Title of Invention	A SMALL - SCALE, SOLAR ENERGY SYSTEM
Abstract	A high-efficiency, small-scale, combined heat and power, concentrating solar energy system, designed specifically for residential and other relatively low-power applications, rendering it cost-effective and economically viable. Two-axis tracking of a dish-like reflector of between 1 and 2 meters in aperture ensures very high concentrating ratios of between 200 and 800 suns or even higher. In consequence very high coolant outlet temperatures, of 120 - 180 0C may be reached at the outlet of the collector coolant, which may be oil, gas, or pressurized water. The high coolant temperatures are advantageous because they may be used for air-conditioning. The high concentration is advantageous because the efficiency of the photovoltaic cells is improved with higher concentration. The overall efficiency is greater than 60 %. Additionally, a simple but accurate drive, designed as a radio-dial drive, with substantially zero backlash, and substantially zero drift, is provided for driving the concentrating solar energy system. Preferably, two radio-dial drives are employed and tracking is performed along two axes, of an azimuth-elevation mount, a polar mount, or a cross mount.

Title of Invention

A SMALL - SCALE, SOLAR ENERGY SYSTEM

Abstract

A high-efficiency, small-scale, combined heat and power, concentrating solar energy system, designed specifically for residential and other relatively low-power applications, rendering it cost-effective and economically viable. Two-axis tracking of a dish-like reflector of between 1 and 2 meters in aperture ensures very high concentrating ratios of between 200 and 800 suns or even higher. In consequence very high coolant outlet temperatures, of 120 - 180 0C may be reached at the outlet of the collector coolant, which may be oil, gas, or pressurized water. The high coolant temperatures are advantageous because they may be used for air-conditioning. The high concentration is advantageous because the efficiency of the photovoltaic cells is improved with higher concentration. The overall efficiency is greater than 60 %. Additionally, a simple but accurate drive, designed as a radio-dial drive, with substantially zero backlash, and substantially zero drift, is provided for driving the concentrating solar energy system. Preferably, two radio-dial drives are employed and tracking is performed along two axes, of an azimuth-elevation mount, a polar mount, or a cross mount.

