WO2014094072A1

WO2014094072A1 - Photovoltaic device and assembly

Info

Publication number: WO2014094072A1
Application number: PCT/AU2013/001515
Authority: WO
Inventors: Ahmed El SAFTY
Original assignee: C I Corporation Pty Ltd
Priority date: 2012-12-21
Filing date: 2013-12-20
Publication date: 2014-06-26

Abstract

A photovoltaic device including at least one photovoltaic cell and an infrared filter assembly positioned relative to an incident radiation side surface of the photovoltaic cell to allow passage of at least a short wavelength portion of incident radiation whilst at least minimising the passage of longer wavelength portions of incident radiation.

Description

PHOTOVOLTAIC DEVICE AND ASSEMBLY

TECHNICAL FIELD

[0001] The present invention relates to solar power apparatus and particularly to a photovoltaic device of a type that contains a series of laminated layers having a front side exposed to a radiation from a photon radiation source.

BACKGROUND ART

[0002] The concept and function of PV Cell is that it is electrically connected either in series or parallel to other PV Cells to form a PV Panel which in turn is either connected in series or in parallel to form a PV Array for electrical power production. Typically the PV Panels are normally fixed and aligned in the direction of incident primary sunlight rays being the source of the photons. To improve the electrical output of the PV Panels, the PV Panels are mounted to either single axis or dual axis sun tracking devices and to further increase the electrical power output of the PV Panel, a Sunlight Concentrating Device ("SCD") is used to amplify the amount of sunlight that contacts the PV Panel. The collective system is generally known as Concentrated PhotoVoltaic system or CPV system.

[0003] The type of concentrators can vary from reflective devices that are mounted near the PV Panel and can take the shape of a flat panel, reflective parabolic or semi-cylindrical troughs or parabolic dish.

[0004] In particular when using SCDs, the temperature of the semiconductor material in the PV Cell increases and the PV Cell becomes less efficient. This is due to the fact that when the electrons are liberated by the incident photon ray, they partially recombine and therefore reduce the useful outer current flow of the photovoltaic cell.

[0005] Prior art attempts included the attachment of heat-dissipating devices to the rear of the PV Cell in a similar manner to those used in other electrical or electronic components.

Another form of cooling of PV Cells is to attach a heat exchanger to the reverse side of the PV Cell that contains a recirculating coolant that removes the accumulated heat from the PV Cell. Yet another form of removing heat from the PV Cell is to use convective air circulation to the reverse side of the PV Cell. These processes cannot remove heat evenly from the PV Cell and can generally cause Cell and diode failure due to uneven temperature and electricity production profiles within the same cell. [0006] There is therefore a need for a thermodynamically and economically efficient device to overcome the shortfall of the prior art.

[0007] It will be clearly understood that, if a prior art publication is referred to herein, this reference does not constitute an admission that the publication forms part of the common general knowledge in the art in Australia or in any other country.

SUMMARY OF INVENTION

[0008] The present invention is directed to a photovoltaic device, which may at least partially overcome at least one of the abovementioned disadvantages or provide the consumer with a useful or commercial choice.

[0009] With the foregoing in view, the present invention in one form, resides broadly in a photovoltaic device including at least one photovoltaic cell and an infrared filter assembly positioned relative to an incident radiation side surface of the photovoltaic cell to allow passage of at least a short wavelength portion of incident radiation whilst at least minimising the passage of longer wavelength portions of incident radiation.

[0010] According to an alternative aspect, the present invention resides in a photovoltaic assembly including at least one photovoltaic cell, an infrared filter assembly positioned relative to an incident radiation side surface of the photovoltaic cell to allow passage of at least a short wavelength portion of incident radiation whilst at least minimising the passage of longer wavelength portions of incident radiation and at least one incident radiation concentration device to concentrate incident radiation through the infrared filter assembly to the at least one photovoltaic cell.

[0011] The present invention is directed towards providing a mechanism by which the temperature of a PV cell can be lowered. It is particularly preferred that the at least short wavelength portion of incident radiation is near infrared radiation. Therefore, the infrared filter assembly will normally allow near infrared radiation to pass whilst minimising or preventing passage longer wavelengths of radiation.

