BRPI1004669A2 - Hybrid water heating and photovoltaic generation system with better use of solar energy - Google Patents

Abstract

HYBRID WATER HEATING AND PHOTOVOLTA GENERATION SYSTEM WITH BETTER USE OF SOLAR ENERGY. The present invention features a hybrid photovoltaic generation and water heating system. This system features a solar cell module with a heat exchanger on its back, a thermal solar collector attached to the module to have a degree of angular freedom and a boiler to store hot water. Cold water from a water tank cools the module as it passes the heat exchanger. The degree of freedom between module and collector is interesting as the system can be adjusted according to the position of the sun to maximize energy extraction (this positioning can be done with an electronic positioner driven by a servo motor). ). This is due to the use of infrared reflection promoted by the cells, which can assist in heating water. Therefore, this invention improves devices in two ways: cooling the cells (increasing their efficiencies) and improving the heating system.

Description

"Hybrid water heating and photovoltaic generation system with better use of energy

solar"

FIELD OF INVENTION

This invention is based on a system that extracts energy

Solar in two ways: It uses the energy of longer-wave infrared radiation for water heating and the energy of visible and near-infrared radiation for photovoltaic conversion power generation. It greatly minimizes the flaws that are found in products already invented, as it utilizes two features not yet explored together. The first is the separation of water that cools cells and increases their efficiency from water that undergoes heating. The second is the use of infrared radiation reflected and unused by solar cells to assist water heating. In addition, this invention can rely on a positioner that seeks the best arrangement of the system for better extraction of solar energy.

. 20 The development of new devices and systems for

Alternative energy utilization is one of the most researched branches today. When it comes to solar energy the research is even more pronounced, especially in hybrid systems to better use this energy. These systems can be widely used in medium and large homes. However, many flaws are found in inventions and products already marketed. BACKGROUND OF THE INVENTION

Solar energy has always been and is still very much coveted by engineers, physicists and researchers from around the world. The power present in this energy source is capable of feeding several activities, among them the electric power production and water heating, targets of the present invention.

Conventionally, solar conversion to electricity and heat collection are done in two separate apparatuses. Solar thermal collectors are responsible for storing the sun's energy by heating air or fluids, while photovoltaic cells are used to convert solar radiation into electrical energy. However, the efficiency of photovoltaic cells is inversely proportional to the operating temperature, ie when the photovoltaic cells heat up, their efficiency is compromised.

The best way to dissipate this heat while maintaining the efficiency of photovoltaic cells is to create a fluid flow in these cells. In turn, by creating this flow, it is possible to use the hot fluid for various purposes.

Water is known to be a very efficient element to carry heat and cool photovoltaic cells, preventing any compromise in their operation. Thus, several researches have been directed to the development of hybrid photovoltaic generation and water heating systems. Thus, many of the products and systems already created use a thermal collector positioned behind a photovoltaic module, which takes advantage of the heat released by the module to heat fluids and consequently cool the cells.

It can be seen that a large number of documents have a similar mounting structure, such as FR 2926676, which describes hybrid equipment consisting of a thermal collector mounted within a support on which it rests and within the which can circulate a fluid with which it exchanges heat. The holder has a front face for exposure to light comprising at least one photovoltaic cell disposed on a rear face of the heat trap. The heat exchange between the thermal collector and the fluid is responsible for maintaining the operation of the photovoltaic cells, as stated above.

In turn, ES2303456 also describes a hybrid solar photovoltaic solar panel capable of generating photovoltaic energy and water heating. It is formed by a plate of material of high thermal conductivity, photovoltaic cells are mounted directly on the collector, where a fluid responsible for capturing the heat, decreasing the temperature of the photovoltaic cells, and raising the temperature of the water, as well as in the equipment described above.

Patent application W02007129985 also describes an apparatus that integrates solar radiation power generation through photovoltaic panels and heat collector heat generation into a single panel. Just below this panel are pipes through which a refrigerant flows from the system. Finally, US2009 / 0114212 describes an apparatus which, as in the equipment described above, also aims to increase the efficiency of solar cells. It is differentially formed by a first area containing refractory Fresnel lenses, which cause sunlight to be focused on the photovoltaic zone located below it. Solar energy is stored between these two layers and can be captured by insulators located in the lower layer. Heat can then be conducted through air or fluid filled pipes.

