Patent Application
20180100676
The present invention relates to a solar device for autonomous refrigeration.
The present invention lies in the fields of self-contained solar air conditioning and self-contained solar cooling.
The use of solar energy for refrigeration is particularly suitable for refrigeration on isolated sites in regions with hot climates and/or that do not have access to the power grid and/or where energy supply is costly.
A number of techniques are known that enable the production of refrigeration either concomitant with the availability of day-time solar energy, or out of phase, during the night.
The current solutions are mainly based on compressor technologies, which consume large amounts of electricity and use refrigerants with high greenhouse warming potential. For isolated sites, these solutions result, for example, in electricity being produced by generators that use a fuel stored in tanks, or in electricity produced during the day by photovoltaic panels being stored in a fleet of batteries. These solutions require, as appropriate, large amounts of maintenance, frequent replenishment of fuel (weekly to monthly), periodic replacement of the battery fleet (every two to five years), and sophisticated electronic control and command devices (controllers, inverters, etc.).
More particularly, a first technique for producing refrigeration during the day consists of converting solar radiation either into electricity via photovoltaic collectors or into work via a thermodynamic engine cycle such as for example an organic Rankine engine cycle, in order then to supply a reverse thermodynamic cycle for refrigeration by expansion (Stirling cycle) or vaporization of a refrigerant (reverse Rankine cycle).
A second method consists of directly using solar radiation in thermal form to supply a gas sorption method of the liquid/gas absorption type, which requires the circulation of a binary or saline solution, such as the ammonia/water or water/lithium bromide solutions conventionally used. Such devices are for example described in U.S. Pat. No. 4,207,744 and U.S. Pat. No. 4,184,338.
These techniques are however relatively complex and costly to implement and require in particular sophisticated control and command procedures for said refrigeration method, particularly circulation pumps and compressors to circulate the working fluids, and/or require low ambient temperatures (below 35° C.) to refrigerate efficiently. These constraints affect the reliability and robustness of these methods.
Another technique is based on methods for the sorption of a gaseous refrigerant by an active solid. These are for example thermochemical methods or adsorption methods. The drawback of such methods lies in the solid nature of the sorbent materials used; they operate discontinuously and lead to intermittent refrigeration, as described for example in U.S. Pat. No. 4,586,345, U.S. Pat. No. 4,993,234 and WO 86/00691.
The object of the present invention is to at least overcome a large number of the problems set out above and also to result in other advantages.
Another purpose of the invention is to solve at least one of these problems by means of a new refrigeration device.
Another purpose of the present invention is autonomous production of refrigeration.
Another purpose of the present invention is to reduce the costs of refrigeration.
Another purpose of the present invention is to reduce the pollution associated with refrigeration.
Another purpose of the present invention is to produce refrigeration more reliably and robustly.
Another purpose of the present invention is to reduce the maintenance demands associated with refrigeration.
At least one of the aforementioned aims is achieved with a device for autonomous refrigeration from a low-temperature solar thermal source between 50° C. and 130° C., said refrigeration being produced with a temperature difference 5° C. to 40° C. lower than the ambient temperature of the outdoor environment and said device implementing a method for the thermochemical sorption of a refrigerant by a solid reagent, said device comprising:
Preferably, the refrigeration produced by the device according to the invention is at a temperature of between −10° C. and 20° C.
The device according to the invention and the variants thereof described below make it possible to efficiently achieve both the solar heating of the reactor and the cooling of the condenser during the course of the day, and the cooling of the reactor during the course of the night.
The completely autonomous management of the day-time and night-time phases without active control is a promising solution for meeting refrigeration requirements on isolated sites in regions with hot climates that do not have access to the power grid. The device according to the invention also makes it possible to reduce production costs as there is no costly external energy supply. Furthermore, as it does not use any consumables, the maintenance of the device—which is limited to occasional cleaning of the collectors—is greatly reduced and inexpensive.
The device according to the invention also makes it possible to reduce the pollution associated with refrigeration as it can use a refrigerant that has no impact on the ozone layer or global warming. Furthermore, the device does not generate greenhouse gases or deplete fossil energy resources as it only uses thermal solar energy, which is a widely available renewable energy. Furthermore, the device according to the invention is completely silent, which is a significant advantage in urban environments or in exceptional and/or protected areas.
