WO2016154074A1

WO2016154074A1 - Hybrid photovoltaic solar collector

Info

Publication number: WO2016154074A1
Application number: PCT/US2016/023319
Authority: WO
Inventors: Melanie C. RYAN
Original assignee: Syenergy Integrated Energy Solutions Inc.
Priority date: 2015-03-20
Filing date: 2016-03-19
Publication date: 2016-09-29

Abstract

A method of fabricating a photovoltaic and air heating system for use with a system for receiving electrical energy, a mechanism for flowing air, and a system for receiving heated air includes providing an assembly including a first air permeable photovoltaic module and a first backing wall, said first air permeable photovoltaic module includes a first end and a second end. Said first air permeable photovoltaic module lies substantially flat against said first backing wall. Said first air permeable photovoltaic module includes photovoltaic cells. Th method further includes transporting said assembly to a site for installation. At said site for installation the method includes orienting said first air permeable photovoltaic module with respect to said first backing wall at said first end to provide a first plenum for air flow there between. Said providing said first plenum forms a first photovoltaic and air heating segment. The method further includes electrically connecting said first photovoltaic module to the system for receiving electrical energy. The method further includes connecting said first photovoltaic and air heating segment to the mechanism for flowing air for pulling external air through said air permeable photovoltaic module into said plenum and from said plenum to the system for receiving heated air.

Description

HYBRID PHOTOVOLTAIC SOLAR COLLECTOR

Field

This patent application generally relates to an air cooled photovoltaic collector system. More particularly it relates to a transpired air cooled photovoltaic collector system. Even more particularly, it relates to a transpired air cooled photovoltaic collector system that is integrated with a building's heating, ventilation, and/or air conditioning system as well as its electrical system.

Background

As photovoltaic cells heat up, their efficiency decreases. Some designs, such as disclosed in patent application US2011/0155214 have been developed with heat sinks. Others, such as disclosed in patent application US2015/0020866A1 use a heat transfer fluid as a coolant to remove heat from the PV cell. Others, such as U.S. patent 7,982,126 includes perforations substantially entirely through the module which form a ventilation mechanism and provides improved thermal properties.

However, further improvement is needed, and this improvement is provided by the present patent application.

Summary

One aspect of the present patent application is a method of fabricating a photovoltaic and air heating system for use with a system for receiving electrical energy, a mechanism for flowing air, and a system for receiving heated air. The method includes providing an assembly including a first air permeable photovoltaic module and a first backing wall in which the first air permeable photovoltaic module includes a first end and a second end and in which the first air permeable photovoltaic module lies substantially flat against the first backing wall. The first air permeable photovoltaic module includes photovoltaic cells. The method further includes transporting the assembly to a site for installation. At the site for installation the method includes orienting the first air permeable photovoltaic module with respect to the first backing wall at the first end to provide a first plenum for air flow there between. Providing the first plenum forms a first photovoltaic and air heating segment. The method further includes electrically connecting the first photovoltaic module to the system for receiving electrical energy. The method further includes connecting the first photovoltaic and air heating segment to the mechanism for flowing air for pulling external air through the air permeable photovoltaic module into the plenum and from the plenum to the system for receiving heated air. Another aspect of the present patent application is a photovoltaic and air heating system for use with a mechanism for flowing air. The system includes a first photovoltaic and air heating segment. The first photovoltaic and air heating segment includes a first air permeable photovoltaic module, a first backing wall, and a first plenum there between. The first air permeable photovoltaic module has a photovoltaic module first end and a photovoltaic module second end. The photovoltaic module first end is connected to the first backing wall at a first angle and with a gap there between for draining water. An axial direction extends parallel to the photovoltaic module first end. When the mechanism for flowing air is duct-connected to the first plenum for withdrawing air from the first plenum, air is pulled into the first plenum through the first air permeable photovoltaic module. Distance between the first air permeable photovoltaic module and the first backing wall defines a first plenum depth. The first plenum depth is sufficient under most of the first photovoltaic module so air entering the first plenum through most of the first air permeable photovoltaic module is pulled primarily in the axial direction.

Brief Description of the Drawings

The foregoing will be apparent from the following detailed description as illustrated in the accompanying drawings, for clarity not drawn to scale, in which:

FIG. la is a three dimensional view of one embodiment of a photovoltaic and air heating system of the present patent application including an air permeable photovoltaic module including an array of photovoltaic cells mounted to a curved air-permeable support sheet, a backing wall, and a plenum there between, in which the curved air-permeable sheet with its photovoltaic array is mounted to a backing wall that is supported by a support system;

FIG. lb is an enlarged view of one embodiment an air permeable photovoltaic cell of the photovoltaic and air heating system FIG. la showing air-cooling-through holes that extend through the photovoltaic cell and the air-permeable support sheet it is mounted on that allow air to flow through the photovoltaic cell and air-permeable support sheet and enter the plenum located between the air-permeable support sheet and the backing wall; FIG. lc is an enlarged view of a cross section of a perforated photovoltaic cell of the photovoltaic and air heating system of FIGS, la, lb showing the direction of flow of air along the surface of each perforated photovoltaic cell, then through the perforations and then into and within the plenum;

FIG. Id is another three dimensional view of the photovoltaic module of FIGS, la-lc, showing its connection to the backing wall;

FIG. le is an enlarged view of a portion of FIG. Id showing the connection of the photovoltaic module to the backing wall with a fastener and spacers that provide space for water that may enter the plenum to drain out by gravity;

FIG. 2a is a three dimensional view of the portion of the photovoltaic and air heating system of FIG. la including the photovoltaic module and backing wall, all stacked in a fiat position;

