The present invention relates to solar fluid heaters and more particularly to a curved surface absorber type solar fluid heater.

Background of the invention

¾ Solar energy collectors are special kind of heat exchangers that utilize solar radiation energy to facilitate heating of fluids. The major component of any solar system is a solar collector. The solar collector is a device which absorbs incoming solar radiation, converts it into heat and transfers this heat to a fluid flowing through the collector. In prior art systems, the heated fluid is stored in an insulated

¾ hot- fluid tank for further use thereof. In general, the solar fluid heating systems have the collector and hot fluid tank located separately from each other and accordingly such systems need excessive use of all-around insulation except solar aperture or window in order to prevent heat loss which substantially increases the cost of these devices. Moreover, separate positioning of the collector and hot fluid

¾ tank make these devices bulky, heavy and unnecessarily larger in size.

Accordingly, attempts have been made to develop various types of storage cum absorber type solar fluid heating systems. For example, in some solar fluid heating systems, a rectangular box with multiple channels within said rectangular box acts as a collector thereby having a top surface of the box acting as an absorber. ttl However, after prolonged use, most of these boxes tend to inflate, resulting into fluid leakage problems, making them unusable. In flat plate collectors (FPCs, hereinafter), fins are directly connected to top surface of the tube wherein solar radiation fall on the fins thereby facilitating absorption of the solar radiation to heat the fluid tubes and surrounding air. This in turn heats the fluid in the tubes. However, such design imposes additional ¾ thermal resistance in heat transfer process increasing heat loss coefficient in existing FPCs.

In evacuated tube collectors (ETCs), due to gap between tubes, whole aperture cannot be used as an absorber to trap solar radiation. Glass tube is prone to breakage during transportation, installation and periodic maintenance. During ¾ removal of hot fluid, mixing of supply ambient fluid with hot fluid, in hot fluid tank, reduces the temperature of hot fluid, is a major problem in most of the existing ETCs. In cylindrical hot fluid tanks, mixing problem is more acute.

In general, all above-mentioned types of solar fluid heaters have difficulty in installation as space with availability of solar radiation is major issue for people ¾ residing in small flats in urban area. Further, the cost is major issue in middle class families for purchasing solar fluid heating systems. Most of the present solar fluid heating system uses high grade material like more metallic parts, glass tubes, insulation, impose limitation in long run in the world of energy crises.

Accordingly, there is a need to develop a solar collector system which uses whole ttl aperture area as an absorber, reduces size of the collector, improves heat utilization factor, sustains fluid pressure and retains its shape, reduces insulation requirement, reduces heat loss from hot fluid tank and reduces mixing of hot and ambient fluid during removal of hot fluid. Further, there is need to develop a solar collector system which has low cost, breakage free transportation, installation and maintenance. Also, there is a need to develop a solar collector system that reduces problem of incorrect due south inclination of collector during system installation ¾ thereby faci I itati ng easy removal of sedi merits from the col I ector thereof.

Summary of the invention

The present invention provides a curved surface absorber type solar fluid heater which includes two radially spaced curved surfaces, preferably of hemispherical shape, closed at bottom periphery forming a closed chamber defining a collector

¾ of the present invention. The collector is equipped to receive a fluid to be heated therein. The curved surface absorber type solar fluid heater includes two radially spaced transparent curved surfaces that are closed at bottom periphery thereof and position over the collector as a glazing. The curved surface absorber type solar fluid heater includes an insulated hemispherical hot fluid tank preferably

¾ positi oned withi n the cavity of an i nner curved surface of the col I ector and bottom insulation. The curved surface absorber type solar fluid heater includes a plurality of first connecting members that facilitate connections between the collector and hot fluid tank. The hot fluid tank has a non-return valve and an air vent positioned thereon. The non-return valve prevents backflow of fluid from hot fluid tank ttl towards collector in absence of sunshine. The air vent is preferably located at the highest position of the collector and most preferably in proximity to the top end of the collector. The glazing, the collector and the hot fluid tank are placed on the bottom insulation. The collector and glazing are substantially concentric in accordance with preferred embodiment of the present invention. However, it is understood that the collector and glazing may be non- concentric in other alternative embodiments of the present invention. The curved surface absorber type solar fluid heater includes a plurality of second connecting members that ¾ faci I itate connecti ons between an ambi ent f I ui d supply tank and the col I ector. T he curved surface absorber type solar fluid heater includes a drain plug that is located at a lowest position on the collector in order to facilitate easy removal of sediment.

