US20060124276A1

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Publication number: US20060124276A1
Application number: US10/544,240
Authority: US
Inventors: Paul Curtis; Robert Curtis; Rosa Delaney
Original assignee: PANEL IP Pty Ltd
Current assignee: PANEL IP Pty Ltd
Priority date: 2003-02-05
Filing date: 2004-01-28
Publication date: 2006-06-15
Also published as: WO2004070281A1; EP1595098A4; AU2003900506A0; EP1595098A1

Abstract

The present invention discloses a solar array cell (15) able to be used both thermally and photovoltaically, together with an array (3) formed from a plurality of the cells (15). A solar energy system for a building which incorporates the array (3) is also disclosed. Each cell (15) is formed from an air duct (16) of parallelogram cross-sectional shape which makes for easy sealing between ducts and a reliable water shedding arrangement for the cells of the array. An air/liquid heat exchanger (35) for a solar hot water supply is also disclosed.

Description

FIELD OF THE INVENTION

The present invention relates to a solar energy system and, in particular, to a solar energy system for use in buildings which enables hot air to be generated for space heating, with the optional addition of either heat to be generated for hot water heating, and/or electricity to be generated from photovoltaic cells, or both.

BACKGROUND ART

It has long been known to provide solar collectors on the roofs of buildings for the purpose of heating hot water and such collectors are well known, and generally unsightly, additions to the roofs of many buildings. This is particularly the case in Australia where solar radiation levels are relatively high. Similarly, it is also well known to provide photovoltaic cells for the generation of electricity from solar radiation and such cells are in widespread use, particularly in rural and outback Australia in locations remote from power generation stations. In particular, in recent years such installations have been favoured over the costs of maintaining lengthy power transmission lines.

Hitherto, if the owner or designer of a building wished to utilize any two, or all three, of the above described systems, then individual stand alone systems would be installed which would not in any way co-operate with each other. Thus, for example, the collectors for heating hot water would be entirely separate installations from the photovoltaic cells used to generate electricity.

OBJECT OF THE INVENTION

The object of the present invention is to overcome the abovementioned disadvantage and provide a solar energy system which provides space heating and, if desired, either or both of heating and electricity generation can be integrated within the one overall system, and thereby utilize common component parts.

SUMMARY OF THE INVENTION

In accordance with a first aspect of the present invention there is disclosed an air duct having a thermal solar absorber formed on one (upper) surface of said duct and in thermal communication with the interior of the duct, said absorber having a transparent pane through which said duct upper surface can be illuminated by solar radiation with a stagnant atmosphere between said pane and said duct upper surface, wherein said pane and said duct upper surface are substantially co-extensive, said duct has at least one inlet and at least one outlet, the periphery of said pane substantially overlies said inlet(s) and outlet(s), and the intended flow of air through said duct below said pane is substantially unidirectional.

In accordance with a second aspect of the present invention there is disclosed a modular set of a plurality of the above described air ducts each having a connection to permit same to be connected in series, or in parallel, or both.

In accordance with a third aspect of the present invention there is disclosed a solar energy system for a building having an exterior surface exposed to solar radiation, said system comprising a plurality of the abovementioned air ducts mounted on said surface to receive said solar radiation, and an air/liquid heat exchanger in thermal communication with at least one duct interior and connected with at least one heat absorbing load.

In accordance with a fourth aspect of the present invention there is disclosed a building having installed therein the abovementioned solar energy system.

In accordance with a fifth aspect of the present invention there is disclosed a method of sealing adjacent air ducts in an array of air ducts forming a thermal solar collector, said method comprising carrying out, not necessarily in sequence, the steps of:

(i) inclining to a substantially like extent at least one pair of adjacent side walls of at least one pair of said ducts,

(ii) locating an opening in each said adjacent side wall,

(iii) aligning said openings,

(iv) interposing between said adjacent side walls a strip of resilient material which extends in a loop around the periphery of each said opening, and

(v) moving one of said pair of ducts vertically with respect to the other of said pair of ducts to thereby generate a compressive horizontal component force which compresses said strip to thereby seal said openings.

In accordance with a sixth aspect of the present invention there is disclosed a method of joining cells in an array of solar thermal absorber cells in a water shedding arrangement on an inclined roof, said method comprising the steps of:

(i) forming each said cell with a transparent upper surface which is substantially co-extensive with said cell,

(ii) forming an overlap portion at one longitudinal edge of each said cell,

(iii) arranging said cells in columns and rows to form said array on said inclined roof with said one longitudinal edge lowermost, and

(iv) overlapping said one longitudinal edge of each cell with the opposite longitudinal edge of the longitudinally adjacent cell.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will now be described with reference to the drawings in which:

FIG. 1 is a plan view of a prior art thermal solar collector used to provide hot air for space heating,

FIG. 2 is a transverse cross-section taken along the line II-II ofFIG. 1.

