PHOTOVOLTAIC PANELS

Field of invention

The invention relates to a device, which enables more efficient use of the energy of solar radiation incident on solar photovoltaic panels.

Background of the invention

Currently, solar photovoltaic panels are known to convert the energy of incident solar radiation into electrical energy. The solar panel is made of a plate -bearing substrate embedded in the frame. There is an electrode, placed on the plate substrate, on which are formed photovoltaic cells made of semiconductor elements based on silicon. The semiconductor elements lie under a transparent covering layer, e.g. made of glass with an anti-reflective coating.

Currently known solar photovoltaic panels technologies have an energy conversion efficiency, of incident solar radiation, of about 17% under the optimal operating conditions. The remaining energy is converted into waste heat that heats the solar photovoltaic panel and this energy is, without any use, radiated to the surroundings of the solar photovoltaic panel. The most important operating conditions of a photovoltaic solar panel include spatial orientation of the solar panel, relative to the direction of solar radiation, and operating temperature.

Especially the operating temperature of the solar photovoltaic panel is the most pressing problem because with increasing operating temperature the already limited efficiency of the photovoltaic technology decreases. Furthermore the lifetime of the photovoltaic elements is reduced since so- called hot spots appears, where the heat waste causes the rise of temperature up to about 100° C, resulting in degradation (short-circuiting) of semiconductor elements.

The abovementioned description of the composition of the most used types of solar photovoltaic panels shows a deficiency in the ability to dissipate or radiate waste heat, especially when cooled by the ambient air. Therefore, it is an undesirable paradox that for our latitude and longitude the efficiency of solar photovoltaic power plants, in terms of ideal lighting conditions in the warm summer months, is lower than in the other months when the air temperature is noticeably lower. The abovementioned shortcomings, associated with a decrease in the efficiency of solar photovoltaic panels due to the effect of waste heat, are solved for example by the technical solution of utility model CZ 19199, which not only actively cools the panels with water in order to increase efficiency of solar photovoltaic panels but it also eliminates the deficiencies of non-ideal light conditions by the concentration of solar radiation by means of reflective surfaces.

Another known solution is an invention of WO 2018148796 A in which a liquid circuit, cooling the photovoltaic panels, is described. In the invention, there is also described the possibility of using a Peltier cell to generate electricity. Another known solution is the technical solution of utility model CN 203464537 U. In this technical solution, there is presented a system of a heat pump that includes solar photovoltaic system for the active removal of waste heat from the solar photovoltaic panels.

The disadvantages of the abovementioned solutions are that they create local cooling zones, where the waste heat is actively pumped out but at the same time they leave the hot spots on the surface of solar photovoltaic panel, especially at the boundaries of individual heat exchangers. The first negative impact is that the photovoltaic elements are dampened or even damaged, and different temperatures in the photovoltaic panel surfaces causes stresses in the material due to thermal expansion. These disadvantages result from the fact that heat exchangers are assembled from partial parts so that the effect of thermal expansion, which is different for different materials is minimized and that the photovoltaic panel is not damaged.

The disadvantages of the abovementioned solution lie in the fact that the waste heat is not meaningfully recovered moreover at the time when the value of water rises, its use is not appropriate.

The purpose of the invention is to create a device for managing waste heat from solar photovoltaic panels that efficiently dissipates waste heat from the solar waste panel to improve the efficiency of converting solar radiation into electricity while providing waste heat for further processing. The second important object of the invention is that the omnipresent waste heat does not limit the production of electricity but it also contributes to the production of the electricity.

Summary of the invention

The defined task is solved by creation of the device for solar photovoltaic panels waste heat management according to the following invention.

The device for solar photovoltaic panels waste heat management includes at least one absorber, which is arranged on the back side of at least one photovoltaic panel, to absorb waste heat. The absorber is arranged under solar photovoltaic panel in order not to limit the solar radiation incident on photovoltaic elements. At least one heat exchanger is connected to the absorber. This exchanger is connected into the primary circuit of the heat pump for the active consumption of the waste heat from the absorber. Removal of waste heat positively affects the efficiency of the photovoltaic elements in the electricity production. The heat exchanger is connected into the primary circuit to a heat pump, which transports heat from the solar panel for further processing. It means that the waste heat is not radiated into surroundings without proper use. At the same time, at least one Peltier cell is connected to the absorber. This cell produces electrical energy thanks to different temperatures while the Peltier cell is flat and has heating and cooling side.