Finally, the device according to the invention does not have any moving mechanical parts, which thus makes it possible to reduce both the operating sound level and the wear on the components and risk of fluid leaking from dynamic sealing gaskets; the device according to the invention is more reliable.
It is also more robust due to its entirely autonomous operation that automatically adjusts to the external insolation and temperature conditions. As it does not have any control/command and/or electronic control components, it has a very long service life; the reactive composites used in the reactors of the device according to the invention have been tested over more than 30,000 cycles (corresponding to approximately 80 years of daily operation) without any loss of performance being observed.
By way of non-limitative examples, the refrigerant can be selected from water, ammonia, ethylamine, methylamine or methanol, and the solid reagent can be selected for example from calcium chloride (CaCl2), barium chloride (BaCl2) or strontium chloride (SrCl2). More generally, the device according to the invention preferably uses a refrigerant other than hydrochlorofluorocarbons and chlorofluorocarbons, which deplete the ozone layer and contribute to global warming.
The phase-change materials used in the present invention to efficiently store the refrigeration produced by solidifying are preferably organic or inorganic compounds. By way of non-limitative examples, they can for example be water, an aqueous solution or a paraffin.
The means for controlling the flow of the refrigerant advantageously make it possible to regulate said flow passively, solely as a function of the pressure differences prevailing between the reactor, the condenser, the evaporator and the first and second tanks during the day-time regeneration and night-time refrigeration phases.
Advantageously, the enclosure and/or the second tank can be thermally insulated in order to reduce the energy requirements necessary to maintain the temperature inside and maintain a liquid refrigerant temperature lower than the ambient temperature during the day, thus preventing the temperature of the refrigerant contained in the evaporator from increasing over the course of the day.
Preferably, the evaporator can be supplied with liquid refrigerant from the second tank by the difference in density of said refrigerant between the inlet and outlet of said evaporator. This thermosyphon operation makes it possible generate a flow of refrigerant between the second tank and the evaporator without a pump and without an external energy supply, thus enhancing the autonomy of the device according to the invention.
Preferably, the reactor can also comprise an isothermal housing arranged to contain the heat exchanger and/or the reactor and capable of reducing the heat losses of said reactor, particularly by conduction. The insulation may be obtained by any known insulating means that withstands the temperature variations to which the reactor is subjected during the course of the night and the day, such as for example glass wool or rock wool.
Advantageously, the reactor can be made up of a plurality of tubular elements comprising the solid reagent and connected to each other by said means of conveying the refrigerant in order to make maximum use of the solar radiation and optimise the heating of the reactor. It is advantageous to maximise both the solar absorption area and the orientation of said reactor in relation to the sun. The tubular element configuration thus makes it possible to maximise both the active area of the reactor and the direct incidence of the sun on said reactor.
Preferably, the plurality of tubular elements can be coated with a solar-absorbing coating to improve the thermal efficiency of the plurality of tubular elements, said coating being in close contact with the wall of the plurality of tubular elements.
By way of non-limitative examples, the coating can be a simple solar paint or a metal film (copper, aluminium, etc.) with good thermal conductivity, placed in thermal contact with the wall of the tubular elements and on which a selective thin layer can be deposited.
Advantageously, the solar-absorbing coating can have low infrared emissivity.
According to a particular embodiment, the reactor can also comprise at least one covering element transparent to solar radiation, arranged to reduce heat losses and maximise solar collection efficiency, said at least one covering element extending beyond the surface of the reactor exposed to the sun.
Optionally, the at least one covering element can also be opaque to infrared radiation in order to enhance the greenhouse effect.
Preferably, at least one of the surfaces of the reactor not exposed to the sun can be thermally insulated to reduce heat losses. The insulation may be obtained by any known insulating means, such as for example glass wool or rock wool.
According to a particular embodiment, the reactor can also comprise actuation means in order to orient the plurality of tubular elements of the reactor in a plane substantially perpendicular to the direction of the sun and thus present the maximum possible solar-absorbing area, in order to optimise the orientation of the reactor and maximise the solar collection efficiency and the associated heat exchanges.