In this layer, there is a second region where photovoltaic cells are located, to which sunlight is directed by Fresnel lenses and where solar energy is converted into electrical. In order to maximize the operation of photovoltaic cells, this area has channels through which air or fluid can pass with the function of cooling them.

We can verify, however, that all these devices have an error that is in their own assembly. The fact that the collector is placed behind the module, as we have seen in the documents described above, presents two problems: it prevents the sun from reaching the collector, impairing water heating; and if the water is hotter than the module, the solar cells will be heated, impairing photovoltaic conversion.

Unlike the aforementioned patents, the

US6063996 shows a triangular mounted hybrid system where on one side there are solar cells while the other acts as a collector. The fluid passes beneath this triangular structure, drawing heat from these two faces and, as a result, warming up. 5/19

As stated earlier, this patent also suffers from the problem of heating cells if the fluid is warmer. Thus, the product goal can no longer be achieved, and actually worsen cell efficiency. This is a common problem and is repeated in virtually all existing hybrid systems.

The present invention, unlike those described above, advantageously utilizes water always coming from a water tank to cool the photovoltaic cells and therefore cold. This water, after capturing the heat of the photovoltaic cells, is transferred to a boiler, not returning to the water tank and allowing the efficiency of these cells to remain constant. It should be noted that in reducing the demand for heated water, the system simply stops receiving cold water and the cooling function of the cell is reduced. Anyway, the system proposed here on average will have cells working with higher efficiency than those previously proposed.

In addition, a second flaw in the invented systems is the non-use of infrared reflection from solar module cells. This reflection occurs mainly in the region of electrical contact under the cells. It occurs for the range of transparent infrared radiation not used by the cell. Because it is transparent, it cuts through the material of the cell and reflects in the metal of the contacts. This reflection can be used to assist water heating, increasing the use of solar energy. The present invention advantageously positions the two devices, heat collector and solar cells, side by side at a predetermined angle so that the solar cells reflect the infrared over the heat collectors.

This increases the use of reflection and further favors the heating of water, which, in turn, is the same as that stored in the boiler and is therefore already preheated.

BRIEF DESCRIPTION OF THE INVENTION

The present invention is a hybrid photovoltaic generation and water heating system comprising solar cell module, thermal solar collector, heat exchanger, fittings, boiler and water pipes.

In this system, the solar cell module, in turn, comprises an upper polymeric plate, solar cells, a metal layer, a lower polymeric plate, a connection between cells and output wiring, which may be arranged on substrates. crystalline or flexible.

Furthermore, the metallic layers of the solar cells promote reflection of the infrared incident on the thermal collector, which in turn comprises a greenhouse formed by a container preferably covered by glass plate or transparent polymer. Inside this container is a coil-shaped tube or some parallel tubes that serve to conduct water that is heated by the sun.

The heat collector and heat exchanger may have varying curvatures and shapes, the heat exchanger preferably comprising parallel tubes or coils. The heat exchanger must also be positioned internally within the greenhouse and behind the solar cell module and fixed to it by an adhesive and thermally conductive material.

In the proposed system, the solar cell module and the solar thermal collector should be positioned facing the incidence of solar radiation, with one or both

Devices can be either fixed or mobile. If they are mobile, the positioning of these devices occurs through an electronic system, preferably a sun visor system and there may be variation in the angulation between them or rotation of the system.

The connections that form the system are resistant to temperature and fatigue, and can be metallic or polymeric when the system is fixed, or formed of a flexible, but resistant material when mobile.

The present invention also comprises a boiler with

a water inlet from the heat exchanger positioned at the bottom, a water inlet also positioned at the bottom and a water inlet from the solar collector being positioned in the upper region of the boiler. In addition, still makes the boiler a

thief, a float or electronic system for water flow control and a water outlet positioned at the top for consumption.

BRIEF DESCRIPTION OF THE FIGURES

Figure 1: Overview of the present invention with the four main elements present. In this case, the degree of freedom between the collector and the base is angular between their planes. Fig. 2: Overview of the present invention with the four main elements present. In this case, the degree of freedom between the collector and the base is the rotation of the system around the normal of these planes.

Figure 3: Top view of possible types of parallel tube heat exchanger or collector.

