FR2727790A1 - Hybrid solar panel generating photovoltaic electricity and heat - Google Patents

Abstract

The panel reflects the min. solar radiation, converts a fraction to heat and absorbs the remainder. The second surface is of similar size and the peripheral walls between them has holes for circulating gas. The sheets (10) in copper or aluminium or another good thermal conductor form curtains with 50 or more holes per sq. cm. One part of each curtain is joined thermally to the panel and adjacent curtains are slightly sepd. to make them thermally independent. Another part is traversed by gas and joins up with the rear surface. The curtains are parallel to the length of the module and are symmetrical with the central space (15) which collects the hot gases that initially enter along an edge channel (6).

Description

TITLE
HYBRID PHOTOVOLTAIC AND THERMAL SOLAR MODULE
OPERATING IN COGENERATION OF HEAT AND ELECTRICAL ENERGY
DESCRIPTION
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a solar module of hybrid character, that is to say converting solar radiation, firstly into electrical energy and secondly into thermal energy, the latter being conveyed by means of a heat transfer gas: STATE OF THE PRIOR ART.

Since the development of solar cells in the years 1970-1980, sets have been proposed separately combining a greenhouse sensor A, with photovoltaic panels, the said assemblies being able to heat air but using, in general, separate glazed area. To resist the weather, the said surfaces must be of the quality buildings therefore of a high cost.

Furthermore, in the invention, the cost of the surface converting radiation into heat is also saved since it is the panel of photovoltaic cells that plays this role.

The claimed invention is the possibility of circulating a hot gas in an autonomous manner that is to say using the single current produced by the solar cells. It allows the realization of a compact solemn module, produced in factory, whose performances can be guaranteed.

Finally the cost of installing such a module is greatly reduced compared to that of two separate systems.

Compared with the performance of conventional heat sensors, a significant gain is achieved with the claimed invention. This gain results from a double step: The invention uses, for transmitting heat between a panel and a gas, a system of "curtains" made of perforated sheet metal, the gas passing in laminar flow through the holes of said "curtains"; which ensures a considerably increased exchange coefficient while presenting a very reduced pressure drop.

The invention introduces the gas through the periphery of the module where are naturally located the carrier structures, difficult to isolate, which therefore remain at room temperature and the invention further provides the output of said gas by the hottest zone located in the central region of the module.

These two approaches, taken in isolation, are not completely new, one of the authors of this patent used, from 1966, perforated copper screens in exchangers operating at 1 degree Kelvin under an absolute pressure of 10 Pascal. This solution has been widely used since in this particular field of temperature and pressure. The second approach is also common practice, still in the cryogenic field, where the supports of the elements located at low temperature are traversed by evaporated helium vapors that oppose the flow of heat from the atmosphere to the cold parts.

But these two approaches are not associated, especially at room temperature, in the industrial field. And the notorious inefficiency of solid conduction under low temperature gradients seems to condemn the use of perforated sheets driving heat in their plane.

SUMMARY OF THE INVENTION
It took the realization of very particular conditions for the two aforementioned approaches, associated, to contribute to the design of the "hybrid solar module" object of the present invention, recalled in abbreviated form in the following: the "module" ).

It will be seen later that the said module presents:
a) the qualities required of a good solar thermal collector, namely:
1) low thermal inertia
2) Higher thermal efficiency than thermal sensors
traditional
3) good mechanical strength.

4) a lightness and ease of implementation that will be appreciated
5) easy access and maintenance
6) a compact form.

 7) a simplicity of implementation, so a reduced cost.

 8) insensitivity inherent to freezing.

b) qualities favorable to photovoltaic efficiency:
1) Heat cure of light-induced degradation
(Staebler-Wronsky effect) solar cell performance
hydrogenated amorphous silicon, which behave so
their temperature coefficient was positive.

2) possibility of using thin film solar cells on
metal-plastic backing, inexpensive and not very fragile.

3) Glass protection against harmful effects of rays
ultra violet.

This module essentially comprises a volume consisting of two parallel surfaces and side walls, one of the surfaces being the seat of a heat release the other a single wall.