According to a first version of the device according to the invention, the night-time cooling of the reactor is provided by natural circulation of the air in the reactor, thus making it possible to achieve cooling in a totally passive manner.
Advantageously for this first version, the reactor can also comprise at least one flap for the ventilation of the plurality of tubular elements, said at least one flap being located at the top and/or bottom of said reactor.
Preferably, the at least one ventilation flap can be arranged to seal the reactor when it is in the closed position in order to enhance the heat exchanges inside said reactor.
Advantageously, the at least one ventilation flap can also comprise drive means to open/close it.
According to a first variant, the drive means can consist of a low-power electric motor.
Advantageously, the electric motor can be powered by an electricity production and/or storage device, optionally powered by photovoltaic panels.
According to a second variant, the drive means can consist of a rack and pinion device actuated by a compressed air rotary jack connected to a compressed air reserve.
Preferably, the compressed air reserve can be refilled by an air compressor powered by photovoltaic panels.
According to a third variant, the drive means can consist of a rack and pinion device actuated by a single-acting hydraulic linear jack controlled by a thermostat bulb in thermal contact with an absorbing plate exposed to the sun. This last variant is entirely passive, autonomous in terms of energy and automatically controlled.
Preferably, the plurality of tubular elements can also comprise a plurality of circular fins, the base of which is in close thermal contact with the wall of the tubular elements in order to enhance the heat exchanges.
Advantageously, the plurality of fins can be covered with a solar-absorbing coating to enhance the heat exchanges.
Advantageously, the plurality of tubular elements can be arranged horizontally in order to improve the flow of air around said tubular elements.
Preferably, the condenser can be of the finned tube type and cooled, in the day, by natural convection of the air around said finned tubes.
According to a second version of the device according to the invention, the night-time cooling of the reactor can be provided by a heat pipe loop operating as a thermosyphon and comprising:
This second version of the cooling of the device according to the invention thus makes it possible to efficiently achieve both the heating of the reactor during the day and the cooling of firstly the reactor during the night and secondly the gaseous refrigerant flooded condenser in the working fluid tank of the heat pipe loop.
Preferably, the working fluid is selected from those fluids that have a boiling temperature at atmospheric pressure of between 0 and 40° C. and that have a pressure of between 1 and 10 bar in the temperature range from 20 to 100° C. By way of non-limitative example, it can be a type C4, C5 or C6 paraffinic hydrocarbon (such as butane, methylpropane, pentane, methylbutane, dimethylpropane, hexane, methylpentane, dimethylbutane, etc.), an HFC type working fluid conventionally used in organic Rankine cycles (R236fa, R236ea, R245fa, R245ca, FC3110, RC318, etc.), an inorganic fluid (ammonia, water), or an alcohol (methanol, ethanol, etc.).
Advantageously, the device according to this second embodiment can also comprise a valve for starting the heat pipe loop, arranged to fill said heat pipe loop with working fluid and/or drain it.
Preferably, the heat pipe evaporator can comprise at least one means of conveying the working fluid arranged inside the plurality of tubular elements of the reactor and in close thermal contact with the solid reagent, said at least one means of conveying the working fluid associated with each tubular element being connected to each other by manifolds at the top and bottom.
Advantageously, the plurality of tubular elements of the reactor can be inclined vertically in order to facilitate the movement of the working fluid by simple gravity.
Advantageously, the heat pipe condenser can be made up of at least one finned tube connected to each other by means of conveying the working fluid.
Preferably, the at least one finned tube of the condenser can be arranged substantially horizontally at the rear of the reactor, with a slight tilt to enable the gravity flow of the liquefied working fluid to the working fluid tank.
Preferably, the working fluid tank can be arranged to maintain a minimum working fluid level in the means of conveying said working fluid of between one third and three quarters of the height of a tubular element of the reactor.
The working fluid tank can also be arranged to evaporate the refrigerant and also comprises the refrigerant condenser arranged to liquefy said refrigerant.
Advantageously, the device for controlling the working fluid flow in the heat pipe loop can also comprise at least one autonomous control means, arranged to respectively open and close the first and second working fluid flow control means, for example at the start of the night and the start of the day.
