CH616500A5 - Solar collector with running water - Google Patents

Abstract

The collector comprises a fibrous mat (2) through which a heat-carrying liquid flows. The upper end of the mat (2) is steeped in a reservoir of liquid (8). Application to the recovery of solar energy, particularly for heating buildings, swimming pools or for producing hot water. <IMAGE>

Description

The present invention relates to a trickling solar collector. It finds an application in the recovery of solar energy with a view in particular to the heating of buildings, swimming pools or the production of hot water.

A trickle solar collector schematically comprises a flat housing, one side of which is transparent and faces the sun, the other side, opaque, supporting a layer absorbing solar radiation and which may have a porous, granular or fibrous structure. ; a heat transfer liquid, for example water, flows through this structure.

Such a solar collector therefore does not have a conventional absorber which generally consists of a sheet on which tubes are welded or of an extra flat radiator whose face facing the sun is covered with an absorbent coating; this absorber is a major part of the cost of a conventional solar collector and its elimination therefore has a significant economic advantage.

French patent 75 32255 filed October 22, 1975 describes a sensor in which it is intended that the heat absorbing zone consists in particular of fibers inserted between two plates, one transparent, the other opaque, the coolant flowing therefore between the two plates occupying the entire volume, comprised between these plates, left free by the fibers.

The important difference between the sensor of the present invention and that of the cited patent lies in the presence of an air gap between the irrigated fibrous medium and the transparent plate. It is therefore no longer necessary to have a double transparent cover, which is detrimental to the transmission of solar radiation. However, even with a double cover, this results in a significant improvement in the efficiency of capturing solar energy by reducing thermal losses towards the front of the collector (the air gap acts as a thermal insulator) .

The present invention in fact consists in using a fibrous mat in contact with a plate constituting the bottom of the sensor; this carpet, which is separated from the transparent cover by an air space whose thickness is determined to limit the heat losses (thick enough to limit the heat losses by conduction, thin enough to limit the convection currents), is supplied with heat-transfer liquid for example by a distribution ramp (tube perforated with holes or slots) or, more favorably by a liquid retention in which the upper end of the fibrous mat soaks; the liquid then permeates the carpet and flows by capillarity and by gravity, thus achieving a homogeneous flow.

The purpose of this arrangement is to obtain a very simple, inexpensive and high-performance system.

In any case, the characteristics and advantages of the present invention will appear better after the description which follows, of exemplary embodiments given by way of explanation and in no way limiting, with reference to the appended figure which schematically shows in section an example realization of the sensor of the invention.

In this figure, the sensor shown comprises a fibrous mat 2 in intimate thermal contact with a support surface 4; the upper end of the fibrous mat, passing over a dam 6 which constitutes the retaining device, dips in a retaining 8 of the heat transfer liquid supplied by an inlet duct 10. A downstream collector 12 is provided at the lower end of the device; depending on the uses of the hot heat transfer liquid collected, it may be advisable to place a siphon on the outlet tube so as to maintain a small quantity of heat transfer liquid in the lower part of the sensor in order to avoid entrainment of air which is harmful to the correct pumping of this liquid.

Preferably, the assembly rests on an insulating support 14 and it is provided with a protective opening 16 constituted by a plate or a film transparent to solar radiation; this transparent cover is separated from the fibrous carpet by an air space preferably 2 to 5 cm thick. The assembly is inclined relative to the horizontal to allow the flow of the heat transfer fluid and better exposure to solar radiation.

The operation of this device is as follows: the heat transfer liquid, for example water, feeds the liquid retention 8 through the inlet duct 10. By capillarity, this liquid permeates the fibrous mat then flows through him, towards the lower end where it is recovered and discharged by the downstream collector 12.

Good homogeneity of the flow is obtained through the use of the distribution device (liquid retention) and the fibrous (or granular or porous) mat which plays the role of permanent liquid distributor.

To improve this liquid distribution and avoid the appearance of preferential paths, the fiber is preferably wetted before operation. This can be done automatically by arranging perpendicular to the flow several intermediate bars constituting covered reservoirs as for the device for distributing the fibrous or granular substance.

