WO2008062409A2

WO2008062409A2 - Improved solar water heating systems

Info

Publication number: WO2008062409A2
Application number: PCT/IL2007/001436
Authority: WO
Inventors: Gregori Kofler; Micki Carmel; Tsach Aylon
Original assignee: 'chromagen' Agricultural Cooperation Society Ltd
Current assignee: 'chromagen' Agricultural Cooperation Society Ltd
Priority date: 2006-11-21
Filing date: 2007-11-21
Publication date: 2008-05-29
Anticipated expiration: 2009-05-21
Also published as: WO2008062409A3

Abstract

It is provided an improved closed-loop solar thermi-siphon heating system that comprises a storage tank for heated water provided with inlet and outlet pipes and a heat exchanger provided within a storage tank. The heat exchanger is fluidically connected to solar collectors and is connected to an expansion vessel that is capable of receiving excess water from the heat exchanger and to discharge it back into the heat exchanger.

Description

IMPROVED SOLARWATER HEATING SYSTEMS

FIELD OF THE INVENTION

The present invention relates to improvements in solar water heating systems, and more particularly to heating systems in which the water storage tank is in a horizontal position, and the heating fluid circulates in a closed loop between the heat exchanger and the collectors.

INVENTION BACKGROUND

Solar water heaters are used mainly in adequate climates as a cost effective way for producing hot water. A basic solar heating system generally includes solar thermal collectors, a storage or reservoir tank in which the hot water are stored, and a fluid system to move the water between the heat collectors and the storage tank. The solar collectors transform solar energy to hot fluid; the hot fluid is flowing into a water storage tank & heating the water inside the storage tank. The energy of the heated fluid is transferred to water inside the storage tank via a heat exchanger. The heat transfer fluid circuit is referenced as closed loop. Solar heating systems are adapted to be used for domestic needs as well as industrial and other needs.

Solar systems were popular in sunny countries in the US such as Florida of regions of California in the 20^th century. Doe to the abundance of sunlight in Israel, solar water heaters were used by about 20% of the population by 1967. Following the energy crisis, a law was passed requiring the installation of solar water heaters in all new homes (except high towers with insufficient roof area). Israel is considered as one of the world leading countries in the use of solar energy per capital. During this time, other countries started to be interested in the use of solar systems installation of solar heating systems became custom in countries with abundance of solar radiation. The increase in use of solar systems brought about technical innovations that have improved the performance, the life expectancy, and the ease of use of the solar heating systems. However, there is still a long felt need to improve the performance and other features of closed loop systems.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an improved closed-loop solar thermo-siphon heating system.

It is another object of the present invention to provide an expansion vessel for an improved closed loop thermo-siphon heating system.

It is yet another object of the present invention to provide connectors for improved closed loop solar heating system. It is therefore provided in accordance with a preferred embodiment of the present invention, An improvement in solar water heaters comprising a horizontal water tank and an inner heat exchanger receiving hot liquid from solar collectors, the improvement comprising an expansion vessel made of a flexible metallic material, capable of receiving excess liquid when the pressure in the heat exchange increases.

Furthermore, in accordance with another preferred embodiment of the present invention, said material is selected from a group of materials such as aluminum.

Furthermore, in accordance with another preferred embodiment of the present invention, said heat exchanger is serpentine.

Furthermore, in accordance with another preferred embodiment of the present invention, said expansion vessel is positioned above the higher inlet to the heat exchanger.

Furthermore, in accordance with another preferred embodiment of the present invention, the expansion of said expansion vessel is reversible. Furthermore, in accordance with another preferred embodiment of the present invention, the expansion vessel is provided with at least one holder capable of limiting deformation of said expansion vessel.

In addition and in accordance with yet another preferred embodiment of the present invention, a solar water heating system is provided that comprises: a storage tank for heated water provided with inlet and outlet pipes; a heat exchanger provided within said storage tank; solar collectors fluidically connected to said heat exchanger wherein fluid is adapted to circulate between the solar collectors and the heat exchanger; expansion vessel fluidically connected to said heat exchanger, wherein said expansion vessel is capable of receiving excess water from said heat exchanger and to discharge the excess water back into said heat exchanger.

Furthermore, in accordance with another preferred embodiment of the present invention, said expansion vessel is made of a flexible metallic material. Furthermore, in accordance with another preferred embodiment of the present invention, said material is selected from a group of materials such as aluminum.

Furthermore, in accordance with another preferred embodiment of the present invention, the expansion of said expansion vessel is reversible.

Furthermore, in accordance with another preferred embodiment of the present invention, the expansion vessel is provided with at least one holder capable of limiting deformation of said expansion vessel.