The summary of the invention is that the absorber is assembled from a homogenizing plate, mounted on the backside of a photovoltaic panel. Applied to the back of the panel, the homogenizing plate receives waste heat from the photovoltaic elements, thus preventing creation of hot spots. The waste heat is not concentrated at points on the surface of the solar panel but it is distributed over the entire surface of the homogenizing plate. This prevention of the formation of hot spots protects the photovoltaic elements from damage by limiting heat so that short circuits caused by over-heating or interruption of the conductive paths by over-heating between the photovoltaic elements, are prevented to appear. Furthermore, there is a layer of non-hardening heat-conducting paste between the backside of the solar photovoltaic panel and the homogenizing plate and further between the homogenizing plate and the heat exchanger. Since the photovoltaic panel, the homogenizing plate and the heat exchanger are made of different materials, there is a different dimension change due to thermal changes. Therefore it is necessary that the individual components of the absorber are not firmly fixed and stress, caused by stress, is avoided.

At the same time, the homogenizing plate leaves at least a part of the backside of the photovoltaic panel uncovered to keep the waste heat in place and at least one heat collector is connected to the uncovered part of the backside of the photovoltaic panel. The uncovered part of the panel is heated in the same way as hitherto for panels without the absorber. However, this waste heat, not absorbed by the absorber, is fed to the heat collector for further processing. At least one Peltier cell is used to utilize the waste heat from the heat collector. This Peltier cell is arranged with the heating side to the homogenizing plate, and is connected to the heat collector, with the cooling side connected to at least one heat-conducting transition. In this way, part of the waste heat is used to create a thermal difference on the Peltier cell that, at that moment, begins to generate electricity.

The invention combines three basic advantages. The first advantage is that by active cooling of the solar photovoltaic panel, the efficiency of electricity production, from solar power, is increased. The second basic advantage is that the waste heat is dissipated for further processing. An ideal example of use of this advantage is for example installation of such device to solar photovoltaic panels in the sawmill area where the energy, in the form of heat, can be used in a wood drier space, possibly the waste heat can be used to heat swimming pools. The third important advantage is the conversion of part of the waste heat into electricity with help of the invented device. Conversion of waste heat into electricity can compensate bad lightning conditions or decrease of efficiency due to wind conditions, but in any case the conversion increases energy balance of solar photovoltaic panels.

In the advantageous embodiment of the device for management of the solar photovoltaic panels waste heat according to this invention the uncovered part of the back of a solar photovoltaic panel lies at its lower edge from the point of view of orientation of the solar photovoltaic panel installation. This is especially important when installing solar panels in continuous solar arrays on the roofs of buildings. If a hot area is left, at the bottom of the solar photovoltaic panel, the heat will rise due to the natural tendency, causing the so-called chimney effect of the air flow in the space between the roof and the panels. In another advantageous embodiment of the photovoltaic solar panels waste heat management device, according to the invention, the homogenize plate and the heat collector are made of the same material, having the same volume of material with a tolerance of +/- 20 % of the volume. Approximately the same volume values of the two components of the device, including the same type of material, result in the same thermodynamic reaction behavior when changing environmental conditions, such as sudden temperature changes, etc.

In another advantageous embodiment of the photovoltaic solar panels waste heat management device, according to the invention, at least one accumulation tank is connecter into the primary circuit of the heat pump. The accumulation tank serves as a buffer for sudden temperature changes. Alternatively, the accumulation tank can serve as a heat source for defrosting in case of an inverted heat pump working cycle.

In another advantageous embodiment of the photovoltaic solar panels waste heat management device, according to the invention, a vacuum expansion tank consisting of a housing of the tank, for enclosing a liquid heat transfer medium, and bellows for gaseous medium, is connected into the primary circuit of the heat pump. By altering the design, i.e. swapping air and the liquid heat transfer medium in the vacuum expansion tank, it is achieved that any shock, caused by pressure changes, that could spread via the liquid transfer medium is eliminated, thanks to the vacuum expansion tank, when compared to other conventional vacuum expansion tanks.

In another advantageous embodiment of the photovoltaic solar panels waste heat management device, according to the invention, the device includes at least one electrical energy storage, which is electrically connected to the solar photovoltaic panels, wherein the heat pump is simultaneously electrically connected to the solar photovoltaic panel and to the electrical storage. By incorporating a power storage facility into the device, the device gains energy independence and the ability to operate in the so-called island mode, in which the device is completely independent on any external artificial power source. Using solar panels, the device is able to reach maximum use of a renewable energy source, represented by solar radiation, making its operation completely ecological, low- cost and safe to the environment. The advantages of the invention are higher efficiency in conversion of solar radiation into electricity, higher production of electricity by processing of part of waste heat into electricity, prolongation of lifetime of solar photovoltaic panels, simplicity of installation on already existing solar photovoltaic panels and already existing load-bearing structures, energy self-sufficiency and last but not least, the production of heat for direct use.