FIG. 2b is an enlarged three dimensional view of the portion of the photovoltaic and air heating system of FIG. 2a;

FIG. 3 is an enlarged three dimensional view of a portion of the photovoltaic and air heating system of FIG. la showing how retaining brackets are used to facilitate providing the curve in the

photovoltaic module;

FIG. 4a is a three dimensional view of components of the photovoltaic and air heating system of FIG. la in a fiat stacked position for transport;

FIG. 4b is a three dimensional view of the photovoltaic and air heating system of FIG. 4a as partially assembled on the support system, with the photovoltaic module tilted at angle φ but still in a flat position just before being bent into its curved position;

FIG. 5 is a three dimensional view showing photovoltaic and air heating systems of FIG. la mounted on the roof of a building, an air handling unit (AHU) that has a primary fan and that is connected to air ducts within the building, connecting ducts, a secondary fan, and an electrical system that includes a bank of batteries or an inverter, in which the connecting ducts extend from the photovoltaic and air heating systems to the air handler unit and to the secondary fan and in which wires connect the photovoltaic array to the batteries or the inverter;

FIG. 6a is a schematic diagram showing one embodiment of the connection of the ducts of FIG. 5 to the air handler unit and the secondary fan, in which the air handler unit includes louvers for directing the flow of air showing a mode of system operation in which the primary fan in the air handling unit is drawing air through the photovoltaic modules into the plenum and through the ducts, and this heated air is being sent to the building via the air handler unit while return air from the building is vented to atmosphere;

FIG. 6b is a schematic diagram showing another embodiment of the system of FIG. 6a showing a mode of system operation in which the secondary fan is drawing air through the photovoltaic modules into the plenum and through the ducts, and this heated air is being vented externally while the air handler unit draws external air for distribution in the building while return air from the building is vented externally;

FIG. 6c is a schematic diagram showing a third mode of the system of FIG. 6a showing a mode of system operation in which heated air returned from the building is directed through the ducts to the photovoltaic modules of FIG. la to melt any ice or snow which may have accumulated on their surface;

FIG. 7a is a cross sectional view normal to an axis of the plenum showing an embodiment of the photovoltaic and air heating system of FIG. la in which the support system is omitted and remaining portions of the photovoltaic and air heating system are mounting on an inclined surface, such as an included roof;

FIG. 7b is a cross sectional view normal to an axis of the plenum showing an embodiment of the photovoltaic and air heating system of FIG. la in which a duct extends through the backing wall for drawing heated air out of the plenum for use in a space or by a device that uses the heated air and with a reflector for shining light onto the photovoltaic module that would otherwise not strike the absorber;

FIG. 7c is a cross sectional view normal to an axis of the plenum showing an embodiment of the photovoltaic and air heating system of FIG. la in which the support system is omitted and remaining portions of the photovoltaic and air heating system are mounted on a horizontal surface, such as a flat roof;

FIG. 7d is a cross sectional view normal to an axis of the plenum showing an embodiment of the photovoltaic and air heating system which uses a flat absorber and fiat insulated backing walls which are mounted on a horizontal surface, such as a flat roof;

FIG. 8a is a schematic diagram of the process used to control the solar collector operating parameters to continuously adapt to changing wind condition ensuring optimal electrical, thermal and overall efficiency;

FIG. 8b is a schematic diagram of the process used to control the solar collector operating parameters to rapidly diagnose any possible conditions where all or part of the photovoltaic module are covered in snow and/or ice, and use hot air from building or process to melt ice on the surface of the absorber;

FIGS. 9a and 9b show embodiments for using the heated air with a heat pump.

FIG. 10 is an illustration of the orientation of a curved convex collector relative to the sun;

FIG. 11a shows an embodiment of FIG. la in which air-cooling-through holes are located in spaces between the photovoltaic cells;

FIG. 1 lb shows an enlarged top view of a portion of FIG. 11a illustrating air-cooling-through holes located in spaces between the photovoltaic cells; FIG. 12 is a three dimensional view of a convex photovoltaic and air heating system with a transparent convex glazing cover spaced from the photovoltaic array with spacers to provide greenhouse heating of the air; and

FIG. 13 is a three dimensional view of an alternate embodiment of the system of FIG. 12 in which the transparent glazing cover includes glazing cover holes and in which greenhouse heated air is pulled through air-cooling-through holes or larger through holes located in the support sheet between photovoltaic cells;

Detailed Description

The present patent application includes a system that provides both electrical and thermal energy while providing for easy installation on a building. Embodiments of the system provide components that are mostly factory assembled, easy to transport, and easy to work with in constrained spaces, such as rooftops, where heavy equipment access may be limited.

In one embodiment, photovoltaic and air heating system 20 includes a plurality of photovoltaic and air heating segments 19 that each include photovoltaic modules 26, plenum 21, and backing wall 24, as shown in FIGS, la- Id. Photovoltaic modules 26 each include array 22 of interconnected photovoltaic cells 23 or interconnected panels (not shown) that contain a sub-array of

interconnected photovoltaic cells 23. In one embodiment array 22 of interconnected photovoltaic cells 23 or interconnected panels are formed on or mounted on air-permeable support sheet 25, together forming air-permeable photovoltaic solar absorbing module 26 that covers plenum 21. In one embodiment, air-cooling-through holes 27 are distributed across surface 28 of array 22 of photovoltaic cells and support sheet 25 and extend through both to provide the air-permeability, as shown in FIG. lb. The distribution of air-cooling-through holes 27 along surface 28 transports a boundary layer of solar heated air in contact with top surface 28 of photovoltaic cell array 22 into plenum 21, as shown in FIG. lc.

