AU599009B2 - Solar collector - Google Patents
Solar collector Download PDFInfo
- Publication number
- AU599009B2 AU599009B2 AU51542/85A AU5154285A AU599009B2 AU 599009 B2 AU599009 B2 AU 599009B2 AU 51542/85 A AU51542/85 A AU 51542/85A AU 5154285 A AU5154285 A AU 5154285A AU 599009 B2 AU599009 B2 AU 599009B2
- Authority
- AU
- Australia
- Prior art keywords
- space
- heat exchange
- secondary liquid
- tank
- heat
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Ceased
Links
- 239000007788 liquid Substances 0.000 claims description 62
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 27
- 239000006096 absorbing agent Substances 0.000 claims description 22
- 239000011521 glass Substances 0.000 claims description 10
- 238000012546 transfer Methods 0.000 claims description 8
- 235000012206 bottled water Nutrition 0.000 claims description 4
- 239000003651 drinking water Substances 0.000 claims description 4
- 238000000034 method Methods 0.000 description 4
- 238000004891 communication Methods 0.000 description 3
- 239000012530 fluid Substances 0.000 description 3
- 238000013517 stratification Methods 0.000 description 3
- 238000001704 evaporation Methods 0.000 description 2
- 230000008020 evaporation Effects 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 239000012080 ambient air Substances 0.000 description 1
- 238000009835 boiling Methods 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 230000008602 contraction Effects 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 238000009413 insulation Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 239000002991 molded plastic Substances 0.000 description 1
- 238000007639 printing Methods 0.000 description 1
- 238000007789 sealing Methods 0.000 description 1
- 210000001364 upper extremity Anatomy 0.000 description 1
- 238000013022 venting Methods 0.000 description 1
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24S—SOLAR HEAT COLLECTORS; SOLAR HEAT SYSTEMS
- F24S10/00—Solar heat collectors using working fluids
- F24S10/40—Solar heat collectors using working fluids in absorbing elements surrounded by transparent enclosures, e.g. evacuated solar collectors
- F24S10/45—Solar heat collectors using working fluids in absorbing elements surrounded by transparent enclosures, e.g. evacuated solar collectors the enclosure being cylindrical
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24S—SOLAR HEAT COLLECTORS; SOLAR HEAT SYSTEMS
- F24S10/00—Solar heat collectors using working fluids
- F24S10/30—Solar heat collectors using working fluids with means for exchanging heat between two or more working fluids
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24S—SOLAR HEAT COLLECTORS; SOLAR HEAT SYSTEMS
- F24S10/00—Solar heat collectors using working fluids
- F24S10/90—Solar heat collectors using working fluids using internal thermosiphonic circulation
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24S—SOLAR HEAT COLLECTORS; SOLAR HEAT SYSTEMS
- F24S60/00—Arrangements for storing heat collected by solar heat collectors
- F24S60/30—Arrangements for storing heat collected by solar heat collectors storing heat in liquids
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E10/00—Energy generation through renewable energy sources
- Y02E10/40—Solar thermal energy, e.g. solar towers
- Y02E10/44—Heat exchange systems
Landscapes
- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Life Sciences & Earth Sciences (AREA)
- Sustainable Development (AREA)
- Sustainable Energy (AREA)
- Thermal Sciences (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Heat-Pump Type And Storage Water Heaters (AREA)
Description
AUSTRALIA
Patents Act 1952 .599009 FORM COMPLETE SPECIFICATION
(ORIGINAL)
FOR OFFICE USE Short Title: Int. Cl: Application Number: 542/85 Lodged: Complete Specification Lodged: Accepted: Lapsed: Published: Priority: This document contains the nimendments made under -,Se:tion 49 and is correct for printing.
44 t o o 4 04 4440 4* 4 4 4 44 Related Art: TO BE COMPLETED BY APPLICANT Name of Applicant: Rheem Australia Limited .4 4 4? o sot; 4 4 4 Address of Applicant: Actual Inventor: Address for Service: Level 26, Wastpac Plaza, iGi-_ 4ri-_ Vj TT E Eo\< e_ nyuaey, r,-Ww-u Z)O- la-ea Tibor FREI Mr A W Tilley Rheem Australia Limited Brodie StreetRydalmere NSW 2116 Complete Specification for the Invention entitled: AR COLLECTOR" The following statement is a full description of this invention, including the best method of performing it known to me: This invention relates to a solar collector for a hot water sytem.
It relates more specifically to solar collectors where double concentrically walled glass tubes, selectively surface coated on the outside of the inner tube and evacuated in the spa., between the glass tubes, are used. It is specific to the type of evacuated tube collector which is open at one end and closed at the other.
