DEVICE FOR THE VALORIZATION OF THERMAL ENERGY PRODUCED BY PHOTOVOLTAIC PANELS

Abstract

The present invention relates to a device for recovering low-quality heat (above 30°C and below 150°C) produced under photovoltaic panels, centralizing its collection, and converting the accumulated heat energy into electricity to supplement the panel's natural power output. Incidentally, the process increases the efficiency of the photovoltaic panels by reducing their temperature and, consequently, extending their lifespan. Furthermore, the invention enables the local and completely green delivery of byproducts such as industrially usable cold air, or, through hydrolysis, hydrogen and oxygen.

Description

Title of the invention: DEVICE FOR RECYCLING THERMAL ENERGY PRODUCED BY PHOTOVOLTAIC PANELS FIELD OF THE INVENTION

[0001] Photovoltaic (PV) panels are designed to ensure the conversion of the energy from solar radiation into electricity. But most of the energy received by the PV is lost in the form of dissipated heat. While thermal photovoltaic (PV-T) panels exist, no operational system allows the simple recovery of the ambient air heated under the PV to centralize it at a single point and then convert the heat it transports into electricity, adding to that directly produced by the PV. The present invention relates to a device for recovering so-called low-quality heat (> 30°C and < 150°C) produced under the photovoltaic panels, centralizing its collection and transforming the energy accumulated in the form of heat into electricity. STATE OF THE ART

[0002] The heat flow generated under the PVs is entirely lost by dissipation in the atmosphere whereas, taking into account the average efficiency of the PVs, it represents 75% of the available energy and the resource is free.

[0003] In certain configurations the hot air flow is recovered, to produce additional electricity, for example, by means of a device based on the low-efficiency Seebek effect. In this case the system is generally located inside each PV, or, at best, in all the PVs of the same group, but always by means of a circuit which passes through each of the panels, in which a working fluid (water, air or organic fluid) circulates and captures the calories carried by the heated air.This process is of average efficiency since it often requires two passages of the fluid in the PV to collect enough calories, it weighs down the PV (+ 50%) which harms its production, its packaging, its transport, its handling and its installation and increases these costs (+ 50%), raises its sale price (+ 100 to 300%) lowers its efficiency (-2 to -5%), multiplies the causes of breakdowns and incidents and generates new types of breakdowns linked to the physical incompatibility of the interface between an electrical network and a liquid network, raises the cost of maintenance and makes it more complex to carry out.

[0004] In other configurations, for example based on the Rankine effect, the heat lost at a higher temperature (> 200°C) is recovered in an industrial-sized unit which is not rational for small and medium-sized conformations.

[0005] Most often, PV-Ts integrate a means of concentrating solar radiation, or even compressing the recovered flux, in order to raise its temperature, which increases the surface area of ​​the system, generates additional manufacturing and installation costs, multiplies the sources of breakdowns, involves specific adjustments and calibrations, severely restricts maintenance, and presents risks for operators.

[0006] In order to allow the smoothing, over time, of the operation of these processes, they can be equipped with a means of storing the recovered energy. The storage is generally carried out in a second stage, after a first heat exchange between the hot air and a working fluid under the PV. When this means is implemented, the device is either in the phase of collecting the energy produced by the heat, or in the phase of restoring it, this alternative operation limits its operability to a cyclic use in which the energy is accumulated during the period of sunshine and used outside this period. In any case, the stored energy is, in the vast majority of situations, used as is or after a final exchange, as a means of heating or cooling the individual home and not to produce electricity. Summary of the invention

[0007] The device according to the invention [Fig.l] makes it possible to overcome all these drawbacks without producing waste or toxic materials and by using materials that can be recycled indefinitely.

[0008] The invention proposes to collect, as is, all of the low heat (< 150°C) produced by solar radiation under the PV, to store it temporarily and then to convert it into electricity.

[0009] The invention comprises three sub-processes. The first sub-process allows the sequestration, extraction and transport of the air loaded with calories. The second sub-process is based on a well-known device for temporary heat storage by means of phase change materials (PCM) improved, in the present invention, by a particular means that allows the complete system to operate continuously and not alternatively. The third sub-process is also well known since it is based on an optimized organic Rankine cycle (ORC), which ultimately has the task of converting the energy available in the form of heat into electrical energy.

