Combined solar electric power and liquid heat transfer collector panel

[0002] This is a Continuation-in-part of application no. 09/681,124 filed Jan. 15, 2001, now abandoned.

[0003] The sole inventor is Annemarie Hvistendahl Konold whose country of citizenship is the U.S.A and resides at: 23903 Malibu Knolls Road, Malibu, Calif. 90265.

[0004] Portion of the invention described herein was also described in patent application no. 09/681,123, filed. Jan. 15, 2001, now abandoned.

[0005] (1) Field of the Invention

[0006] 1. The present invention relates to the use of solar energy for conversion of solar energy to electrical and thermal energy with the added function of radiant cooling for general use with industrial/commercial processes requiring working fluid cooling; and using a heat transfer plate to heat a photovoltaic array to maintain its operating temperature in a range that provides maximum efficiency to improve electrical energy conversion in cold climates or winter conditions.

[0007] (2) Description of the Related Art

[0008] 2. The conversion of solar energy to thermal or electrical energy through the use of systems such as photovoltaic arrays, passive absorbers of solar energy, solar furnaces, trough concentrating collectors with sun trackers is well established in the art. U.S. Pat. No. 4,315,163 describes a multipower electrical system for supplying electrical energy to a house including a solar photovoltaic array, a battery charger and DC to AC inverter. U.S. Pat. No. 4,147,157 describes an active solar energy system comprising an array of solar collectors for both generating power for a pump; and for heating a fluid, a pumping device powered by the array to circulate the heated fluid and a storage tank to contain the heated fluid. Similarly, U.S. Pat. No. 5,293,447 describes a system for heating water using solar energy comprising a photovoltaic array, a water heater and a controller.

[0009] 3. Systems have also been proposed for simultaneously converting solar energy to thermal and electrical. For example, U.S. Pat. No. 4,392,008 describes a flat plated solar thermal collector below and in spaced conductive relationship to a plate-mounted array of photovoltaic cells. U.S. Pat. No. 5,522,944 describes an apparatus with an array of photovoltaic cells and a plurality of interconnected heat collecting tubes disposed on the same plane with the array.

[0010] 4. Other systems attempting to optimize electrical energy conversion and provide conversion to thermal energy from solar energy have been proposed. For example, U.S. Pat. No. 4,373,308 describes a solar cell array consisting of individually relatable, elongated segments driven by a sun tracker and motor with a thermal solar collector supported beneath the solar cell array for utilization of solar energy received through a roof opening in a building. U.S. Pat. No. 6,018,123 describes a solar cell module provided at the position of a heat collecting plate inside a heat collector in which hot air can be led into a house while maintaining the performance of solar cells.

[0011] 5. However, there is an unmet need in the art for improvements to optimize systems that convert solar energy to both thermal and electrical energy efficiently in colder climates adding a function to radiate heat to cool fluids and keep the collectors free of snow and ice.

[0012] 6. The invention provides enhanced performance characteristics and adds a heat radiator function within a single enclosure that previous inventions do not provide.

[0013] 7. Included within a single enclosure is a photevoltaic grid that converts solar energy into electrical energy, a thermally conductive heat transfer plate disposed on a plane below the photovoltaic grid. The heat transfer plate converts the solar energy in thermal energy uniformly distributed over the entire plate. On a plane below the plate but thermally coupled to the plate by a thermal conductive compound are copper tubes which impart the thermal energy from the plate to a fluid disposed inside the tube heating the fluid to a high temperature before being discharged from the enclosure.

[0014] 8. In a radiator mode, a hot fluid is introduced to the copper tubes that absorb the heat form the fluid, cooling the fluid. This thermal energy is conducted from the tubes to the heat transfer plate that radiates the thermal energy through the photovoltaic grid and out through the glass covered top of the enclosure.

[0015] 9. The capability to convert solar energy to electrical energy and to thermal energy is improved by the addition of a Fresnel lens array supported above the photovoltaic grid by lens support panels riveted to the enclosure. The Fresnel lens magnifies the amount of insolation (solar energy) received by the photovoltaic grid and the thermal transfer plate.

[0016] The Fresnel lens is held in place on the lens supports by lens retainer in a manner that imparts a curvature to the lens. This curvature allows the lens to magnify the available insolation regardless of the Sun's position providing a passive solar tracker capability. Thus the need for a Sun tracker sensor, drive electronics and a drive motor coupled to the lens array is not required, saving energy, weight and cost. Testing has shown that the performance of the photovoltaic grid is improved by at least 14 percent using this lens feature.

[0017] 10. The ability to remove heat from a hot fluid and radiate the heat through the photovoltaic grid and out the enclosure top heats the lens array and the surrounding lens support panels. This heating ability allows operation of the collector in cold climates preventing the build up of ice and snow on the collector.