Full Text	SMALL-SCALE, CONCENTRATING, SOLAR CHP SYSTEM FIELD AND BACKGROUND OF THE INVENTION The present invention relates to high-efficiency, small-scale, combined heat and power (CHP), concentrating solar energy systems, and to a radio-dial drive, for celestial tracking mechanisms, which may be used with the concentrating solar energy systems. Solar photovoltaic collectors are usually of the flat plate type, consisting of a large area of stationary photovoltaic cells that receive natural sunlight, but do not follow the apparent motion of the sun. As yet, power generation by these photovoltaic collectors is not economic, when compared with conventional power sources of fossil fuels. One approach to reducing the cost of power generation by solar photovoltaic collectors is to concentrate the sunlight by optical means, such as lenses and (or) mirrors, thus reducing the actual area of the photovoltaic cells, per kW. Current cells can be activated by solar radiation, which is concentrated by a factor of up to 1,000; therefore the required photovoltaic cell area per kW is 1,000 times less. The resultant power system may be more cost-effective, even when taking into account the more expensive photovoltaic cells for the concentrated radiation and the additional components of the concentrating system, such as, the focusing optics, the mechanical support structure, the tracking mechanism, and the computer control for the tracking. Large concentrating solar power systems, operating with photovoltaic cells, have been proposed and built These may include a single, large concentrator, or a cluster of large concentrators. Yet, to be economically viable, a collector area of about 100 to 200 square meters is required, for each concentrator, so as to spread the cost of the additional components of the concentrating system, per kW. These large concentrating solar power systems are suitable for remote areas, which have no access to the grid. Nonetheless, employing large concentrating solar power systems suffers from a number of drawbacks. 1. Although in general, a larger system tends to be more economical than a smaller system, there are disadvantages to a larger system, as well. Wind resistance is higher, creating high forces on the collector, and these may lead and a simple circuitry, that guarantees easy maintenance and operational procedures, making it suitable for domestic applications. The tracker has a shaft encoder, a 50 W motor developing 20 N-m and is provided with a brake, to produce a torque of up to 500 N-m, when the motor is off, together with an electronic control circuit The system has been tested in conjunction with a domestic concentrator-type solar water heater, but it is believed that maximum benefit would be realized when used as a hybrid system, incorporating photovoltaic and hot water units. However, the system of Ali, et al. has digital tracking, with a resolution of about 0.72 degrees, relies on polished aluminum troughs, as linear concentrators, and uses a single-axis tracking mechanism, so that overall, it achieves a concentrating factor of only about 10. Additionally, the system of Ali, et al. uses both photovoltaic cells and hot water units. In practice, the hot water units are not necessary, since waste heat from the photovoltaic converter can be used for producing hot water. Additionally, Komp, R. J. in "Field experience and performance evaluation of a novel photovoltaic thermal hybrid solar energy collector," EDB, 86-15, 86:116025, 8606508853, NDN-68-0430-1210-7, 1985, CONF-850604, SESCI, Ottawa, Ontario, Canada, describes a new design of a hybrid solar module, capable of furnishing 150 watts (AMI peak power) of electrical power and 1600 watts of thermal energy in the form of hot water. The module incorporates photovoltaic ceils, encapsulated in silicone mounted on the front surface of extruded aluminum fins. Copper tubes forced into the backs of the fins carry the cooling fluid (usually water) to remove the heat while curved aluminum reflectors concentrate light onto the silicon solar cells. The linear curved concentrators (similar to those developed by Winston) require no tracking or seasonal adjustment at the low concentration ratio of 2.1 to 1. The module is intended for residences or small businesses that do not have ready access to conventional utilities. It is essentially a single-size unit and may be installed in a similar manner as a conventional solar heater, with a portion of the solar cell array dedicated to powering and controlling the circulating pump and, if necessary, a valve for a hot water system. The photovoltaic array is split into two separate sections that can be wired in parallel for 12V or in series for 24V systems. Yet, the system of Komp relies on linear concentrators, does not use tracking, and achieves a concentration ratio of only about 2.1 to 1. solar cells were single crystal silicon, designed to match the physical and spectral parameters of the collector. The power conditioning system was utility interactive to provide not only for backup power, but for a power exchange between the solar energy system and the local utility. Process control included data acquisition on all system components and building demands, as well as required control of all components. Thermal energy from the solar cell coolant was provided to the college for winter heating and year-round domestic hot water. The energy system was expected to be operational in the winter of 1979, with connection to the college facilities in the summer of 1980. However, again the system of Henry, et al. is relatively large, single-axis tracking system, adapted for producing 320 kW, and achieving a concentration factor of only about 42. Yet there is still a widely recognized need for, and it would be highly advantageous to have, relatively small cost-effective solar power systems, which have a low production rate threshold for competitive mass production, can be installed close to the consumers of energy, and provide means to use the generated heat as well as the electricity. SUMMARY OF THE INVENTION The object of the present invention relates to providing a high-efficiency Combined Heat and Power (CHP) solar energy system, sufficiently compact to be installed at the point of consumption, with minimal investment in infrastructure, and amenable to mass production, leading to low production cost even with a relatively small market volume, so that overall, the cost of the energy which is consumed is competitive with conventional power generation from fossil fuels. The present invention successfully addresses the shortcomings of the presently known configurations by providing a high-efficiency, small-scale, combined heat and power (CHP), concentrating solar energy system, designed specifically for residential and other relatively low-power applications, rendering it cost-effective and economically viable. Two-axis tracking of a dish-like reflector of between 1 and 2 meters in aperture ensures very high concentrating ratios of between 200 and 800 suns or even higher, if cells suitable for operation at higher concentration are available. In consequence very high coolant outlet temperatures, of 120 - 180 °C may be reached at FIGs. 2A - 2B schematically illustrate first and second views of a radio-dial drive, in accordance with the present invention; FIG. 3 schematically illustrates a cross-sectional view of a radio-dial drive, associated with a timing belt, in accordance with another embodiment of the present invention; FIGs. 4A — 4B schematically illustrate first and second views of a concentrating solar collector, operable with two-axis tracking, each having a radio-dial drive, in accordance with the present invention; FIGs. 5 schematically illustrates a concentrating solar collector, operable with two-axis tracking of a polar mount, each axis having a radio-dial drive, in accordance with another embodiment of the present invention; FIG. 6 schematically illustrates a schematic CHP circuit, in accordance with the present invention; FIG. 7 schematically illustrates a single-solar-collector CHP circuit, in accordance with the present invention; FIG. 8 schematically illustrates a CHP circuit for a cluster of solar collectors, in accordance with the present invention; and FIG. 9 schematically illustrates the cluster arrangement of FIG. 8, in accordance with the present invention. DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is a high-efficiency, small-scale, combined heat and power, concentrating solar energy system, designed specifically for residential and other relatively low-power applications, rendering it cost-effective and economically viable. Two-axis tracking of a dish-like reflector of between 1 and 2 meters in aperture ensures very high concentrating ratios of between 200 and 800 suns or even higher. In consequence very high coolant outlet temperatures, of 120 -180 °C may be reached at the outlet of the collector coolant, which may be oil, gas, or pressurized water. The high coolant temperatures are advantageous because they may be used for air-conditioning. The high concentration is advantageous because the efficiency of the photovoltaic cells is improved with higher concentration. The overall efficiency is greater than 60 %. Additionally, a simple but accurate drive, designed as a radio-dial drive, with substantially zero backlash, and substantially zero drift, is provided for solar incident flux, as a function of geographic location, date, and hour. Additionally or alternatively, a closed-loop operation, based on measured solar incident flux may be employed. Azimuth-elevation mount 100A is often used for heliostats and solar concentrators. Its advantage is that the mechanics are the same for all locations, so no physical adjustments need to be made, specifically for each geographic location. Its main disadvantage is that both axes are constantly moving, at variable speeds, so that together they correct for three effects, the geographic, the seasonal, and the hourly changes of the direction that will maximize the solar incident flux. Azimuth-elevation mount 100A is considered an Euler system, and has a singularity when the sun is in the zenith, which may take place at latitudes of ± 23.5 °. Thus, it may be inappropriate near the equator. Figure IB schematically illustrates a cross mount 100B, as known. Cross mount 100B includes a vertical rod 119 which is fixed to ground 110. A horizontal rod 107, mounted on vertical rod 119 defines an axis of rotation 113 A, as shown by an arrow 115. A rod 109, mounted on rod 107 defines an axis of rotation 113B, as shown by an arrow 117. Reflector 112 is mounted on rod 109, so as to rotate with rods 107 and rod 109, changing its azimuth and elevation. Cross mount 100B has singularity near the polar region. Figure 1C schematically illustrates a polar mount 120, as known. In essence, polar mount 120 compensates for daily and seasonal variations of direction that will optimize the solar incident flux, while the geographic affect is built into the mount. Polar mount 120 includes poles 126 and 127, both having proximal and distal ends 128 and 130, with respect to ground 110, wherein proximal ends 128 are fixed to ground 110. A rod 122, extending north to south between distal ends 130 of poles 126 and 127, makes an angle p with the face of the earth (ground 110), angle p being substantially equal to the geographical latitude. Rod 122 defines a length axis 121 A, which is parallel to the axis of rotation of the earth, i.e., the line connecting the Earth's poles. a spring 52, mounted on drum external surface 41, having a spring axis 59, orthogonal to drum axis of rotation 43; and an anchor 54, mounted on drum external surface 41. Additionally, radio-dial drive 20 includes a cylindrical capstan 50, mounted on support structure 45, adjacent to drum 42. Capstan 50 defines a capstan axis of rotation 47, parallel to drum axis of rotation 43, and a capstan external surface 49, along its circumference. A cable 56, having first and second ends 51 and 53, respectively, is tightly wound around drum 42 in a first direction, and around capstan 50 in a second direction, wherein first end 51 is fixedly attached to spring 52 and second end 53 is fixed against drum external surface 41 by anchor 54. Additionally, spring 52 is held in tension with a force which is just greater than the required force for turning drum 42 and shaft 48, so that turning the capstan 50 in a first direction will turn drum 42 in a second direction, with substantially zero backlash and substantially zero drift Substantially zero backlash relates to a near absence of slack in cable 56, as capstan 50 changes a direction of rotation, for example, from clockwise to counterclockwise, or vice versa. Substantially zero drift relates to a near absence of slippage in cable 56 against drum external surface 41, and against the capstan surface 49. The travel of drum 42 is described by an arrow 55 and is preferably ± 90°, for an arc of 180°. It will be appreciated that other values which may be smaller or larger are also possible. Capstan 50, which is considerably smaller than drum 42, makes several revolutions, as illustrated by an arrow 57, as drum 42 completes an arc of 180°. The diametric ratios of drum 42 and capstan 50 may be, for example, 1 to 6.5. It will be appreciated that other values, which may be smaller or larger, are also possible. A computer-controlled motor 40, or another computer controlled drive system provides the tuning or tracking motion to capstan 50, based on an expression for the direction that will maximize the solar incident flux, as functions of date, time, and geographic location. Motor 40 may be a stepped motor or a DC motor. Additionally, a close-loop system, described hereinbelow, in conjunction with Figures 4A - 4B and 5 may be used. substantially focus the incident radiation to a focal point, may be used. Alternatively still, concentrator 12 may be trough-like. Additionally, drive unit 14 includes at least a first drive module 20A (Figure 4A and 4B), for solar tracking along a first axis, and preferably also, a second drive module 20B (Figure 4B), for solar tracking along a second axis, orthogonal to the first axis. Drive unit 14 further includes a counterweight 26. Concentrating dish 12 preferably includes a rim 30. A reflector 32 forms the surface of concentrating dish 12, which faces the sun. The angle between rim 30, a focal point F of dish 12, and a center P is ex, which may be used as a measure of the concentrating power of dish 12. A power conversion unit 34, substantially at the focal point of concentrating dish 12, may be photovoltaic cells, adapted for concentrated radiation. Alternatively, a thermal engine or another known method of producing electric power may be used. Drive unit 14 is mounted on pedestal 16, structured so that it can cany the loads of dish 12 and the drive unit 14, while allowing full motion of the drive modules 20A and 20B. Dish 12 is attached to module 20B through a dish support 28. Preferably, Collector 10 includes two degrees of motion. When constructed as an azimuth-elevation mount or as a cross mount, these two motions simultaneously track the sun with respect to geographic, seasonal and daily variations. Referring further to the drawings, Figure 5 schematically illustrates collector 10, mounted on a polar mount 120, and preferably incorporating two radio-dial drives, in accordance with the present invention. Accordingly, Collector 10 includes polar mount 120, having two poles 126 and two poles 127 (of which only one is seen in the pictorial representation), all having proximal ends 128, with respect to ground 110, and are fixed to ground 110 at their proximal ends 128. Poles 126 and 127 are connected by a rod 122, at their distal ends 130. Rod 122 makes angle P with the earth surface. Polar mount 120 further includes daily axis of rotation 121 A, for following the daily motion of the sun, from east to west Additionally, polar mount 120 includes seasonal axis of rotation 121B, for correcting the daily solar tracking for the seasonal changes, Le., the tilt of the sun's somewhat, so that reflector 12 may be actually pointing off from the orientation specified by the expression for the direction that will maximize the solar incident flux. The closed loop operation may then correct for the inaccuracy, by reporting to the computer that the solar incident flux is less than that which can be realized, leading