[0012] PV Cell cooling is generally required when solar concentrators are used to deflect (in the case of mirrored reflectors) or diffract (in the case of Fresnel lens concentrators) solar rays from a larger surface area to a smaller PV Cell surface area so as have the effect of having multiple suns radiating the PV Cell. The cooling is normally required due to the unfavourable thermo-resistive properties of the cells used, which result in increasing efficiency losses with temperature increases. The deflected or diffracted solar rays generally are more intense at the centre of the point of incident and become less intense further from the centre. This causes uneven potential drop within the same PV Cell and eventually can lead to the PV Cell's failure.

[0013] Existing cooling devices are generally mounted on the rear (non-radiated) side of the PV Cell to avoid interference with radiation incident rays. The radiated side and non-radiated side heat exchangers do not maintain an even panel temperature and erratic temperature profiles occur in the PV Panel and individual PV Cells. Uneven cooling systems can reduce the life of the PV Cells due to repeated uneven thermal expansion and contraction which eventually will lead to failure.

[0014] The present invention uses techniques and devices to reduce the amount of infra-red rays contacting the PV Cell which, if allowed, has the effect of heating the PV Cell and reducing its efficiency due to the PV Cells thermo-resistive properties. The techniques used are also designed to maintain a relatively even relatively lower temperature (generally below 30 degrees Celsius) across a PV Panel during operation to ensure optimum efficiency.

[0015] The preferred photovoltaic cell is a type that contains a series of laminated layers having a front side exposed to a radiation from a photon radiation source and protected by a layer of durable photon-transparent plastic or glass for weather protection, a middle section that contains a semiconductor that is capable of converting photons to electricity and a reverse side that contains a weather proof encapsulating layer. Collectively this configuration is known as a Photovoltaic Cell or PV Cell.

[0016] By far, the most prevalent bulk material for solar cells is crystalline silicon

(abbreviated as a group as c-Si), also known as "solar grade silicon". Crystalline silicon (c-Si) has a bandgap of approximately 1.1 eV, which means it absorbs the the infrared portion of the spectrum more strongly than visible part of the solar spectrum.

[0017] The Shockley-Queisser limit for the theoretical maximum efficiency of a solar cell. Semiconductors with band gap between 1 and 1.5eV, or near-infrared light, have the greatest potential to form an efficient cell.

Further, the properties of near-infrared radiation are summarised in the following

[0019] It can therefore be seen that the photon energy of near-infrared radiation corresponds with the bandgap of crystalline silicon the most prevalent bulk material, and with the Shockley- Queisser limit for the theoretical maximum efficiency of a solar cell. Although any type of PV cell can be used, a crystalline silicon based PV cell is preferred.

[0020] The infrared filter assembly of the present invention may have any form. For example, the filter assembly may be provided in the form of a coating to an outer portion of the PV cell or alternatively, tandem PV cell can be provided with one or more secondary layers of silicon of different type to allow use of the remainder of the spectrum of the incident radiation as well as allowing the at least short wavelength portion of the incident radiation to pass to a PV cell.

[0021] According to a most preferred form, the infrared filter assembly is a heat exchanger or vessel through which a fluid can flow to absorb or filter the less preferred portions of the incident radiation.

[0022] It is preferred that the heat exchanger or vessel is a substantially planar, typically three-dimensional rectangular vessel.

[0023] It is preferred that the vessel is substantially the same dimension as the PV cell to which it is applied, normally covering the PV cell.

[0024] The preferred heat exchanger or vessel is mounted relative to the outer face of the PV cell in any manner. For example, the heat exchanger or vessel can be attached directly to the outer surface of the PV cell or alternatively, may be mounted in a configuration which spaces of the inner surface of the heat exchanger or vessel from the outer surface of the PV cell as this may further increase the temperature reduction of the PV cell by preventing or limiting any conductive heat transfer.

[0025] The preferred heat exchanger or vessel will typically be hollow, manufactured from a number of side walls. Further, the preferred heat exchanger or vessel will typically have at least one transparent sidewall. Normally, at least the outer side wall which is substantially parallel to the outer surface of the PV cell will be transparent but other walls, including the inner side wall which is located adjacent the outer surface of the PV cell may also be transparent.

[0026] Any one or more of the walls of the preferred heat exchanger or vessel may be coated in order to filter or collect portions of the incident radiation spectrum.

[0027] Any one or more of the walls of the preferred heat exchanger or vessel may be provided with a coating or surface conditioning which allows photons to pass rather than be reflected outwardly and/or more effectively traps photons within the preferred heat exchanger or vessel.

[0028] It is particularly preferred that a filter coating be applied to at least the inner side wall of the heat exchanger or vessel located adjacent the outer surface of the PV cell.