Figure 4: Top view of possible types of collector or heat exchanger with a coil.

Figure 5: Typical structure of a solar cell module.

Figure 6: Common structure of a boiler.

Figure 7: Reflection rate of parts of a solar cell obtained by wavelength (nm).

Figure 8: Amount of electric current flowing through cell (I) in relation to voltage in cell (V).

Figure 9: Open circuit voltage (Voc) in relation to solar cell temperature (T).

Figure 10: Power generated by a solar cell (P), normalized at 20 ° C, relative to the temperature of the solar cell (T).

Figure 11: Variation in collector water temperature (Θ) in degrees Celsius, in relation to time (T) in minutes.

Figure 12: Variation in collector water temperature (Θ) in degrees Celsius, in relation to time (T) in minutes, with light incidence at 15 °.

Figure 13: Variation in water temperature (Θ) measured in degrees Celsius relative to time in minutes. Figure 14: Variation in water temperature (Θ), measured in degrees Celsius, in relation to time in minutes.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is based on the use of four main devices together: a solar cell module 31, a heat exchanger 11, a thermal solar collector 41 and a reservoir or boiler 51. The heat exchanger 11 is positioned at the rear of the solar module 31, glued with a high thermal conductivity adhesive 21, to remove heat from the cells and preheat the water. One of the edges of the thermal solar collector is coupled to an edge of the module so that there is a degree of angular freedom 05 between them. Thus, the inclination of the module 31 with the coupled exchanger 11 can be adjusted according to the position of the sun, so as to utilize the infrared reflection 04 of the cells and therefore maximize the extraction of solar energy 03. a degree of freedom between the collector and the base of the system, so that there is mobility between them. This mobility may be by angular movement 06 between the collector planes 41 and the base plane or rotational 07 around the collector normal.

Positioning may be provided by an electronic positioner driven by a servo motor coupled to the mechanical system. The use of this positioner is at the discretion of the project, as in some situations it is better not to use it. In this case, the system should be positioned so that solar energy extraction 03 is maximized at noon, when solar radiation is most intense. Water flow is one of the fundamental procedures of this invention. Water from a supplier 51 (such as a water tank or from the street, for example) must first pass through heat exchanger 11. So, since this water is always cold, it will always remove heat from module 31 and never heat up. him. This preheated water 91 enters the boiler 51 so that it can enter the heating cycle with the solar thermal collector 41. This heating is caused by the incidence of solar radiation 03 on the collector 41 and, as already mentioned, is aided with the reflected radiation. 04 by module 31.

With these features, the present invention overcomes all the problems that were previously presented in the previous inventions.

*

The present invention, in Figures 1 and 2, presents a hybrid photovoltaic generation and water heating system, consisting mainly of four key elements: a heat exchanger 11, a solar cell module 31, a thermal solar collector 41 and a boiler 51. The heat exchanger 11 and the solar collector 41 may be, for example, of the types shown in Figures 3 and 4. Module 31 should have an approximate structure to that shown in Figure 5. Meanwhile, a type Reservoir capacity for boiler 51 is drawn in Figure 6.

In Figure 1 we can see the first type that the present invention may have. In it we can see the four main elements mentioned above. In addition, we can see water pipes 02. These connections 02 can be rigid (made of metal or PVC) or flexible (polymeric or metallic hoses, for example). The type of these connections 02 will only depend on how the proposed system will act. The degrees of freedom of system 05, which is the inclination that collector 41 may have relative to the base of the system, and 06, which is the angular movement between module 31 and collector 41, indicate the movements that the system has. This movement must be provided by a constant positioning electronic system, so that the system adjusts so that the solar energy extraction from radiation 03 is maximum. This position is based on the incidence of solar radiation 03 on devices 31 and 41. Solar radiation 03 on the module 31 is converted into electrical energy. In the meantime, the radiation incident on the collector 41 is used to heat the water (ie, it becomes thermal energy). There is also infrared reflection 04, which will be explained when we return to the subject of positioning.

There are two factors that are of utmost importance to the

operation of the present invention. The higher the temperature of solar cells 38 present in module 31 (shown in Figure 5), the lower its efficiency and, therefore, the worse the conversion to electricity. Therefore, there is a heat exchanger 11 positioned behind module 31 to cool cells 38. In addition to this cooling, water is preheated by exchanger 11 before entering boiler 51. Thus, the initial temperature of the water to be heated in the collector 41 is longer, decreasing the time required to heat the water to the desired temperature.