the computer to specify a correction to the motion. It is in this regard that the substantially zero backlash of radio-dial mechanism 20 is important Backlash may occur with a change in the direction of motion, and generally, the basic tracking motion is unidirectional (except for seasonal changes in direction, twice a year, in the spring and fall). Thus the basic motion should not encounter backlash. However, the correction, as specified by the closed-loop system, may be in any of the two directions of motion of each axis, and must be highly accurate. Therefore, radio-dial mechanism 20, with its substantially zero backlash and substantially zero drift is particularly suitable for the correction motion, as specified by the closed loop system. Preferably, the closed-loop system is additional to the system operated by the computer-calculated expression for the direction that will maximize the solar incident flux. Alternatively, only a closed loop system, or only a computer-calculated expression for the direction that will maximize the solar incident flux may be employed. Another aspect of the present invention relates to employing a Combined Heat and Power (CHP) circuit, for increased cost-effectiveness of the small-scale solar power system. Thus, Figure 6 schematically illustrates a CHP circuit 150, in accordance with the present invention. Accordingly, CHP circuit 150 operates with a preferably closed-loop primary coolant circulating system 155, driven by a pump 158. The coolant may be water, oil, or another fluid, for example, a gas. Thus, CHP circuit 150 includes a power generation module 152, which includes at least one Collector 10 (Figures 4A - 4B and 5), having at least one power conversion unit 34, for example, a thermal engine or concentrated photovoltaic cells. A control system 153, preferably supported by a closed loop system 157 controls the tracking of at least one collector 10. backup heater 189, as known. Hot water from hot-water tank 188 may supply general hot water needs 190 of residential unit 180, as well as space heating 192, for example, through radiators, or under-floor water pipes. As has been illustrated in conjunction with Figure 6, the coolant of the primary loop of CHP circuit 150 flows to excess heat exchanger 156, where excess heat is removed. Pump 158 ensures circulation-Referring further to the drawings, Figure 8 schematically illustrates a CHP circuit 200 for a cluster of solar collectors, for residential or small commercial unit 210, in accordance with the present invention. The advantage of using a cluster of concentrating solar collectors 10, is that power collection is greatly increased, while the number of auxiliary components, such as secondary heat exchanger 156 and pump 158, and control unit 153 remains the same, so as to further improve the cost effectiveness and economic viability of the system. Additionally, maintenance could be simplified for a single component replacing many identical smaller components. The operation of cluster 200 is similar to the operation of system 170 (Figure 7), with the following exceptions: 1. Electrical interfaces 172 of each concentrating solar collectors 10 may be connected in series or in parallel, or in a combination of series and parallel connections, providing flexibility in power and voltage input to a residential unit 210. 2. At the same time, the control of all concentrating solar collectors 10 may be performed by control unit 153 (Figure 6), since the tracking data for all concentrating solar collectors 10 is the same. 3. The hot water interfaces from all collectors may be connected to a single secondary closed loop system. The connection is in parallel. The pipe leads to a central primary heat exchanger in the hot water tank, a central secondary heat exchanger, and a single pump. Since the plurality of collectors are connected in parallel, each collector receives the same low inlet temperature and the total flow rate in the pump and in the main pipe is the sum of flow rates in all the collectors. 4. Although the number of collectors connected in parallel to a single pump and heat exchanger is not limited in principle, it may be reasonable to divide a large field into several independent sections, to limit the cost of the tubes. It will be appreciated that in general, the cluster arrangement may be either closed loop or open loop. In general, a single control unit 153 may be used will all the collectors, but each may require its individual closed loop system 157. The following are general design parameters for the present invention. A typical size for a solar energy system of the present invention, as illustrated in Figures 4A — 4B and 5 may be a concentrator diameter of between about 0.5 meters and about 2 meter, and preferably, about 1 meter, capable of producing about 150 Watts of electricity, together with about 350 Watts of heat Thus, the structural support of the collector needs be relatively light, since the wind loads are relatively small. The tracking mechanism is relatively simple and can be manufactured relatively inexpensively. The cost of manufacturing such a system is estimated at about $2 per Watt at peak power. The required investment for a suitable production line is estimated at about $5M. Given an annual production rate of 5 Megawatts and an interest rate of 5%, the surcharge for repaying the initial investment is estimated at only about $0.13 per Watt at peak power. Therefore the required market volume for the proposed small-scale system is smaller by an order of magnitude than that of current, large systems, and the required investment risk is correspondingly smaller. The small-scale solar energy systems can be installed at the point of consumption, such as on rooftops of domestic and public buildings, in urban environment, supplying them with both power and hot water, for domestic water and space heating. With a Combined Heat and Power (CHP) system an overall efficiency of the system may be competitive with fossil fuel power plants. Cost estimates are based on an annual production rate of 250,000 m , which corresponds to 1.2 million and 260,000 units per year for concentrators of between about 0.5 m and LI m in diameter. The production period, i.e., the period during which the system may be produced and sold, and the initial investment can be amortized and recovered is about 10 years. Design parameters, considerations, and requirements for Collector 10 of Figures 4A - 4B and 5 are discussed below: 1. Reflector 12 may be designed as a concave parabolic dish with a projected (aperture) diameter of about between 0.5 and 2 meters, and preferably about 1.1 meter in diameter. It will be appreciated that other diameters are also possible. comparison, for small-scale systems, the problem of wind resistance is far less acute. 2. With an efficiency of power conversion to photovoltaic cells in the range of 10 to about 37 percent, most of the solar energy is discharged as heat Yet in a centralized, remote area there is little opportunity to utilize that heat, for example, in a Combined Power and Heat (CPH) system, thus the heat is wasted. By comparison, small-scale systems, built on rooftops, may be designed as Combined Power and Heat (CPH), with a considerably increase in overall efficiency. 3. The large concentrating solar power systems are installed away from the consumer. Therefore additional costs due to power distribution and to transmission losses are incurred, reducing the amount of available electricity by 10-20%, and raising the cost of the electric power thus produced by factors of between 2 and 3. Yet with large concentrating systems of photovoltaic cells, transmission and distribution costs cannot be avoided since the systems are too large to be installed at the points of consumption. By comparison, for small-scale systems, built on rooftops, at the point of consumption, there are not distribution costs and no transmission losses to speak of. 4. The initial investment for large concentrating solar power systems is very high, making decisions in this regard difficult, bureaucratic, and risky. By comparison, for small-scale systems, the decision is of the individual homeowner, and governmental incentives may be used to make it less risky. 5. Furthermore, competitive costs may be realized for large concentrating solar power systems if a significant number of them, equivalent for example, to at least 50 megawatt per year, is manufactured. Yet such a market volume is difficult to guarantee; therefore, the investment arid the risk associated with the development of such large systems are very high. By comparison, for small-scale systems, given governmental incentives, such a market may be realized. 6. Large concentrating solar power systems must be installed by trained personnel with specialized equipment and facilities, requiring special contractors, and special licenses, which increase their costs. By comparison, embodiments and aspects of the present invention as delineated hereinabove and as claimed in the claims section below finds experimental support in the following examples. It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment Conversely, various features of the invention, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable subcombination. Although the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the spirit and broad scope of the appended claims. All publications, patents and patent applications mentioned in this specification are herein incorporated in their entirety by reference into the specification, to the same extent as if each individual publication, .patent or patent application was specifically and individually indicated to be incorporated herein by reference. In addition, citation or identification of any reference in this application shall not be construed as an admission that such reference is available as prior art to the present invention. What is claimed: 1. A high-efficiency, small-scale, combined heat and power, concentrating solar energy system comprising: at least one collector, which comprises: a concentrator, having an aperture of between about 0.5 m about 2 meters, adapted for focusing incident solar radiation to a focal point; at least one drive on which said concentrator is mounted, said drive being adapted for tracking a direction that will maximize the solar incident flux, at least along one axis; a control unit, in communication with said drive, for controlling said drive, based on an expression of said direction, as functions of time of day, season, and geographic latitude; and a power conversion unit, substantially at said focal point; a power supply system, which receives electrical power from said power conversion unit; a heat supply system, which receives heat from a cooling system of said power conversion unit, wherein a combined heat and power efficiency of said high-efficiency, small-scale, combined heat and power, concentrating solar energy system is greater than 60% overall efficiency. 2. The high-efficiency, small-scale, combined heat and power, concentrating solar energy system of claim 1, wherein a combined heat and power efficiency of said high-efficiency, small-scale, combined heat and power, concentrating solar energy system is greater than 65% overall efficiency. 3. The high-efficiency, small-scale, combined heat and power, concentrating solar energy system of claim 1, wherein a combined heat and power efficiency of said high-efficiency, small-scale, combined heat and power, concentrating solar energy system is greater than 70% overall efficiency. f 4. The high-efficiency, small-scale, combined heat and power, concentrating solar energy system of claim 1, wherein a combined heat and power efficiency of said high-efficiency, small-scale, combined heat and power, concentrating solar energy system is greater than 75% overall efficiency. 5. The high-efficiency, small-scale, combined heat and power, concentrating solar energy system of claim 1, wherein said at least one collector comprises a plurality of collectors, arranged as a cluster, each including said heat supply system, and further wherein said heat supply systems from each collector are arranged in parallel, so as to have the same inlet and outlet coolant conditions. 6. The high-efficiency, small-scale, combined heat and power, concentrating solar energy system of claim 1, wherein said heat supply system operates an air conditioning system. 7. The high-efficiency, small-scale, combined heat and power, concentrating solar energy system of claim 1, wherein said collector includes a closed loop system. 8. The high-efficiency, small-scale, combined heat and power, concentrating solar energy system of claim 1, wherein said at least one drive includes at least two drives, adapted for tracking a direction that will maximize the solar incident flux, at least along two axes. 9. The high-efficiency, small-scale, combined heat and power, concentrating solar energy system of claim 1, wherein said at least one drive is a radio dial drive. 10. A celestial tracking system, comprising: a first main support; a first tracking unit, mounted on said first main support, which comprises: a first radio-dial drive for celestial tracking mechanism, comprising: a first support structure; a first cylindrical drum, mounted on said support structure, said drum defining a drum axis of rotation and a drum external surface, along its circumference, and said drum having: a first central shaft, parallel to said drum axis of rotation, and fixedly attached to said drum, so as to rotate with said drum, in said axis of rotation; a first spring, mounted on said drum external surface, having a spring axis orthogonal to said drum axis of rotation; and a first anchor, mounted on said drum external surface; a first cylindrical capstan, mounted on said support structure, adjacent to said drum, and defining a capstan axis of rotation, parallel to said drum axis of rotation and a capstan external surface, along its circumference; a first cable, having first and second ends, said cable being tightly wound around said drum in a first direction, and around said capstan in a second direction, wherein said first end is fixedly attached to said anchor and said second end is fixedly attached to said spring, and wherein said spring is held in tension with a force which is greater than the required force for turning said drum, so that turning the capstan in a first direction will turn the drum in a second direction, with substantially zero backlash and substantially zero drift; and a first motor, mounted on said main support, for providing a tracking motion. 11. The celestial tracking system of claim 10, wherein said first motor is selected from the group of a step motor and a DC motor. 12. The celestial tracking system of claim 10, and further including a timing belt arranged between said first motor and said first cylindrical capstan. 13. The celestial tracking system of claim 10, wherein said first tracking unit is arranged on a first axis of rotation, and further including a second tracking unit, arranged on a second axis of rotation, and comprising: a second radio-dial drive for celestial tracking mechanism, comprising: a second support structure; a second cylindrical drum, mounted on said second support structure, said second drum defining a second drum axis of rotation and a second drum external surface, along its circumference, and said second drum having: a second central shaft, parallel to said second drum axis of rotation, and fixedly attached to said second drum, so as to rotate with said second drum, in said second axis of rotation; a second spring, mounted on said second drum external surface, having a second spring axis, orthogonal to said second drum axis of rotation; and a second anchor, mounted on said second drum external surface; a second cylindrical capstan, mounted on said second support structure, adjacent to said second drum, and defining a second capstan axis of rotation, parallel to said second drum axis of rotation and a second capstan external surface, along its circumference; a second cable, having first and second ends, said second cable being tightly wound around said second drum in a first direction, and around said capstan in a second direction, wherein said first end is fixedly attached to said second anchor and said second end is fixedly attached to said second spring, and wherein said second spring is held in tension with a force which is greater than the required force for turning said second drum, so that turning said second capstan in a first direction will turn the drum in a second direction, with substantially zero backlash and substantially zero drift; and a second motor, mounted on said second main support, for providing a second tracking motion. 