The collector gets heated by absorbing incoming solar radiation that in turn heats ¾ the fluid to develop a thermo siphon circulation of fluid in between the collector and hot fluid tank such that the temperature of the hot fluid increases until the thermal equilibrium between collector and the surrounding is reached. It is understood however that the fluid from hot fluid tank can be consumed as and when required thereby removing hot fluid from a highest position thereof. The ¾ hemispherical shape of the hot fluid tank and highest position of removal of hot fluid mutually reduce temperature loss which may occur due to mixing of supply ambient fluid with hot fluid. The unique combination of the shape of the collector and the position of the hot fluid outlet in the present invention enables heating of the fluid to a higher temperature in a given time and at given solar radiations. ttl In the context of the present invention, installation of hot fluid tank within the collector not only reduces insulation requirement but also reduces heat loss from outer surface thereof. Further, as the hot fluid tank is placed within the collector, convection loss is negligible. In addition, the collector has double walled construction that holds hot fluid inside and provides an additional hot fluid jacket to hot fluid contained with the hot fluid tank thereby preventing convection heat loss even in adverse situations like evening/ night hours during which climate is windy and solar radiation is poor.

¾ Brief description of the drawings:

FIG. 1 is a fragmentary sectional perspective view of a curved surface absorber type solar fluid heater constructed in accordance with the preferred embodiment of the present invention;

FIG. 1 A is an exploded view of the curved surface absorber type solar fluid heaterft of FIG. 1;

FIG. 2 is a wire frame view of the curved surface absorber type solar fluid heater of FIG. 1;

FIG. 3 is a partially expanded perspective view of the curved surface absorber type solar fluid heater of FIG. 1 showing details of supports and locking of¾ glazing defi ned thereon;

FIG. 4 is a fragmentary sectional perspective view of the curved surface absorber type solar fluid heater of FIG. 1;

FIG. 5 is a fragmentary sectional perspective view of the curved surface absorber type solar fluid heater of FIG. 1; and FIG. 6 is a perspective view of an alternative embodiment of the collector of the curved surface absorber type solar fluid heater of FIG. 1.

Detailed Description of the invention

Although specific terms are used in the following description for sake of clarity, ¾ these terms are intended to refer only to particular structure of the invention selected for illustration in the drawings, and are not intended to define or limit the scope of the invention.

Referring to FIGS. 1 and 1A, a fragmentary sectional perspective front view of a hemispherical absorber type solar fluid heater 50 in accordance with the preferred

¾ embodiment of the present invention is shown. The hemispherical absorber type solar fluid heater 50 has an approximately hollow hemispherical construction that mainly includes an outer transparent glazing 1, an inner transparent glazing 2, a black outer curved surface 3, an inner curved surface 4. A first chamber 26 is defined between the outer transparent glazing 1 and the inner transparent glazing

¾ 2. A second chamber 22 is defined between the black outer curved surface 3 and the inner curved surface 4. The second chamber 22 is configured to receive a fluid to be heated therein. The second chamber 22 formed by curved surfaces 3, 4 define a collector 28 of the hemispherical absorber type solar fluid heater 50 in accordance with the present invention. In an embodiment the collector 28 may ttl have a plurality of indentations on either inner surface or outer surface or on both i nner and outer surfaces i n order to i mpart strength to the col I ector 28. In additi on, the hemispherical absorber type solar fluid heater 50 includes a support grill 23 that facilitates support for hemispherical curved surfaces of the transparent glazing 1, 2.