This heat exchanger 11 is bonded to module 31 via an adhesive 21. This adhesive 21, in addition to having the function of gluing both devices.il and 31, must also conduct heat well from module 31 to heat exchanger 11 so that cooling of solar cells 38 happens efficiently. Thus, the adhesive material 21 must be a good adhesive with excellent thermal conduction. Otherwise, system operation may be compromised.

The second important factor is the positioning of the system.

This factor must be carefully worked out because the energy the system uses is not only from incident radiation 03. Because solar cells 38 reflect infrared due to a metal base 36 they have, this reflection 04 is. This is used to assist the heating of the water passing through the collector 41. Thus, both the inclination angle 05 of the collector 41 and the relative angle 06 should be adjusted to an optimal position in order to make better use of solar energy. As already stated, this positioning can be done electronically with a sunshade system.

These degrees of freedom 05 and / or 06 may be nullified by

restrict a definitive position to either or both elements. Thus we can have four situations:

1) Both free angles 05 and 06, regulated by an electronic system.

2) Angle 05 is fixed (attached to base, for example) and angle

06 is mobile, regulated by an electronic system;

3) Angle 06 is fixed at a certain position and angle 05 is movable, regulated by an electronic system;

4) Both angles are fixed, so that solar energy extraction is more effective. It is advisable to adjust it in

position where the energy extraction is maximum at noon.

If there are degrees of freedom in the system, water-02 connections must be flexible, such as polymeric or metal hoses. Therefore, the forming material 02 must be a flexible, fatigue and temperature-resistant polymer or metal. If the system is fixed, rigid connections may be used, which may be metallic or polymeric as long as they are also resistant to temperature variation. If the system has only a degree of freedom, only flexible, moving and rigid connections where the element is fixed can be used.

In Figure 2 we have a second type for the present invention. The system is very similar to the case shown in Figure 1. However, here the degree of freedom 05 does not exist, giving rise to another type of degree of freedom 07. This movement 07 is the rotation of the collector relative to the base. The use of 05 or 07 is at the discretion of the specific installation design of the present invention, as in some cases it may be simpler to use 05 and in others 07. All analyzes of use of a positioning system and materials to be used , made for the first case of Figure 1 (which uses degree of freedom 05) can be considered for the second case of Figure 2 (which uses degree of freedom 07).

In Figure 3 and Figure 4 we have two examples of heat exchanger 11 and thermal solar collector 41 that can be used for the present invention. Despite the representations in the figures, collector 41 and exchanger 11 may have curvatures and their shapes, if appropriate for the project.

Let's start with heat exchanger 11. In Figure 3, we have an 11 of parallel tube type 14. In it water enters 12, passing through parallel tubes 14 being preheated. Soon after, the water exits 13 to pass through connections 02 and into boiler 51. In Figure 4, we have a second type of heat exchanger 11, where we have a coil 15 instead of parallel tubes 14. The operation is the same : Water enters 12, passes through coil 15 being preheated and exits 13, going to boiler 51.

In case the figures represent a solar collector

thermal, the processes are the same. Water inlet remains 42 and outlet 43. Coil 45 and parallel tubes 44 remain the means of heating water. However, collector 41 must have a greenhouse to store heat. This greenhouse can be a glass plate on the top of the box that holds the coil 45 or a plate of a transparent polymer.

However, either collector 41 or heat exchanger 11 should be black in order to better absorb heat radiation. This coloring can be acquired by painting or sand blasting, for example.

Figrara 5 shows the basic and common structure of a solar cell module 31. In it we can see the module frame 34, the glass plate that protects the cells 32, the upper polymeric plate 33 for protection, the solar cells 38, the metallic layer 36, the lower polymeric plate 35, the connection between the cells 37 and finally the output wiring 32. Like the collector 41 and the heat exchanger 11, the module 31 may have curvatures in its shape.

In this figure we can notice some important elements in the

31 required for system operation. The frame 34 protecting it must be adapted to be able to couple the module 31 to the collector 41 or the positioning system. These adaptations may vary depending on the installation project. Thus, the material of 34 should be metallic or polymeric with suitable mechanical properties.