[0018] 11. A temperature sensor is provided so that when the sensor output signal is coupled to a microprocessor-based controller, thermostat or Proportional-Integral-Derivative (PID) controller, fluid flow rate can be regulated as a function of its discharge temperature. By this method, fluid discharged from the collector can be maintained at a constant temperature. Since this temperature is also proportional to the photovoltaic grid temperature, the photovoltaic operating temperature can maintained within the preferred range of 70° F. to 100° F. which is the range where the photovoltaic grid is most efficient.

[0019] 12. Another benefit is provided with the flow of cold fluid through the collector panels, if mounted on a building roof, reduces the roof temperature in the immediate area around the panel enclosure from roof temperatures of 100° F. to 140° F. down to 80° F. to 120° F. depending upon the building environmental conditions. This ability to cool roofs augments or replaces building air conditioning thus providing a savings in building air conditioning costs.

[0020] 13. FIG. 1 is a conceptual depiction of the collector panels installed in a system illustrating the primary components employed to provide simultaneous electric power and heat from a single system using a single set of Solar collection panels.

[0021] 14. FIG. 2 shows the three views of the Collector Panel comprised of the Photovoltaic electric, the heat exchanger, and the Fresnel lens assembly. The electrical and plumbing fittings are provided for interconnection of multiple Solar Collector panel units, and connection of the panels to accompanying electrical energy storage and thermal energy storage or dissipation systems.

[0022] 15. FIG. 3 shows the Collector Panel sizes and power & heat capacities for assembly into multiple-panel arrays.

[0023] 16. FIG. 4 illustrates the internal design of the Collector Panel indicating the integration of the Photovoltaic grid, the heat exchanger, and the Fresnel lens assembly. The Photovoltaic grid and the heat exchanger are interfaced through a copper heat conducting-plate for uniform and efficient heat absorption and radiation.

[0024] 17. FIG. 5 shows the Collector Panel array for simultaneous liquid heating and/or panel warming and electric poster generation. Cold liquid flows from the consumer's plant into the panels and heated liquid flows out of the panels into the consumer's plant. Electric current flow to the consumer's plant is included.

[0025] 18. FIG. 6 shows the Collector Panel array for simultaneous liquid cooling and/or Collector Panel warming and electric power generation. Hot liquid flows from the consumer's plant into the panels and cooled liquid flows out of the panels into the consumer's plant. Electric current flow to the consumer's plant is included.

[0026] 19. FIG. 7 shows the components provided and their connection for the electrical segment of the Collector panel, including a list of consumer plant systems with which the electrical segment is integrated.

[0027] 20. FIG. 8 shows the components provided and their connection for the heat transfer segment of the Collector panel, including a list of consumer plant systems with which the heat transfer segment is integrated.

[0028] 21. The invention employs a Solar Collector Panel [100] that is a self-contained, compact Solar Photovoltaic and heat energy absorption and dissipation unit that provides electric power and liquid heat transfer from within a single integrated unit. The heat Transfer Unit [102]. [203] includes a copper plate [403] and a copper tubing heat exchanger [404]. Typically, solar collector panels [100] are integrated within a system to provide a heated liquid for a building liquid system and simultaneously provide electrical power for a building electrical system. As shown in FIG. 1, a photovoltaic unit [101] portion of a panel has its electrical output connected to a battery charge controller [106] which charges a battery bank [103] which, in turn, drives a DC to AC inverter [107] providing useful AC electrical power that is fed into the building electrical system. There are numerous variations of this arrangement that are well understood in the art. Also shown in FIG. 1, is the heat transfer unit [102] whose liquid discharge is connected to a closed liquid loop pressurized by a liquid pump [105] that pumps the heated liquid into liquid storage tanks [104] and then out to the building liquid system for heated liquid fluid use, returning cooler liquid to a liquid input of the panel There are also numerous variations of this arrangement that are well understood in the art.

[0029] 22. FIG. 2 shows the three views of the Solar Collector Panel [100] comprising the Photovoltaic (PV) grid [201],[401], the copper tubing heat exchanger [404], and the Fresnel lens [205],[409] assembly. The Fresnel lens [205], [409] assembly is employed to increase the Solar electric and heat energy capturing capacity of the panel. Initial testing indicates that the increase is as much as 14 percent above conventional solar electric and heating panels. Through its shape, the Fresnel lens [205], [409] assembly also provides static Sun tracking to maximize solar energy capture, without the use of mechanical rotating or positioning mechanisms. The Fresnel lens [205], [409] provide this enhancement on days of partial overcast as well as on Sunny days. As seen in FIG. 3, the Solar Collector Panel [100] is provided in a range of sizes and capacities to provide flexibility in grouping of arrays to meet consumer energy requirements.