The hemispherical absorber type solar fluid heater 50 includes a hot fluid tank 5, preferably of hemispherical shape. However, it is understood that the shape of hot

¾ fluid tank 5 may vary in other alternative embodiments of the present invention.

In this preferred embodiment, the hemispherical hot fluid tank 5 is enclosed concentrically within an enclosure formed by the collector 28 and the base insulation 12. However, it is understood that the hemispherical hot fluid tank 5 may be positioned in an off-centered positioned within the collector in alternative

¾ embodiments of the present invention. Further, it is understood that the hot fluid tank 5 may be positioned outside the collector 28 in another alternative embodiments of the present invention.

The hemispherical absorber type solar fluid heater 50 includes a plurality of connecting members including but not limited to a hot fluid tank inlet pipe 6, an

¾ ambient fluid pipe 8, an opposed pair of recirculation connectors 9 and a hot fluid tank outlet pipe 10. The hot fluid tank inlet pipe 6 connects the second chamber 22 to the hot fluid tank 5. The hot fluid tank inlet pipe 6 includes a non- return valve 7 positioned thereon. The ambient fluid pipe 8 connects to an overhead fluid supply tank (not shown). The recirculation connectors 9 facilitate connection ttl between the collector 28 and hot fluid tank 5. In particular, the connectors 9 facilitate flow of fluid from hot water tank 5 to collector 28 during sunshine hours. In addition, the connectors 9 facilitate flow of fluid from collector to hot water tank 5 duri ng usage of hot water stored i n the hot water tank. The ambient fluid pipe 8 is positioned along a plane that is normal to a plane of recirculation connectors 9. In this preferred embodiment, an angle between the ambient fluid pipe 8 and the recirculation connectors 9 is approximately 90°. However, it is understood that said angle between the ambient fluid pipe 8 and the ¾ recirculation connectors 9 may vary in other alternative embodiments of the present invention. The hot fluid tank outlet pipe 10 facilitates dispensing of hot fluid for usage. The collector 28 of the hemispherical absorber type solar fluid heater 50 i ncl udes an ai r vent 13.

Referring to FIG. 2, a drain plug 20 connects to the lowest position on the ¾ collector 28 to facilitate easy removal of sediment from the fluid heater 50. The hemispherical absorber type solar fluid heater 50 includes a peripheral insulation ring 21 configured along the base of the collector 28. The peripheral insulation ring 21 forms a part of base insulation 12 in accordance with the present invention.

¾ Referring to FIG. 3, a locking mechanism adapted for glazing 1, 2 along its support grill to base supports of a curved surface absorber type solar fluid heater 50 in accordance with the present invention are shown. The curved surface absorber type solar fluid heater 50 includes a plurality of supports 14. The supports 14 are held in position using respective locking arrangement/ mechanism ttl that includes a plurality of strips 15, a plurality of screws 16, a bottom locking plate 17, a top locking plate 18, and a locking clip 19. Referring to FIGS. 4 and 5, a fragmentary sectional front view of curved surface absorber type solar fluid heater 50 in accordance with the present invention includes a plurality of spacer strips 24 and a plurality of circular ring 25. A third chamber 27 is defined between inner curved surface of collector 28 and the ¾ bottom insulation 12. The hot fluid tank 5 has hot fluid tank insulation 11 that includes a vapour barrier 45 covered with a reflective foil 40. The bottom insulation 12 includes a vapour barrier 60 covered with a reflective foil 55. As shown in FIG. 5, the curved surface absorber type solar fluid heater 50 includes an ON/OFF cock 70 mounted on the connectors 9 as illustrated.