It is used in conjunction with a storage tank for collecting water heated by the solar collector and the invention is applicable either in a close coupled tank and utilising the principle of thermosyphon circulation or in a remote pumped circulation system.
00 f The solar collector is of the "indirect" heat transfer type in which the (usually) potable water heated and stored in the system is not directly heated by circulation through the inner space defined by the evacuated tube absorbers but rather by exchange of heat from a heat transfer liquid which circulates within the evacuated tubes themselves.
#401 ar, It is to be assumed that usually a number of •evacuated tubes are arranged with longitudinal axes parallel, in a planar array installed at an inclined 0 4 angle in a position to receive prevailing insolation.
Solar collectors of the above described type are o 00o already well known and many solutions have been proposed concerning methods of extracting useful heat from the single open ended type evacuated tube absorber.
N 40 -2- At least one such system describes a method whereby the potable mains pressurised water is directly circulated in contact with the inner glass wall of each absorber in the array. Although this method provides relatively good heat transfer from the heated selective surface to the glass to the water, it is disadvantaged by the difficulty of sealing each tube against the pressure of the water in the system as well as by the problem of the pressure induced stress placed upon the individual glass tubes and is further disadvantaged by the fact that in the event of a single tube being broken while in service (such as by a hailstone impact), all the stored hot water in the system would be lost in a very short time and the system would be not capable of providing any further hot water until the broken tube was replaced.
Other systems already proposed describe metal tubes, for example a U-shaped tube, circulating the pressurised water through the internal space of the evacuated tube absorber. This overcomes the problem of leaking or broken tubes, but introduces the difficulty of transferring the heat absorbed by the inner glass wall to the metal tube and hence the circulating water. Although many solutions have been proposed for transferring the heat all have left room for improvement due to reasons such as excessive cost and poor heat transfer. This invention now proposes a number of useful improvements aimed at overcoming the S4: disadvantages obtaining with previously disclosed solar collectors of the generic type and in so doing St to provide a further path to the more widespread use of the potentially highly efficient evacuated tube collector in the substantial market for solar energy exploitation which exists to provide domestic hot M water.
-3 This invention consists, in a first aspect, of apparatus for transferring heat energy from an array of solar absorbers installed in an inclined parallel spaced arrangement, said absorbers being of the double glass walled single open ended evacuated tubular type, to a tank of stored water; comprising in combination:a stored water circulation circuit including a single walled heat exchanger positioned remote from said tank, and a secondary, heat transfer liquid system, including an externally heat insulated heat exchange space, through which said single walled heat exchanger passes, to contact said secondary liquid when occupying said space; and wherein said heat exchange space is axially divided into discrete sub-spaces each of which internally communicates with: S(i) an interior, secondary liquid filled, space of one solar absorber; and (ii) a secondary liquid overflow tank which is, at least indirectly, vented to atmosphere; and wherein the overflow tank is axially compartmented by weirs to correspond to the internal divisions in the heat exchange space and has the number of axial compartments so provided preferably being equal to the number of sub-spaces of the heat exchange space; and wherein the overflow tank internally communicates with the heat exchange space by a short conduit of small internal cross-sectional area from a point high in the heat exchange space to enter the overflow tank at a point of low elevation with respect to the connection point to the heat exchange space exchange space; and incorporates a liquid level control means adjustable to control the secondary liquid at a level slightly above the tops of said weirs and which is supplied from a remote source of secondary liquid.
40 4' iZ§Ei 40 -4- In a second aspect of the same invention it consists of apparatus for transferring heat energy from an array of solar absorbers installed in an inclined parallel spaced arrangement, said absorbers being of the double glass walled single open ended evacuated tubular type to a tank of stored water; comprising in combination: a stored water circulation circuit including a single walled heat exchanger positioned remote from said tank, and a secondary, heat transfer liquid system, including an externally heat insulated heat exchange space, through which said single walled heat exchanger passes, to contact said secondary liquid when occupying said space; and wherein said heat exchange space is axially divided into discrete sub-spaces each of which internally communicates with the interior, secondary liquid filled, space of one solar absorber, and (ii) a secondary liquid cverflow tank directly vented to atmospheie; and wherein the tank internally communicates with each heat exchange sub-space separately by a tube of small internal cross-sectional area from a point high in the heat exchange sub-space to enter the overflow tank at a point of low elevation with respect to the connection point in the heat exchange space; and incorporates a liquid level control means adjustable to control the secondary liquid level in the overflow tank and which is supplied from a remote source of secondary liquid.
The invention is further explained, by way of examples, with the aid of the accompanying drawings.