[0030] 23. FIG. 4 gives the detailed design of the integrated Solar Collector Panel [100]. As shown in the panel Section A—A, a copper plate [403] is mated between the Photovoltaic (PV) grid [201], [401] substrate and the copper tubing heat exchanger [404] to uniformly absorb incoming heat from the Sun and distribute it to the copper tubing heat exchanger [404]. Similarly, the copper plate [403] uniformly distributes heat from the copper tubing heat exchanger [404] to the Photovoltaic (PV) grid [201], [401] substrate for radiation to the atmosphere when the Solar Collector Panel [100] is connected for heat dissipation. Foam insulation [405] lies between the copper tubing heat exchanger [404] and the bottom cover plate [406] to reduce heat leakage from the Solar Collector Panel [100], retaining maximum heat for transfer to or from the user plant.

[0031] 24. An anodized aluminum frame [407] has attached to the bottom of the frame along the length of a first long side and a second long side, an L-shaped aluminum channel with mounting holes disposed evenly across the length of the channel. These mounting holes allow for the fastening of the collector panel frame to a footing or building roof using standard bolts. Rivets attach the L-channels.

[0032] 25. In a similar manner, aluminum lens supports [411] are riveted along the length of each side of the frame [407]. The height of these supports are selected to allow positioning of the lens assembly 6.5 to 7.5 inches above a bottom surface of a glass/plastic cover plate [408] depending upon the panel size or 5.5 inches above a top surface of the glass/plastic cover plate [408]. This distance was selected to ensure that the focal point of the Fresnel lens [205], [409] lies below the plane of the photovoltaic grid [201], [401] so that hot spots due to insolation magnification don't form on the grid.

[0033] 26. As seen in FIG. 2, openings, or louvers [206], are provided in the lens supports [411] with movable sections to control air and rain flow across the grid surface. For cold climate installation, the louvers [206] are opened for maximum heat radiation, airflow, and release of impingent snow and ice. For warm climate installation, the lens support louvers [206] are closed to preclude the leakage of captured heat, which would otherwise be caused by airflow across the grid surface.

[0034] 27. Along the top inside edge, evenly disposed along the full length of each lens support [411] are lens retainers [410] fastened to the lens supports [411] by screws. Each lens retainer [410] has a grove sized to receive the edge of the Fresnel lens [205], [409] similar to a tongue and grove fitting to hold the lens firmly in position. The lens retainers [410] are fabricated either from a hard rubberized material or plastic. In the preferred embodiment, the lens retainers [410] are plastic. Each short side of each Fresnel lens [205], [409] is secured to the lens retainers [410] in this manner. The length of each lens retainers [410] matches the length of each Fresnel lens [205], [409] short side dimension.

[0035] 28. As shown in FIG. 4, View A—A, the solar collector panel [100] is constructed as a sandwich of component layers. The first layer is the glass/plastic cover plate [408] held in place by the overlaying lip formed on the top of the frame [407] side members. In the preferred embodiment the cover plate [408] is made from glass but it can be plastic. Mounted below the cover plate [408] is the photovoltaic (PV) grid [401]. The photovoltaic grid [401] is a commercial unit available from Kyocera, Siemens and BP. Below that is mounted the heat transfer copper plate [403] for uniform and efficient heat absorption and radiation. In the preferred embodiment the plate is made from copper. For maximum heat transfer, a copper tubing heat exchanger [404] is bonded to the heat transfer copper plate [403] using a thermal conducting compound. In the preferred embodiment, the copper tubing heat exchanger [404] is made from copper tubing and the compound is a copper-filled epoxy.

[0036] 29. Foam insulation [405] lies between the copper tubing heat exchanger [404] and the frame [407] bottom cover plate [406]. Rivets secure the bottom cover plate [406] so that the entire collector panel sandwich is firmly held in place.

[0037] 30. The above-unsealed Solar Collector Panel [100] is designed to be a self-contained, compact Solar Photovoltaic and heat energy absorption and dissipation unit that provides electric power and liquid heat transfer from within a single integrated unit

[0038] 31. Plenum, high temperature rated cabling 200° C., 14 gauge is attached to the photovoltaic grid [201], [401] and brings the electrical energy out to the electrical function box and conduit elbow fitting [202], [402]. Connections to the Photovoltaic grid are made through the electrical junction box and conduit elbow fitting [202], [402]. Signal cabling from the discharge temperature sensor [809], described below, is also brought through the electrical junction box and conduit elbow fitting [202], [402]. The electrical junction box and conduit elbow fitting [202], [402] facilitates the connection of any number of Collector Panels [100] into arrays [700], [800] as illustrated in FIGS. 5, 6, 7, and 8.