Between these two surfaces, a structure made up of perforated sheet "curtains" ensures the heat exchange between the surface where the heat is released and a gas circulating in forced convection between the two surfaces.

In a particular embodiment, the surface where the heat evolution takes place may be a rectangular panel of photovoltaic cells in which the radiated energy coming from the sun is converted on the one hand into electrical energy, on the other hand into heat.

The gas circulating between the two surfaces can be simply air and the "curtains", through which the heat exchange can be made, can be made of 0.5 to 1 millimeter thick aluminum sheet perforated with holes. circular, of a diameter close to the thickness of said sheet, through which is carried 1 heat exchange.

Part of each "curtain" is thermally bonded by gluing or close approximation to the panel of photovoltaic cells, while leaving a small space between the parts two successive "curtains" thermally connected to said panel of photovoltaic cells to make said " curtains "thermally independent.

The other part of each "curtain" joins the second constituent surface of the space where the gas circulates, forcing the latter to cross successively the so-called "curtains".

These "curtains" are arranged parallel to the longitudinal axis of the module, the number of ten on each side of the axis; the two "curtains" symmetrically placed closest to the axis leaving between them a space intended to act as a collector for the hot gas.

The "curtains" are traversed successively by the gas following a path parallel to the surface of the cell panel and perpendicular to the longitudinal axis of the module so that the gas enters <through two filters arranged on each side of the module) in a place where normally cold bearing structures are difficult to thermally isolate, to exit by a sleeve disposed in the axis where the temperature is highest.

The entire part of the module participating in the heat exchange is sized so that the passage of gas therein in a laminar regime.

Means are provided to circulate the gas in the module.

At the front and at the back of the module are enclosed spaces a few centimeters thick where the immobilized air acts as thermal insulation: at the front, these closed spaces comprise one or more glass walls, optionally coated with an antireflection layer to improve their transparency; said glass walls being intended to produce the greenhouse effect and to absorb ultraviolet rays.

- At the back, there is a single enclosed space whose walls are lined with an infrared reflective coating; alternatively, this rear enclosed space can be filled with an insulating material of low thermal inertia;
At the inlet of the gas in the module are arranged filters designed to prevent clogging of the holes of the "curtains".

A fan, whose motor is powered by the photovoltaic panel, is disposed at the output of said module. This fan will preferably be driven by a permanent magnet motor; the flow rate of said fan will then be practically proportional to the incident solar flux which will achieve a self-regulation of the temperature; in particular, it is possible to choose said fan provided with a permanent magnet motor so that the rise in temperature of the gas remains constant whatever the sunlight.

If the gas to be heated is air it will be taken, preferably, in the room where the temperature is generally higher than the outside temperature.

For example, a hybrid solar module according to the invention, - 50 centimeters wide and 1 meter long, - receiving a thermal flux of 500 watts / m2, - provided with "curtains" connecting space areas of 4 centimeters, the so-called
"curtains" being made of 0.7 mm thick perforated aluminum sheet
of 500 holes 0.7 mm in diameter per cm2, - having on the sun side a confined space of 4 cm in thickness bounded by
a glass plate.

- with a closed space of 4 cm thick coated on the opposite side
internally of a reflective sheet of aluminum, - comprising a fan powered by the photovoltaic panel, allows to heat from 100C to 600C with a thermal efficiency of 68 z and to propel autonomously an air flow of 12 m3 / h; if we take air in a room to be heated whose temperature is of the order of 180C the thermal efficiency goes to 70 t with a flow rate of 15) / h.

In one variant, the solar module may have any shape, the gaseous flow flowing therethrough moving perpendicular to the "curtains" of the periphery of said module, which is at ambient temperature, towards its central part where the temperature is the highest.

In a variant, the glass wall limiting an enclosed space at the front of said hybrid solar module may be the canopy of a veranda which has by destination a "bituminous" quality that protects said module from the elements.

In one variant, one or more of the glass walls arranged at the front of said hybrid solar module may be coated with an antireflection layer in order to improve the transparency thereof.

In a variant, the cells of the photovoltaic panel are made of hydrogenated amorphous silicon or other photovoltaic material behaving as if it had a positive temperature coefficient.