Preferably, the at least one autonomous control means of the first and second working fluid flow control means can comprise:
According to another embodiment of the invention compatible with each of the previous variants, the device according to the invention can consist of a modular architecture comprising:
This modular arrangement makes it possible to facilitate the implementation and installation of the device.
Advantageously, the evaporator can be of the flooded type and comprise at least one tubular element arranged to circulate the refrigerant by thermosyphon with the second tank.
Preferably, the second assembly can comprise a tight isolation valve, arranged to fill the device with refrigerant and/or drain it.
Preferably, the refrigerant can be ammonia.
According to another aspect of the invention, it is proposed that the device according to the invention be used to produce ice.
Alternatively, the device according to the invention can also be used to produce water.
Advantageously, water can be produced by condensing the water vapour contained in the air on a wall that is kept cold by the device.
Other advantages and characteristics of the invention will become apparent from the following description and from several embodiments given as non-limitative examples with reference to the attached schematic drawings, in which:
The embodiments which will be described below are in no way limitative; it is possible in particular to imagine variants of the invention comprising only a selection of characteristics described below in isolation from the other characteristics described, if this selection of characteristics is sufficient to confer a technical advantage or to differentiate the invention with respect to the state of the prior art. This selection comprises at least one, preferably functional, characteristic without structural details, or with only a part of the structural details if this part alone is sufficient to confer a technical advantage or to differentiate the invention with respect to the state of the prior art.
In particular, all the variants and all the embodiments described can be combined together if there is no objection to this combination from a technical point of view.
In the figures, the elements common to several figures retain the same reference.
The method for intermittent solar refrigeration described below and the object of the present invention is a thermochemical sorption thermal method the principle of which is based on the combination of a liquid/gas change of state of a refrigerant G and a reversible chemical reaction between a solid reagent and this refrigerant:
S
1
+G
(Gas)
⇄S
2
Q
R and G(Liq)+QL⇄G(Gas)
In the case of the synthesis reaction of the solid S2 from left to right, the refrigerant gas G reacts with the refrigerant-lean salt reagent S1 to form the refrigerant-rich salt S2. This reaction is exothermic and releases heat of reaction QR. Furthermore, the gas G absorbed by S1 is produced by evaporation of the refrigerant liquid G by absorbing the latent heat QL.
In the reverse direction from right to left, the endothermic decomposition reaction of the solid S2 requires the thermal gain QR so that the reagent S2 releases the refrigerant gas G again. It is then condensed by releasing latent heat QL.
These processes are implemented in two connected tanks that exchange the refrigerant gas G, thus forming a thermochemical dipole wherein the first tank, made up alternately of the evaporator or the condenser, is the seat of the change of state of the refrigerant G. The second tank is made up of the reactor and contains the solid reagent salt reacting reversibly with the refrigerant G.
The physico-chemical processes implemented in such a thermochemical method are monovariant and, with reference to
Ln(P)=f(−1/T)
Each of the straight lines shown in
The step of regeneration of the thermochemical dipole takes place at high pressure Ph imposed either by the reactor heating conditions during decomposition or by the refrigerant condensation conditions. Conversely, the refrigeration step takes place at low pressure Pb imposed by the reactor cooling conditions during synthesis and the refrigeration temperature Tf produced at the evaporator.
To implement this thermochemical method with a solar thermal source, the simplest device according to the invention comprises the following elements, listed with reference to
The solar refrigeration device 200 according to the invention thus involves the transformation of a consumable solid reagent arranged in a reactor 202 and operates according to an intrinsically discontinuous method. It comprises two main phases that are described below with reference to
The operation of said autonomous solar refrigeration device 200 will now be described in detail over a daily cycle.