¾ Referring to FIG. 6, an alternative embodiment of the curved surface absorber type solar fluid heater 50 is shown wherein the second chamber 22 of the collector 28 is formed out of a plurality of tubular members 602 is positioned circumferential ly on a grid structure formed out of an outer hemispherical glazing 604 and an inner hemispherical support grid 606. Preferably, the tubular members

¾ 602 are positioned between the outer hemispherical glazing 604 and inner hemispherical support grid 606 such that the tubular member 602 is wound from a bottom end 610 to a top end 608 thereof. The hemispherical grid structure is designed such that each turn of the tubular member 602 remains snugly fitted with adjacent tubular member 602 to define the second chamber 22 having a tubular ttl hemispherical configuration in accordance with this alternative embodiment. In this alternative embodiment, the bottom end 610 of the tubular member 22 is connected to ambient fluid pipe 8. In this alternative embodiment, the top end 608 of the tubular member 22 is connected to hot fluid tank inlet pipe 6. Referring to FIGS. 1-6, in operation, an ambient fluid is supplied under predetermined pressure head from the ambient fluid pipe 8 to the second chamber 22 of the collector 28. The hot fluid tank 5 is connected to the collector 28 by the connectors 9.

¾ During sunshine hours, the solar radiation enters through the outer glazing 1 and inner glazing 2 such that the solar radiation is absorbed by black outer curved surface 3 that in turn heats fluid in the second chamber 22. Heating of fluid within the second chamber 22 develops thermo siphon effect that develops circulation of fluid from bottom portion of the collector 28 to top portion of the collector 28

¾ thereby enabl i ng the heated f I ui d to enter i nto the hot f I ui d tank 5 via the hot f I ui d tank inlet pipe 6 thereby enabling natural circulation to continue until the thermal equilibrium in between collector 28, hot fluid tank 5 and surrounding environment is achieved. The hot fluid flows from the top of the collector 28 through the hot fluid tank inlet pipe 6 via non-return valve 7. Thus, hot fluid from the hot fluid

¾ tank 5 is available for consumption as and when required through the hot fluid tank outlet pipe 10. It is understood here that the collector 28 facilitate whole hemispherical surface of the second chamber 22 to be utilized for heating of fluid. Further, it is understood that the natural circulation within the collector 28 may be replaced by forced circulation thereby connecting a pump to the ambient fluid ttl pipe 8 in other alternative embodiments of the present invention. Further, it is understood that a series of curved surface absorber type solar fluid heater 50 may be arranged in series thereby subjecting them under forced circulation by attaching pump(s) to their respective ambient fluid pipes 8 when requirement of heated fluid is at a higher flow rate in application areas, such as industrial use.

The collector 28 is supported on plurality of the supports 14. The collector 28 and the glazing 1, 2 are held together on the bottom insulation 12 thereby using the

¾ locking arrangement as shown in FIG .3. However, in an alternative embodiment, the glazing 1, 2 may have a zip lock arrangement to facilitate removal and replacement of the glazing 1, 2 from the curved surface absorber type solar fluid heater 50. The bottom locking plate 17 is attached to support strip 15 and top locking plate 18 is attached to the grill 23 which supports glazing 1, 2. The

¾ locking plates are in tension by the locking clip 19, which secures air tight connection between black outer curved surface 3 of collector 28 and glazing 2.

During sunset/ night hours, the pivot type dead weight non-return valve 7 performs the function of preventing back flow of fluid from hot fluid tank 5 to collector 28. The non-return valve 7 is preferably connected with predetermined

¾ inclination angle η. In this preferred embodiment, the inclination angle η is in a range from about 0° to about 90°. However, the inclination angle η may vary in other alternative embodiments of the present invention. The drain plug 20 is attached to lowest position of the collector chamber 22 as shown in FIG .2. Base of collector 28 is configured to have a predefined slope towards the drain plug 20 ttl for easy removal of sediments. For descaling, ON/OFF cocks 70 is installed on the connectors 9 with proper arrangement for isolating hot fluid tank 5. The ON/ OFF cock 70 is also required to be closed to isolate the hot fluid tank 5. It is understood however that the descaling agent is circulated through chamber 22 with proper inlet and outlet arrangement for few cycles until it is flushed out through drain plug 20.

In the context of the present invention, the curved surface absorber type solar fluid heater 50 is designed to maintain a predefined temperature difference ( VT) of 25 ¾ °C - 30 °C. It is understood here that VT in accordance with the present invention is a temperature difference between cold water inlet temperature and hot water outlet temperature.

