FR2522397A1 - Air flow solar collector using convection - has core of heat absorbing material permeable to air with outer glazing - Google Patents

Abstract

The flow of heat carrying traverses the solar collector body longitudinally or transversely, the body material being transparent, translucent, or opaque. A frame (1) holds the material between two grill walls, one wall (3) being oriented towards the suns rays and protected by a glazing (7). The other opposed wall (4) is at least partially permeable to air flow. Air flow penetrates the collector via an opening (9) beneath the glazing, traverses one wall, absorbs heat from the body, and exits into a housing (11). The glazing and top wall form a volume of air with decreasing transverse section, to regulate air flow.

Description

 The solar collector which is the subject of the invention is designed so that the air, vector of the heat captured, circulates essentially inside the body of the collector after having been preferably drawn outside, The body of the collector consists of transparent, translucent and / or opaque materials permeable to air, and these materials which capture the radiation transmit it directly or indirectly to the air vector of heat by convection, which is collected at the rear of the sensor.

 The advantage of this device is to reduce the temperature of the glazing through which it is received. This temperature will, depending on the perfection of the positive, be more or less close to the temperature of the outside air. heat losses due to this glazing are minimized, and the overall heat capture efficiency will approach the unit, insofar as the thermal insulation of the sensor body is well achieved, at the rear and laterally.

 This advantage comes first in the heart of winter, the conventional collectors then having very low yields, linked to the low outside temperatures and the atmospheric conditions (wind, in particular) which favor convection losses.

 The heat thus captured may be used to heat the premises, in particular by using hot air to ensure the ventilation of the premises. If the temperature of the air leaving the collectors is sufficient, it can provide heating alone. It will also be possible to use this high temperature in batteries or by other means in order to heat the e @ u of heating or domestic hot water.

 Figures 1, 2, and 3 show an embodiment of the invention. Figures 1 and 2 show an isolated sensor, seen in cross section and in plan. Figure 3 shows a set of sensors in place.

 The sensor body is constituted by a rectangular frame (1) externally insulated (2). The faces (3) and (4) of the sensor body are constituted by a grid, the meshes of which are dimensioned in order to hold in place the materials placed inside the sensor, while allowing easy passage of air.This mesh can be made of metal, plastic, or other.It can consist of a conventional mesh, an expanded metal, or an very widely perforated sheet metal.

Inside the frame, between the mesh faces are piled up the materials / intended to interpose the radiation and transmit the heat thus obtained to the air. These materials can be of a uniform nature, or on the contrary differentiated according to, for example, that 'they are more
OR Joins close to the front of the sensor.

 Figure 1 shows an embodiment in which two layers of material succeed one another, one (5) consisting of transparent materials which will allow a significant part of the reyonnais to pass (for example 70 to 80% of it), while the layer (6) will be constituted by opaque materials whose surface characteristics will be very close to the black body, and which may also be irregular (grooves, projections, etc.) thus favor the absorption of radiation and exchange by convection.

 The two layers (5) and (6) may be separated by a mesh or simply carefully placed in place during manufacture and blocked between the faces (3) and (4). Three or more layers may also be provided.

 The material used must be suitably permeable to the passage of air; it must be manufactured and put in place so that the air is forced to frequent changes of direction in order to improve the convection coefficient. the so-called Raschig rings are likely to constitute an excellent filling material, whether they are complete, that is to say closed, or open. In the case of two layers, the rings may be made of glass (or of a plastic material substantially equivalent in terms of transparency), for layer (5), the layer (6) being ribbed black rings, plastic in general.

 The face (3? Exposed 'to the solar beam is protected by a glazing (7) which delimits with it a trapezoidal section, the closed end (8) is very narrow and the other end (9) more wide open. This glazing can exceed the frame of the sensor, above the opening (9) the dimension of the spending part (10) being a function of the slope of the sensor and the metrological conditions of the site, the objective being '' best avoid the entry of rainwater or vegetable or other products.

 The opening (9) can also be equipped with a device @@, (grating, guide vanes, filters, etc.) intended to tell you about the accidental entry of water or foreign bodies. a centralized air supply will be provided from a distributor, if necessary, with a filtering system and a fan. The end (9) will then be formed.

 The air heated in the body of the sensor exits through the base (4) and is collected in a formwork (11) well insulated (12). It is then evacuated by the ducts (13). Air circulation can be ensured by a fan located downstream (not fi Jure ui gathers the air coming from the different sensor units for its use. The filtering of the alarm, if necessary, is ensured, are upstream thanks to the filter elements placed in the opening (9) and mentioned above, either downstream, in a conventional manner.

 All the constituent elements of the network will be calculated, except in special cases, in order to maintain the bodies of the sensors in slight depression.

 Figures 1, 5 and 6 show another embodiment of the invention. The air flow always crosses the body of the sensor transversely, but for a fraction only, the other fractions -of the flow passing through openings made in both sensor ends.

 Figure 4, cross section of the sensor, shows that the grid (4) of the previous case disappears and merges with the formwork (11).