At the start of the day, the reactor 202 is at a temperature close to the outside ambient temperature To and at a so-called low pressure Pb (point S in
When the pressure in the reactor 202 becomes slightly higher than the pressure prevailing in the first tank 208 of condensed liquid at ambient temperature To, the valve 204 opens in order to cool and condense the desorbed gas leaving the reactor 202 to the temperature Th in the condenser 207. The condensed gas is then stored throughout the day at the day-time ambient temperature To in the first tank 208 (corresponding to point C in
When, at dusk, the solar radiation is no longer sufficient, the temperature prevailing inside the reactor 202 starts to decrease, then leading to a reduction in the internal pressure of the reactor 202. The pressure differential between the reactor 202 and the condenser 207 decreases and, beyond a certain threshold, then becomes lower than the opening pressure of the valve 204. The valve then closes and isolates the reactor 202, thus preventing it from reabsorbing the steam contained in the first tank 208 at ambient temperature To. The reactor 202 is cooled to ambient temperature To, also leading to a reduction in the internal pressure thereof in accordance with its thermodynamic equilibrium (corresponding to migration from point D to point S in
Depending on the equilibria and thresholds chosen, the refrigeration temperatures Tf produced and the outside ambient temperature To, two different embodiments for the cooling of the reactor 202 are proposed and described in the paragraphs below.
As the reactor 202 cools down, the pressure thereof then also becomes lower than the pressure prevailing in the second tank 209. Advantageously, this can be thermally insulated from the outside in order to maintain the liquid refrigerant 218 contained in the tank 209 at a temperature lower than ambient temperature during the day, thus preventing the temperature of the refrigerant contained in the evaporator 212 from increasing over the course of the day. As a result, the pressure prevailing in the thermally insulated second tank 209 is lower than the pressure prevailing in the uninsulated first tank 208. The pressure decrease then enables the valve 205, when a certain pressure difference corresponding to the valve opening threshold is reached, to open, thus permitting the reactor 202 to take in and chemically absorb the gas coming from the second tank 209.
The pressure then decreases in the second tank 209 and, when the pressure difference with the first tank 208 of condensed liquid is sufficient, for example in the region of a few bar (typically 1 to 10 bar), the valve 206 opens and supplies the second tank 209 with liquid at the night-time temperature To, until all of the condensed liquid refrigerant contained in the first tank 208 has been decanted into the second tank 209 via the valve 206. As the reactor 202 continues to absorb the steam produced by evaporation of the liquid contained in the second tank 209, the decanted liquid cools until the temperature thereof is lower than the temperature of the refrigerant contained in the evaporator 212 maintained at a higher temperature by the PCM 213.
Thereafter, circulation of the refrigerant is triggered naturally, by thermosyphon, using the difference in density of the liquid refrigerant between the evaporator 212 and the second tank 209. The evaporator 212 is then supplied from the bottom 218 with liquid refrigerant that is denser than at its diphasic outlet 219. The refrigerant leaving the evaporator 212 through the diphasic outlet 219 is made up of both a liquid phase and a gaseous phase, which makes it less dense than the solely liquid refrigerant entering the evaporator 212. The steam produced in the evaporator 212 is then sucked into the second tank 209 and absorbed by the reactor 202 via the valve 205. The refrigeration is thus produced in the evaporator 212 throughout the night until sunrise, when the reactor starts to heat up; the refrigeration produced during the night is stored in the phase-change material 213 to be delivered according to the refrigeration requirements during the day.
To achieve efficient heating, the heat exchanger 201 of the reactor 202 must have the largest possible solar absorption area. According to a particular embodiment, the optimum orientation is obtained by aligning the heat exchanger 201 with the direction normal to the sun, i.e. for example tilted relative to the ground at an angle preferably corresponding to a latitude close to the latitude of the site for optimum refrigeration production throughout the year.
Such a heat exchanger 201, arranged to utilise solar radiation, will now be described with particular reference to
To utilise solar radiation to maximum effect, and according to a particular embodiment, the heat exchanger 201 is coupled to the reactor 202 and is made up of a set of tubular elements 501 comprising the solid reagent material 502. The tubular elements 501 are distributed—preferably evenly—in an isothermal housing 503, and are connected to each other by means of conveying 504—for example manifolds—and linked to the condenser 207 and/or the evaporator 212.
According to a particular embodiment, the tubular elements 501 are covered with a solar-absorbing coating 505, if possible selective, in close contact with the wall of the tubular elements 501. The solar-absorbing coating 505 has high solar absorptivity and, advantageously, low infrared emissivity.
A cover that is transparent to solar radiation 506 covering the front surface of the heat exchanger 201 exposed to the sun makes it possible to reduce heat losses by convection. Preferably, it can also reduce radiation losses and enhance the greenhouse effect, by blocking the infrared radiation emitted by reactors heated to a high temperature. Ultimately, the solar collection efficiency is maximized.
