WO2000012944A1

WO2000012944A1 - A solar energy collector

Info

Publication number: WO2000012944A1
Application number: PCT/SE1999/001342
Authority: WO
Inventors: Bengt Freij
Original assignee: Bengt Freij
Priority date: 1998-08-27
Filing date: 1999-08-06
Publication date: 2000-03-09
Also published as: AU5888699A; SE9802874L; SE9802874D0

Abstract

A solar energy collector includes a heat exchanger (10) which extends over an external wall of a building and includes at least two throughflow passageways (121, 122) for heat transporting fluid, for instance air. The passageways (121-124) are delimited by sheets (12, 13, 14, 32, 33) which are mutually spaced in a direction perpendicular to the exposed surface of the heat exchanger, such that the throughflow passageways (121-124) are mutually separated in said perpendicular direction. The wall sheets defining said throughflow passageways (121-124) have an adapted transparency for selective distribution of incident radiation energy, such as thermal energy, to different passageways. Some (31-34) of the sheets defining said passageways are corrugated.

Description

A SOLAR ENERGY COLLECTOR

The present invention relates to a solar energy collector of the kind defined in the preamble of the accompanying Claim 1.

The invention thus relates to a solar energy collector that includes a heat exchanger which has at least two throughflow passageways for conducting a heat transport fluid and which may extend over part of an external wall of a building.

EP 0 067 732 teaches an external wall of a building that is constructed from hollow concrete blocks which include vertical and vertically connected passageways. Solar radiation heats the external wall and air circulating through the passageways in the blocks absorbs the heat and conducts it into the building interior.

One drawback with such known external wall solar energy collectors is that the outer surface of the collector must be heated to a relatively high temperature, meaning that the incident radiation energy is quickly cooled away to the ambient air by convection. It is also difficult to obtain a long delimitation line with respect to the free cross-section of the passageway in relation to its cross-sectional area, which restricts heat transfer efficiency. Thermal inertia is also high.

The object of the present invention is to provide an exterior heat exchanger with which the aforesaid drawbacks are eliminated or partially reduced, and with which the attemperating energy requirement of a building can be ensured by creating the best possible interior climate regardless of the time of the year in an attemperated climate.

This object is achieved with a solar energy collector according to the accompanying independent Claim 1.

Further embodiments of the invention will be apparent from the dependent Claims.

The inventive heat exchanger finds general use and is beneficial by virtue of providing an inner distribution between heat exchange passageways that are separated in the direction of the incident solar energy, i.e. in a direction perpendicular to the passageway-forming sheets or slabs of the heat exchanger.

Figuratively speaking, one particular embodiment of the invention can be considered to be based on the concept of constructing an external wall of the building in a manner to satisfy the requirement of effective heat insulation in order to achieve an attemperated interior climate, wherewith the outer side of the external wall is constructed over a relatively large area with a heat exchanger that includes a plurality of essentially transparent sheets disposed parallel with the outer surface of said wall. Surface-spread throughflow gaps are formed between these transparent sheets, said gaps being formed to permit the vertical throughflow of air. Air that is introduced into these passageways can then be heated by incident solar energy, which is thus first converted to heat in the essentially transparent walls of the passageway and then transferred by convection to the vertically through-flowing air. The incident solar energy can be distributed appropriately to the various passageways, by adapting the transparency of the sheets that include said passageways. As will be understood, the innermost wall of the innermost passageway can be made opaque, for instance may be black in colour, whereas the outwardly-lying passageway- forming sheets must be transparent to some extent. For instance, the transparency of the wall sheets may be chosen so that solar energy will be absorbed mainly by the heat- exchanger passageways that lie closest to the external wall of the building, while the outermost heat-exchanger passageway for instance serves mainly to form in an outward direction heat insulation in winter conditions for those passageways that lie inwardly thereof.