A mechanism for flowing this air, such as primary fan 36 of FIG. 5, facilitates drawing the solar heated air through air-cooling-through holes 27 into plenum 21 which lies between air-permeable photovoltaic solar absorbing modules 26 and impermeable backing wall 24. Instead of fan 36 other mechanisms for flowing air can be used, such as a set of pneumatic bellows or diaphragms.

In one embodiment, once drawn into plenum 21 , air flows along axial direction A-A down the length of plenum 21 towards fan 36. As shown in FIG. la, axial direction A-A is parallel to edge 38 where impermeable backing wall 24 meets air-permeable support sheet 25 of air-permeable photovoltaic solar module 26. In one embodiment, rows of series connected photovoltaic cells 23 extending along axial direction A-A while columns of photovoltaic cells 23 extending

perpendicular to axial direction A-A are electrically connected in parallel.

Although illustrated in FIG. la with a convex shape, air-permeable photovoltaic solar absorbing modules 26 can instead be flat. In the case of fiat air-permeable photovoltaic solar absorbing modules 26' at least one additional backing wall 24' may be included to form plenum 21 ' as shown in FIG. 7d.

In one embodiment, each convex air-permeable photovoltaic solar absorbing module 26 has a length of 8 to 10 feet (2.44 to 3.05 m) in the axial direction, while its width when fiat is 4 to 6 feet (1.22 to 1.83 m). Other dimensions can be equally well be used.

In one embodiment, panels, such as the 72 Watt thin film solar cell panel with serial number SN- PVLS11-72 available from Sinol Tech, Jinan City, China, are mounted to air-permeable support sheet 25. Each of these panels includes a single row of 11 series-connected thin film photovoltaic cells. A full description of these panels may be found in the data sheet at at this url:

smoltech om/upIoad ile/downioad^O 15161556212803 ,pdf. Open circuit voltage in full sunlight is 24.2 Volts and short circuit current is 5.1 Amps. Length of each panel is 107.9 inches (2.741 m) and width is 14.9 inches (0.378 m). Advantageously SN-PVLSl 1-72 panels are flexible and need no glass cover, as described in the data sheet. After mounting the SN-PVLSl 1-72 panels on support sheet 25, perforating support sheet 25 and connecting one edge of air-permeable support sheet 25 to air-impermeable backing wall 24, air-permeable photovoltaic solar module 26 is then transported to a site for installation where it is pushed into a convex shape, as more fully described for a non- photovoltaic thermal solar absorber in commonly owned United States Patent 9,206,997, incorporated herein by reference.

Wiring from the SN-PVLSl 1-72 panels and air-permeable photovoltaic solar absorbing modules 26 connects through a junction box (not shown) to a set of batteries 39 that can store the electrical energy and/or is connected to the local electrical grid through an electrical inverter that converts direct current to alternating current.

In one embodiment, array of air-cooling-through holes 27 is formed through each of the SN- PVLS11-72 solar panels mounted to air-permeable support sheet 25, including through solar cells of the panels. Air-cooling-through holes 27 are formed through photovoltaic cells 23 and through permeable sheet 25 to which they are mounted by a process such as drilling, punching, laser cutting or water jet perforating.

In another embodiment photovoltaic cells 23 are specially sized to have a width dimension equal to or less than 1.5 inch (38 mm), and air-cooling-through holes 27 are located in air-permeable support sheet 25 in the spaces between photovoltaic cells 23, as shown in FIG. 11 detail. Thus, in this embodiment, photovoltaic cells 23 are free of air-cooling-through holes 27. Air-cooling- through holes 27 are spaced a bit more than the 1.5 inch (38 mm) cell dimension apart and range from 1/32 inch (0.8 mm) to 1/16 inch (1.6 mm) in diameter to provide permeable photovoltaic solar absorbing module 26 with porosity in the range from 0.5% to 2%. In this embodiment photovoltaic cells 23 may be mounted to support sheet after air-cooling-through holes 27 have been formed. Air-cooling-through holes 27 may be of any shape, such as round or rectangular.

In embodiments in which air-cooling-through holes 27 extend through photovoltaic cells 23 or in embodiments in which air-cooling-through holes 27 just extend between photovoltaic cells 23, air- cooling-through holes 27 may be spaced about ¾ inch (19 mm) apart and range from 1/32 inch (0.8 mm) to 1/2 inch (13 mm) in diameter to provide permeable photovoltaic solar absorbing module 26 with porosity in the range from 0.5% to 2%. Higher or lower porosity can also be used. For example, porosity can range up to about 6%. In one embodiment air-cooling-through holes 27 were 1/16 inch (1.6 mm) in diameter on 9/16 inch (14 mm) centers in a square pattern. Photovoltaic array 22 can also be perforated with slots. In embodiments in which air-cooling-through holes 27 are exclusively between photovoltaic cells 23, punched loops can be used, as typically provided in housing soffits that include pressed dimples in a sheet that make slitted holes on the sides of each dimple.

In one embodiment illustrated in FIGS. 1 la, 1 lb, air-permeable photovoltaic solar absorbing module 26 may have a band free of photovoltaic cells 23 around its four edges allowing for connection of photovoltaic and air heating segments 19 to each other and allowing for connection of backing wall 24 to air-permeable support sheet 25.