 The air always enters through the opening (9). This includes a blade (15) intended to permanently dose (during assembly or during adjustment) the quantity of air which engages in the distributor (16) and then crosses longitudinally the body of the sensor to reach the collector (17). The rest of the air engages in the space between the glazing (7) and the grill (3). is partially sucked towards the body of the sensor through the screen (3), the remaining fraction leading to the collector (17) through a positive adjustment setting (18) which limits the permanent flow. The air is then collected as previously by the tubes (13) and collectors (14).

 Figure 5 shows the same sensor in horizontal view before installation. Figure 6 shows a set of sensors in place.

 In a variant of this latter embodiment, the grating (3) is replaced by a vitra3e (glass or equivalently equivalent) the fraction of the air sucked in by (3) canceling out, and the entire dressing flow by the openings (i6) and (17).

 The operation of a battery of solar collectors does not ensure, on its own, the heating of a building, even under the most favorable conditions, except at the cost of investments totally inco @@ atible with the annual savings made. The profitability of the installation requires that the sensors be combined with another source of energy. This will preferably be chosen from storable or renewable energies. A heat pump using, on the evaporator, the heat obtained by cooling the outside air, or better still cooling the air extracted from the building, or the heat extracted from seasonal storage, constitute examples of solutions using only a minimum of traditional energy.

 This combination can only be studied on a practical case.

 Or a villa with 100 m2 of living space, volume 250 m3, with G = 1 W / h.m3 located in the Perpignan region, equipped with the sensors described above, slope 33% (slope not very favorable, but which corresponds on the roof slopes of the region): with 14 m2 of catchment area.

The normally admitted air renewal will be 250 m3 / h, or approximately 18 m3 / h per m2 of sensor. The incident radiation varies from 66 kWh / m2. Month (December) to 217 kWh / m2. Month (July) for the defined slope, on average, for daytime periods, per m2, 230 W in December and 480 W in July. In fact the @ flux will vary from? 100 to 350 W in
December and from 100 to 900 W in July.

 If the catch yield were 100%, the air would heat up from 16 to 57 C in December, and from 16 to 147 C in July. In practice and with the admitted volume of fire, the average yield will be 0.8 in winter and 0.5 to 0.6 in summer. An increase in summer flow, bringing the temperature rise to 70 or 75 C will yield an average summer yield of 0.70.

 In these conditions, the air will be warmed from 13 to 46 C in December and from 13 to 52 C in July. It will always be usable in winter to ensure ventilation of the heated premises, at the cost, sometimes of a slight It will even very often provide all of the thermal needs.

 In summer, the receivers will ensure the filling of a seasonal storage facility, as well as the partial satisfaction of domestic hot water needs.

The additional heat pump will recover the calories corresponding to the cooling of the air extracted from the building from 20 to 8 C. With a performance coefficient of 4, an installed overpower of 10%, and the recovery of 75% of the compressor energy, the heat pump supply will be 0.75 x 1.1
250 x 0.34 x 12 x (1 +) = 1,230 W
4 or 836 kWh for 30 days.

The city's monthly balance sheet for the winter months (duration reduced uniformly to 30 days) is established as follows, in kWh / month, first by neglecting the preparation of domestic hot water, then by including it (rated at 200 kWh / month)
Month October Novem Decem Janvi Feb March April
Requirements 208 1,040 1,588 1,795 1,625 1,077,586 EC direction
Sensors 1 364 993 739 809 1 145 1 569 1 781
PAC 0 47 849 885 480 o 0
Deficit 100
Requirements 408 1,240 1,788 1,995 1,825 1,277,786 with EC
PA c 0 O 247 886 886 680 Q o
Deficit 163,300
These tables show that the heat pop is theoretically used 1840 or 2195 hours (at full power) depending on the case. In reality the time of @arche is much higher, due to the wasting of solar energy especially when the temperature is moderate and sunshine @ poor, and, for example 2,500 or 3,000 hours.

 The deficit is theoretically 100 or 463 kWh, and in fact about 500 or 1000 kWh per winter.

 This calculation must be completed by examining the figures during an exceptional cold period, that is (after statistical control) five consecutive days with an average temperature of +2 C, with low sunshine (1000 watts / day).

 The needs are then, for the 5 days, of 530 kWH env, and the resources of 56 + 148 = 204 kWh, with a deficit of 326 kWh. This deficit, in practice is confused with the deficit of 1000 kWh, but subject to a sufficient temperature level (preparation of hot water and heating in very cold weather).

 Under this reserve, the deficit will be easily filled by recourse to seasonal storage. The quantity of heat received by the collectors during the five summer months by radiation is 12,908 kWh. After reheating the hot water, and with a yield of 0.7 more than â 000 kWh are available for storage, and whatever the doors, even in the absence of any heat insulation, the quantity of heat necessary in order to compensate for the winter deficit will exist at the desired time.

 The interest of catts analyze (which could be redone for most sites in France) is to demonstrate the immediate advantages of a high sensor output in winter, but above all to bring out the problem posed by the temperature of the air at the exit of the # # sensors, problem linked to the efficiency, first, but also to the air flow.