14. The celestial tracking system of claim 10, and further including a concentrating solar energy system, comprising: a collector; and a power conversion unit. 15. The celestial tracking system of claim 10, and further including a control unit, in communication with said motor, for controlling said tracking motion, using an expression for the direction that will maximize the solar incident flux. 16. A solar energy system, comprising: a first main support of said solar energy system; a first tracking unit, mounted on said first main support, which comprises: a first radio-dial drive for celestial tracking mechanism, comprising: a first support structure; a first cylindrical drum, mounted on said support structure, said drum defining a drum axis of rotation and a drum external surface, along its circumference, and said drum having: a first central shaft, parallel to said drum axis of rotation, and fixedly attached to said drum, so as to rotate with said drum, in said axis of rotation; a first spring, mounted on said drum external surface, having a spring axis orthogonal to said drum axis of rotation; and a first anchor, mounted on said drum external surface; a first cylindrical capstan, mounted on said support structure, adjacent to said drum, and defining a capstan axis of rotation, parallel to said drum axis of rotation and a capstan external surface, along its circumference; a first cable, having first and second ends, said cable being tightly wound around said drum in a first direction, and around said capstan in a second direction, wherein said first end is fixedly attached to said anchor and said second end is fixedly attached to said spring, and wherein said spring is held in tension with a force which is greater than the required force for turning said drum, so that turning the capstan in a first direction will turn the drum in a second direction, with substantially zero backlash and substantially zero drift; a first motor, mounted on said main support, for providing a tracking motion; a collector; and a power conversion unit. 17. A central plant, comprising: a plurality of units, each of said units including: a first main support; a first tracking unit, mounted on said first main support, which comprises: a first radio-dial drive for celestial tracking mechanism, comprising: a first support structure; a first cylindrical drum, mounted on said support structure, said drum defining a drum axis of rotation and a drum external surface, along its circumference, and said drum having: a first central shaft, parallel to said drum axis of rotation, and fixedly attached to said drum, so as to rotate with said drum, in said axis of rotation; a first spring, mounted on said drum external surface, having a spring axis orthogonal to said drum axis of rotation; and a first anchor, mounted on said drum external surface; a first cylindrical capstan, mounted on said support structure, adjacent to said drum, and defining a capstan axis of rotation, parallel to said drum axis of rotation and a capstan external surface, along its circumference; a first cable, having first and second ends, said cable being tightly wound around said drum in a first direction, and around said capstan in a second direction, wherein said first end is fixedly attached to said anchor and said second end is fixedly attached to said spring, and wherein said spring is held in tension with a force which is greater than the required force for turning said drum, so that turning the capstan in a first direction will turn the drum in a second direction, with substantially zero backlash and substantially zero drift; a first motor, mounted on said main support, for providing a tracking motion; a first transmission system, in communication both with said motor and with said cylindrical capstan, for transmitting said tracking motion from said motor to said capstan; a collector; and a power conversion unit. 18. The central plant of claim 17, wherein said first motor is selected from the group of a step motor and a DC motor. 19. The central plant of claim 17, wherein said first tracking unit is arranged on a first axis of rotation, and further including a second tracking unit, arranged on a second axis of rotation, and comprising: a second radio-dial drive for celestial tracking mechanism, comprising: a second support structure; a second cylindrical drum, mounted on said second support structure, said second drum defining a second drum axis of rotation and a second drum external surface, along its circumference, and said second drum having: a second central shaft, parallel to said second drum axis of rotation, and fixedly attached to said second drum, so as to rotate with said second drum, in said second axis of rotation; a second spring, mounted on said second drum external surface, having a second spring axis, orthogonal to said second drum axis of rotation; and a second anchor, mounted on said second drum external surface; a second cylindrical capstan, mounted on said second support structure, adjacent to said second drum, and defining a second capstan axis of rotation, parallel to said second drum axis of rotation and a second capstan external surface, along its circumference; a second cable, having first and second ends, said second cable being tightly wound around said second drum in a first direction, and around said capstan in a second direction, wherein said first end is fixedly attached to said second anchor and said second end is fixedly attached to said second spring, and wherein said second spring is held in tension with a force which is greater than the required force for turning said second drum, so that turning said second capstan in a first direction will turn the drum in a second direction, with substantially zero backlash and substantially zero drift; a second motor, mounted on said second main support, for providing a second tracking motion; and a second transmission system, in communication both with said second motor and with said second cylindrical capstan, for transmitting said second tracking motion from said second motor to said second capstan. 20. The central plant of claim 17, wherein said collector has a real focal point and an aperture of between about 0.5 meter and about 2 meters. 21. The central plant of claim 17, wherein said power conversion unit is selected from the group consisting of a thermal generator, concentrated photovoltaic cells, and flat photovoltaic cells. 22. The central plant of claim 17, arranged as a Combined Heat and Power (CHP) system. 23. The central plant of claim 17, and further including differential means for measuring the solar incident flux, for providing a closed-loop control of said tracking motion. 24. The central plant of claim 17, and further including a control unit, in communication with said motor, for controlling said tracking motion, using an expression for the direction that will maximize the solar incident flux. 25. A heliostat, comprising: a first main support for said heliostat; a first tracking unit, mounted on said first main support, which comprises: a first radio-dial drive for celestial tracking mechanism, comprising: a first support structure; a first cylindrical drum, mounted on said support structure, said drum defining a drum axis of rotation and a drum external surface, along its circumference, and said drum having: a first central shaft, parallel to said drum axis of rotation, and fixedly attached to said drum, so as to rotate with said drum, in said axis of rotation; a first spring, mounted on said drum external surface, having a spring axis orthogonal to said drum axis of rotation; and a first anchor, mounted on said drum external surface; a first cylindrical capstan, mounted on said support structure, adjacent to said drum, and defining a capstan axis of rotation, parallel to said drum axis of rotation and a capstan external surface, along its circumference; a first cable, having first and second ends, said cable being tightly wound around said drum in a first direction, and around said capstan in a second direction, wherein said first end is fixedly attached to said anchor and said second end is fixedly attached to said spring, and wherein said spring is held in tension with a force which is greater than the required force for turning said drum, so that turning the capstan in a first direction will turn the drum in a second direction, with substantially zero backlash and substantially zero drift; a first motor, mounted on said main support, for providing a tracking motion; a first transmission system, in communication both with said motor and with said cylindrical capstan, for transmitting said tracking motion from said motor to said capstan; and a collector. 26. The heliostat of claim 25, wherein said first motor is selected from the group of a step motor and a DC motor. 27. The heliostat of claim 25, wherein said first tracking unit is arranged on a first axis of rotation, and further including a second tracking unit, arranged on a second axis of rotation, and comprising: a second radio-dial drive for celestial tracking mechanism, comprising: a second support structure; a second cylindrical drum, mounted on said second support structure, said second drum defining a second drum axis of rotation and a second drum external surface, along its circumference, and said second drum having: a second central shaft, parallel to said second drum axis of rotation, and fixedly attached to said second drum, so as to rotate with said second drum, in said second axis of rotation; a second spring, mounted on said second drum external surface, having a second spring axis, orthogonal to said second drum axis of rotation; and a second anchor, mounted on said second drum external surface; a second cylindrical capstan, mounted on said second support structure, adjacent to said second drum, and defining a second capstan axis of rotation, parallel to said second drum axis of rotation and a second capstan external surface, along its circumference; a second cable, having first and second ends, said second cable being tightly wound around said second drum in a first direction, and around said capstan in a second direction, wherein said first end is fixedly attached to said second anchor and said second end is fixedly attached to said second spring, and wherein said second spring is held in tension with a force which is greater than the required force for turning said second drum, so that turning said second capstan in a first direction will turn the drum in a second direction, with substantially zero backlash and substantially zero drift; a second motor, mounted on said second main support, for providing a second tracking motion; and a second transmission system, in communication both with said second motor and with said second cylindrical capstan, for transmitting said second tracking motion from said second motor to said second capstan. 28. The heliostat of claim 25, wherein said collector has a real focal point and an aperture of between about 0.5 meter and about 2 meters. 29. The heliostat of claim 25, and further including a control unit, in communication with said motor, for controlling said tracking motion, using an expression for the direction that will maximize the solar incident flux. 30. A central plant, comprising: a plurality of heliostats, each of said heliostats including: a first main support; a first tracking unit, mounted on said first main support, which comprises: a first radio-dial drive for celestial tracking mechanism, comprising: a first support structure; a first cylindrical drum, mounted on said support structure, said drum defining a drum axis of rotation and a drum external surface, along its circumference, and said drum having: a first central shaft, parallel to said drum axis of rotation, and fixedly attached to said drum, so as to rotate with said drum, in said axis of rotation; a first spring, mounted on said drum external surface, having a spring axis orthogonal to said drum axis of rotation; and a first anchor, mounted on said drum external surface; a first cylindrical capstan, mounted on said support structure, adjacent to said drum, and defining a capstan axis of rotation, parallel to said drum axis of rotation and a capstan external surface, along its circumference; a first cable, having first and second ends, said cable being tightly wound around said drum in a first direction, and around said capstan in a second direction, wherein said first end is fixedly attached to said anchor and said second end is fixedly attached to said spring, and wherein said spring is held in tension with a force which is greater than the required force for turning said drum, so that turning the capstan in a first direction will turn the drum in a second direction, with substantially zero backlash and substantially zero drift; a first motor, mounted on said main support, for providing a tracking motion; a first transmission system, in communication both with said motor and with said cylindrical capstan, for transmitting said tracking motion from said motor to said capstan; a collector, said central plant further including a power conversion unit. 31. The central plant of claim 30, wherein said first motor is selected from the group of a step motor and a DC motor. 32. The central plant of claim 30, wherein said first tracking unit is arranged on a first axis of rotation, and further including a second tracking unit, arranged on a second axis of rotation, and comprising: a second radio-dial drive for celestial tracking mechanism, comprising: a second support structure; a second cylindrical drum, mounted on said second support structure, said second drum defining a second drum axis of rotation and a second drum external surface, along its circumference, and said second drum having: a second central shaft, parallel to said second drum axis of rotation, and fixedly attached to said second drum, so as to rotate with said second drum, in said second axis of rotation; a second spring, mounted on saia secona arum external surface, having a second spring axis, orthogonal to said second drum axis of rotation; and a second anchor, mounted on said second drum external surface; a second cylindrical capstan, mounted on said second support structure, adjacent to said second drum, and defining a second capstan axis of rotation, parallel to said second drum axis of rotation and a second capstan external surface, along its circumference; a second cable, having first and second ends, said second cable being tightly wound around said second drum in a first direction, and around said capstan in a second direction, wherein said first end is fixedly attached to said second anchor and said second end is fixedly attached to said second spring, and wherein said second spring is held in tension with a force which is greater than the required force for turning said second drum, so that turning said second capstan in a first direction will turn the drum in a second direction, with substantially zero backlash and substantially zero drift; a second motor, mounted on said second main support, for providing a second tracking motion; and a second transmission system, in communication both with said second motor and with said second cylindrical capstan, for transmitting said second tracking motion from said second motor to said second capstan. 33. The central plant of claim 30, wherein said collector has a real focal point and an aperture of between about 0.5 meter and about 2 meters. 34. The central plant of claim 30, wherein said power conversion unit is selected from the group consisting of a thermal generator, concentrated photovoltaic cells, and flat photovoltaic cells. 35. The central plant of claim 30, arranged as a Combined Heat and Power (CHP) system. me central plant of claim 30, and further including differential means for measuring the solar incident flux, for providing a closed-loop control of said tracking motion, 37. The central plant of claim 30, and further including a control unit, in communication with said motor, for controlling said tracking motion, using an expression for the direction that will maximize the solar incident flux.