FIG. 3 is a schematic perspective view of a building which has installed therein the integrated solar energy system of a first embodiment,

FIG. 4 is a perspective view of the solar collector array incorporated in the system ofFIG. 1,

FIG. 5 is a perspective view of a single modular duct unit used in the array ofFIG. 4 and incorporating a thermal solar absorber in its upper surface,

FIG. 6 is a partial transverse cross-sectional view through a number of the ducts ofFIGS. 4 and 5 showing the side by side interconnection of the ducts,

FIG. 7 is a partial longitudinal cross-sectional view through the collector array ofFIG. 4 showing how the upper surface of the absorbers are overlapped so as to provide a water shedding arrangement,

FIG. 8 is a schematic circuit arrangement of the integrated solar energy system of the first embodiment showing the possible flows of hot air, hot water and electricity,

FIG. 9 is a schematic diagram illustrating the compact nature of an integrated system of a second embodiment, and

FIG. 10 is a schematic circuit arrangement of the embodiment ofFIG. 9.

DETAILED DESCRIPTION

As illustrated inFIGS. 1 and 2, conventional thermal solar absorber for heating hot air take the form of acollector box200 having aglass top201,side walls202 and aninsulated base203. Located within thebox200 are two opposed

sheets

205,206 generally formed from profiled roofing material. The opposed profiles define a number of

parallel ducts

210,211,212, . . .219 which are joined end to end by U-shaped insulatedmanifolds220 located exterior of thecollector box200. As indicated by arrows inFIG. 1, a serpentine flow path is created with air flowing through each of the

ducts

210,211,212, . . .219 in sequence between aninlet225 andoutlet226.

Located between theglass top201 and theupper sheet205 is a stagnant air space which insulates the

ducts

210,219. Theupper sheet205 forms the heat absorbing surface.

This prior art arrangement suffers from various efficiency disadvantages including that the area of the actual ducts (210,211,212, . . .219) is less than the area of theglass top201. The prior art arrangement also suffers from a number of constructional disadvantages in that eachmanifold220 must be sealed to the corresponding ends of the corresponding ducts. There should also be reasonable sealing between adjacent ducts such as210 and211. In addition, theentire box200 needs to be mounted somewhere on a building, for example on the roof of the building, where it receives solar radiation but inevitably also forms a readily observable eyesore. Furthermore, where a number ofsuch boxes200 are to be connected together, for example in series or in parallel, then theinlets225 andoutlets226 must be joined together by appropriated insulated manifolds (not illustrated) similar tomanifolds220.

It follows from the foregoing that if an unobtrusive collector is to be formed without the inherent deficiencies of the collector ofFIGS. 1 and 2, then an entirely new approach to collector construction was required. Furthermore, as will be apparent from the following description improvements in various aspects of the solar energy system other than the collector, enable an improved overall system to be provided.

Turning now toFIG. 3, for a new building1 an integrated system can be installed during construction, in particular during construction of theroof2 upon which asolar collector array3 is installed. In addition, during construction a piping array6 in this embodiment is installed in the floor5 which is intended to carry water for the purposes of either heating or cooling the floor5 and thus moderating the temperature of theinterior7 of the building1. Theinterior7 is also provided withair outlets51 andinlets52 to enable theinterior7 to be heated.

The floor5 is located above a foundation9 within which is located a corrugatedmetal water tank10, or most preferably an in ground tank fabricated from concrete (not illustrated) the primary function of which is to store potable water. However, thetank10 having been purchased can also be used to constitute a reservoir of cold water. The building1 is also provided with ahot water service11, which is essentially an insulated water tank, and aheat source12 which in the preferred embodiment is a reverse cycle air conditioning system, but which could merely be a fuel burning heater such as a wood stove, gas or oil fired heater, an electric heater, or similar. Aheat bank50 is also provided. Thehot water service11,heat source12, andheat bank50 can be located either outside the building1 (as illustrated), or inside the building, or under its floor5 as desired.

Thesolar collector array3 ofFIG. 3 is formed from a number ofindividual cells15 each of which is essentially alike. Thecollector array3 is illustrated in more detail inFIG. 4 and the individual collector cells themselves are illustrated in more detail inFIGS. 5 and 6.