In a variant, the photovoltaic cell panel may be replaced by a single absorption surface close to the unit, which may or may not receive additional heating by joule effect.

In one variant, the gas can heat a gas other than air. FIGURE PRESENTATION
Figure (1) shows in perspective, a cross section of the portion of the photovoltaic module, object of the invention, where the heat exchange is carried out.

Figure (2) shows, in section, the module according to a variant of the invention wherein the front window is constituted by a conservatory canopy.

Figure (3) shows schematically the flow of air through the "curtains" perforated sheet.

The hybrid photovoltaic module comprises a central portion shown in Figure (1) where the heat exchange is effected, this central portion is sandwiched between two closed spaces where the air is substantially immobilized, plays the role of thermal insulation. these two closed spaces are visible in Figure (2) which represents a variant of the invention. The gas circulation mode, which is specific to the invention, is shown schematically in Figure (3).

DESCRIPTION RETAILLER OF THE INVENTION.

In FIG. 1, which shows in perspective a cross-section of the central part of the module, the wall <1> receiving the solar flux is distinguished, the said wall being constituted by a rectangular panel <9> which integrates the photovoltaic cells <2> and a second wall <3> constituting with the side walls <4>, the space in which circulates the gas to be heated, the circuit of which is shown in FIG. 3: the gas enters <5> through two orifices <6> and exits < 7> by a sleeve <8>, holes and sleeve shown in Figure 3.

Between these two walls <9> and <3> are located "curtains" <10> in sheet of good thermal conductivity, perforated with holes to the number of about 50 per cmt said "curtains" being parallel to the axis of module. Part <11> of each of said "curtains" is glued or in close contact with the panel of photovoltaic cells, the parts of two successive "curtains" thermally bonded to the photovoltaic panel being slightly separated <12> to make said "curtains "thermally independent. The part <11> of the "curtains" not connected to the photovoltaic cell panel is traversed perpendicularly by the gas which gradually heats up passing successively from one "curtain" to the next. The gas goes from the edges <4> of the module to the center of the module where two "curtains" more spaced <15> form a collector for the hot gas <16>. At the exit of each curtain the gas has taken a temperature which differs only very little from the temperature of the photovoltaic cell panel to which part of the said "curtain" is thermally bonded; so that the gas energetically cools said panel on its <18> edges which remain at a temperature close to ambient; while, in its axis, said panel is brought to a temperature close to the outlet temperature of the gas.

Attached To the presence of closed isolation spaces on either side of the module, represented in <19> and <20> in FIG. (2), and confined spaces at each end of the module, represented in < 32> in FIG. 3, this design has the effect of reducing the thermal losses of the module by a significant factor and, consequently, of increasing the thermal efficiency of the module, which efficiency, under a solar irradiation of 500 watt / m2 can reach 70 8 by heating air that enters 200C to go out at 600C.

The side walls <4> constitute with the rear wall <3> and the frame <22> of the photovoltaic cell panel, a frame for the module a which it confers a high rigidity without increasing its thermal inertia.

The gas accesses the first two "curtains" side <23> through two filters (not shown) that protect against clogging holes "curtains".

These filters are preceded by a coarser grid (not shown) intended to stop insects, spiders etc ...

Starting from the lateral spaces <31> and after passing through all the "curtains" the gas is in the axial space <16> acting as a collector, to finally exit through the sleeve <8> shown in the figure 3, which can be arranged a fan <25> which fan can be driven by a permanent magnet motor powered by the photovoltaic panel, the combined characteristics of these last two elements provide the system self-regulation of the temperature of the hot gas.

The rectangular shape of the module described above is not exclusive. The module may affect any other form, not shown, with the appropriate adaptations provided that the principle that the gas moves between the "curtains" perpendicular to the latter, by entering the periphery of the module which is at a temperature, is respected. close to the ambient temperature to get out of the central part where the temperature is highest, the surface of the "curtains" being sufficient so that the pressure drop at their crossing remains very small.