[0010] In order to maximize the temperature level of the hot flow, the invention distinguishes the possibility of supplying the system with an ejector (Vortex)(18).

[0011] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The first sub-process is responsible for capturing the air heated by the effects of the solar radiation and stagnant under the PV, its essential element is a box (BOX) [Fig.2](l).

[0013] According to a first characteristic, the BOX is preferably parallelepipedal in order to fit perfectly into the natural geometry of the PV (21) under which it is installed. It can, however, adopt a different one if the shape or dimensions of the PV or the installation conditions require it.

[0014] The position of the BOX makes it possible to isolate, in a defined space, a volume of air at the maximum temperature that can be reached depending on the time of year, the time of day, the local and specific atmospheric conditions, the type of PV, the exposure angle and the conformation of the BOX. This space is the air gap (20), it is created between the BOX and the underside of the PV by integrating the void formed by the base of the frame of the PV with its active face.The BOX is made of a material which may be metallic, such as steel, aluminum, iron, or an alloy, a polymer of mineral or vegetable origin, recycled or not, graphite (or one of its predecessors, a derivative or a mix) or any other type of material, sufficiently waterproof once formed, by folding, stamping, roll-forming, casting, extrusion, tapping, welding, 3D printing or any other means, or made waterproof and weatherproof and whose degradability over time complies with the specified requirements for the photovoltaic process.

[0015] According to a second characteristic, the innovation is based on the maximum safeguarding of the captured heat carried by the ambient air to improve the quality of the heat transfer (heat transfer coefficient) to the initial heat transfer fluid (air) and avoid the dissipation of heat into the atmosphere through the components of the BOX, increase the thermal conductivity that governs the flow in its transfer function and reduce heterogeneous nucleation. Depending on these objectives, when it is decided or when the material used to make the BOX does not have sufficient or optimal qualities, the interior of the box can be coated, while preserving its flatness and reducing asperities, roughness and protrusions to a minimum in order to protect the quality (direction, liveliness, convolution) of the flow created, with a reflective product (paint, paste, coating, sheath, surfactant, glue, of any type).The reflective material can be completed by the application of a thermal interface material (TIM), preferably of the nanometric type and prepared by ball milling to facilitate its coating, such as graphene (or a graphite derivative: GNP, RGo, CNT, SWCNT nanoplatelets, or a composite containing graphene and another material such as copper or boron nitride). The reduction of the TIM is preferably carried out by means of a reducing agent of natural origin (glucose, albumin protein, vitamin C, melatonin, sugar, green tea, ginseng, red wine or bacteria).

[0016] According to a third characteristic, two antagonistic tips of the BOX (1,2a and 1,2b) are perforated with one or more openings to allow the circulation of air at the inlet (E) and outlet (S). The side allowing the entry of fresh air (1,2b) is perforated by means of orifices, preferably in the form of slits. This type of perforation keeps the material separate from the sheet and forms an internal opening specifically oriented towards the top of the box to force the convection movement of the incoming air towards the underside of the active part of the PV in order to expel bubbles resulting from possible nucleation and to ensure its cooling. However, the inlet orifices can have any shape provided that they ensure, within the programmed time of the hot flow extraction phase, the entry of fresh air under satisfactory conditions of volume, speed, distribution and circulation in the BOX.The other two panels (1.1a and 1.1b) and the bottom (lc) of the BOX are completely closed except for technical reservations, if any, on one or more of the elements (for the purpose of evacuating satellite water, cleaning the inside of the BOX such as removing dust, insects or other pests, passing cables, installing electrical and / or electronic boxes, inserting structural devices and / or supports, elements of the photovoltaic installation such as inverters, micro-inverters, ballast loads, boxes, concentrators, monitoring systems, tracking means, transformers, converters, sensors, detectors, automatic maintenance and servicing systems or others. One or more of the sides may be fully or partially movable and / or articulated.