Figure 1 is a cross sectional elevation view and Figure 2 is a cross sectional plan view, both of a solar collector according to this invention.
i As shown by way of the figures, the invention has the following features:a. The use of a secondary liquid within each evacuated tube 1 and an attached heat exchange space 2, with enclosing heat insulation 12.
b. The use of an indirectly vented overflow tank 3 in liquid communication with the heat exchange chamber. The liquid communication means 9, is described more fully below.
c. The secondary liquid is not under mains pressure, although the hot water supply for use preferably is.
i d. The primary liquid, that is, the potable water as stored in the tank, is circulated through the heat 15 exchange space 2 within a single walled heat exchanger preferably externally finned as shown at 11.
e. The circulation of primary fluid may be by thermosyphon between the pipe 10 and a close coupled tank (not shown) or it may be by pumped circulation between the pipe and a tank located at any remote point.
f. The heat exchange space 2 and the overflow tank 3 can be made of moulded plastics material (for economical manufacture) in a single length, or assembled from smaller modules into an elongate component to suit the number of individual solar absorbers (evacuated tubes 1) in the array.
g. The heat exchange space 2 is compartmentalised by liquid tight seals 5 or divisions, so that if one evacuated tube were to be broken, only a relatively small volume of secondary heat exchange liquid would escape and the system as a whole would remain usable until such time as the broken tube could be conveniently replaced.
h. The overflow tank 3 is divided by transverse weirs 4 to compartmentalise it so that in the event of a tube breakage only a small portion of heated secondary liquid could be lost from the tank.
i. The fluid communication between the heat exchange space 2 and the overflow tank 3 is by narrow liquid conduits 9 from the top of the heat exchange i chamber to the bottom of the overflow chamber such i that each sub-divided space in the heat exchange space is kept liquid filled when the secondary liquid in it cools (such as overnight), by a suction effect achieved by volumetric contraction of the secondary liquid upon cooling. Thus the heat exchange and overflow chambers need not be interconnected such as to rely on a gravitationally induced flow from the overflow to the heat exchange chambers. This has the advantage that the thermosyphon heat loos from the heat exchange chamber to the overflow chamber is obstructed. Also the whole assembly may be constructed having a more pleasing low profile Sappearance when installed on a visible roof location.
j. Secondary liquid lost by evaporation from the overflow chamber is topped up by a cistern type arrangement in a liquid level tank 13, from either a 3 25 storage tank of secondary liquid or if, as is preferred, the secondary liquid is chosen as mains water, then the liquid level tank 13 takes its replenishment from the water-mains to keep filled to j level line 14. The liquid level tank may be rotated around joint 15 relative to the angle of inclination of the tubular absorbers when installed.
k. The secondary fluid is preferably water because this allows (according to standards of construction imposed on the industry) a single walled heat exchange 7 M_6~ 0 arrangement between the primary and secondary liquids. Also, as stated above, water is conveniently available to replenish any evaporation or leakage loss from the system.
1. The evacuated tube absorbers 1 need not be made more complicated or expensive by provision of any internal physical division since the circulation of secondary liquid within the internal space is by thermosyphon counter currents whereby cooler secondary liquid from low in the heat exchange space 2 flows into the lower part of the mouth of the evacuated tube and flows to the lower (closed) end of the tube.
J As solar heat is absorbed by the secondary liquid in till the solar absorber the liquid tends to rise to the highest point (at any transverse cross section) and then rises up the inclined upper extremity of the inner space of the solar absorber tube so creating a return current of heated secondary liquid. This effect obtains without the aid of any axially extending internal division of the solar absorber or of the heat exchange space.
Advantages of the invention described are: Evacuated tube collectors of the type, when used with water as a secondary liquid, show extended time freeze protection at -10 degrees C ambient air temperatures.
The venting of the overflow tank to atmosphere and the use of water as the secondary liquid assures that stored potable water can never reach boiling point regardless of extended periods of high intensity insolation. The temperature difference across the heat exchanger may be designed by varying liquid flow S4'- 8 resistance and/or fin area such that at the hotter end of the primary liquid flow through the heat exchange space the primary liquid temperature can be controlled degrees C (for example) lower than that of the heated secondary liquid within the heat exchange space. By this means the temperature of the stored water can be limited to a usually desirable maximum of degrees C, or less if desired. Therefore, a temperature responsive valve such as a "Sunstat" (registered trade mark) valve to cut off over-temperature primary liquid circulation, common in previous solar hot water systems, is not required in the system as here disclosed and this further assists in the important objective of economy of manufacture.
The system as disclosed has the advantage of S0 enabling thermal stratification within the storage tank to a much greater extent than is possible with other arrangements proposed, given the presence of an electrical heating element for boosting.