In the context of the present invention, the insulation material used is Rock wool that has a density of approximately 96 Kg/m ³ and thermal conductivity of

¾ approximately 0.045 W/m K . However, it is understood that other types of insulation materials may be used in other alternative embodiments of the present invention. In the context of the present invention, the glazing 1, 2 are made of transparent material including but not limited to Polythene, Polycarbonate, glass and the like. In an alternative embodiment, the curved surface absorber type solar

¾ fluid heater 50 may be constructed without the use of glazing 1, 2.

In an embodiment of the present invention, the curved surface absorber type solar fluid heater 50 is a curved surface solar system which consists of a curved surface absorber, making the solar system independent of tracking requirements irrespective of geographic location of installation and/or irrespective of any ttl seasonal requirements and/or irrespective of any part of the year. This facilitates use of said curved surface solar system for heating of fluid and/or generation of electricity by solar cells. E xamples

Hereinafter, the present invention will be described in more detail based on examples. The examples are not intended to limit the scope of the present invention. It is believed the invention will be better understood from the following ¾ detailed examples:

E xample 1 :

C urved surface absorber type solar fluid heater 50 under natural circulation mode:

Experiment was conducted on the curved surface absorber type solar fluid heater ¾ 50 in a cloudy sky situation wherein average solar radiation was observed to be in a range from about 300 W/m ² to 450 W/m ² . Accordingly, in natural circulation mode, the temperature difference between an ambient temperature of the cold water entering from inlet to the collector and hot water coming out from collector was observed to be in a range of 20 °C to 25 °C. At 10 O ^" clock, an inlet ¾ temperature of water was 20°C. 10 liters of heated water was drawn at 45°C after 2 hours of solar heating in natural circulation mode.

E xample 2:

C urved surface absorber type solar fluid heater 50 under natural circulation mode: ttl Experiment was conducted on the curved surface absorber type solar fluid heater 50 in a clean sky situation wherein average solar radiation was observed to be in a range from about 400 W/m ² to 575 W/m ² . Accordingly, in natural circulation mode, the temperature difference between an ambient temperature of the cold water entering from inlet to the collector and hot water coming out from collector was observed to be in a range of 25 °C to 32 °C. At 10 0 ^" clock, an inlet ¾ temperature of water was 20°C. 10 liters of heated water was drawn at 52°C after 2 hours of solar heating in natural circulation mode.

E xample 3:

C urved surface absorber type solar fluid heater 50 under forced circulation in parallel mode:

¾ Experiment was conducted on the curved surface absorber type solar fluid heater 50 in forced circulation mode wherein an array of collectors 28 was arranged in a parallel arrangement such that simultaneous input of ambient temperature water inlet was given to each collector 28 and hot water was taken out from a common outlet to which outlet of each collector 28 was connected in parallel position.

¾ A ccordi ngly, i mprovement i n system response was observed i n term of eff i ci ency.

It was observed that there was gain of same temperature in force circulation mode for the same amount of water in less time in comparison to natural mode.

E xample 4:

C urved surface absorber type solar fluid heater 50 under forced circulation ttl in series mode: Experiment was conducted on the curved surface absorber type solar fluid heater 50 in forced circulation mode wherein array of collectors 28 was arranged in a series arrangement such that the ambient temperature water input was given to the inlet of the first collector 28 and hot water outlet of the first collector 28 was ¾ connected to the inlet of the next col I ector 28. In seri es mode, the temperature ri se was observed to be higher than that of temperature rise under the forced circulation in parallel mode. In series mode, the flow rate of water was observed to be lower than the flow rate of the water under forced circulation in parallel mode.

¾ The embodiments of the invention shown and discussed herein are merely illustrative of modes of application of the present invention. Reference to details in this discussion is not intended to limit the scope of the claims to these details, or to the figures used to i 11 ustrate the i nventi on.

It is understood that various omission and substitutions of equivalents are ¾ contemplated as circumstance may suggest or render expedient but such are intended to cover the application or implementation without departing from the scope of the present invention.