[0017] According to a fourth characteristic, the BOX (1) is independent of the PV (21) with which it is integral by means of a fixing [Fig.4] (Several compatible fixing systems presented include existing or adapted means of existing ones and innovative devices, without this state being exhaustive). The fixing must adapt to the thickness of all the PV frames and to all the dimensions of the BOX, it acts as a gripper but can operate by controlled forcing, pinching, blocking, simultaneous compression of two or three elements (22, 25). The grippers are tension springs or any other means such as a plate with (30) or without reinforcement (31) which are screwed (40) or riveted (27) on the box and adjustable in height according to, for example, a slide method (oblong shape) (35), mechanical (screw penetrating or not in the BOX and / or the rail (24).The grippers are locked by means of a hammer nut or an insert (36) slid into a rail or by a stirrup (37), fishplate, ratchet, spring, grasshopper or any other effective device. The fixing elements may consist: for adjustment, guidance (38) and immobilization (39 and 37) in the upper part, in a spacer, threaded or not, forming a partial (28, 29) or total (over the entire length of the BOX), and consisting of an intermediate part, called penetrating, fitted into the BOX (33) and / or arranged outside the BOX and fixed. by screwing (40) or riveting (27); of crampons; of mobile hooks; semi-mobile or articulated and for the lower connection, according to an arrangement which links, at the same time (34) or in two times, the BOX (1), the PV (21) and the base or the support (rail, tube, profile..)(23) on which the elements are positioned. The fixing can also be directly articulated with the reservations proposed by the panel manufacturers within the framework of the PV.These principles make the innovation universal because it can be adapted to all types of existing or future PV, as well as to installations already in place, to all supports (sloping or flat roofs, facades, shade structures, panel fields), to all means of fixing the PV (support profiles, whatever the shape of the profile, mini-rails, single or multiple rails, welded or mechanically fixed rails and supports, welded, glued or mechanically fixed brackets, weighted panels, devices on roof frames or specific, with fixed, adjustable or mobile feet, process with tracker), whatever the exposure slope given to the panel (from 0° to 90°), to all support materials (tiles, slates, sheet metal, corrugated or trapezoidal sheet metal, fiber cement, free frames), as well as to all exposure modes: flat, in two sections, in landscape or portrait whatever the number of panels; single, isolated, field or tunnel installation.

[0018] According to a fifth characteristic, the BOX can be arranged under a single PV or, when the PV layout plan allows it, in a continuous series forming a tunnel of contiguous PV (2 or more) [Fig. 3]. In this hypothesis, the series of BOXes forming the lower part of the tunnel is produced according to the description of the invention by removing, at the right of each junction between BOXes, the end pieces having the openings intended for the air inlet (1, 2a) and outlet (1, 2b), keeping only the first at the start and end of the tunnel. An assembly system (41), comprising two sides (42) and a bottom (43), is added inside the BOX, without hindering the circulation of air or outside of it.

[0019] According to a sixth characteristic, each BOX is equipped with a means of extracting ((3)) the hot air produced therein, by regulated depression of a transfer and transport network. Dimensioned according to the required power, one or more suction units (fans with a vacuum function) create, when they are started, at the time determined according to the programmed criteria, and managed by the system, a depression upstream of the circuit and an overpressure downstream of it. The transport takes place, from the hot air outlet orifice(s) (1, 2b) by means of a duct (2, 1) which connects the BOX to the evacuation and transport network (2) consisting of one or more collectors (2, 2). The exhaust and circulation duct(s) for the captured air may be metallic and / or made of flexible and supple materials. The whole is insulated and / or traced to limit the loss of thermal load.All or part of the collection circuit can be coated, in its in- surface. interior, of a thermal interface material (TIM) which reduces this loss.

[0020] The second sub-process (4) has the mission of storing the heat carried by the flow captured by the BOX, of preserving the heat under minimal loss, of restoring it to the third sub-process at its request, while guaranteeing uninterrupted and regular storage and delivery movements in volume and power. If the conservation of energy by phase change materials (PCM) is well known and documented, there is no process in the field of PV-T which integrates it other than to regulate the use of the stored heat so as to restore it outside the period during which it is captured (alternating operation).