In systems where heat is exchanged directly across the wall or part of the wall of the storage tank, good thermal stratification of the stored heated water is not achieved. As is recognised by those skilled in the art, thermal stratification in the storage tank enables up to 10% increase in solar contribution, that is, in the proportion of solar energy input into the tank in a given time (usually on j 30 an annual basis) as a percentage of the total heat energy (solar plus electric) input.
n -9-
Claims (4)
1. Apparatus for transferring heat energy from an array of solar absorbers installed in an inclined parallel spaced arrangement, said absorbers being of the double glass walled single open ended evacuated tubular type, to a tank of stored water; comprising in combination:- a stored water circulation circuit including a single walled heat exchanger positioned remote from said tank, and a secondary, heat transfer liquid system, Si including an externally heat insulated heat exchange o space, through which said single walled heat exchanger passes, to contact said secondary liquid when occupying said space; and wherein said heat exchange space is axially divided into discrete sub-spaces each of which internally communicates with: an interior, secondary liquid filled, space of one solar absorber; and S(ii) a secondary liquid overflow tank which is, at i least indirectly, vented to atmosphere; and wherein Sthe overflow tank is axially compartmented by weirs to I correspond to the internal divisions in the heat exchange space and has the number of axial compartments so provided preferably being equal to the I number of sub-spaces of the heat exchange space; and wherein the overflow tank internally communicates with the heat exchange space by a short conduit of small internal cross-sectional area from a point high in the heat exchange space to enter the overflow tank at a point of low elevation with respect to the connection point to the heat exchange space exchange space; and incorporates a liquid level control means adjustable to control the secondary liquid at a level slightly above the tops of said weirs and which i3 supplied from a remote source of secondary liquid. -3l 0 1144 Al, -10.
2. Apparatus for transferring heat energy from an array of solar absorbers installed in an inclined parallel spaced arrangement, said absorbers being of the double glass walled single open ended evacuated tubular type to a tank of stored water; comprising in combination: a stored water circulation circuit including a single walled heat exchanger positioned remote from said tank, and a secondary, heat transfer liquid system, including an externally heat insulated heat exchange space, through which said single walled heat exchanger passes, to contact said secondary liquid when occupying said space; and wherein said heat exchange space is axially divided into discrete sub-spaces each of which internally communicates with the interior, secondary liquid filled, space of one solar absorber, and (ii) a secondary liquid overflow tank directly vented to atmosphere; and wherein the tank internally communicates with each heat exchange sub-space separately by a tube of small internal cross-sectional area from a point high in the heat exchange sub-space to enter the overflow tank at a point of low elevation with respect to the connection point in the heat exchange space; and incorporates a liquid level control means adjustable to control the secondary liquid level in the overflow tank and which is supplied from a remote source of secondary liquid.
3. Apparatus for transferring heat energy as claimed in any one of the preceding claims wherein said single walled heat exchanger is provided with thermally conductive extensions to its surface area in contact with said secondary liquid. 11
4. Apparatus for transferring heat energy as claimed in any of the preceding claims wherein said secondary liquid is potable water. Apparatus for transferring heat energy with reference to and as described in the accompanying specification and Figures 1 and 2. DATED THIS 27th Day of April 1990 4r 1 I II I 4 4, 1r RHEEM AUSTRALIA LIMITED I 4 050263 12
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| AU51542/85A AU599009B2 (en) | 1984-12-20 | 1985-12-20 | Solar collector |
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| AUPG8655 | 1984-12-20 | ||
| AUPG865585 | 1985-12-20 | ||
| AU51542/85A AU599009B2 (en) | 1984-12-20 | 1985-12-20 | Solar collector |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| AU5154285A AU5154285A (en) | 1987-06-25 |
| AU599009B2 true AU599009B2 (en) | 1990-07-12 |
Family
ID=25629289
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| AU51542/85A Ceased AU599009B2 (en) | 1984-12-20 | 1985-12-20 | Solar collector |
Country Status (1)
| Country | Link |
|---|---|
| AU (1) | AU599009B2 (en) |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| AU559223B2 (en) * | 1982-11-19 | 1987-02-26 | N.V. Philips Gloeilampenfabrieken | Solar collector unit |
| AU568826B2 (en) * | 1982-11-24 | 1988-01-14 | Solar Engineering Pty. Ltd. | Solar fluid heater |
-
1985
- 1985-12-20 AU AU51542/85A patent/AU599009B2/en not_active Ceased
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| AU559223B2 (en) * | 1982-11-19 | 1987-02-26 | N.V. Philips Gloeilampenfabrieken | Solar collector unit |
| AU568826B2 (en) * | 1982-11-24 | 1988-01-14 | Solar Engineering Pty. Ltd. | Solar fluid heater |
Also Published As
| Publication number | Publication date |
|---|---|
| AU5154285A (en) | 1987-06-25 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MK14 | Patent ceased section 143(a) (annual fees not paid) or expired |