Sunlight intensity varies with level on convex air-permeable photovoltaic solar absorbing module 26, as shown in FIG. 10. When the sun is normal to the center of convex air-permeable

photovoltaic solar absorbing module 26 in FIG. la, rows extending along axial direction A-A perpendicular to the sun receive more intense sunlight than rows higher up or lower down on convex air-permeable photovoltaic solar absorbing module 26. For example, when the sun is normal to center row 37a of convex air-permeable photovoltaic solar absorbing module 26, the angle of incidence of the sun to highest row 37b and lowest row 37c may be approximately 30 , and the intensity of light at those locations will be cos 30 or 0.87 times the intensity at the center of module 26.

In another example, as shown in FIG. 10, the sun is positioned towards the southwest in the late afternoon at the summer solstice in the northern hemisphere, upper rows of cells 23 extending along axial direction A-A of air-permeable photovoltaic solar absorbing module 26 will be close to normal to rays of sunlight while lower rows will be in the shade, and therefore will not be able to capture any direct solar radiation. Photovoltaic cells 23 connected in series along axial direction A- A, and all cells 23 in each row receive about the same amount of insolation while perpendicular to the axial direction, rows of arrays 22 of photovoltaic cells 23 are connected in parallel. The parallel connected cells allow paths for electrical current around a temporarily shaded photovoltaic cell 23 in one of the rows, minimizing electrical losses in the shaded cell. In one embodiment illustrated in FIG. 7d, photovoltaic and air heating segments 19 each include arrays 22' of interconnected photovoltaic cells 23', or panels that include sub-arrays of

interconnected photovoltaic cells, are mounted on more rigid fiat air-permeable support sheet 25' and include air- impermeable backing walls 24a' and 24b' with plenum 21 ' there between.

Photovoltaic and air heating segments 19 may be assembled on site for installation from fiat sheets, including arrays 22' of interconnected photovoltaic cells 23' or panels mounted on flat air- permeable support sheet 25' and air-impermeable backing walls 24a' and 24b' that were connected to each other in a factory. Interconnected photovoltaic cells 23' for this flat panel embodiment may be crystalline, polycrystalline, or thin film and may have air permeable glazing, as further described herein below.

As shown in FIG. 5, fan 36 may be a component of a building's air handling unit 40 that may be part of the building's heating, ventilating and air conditioning system. In one embodiment, primary fan 36 is powered using electricity produced by photovoltaic modules 26. Alternatively, primary fan 36 may be powered using another source of electricity, such as the standard electric grid.

Drawing air warmed by photovoltaic array 22 away from top surface 28 of photovoltaic array 22 cools cells 23 of array 22 and improves their efficiency at converting solar radiation into electricity as shown in the data sheet for SN-PVLS11-72 panels. In addition, this warmed air drawn radially through air-cooling-through holes 27 into plenum 21 and pulled toward fan 36 makes heat dissipated from photovoltaic array 22 - that would otherwise be wasted - available for heating building or for other uses, such as air-source heat pumping, crop drying, clothes drying, and sludge drying.

In one embodiment, one or more support legs 50 set the angle of photovoltaic array 22 with the sun to optimize average light incidence.

In one embodiment, precipitation and water vapor that passes through air-cooling-through holes 27 in photovoltaic array 22 into plenum 21 exits plenum 21 through gap 52 at the lowest region of plenum 21, for example, where air-permeable support sheet 25 meets backing wall 24 at acute angle Θ, as shown in FIG. le. Advantageously, the flow of air along top surface 28 and through air-cooling-through holes 27 of photovoltaic array 22 also provides for drying out any precipitation that lands on top surface 28 of photovoltaic array 22 or that penetrates into plenum 21 after such precipitation ceases or after conditions that allow condensation to form on top surface 28 or within plenum 21 abate.

In one embodiment, air flow provided by fan 36 is automatically adjusted in response to changes in wind speed, as measured by anemometer 174, which provides an analog input to programmable controller 56 which in turn calculates a corresponding fan 36 speed set point and sends a signal to series drive 58. Programmable controller, such as Allen-Bradley brand MicroLogix 1100 controllers manufactured by Rockwell Automation, Milwaukee, Wisconsin or an industrial computer using a serial communication protocol such as MODBUS, and series drive 58, such as the A1000 series drive manufactured by Yaskawa Electric Corporation, Waukegan, IL or the ACS550 series drive manufactured by ABB, Zurich Switzerland.

While in calm conditions, air flow through photovoltaic array 22 into plenum 21 and axially along plenum 21 is selected for optimal cooling of photovoltaic array 22, as wind speed over top surface 28 of photovoltaic array 22 increases, programmable controller 56 directs fan 36 to increase air flow to maintain the pressure difference and the flow through air-cooling-through holes 27 into plenum 21. Thus reverse flow of air is avoided, in which air within plenum 21 is sucked out of plenum 21 through air-cooling-through holes 27 because of the reduction in external pressure caused by wind blowing across photovoltaic array 22. If wind speed becomes too high for fan 36, and it is no longer possible to overcome the reverse flow effect by increasing fan speed, programmable controller 56 sends a signal to cause fan 36 to stop. While the boundary layer cooling of photovoltaic array 22 fan 36 provides is no longer functioning, fortunately, the high wind itself provides for convective cooling of photovoltaic array 22, so the photovoltaic cells 23 continue to operate at high efficiency notwithstanding the absence of transpired cooling during high wind conditions.

Another aspect of the present patent application is a method of fabricating photovoltaic and air heating system 20. The method includes providing assembly 60 including backing wall 24 and photovoltaic module 26, in which photovoltaic module 26 is substantially flat against backing wall 24. Next, transporting assembly 60 of photovoltaic module 26 fiat against backing wall 24 to a site for installation. At the site for installation, providing photovoltaic module 26 with a curved shape to provide plenum 21 between photovoltaic module 26 and backing wall 24. In this embodiment, when flat, photovoltaic module 26 has a larger width than backing wall 24 so their widths match when photovoltaic module 26 is curved into its convex shape.