However, the essential factor of the module is the metallic contact 36 behind the solar cells 38. Its importance is that it causes infrared reflection 04 which aids water heating. If the module does not have this contact 36 there will be no such reflection 04.

The material of the other elements is not of great importance to the functionality of the hybrid system. Therefore, for example, solar cells 38 may be monocrystalline silicon, polycrystalline silicon, amorphous silicon, organic, CIGS, compounds III-V, etc. They may be on crystalline or flexible substrates.

Finally, in Figure 6 we have a basic schematic representation of a reservoir 51, better known as a boiler. In it we can identify the inlet 52 of preheated water 91 from the heat exchanger 11; outlet 53 of preheated water 92 to be heated in solar collector 41; inlet 54 of heated water 93 by collector 41; the thief 55; a float 56; and an outlet 58 for hot water 94 for consumption.

The in and out representations of water 91, 92, and 93 show the path that water 57 has and will still take in the solar heating cycle. The arrangement of these inputs 52 and 54 and output 53 in the boiler frame 51 must be carefully arranged so as not to impair their functionality. Thus, inlet 52 should be managed such that water 91 enters the bottom of reserve 57, as it is in this region that water 57 is coldest. This can be by immediately placing inlet 54 in the bottom of boiler 51 or bending the pipe to expel water 91 into the cold water region, as shown in Figure 6. Exit 58 should also be well planned to remove from boiler 51 the part where reserve water 57 is warmer, directing it for consumption.

With or without the presence of a pump to force the movement of the water (because if there is no pump the water circulates by natural convection), the arrangements of inlet 54 and outlet 53 are still important. Water outlet 53 should be positioned at the bottom of boiler 51, as it is in this region that water 57 is the coldest and therefore must be heated. Unlike this, the water inlet 54 from the collector 41 should be positioned in the upper region of the boiler 51, where the water 57 is warmer, avoiding mixing water at different temperatures and losing the heated water 93.

Float 56 is an example of controlling the volume of water entering boiler 51. An electronic system or any other form of control may also be used instead.

Embodiment Examples Exemplol: The Infrared Reflection of the Solar Cell

A solar module was disassembled in some parts and reflectivity tests were performed. These parts were the module with all its layers, the module without the glass and only the glass that protects it (Figure 7).

We could verify that the solar module reflects around

15% to 20% of incident infrared radiation (between 10000nm to 2300nm). This radiation is not actually harnessed by the silicon cells and is reflected by the aluminum contact under the substrate. Therefore, such reflection was used to assist in water heating.

In turn, a test of black glasses in the sun with a mirror and the reflecting module showed that the module adds a considerable amount of radiation to the water, increasing its temperature. The result is shown in Table 1.

Table 1

Indication of final water temperature

INCIDENT RADIATION END TEMPERATURE SOL 4 0 ° C SOL + REFLECTION MIRROR 44 0C SOL + REFLECTION MODULE 42 0C

Example 2: Characterization of the solar cell at different temperatures

A solar cell was placed in a temperature controller, where it was assumed that the cell would be at the same temperature as indicated in the controller. Thus, for each temperature, data were collected from the current flowing through the cell and the voltage at its terminals (Figure 8).

It has also been observed that the solar cell open circuit voltage drop (Voc) is linear with increasing temperature and, similarly, that the maximum power supplied by the cell (Pmax) also has linear dependence on temperature.

Thus, decreasing the temperature of solar cells is an object of the present invention. Thus, to remove heat from the module was made a water passage underneath it (cooling it) just after leaving the water tank before feeding the boiler, thus leaving it preheated.

Example 3: Collector Test

The first test was done with a light source focusing in the normal direction to the collector surface. A distance of 15 cm (random) was chosen between the collector and the center of the light. In Figure 13 we see the temperature increase and asymptotic tendency to a terminal value.

With this normal incidence test we can see that the collector is functioning properly under the incandescent lamp radiation and can be used for future tests with confidence.

The collector was also tested with light falling at an angle of 15 ° to the surface of the collector. The result, which can be seen in figure 11, which in this case will be our reference, because it will be in this same position and situation that the reflections will be tested.