[0021] According to a seventh characteristic, the sub-process (4) comprises a control valve (4, 1) which ensures the control of the movements and the flow rate (volume and speed) according to a decision table managed by the recorded program and distributes the fluid to one of the two boxes (4, 2) and (4, 3) which are contiguous but not communicating and which form the storage complex. Each box is an exchanger consisting of a piping circuit circulating alongside a set of sheaths containing a phase change material which is a heat transfer fluid or another device for capturing and retaining heat (cement, etc.). Preferably, the support is a fluid which is selected according to parameters specific to the installation: thermal stability, density of the melting point, heat capacity (calorific), viscosity, thermal conductivity, vapor pressure, freezing point, chemical compatibility with stainless steels.In the piping circuit circulates the hot air extracted under the PV. The system supplies one or the other of the boxes depending on whether or not it is in the heat restitution phase towards subsystem 3. In the box, then delivered, the PCM passes from its initial phase to the final phase under the effect of the heat transferred to it or captures the energy according to its conformation and its operating principle if it is not that of solid to liquid. The subsystem retains the heat for the necessary duration of time according to the programming and the requirements of the system. When the production of electricity requires it, a compressor (5) charges the network of one of the boxes with compressed air according to its availability, and its state (in the filling or emptying phase), which allows the reverse maneuver to be carried out to that of the supply.This movement blocks the possibility of supplying the requested box with new captured energy but does not in any way affect the capacity of the second box to be recharged. This organization ensures permanent operation of the whole even when the storage function is activated at the same time as the destocking function.

[0022] The third sub-process forms a thermodynamic Rankine cycle (ORC) and allows the conversion of the captured heat into electricity.

[0023] According to an eighth characteristic, the hot air propelled by the compressor feeds one of the circuits of an evaporator (6) which is preferably a plate exchanger (for example brazed plates coated with an internal complex (TIM) improving the heat exchange) but which can be of another design. The second circuit is fed by a working fluid in the liquid or gaseous state. The working fluid is preferably CO2 (R744) but can be any simple or mixed organic fluid (Zeotrope), which expands at low temperature.The working fluid is chosen, taking into account the constraints of the operating unit, for its optimal qualities, viscosity, surface tension, thermal conductivity, flow quality, mass flow rate, COP, specific energy consumption, specific gravity, molecular weight, thermal efficiency, enthalpy, high temperature stability, evaporation temperature, slip point (critical temperature and normal boiling temperature, boiling point level, critical pressure, specific heat, specific volume, bubble point or dew point) and in terms of safety and operating classification (lower flammability limit, heat of combustion, occupational exposure limit) finally for its suitability with environmental requirements (annual atmospheric lifetime (ATMy), global warning potential (GWP), ozone depletion potential (ODP))..

[0024] According to a ninth characteristic, the working fluid is vaporized and, under the control of a flow regulator (7), is directed towards a turbine (8) which transforms the steam into kinetic energy, itself transmitted by means of a shaft (9) to an alternator (10) which produces electricity. The flow regulator can be controlled (9,1) by the transmission shaft to avoid water hammer. The steam entry into the turbine is also regulated according to the volume, flow rate and temperature of the hot air distributed by the evaporator.

[0025] According to a tenth characteristic, as soon as the superheated steam enters the turbine, part of it can be captured to be directed to a regenerator (IHE) (15). The steam, at the outlet of the turbine, or the balance, after collection to supply, possibly, the IHE, is evacuated to one of the circuits of a condenser (12) in the second circuit of which cold water is introduced, taken from the network or from an ad hoc basin, by means of a pump (13). The cooling fluid can be air. The exchange makes it possible to restore on the one hand the working fluid to the initial state at its delivery temperature and, on the other hand, water whose temperature has been lowered and which is returned to its original basin (or to the public network) (14).

[0026] According to an eleventh characteristic, the subsystem can integrate a regenerator (IHE) whose function, when implemented, is to preheat the working fluid after it has been cooled by fulfilling its force-creating function. kinetic. The working fluid extracted from the condenser is heated by exchange with the steam fraction from the turbine. The fluid remains in its primary state but sees its temperature rise to a level close to its boiling point. This device makes it possible to optimize the consumption of the heat taken from under the PV, which, for a given cycle, is reduced by 50 to 70%.