[0029] Anti-reflective coatings can be applied to create destructive interference within the vessel. This can be done by modulating the Refractive index of the surface coating; if destructive interference is achieved, there will be little or no reflective wave and thus all light will be transmitted into the vessel.

[0030] Surface texturing is another option, but may be less viable because it also increases the manufacturing price. By applying a texture to the surface of the heat exchanger or vessel, the reflected light can be refracted into striking the surface again, thus reducing the overall light reflected out.

[0031] Light trapping as another method allows for a decrease in overall thickness of the heat exchanger or vessel; the path length that the light will travel is several times the actual device thickness. This can be achieved by adding a textured backreflector to the heat exchanger or vessel as well as texturing the surface. If both front and rear surfaces of the heat exchanger or vessel meet this criterion, the light will typically be 'trapped' by not having an immediate pathway out of the heat exchanger or vessel due to internal reflections.

[0032] The particular material used to form the walls of the heat exchanger or vessel may be absorbent to portions of the spectrum except for near infrared.

[0033] As mentioned above, the heat exchanger or vessel will typically be hollow in order to allow a heat transfer medium to flow there through. Preferably, the heat transfer medium chosen will also be absorbent to portions of the spectrum except near infrared allowing the near infrared wavelengths to pass through the heat exchanger and heat exchange medium, to the PV cell.

[0034] Preferably, the heat exchange medium will absorb portions of the spectrum except near infrared which will cause a corresponding increase in the temperature of the heat exchange medium. Normally, this now heat charged heat exchange medium will be removed from the heat exchanger according to normal principles for recovery of the excess heat elsewhere or alternatively, injection of the heat to the environment. It is preferred that the heat is recovered for use. The exchange medium will normally be transparent or at least transmissive to useful portions of the incident radiation.

[0035] There are a variety of mechanisms by which the heat can be recovered. However, the preferred mechanisms for heat recovery include a secondary heat exchanger that can take the form of a space heating device, a water heating device or desalination unit.

[0036] According to a preferred embodiment, a number of transparent baffles, or radiation transparent baffles are also incorporated into the heat exchanger so as to direct the heat exchange medium from a preferably central point of entry outward toward the edges of the heat exchanger. This will typically allow the heat exchange medium to pass over the hottest part of the photovoltaic cell when the medium is at its coolest.

[0037] The transparent baffles can be provided in any orientation but it is preferred that the baffles extend across the shorter dimension of the PV cell.

[0038] Whilst the present invention is particularly directed towards the at least short wavelength portion of incident radiation being near infrared radiation, it is anticipated that the present invention can be easily adjusted to utilise other useful portions of the incident radiation either as as well as near infrared radiation or in the alternative. Therefore, the present invention is not to be limited to an application in which near infrared radiation only is allowed to pass to the PV cell.

[0039] The photovoltaic device as described above can be used in association with radiation concentrators and in one particularly preferred form, will be used in that form. Any type of radiation concentrator or collect that can be used in association with the cooled photovoltaic device described above according to the principles of concentrated solar power.

[0040] Concentrating technologies exist in four common forms, including parabolic trough, dish Stirlings or dish engine systems, concentrating Fresnel reflectors, and solar power towers or heliostats. Any one or more of these concentrating technologies or any other concentrating technology can be used in association with the photovoltaic device described above.

[0041] It is also preferred that the photovoltaic device and any associated concentrating technology be appropriately mounted in order to ensure that the incident radiation strikes the PV cell as efficiently as possible. There are many solar tracking devices including either single axis or dual axis some tracking devices and any one or more of these devices may be used. It is particularly preferred that the tracking or mounting device used be capable of moving the photovoltaic device or assembly as described above into a "safe" or "sleep" position during inclement conditions.

[0042] Probably the most dangerous inclement condition to the device and assembly of the present invention are high winds. Therefore, an elevated wind detection system will preferably be associated with the device or assembly of the present invention in order to detect elevated wind conditions and therefore move the photovoltaic device and assembly into the "safe" or "sleep" position.

[0043] It is particularly preferred that the elevated wind detection system include at least an anemometer and preferably both an anemometer and an excellent barometer in order to detect movement in the photovoltaic device and assembly.

[0044] Typically, the "safe" or "sleep" position will be a position where the photovoltaic device and assembly is substantially coplanar and typically closely spaced to the surface from which it is mounted. This position will typically prevent any unnecessary lifting and/or possible deformation of the mounting assembly by preventing or minimising high wind getting underneath the device or assembly.