The outermost sheet, which is preferably fully transparent, is preferably constructed as a heat insulator. The innermost sheet is also preferably constructed as a heat insulator. A heat insulating sheet may be comprised of a corrugated foil structure that includes two mutually separated, plane- parallel foils and a corrugated or undulating foil located therebetween and connected to said planar foils at its peaks/troughs. The corrugated structure is conveniently orientated so that the resultant passageways will extend horizontally, therewith restricting convection losses.

The intermediate sheets of the heat exchanger may be alternating planar sheets and undulating sheets (corrugated sheets) so as to form a corrugated structure that includes vertically orientated channels through which cooling air can be passed. The heat captured by the heat exchange fluid/the air can be conducted into the building interior and therewith contribute towards heating the building, at least in winter. If the building requires no heat supplement during part of the year, the heat exchange passageways can be closed so as to enclose the air, wherewith the heat exchanger provides effective additional insulation for the external wall of the building.

It may be desirable in summertime to restrict the inflow of solar energy through the external wall and into the interior of the building. This can be achieved by conducting the air circulating through the heat exchanger and heated therein to the surroundings.

The invention will now be described in more detail by way of example with reference to the accompanying drawing, in which

Fig. 1 is a schematic vertical section view of a building whose external wall is provided with an inventive solar energy collector; and

Fig. 2 is a schematic horizontal sectional view of a variant of the collector shown in Fig. 1.

Illustrated in Fig. 1 is a building 1 whose external walls 2, roof 3 and floor 4 are thermally insulated. Provided on an external wall 2 that is exposed to radiation from the sun 30 is a heat exchanger 10 which extends over a substantial part of the area of said external wall 2. In the illustrated case, the heat exchanger 10 includes five essentially transparent and generally planar sheets 11, 12, 13, 14, 15 which extend in mutually parallel, spaced relationship and which are also parallel with the surface of the external wall 2. Surface extended passageways are formed between the sheets 11-15.

A bottom collecting box 25 is connected to the bottom ends of the vertical throughflow passageways 121-124 and includes an inlet channel 26 provided with a valve 27. The upper ends of the passageways 121-124 (Fig. 2) are connected to an upper collecting box 20 which has a first outlet channel 23 that leads into the interior of the building 1, and a second outlet channel 21 which opens into the surrounding atmosphere. The channels 23, 21 include respective valves 24 and 22. The airflow through the heat exchanger 10 can thus be regulated by opening and closing the valves 22, 24, 27, so that the outflow is either led into the building interior via the channel 23 or is led out to the ambient atmosphere via the channel 22, or so that air is enclosed in the heat exchanger. It will be obvious to the person skilled in this art that the valve 27 may be omitted. Moreover, the valves 22, 24, 27 may be controlled by control devices 40-42 that are regulated in a known manner to sense temperature conditions and therewith establish the aforesaid operational modes. Thus, when the heat exchanger delivers a heat surplus and the building requires heating, warm air is introduced via the channel 23. When the building requires cooling, the valve 22 is opened and the valve 24 is closed, so that absorbed solar heat will be led out to the ambient atmosphere. When the heat exchanger 10 does not deliver a substantial heat surplus, all valves 22, 24, 27 can be closed, so that the heat exchanger 10 will form additional heat insulation, for the wall 2. Correspondingly, those surfaces at which the incident solar radiation energy shall be converted to heat can be chosen by appropriate selection of the degree of transparency of the sheets 12, 13, 14; 32, 33.

The transparency/opacity can be defined by virtue of the sheets/surfaces concerned having a given uniform distribution of heat-absorbent material in an essentially transparent substrate, or by virtue of the sheets being coated or covered with a radiation absorbent outer layer in delimited sub- regions.

In summertime, the radiation energy absorbed in the sheets can be carried away by air flowing through the passageways.