Description of the drawings

The presented invention will be more precisely explained in the following drawing where:

Fig. 1 shows a scheme of the device according to the invention,

Fig. 2 shows a simplified view from above of a solar photovoltaic panel with absorber components and equipment for converting waste heat into electricity,

Fig. 3 shows airflow below the solar panels on a sloping roof.

Examples of the preferred embodiments of the invention

It is understood that the hereinafter described and illustrated specific examples of the embodiment of the invention are presented for illustrative purposes and not as a limitation of the examples of the embodiment of the invention to the cases shown herein. Experts who are familiar with the state of technology shall find, or using routine experimentation will be able to determine, a greater or lesser number of equivalents to the specific embodiment of the invention which are specifically described here.

Fig. 1 shows a schematic diagram of a device 1 for solar photovoltaic panel 2 waste heat management. An absorber 3, consisting of a homogenizing plate 4 and a heat exchanger 5, is connected to the underside of the solar photovoltaic panel 2. The homogenizing plate 4 is made of a thick aluminum sheet and is fixed to the panel 2 via a thermal conductive paste, to create as large transfer surface as possible. The thermal conductive paste must be made of an inert material in order to avoid stresses between the panel 2 and the glued homogenizing plate 4. Furthermore, the thermal conductive paste must meet the condition that it is inert to the rear surface treatment of the photovoltaic panel 2.

The heat exchanger 5 is formed designed as a hollow body for flowing through with a liquid heat transfer medium, for example an alcohol-based medium. The liquid heat transfer medium must not be aggressive to metals, it must be antifreeze and must be environmentally friendly. The exchanger

5 is made, for example, of steel with an enamel coating. A heat conducting paste is also applied between the exchanger 5 and the plate 4. The heat exchanger 5 is connected to the primary circuit of the heat pump 6, which serves as a pump for the removal of waste heat for further use. The difference of the heat pump 6 is that it uses a vacuum expansion tank _P, joined into the primary circuit. The tank 11 has a switched function of the expansion bellows, when compared to other known state of technique. Gaseous medium is blown into the bellows and a liquid heat transfer medium is blown into the space between the walls of the tank H. Into the primary circuit is connected a water storage tank 10 that serves as a thermal buffer for sudden changes in air temperature. The heat pump 6 can also operate in a reverse mode, whereby the panels 2 can be heated up by the absorber 3, e.g. to defrost the panels.

The device 1 also includes a power storage 12, such as a Li-Ion accumulator, which is electrically connected to the solar panels 2 for charging it with electricity and is also connected to a heat pump

6 to supply it with power. The capacity of the storage 12 is increased according to the number of solar panels 2 and with this related size of the device 1.

Figure 2 shows a bottom view of the solar photovoltaic panel 2. The homogenizing plate 4 of the absorber 3 does not cover the entire underside of the panel 2, but leaves a free strip at the bottom edge of the panel 2 for access. There is a heat collector 7, arranged to this strip, which consists of an aluminum housing. The heat collector 7 has a volume equal to that of the homogenizing plate 4, in terms of material volume. At the same time, a Peltier cell 8 is arranged on the homogenizing plate 4 with a hot side. The cold side of the Peltier cell 8 is provided with an output of the copper thermal conductive transition 9. Heat collector 7 is provided with output of the transition 9. Figure 3 shows the airflow below the solar panels 2 fixed on the sloping roof of the object. By orienting the hot heat collectors 7 to the lower edge of the panels 2, the chimney airflow in the space between the solar panels 2 and the roof, is initiated.

Industrial applicability

A device for waste heat management of solar photovoltaic panels, according to the invention, will be applied on either newly installed or already installed solar panels, domestic buildings, in industrial sites, or in solar power plants.

Overview of reference symbols used in the drawings

1 device for waste heat management of solar photovoltaic panels

2 solar photovoltaic panel

3 absorber

4 homogenizing plate

5 heat exchanger

6 heat pump

7 heat collector

8 Peltier cell

9 heat conductive transition

10 storage tank

11 vacuum expanse tank

12 electrical energy storage