[0045] One or more measurement devices may be provided to measure weather conditions and to actuate the movement to the "safe" or "sleep" position and preferably out of the "safe" or "sleep" position back to the operational position. The measurement devices may include an anemometer and/or a hail detector.

[0046] The "safe" or "sleep" position may differ depending upon the increment condition. For example, in high winds, it is preferable to have the assembly in a "lay flat" position parallel to a roof surface or other surface and closely spaced therefrom in order to prevent the wind lifting the assembly. In other conditions, such as for example hail, it may be preferable to have the assembly position the photovoltaic device more or less vertically and preferably, each wise to the direction of the approaching hail.

[0047] Further, in the event that there is a current surge, the device or assembly will preferably turn away from the sun in order to reduce current flow. Other protection devices are already typically already provided in the inverters associated with PV cells and arrays.

[0048] Any of the features described herein can be combined in any combination with any one or more of the other features described herein within the scope of the invention.

[0049] The reference to any prior art in this specification is not, and should not be taken as an acknowledgement or any form of suggestion that the prior art forms part of the common general knowledge.

BRIEF DESCRIPTION OF DRAWINGS

[0050] Various embodiments of the invention will be described with reference to the following drawings, in which:

[0051] Figure 1 is a schematic illustration of the operation of a typical photovoltaic cell.

[0052] Figure 2 is a schematic illustration of a typical Fresnel lens concentrator showing the lines of travel of the incident solar rays.

[0053] Figure 3 is a schematic illustration of the typical layers of a photovoltaic cell.

[0054] Figure 4 is a diagram of a photovoltaic device according to a particularly preferred embodiment of the present invention.

[0055] Figure 5 is a cross-sectional diagram of the photovoltaic device illustrated in Figure 4.

[0056] Figure 6 is axonometric view of a preferred embodiment of the invention with a concentrator positioned relative to the photovoltaic device.

DESCRIPTION OF EMBODIMENTS

[0057] According to the preferred embodiment of the present invention, a temperature controlled photovoltaic device is provided.

[0058] The basic construction and operation of a photovoltaic cell (PV cell) is illustrated in Figure 1. Sunlight is composed of photons 10, or particles of solar energy. Only the absorbed photons generate electricity. When this happens, the energy of the photon is transferred to an electron in an atom of the cell (which is actually a semiconductor). With its newfound energy, the electron is able to escape from its normal position associated with that atom to become part of the current in an electrical circuit. Special electrical properties of the PV cell— a built-in electric field— provide the voltage needed to drive the current through an external load 11 (such as a light bulb). [0059] To induce the electric field within a PV cell, two separate semiconductors are sandwiched together beneath a glass layer 14. The p-type 12 and n-type 13 of semiconductors correspond to "positive" and "negative" because of their abundance of holes or electrons (the extra electrons make an "n" type because an electron actually has a negative charge).

[0060] Although both materials are electrically neutral, n-type silicon has excess electrons and p-type silicon has excess holes. Sandwiching these together creates a p/n junction at their interface, thereby creating an electric field.

[0061] An assembly according to a preferred embodiment is illustrated in Figure 2. In figure 2, a cooled photovoltaic cell 15 is provided beneath a sunlight concentration device which according to Figure 2 is a Fresnel lens 16. The Fresnel lens 16 has the effect of collecting or concentrating sunlight from a larger area and concentrating it toward the cooled photovoltaic cell 15.

[0062] Figure 3 illustrates the typical photovoltaic cell layers. A photovoltaic cell of this general type will preferably be used according to the present invention. The photovoltaic cell illustrated has an outer glass layer 17. Immediately below the outer glass layer 17 is a layer of EVA film 18 provided to allow the outer glass layer 17 to adhere to the photovoltaic layer 19. A second layer of EVA film 20 is provided beneath the photovoltaic layer 19 18 for adhesion purposes. A metal backplate 21 is provided on the other side of the second layer of EVA film 20.

[0063] A cooled photovoltaic cell 15 according to a particularly preferred embodiment of the present invention is illustrated in Figure 4.

[0064] The three-dimensional illustration of Figure 4 shows an infrared filtered, but otherwise solar transparent, heat exchanger adjoined to a typical photovoltaic device 23 which allows the useful and relatively short wavelength portion of the solar ray spectrum to perform the normal photovoltaic duty on the photovoltaic device 23 whilst absorbing a significant proportion of the relatively long infrared wavelength portion of the spectrum.