Air-impermeable backing wall 24 has a smooth inner surface to facilitate flow of air within plenum 21, and facilitate elimination of water that makes its way into plenum 21, as described herein above. Backing wall 24 may include insulation to retain heat within plenum 21. In one embodiment impermeable backing wall 24 has a highly reflective inner surface to help retain heat as well.

In one embodiment, top end 126 of air-permeable support sheet 25 is connected to top edge 127 of backing wall 24 with one or more fasteners, such as continuous hinge 128. The convex curved shape 129 of air-permeable support sheet 25, as viewed from outside the plenum along a plane perpendicular to an axis of the plenum, is formed from flat air-permeable support sheet 25' shown in FIGS. 2a, 2b. Bottom end 130 of flat air-permeable support sheet 25' is pushed toward continuous hinge 128, causing air-permeable support sheet 25 to bend into curved shape 129, as shown in FIGS, la, Id. In one trial backing wall 24 was 49.5 inches (126 cm) wide and air- permeable support sheet 25 was bent to provide a maximum depth of plenum 21 at 17.5 inches (44 cm). In another trial a shorter air-permeable support sheet 25 was used, and the maximum depth of plenum 21 was 11 inches (28 cm) and in another the maximum depth was 10 inches (25 cm). In an alternative embodiment, the hinges are installed along bottom end 130 of air-permeable support sheet 25. Air-permeable support sheet 25 is pushed from the top end to form curved shape 129 and connected to top edge 127 of backing wall 24. With convex curved shape 129 the cross section perpendicular to the axial direction has substantial area between air-permeable support sheet 25 and planar backing surface 24.

Solar cells may each include an antirefiective coating, as known in the art, to reduce reflection and to increase electricity and heat production. In one embodiment, photovoltaic and air heating system 20 includes glazed cover 131a supported by glazed cover spacers 131b, as shown in FIG. 12. Air entering between glazed cover 131a and photovoltaic cells 23 along top and bottom edges and ends of glazed cover 131a is greenhouse heated between glazed cover 131a and photovoltaic module 26. The heated air is pulled through photovoltaic module 26 into plenum 21 via air-cooling-through holes 27 or through larger holes 27' by fan 36. Larger holes 27' suitable for such greenhouse heated air may have dimensions such as 6 inches by 18 inches. Alternatively glazed cover may be perforated with its own holes to allow air to pass through glazed cover 131a' rather than along its four edges, as shown in FIG. 13. Glazed cover 131a may be made of a transparent material such as polycarbonate or glass which may be curved according to the curvature of photovoltaic module 26.

Bottom end 160 of photovoltaic module 26 may be temporarily held with absorber retaining brackets 136 to retain curved shape 129 while fasteners, such as screws or bolts 138, are used to set bottom end 160 permanently in place against bottom edge 140 of backing wall 24, as shown in FIGS. 2b and 3. Retaining brackets 136 can be left in place after fasteners are installed. The amount of curvature of air-permeable support sheet 25 is determined by the distance bottom end 160 is pushed toward continuous hinge 128 before it reaches bottom edge 140 of backing wall 24. Thus, in this embodiment, the width dimension of backing wall 24 determines the curvature of air- permeable support sheet 25. Air-permeable support sheet 25 has a thickness in the range from .25mm to 1mm. It can also have a thickness greater than 1mm. In one embodiment steel structural sheet is used to fabricate perforated sheet with a thickness of 18 mils or .45mm. A material such as perforated plastic can be used, for example, polyethylene plate. A black or dark colored sheet improves thermal absorption in the spaces between photovoltaic cells and may better capture any light penetrating through photovoltaic cells.

In one embodiment, backing wall 24 is mounted on collector legs 142, as shown in FIGS. Id, 2a, 2b with fasteners (not shown). Bottom ends 143 of collector legs 142 are connected to base 144 with pins or hinges 145 that extend through clearance holes 146, as shown in FIGS, la, Id and in FIGS. 4a, 4b, so collector legs 142 may be easily elevated from the flat position against base 144 shown in FIG. 4a to the tilted position at angle φ shown in FIGS, la, Id and FIG. 4b. Bottom ends 147 of support legs 148 are connected to base 144 with pins or hinges 149 and are raised to support collector legs 142 at the desired tilt angle φ. Top ends of support legs 148 are connected to collector legs 142 with pins or hinges 153. Base 144 may be mounted to a support surface, such as the roof of a building or the ground.

In one embodiment, locking leg 152 is used, as shown in FIG. 4b. In one embodiment locking leg 152 has pin hinge 145 connecting it to base 144. Locking leg also has pin hinge 153 where it contacts collector leg 142. Locking leg 152 also has two leg segments, 152a, 152b with hinge 154 there between. When photovoltaic and air heating system 20 is elevated and locking leg 152 is fully extended, a leg locking device locks hinge 154 so leg segments 152a and 152b extend in a straight line in a fixed position. In one embodiment support legs 148 and one of the locking leg segments 152a or 152b have telescoping sections so angle φ can be adjusted seasonally to improve collector orientation. Locking leg 152 allows photovoltaic and air heating system 20 to be easily elevated from the fiat position against base 144 shown in FIG. 4a to the tilted position at angle Φ shown in FIGS. 2a, 2b and FIG. 4b. Once in this position the locking leg 152 is locked into place with a leg locking device (not shown).