It will be apparent fromFIGS. 4-6 that each of theindividual collector cells15 is fabricated as atubular air duct16 having anabsorber17 formed on its upper surface. Theair duct16 is preferably formed from pressed sheet metal and, as best illustrated inFIG. 6, has a transverse cross-sectional shape which is a parallelogram which thereby enables theair ducts16 to be nested side by side as illustrated inFIG. 6. As also illustrated inFIG. 7 the longitudinal cross-sectional shape is also a parallelogram which enables theair ducts16 to be nested end-to-end as seen inFIG. 7.

The sheet metal from which eachair duct16 is fabricated, is preferably pressed so as to provide two potential transverse openings18 (FIG. 5) and two potentiallongitudinal openings19. Depending upon the intended configuration of thecollector array3 and the intended direction of air flow therethrough, so

individual openings

18,19 are pressed out, or left in situ, prior to assembling thecollector array3.

The upper surface of eachcollector cell15 can be formed either as a photovoltaic array21 (FIG. 4) or as a solarthermal collector22. Thethermal collector22 essentially takes the form of an upper sheet orpane23 of glass, polycarbonate or similar transparent material which is spaced from a lower sheet24 (FIG. 6) which is preferably formed from the metal of theair duct16. Thelower sheet24 of thecollector22 forms the upper interior surface of theair duct16. Thesheet24 is preferably treated. The most simple form of treatment is for the upper surface of thesheet24 to be painted black. The most preferred form of treatment is for the upper surface of thesheet24 to be coated with a material which absorbs heat and for the lower surface of thesheet24 to be coated with a material which re-emits heat to the air within theduct16. An insulatingbead25 extends around the periphery of each of theupper sheets23 thereby forming a sealed stagnant air volume between theupper sheet23 andlower sheet24.Such beads25 are known per se from the fabrication of double glazed windows. Solar radiation incident on theupper sheet23 passes therethrough and heats thelower sheet24 which in turn heats the air in the interior of theduct16.

As best seen inFIGS. 5 and 6, thelower sheet24 is formed into asingle ridge27 on one side of thecell15 and into an invertedU-shaped channel28 on the other side of thecell15. Theridges27 andchannels28 are shaped so as to enable the cells to be slidingly engaged as illustrated inFIG. 6 with aridge27 of onecell15 located interior of thechannel28 of theadjacent cell15.

As seen inFIGS. 5 and 6, thebase26 of theduct16 is provided with aflange29 through which the shank of a conventional fastener (not illustrated) can pass vertically so as to secure the base26 to a conventional timber rafter or batten31 (FIG. 7). Thus as seen inFIG. 6, theleft hand duct16 is first secured and then eachduct16 is secured in turn progressively working to the right as seen inFIG. 6 (and the lower-most row first, and then the next highest row next, as seen inFIG. 7).

The air flow passages which extend between theindividual collector cells15 are preferably sealed by means of single sided adhesive, resilient foam tape20 (illustrated in phantom inFIG. 5) which is located around each of the punched out

openings

18,19. In this way escape of heated air from thesecells15 is prevented. This sealing action is facilitated by the transverse and longitudinal cross-sectional shapes of theducts16 each being a parallelogram. As a consequence of this shape, the downward vertical force exerted via the fasteners passing throughflange29 results in the side wall of one duct which lies above the side wall of the adjacent duct, exerting a downward force and thereby generating a horizontal component force which compresses thefoam tape20 interposed between the adjacent side walls by virtue of thetape20 extending around the periphery of the punched out

openings

18,19. As a consequence, during the installation procedure, adjacent ducts are sealed. In this connection it should be borne in mind that pressure differences between the interior and exterior of theducts16 are generally low (being generally only a fraction of an atmosphere).

Finally, as illustrated inFIG. 6, the exterior surfaces of thecollector array3 are preferably insulated with aconventional insulation layer30. Thermal insulation betweenadjacent duct cells16 is, in general, not required.

As best seen inFIG. 4, thesolar collector array3 is provided with input and

output ducts

32,33 which connect to the remainder of the solar energy system to be described in relation toFIG. 8. The input and

output ducts

32,33 illustrated in solid lines inFIG. 4 are those preferably used with, for example, a cathedral ceiling. For conventional ceilings the solid line input and

output ducts

32,33 may interfere withrafters31 so the input and

output ducts

32,33 illustrated in dotted lines inFIG. 4 are used providing entry and exit of air through apertures (not illustrated) formed in thebase26 of theducts16.