[0027] According to a twelfth characteristic, the entire process is controlled by means of dedicated software which determines the times of launching of the hot air extractor (3) according to the time of year, local and installation-specific parameters and the temperature of the intra-BOX air, measured by means of sensors. The program also determines the destination of the air taken to one or other of the boxes of the PCM (4) and manages their availability. Similarly, the operation of the entire sub-process 3 is optimized (volume and speed of the steam injected into the turbine, time and volume of the superheated steam taken for the benefit of the IHE, control of the various parameters including the temperature of the cooling water returned). Different sensors connected to the software protect against operating alterations, breakdowns and malfunctions, by sending the data back to the control station if it exists or to an external service.The software is capable of interrupting all or part of the functions or reducing the quantum of operations while preserving, where possible, the device in degraded operation.

[0028] According to a variant of the process, this is enhanced by the addition of an ejector (Ranque-Hilsch type Vortex) (18). The compressor (5) arranged at the outlet of the storage unit (4,2 and 4,3) of subsystem 2 (PCM) delivers the hot air to the ejector (Vortex). The fluid is then divided into a very hot part, which is directed towards the evaporator, which greatly increases (+ 30 to 40%) the quantity of steam produced to feed the turbine and a very cold part which can be used in another process, or returned to the atmosphere or used to cool the working fluid in the condenser, which reduces the consumption of cooling water and the volume of its discharge.

[0029] MANNER IN WHICH THE INVENTION IS CAPABLE OF INDUSTRIAL APPLICATION

[0030] A scientific article published on 02 / 11 / 2021 by two researchers in physical geography from the universities of Lund and Hawkesbury argues that solar panels in the Sahara could boost renewable energies but would harm the global climate, to the point that it could lead to the disappearance of the human species through the effects of global warming induced by heat emissions from solar radiation through PV. The article is the subject of controversy but no one provides a technical solution to the claims it makes, which are at least partially founded. The present invention, the object of which is the total recovery of the heat produced and its transformation into electricity, destroys the ob- jections on this subject.

[0031] A report from the International Energy Agency (IEA) indicates that solar energy recovery technologies should provide 11% of the electricity produced in the world in 2050, this is the "Blue Map" scenario which reduces the share of the recovery of solar thermal energies to the detriment of the expected efficiency of PV. This is a huge paradox since this recovery does not require any particular research, is based on a free source involving practically only the exploitation of the structure of the PV fields. The BOX, constituting the innovation, and its decisive accessory formed by a pair of PCM boxes with sequenced operation meets all the requirements since it can, for a minimal investment, allow to double, in the best cases, the electricity production of the existing PV network and offer numerous by-products.The innovation is applicable in all configurations to be implemented and, for existing ones, without harming them and therefore without risk of leading them to drift from the specified legal and contractual requirements or existing approvals and certifications.

[0032] One of the additional positive effects of implementing the innovation is the improvement of the quality and regularity of cooling of the active part of the PV. The management of the flow of fresh air and the intensity of the extraction of hot air lead to a reduction in the average temperature of the modules (cells) in such a way that the efficiency of the panel is improved by 1 to 3% and its lifetime is extended by reducing the effects of degradation over time.

[0033] Depending on the actual configuration of the system and the volume of raw material input (Energy), the invention generates, as another by-product, also obtained at the lowest cost, the very cold fluid produced by the vortex and usable in an industrial process or for the energy consumption of conventional housing.

[0034] The surplus electricity produced can be used to supply perfectly green oxygen and / or hydrogen, in the local network, by adding a hydrolyser which, in addition, can be supplied by the water heated in its exchange with the steam in the condenser. This reduces possible water discharges outside.

[0035] Similarly, electricity can be used as a green fuel for biological systems by converting it into biochemical energy by reducing, for example, the power of NAD(P)H, ferredoxin and adenosine triphosphate (ATP).

[0036] From an environmental point of view, the invention does not emit any toxic emissions, does not create any waste, is made from totally recyclable materials, requires only minimal maintenance, and can be sized according to the volume of hot air available. In particular, it can be miniaturized to create only a low volumetric and surface impact. In its operation, the invention can be consumer of CO2 which is a powerful greenhouse gas.