In each embodiment support legs 148, 152 are dimensioned to optimize the average light incidence angle Θ with respect to the absorber for the latitude of the installation.

Two or more photovoltaic and air heating segments 19 may be connected together to form a longer row, as shown in FIGS, la, 5. Row end cap 104 may be used at the end of a single photovoltaic and air heating segments 19 or at the end of a row of photovoltaic and air heating segments 19 to retain heated air within air plenum 21 , prevent cooler outside air from getting in through other than through air-permeable support sheet 25 and provide stiffness to air-permeable support sheet 25 in either or both radial and axial directions. Row end cap 104 can be a plate that completely covers this end of air-permeable support sheet 25. This plate can be fabricated of an impermeable material, such as metal, wood, or plastic and can be insulated with foam insulation, air gap, and reflective inner surface to prevent heat loss. In one embodiment the plate is thick enough to both provide structural support and block flow of air into the duct from this end, so air only comes in to air plenum 21 through air-permeable support sheet 25, where the air has been heated by the sun. Both ends can have this row end cap 104 if air is removed from an intermediate portion of the row through backing wall 24.

In another embodiment, photovoltaic and air heating system 20 is directly mounted on a support surface such as angled roof 122, as shown in FIG. 7a, thus eliminating the need for legs and hinges. Angled roof 122 can also take the place of backing wall 24 providing the impermeable insulated backing surface. In this embodiment, angled roof 122 defines a boundary of plenum 21 along with photovoltaic module 26. Photovoltaic and air heating system 20 of FIG. 7a can also be directly mounted to a horizontal surface, such as a fiat roof or the ground, as shown in FIG. 7c.

In one embodiment air outlet box 124 is connected to a penetration through impermeable backing wall 24 for air outlet from plenum 21, as shown in FIG. 7b. In another embodiment air outlet box 124 is connected to hole 108 in rigid end cap 106 at the end of solar air heating unit 18 or at the end of a row of connected photovoltaic and air heating segments 19, as shown in FIGS. 7a-7c. Air outlet box 124 can have any shape, such as circular or rectangular.

One or more rows of photovoltaic and air heating system 20 can be installed for preheating fresh air immediately upstream of air handler unit 40, all mounted on roof 132a of building 132b, as shown in FIG. 5. An air handler unit 40, such as "Solution" packaged air handlers or "Commercial Comfort Systems" (CCS) Series 5, Series 10, Series 20, Series 40, Series 100 manufactured by Johnson Controls, Milwaukee, Wisconsin, may already be installed on the building. It may include a natural gas burner or another source of heat to heat the incoming air in order to maintain acceptable comfort levels within the building. The use of rows of photovoltaic and air heating system 20 provides solar preheating of that incoming air. Fan 36 in air handler unit 40 draws air from rows of photovoltaic and air heating system 20 to air handler unit 40 through transfer duct system 134. Photovoltaic and air heating system 20 is expected to reduce the consumption of natural gas to preheat incoming air by 20-60%. The amount of natural gas displacement potential is generally a function of climate variables such as insolation (amount of solar radiation available), daytime and nighttime ambient temperature, and building demand. Bypass louvers 133, such as the 700 through 1900 series manufactured by Activar Inc.

( '_*'. Ά \ ,;-cn - a:n¾ u >nQ are generally supplied in transfer duct system 134 so that air entering air handler unit 40 can be drawn directly into building 132b without passing through and being heated in photovoltaic and air heating system 20 in the warm season when building 132b does not require space heating.

In one operating configuration, shown in FIG. 6a, bypass louvers 133 are closed and diverter gate 139 is positioned to direct the flow of air from air-cooling-through holes 27 in photovoltaic panel 26 through ducts 134 towards primary fan 36 and air handling unit 40 and then to building 132b, while return air from the building 132b is vented via louvers 141 to atmosphere.

In another operating configuration for use when thermostats in building 132b do not call for heat, louvers 133' and 141 are opened while diverter gate 139' is positioned as shown in FIG. 6b to direct unheated ambient air toward primary fan 36 while secondary fan 129 is drawing heated air from air-cooling-through holes 27 in photovoltaic array 21 to plenum 21, through ducts 134 for venting externally. In addition to drawing external air through bypass louvers 133' for distribution in building 132 air handler unit 40 also vents return air from building 132 through louvers 141 to the outdoors. In one embodiment, secondary fan 129 can be operated using electricity provided by the photovoltaic array driven by a DC motor.

In a third operating configuration, to address snow or ice on photovoltaic and air heating system 20, louvers 133' are open while louvers 141 are closed, and secondary fan 129 is off, as shown in FIG. 6c, to provide heated air from building 132b through ducts 134 to plenum 21 of photovoltaic and air heating system 20 where the heated air will melt ice or snow which may have accumulated on surfaces of air-permeable support sheet 25 and array 22 of interconnected photovoltaic cells 23.

In addition to heating air for direct space heating or for further heating in an air handling unit for building space heating as well as for providing electricity, photovoltaic and air heating system 20 can also be used for both providing electricity and for preheating process air that may be further heated in an industrial application, such as for use in an industrial oven or for combustion air.