In short, the solar radiation reaches the photovoltaic cells <2> where it is converted on the one hand into electrical energy and on the other hand into heat,
Said heat is transmitted through the panel <9> to the part <11> of said "curtains" thermally bonded to the panel, the so-called "curtains" yielding in turn said heat to the gas flow, to the passage of holes <24 >.

Particular embodiment:
FIG. 2 represents a module in the preferred variant where the wall of the module which receives the solar flux <26> is the canopy of a veranda <27>
Between this glass roof <27> and the photovoltaic cell panel <9>, at a distance of, for example, 4 cm, there is a virtually immobilized air space <19> which acts as a thermal insulation with the outside world <28 >. The side walls of said closed space being constituted by a structure <29> having a certain elasticity allowing the module to permanently adjust to the slight movements and relative expansions canopy / module, without developing mechanical stresses.

On the opposite side to the said canopy a wall <30> forms with the central part of the module and the rear of the latter, a closed space <20> of almost immobilized air which acts as thermal insulation compared to the local <33> where the module is located, said enclosed space <20> lined internally with a reflective coating for the infrared <34>, for example a thin aluminum foil. In a variant, not shown, the said closed space is filled with a thermally insulating material, the said material having a low thermal inertia. If this material is a closed-cell plastic foam, thermopolymerized and having a hardened skin, it may possibly participate in the mechanical strength of the entire module. At both ends of the confined space module <32> shown in FIG. 3, play the same role of isolation as the enclosed space <20> and are treated with the same technique.

In a variant not shown, a number of transparent walls can divide the said enclosed space <19> located between the canopy and the panel of photovoltaic cells <9>, in several independent confined spaces, parallel to said photovoltaic cell panel, in order to increase the so-called "greenhouse" effect which consists in blocking the losses by infrared radiation by interposing surfaces which are opaque to them, the said.

surfaces being transparent in the visible range.

In a variant of the preceding descriptions all or part of the transparent surfaces may be coated with an antireflection layer to improve the transparency.

INDUSTRIFTT-FS APPLICATIONS
The "hybrid solar module" will usually be used with means for storing electrical energy and means for storing the appropriate hot and cold, allowing the use of the module to be relaxed on a daily, weekly or even longer cycle, if special local circumstances permit. The storage of heat and cold will advantageously be made by running gas treated or treated by the module, corrugated plastic pipes, kind of agricultural drains, low cost, which will be buried from the depths of the order of the miter in a nol possibly conditioned to improve the thermal diffusivity and volumetric specific heat.

The places of use of the "hybrid solar module", which is the subject of the present invention, can be classified in: 10 - Places already connected to the energy networks:
a) in living quarters with large glazed areas com
the veranda there is, in summer a recurring problem of overheating.

The use of the module will draw air from the
cold storage and bring calories to calorie storage
while accumulating surplus electricity for power
make these transfers and if necessary the inverse transfers
during periods without sun. The hybrid solar module
therefore to ensure completely autonomously and economically all or
Part of the air conditioning of living areas, in summer, period
during which traditional air conditioners are
especially energy-voracious.

(b) in premises temporarily unoccupied in winter the risk of freezing
requires the draining of hydraulic lines and equipment or A
maintain an expensive heating. This last solution implies
a risk of fire always present in the unsupervised places
for long periods. If the heating is electric it
there is also the risk of network failure or that of a
inadvertent disjunction.

20 Living spaces connected to no network:
a) whatever the season and especially at mid-season the module
solar hybrid with moderate storage, can take into account
responsible for the conditioning of inhabited places in summer and mid-season and
bring extra in winter.

(b) in addition to its contribution to the thermal problems of inhabited places, the
Hybrid solar module assisted by a storage battery, can
ensure the power supply of the information media,
automation and computer science.

(c) in places that are absolutely self-sufficient,
the exception, depending on the geography and the exposure, of a heating
more or less important in winter (wood, fuel or propane),
the hybrid solar module is the required solution because the most
economic.

30 in all places, the hybrid solar module thanks to its efficiency
raised to 600C and above, allows the production of hot water
appropriate air / water heat exchanger.