Full Text

SMALL-SCALE, CONCENTRATING, SOLAR CHP SYSTEM
FIELD AND BACKGROUND OF THE INVENTION
The present invention relates to high-efficiency, small-scale, combined heat and power (CHP), concentrating solar energy systems, and to a radio-dial drive, for celestial tracking mechanisms, which may be used with the concentrating solar energy systems.
Solar photovoltaic collectors are usually of the flat plate type, consisting of a large area of stationary photovoltaic cells that receive natural sunlight, but do not follow the apparent motion of the sun. As yet, power generation by these photovoltaic collectors is not economic, when compared with conventional power sources of fossil fuels.
One approach to reducing the cost of power generation by solar photovoltaic collectors is to concentrate the sunlight by optical means, such as lenses and (or) mirrors, thus reducing the actual area of the photovoltaic cells, per kW. Current cells can be activated by solar radiation, which is concentrated by a factor of up to 1,000; therefore the required photovoltaic cell area per kW is 1,000 times less. The resultant power system may be more cost-effective, even when taking into account the more expensive photovoltaic cells for the concentrated radiation and the additional components of the concentrating system, such as, the focusing optics, the mechanical support structure, the tracking mechanism, and the computer control for the tracking.
Large concentrating solar power systems, operating with photovoltaic cells, have been proposed and built These may include a single, large concentrator, or a cluster of large concentrators. Yet, to be economically viable, a collector area of about 100 to 200 square meters is required, for each concentrator, so as to spread the cost of the additional components of the concentrating system, per kW. These large concentrating solar power systems are suitable for remote areas, which have no access to the grid.
Nonetheless, employing large concentrating solar power systems suffers from a number of drawbacks. 1. Although in general, a larger system tends to be more economical than a
smaller system, there are disadvantages to a larger system, as well. Wind
resistance is higher, creating high forces on the collector, and these may lead

and a simple circuitry, that guarantees easy maintenance and operational procedures, making it suitable for domestic applications. The tracker has a shaft encoder, a 50 W motor developing 20 N-m and is provided with a brake, to produce a torque of up to 500 N-m, when the motor is off, together with an electronic control circuit The system has been tested in conjunction with a domestic concentrator-type solar water heater, but it is believed that maximum benefit would be realized when used as a hybrid system, incorporating photovoltaic and hot water units.
However, the system of Ali, et al. has digital tracking, with a resolution of about 0.72 degrees, relies on polished aluminum troughs, as linear concentrators, and uses a single-axis tracking mechanism, so that overall, it achieves a concentrating factor of only about 10.
Additionally, the system of Ali, et al. uses both photovoltaic cells and hot
water units. In practice, the hot water units are not necessary, since waste heat from
the photovoltaic converter can be used for producing hot water. Additionally,
Komp, R. J. in "Field experience and performance evaluation of a novel photovoltaic
thermal hybrid solar energy collector,"
EDB, 86-15, 86:116025, 8606508853, NDN-68-0430-1210-7, 1985, CONF-850604, SESCI, Ottawa, Ontario, Canada, describes a new design of a hybrid solar module, capable of furnishing 150 watts (AMI peak power) of electrical power and 1600 watts of thermal energy in the form of hot water. The module incorporates photovoltaic ceils, encapsulated in silicone mounted on the front surface of extruded aluminum fins. Copper tubes forced into the backs of the fins carry the cooling fluid (usually water) to remove the heat while curved aluminum reflectors concentrate light onto the silicon solar cells. The linear curved concentrators (similar to those developed by Winston) require no tracking or seasonal adjustment at the low concentration ratio of 2.1 to 1. The module is intended for residences or small businesses that do not have ready access to conventional utilities. It is essentially a single-size unit and may be installed in a similar manner as a conventional solar heater, with a portion of the solar cell array dedicated to powering and controlling the circulating pump and, if necessary, a valve for a hot water system. The photovoltaic array is split into two separate sections that can be wired in parallel for 12V or in series for 24V systems.
Yet, the system of Komp relies on linear concentrators, does not use tracking, and achieves a concentration ratio of only about 2.1 to 1.

solar cells were single crystal silicon, designed to match the physical and spectral parameters of the collector. The power conditioning system was utility interactive to provide not only for backup power, but for a power exchange between the solar energy system and the local utility. Process control included data acquisition on all system components and building demands, as well as required control of all components. Thermal energy from the solar cell coolant was provided to the college for winter heating and year-round domestic hot water. The energy system was expected to be operational in the winter of 1979, with connection to the college facilities in the summer of 1980.
However, again the system of Henry, et al. is relatively large, single-axis tracking system, adapted for producing 320 kW, and achieving a concentration factor of only about 42.
Yet there is still a widely recognized need for, and it would be highly advantageous to have, relatively small cost-effective solar power systems, which have a low production rate threshold for competitive mass production, can be installed close to the consumers of energy, and provide means to use the generated heat as well as the electricity.
SUMMARY OF THE INVENTION
The object of the present invention relates to providing a high-efficiency Combined Heat and Power (CHP) solar energy system, sufficiently compact to be installed at the point of consumption, with minimal investment in infrastructure, and amenable to mass production, leading to low production cost even with a relatively small market volume, so that overall, the cost of the energy which is consumed is competitive with conventional power generation from fossil fuels.
The present invention successfully addresses the shortcomings of the presently known configurations by providing a high-efficiency, small-scale, combined heat and power (CHP), concentrating solar energy system, designed specifically for residential and other relatively low-power applications, rendering it cost-effective and economically viable. Two-axis tracking of a dish-like reflector of between 1 and 2 meters in aperture ensures very high concentrating ratios of between 200 and 800 suns or even higher, if cells suitable for operation at higher concentration are available. In consequence very high coolant outlet temperatures, of 120 - 180 °C may be reached at

FIGs. 2A - 2B schematically illustrate first and second views of a radio-dial drive, in accordance with the present invention;
FIG. 3 schematically illustrates a cross-sectional view of a radio-dial drive, associated with a timing belt, in accordance with another embodiment of the present invention;
FIGs. 4A — 4B schematically illustrate first and second views of a concentrating solar collector, operable with two-axis tracking, each having a radio-dial drive, in accordance with the present invention;
FIGs. 5 schematically illustrates a concentrating solar collector, operable with two-axis tracking of a polar mount, each axis having a radio-dial drive, in accordance with another embodiment of the present invention;
FIG. 6 schematically illustrates a schematic CHP circuit, in accordance with the present invention;
FIG. 7 schematically illustrates a single-solar-collector CHP circuit, in accordance with the present invention;
FIG. 8 schematically illustrates a CHP circuit for a cluster of solar collectors, in accordance with the present invention; and
FIG. 9 schematically illustrates the cluster arrangement of FIG. 8, in accordance with the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention is a high-efficiency, small-scale, combined heat and power, concentrating solar energy system, designed specifically for residential and other relatively low-power applications, rendering it cost-effective and economically viable. Two-axis tracking of a dish-like reflector of between 1 and 2 meters in aperture ensures very high concentrating ratios of between 200 and 800 suns or even higher. In consequence very high coolant outlet temperatures, of 120 -180 °C may be reached at the outlet of the collector coolant, which may be oil, gas, or pressurized water. The high coolant temperatures are advantageous because they may be used for air-conditioning. The high concentration is advantageous because the efficiency of the photovoltaic cells is improved with higher concentration. The overall efficiency is greater than 60 %. Additionally, a simple but accurate drive, designed as a radio-dial drive, with substantially zero backlash, and substantially zero drift, is provided for

solar incident flux, as a function of geographic location, date, and hour. Additionally or alternatively, a closed-loop operation, based on measured solar incident flux may be employed.
Azimuth-elevation mount 100A is often used for heliostats and solar concentrators. Its advantage is that the mechanics are the same for all locations, so no physical adjustments need to be made, specifically for each geographic location. Its main disadvantage is that both axes are constantly moving, at variable speeds, so that together they correct for three effects, the geographic, the seasonal, and the hourly changes of the direction that will maximize the solar incident flux.
Azimuth-elevation mount 100A is considered an Euler system, and has a singularity when the sun is in the zenith, which may take place at latitudes of ± 23.5 °. Thus, it may be inappropriate near the equator.
Figure IB schematically illustrates a cross mount 100B, as known.
Cross mount 100B includes a vertical rod 119 which is fixed to ground 110. A horizontal rod 107, mounted on vertical rod 119 defines an axis of rotation 113 A, as shown by an arrow 115. A rod 109, mounted on rod 107 defines an axis of rotation 113B, as shown by an arrow 117.
Reflector 112 is mounted on rod 109, so as to rotate with rods 107 and rod 109, changing its azimuth and elevation.
Cross mount 100B has singularity near the polar region.
Figure 1C schematically illustrates a polar mount 120, as known.
In essence, polar mount 120 compensates for daily and seasonal variations of direction that will optimize the solar incident flux, while the geographic affect is built into the mount.
Polar mount 120 includes poles 126 and 127, both having proximal and distal ends 128 and 130, with respect to ground 110, wherein proximal ends 128 are fixed to ground 110. A rod 122, extending north to south between distal ends 130 of poles 126 and 127, makes an angle p with the face of the earth (ground 110), angle p being substantially equal to the geographical latitude. Rod 122 defines a length axis 121 A, which is parallel to the axis of rotation of the earth, i.e., the line connecting the Earth's poles.