Advantageously, thermal insulation 507—for example using rock wool or glass wool—can be applied to the rear surface of the heat exchanger 201 in order to reduce heat losses by conduction and/or convection to the external environment.
The night-time cooling of the reactor 202 can be achieved according to two embodiments described below, the selection of which depends on the solid reagent 502 used in the reactor 202, the temperature of the refrigeration Tf to be produced and the night-time ambient temperature To:
Each of these two embodiments, together with all of the variants of which they are comprised, are compatible with any one of the embodiments of the invention set out above or below.
This cooling thus uses the air circulation caused by the stack effect in the reactor 202 by means of opening the ventilation flaps located at the top 509 and bottom 508 of the reactor 202.
Advantageously, to improve the heat exchanges and heat removal, the tubular elements 501 are equipped with fins 510, for example circular, the base of which is in close thermal contact with the wall of the tubular elements 501 of the reactor 202.
Advantageously, they can be arranged horizontally in order to improve the heat convection coefficient by promoting an air flow substantially perpendicular to the direction of the tubular elements 501 in the reactor 202.
Finally, in order to absorb the solar radiation more efficiently, the fins 510 can be covered with a solar-absorbing coating in a similar way to the coating that can cover the tubular elements 501.
In this first embodiment for cooling the reactor 202, the reactive gas condenser 207 can be of the finned tube type and placed at the rear or said reactor 202. It is then cooled during the day by natural convection of the air on the finned tubular elements.
Each ventilation flap 508, 509 comprises a plate 511 arranged to be airtight on the frame of the reactor 202 during the day, and a rotating rod actuated in particular at daybreak to close said flap 508, 509 and at nightfall to open said flap 508, 509.
According to an advantageous variant, the ventilation flap 508, 509 can also comprise drive means 600 arranged to rotate it by means of various devices, controlled for example as a function of the detection of daybreak or nightfall, a temperature increase (thermostat device) or a solar irradiance threshold.
Different variants of these drive means 600 are proposed and described in the paragraphs below. They are all compatible with any one of the embodiments of the invention set out above or below.
The ventilation flap 508, 509 can be driven using a low-power electric motor that is, according to an advantageous variant, supplied by an electric battery recharged by a photovoltaic collector. Typically, the power requirements are sufficiently low and brief for the area of said photovoltaic collector to be less than one square metre.
The ventilation flap 508, 509 can also be driven using a rack and pinion device that can for example be actuated by a double-acting compressed air ¼-turn rotary jack. The rotary jack is then connected to a compressed air reserve (typically 6 bar) via a 5/3 or 4/3 monostable spool valve that is actuated over a short period (momentary control lasting approximately ten seconds) as a function of the solar irradiance. The closing of the ventilation flap is actuated when the irradiance is above a first threshold (obtained close to the moment when the sun rises) and the opening of the flap is actuated when the irradiance is below a second threshold (obtained close to the moment when the sun sets). Advantageously, the first closing threshold can be greater than the second opening threshold of said flaps.
The compressed air reserve can be refilled periodically by an air compressor powered by photovoltaic panels.
The ventilation flap 508, 509 can also be driven using the device 600 described in
The thermostat bulb 611 contains a fluid 613 that is sensitive to temperature variations. More particularly, the fluid 613 is capable of vaporizing over a temperature range that is preferably between To and Th and corresponds to a pressure range compatible with the opening and closing of the ventilation flap 508, 509 that it controls. The vaporization of the fluid 613 makes it possible to pressurise the hydraulic liquid 606 contained in the hydraulic linear jack 605 by means of an accumulator 608 containing a deformable bladder 609, working in conjunction with the thermostat bulb 611 and deformed by the fluid 613.
The hydraulic liquid 606 pressurized in this way makes it possible to move both the piston 604 of the jack 605 and the rack 601, thus rotating the rod 620 of the ventilation flap 508, 509 by means of the drive pinion 602.
A return spring 603 makes it possible to push the hydraulic liquid 606 back towards the accumulator 608 when the pressure in the thermostat bulb 611 decreases following reduced exposure of the solar-absorbing plate 612.