40 different problems for which the hybrid solar module is a solution
all indicated:
a) in the first rank the autonomous drying of grains, fodder and other
vegetable production, particularly in underdeveloped countries.

(b) remote measuring stations with apparatus not
not supporting freezing: rain gauges, to take an example
obvious, but also the control of spring waters, polluted waters
etc ... All devices that perform an optical check has
through a window that must remain dry

Claims (2)

receiving directly or indirectly the solar radiation and, consisting of a panel of photovoltaic cells, said panel a) a first surface, preferably flat and rectangular in shape that it comprises: CLAIMS [1] A hybrid solar module called after the module, characterized by i) reflecting as little as possible, ii) converting a fraction into electrical energy, or neighboring. b) a second surface, parallel to the previous one and of equal dimension iii) absorbing the balance which is converted into heat, a gaseous flow to be heated. said first and second surfaces a space or can circulate c) peripheral walls having orifices and constituting with 1) having said circular curtains in number preferably equal to or greater than 50 per cm 2, good heat conductor and having holes of preferably perforated being aluminum or copper or any other material d) between the surfaces, "curtains" perforated sheet metal, said sheet metal independent. separated from each other to make them thermally as to the photovoltaic panel being slightly the parts of two successive "curtains" linked thermi i) a thermally bonded portion to the photovoltaic panel joined the rear surface. ii) a portion through which the gas stream which part 2) i) is arranged parallel to the length of the module. gaseous hot. axial, said space constituting a flow collector ii) located symmetrically on either side of a space said space constituting a collector located in its axis. gas entering through the lateral edges of the module to join 3) being successively crossed by the gas flow, said gas flow through the module in laminar flow. e) a general dimensioning and a number of "curtains" such as the high flow. and leaving in the axis of the module where the temperature is the most find the carrier structures difficult to isolate thermally by entering the side edges of the module where f) means for circulating the said gas flow, circulation circulation of said gas stream. connection to connect the said module to the easily removable filter system and the output, in the axis, a sleeve g) At the inlet of the gas stream, on the lateral edges of the module, two electric current used to the outside the module. electrical, and in particular appropriate passages for the output of the photovoltaic, with the points where is used the said energy solar radiation conversion by the cell panel h) means for connecting the electrical energy from the central part where the temperature is the highest. from the periphery of the module which is at ambient temperature to its b) in that the gaseous flow moves perpendicularly to the curtains a) in that it has a shape other than rectangular [2] A module according to claim [1] characterized : several volumes closed. the said surfaces and the panel of photovoltaic cells, one or periphery of the said space or spaces, the walls delimiting with the space or spaces at the front of the photovoltaic cell panel and, a) one or more transparent surfaces which limit one or more several [3] A module according to claims [1], and / or [2), comprising: rear of the module, a closed volume. Said volume being either periphery of said space, walls delimiting, with the wall b) a wall limiting a space at the rear of the module, and A the  i) lined internally with a low-emission coating, as  example a thin sheet of aluminum.  ii) lined with cellular thermal insulation or super insulation  as it is used in cryogenic enclosures or  in the combinations of cosmonauts.  canopy without developing mechanical constraints.  the slight movements and dilations between the said module and the so-called  canopy a closed space able to immobilize the air and to adjust  some elasticity, determine between the said module and the so-called  b) in that side walls constituted by an element having  hybrid is formed by the verriere of a veranda  a) the transparent outer surface at the front of said solar module  [4) A module according to claim [3] characterized in that:  reflection.  crossed by solar radiation are coated with an anti  characterized in that all or part of the transparent surfaces  [5] A "hybrid solar module" according to the claims (4)  having a positive apparent temperature coefficient.  made of hydrogenated amorphous silicon or other photovoltaic material  characterized in that the cells of the photovoltaic panel are A hybrid solar nodule according to claim 4 and / or  fan powered by the photovoltaic panel.  that the circulation of gas in the module is ensured by a (7) A "hybrid solar module" according to claim [6] characterized in  or not to receive additional heating by joule effect.  replaced by a single absorption surface close to the unit, which can  according to claim 3 in which the photovoltaic panel is [8] A purely thermal sensor corresponding to the specification of a module