a spring 52, mounted on drum external surface 41, having a spring axis 59, orthogonal to drum axis of rotation 43; and
an anchor 54, mounted on drum external surface 41.
Additionally, radio-dial drive 20 includes a cylindrical capstan 50, mounted on support structure 45, adjacent to drum 42. Capstan 50 defines a capstan axis of rotation 47, parallel to drum axis of rotation 43, and a capstan external surface 49, along its circumference.
A cable 56, having first and second ends 51 and 53, respectively, is tightly wound around drum 42 in a first direction, and around capstan 50 in a second direction, wherein first end 51 is fixedly attached to spring 52 and second end 53 is fixed against drum external surface 41 by anchor 54.
Additionally, spring 52 is held in tension with a force which is just greater than the required force for turning drum 42 and shaft 48, so that turning the capstan 50 in a first direction will turn drum 42 in a second direction, with substantially zero backlash and substantially zero drift
Substantially zero backlash relates to a near absence of slack in cable 56, as capstan 50 changes a direction of rotation, for example, from clockwise to counterclockwise, or vice versa.
Substantially zero drift relates to a near absence of slippage in cable 56 against drum external surface 41, and against the capstan surface 49.
The travel of drum 42 is described by an arrow 55 and is preferably ± 90°, for
an arc of 180°. It will be appreciated that other values which may be smaller or larger are also possible. Capstan 50, which is considerably smaller than drum 42, makes several revolutions, as illustrated by an arrow 57, as drum 42 completes an arc of 180°. The diametric ratios of drum 42 and capstan 50 may be, for example, 1 to 6.5. It will be appreciated that other values, which may be smaller or larger, are also possible.
A computer-controlled motor 40, or another computer controlled drive system provides the tuning or tracking motion to capstan 50, based on an expression for the direction that will maximize the solar incident flux, as functions of date, time, and geographic location. Motor 40 may be a stepped motor or a DC motor. Additionally, a close-loop system, described hereinbelow, in conjunction with Figures 4A - 4B and 5 may be used.

substantially focus the incident radiation to a focal point, may be used. Alternatively still, concentrator 12 may be trough-like.
Additionally, drive unit 14 includes at least a first drive module 20A (Figure 4A and 4B), for solar tracking along a first axis, and preferably also, a second drive module 20B (Figure 4B), for solar tracking along a second axis, orthogonal to the first axis. Drive unit 14 further includes a counterweight 26.
Concentrating dish 12 preferably includes a rim 30. A reflector 32 forms the surface of concentrating dish 12, which faces the sun. The angle between rim 30, a focal point F of dish 12, and a center P is ex, which may be used as a measure of the concentrating power of dish 12.
A power conversion unit 34, substantially at the focal point of concentrating dish 12, may be photovoltaic cells, adapted for concentrated radiation. Alternatively, a thermal engine or another known method of producing electric power may be used.
Drive unit 14 is mounted on pedestal 16, structured so that it can cany the loads of dish 12 and the drive unit 14, while allowing full motion of the drive modules 20A and 20B.
Dish 12 is attached to module 20B through a dish support 28.
Preferably, Collector 10 includes two degrees of motion.
When constructed as an azimuth-elevation mount or as a cross mount, these two motions simultaneously track the sun with respect to geographic, seasonal and daily variations.
Referring further to the drawings, Figure 5 schematically illustrates collector 10, mounted on a polar mount 120, and preferably incorporating two radio-dial drives, in accordance with the present invention.
Accordingly, Collector 10 includes polar mount 120, having two poles 126 and two poles 127 (of which only one is seen in the pictorial representation), all having proximal ends 128, with respect to ground 110, and are fixed to ground 110 at their proximal ends 128. Poles 126 and 127 are connected by a rod 122, at their distal ends 130. Rod 122 makes angle P with the earth surface.
Polar mount 120 further includes daily axis of rotation 121 A, for following the daily motion of the sun, from east to west
Additionally, polar mount 120 includes seasonal axis of rotation 121B, for correcting the daily solar tracking for the seasonal changes, Le., the tilt of the sun's

somewhat, so that reflector 12 may be actually pointing off from the orientation specified by the expression for the direction that will maximize the solar incident flux. The closed loop operation may then correct for the inaccuracy, by reporting to the computer that the solar incident flux is less than that which can be realized, leading the computer to specify a correction to the motion.
It is in this regard that the substantially zero backlash of radio-dial mechanism 20 is important Backlash may occur with a change in the direction of motion, and generally, the basic tracking motion is unidirectional (except for seasonal changes in direction, twice a year, in the spring and fall). Thus the basic motion should not encounter backlash. However, the correction, as specified by the closed-loop system, may be in any of the two directions of motion of each axis, and must be highly accurate. Therefore, radio-dial mechanism 20, with its substantially zero backlash and substantially zero drift is particularly suitable for the correction motion, as specified by the closed loop system.
Preferably, the closed-loop system is additional to the system operated by the computer-calculated expression for the direction that will maximize the solar incident flux.
Alternatively, only a closed loop system, or only a computer-calculated expression for the direction that will maximize the solar incident flux may be employed.
Another aspect of the present invention relates to employing a Combined Heat and Power (CHP) circuit, for increased cost-effectiveness of the small-scale solar power system.
Thus, Figure 6 schematically illustrates a CHP circuit 150, in accordance with the present invention.
Accordingly, CHP circuit 150 operates with a preferably closed-loop primary coolant circulating system 155, driven by a pump 158. The coolant may be water, oil, or another fluid, for example, a gas.
Thus, CHP circuit 150 includes a power generation module 152, which includes at least one Collector 10 (Figures 4A - 4B and 5), having at least one power conversion unit 34, for example, a thermal engine or concentrated photovoltaic cells. A control system 153, preferably supported by a closed loop system 157 controls the tracking of at least one collector 10.

backup heater 189, as known. Hot water from hot-water tank 188 may supply general
hot water needs 190 of residential unit 180, as well as space heating 192, for example,
through radiators, or under-floor water pipes.
As has been illustrated in conjunction with Figure 6, the coolant of the primary
loop of CHP circuit 150 flows to excess heat exchanger 156, where excess heat is
removed. Pump 158 ensures circulation-Referring further to the drawings, Figure 8 schematically illustrates a CHP
circuit 200 for a cluster of solar collectors, for residential or small commercial unit
210, in accordance with the present invention.
The advantage of using a cluster of concentrating solar collectors 10, is that
power collection is greatly increased, while the number of auxiliary components, such
as secondary heat exchanger 156 and pump 158, and control unit 153 remains the
same, so as to further improve the cost effectiveness and economic viability of the
system. Additionally, maintenance could be simplified for a single component
replacing many identical smaller components.
The operation of cluster 200 is similar to the operation of system 170 (Figure
7), with the following exceptions:
1. Electrical interfaces 172 of each concentrating solar collectors 10 may be connected in series or in parallel, or in a combination of series and parallel connections, providing flexibility in power and voltage input to a residential unit 210.
2. At the same time, the control of all concentrating solar collectors 10 may be performed by control unit 153 (Figure 6), since the tracking data for all concentrating solar collectors 10 is the same.
3. The hot water interfaces from all collectors may be connected to a single secondary closed loop system. The connection is in parallel. The pipe leads to a central primary heat exchanger in the hot water tank, a central secondary heat exchanger, and a single pump. Since the plurality of collectors are connected in parallel, each collector receives the same low inlet temperature and the total flow rate in the pump and in the main pipe is the sum of flow rates in all the collectors.
4. Although the number of collectors connected in parallel to a single pump and heat exchanger is not limited in principle, it may be reasonable to divide a large field into several independent sections, to limit the cost of the tubes.

It will be appreciated that in general, the cluster arrangement may be either closed loop or open loop. In general, a single control unit 153 may be used will all the collectors, but each may require its individual closed loop system 157.
The following are general design parameters for the present invention.
A typical size for a solar energy system of the present invention, as illustrated in Figures 4A — 4B and 5 may be a concentrator diameter of between about 0.5 meters and about 2 meter, and preferably, about 1 meter, capable of producing about 150 Watts of electricity, together with about 350 Watts of heat Thus, the structural support of the collector needs be relatively light, since the wind loads are relatively small. The tracking mechanism is relatively simple and can be manufactured relatively inexpensively.
The cost of manufacturing such a system is estimated at about $2 per Watt at peak power. The required investment for a suitable production line is estimated at about $5M. Given an annual production rate of 5 Megawatts and an interest rate of 5%, the surcharge for repaying the initial investment is estimated at only about $0.13 per Watt at peak power. Therefore the required market volume for the proposed small-scale system is smaller by an order of magnitude than that of current, large systems, and the required investment risk is correspondingly smaller.
The small-scale solar energy systems can be installed at the point of consumption, such as on rooftops of domestic and public buildings, in urban environment, supplying them with both power and hot water, for domestic water and space heating. With a Combined Heat and Power (CHP) system an overall efficiency of the system may be competitive with fossil fuel power plants.
Cost estimates are based on an annual production rate of 250,000 m , which corresponds to 1.2 million and 260,000 units per year for concentrators of between about 0.5 m and LI m in diameter. The production period, i.e., the period during which the system may be produced and sold, and the initial investment can be amortized and recovered is about 10 years.
Design parameters, considerations, and requirements for Collector 10 of Figures 4A - 4B and 5 are discussed below:
1. Reflector 12 may be designed as a concave parabolic dish with a projected
(aperture) diameter of about between 0.5 and 2 meters, and preferably about 1.1 meter in diameter. It will be appreciated that other diameters are also possible.

comparison, for small-scale systems, the problem of wind resistance is far less acute.
2. With an efficiency of power conversion to photovoltaic cells in the range of 10 to about 37 percent, most of the solar energy is discharged as heat Yet in a centralized, remote area there is little opportunity to utilize that heat, for example, in a Combined Power and Heat (CPH) system, thus the heat is wasted. By comparison, small-scale systems, built on rooftops, may be designed as Combined Power and Heat (CPH), with a considerably increase in overall efficiency.
3. The large concentrating solar power systems are installed away from the consumer. Therefore additional costs due to power distribution and to transmission losses are incurred, reducing the amount of available electricity by 10-20%, and raising the cost of the electric power thus produced by factors of between 2 and 3. Yet with large concentrating systems of photovoltaic cells, transmission and distribution costs cannot be avoided since the systems are too large to be installed at the points of consumption. By comparison, for small-scale systems, built on rooftops, at the point of consumption, there are not distribution costs and no transmission losses to speak of.
4. The initial investment for large concentrating solar power systems is very high, making decisions in this regard difficult, bureaucratic, and risky. By comparison, for small-scale systems, the decision is of the individual homeowner, and governmental incentives may be used to make it less risky.
5. Furthermore, competitive costs may be realized for large concentrating solar power systems if a significant number of them, equivalent for example, to at least 50 megawatt per year, is manufactured. Yet such a market volume is difficult to guarantee; therefore, the investment arid the risk associated with the development of such large systems are very high. By comparison, for small-scale systems, given governmental incentives, such a market may be realized.
6. Large concentrating solar power systems must be installed by trained personnel with specialized equipment and facilities, requiring special contractors, and special licenses, which increase their costs. By comparison,

embodiments and aspects of the present invention as delineated hereinabove and as claimed in the claims section below finds experimental support in the following examples.
It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment Conversely, various features of the invention, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable subcombination.
Although the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the spirit and broad scope of the appended claims. All publications, patents and patent applications mentioned in this specification are herein incorporated in their entirety by reference into the specification, to the same extent as if each individual publication, .patent or patent application was specifically and individually indicated to be incorporated herein by reference. In addition, citation or identification of any reference in this application shall not be construed as an admission that such reference is available as prior art to the present invention.