Photovoltaic and air heating system 20 can also be used for direct application of the heated air for other heating applications, such as crop drying. In one embodiment, air heated in photovoltaic and air heating system 20 is provided to air-source heat pump such as air-to-liquid heat pump 135b, as shown in FIG. 9a, such as Waterstage Series Model WOYK 160 LC, by Fujitsu General Ltd., Kawasaki, Japan

lvllp:/Viup^'tsu-gei era.l.de/heat-pumps/watersta

-woyk- 16Q-lc.html or air-to-air heat pump 135a, as shown in FIG. 9b, such as Infinity 20 series heat pump, model 25VNA0, by Carrier, a United Technologies Company, Syracuse, NY, USA http://vvwvv .carrier, com/homeconifort/en/m

Continuous control over fan 36 in air handler unit 40 allows photovoltaic and air heating system 20 to continuously adapt to changing wind conditions, as shown in the flow chart of FIG. 8a. A program running on programmable controller 56 receives input from building thermostat 172 to determine whether or not building or process heat is needed, as shown in decision diamond 200.

If so, the program running on programmable controller 56 then receives input from anemometer 174 to determine a setting for primary fan 36 in air handler unit 40, as shown in analog wind level block 201, with corresponding low, moderate and high wind levels, and analog wind level block 202, with corresponding low/medium and high wind levels.

First, programmable controller 56 determines whether wind speed from anemometer 174 is less than approximately 10 km/h (low), as shown in analog wind level decision block 201. If so, programmable controller 56 sends a signal to turn on air handler unit fan 36 and to turn on motors (not shown) controlling louvers to provide settings as shown in FIG. 8a.

If wind speed from anemometer 174 is between approximately 10 and 25 km/h (moderate), programmable controller 56 sends a signal to increase speed of air handler unit fan 36 to increase air flow in proportion to wind speed, thus ensuring that air is pulled into plenum 21 through air- cooling-through holes 27. If wind speed is higher than approximately 25 km/h, programmable controller 56 sends a signal to motors that open louvers 133 ' to draw outside air directly into building 132 bypassing photovoltaic and air heating system 20.

If building or process heat is not needed, as shown in decision diamond 200, and if the program running on programmable controller 56 receives data from anemometer 174 showing that wind speed is below approximately 25 km/h, programmable controller 56 sends a signal to a switch that turns on secondary fan 129 to vent heated air collected in plenum 21 to atmosphere, while still drawing external air across surfaces of photovoltaic cells 23 through air-cooling-through holes 27 to cool photovoltaic cells 23. Programmable controller 56 may also send a signal to motors controlling louvers 133 and 141 and diverter 139 to position them as provided in FIG. 6a. If wind speed is greater than approximately 25 km/h, programmable controller 56 sends a signal to the switch of secondary fan 129, stopping secondary fan 129, as the wind will sufficiently cool photovoltaic cells 23.

Programmable contro Her 56 includes a program to periodically receive data from thermocouple 180 showing whether ambient temperature is below freezing, as shown in decision box 203 and from pair of thermocouples 182a, 182b in different locations on surface of photovoltaic and air heating system 20 showing whether a temperature difference of more than IO C exists between these locations, as shown in box 204. Such a temperature difference may indicate the presence of snow or ice on photovoltaic and air heating system 20. If so, the program running on programmable controller 56 sends a signal to the motors to set louvers 133', 14 V and diverter 139' as shown in FIG. 6c so air handler unit 40 provides warm building air to photovoltaic and air heating system 20, as shown in FIG. 8b. In one embodiment, the program running on programmable controller 56 maintains this configuration for a set time, such as 15 minutes, to melt any ice or snow which may have accumulated.

While the disclosed methods and systems have been shown and described in connection with illustrated embodiments, various changes may be made therein without departing from the spirit and scope of the invention as defined in the appended claims.

Claims

1. A method of fabricating a photovoltaic and air heating system for use with a system for

receiving electrical energy, a mechanism for flowing air, and a system for receiving heated air, comprising: a. providing an assembly including a first air permeable photovoltaic module and a first backing wall, wherein said first air permeable photovoltaic module includes a first end and a second end, wherein said first air permeable photovoltaic module lies substantially fiat against said first backing wall, wherein said first air permeable photovoltaic module includes photovoltaic cells; b. transporting said assembly to a site for installation; c. at said site for installation orienting said first air permeable photovoltaic module with

respect to said first backing wall at said first end to provide a first plenum for air flow there between, wherein said providing said first plenum forms a first photovoltaic and air heating segment; d. electrically connecting said first photovoltaic module to the system for receiving electrical energy; and e. connecting said first photovoltaic and air heating segment to the mechanism for flowing air for pulling external air through said air permeable photovoltaic module into said plenum and from said plenum to the system for receiving heated air.

2. A method as recited in claim 1, further comprising providing a retaining bracket, wherein at said site for installation, holding said second end of said first photovoltaic module with said retaining bracket to hold said first photovoltaic module in a convex shape.

3. A method as recited in any of claims 1-2, further comprising providing a first element and a second element, wherein at said site for installation, connecting said second end to said first backing wall with said first element and with said second element, wherein said first element and said second element have a gap there between and are configured for holding said second end so said first photovoltaic module has a convex shape.

4. A method as recited in any of claims 1-3, wherein the mechanism for flowing air provides air flowing in an axial direction in said plenum between said first photovoltaic module and said first backing wall, wherein said axial direction is parallel to said second end, wherein distance between said first photovoltaic module and said first backing wall defines a plenum depth, wherein said plenum depth is sufficient under most of said photovoltaic module so air entering said first plenum through most of said first photovoltaic module is pulled primarily in said axial direction.

5. A method as recited in any of claims 1-4, further comprising connecting a second said

photovoltaic and air heating segment, wherein when connected, first and second photovoltaic modules, backing walls, and plenums of said connected first and second photovoltaic and air heating segments are respectively aligned so air entering said first plenum passes in said axial direction through said second plenum.