[0037] Technically the invention is autonomous, that is to say that it can be implemented using any PV from any manufacturer without the intervention of any other external means since it has its own support (which is the subject of a specific invention patent) and its own fixing device (the subject of claim 5). But it has the advantage of being able to adapt instantly, without substantial modification and without affecting their integrity, to existing fixing and supporting methods, in this case, for installations already carried out or those to come. POSSIBLE VARIANTS

[0038] The invention is not limited to the embodiments described in the foregoing. It is obvious that many versions are conceivable within the scope of the claims made. These modifications may relate to the nature of the materials composing the BOX, the methods of connection between the different elements of the BOX and between the BOX, the PV, and the support of the assembly as well as between the components of the sub-processes and in particular the devices capable of reducing the exergy of each of said components and improving their efficiency. These may be regulation or control systems, the chemical composition of the reflective coatings internal to the BOX, the pipes and the exchangers, the conformation of the mechanical and hydraulic transmissions, all variations which cannot characterize an essential difference with the present innovation.

Claims

Claims

1. Device for isolating and collecting hot air generated by solar radiation on the underside, in the air gap of photovoltaic (PV) panels and characterized in that it comprises a housing of parallelepiped shape, or, in any case, in the shape of the PV with which it is integral and called BOX. The BOX is formed of two solid sides, two sides comprising orifices ensuring the entry of fresh air, the extraction of hot air and a bottom. The bottom of the BOX has a flow means. Other reservations can be provided to ensure the passage of the devices necessary for the operation and maintenance of the PV.

2. Device according to claim 1 characterized in that, in order to improve the thermal conductivity inside the BOX, the material composing it is covered with a reflective product to which is added, on the surface or in the mass, a nanometric type interface material.

3. Device according to claim 1 characterized in that the side allowing the entry of fresh air is perforated by means of orifices, preferably in the form of holes specifically oriented towards the top of the BOX, in the direction of the underside of the part of the PV.

4. Device according to claim 1 characterized in that the BOX is fixed to the PV and to the support on which these devices are placed by means of a system of fasteners which strongly bind them and immobilize them.

5. Device according to claim 4 characterized in that at least one of the attachment systems is a screw for fixing and locking the BOX and the PV and / or the support means (rail, profile, tube, etc.) and consists of a spacer penetrating the BOX or passing through it entirely, which can be simply fixed to the outside of the BOX, ensuring, at the same time, by means of a threaded axis and a hollow axis, the immobilization of the locking screw and its precise guidance along the PV and the BOX.

6. Device according to claims 1), 3), 4) and 5) which allows the positioning of BOX in a continuous series forming a tunnel.

7. Device according to claim 1 characterized in that the hot air outlet(s) are provided with a flexible or rigid sheath, connecting the BOX to an evacuation network consisting of collectors. The network of collectors is insulated and / or traced. A fan with a vacuum function creates, at programmed time intervals, a vacuum upstream and overpressure downstream of the network to ensure the extraction and rapid circulation of the hot fluid to sub-process 2.

8. Device formed from a distribution valve and two independent boxes, which makes it possible to store the heat captured in a process based on phase change materials.

9. Device according to claim 8 allowing the control of the supply distribution valve. The purpose of the control is to direct the heat transfer flow delivered to one or other of the boxes, depending on the needs of the process, ensuring that the selected box is not, at the same time, in the phase of restoring the heat in which it is stored. In this case, the means diverts the flow to the second box. The system does not allow the two boxes to be supplied or emptied at the same time so that at any time when one box is filled the other box can supply the downstream device.

10. Device according to claim 8 which comprises a compressor which injects a cold flow making it possible to extract the heat stored in one or other of the boxes.

11. Device forming an ORC (Organic Rankine Cycle) type process comprising at least one evaporator, optimized exchanger, the function of which is to ensure the vaporization of a working fluid at low boiling temperature, a flow regulator controlled by the transmission shaft between the turbine and the alternator, one or more turbines, a means of transmitting the kinetic energy created by the turbine to an alternator which produces electricity, a condenser, a pump for supplying the cooling fluid (water or air).

12. Device according to claim 11 which comprises an ejector (Ranque-Hilsch type vortex) which separates the hot air coming from the PCM into a hot flow which feeds the turbine and into a cold flow which can be discharged into the atmosphere or consumed industrially or civilly.

13. Device according to claim 11 which is equipped with a system for withdrawing a small part of the superheated steam in the turbine to be directed towards an internal heat exchanger (IHE) which preheats the cooled working fluid and a pump which ensures the reintroduction of the working fluid, heated slightly below its boiling temperature in the evaporator where the cycle begins again.

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