Fig. 1 illustrates schematically that the sheets 11, 12, 13, 14, 15 are planar and plane-parallel sheets which extend parallel with the outer surface of the wall 2, wherewith the sheet 14 may be totally opaque. Fig.1-2 shows the heat exchanger supplemented with corrugated sheets 31-34 inserted between the sheets 11, 12; 12, 13; 13, 14; 14, 25. The corrugated sheets 31 and 34 are provided with generally horizontal flutes. The horizontally separated, lateral edges of the sheets 11, 31, 12 and 14, 34, 15 respectively are mutually sealed so that the group of sheets 11, 31, 12; 14, 34, 15 will form heat insulator plates. The corrugated sheets 32, 33 are orientated with generally vertical corrugation flutes such as to form said vertical throughflow passageways 121-124 together with the sheets 12-14.

The sheets 11, 31, 12 are transparent and form an effective heat insulator for the passageways 121, 122 (and also for the passageways 123, 124 that lie inwardly thereof) in an outward direction. The innermost plate 14, 23, 15 also forms an effective heat insulating plate, which may be transparent or opaque. The embodiment illustrated in Figs. 1 and 2 is associated primarily with a climate in which the building will essentially have a heating requirement.

The central part of the solar energy collector includes at least two cooling air passageways that are separated in the thickness direction of the collector. These passageways may, in turn, be divided by corrugated sheets 32, 33, as shown. In preferred embodiments, still more passageways are provided, these passageways being separated in the thickness direction of the inner wall and screened by separate sheets corresponding to the sheets 12, 13, 14 and optionally by corrugated sheets 32, 33 placed therebetween with the corrugations extending vertically. This design enables relatively large surfaces to be readily provided for heat transfer from the heat exchanger sheets heated by solar radiation to the cooling air flow, so that the heat exchanger is able to operate effectively with the minimum risk of stagnation in the air throughflow.

Claims

1. A solar energy collector that includes a heat exchanger (10) having at least two throughflow passageways (121-124) for heat transporting fluid in the form of air, wherein the passageways are delimited by sheets (12, 13, 14, 32, 33) which are mutually spaced in a direction perpendicular to the exposed surface of the heat exchanger, such that the throughflow passageways 121-124 are mutually separated in said perpendicular direction, characterised in that at least some (12, 13, 14) of the sheets defining said throughflow passageways (121-124) have an adapted transparency for converting incident radiation energy to thermal energy, wherein the transparency of said sheets is chosen to provide distribution of the thermal energy corresponding to the energy content of the solar radiation between said throughflow passageways.

2. A collector according to Claim 1, characterised in that the passageways extend generally in mutually the same direction, and in that a distribution box (20) is provided at least at their outlet ends, wherein the distribution box (20) has a first outlet channel (23), which includes a valve (24), and a second outlet channel (21) which opens into the ambient atmosphere and which includes a valve (22).

3. A collector according to Claim 2, characterised in that an inlet distribution box (25) is connected to the inlet end of respective passageways; and in that the inlet box (25) has an inlet channel (26) which includes a valve (27).

4. A collector according to any one of Claims 1-3, characterised in that at least some of the sheets defining said passageways are corrugated or undulated sheets (32, 33) which form laterally delimited and vertically orientated throughflow passageways (121-124).

5. A collector according to any one of Claims 1-4, characterised in that the heat exchanger includes an exterior transparent heat-insulating plate (11, 31, 12).

6. A collector according to Claim 5, characterised in that said plate is comprised of two parallel mutually spaced sheets (11, 12) and a corrugated sheet (31) having horizontally orientated troughs disposed therebetween, wherein the lateral edges of the plate are sealed.

7. A collector according to any one of Claims 1-6, characterised in that the heat exchanger includes an innermost heat insulating plate (14, 34, 15).

8. A collector according to Claim 7, characterised in that the innermost plate of the heat exchanger is comprised of two parallel and mutually spaced sheets (14, 15) and a corrugated sheet (34) having horizontal troughs disposed therebetween, wherein the vertical lateral edges of the innermost plate are sealed.

9. A collector according to any one of Claims 1-8, characterised in that the heat exchanger is mounted on an external wall of a building.

10. A collector according to any one of Claims 1-9, characterised in that the sheets of said heat exchanger are orientated generally vertically; and in that said passageways are adapted for essentially vertical throughflow.