What is claimed:
1. A high-efficiency, small-scale, combined heat and power, concentrating
solar energy system comprising:
at least one collector, which comprises:
a concentrator, having an aperture of between about 0.5 m about 2 meters, adapted for focusing incident solar radiation to a focal point;
at least one drive on which said concentrator is mounted, said drive being adapted for tracking a direction that will maximize the solar incident flux, at least along one axis;
a control unit, in communication with said drive, for controlling said drive, based on an expression of said direction, as functions of time of day, season, and geographic latitude; and
a power conversion unit, substantially at said focal point; a power supply system, which receives electrical power from said power conversion unit;
a heat supply system, which receives heat from a cooling system of said power conversion unit,
wherein a combined heat and power efficiency of said high-efficiency, small-scale, combined heat and power, concentrating solar energy system is greater than 60% overall efficiency.
2. The high-efficiency, small-scale, combined heat and power, concentrating solar energy system of claim 1, wherein a combined heat and power efficiency of said high-efficiency, small-scale, combined heat and power, concentrating solar energy system is greater than 65% overall efficiency.
3. The high-efficiency, small-scale, combined heat and power, concentrating solar energy system of claim 1, wherein a combined heat and power efficiency of said high-efficiency, small-scale, combined heat and power, concentrating solar energy system is greater than 70% overall efficiency.

f
4. The high-efficiency, small-scale, combined heat and power, concentrating solar energy system of claim 1, wherein a combined heat and power efficiency of said high-efficiency, small-scale, combined heat and power, concentrating solar energy system is greater than 75% overall efficiency.
5. The high-efficiency, small-scale, combined heat and power, concentrating solar energy system of claim 1, wherein said at least one collector comprises a plurality of collectors, arranged as a cluster, each including said heat supply system, and further wherein said heat supply systems from each collector are arranged in parallel, so as to have the same inlet and outlet coolant conditions.
6. The high-efficiency, small-scale, combined heat and power, concentrating solar energy system of claim 1, wherein said heat supply system operates an air conditioning system.
7. The high-efficiency, small-scale, combined heat and power, concentrating solar energy system of claim 1, wherein said collector includes a closed loop system.
8. The high-efficiency, small-scale, combined heat and power, concentrating solar energy system of claim 1, wherein said at least one drive includes at least two drives, adapted for tracking a direction that will maximize the solar incident flux, at least along two axes.
9. The high-efficiency, small-scale, combined heat and power, concentrating solar energy system of claim 1, wherein said at least one drive is a radio dial drive.
10. A celestial tracking system, comprising: a first main support;
a first tracking unit, mounted on said first main support, which comprises:

a first radio-dial drive for celestial tracking mechanism, comprising:
a first support structure;
a first cylindrical drum, mounted on said support structure, said drum defining a drum axis of rotation and a drum external surface, along its circumference, and said drum having:
a first central shaft, parallel to said drum axis of rotation, and fixedly attached to said drum, so as to rotate with said drum, in said axis of rotation;
a first spring, mounted on said drum external surface, having a spring axis orthogonal to said drum axis of rotation; and
a first anchor, mounted on said drum external surface;
a first cylindrical capstan, mounted on said support structure, adjacent to said drum, and defining a capstan axis of rotation, parallel to said drum axis of rotation and a capstan external surface, along its circumference;
a first cable, having first and second ends, said cable being tightly wound around said drum in a first direction, and around said capstan in a second direction, wherein said first end is fixedly attached to said anchor and said second end is fixedly attached to said spring, and wherein said spring is held in tension with a force which is greater than the required force for turning said drum, so that turning the capstan in a first direction will turn the drum in a second direction, with substantially zero backlash and substantially zero drift; and
a first motor, mounted on said main support, for providing a tracking motion.
11. The celestial tracking system of claim 10, wherein said first motor is selected from the group of a step motor and a DC motor.
12. The celestial tracking system of claim 10, and further including a timing belt arranged between said first motor and said first cylindrical capstan.

13. The celestial tracking system of claim 10, wherein said first tracking unit is arranged on a first axis of rotation, and further including a second tracking unit, arranged on a second axis of rotation, and comprising:
a second radio-dial drive for celestial tracking mechanism, comprising:
a second support structure;
a second cylindrical drum, mounted on said second support structure, said second drum defining a second drum axis of rotation and a second drum external surface, along its circumference, and said second drum having:
a second central shaft, parallel to said second drum axis of rotation, and fixedly attached to said second drum, so as to rotate with said second drum, in said second axis of rotation;
a second spring, mounted on said second drum external surface, having a second spring axis, orthogonal to said second drum axis of rotation; and
a second anchor, mounted on said second drum external surface;
a second cylindrical capstan, mounted on said second support structure, adjacent to said second drum, and defining a second capstan axis of rotation, parallel to said second drum axis of rotation and a second capstan external surface, along its circumference;
a second cable, having first and second ends, said second cable being tightly wound around said second drum in a first direction, and around said capstan in a second direction, wherein said first end is fixedly attached to said second anchor and said second end is fixedly attached to said second spring, and wherein said second spring is held in tension with a force which is greater than the required force for turning said second drum, so that turning said second capstan in a first direction will turn the drum in a second direction, with substantially zero backlash and substantially zero drift; and
a second motor, mounted on said second main support, for providing a second tracking motion.

14. The celestial tracking system of claim 10, and further including a
concentrating solar energy system, comprising:
a collector; and
a power conversion unit.
15. The celestial tracking system of claim 10, and further including a control unit, in communication with said motor, for controlling said tracking motion, using an expression for the direction that will maximize the solar incident flux.
16. A solar energy system, comprising:
a first main support of said solar energy system;
a first tracking unit, mounted on said first main support, which comprises:
a first radio-dial drive for celestial tracking mechanism, comprising:
a first support structure;
a first cylindrical drum, mounted on said support structure, said drum defining a drum axis of rotation and a drum external surface, along its circumference, and said drum having:
a first central shaft, parallel to said drum axis of rotation, and fixedly attached to said drum, so as to rotate with said drum, in said axis of rotation;
a first spring, mounted on said drum external surface, having a spring axis orthogonal to said drum axis of rotation; and
a first anchor, mounted on said drum external surface;
a first cylindrical capstan, mounted on said support structure, adjacent to said drum, and defining a capstan axis of rotation, parallel to said drum axis of rotation and a capstan external surface, along its circumference;
a first cable, having first and second ends, said cable being tightly wound around said drum in a first direction, and around said capstan in a second direction, wherein said first end is fixedly attached to said anchor and said second end is fixedly attached to said spring, and wherein said spring is held in

tension with a force which is greater than the required force for turning said drum, so that turning the capstan in a first direction will turn the drum in a second direction, with substantially zero backlash and substantially zero drift;
a first motor, mounted on said main support, for providing a tracking motion;
a collector; and
a power conversion unit.
17. A central plant, comprising: a plurality of units, each of said units including: a first main support;
a first tracking unit, mounted on said first main support, which comprises:
a first radio-dial drive for celestial tracking mechanism, comprising:
a first support structure;
a first cylindrical drum, mounted on said support structure, said drum defining a drum axis of rotation and a drum external surface, along its circumference, and said drum having:
a first central shaft, parallel to said drum axis of rotation, and fixedly attached to said drum, so as to rotate with said drum, in said axis of rotation;
a first spring, mounted on said drum external surface, having a spring axis orthogonal to said drum axis of rotation; and
a first anchor, mounted on said drum external surface;
a first cylindrical capstan, mounted on said support structure, adjacent to said drum, and defining a capstan axis of rotation, parallel to said drum axis of rotation and a capstan external surface, along its circumference;
a first cable, having first and second ends, said cable being tightly wound around said drum in a first direction, and around said capstan in a second direction, wherein said first end is fixedly attached to said anchor and said second end is fixedly attached to said spring, and wherein said spring is held in

tension with a force which is greater than the required force for turning said drum, so that turning the capstan in a first direction will turn the drum in a second direction, with substantially zero backlash and substantially zero drift;
a first motor, mounted on said main support, for providing a tracking motion;
a first transmission system, in communication both with said motor and with said cylindrical capstan, for transmitting said tracking motion from said motor to said capstan;
a collector; and
a power conversion unit.
18. The central plant of claim 17, wherein said first motor is selected from the group of a step motor and a DC motor.
19. The central plant of claim 17, wherein said first tracking unit is arranged on a first axis of rotation, and further including a second tracking unit, arranged on a second axis of rotation, and comprising:
a second radio-dial drive for celestial tracking mechanism, comprising:
a second support structure;
a second cylindrical drum, mounted on said second support structure, said second drum defining a second drum axis of rotation and a second drum external surface, along its circumference, and said second drum having:
a second central shaft, parallel to said second drum axis of rotation, and fixedly attached to said second drum, so as to rotate with said second drum, in said second axis of rotation;
a second spring, mounted on said second drum external surface, having a second spring axis, orthogonal to said second drum axis of rotation; and
a second anchor, mounted on said second drum external surface;
a second cylindrical capstan, mounted on said second support structure, adjacent to said second drum, and defining a second capstan axis of

rotation, parallel to said second drum axis of rotation and a second capstan external surface, along its circumference;
a second cable, having first and second ends, said second cable being tightly wound around said second drum in a first direction, and around said capstan in a second direction, wherein said first end is fixedly attached to said second anchor and said second end is fixedly attached to said second spring, and wherein said second spring is held in tension with a force which is greater than the required force for turning said second drum, so that turning said second capstan in a first direction will turn the drum in a second direction, with substantially zero backlash and substantially zero drift;
a second motor, mounted on said second main support, for providing a second tracking motion; and
a second transmission system, in communication both with said second motor and with said second cylindrical capstan, for transmitting said second tracking motion from said second motor to said second capstan.
20. The central plant of claim 17, wherein said collector has a real focal point and an aperture of between about 0.5 meter and about 2 meters.
21. The central plant of claim 17, wherein said power conversion unit is selected from the group consisting of a thermal generator, concentrated photovoltaic cells, and flat photovoltaic cells.
22. The central plant of claim 17, arranged as a Combined Heat and Power (CHP) system.
23. The central plant of claim 17, and further including differential means for measuring the solar incident flux, for providing a closed-loop control of said tracking motion.
24. The central plant of claim 17, and further including a control unit, in communication with said motor, for controlling said tracking motion, using an expression for the direction that will maximize the solar incident flux.