The test result with the light falling at 15 ° shows that the water reached, at equilibrium, the temperature of 10.6 ° C above room temperature. That is, our reference data will be I = I0 for the radiation and θ = θ0 = 10.6 ° C.

Example 4: Module Reflection Tests

With the result set forth in Example 3, it was possible to test how much the infrared reflection of solar cells on the collector could affect water heating. Thus, the same arrangement previously made (the reference) was used for this experiment. /

First, we tested how much an excellent reflector (ordinary mirror) would improve the system to compare it with the efficiency of the solar module of the present invention.

We can see in Figures 13 and 14 that temperature variation was obtained in the water where the light was reflected by the mirror θ = 12.8 ° C; and temperature variation where light was reflected by the modulus θ = 11.9 ° C:

With these values, the following results for module and mirror reflection were obtained:

Table 2: Differences in water temperature in different types of reflection and amount of radiation incident on each of them.

EXPERIMENT TEMPERATURE DIFFERENCE (Θ) RADIATION INTENSITY Oblique incidence (15 °) 10.6 ° C Io With mirror reflection 12. 8 ° C 1,208 * Io With module reflection 11.9 ° C 1,123 * I0

Considering that the mirror is the upper limit of the module's performance, while the light falling at 15 ° is the lower limit, it was found that the module has an impressive performance, contributing to a 12.3% portion of the light's radiation. Incandescent light bulb over the collector.

Claims (25)

1. Hybrid photovoltaic generation and water heating system comprising the following devices: (a) solar cell module, (b) thermal solar collector, (c) heat exchanger, (d) connections, (e) boiler and (f) water pipes. System according to Claim 1, characterized in that the solar cell module (a) comprises a glass plate or upper polymeric material, solar cells with metal layers disposed inferior to each other, lower polymeric plate, connection between the cells. and output wiring. System according to claim 2, characterized in that said solar cells can be arranged on crystalline or flexible substrates. System according to claim 2, characterized in that said metallic layers existing in the solar cells (a) promote reflection of the incident infrared in the thermal collector (b). System according to Claim 1, characterized in that the thermal collector (b) comprises a greenhouse containing serpentine-shaped tubes or parallel tubes. System according to claim 5, characterized in that the greenhouse comprises a container preferably covered by a glass plate or transparent polymer. System according to Claim 1, characterized in that the heat collector (b) and the heat exchanger (c) may have varying curvatures and shapes. System according to Claim 1, characterized in that the heat exchanger (c) preferably comprises parallel tubes or coils. System according to claim 8, characterized in that said tubes and coil are preferably positioned internally to the stove. System according to Claim 1, characterized in that the heat exchanger (c) is positioned behind the solar cell module (a). System according to Claim 10, characterized in that the heat exchanger (c) is fixed to the solar cell module (a) by an adhesive. System according to claim 11, characterized in that said adhesive is of adhesive and thermally conductive material. System according to Claim 1, characterized in that the devices (a) and (b) are positioned towards the incidence of solar radiation. System according to claim 13, characterized in that the positioning of (a), (b) or both devices can be fixed. System according to claim 13, characterized in that the positioning of (a), (b) or both devices can be movable. System according to claim 15, characterized in that the movement of the devices (a) and (b) is preferably carried out by a constant positioning electronic system. System according to claim 15, characterized in that the positioning of said devices may vary in the angle between them or by rotation of the system. System according to Claim 1, characterized in that the connections (d) are resistant to fatigue and temperature variation. System according to Claim 14, characterized in that the connections (d) are rigid in the fixed system, preferably metallic or polymeric. System according to Claim 15, characterized in that the connections (d) are flexible in the mobile system, preferably polymeric or metallic hoses. System according to Claim 1, characterized in that the boiler (e) comprises a water inlet by the heat exchanger, a water inlet to the solar collector, a water inlet by the solar collector, a thief, a float and one outlet for drinking water. System according to claim 21, characterized in that the heat exchanger water inlet is positioned in the lower part of the boiler (e). System according to Claim 21, characterized in that the water outlet is positioned at the bottom of the boiler (e). System according to Claim 21, characterized in that the water inlet from the solar collector (b) is positioned in the upper region of the boiler (e). System according to claim 21, characterized in that the boiler (e) comprises a float or an electronic water flow control system.