Additionally and in accordance with yet another preferred embodiment of the present invention, it is provided fitting for solar collectors of solar water heaters comprises a spherical flare at one end of at least one pipe adapted to seal with an O-ring a connection between said pipe and pipes of manifolds in any angle between them while aligning the pipes in a desired angle using a bracket. Furthermore, in accordance with another preferred embodiment of the present invention, the fittings are made of plastic material.

Furthermore, in accordance with another preferred embodiment of the present invention, said bracket is enclosed on said pipes.

Furthermore, in accordance with another preferred embodiment of the present invention, at least one spring firmly holds said bracket.

Additionally, in accordance with another preferred embodiment of the present invention, said pipes of manifolds are in the different shapes selected from a group of "T", "L", or straight pipes.

BRIEF FIGURE DESCRIPTION

In order to better understand the present invention and appreciate its practical applications, the following figures are attached and referenced herein. Similar components are denoted by similar reference number.

Please note the figures are given as an example and a preferred configuration only, and do not limit the scope of the present invention in any way, as defined in the appending Description and Claims.

Figure 1 illustrates a scheme of a thermo-siphon closed loop system with serpentine heat exchanger in accordance with a preferred embodiment of the present invention.

Figures 2a &b illustrates an isometric view and a cross sectional isometric view of the closed loop system, respectively, in accordance with a preferred embodiment of the present invention, with a heat exchanger and expansion vessel assembled in a preferred configuration.

Figure 3 illustrates a side view of the present invention, showing the water tank, the expansion vessel and the socket connecting the two, assembled in a preferred configuration in accordance with a preferred embodiment of the present invention.

Figure 4 illustrates a left cross section view of the expansion vessel assembled in a preferred configuration in accordance with a preferred embodiment of the present invention.

Figure 5 illustrates a front view of the expansion vessel shown in Figure 3.

Figures 6a-d illustrates "exploded" views of quick fittings for closed loop systems in accordance with preferred embodiments of the present invention.

DETAILED DESCRIPTION OF THE INVENTION AND FIGURES

The present invention provides a novel and improved solar heating system and preferably a closed loop system. in one aspect of the present invention, the invention provides a new solar heating system enabled with quick and tool-less installation with "plug & flow" fittings. The tool-less concept aids safety of workers in high roofs that no longer need to carry and use cumbersome wrenches,

In another aspect of the present invention, it provides an expansion tank that is provided to the heating system designs that eliminates the need for heat sensitive rubber diaphragms to ensure high durability during the systems' life span. Reference is made to Figure 1 illustrating a scheme of a thermo-siphon closed loop system with serpentine heat exchanger in accordance with a preferred embodiment of the present invention. A water storage tank 100, which is placed in a horizontal position, is provided with a heat exchange 102 that is preferably serpentine and is provided within tank 100. Water tank 100 is enclosed with an outer expansion vessel 104 in an external thermally insulated shell covered with an external cover as indicated with dotted lines 106 in the Figure. Water tank 100 is provided with a safety valve 108 on the inlet water supply pipe 109 and a pipe 110 from which water can be delivered to the user. Solar collectors 112 are fluidically connected by pipes 120 and 122 to heat exchanger 102. The direction of fluid flowing in the system is indicated by arrows within the pipes. Water is circulated between the collectors and heat exchanger 102 through the pipes in a manner that is customary in the industry. An air relief valve 124 is provided on pipe 122 so as to relieve any air bubbles, detrimental to heat exchange processes that enters the system.

Solar collectors 112 are connected to each other by dedicated and specially designed fittings 114, 116, and 118 as will be explained herein after (the connectors are enlarged in the figure and the type of connector is indicated as will be shown herein in the relevant figures). The fittings are capable of providing some degree of freedom to the connection between the collectors so that the system will be more flexible. It should be noted that any type of heat collectors can be used in the solar heat system of the present invention without limiting the scope of the present invention.

Reference is now made to Figures 2a and b illustrating an isometric view and a cross sectional isometric view, respectively, of the closed loop system in accordance with a preferred embodiment of the present invention, with a heat exchanger and expansion vessel assembled in a preferred configuration. As previously indicated and illustrated, water tank 10 is designed to be positioned horizontally. Water tank 10 is provided with heat exchanger 12 that receives the hot liquid from the solar collectors (solar collectors not shown in Figure 2). Heat exchanger 12 as shown in Figure 2b is a serpentine pipe positioned within tank 10. Water that enters tank 10 is heated by heat exchanger 12. Expansion vessel 16 is connected to the upper side of heat exchanger 12 by joint pipe 14. Expansion vessel 16 is preferably made of a flexible aluminum profile and is positioned above the higher inlet of heat exchanger 12 in order to allow release of air from the closed loop. Under solar irradiation, the liquid temperature in the closed loop rises and its volume and pressure increases. Flexible expansion tank 16 expands and moderates pressure increase by absorbing excess liquid. This process is reversible; when the temperature in the system decreases, the walls of expansion vessel 16 return to their original state and the excess liquid returns to heat exchanger 12. This solution facilitates the design of an effective closed solar water heating system.