As also seen inFIG. 4, fabricated together with thesolar collector array3 is aheat exchanger35 for liquids formed from an array ofcopper pipes36 which pass through preformedapertures37 as best seen inFIG. 5. As will be explained hereafter, water is passed through thepipes36 of theheat exchanger35 and is heated by the hot air present within theinterior38 of thecells15.

Turning now toFIG. 8, the integrated solar energy system of the first embodiment will now be described. Asolar collector array3 essentially the same as that ofFIGS. 3 and 4 is provided. Theparticular array3 ofFIG. 8 has threephotovoltaic cells21 which are shown as being connected in series with adiode39 and abattery40 or equivalent. These are intended to schematically illustrate the electrical supply system powered by thephotovoltaic cells21 and used to charge thebattery40. It is to be understood that thebattery40 is merely indicative of the destination for the generated electricity. Instead of a battery40 a grid interactive inverter can be used. Furthermore, in order to ensure that thosecells15 havingphotovoltaic cells21 are cooled to a maximum extent, these cells should be positioned first, or at least early on, in the flow of air through the array3 (that is, thecells21 should preferably be adjacent the input32).

In addition, the hot air/liquid heat exchanger35 is connected via apump42 andvalve107, with a heat exchanger in thehot water service11. Thus the liquid in theheat exchanger35, and the potable water in thehot water service11 do not mix. This enables anti-freeze, or similar, to be used in theheat exchanger35, if desired. In addition, at night thepump42 can be turned off to save power thereby allowing the liquid to drain from theheat exchanger35. Furthermore, theheat exchanger35 is not subjected to the relatively high liquid pressures of the building potable water supply. During daylight hours, when thecollector array3 is generating heat, hot liquid passes from theheat exchanger35 to heat thehot water service11. During the winter months, hot water is also passed viavalve108 to the piping array6 which heats the floor5 of the building1. However, in the summer months, thevalve108 is closed and anothervalve109 is opened thereby allowing apump43 to circulate cold water from the underfloor water tank10 through the piping array6 to thereby cool the floor5.

Turning now to the hot air flow, aheat bank50 is provided which preferably takes the form of individual wax “candles”55 each located within its own tubular plastic housing, the wax undergoing a phase change at typically approximately 40° C. The wax stores heat when passing from a solid to a molten condition and gives out heat when passing from a molten to a solid condition. Other phase change materials including mineral salts can also be used. Theheat bank50 is connected via a blower orfan44 and dampers or valves101-106 with thearray3,hot air outlets51 which lead into theinterior7 of the building1, anair inlet52 from theinterior7, and theheat source12.

When thesolar collector3 is producing heat, hot air passes from theoutput duct33 viavalve101 to theheat bank50 and then passes via the blower orfan44 throughvalve104 to theinput duct32. This flow of air fundamentally stores heat within theheat bank50 for use at a later time. In addition, during the winter months, if desired,valve105 can be manipulated so as to allow some of the hot air from theoutput duct33 to pass into theinterior7 of the building via thehot air outlets51. This provides day time heating. During the night time, and at other periods when thesolar collector array33 is not being heated, thevalve104 is closed and the

valves

102 and105 are opened thereby allowing air heated by theheat bank50 to circulate through theair inlets52, thevalve102, theheat bank50, thevale105 and thehot air outlets51.

For those occasions, such as periods of extended rainfall during winter, where an external heat supply is required, thevalve106 can be opened thereby enabling theheat source12 to supply hot air directly to theheat bank50.

Turning now toFIGS. 9 and 10, a second embodiment of the present invention is illustrated and which is particularly suitable for installation in existing buildings. In all installations it is desirable that the various components of the system be compactly located relative to each other since the volume occupied by the installed equipment should preferably be as small as possible. However, in new buildings there is generally more scope for changing the building itself to better suit the overall system whilst in existing buildings the building itself is generally not changed to minimize expenditure. The second embodiment illustrated inFIGS. 9 and 10 makes this minimization of expenditure possible.

InFIGS. 9 and 10, thecollector3,building interior7 andheat source12 are essentially as before. However, the remaining components to supply hot air can be located within thecabinet50 used primarily to house the heat bank “candles”55. In the embodiment illustrated inFIGS. 9 and 10, thesolar collector array3 only provides hot air so no hot water is provided nor is any electricity generated. The various flow paths for heated air inFIGS. 9 and 10 are essentially as explained above in relation toFIG. 8. However, the compact geometrical relationship of the system components is apparent fromFIG. 9.