However, in the example described, it is easy to vary this flow rate. By reduction, which will mean meaning, but also by increase, this resulting in no waste, since everything @ l @ heat of the air is recovered, practically up to the level (+8 C) of the average daily temperature of the coldest month (7.5 C).

 There are other means of raising the temperature of the air at the outlet of the sensors by reducing the surface of the latter by using mirrors, but these methods, already known, are not analyzed here.

 The variation of the air flow entails another important consequence linked to the speed of the air and consequently to the coefficient of heat transmission not convection.

 In the first embodiment (FIG. 1) the speed of the air is weak in the passage through the body of the sensor and the temperature of the materials will rise, favoring the losses by radiation towards the glazing. The air flow licking that -this, which recovers (in part) not only the heat received by radiation, but that which has been ah sorbed at the entrance of the radiation (loss @ optics) therefore plays a crucial role and its flow rate must be regulated, in particular by reduction pressure losses in the body of the sensor q the end @ (8).

 In the second embodiment (FIG. 4) the speed of the air in the body of the sensor, while remaining low, will be 5 to 10 times higher, and the glazing can be swept with a quantity of looks less important.

 The solar collectors described are therefore characterized by the design details already listed, but also by the advantage represented by their association with a device for recovering heat from the extracted air which, in combination with the control systems debit, to put back the optimal use.

Claims (13)

 1.- Solar air collector, characterized by this air flow  heat vector, crosses the sensor body longitudinally or  transversely, the sensor body being formed using m @ té  air permeable, transparent, translucent and / or opaque  ques, this material being blocked inside a frame (1), between  two walls, one of which (3) oriented towards radiation, is protected  by glazing (7) and the other (4) opposite (3) is at the back by  partially permeable to air flow, this flow entering the sensor  by an opening (9), between glazing and proi (3), through ersuite  wall (3) can travel the body of the sensor (5) and (6), absob-  bant, by convection the heat capré by the materials of the body  thanks to the radiation, and emerging from the body of the sensor to be re @@@  picked from a formwork (11) for the use of its heat.  2. A sensor according to claim 1 characterized, in a first  embodiment, by what the glazing creates, with the face (3) of the  sensor, an air volume of decreasing cross-section from the  port (9) towards the other end (8) causing air penetration  as regular as possible in the body (5) by the face (3), entuè  The rear face (4), also permeable to  the air allows the air to reach the waterproof formwork (11), the  cross section is gradually increasing, favoring a re  regular partition of the air flow in the sensor.  3.- Sensor according to reve-dication i characterized, in another  embodiment, by existence, at the two ends of the body of the  sensor, distributor and air collector in which the  air resistance is practically zero. Part of the air flow entered  through the orifice (9) passes into the distributor and runs longitudinally  the sensor body to reach the collector (18), the rest of the  flJx passing over the wall (3). A fraction of the air is sucked in  through the wall (3), more or less breathable, and another action leads directly to the collector after having touched the glass  age over its entire surface. The three fractions, gathered in the neck  reader, are then used as before.  4.- sensor according to claims i 2 and 3 wherein a dis  positive protection against ingress of water or foreign matter  managers is arranged in front of the opening (9) device constituted by a  extension of the glazing beyond the completed sensor body (10), or  not by a system of blading, filtering and / or regulation.  5. A sensor according to claims 1 2 and 3 in which the air supply is obtained by means of a duct network associated with a fan (possibly with a filter) and / or in which the departure and the air is produced using a similar assembly, both the rooster assembly so that the sensor body is always slightly depressed  6.- A sensor according to claims 1 2 and 3 characterized by the choice, for the sensor body of transparent and / or translucent and / or opaque materials having, per unit volume, a maximum exchange surface  7. A sensor according to claims 1 2. and 6 characterized in that the radiation strikes first, the transparent materials possibly then translucent materials, before being completely absorbed by the opaque materials.  8.- Sensor according to claims I 2 3 and 6 characterized by the choice of materials of different dimensions allowing, by the graduated resistance which they oppose to the passage of air, to optimize the distribution of the flow in the bodies of the sensor .

 9. A sensor according to preceding claims in which the material used, transparent or not, consists wholly or partly of so-called closed or open Raschig rings,  10.- Sensor according to claims 1 2 and 3 wherein the opening 9 is provided with an adjustable guide vane in order to limit and / or orient the air flow.  11. A sensor according to claims 1 and 3 in which devices d: adjustment by blading or the like, make it possible to act on the distribution of the air flow in the different paths.  12. A sensor according to claims 1 and 3 wherein the wall 3 is replaced by a transparent wall (glass or material having the same transparency), so that the air flow has only two possible paths leading to the orifices (16) and (17).  13.- Association of a set of caters produced according to one or more of the preceding claims and of a powered heat pump system, evaporators by the air extracted from the locau @ heated by the sensors, the heating being of the "to hot air ", and the flow and temperature characteristics being coordinated between the two devices in order to ensure the best overall efficiency, and to avoid wasting thermal energy.