6. A method as recited in claim any of claims 1-5, wherein said first photovoltaic module has a rigidity sufficient to provide and maintain a convex shape when supported only along said photovoltaic module first and second ends, further comprising at said site for installation, providing a force to bend said first photovoltaic module into a convex shape, wherein said first photovoltaic module has said convex shape when said first photovoltaic module is viewed from outside said first photovoltaic module.

7. A method as recited in any of claims 1-6, wherein said system for receiving heated air includes an air handling unit and a duct, further comprising connecting said first photovoltaic and air heating segment to said air handling unit through said duct for air flow there between.

8. A method as recited in any of claims 1-7, wherein said first photovoltaic and air heating segment further includes a base, wherein in (b) transporting said first backing wall flat against said base.

9. A method as recited in any of claims 1-8, wherein (c) includes tilting said first backing wall with respect to said base at said site for installation.

10. A method as recited in any of claims 1-9, further comprising a hinge, further comprising

connecting said first photovoltaic module to said first backing wall along said first end with said hinge.

11. A method as recited in claim 10, further comprising connecting said first photovoltaic module to said first backing wall along said first end with said hinge before said transporting (b).

12. A method as recited in claim any of claims 1-11, wherein said first air permeable photovoltaic module includes air-cooling-through holes, wherein said mechanism for flowing air pulls air into said plenum through said air-cooling-through holes.

13. A method as recited in any of claims 1-12, further comprising providing a glazing and

mounting said glazing over said first air permeable photovoltaic module.

14. A method as recited in any of claims 1-13, further comprising providing a second mechanism for flowing air and connecting said second mechanism for flowing air for pulling air from said first photovoltaic and air heating segment for release to an external environment.

15. A method as recited in any of claims 1-14, further comprising automatically directing warm building air to said first plenum for removing snow from said first air permeable photovoltaic module.

16. A method as recited in any of claims 1-15, further comprising providing a reflector to shine sunlight on said first air permeable photovoltaic module that would otherwise not strike said first air permeable photovoltaic module.

17. A method as recited in any of claims 1-16, further comprising providing a heat pump and

connecting said heat pump to said first photovoltaic and air heating segment for receiving heated air.

18. A photovoltaic and air heating system for use with a mechanism for flowing air, comprising a first photovoltaic and air heating segment, wherein said first photovoltaic and air heating segment includes a first air permeable photovoltaic module, a first backing wall, and a first plenum there between, wherein said first air permeable photovoltaic module has a photovoltaic module first end and a photovoltaic module second end, wherein said photovoltaic module first end is connected to said first backing wall at a first angle and with a gap there between for draining water, wherein an axial direction extends parallel to said photovoltaic module first end, wherein when the mechanism for flowing air is duct-connected to said first plenum for withdrawing air from said first plenum, air is pulled into said first plenum through said first air permeable photovoltaic module, wherein distance between said first air permeable photovoltaic module and said first backing wall defines a first plenum depth, wherein said first plenum depth is sufficient under most of said first photovoltaic module so air entering said first plenum through most of said first air permeable photovoltaic module is pulled primarily in said axial direction.

19. A photovoltaic and air heating system as recited in claim 18, wherein said plenum depth varies along a plane perpendicular to said axial direction.

20. A photovoltaic and air heating system as recited in any of claims 18-19, wherein said first

photovoltaic module has a rigidity sufficient to provide and maintain a convex shape when a force to bend said first photovoltaic module into said convex shape is applied and said photovoltaic module second end is connected to said first backing wall, wherein along a cross section of said first photovoltaic module normal to said axial direction said first photovoltaic module has an average shape that is convex when said first photovoltaic module is viewed from outside of said plenum, wherein said convex shape provides said plenum for air flow.

21. A photovoltaic and air heating system as recited in any of claims 18-20 wherein said first

photovoltaic module is hingeably connected to said backing wall.

22. A photovoltaic and air heating system as recited in any of claims 18-21, wherein said first backing wall is impermeable to air.

23. A photovoltaic and air heating system as recited in claim 22, further comprising a second

backing wall, wherein said second backing wall is impermeable to air.

24. A photovoltaic and air heating system as recited in any of claims 18-23, wherein along a plane perpendicular to said axial direction said first plenum has a triangular cross section.

25. A photovoltaic and air heating system as recited in any of claims 18-24, further comprising a second said photovoltaic and air heating segment, wherein said second photovoltaic and air heating segment includes a second photovoltaic module, a second backing wall, and a second plenum, wherein when said first and said second photovoltaic and air heating segments are connected to each other said first and second photovoltaic modules, backing walls and plenums are respectively aligned so when the mechanism for flowing air is duct-connected to said first plenum for withdrawing air, air is also pulled through said second photovoltaic module and into said second plenum and passes in said axial direction through said first plenum.

26. A photovoltaic and air heating system as recited in any of claims 18-25, further comprising a structure having a roof, wherein said first backing wall includes said roof.

27. A photovoltaic and air heating system as recited in any of claims 18-26, further comprising a glazing, wherein said glazing extends over said first photovoltaic module.

28. A photovoltaic and air heating system as recited in claim 27, wherein said glazing is permeable to air.

29. A photovoltaic and air heating system as recited in any of claims 27-28, wherein said glazing is spaced from said first photovoltaic module with an air gap there between for providing greenhouse effect air heating.

30. A photovoltaic and air heating system as recited in any of claims 18-29, wherein said first air permeable photovoltaic module includes air-cooling-through holes, wherein said mechanism for flowing air pulls air into said plenum through said air-cooling-through holes.

31. photovoltaic and air heating system as recited in any of claims 18-30, further comprising a heat pump connected to said first photovoltaic and air heating segment for receiving heated air.