The quantity of fluid 613 contained in the thermostat bulb 611 is defined as a function firstly of the volume of the bladder 609 pressurizing the hydraulic liquid 606 of the jack 605, and secondly of the maximum pressure to be reached to actuate the ventilation flap 508, 509, which must also correspond to an intermediate temperature Ti between To and Th and at which there is no more fluid 613 to be vaporized.
The device according to this particular embodiment is entirely passive, autonomous and automatically controlled by the intensity of the solar radiation.
In this embodiment, the reactor 202 is cooled at night and/or the refrigerant condenser is cooled during the day by a heat pipe loop. It is thus possible to transfer heat, firstly by evaporating a working fluid that has absorbed the heat released by the reactor 202 during the night-time refrigeration production phase or by the condenser 207 during the day-time reactor 202 regeneration phase, and secondly by condensing said working fluid, thus releasing the heat previously absorbed directly to the outside air via the heat pipe condenser 702.
During the night, a heat pipe evaporator 701, incorporated into the tubular elements 501, is supplied with liquid working fluid and thus cools the reactor 202 by evaporation of the liquid working fluid. The steam produced in this way condenses at night-time ambient temperature in a heat pipe condenser 702. The working fluid liquefied in this way flows by gravity into the tank 705 by means of the connection via the tubing 707 between said tank 705 and the inlet of the heat pipe condenser 702.
During the day, the heat pipe evaporator 701 incorporated into the reactor 202 is inactive due to the closing of two valves 703, 704 placed between the evaporator 701 and the condenser 702 of the heat pipe loop. The first, 703, makes it possible to control the flow of the working fluid through a liquid connection located at the bottom, while the second, 704, makes it possible to control the flow of the working fluid through a gas connection located at the top.
Thus, when the reactor 202 is heated by the sun during the regeneration phase, the pressure in the heat pipe evaporator 701, isolated in this way, increases and causes the draining of the working fluid from the bottom of the evaporator 701 in liquid form. It is then stored in a working fluid tank 705 by means of a drain line 709. Preferably, the working fluid tank 705 is arranged to store the liquid working fluid during the draining of the evaporator incorporated into the reactor. The reactor 202 is thus arranged to increase in temperature and perform its regeneration during the day.
With reference to
According to a particular embodiment, the steam 703 and liquid 704 valves close at the start of the day and open at the start of the night independently due to the action of autonomous control means the operation of which is described with reference to
The autonomous control means of the valves 703 and 704 consists of a thermostat bulb 801, heated during the day and cooled at night by an absorbing plate 802 that has high solar absorptivity, high infrared emissivity and low thermal mass. The absorbing plate 802 is preferably exposed to the sky to utilise both heating by solar radiation during the day and radiative cooling at night. The thermostat bulb 801 contains a fluid that is arranged, under the action of solar radiation, to increase the pressure in a bellows 803 and move a needle 804 on the seat of the port of the valve 703 or 704, thus closing off the passage of the working fluid. When the pressure drops in the thermostat bulb 801, by radiative cooling at the start of the night, the bellows 803 reduces in volume under the action of a spring 805 the stiffness of which can be adjusted by an adjusting screw 806. The needle 804 rigidly connected to the bellows 803 detaches from the seat of the valve 703 or 704 and then allows the working fluid to flow into the heat pipe loop.
According to a particular variant of the invention, compatible with any one of the embodiments set out in the paragraphs above, and in order to facilitate the implementation and installation of the device according to the invention, a modular design of the device according to the invention is proposed.
With reference to
The modularity of such a device makes it possible to connect a plurality of first elements 1001 to at least one second element 1002.
Of course, the invention is not limited to the examples which have just been described and numerous adjustments can be made to these examples without exceeding the scope of the invention. In particular, the different characteristics, forms, variants and embodiments of the invention can be combined with one another according to various combinations inasmuch as they are not incompatible or mutually exclusive. In particular all the variants and embodiments described previously can be combined with each other.
| Number | Date | Country | Kind |
|---|---|---|---|
| 1552396 | Mar 2015 | FR | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2016/056382 | 3/23/2016 | WO | 00 |