[0065] A suitably selected (high thermal capacity and infrared absorbing.heat transfer liquid is pumped into the heat exchanger 22 to absorb infrared rays apart from the near infrared portion and remove thermal energy from the radiating side of the photovoltaic device 23.

[0066] The heat transfer liquid is pumped into the centre of the heat exchanger 22 through the inlet conduit 24 and is directed outwards towards the edge of the heat exchanger 22 through a baffled section so as to maintain a relatively even temperature across the photovoltaic device 23 as generally the centre portion of the photovoltaic device 23 is the hottest zone when solar concentrators are used particularly one such as the linear Fresnel lens depicted in Figures 2 and 6.

[0067] As illustrated, the heat exchanger vessel 22 is a substantially planar, three- dimensional rectangular vessel with substantially the same dimension as the PV cell 23 to which it is applied, normally covering the PV cell.

[0068] The illustrated heat exchanger or vessel is attached directly to the outer surface of the PV cell in any manner.

[0069] The preferred heat exchanger vessel 22 is hollow, manufactured from a number of side walls. Normally, at least the outer side wall which is substantially parallel to the outer surface of the PV cell is transparent but other walls, including the inner side wall which is located adjacent the outer surface of the PV cell, may be also transparent.

[0070] The hollow heat exchanger or vessel allows a heat transfer medium to flow there through. The heat transfer medium chosen is absorbent to portions of the spectrum except near infrared allowing the near infrared wavelengths to pass through the heat exchanger 22 and heat exchange medium, to the PV cell 23.

[0071] The heat exchange medium absorbs portions of the spectrum except near infrared which will cause a corresponding increase in the temperature of the heat exchange medium. . Normally, this now heat charged heat exchange medium will be removed from the heat exchanger according to normal principles for recovery of the excess heat elsewhere or alternatively, ejection of the heat to the environment. It is preferred that the heat is recovered for use.

[0072] According to the illustrated embodiment, the number of transparent baffles 25 are also incorporated into the heat exchanger 22 so as to direct the heat exchange medium from a preferably central point of entry outward toward the edges of the heat exchanger. This will typically allow the heat exchange medium to pass over the hottest part of the photovoltaic cell when the medium is at its coolest.

[0073] The transparent baffles can be provided in any orientation but it is preferred that the baffles extend across the shorter dimension of the PV cell. The arrows in Figure 4 indicate the preferred direction of movement of the heat transfer liquid medium in the heat exchanger 22. The cross-sectional diagram in Figure 5 shows the path of the heat transfer liquid and the directional flow of the infrared rays.

[0074] The heat transfer liquid removes thermal energy in 2 ways, through normal convective heat transfer between the boundary of the heat exchanger and the photovoltaic device and by absorbing the relatively long wavelength rays of the solar spectrum generally referred to as infrared rays.

[0075] The heated heat transfer liquid is directed away from the heat exchanger to an independent thermostatically controlled heat exchanging device (not shown) that can be utilised for hot water production, desalination or absorption chilling applications. The cooled heat transfer liquid is pumped back to the heat exchanger attached to the photovoltaic device.

[0076] In typical photovoltaic devices, the long wave infrared rays, which do not have any photovoltaic properties, are absorbed in the material of construction of the heat exchanger and the heat transfer liquid which is then transferred to thermal energy which is removed at a secondary heat exchanger.

[0077] In accordance with the thermodynamic advantages of the present invention it is noted that:

• a photovoltaic device to date was only able to convert solar rays to electric power at an efficiency of approximately 12%;

• This efficiency vastly drops by up to 15% when solar concentrators are used due to the thermo-resistive properties of the photovoltaic device;

• Which can now be used as cogeneration (power and heat) device to make a photovoltaic module which generates electrical power and heat at an overall efficiency of

approximately 60%; and

• The life of the photovoltaic device can now be prolonged due to the lower amount of thermo-mechanical stresses.

[0078] In the present specification and claims (if any), the word 'comprising' and its derivatives including 'comprises' and 'comprise' include each of the stated integers but does not exclude the inclusion of one or more further integers.

[0079] Reference throughout this specification to 'one embodiment' or 'an embodiment' means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearance of the phrases 'in one embodiment' or 'in an embodiment' in various places throughout this specification are not necessarily all referring to the same embodiment.

Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more combinations.