It will be apparent to those skilled in the art that the above described solar energy system provides hot air for space heating and, if desired, enables the simultaneous provision of electrical energy, and/or heat for hot water. Because the system is integrated, the overall cost is reduced relative to three individual systems because of the utilization of common components. Furthermore, aesthetically thesolar collector array3 is quite unobtrusive and can combine solar thermal absorbers and photovoltaic cells in an aesthetically pleasing manner. Further, the modular nature of the array and the sealing of the individual cells of the array make for both inexpensive construction and quick and inexpensive installation.

In addition, because thephotovoltaic arrays21 have their lower surfaces cooled by the extraction of heat into the correspondingducts16, the electrical output of thephotovoltaic arrays21 is increased.

The foregoing describes only some embodiments of the present invention and modifications, obvious to those skilled in the art, can be made thereto without departing from the scope of the present invention. For example, the number of cells in thearray3 ofFIG. 2 can be 4×4 or 3×5 or other such combinations and not just the 3×4 combination illustrated.

The term “comprising” as used herein is used in the inclusive sense of “including” or “having” and not in the exclusive sense of “consisting only of”.

Claims

1. An air duct having a thermal solar absorber formed on one (upper) surface of said duct and in thermal communication with the interior of the duct, said absorber having a transparent pane through which said duct upper surface can be illuminated by solar radiation with a stagnant atmosphere between said pane and said duct upper surface, wherein said pane and said duct upper surface are substantially co-extensive, said duct has at least one inlet and at least one outlet, the periphery of said pane substantially overlies said inlet(s) and outlet(s), and the intended flow of air through said duct below said pane is substantially unidirectional.

2. The duct as claimed inclaim 1 and having connection means to permit said duct to be connected either in series, or in parallel, or both, with like ducts.

3. The duct as claimed inclaim 2 and having a transverse cross-sectional shape which is a trapezium.

4. The duct as claimed inclaim 3 wherein said transverse cross-sectional shape is a parallelogram.

5. The duct as claimed inclaim 4 wherein said connection means includes fasteners having a substantially vertically extending shank which, when tightened, exert a horizontally extending force component on said inlet or outlet.

6. The duct as claimed inclaim 1 and including an air/liquid heat exchanger in thermal communication with the duct interior.

7. The duct as claimed inclaim 6 wherein said air/liquid heat exchanger comprises a thermally conductive pipe passing through said duct interior.

8. The duct as claimed inclaim 6 wherein said liquid is water.

9. A modular set of a plurality of air ducts each being as claimed inclaim 2.

10. The set as claimed inclaim 9 wherein each said duct is shaped to mate with like ducts to thereby form an array.

11. A solar energy system for a building having an exterior surface exposed to solar radiation, said system comprising,

a plurality of air ducts as claimed inclaim 2 and being mounted on said exterior surface to receive said solar radiation, and

an air/liquid heat exchanger in thermal communication with at least one duct interior and connected with at least one heat absorbing load.

12. The system as claimed inclaim 11 wherein said air ducts are connected in an air flow path which includes at least one hot air outlet located in the interior of said building.

13. The system as claimed inclaim 12 wherein said air flow path includes a heat bank.

14. The system as claimed inclaim 13 wherein said air flow path includes an external heat source.

15. The system as claimed inclaim 14 wherein said external heat source is connected with said heat bank.

16. The system as claimed inclaim 15 wherein said external heat source is selected from the group consisting of a fuel burning heater, an electric heater, and a reverse cycle air conditioner.

17. The system as claimed inclaim 11 wherein said heat absorbing load comprises a hot water service.

18. The system as claimed inclaim 11 wherein at least one of said air ducts is modified to replace the thermal solar absorber thereof with a photovoltaic collector.

19. A method of sealing adjacent air ducts in an array of air ducts forming a thermal solar collector, said method comprising carrying out, not necessarily in sequence, the steps of:

(ii) locating an opening in each said adjacent side wall,

(iii) aligning said openings,

20. The method as claimed inclaim 19 comprising the further step of:

(vi) fixing said other duct and moving said one duct relative to said fixed duct.

21. The method as claimed inclaim 19 comprising the further step of:

(vii) inclining all sides of all said ducts to said substantially like extent to permit openings extending in the row direction, or the column direction, of said array to be sealed.

22. A method of joining cells in an array of solar thermal absorber cells in a water shedding arrangement on an inclined roof, said method comprising the steps of:

(ii) forming an overlap portion at one longitudinal edge of each said cell,

23. The method as claimed inclaim 22 including the step of:

(v) forming a rebate in said lowermost longitudinal edge to receive therein the opposite longitudinal edge of the adjacent cell.