[0039] 32. Connections to the copper tubing heat exchanger [404] are through standard pipe thread fittings [204], [505], [605]. The pipe thread fittings [204], [505], [605] facilitate the joining of any number of Collector Panels [100] into arrays [700], [800] as illustrated in FIGS. 5 and 6. The copper tubing heat exchanger [404] of the Collector Panel [100] accommodates any non-corrosive liquid.

[0040] 33. As shown in FIG. 7, electric current is drawn from the photovoltaic grid [201], [401] of the collector panels [100] and delivers DC current [503], [603] to operate electrical apparatus. This DC current [503], [603] is connected to a building plant electrical power system as shown in FIG. 6 to charge batteries that store energy for subsequent use. Such battery charging systems with DC to AC conversion systems are well understood in the art.

[0041] 34. In general, battery charge regulators [701] keep the battery bank [702] charged, prevent overcharging, and regulate electric current flow from the photovoltaic grid [201], [401] to the battery bank [702]. Battery output current is supplied to one or more DC to AC inverters [703] to convert DC battery power to AC power to supply power at the required voltage and frequency to operate consumer electrical apparatus. A battery voltage sensor [704] may be provided to determine when the Solar array power is not sufficient to keep the battery bank [702] fully charged to satisfy consumer power demand, at which time it activates a transfer relay [705] to connect the battery charger [706] to city mains or a consumer auxiliary generator for additional power. The consumer can be provided with additional control of the transfer relay [705] to direct city mains power to his plant and/or feed unused solar power from the DC to AC Inverter [703] back to the city utility grid.

[0042] 35. The electrical junction box and conduit elbow [202], [402] facilitate the joining of any number of Collector Panels [100] into arrays [700], [800] as illustrated in FIGS. 5 and 6. By the means described above, the Collector Panel array is integrated with consumer electric systems such as power distribution, electric space heating, and industrial process power and control systems thus replacing or augmenting the electrical components of these systems.

[0043] 36. In a warm or hot climate, as shown in FIG. 5, a liquid is heated fort household or commercial domestic use. Similarly, a liquid is heated for an industrial or commercial manufacturing process. Cold liquid [501] flows from a consumer's plant into the panels and heated liquid [502] flows out of the panels' into the consumer's plant. As illustrated in FIG. 8, an array of the Collector Panels [700], [800] may be integrated with consumer plant systems such as an Air Conditioning or a heat pump system to add or remove heat, thus replacing or augmenting the heat transfer components of these systems.

[0044] 37. Controlling fluid flow in consumer plant heat transfer systems is generally understood in the art. Check valves [803], [807] provide liquid flow in a single direction to prevent the flow directly from the source into the consumer plant. A shutoff valve [804] can be provided for consumer control of incoming liquid. A control valve [810] is often provided for consumer control of liquid flow to and from storage tanks [801], such as rooftop tanks [808] combined with a rain collector [805], filter [806], and check valve [807]. The roof top tank [808] provides plant liquid pressurization in the absence of other sources of pressurization, such as city water.

[0045] 38. In a cold climate, as shown in FIG. 6, a liquid is cooled for industrial processes or machines such as a stationery engine. Hot liquid [601] flows from a consumer's plant into the panels and cooled liquid [602] flows out of the panels into the consumer's plant. A rooftop may be heated through the Collector Panels [100] to reduce snow and ice build-up, and keep the Collector Panels [100] free of snow and ice.

[0046] 39. Depending upon the climate where the Collector Panel array [700], [800] is installed, heat is removed from or added to the Panels improving their Photovoltaic efficiency, minimizing thermal stress and material deterioration to yield maximum lifetime, and providing a cooled or heated liquid for the consumer at the same time. Consumer plant liquid flow and temperature control and thermal energy storage or dissipation is provided through a temperature sensor [809] included as part of the Collector Panel [100]. The sensor is an integral part of the Collector Panel [100] for domestic, industrial, and commercial system/process controls. The sensor analog output signal can be interfaced to a controller device [811] which can be a process control microprocessor, programmable controller, or Proportional-Integral-Derivative (PfD) 3-mode controller whose output controls a proportional flow control valve to control liquid flow as a function of collector panel discharge flow temperature. The Panel photovoltaic grid temperature is thus maintained within an optimal operating range of 70 to 100 degrees F. Additionally, the sensor analog output signal and the controller device analog output signal can also interface with a pump [802] that pumps the liquid through the liquid flow closed loop.