Solar radiation is absorbed in the liquid itself (in particular infrared radiation) but also, in the thickness of the fibrous structure (due to the multiple reflections on the different fibers) and possibly by the support surface. The good liquid-fiber contact ensures a very efficient heat exchange between these two bodies, due, in particular, to the microturbulences which arise in the liquid during its flow.

The transparent cover 16 is only used to create a greenhouse effect and minimize forward heat losses.

For purely explanatory purposes, the following materials can be used to make a solar collector according to the invention: the fibrous mat can be made of natural, artificial or synthetic fibers, preferably formed by a three-dimensional entanglement of fibers ("non-woven") ) in polyamide or polyes5

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ter; materials such as those used to make the scouring pads can be used in particular. The support surface can be made of rigid plastic, for example reinforced polyester or laminate. Excellent thermal contact can be obtained between the fibrous mat and the support surface by bonding. The transparent cover can be made of glass or transparent plastic or made up of a single or double heat-shrinkable film (made of polyethylene, polyvinyl chloride or fluoride). The heat transfer liquid is advantageously water and its flow rate can be of the order of 30 to 1001 / h per m2 of captive surface.

The collector described is particularly well suited to the production of solar energy recuperators intended for example for the production of hot water for holiday camps, campsites, garden showers or for swimming pools etc. For these summer applications, the solar collector will preferably be slightly inclined, the angle formed with the horizontal being between 10 and 40 ° and advantageously 25 ° in our latitudes. It can also be applied to domestic heating, in particular in the form of terrace sensors in which the fibrous or granular structure lines the surface of a slightly sloping terrace (2 to 10%) or else in the form of a sensor with a pitched roof. strong (40 to 60 degrees).

It will further be observed that the sensor described offers to the eye the surface corresponding to the fibrous carpet and that it can be colored at will to produce any desired decorative effect or to blend in with its environment. In the latter case, the carpet can be green in color, or tile or slate color.

In particular sunshine conditions such as particularly favorable summer conditions, and, for aesthetic reasons, it is even possible to remove the transparent cover, the fibrous carpet is then irrigated in the open air.

An example of embodiment of a trickling solar collector according to the invention can be the following. With a width of 1 meter and a length (direction of flow) of 2 meters, this sensor is equipped with a fibrous mat (non-woven polyamide) 1 m thick, green in color. With a liquid distribution device consisting of a 3 cm high dam, flows of 1501 / h can be achieved without spilling the liquid (water in this case) over the retaining dam. The height of the water reservoir is automatically established at a level ensuring equal supply and capillary pumping rates through the fiber.

Equipped with a double film of heat-shrunk polyethylene and inclined at 22 ° to the horizontal, yields of 2 "capture greater than 70% are obtained at midday under the following conditions:

incident solar flux: water outlet temperature outside temperature:

water flow:

useful heat recovered: capture efficiency:

543 w / m2 26 ° C 16 ° C 72 1 / h 397 w / m2 73%

1 sheet of drawings

Claims (7)

616,500 1. Solar collector with trickle comprising a fibrous zone inclined with respect to the horizontal and exposed to the solar rays, zone in which a heat-transfer liquid flows, characterized in that the fibrous zone is constituted by a fibrous carpet (2 ) one side of which is in contact with an opaque support surface (4) and the other side of which is in contact with an air space, this mat being irrigated by a heat-transfer liquid which flows by simple gravity. 2. Sensor according to claim 1, characterized in that it further comprises a device for distributing the heat-transfer liquid comprising a liquid retention (8) in which the upper end of the fibrous mat (2) is soaked. 2 3. Sensor according to claim 1, characterized in that intermediate liquid retaining devices provide an automatic re-impregnation of the fibrous mat (2). 4. Sensor according to claim 1, characterized in that the mat (2) is made of synthetic fiber. 5. Sensor according to claim 1, characterized in that it further comprises a cover (16) transparent to the sun's rays. 6. Sensor according to claim 5, characterized in that said cover (16) consists of a single or double film of heat-shrinked transparent plastic material. 7. Sensor according to claim 1, characterized in that the irrigated fibrous mat is in the open air, without cover.