[0080] In compliance with the statute, the invention has been described in language more or less specific to structural or methodical features. It is to be understood that the invention is not limited to specific features shown or described since the means herein described comprises preferred forms of putting the invention into effect. The invention is, therefore, claimed in any of its forms or modifications within the proper scope of the appended claims (if any) appropriately interpreted by those skilled in the art.

Claims

1. A photovoltaic device including at least one photovoltaic cell and an infrared filter assembly positioned relative to an incident radiation side surface of the photovoltaic cell to allow passage of at least a short wavelength portion of incident radiation whilst at least minimising the passage of longer wavelength portions of incident radiation.

2. A photovoltaic assembly including at least one photovoltaic cell, an infrared filter

assembly positioned relative to an incident radiation side surface of the photovoltaic cell to allow passage of at least a short wavelength portion of incident radiation whilst at least minimising the passage of longer wavelength portions of incident radiation and at least one incident radiation concentration device to concentrate incident radiation through the infrared filter assembly to the at least one photovoltaic cell.

3. A photovoltaic assembly as claimed in either claim 1 or claim 2 wherein the at least short wavelength portion of incident radiation is near infrared radiation.

4. A photovoltaic assembly as claimed in claim 3 wherein the infrared filter assembly

allows near infrared radiation to pass whilst minimising or preventing passage longer wavelengths of radiation.

5. A photovoltaic assembly as claimed in any one of the preceding claims wherein the

infrared filter assembly is a heat exchanger or vessel through which a fluid can flow to absorb or filter less preferred portions of incident radiation.

6. A photovoltaic assembly as claimed in claim 5 wherein the heat exchanger or vessel is a substantially planar, three-dimensional, rectangular vessel.

7. A photovoltaic assembly as claimed in claim 6 wherein the vessel is substantially the same dimension as the PV cell to which it is applied, covering the PV cell.

8. A photovoltaic assembly as claimed in any one of claims 5 to 7 wherein the heat

exchanger or vessel is mounted relative to the outer face of the PV cell.

9. A photovoltaic assembly as claimed in any one of claims 5 to 7 wherein the heat

exchanger or vessel is mounted in a configuration which spaces of an inner surface of the heat exchanger or vessel from an outer surface of the PV cell to further increase the temperature reduction of the PV cell by limiting any conductive heat transfer.

10. A photovoltaic assembly as claimed in any one of claims 5 to 9 wherein the heat exchanger or vessel has at least one transparent sidewall substantially parallel to the outer surface of the PV cell.

11. A photovoltaic assembly as claimed in any one of claims 5 to 10 wherein one or more of the walls of the heat exchanger or vessel are coated in order to filter or collect portions of the incident radiation spectrum.

12. A photovoltaic assembly as claimed in any one of claims 5 to 1 1 wherein one or more of the walls of the preferred heat exchanger or vessel are provided with a coating or surface conditioning allowing photons to pass rather than be reflected outwardly and/or more effectively traps photons within the preferred heat exchanger or vessel.

13. A photovoltaic assembly as claimed in any one of claims 5 to 11 wherein the heat

exchanger or vessel is hollow in order to allow a heat transfer medium to flow

therethrough.

14. A photovoltaic assembly as claimed in claim 13 wherein the heat transfer medium chosen is absorbent to portions of the spectrum except near infrared allowing the near infrared wavelengths to pass through the heat exchanger and heat exchange medium, to the PV cell.

15. A photovoltaic assembly as claimed in an one of claims 5 to 14 further including a

number of radiation transparent baffles incorporated into the heat exchanger so as to direct the heat exchange medium from a central point of entry outward toward the edges of the heat exchanger.

16. A photovoltaic assembly as claimed in any one of claims 5 to 15 mounted relative to a solar tracking device in order to ensure that the incident radiation strikes the PV cell as efficiently as possible.

17. A photovoltaic assembly as claimed in any one of claims 5 to 16 wherein the mounting device used moves the photovoltaic assembly into a safe position during inclement conditions.

18. A photovoltaic assembly as claimed in any one of claims 1 to 4 wherein the infrared filter assembly is provided in the form of a coating to an outer portion of the PV cell

19. A photovoltaic assembly as claimed in any one of claims 1 to 4 wherein the infrared filter assembly is provided in the form of a tandem PV cell provided with one or more secondary layers of silicon of different type to allow use of a useable portion of the spectrum of the incident radiation other than near infrared as well as allowing the at least short wavelength portion of the incident radiation to pass to a PV cell.