25. A heliostat, comprising:
a first main support for said heliostat;
a first tracking unit, mounted on said first main support, which comprises:
a first radio-dial drive for celestial tracking mechanism, comprising:
a first support structure;
a first cylindrical drum, mounted on said support structure, said drum defining a drum axis of rotation and a drum external surface, along its circumference, and said drum having:
a first central shaft, parallel to said drum axis of rotation, and fixedly attached to said drum, so as to rotate with said drum, in said axis of rotation;
a first spring, mounted on said drum external surface, having a spring axis orthogonal to said drum axis of rotation; and
a first anchor, mounted on said drum external surface;
a first cylindrical capstan, mounted on said support structure, adjacent to said drum, and defining a capstan axis of rotation, parallel to said drum axis of rotation and a capstan external surface, along its circumference;
a first cable, having first and second ends, said cable being tightly wound around said drum in a first direction, and around said capstan in a second direction, wherein said first end is fixedly attached to said anchor and said second end is fixedly attached to said spring, and wherein said spring is held in tension with a force which is greater than the required force for turning said drum, so that turning the capstan in a first direction will turn the drum in a second direction, with substantially zero backlash and substantially zero drift;
a first motor, mounted on said main support, for providing a tracking motion;
a first transmission system, in communication both with said motor and with said cylindrical capstan, for transmitting said tracking motion from said motor to said capstan; and a collector.

26. The heliostat of claim 25, wherein said first motor is selected from the group of a step motor and a DC motor.
27. The heliostat of claim 25, wherein said first tracking unit is arranged on a first axis of rotation, and further including a second tracking unit, arranged on a second axis of rotation, and comprising:
a second radio-dial drive for celestial tracking mechanism, comprising:
a second support structure;
a second cylindrical drum, mounted on said second support structure, said second drum defining a second drum axis of rotation and a second drum external surface, along its circumference, and said second drum having:
a second central shaft, parallel to said second drum axis of rotation, and fixedly attached to said second drum, so as to rotate with said second drum, in said second axis of rotation;
a second spring, mounted on said second drum external surface, having a second spring axis, orthogonal to said second drum axis of rotation; and
a second anchor, mounted on said second drum external surface;
a second cylindrical capstan, mounted on said second support structure, adjacent to said second drum, and defining a second capstan axis of rotation, parallel to said second drum axis of rotation and a second capstan external surface, along its circumference;
a second cable, having first and second ends, said second cable being tightly wound around said second drum in a first direction, and around said capstan in a second direction, wherein said first end is fixedly attached to said second anchor and said second end is fixedly attached to said second spring, and wherein said second spring is held in tension with a force which is greater than the required force for turning said second drum, so that turning said second capstan in a first direction will turn the drum in a second direction, with substantially zero backlash and substantially zero drift;

a second motor, mounted on said second main support, for providing a second tracking motion; and
a second transmission system, in communication both with said second motor and with said second cylindrical capstan, for transmitting said second tracking motion from said second motor to said second capstan.
28. The heliostat of claim 25, wherein said collector has a real focal point and an aperture of between about 0.5 meter and about 2 meters.
29. The heliostat of claim 25, and further including a control unit, in communication with said motor, for controlling said tracking motion, using an expression for the direction that will maximize the solar incident flux.
30. A central plant, comprising:
a plurality of heliostats, each of said heliostats including: a first main support;
a first tracking unit, mounted on said first main support, which comprises:
a first radio-dial drive for celestial tracking mechanism, comprising:
a first support structure;
a first cylindrical drum, mounted on said support structure, said drum defining a drum axis of rotation and a drum external surface, along its circumference, and said drum having:
a first central shaft, parallel to said drum axis of rotation, and fixedly attached to said drum, so as to rotate with said drum, in said axis of rotation;
a first spring, mounted on said drum external surface, having a spring axis orthogonal to said drum axis of rotation; and
a first anchor, mounted on said drum external surface;

a first cylindrical capstan, mounted on said support structure, adjacent to said drum, and defining a capstan axis of rotation, parallel to said drum axis of rotation and a capstan external surface, along its circumference;
a first cable, having first and second ends, said cable being tightly wound around said drum in a first direction, and around said capstan in a second direction, wherein said first end is fixedly attached to said anchor and said second end is fixedly attached to said spring, and wherein said spring is held in tension with a force which is greater than the required force for turning said drum, so that turning the capstan in a first direction will turn the drum in a second direction, with substantially zero backlash and substantially zero drift;
a first motor, mounted on said main support, for providing a tracking motion;
a first transmission system, in communication both with said motor and with said cylindrical capstan, for transmitting said tracking motion from said motor to said capstan; a collector, said central plant further including a power conversion unit.
31. The central plant of claim 30, wherein said first motor is selected from the group of a step motor and a DC motor.
32. The central plant of claim 30, wherein said first tracking unit is arranged on a first axis of rotation, and further including a second tracking unit, arranged on a second axis of rotation, and comprising:
a second radio-dial drive for celestial tracking mechanism, comprising:
a second support structure;
a second cylindrical drum, mounted on said second support structure, said second drum defining a second drum axis of rotation and a second drum external surface, along its circumference, and said second drum having:
a second central shaft, parallel to said second drum axis of rotation, and fixedly attached to said second drum, so as to rotate with said second drum, in said second axis of rotation;

a second spring, mounted on saia secona arum external surface, having a second spring axis, orthogonal to said second drum axis of rotation; and
a second anchor, mounted on said second drum external surface;
a second cylindrical capstan, mounted on said second support structure, adjacent to said second drum, and defining a second capstan axis of rotation, parallel to said second drum axis of rotation and a second capstan external surface, along its circumference;
a second cable, having first and second ends, said second cable being tightly wound around said second drum in a first direction, and around said capstan in a second direction, wherein said first end is fixedly attached to said second anchor and said second end is fixedly attached to said second spring, and wherein said second spring is held in tension with a force which is greater than the required force for turning said second drum, so that turning said second capstan in a first direction will turn the drum in a second direction, with substantially zero backlash and substantially zero drift;
a second motor, mounted on said second main support, for providing a second tracking motion; and
a second transmission system, in communication both with said second motor and with said second cylindrical capstan, for transmitting said second tracking motion from said second motor to said second capstan.
33. The central plant of claim 30, wherein said collector has a real focal point and an aperture of between about 0.5 meter and about 2 meters.
34. The central plant of claim 30, wherein said power conversion unit is selected from the group consisting of a thermal generator, concentrated photovoltaic cells, and flat photovoltaic cells.
35. The central plant of claim 30, arranged as a Combined Heat and Power (CHP) system.

me central plant of claim 30, and further including differential means for measuring the solar incident flux, for providing a closed-loop control of said tracking motion,
37. The central plant of claim 30, and further including a control unit, in communication with said motor, for controlling said tracking motion, using an expression for the direction that will maximize the solar incident flux.

Documents:

3355-chenp-2005 abstract-granded.jpg

3355-chenp-2005 abstract-granded.pdf

3355-chenp-2005 claims-granded.pdf

3355-chenp-2005 description (complete)-granded.pdf

3355-chenp-2005 drawings-granded.pdf

3355-chenp-2005-abstract.pdf

3355-chenp-2005-claims.pdf

3355-chenp-2005-correspondnece-others.pdf

3355-chenp-2005-correspondnece-po.pdf

3355-chenp-2005-description(complete).pdf

3355-chenp-2005-drawings.pdf

3355-chenp-2005-form 1.pdf

3355-chenp-2005-form 18.pdf

3355-chenp-2005-form 3.pdf

3355-chenp-2005-form 5.pdf

3355-chenp-2005-pct.pdf

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Patent Number

225550

Indian Patent Application Number

3355/CHENP/2005

PG Journal Number

52/2008

Publication Date

26-Dec-2008

Grant Date

19-Nov-2008

Date of Filing

12-Dec-2005

Name of Patentee

RAMOT AT TEL AVIV UNIVERSITY LTD

Applicant Address

32 HAIM LEVANON STREET, 69 975 TEL AVIV,

Inventors:

#	Inventor's Name	Inventor's Address
1	LEVY, NATHAN-ARIE	11 HAMERED STREET, 43414 RAANANA,
2	KRIBUS, ABRAHAM	2 SMILANSKI STREET, 76447 RECHOVOT,
3	KAFTORI, DANIEL	MOSHAV ALONEI ABBA, 36005 ALONEI ABBA,

PCT International Classification Number

F24J

PCT International Application Number

PCT/IL2004/000406

PCT International Filing date

2004-05-12

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	155867	2003-05-12	Israel