The system is designed to allow normal action when the temperature of the liquid does not exceed 150 ⁰C and 4.5 bar. In case of a failure that causes the temperature to rise above 150 ⁰C, safety valve 18 opens up in order to release the excess pressure that was formed within the closed system. It should be emphasized that the current design of the expansion vessel is advantageous in respect with other since it is all made of aluminum a fact that eliminates a major portion of corrosion effect. The aluminum body is flexible and resistant to high temperature in oppose to rubber diaphragm which is the design that is used nowadays in expansion vessels. Figures 3 and 4 illustrates side view and a cross sectional view of an expansion vessel and a boiler joint in accordance with a preferred configuration of the present invention. Cover 20 is part of expansion vessel 16 and is maintained attached and secured by an O-ring 22, preferably having a cross sectional diameter of 4 mm. Rear cover 24 is a part of the expansion vessel cover as well. Parts "20" and "24" are secured to each other by socket 25. Socket 25 is welded to the water tank and holds the expansion vessel in desirable position.

Figure 5 illustrates a frontal view of the expansion vessel. Aluminum I holders 26 and 28 are aimed at limiting the deformation of the expansion vessel. The expansion vessel is preferably made by extrusion process and is designed to work for about 10 years or 3000 cycles. The volume change of expansion vessel 16 is designed to be between 400 ml to 1400 ml. No maintenance actions are required for the expansion vessel.

Horizontal solar water tanks are relatively narrower than vertical water tanks, therefore heat exchanger 12 (shown in Figure 2), is specially designed to fit into water tank 10 and to minimize heat losses. The heat exchanger is designed of 1 inch diameter steel pipe and is meandering within the tank.

Connectors or quick fittings that may connect between the solar collectors, between the collectors and the water tank and between other elements of the system were developed in order to provide some degree of freedom to the connections.

Figures 6a-d illustrate exploded views of the connectors. The connectors are easy and quick to use. The end forming of pipe 5 shown in Figures 6a and 6b and pipe 7 in Figures 6c and 6d is a spherical flare. The "L" or "T" connectors (all referred in the figures in the numeral 3) are preferably made of brass and are inserted into the flare end of pipe 5 or 7 while O-ring 4 hydraulically seals the connection. Bracket 1 , preferably made of aluminum, holds the pipes together using springs 2. The pipes are simply aligned. It should be mentioned that the fittings can be made of different types of material such as aluminum or brass or plastic but are not limited to those materials and fittings made of other materials are possible.

Reference is made again to Figure 1 illustrating the positioning of the fittings shown in Figure 6 into the system. The solar collectors are provided with the fitting that is adjusted to the positioning within the system. Different type of fitting is fitted between both collectors so as to allow some freedom of movement using the flare structure or in the angle of one collector where the structure is more fixed. As mentioned herein before, the fittings are shown in enlarged configurations.

It should be emphasized that the fittings of the present invention are of the type of fast installation w/o any seal material. The only seal is the O-rings. The fittings allow connecting manifolds of solar collectors that are not necessarily aligned and are suitable for all kinds of solar systems: open loop, closed loop, thermo siphon and forced circulation systems. It should be clear that the description of the configurations and attached Figures set forth in this specification serves only for a better understanding of the invention, without limiting its scope as covered by the following Claims.

It should also be clear that after reading the present specification a skilled person, can make adjustments or amendments to the attached Figures and above described configurations that would still be covered by the following Claims.

Claims

C L A I M S

1. An improvement in solar water heaters comprising a horizontal water tank and an inner heat exchanger receiving hot liquid from solar collectors, the improvement comprising an expansion vessel made of a flexible metallic material, capable of receiving excess liquid when the pressure in the heat exchange increases.

2. The improvement as claimed in Claim 1 , wherein said material is selected from a group of materials such as aluminum.

3. The improvement as claimed in Claim 1 , wherein said heat exchanger is serpentine.

4. The improvement as claimed in Claim 1 , wherein said expansion vessel is positioned above the higher inlet to the heat exchanger.

5. The improvement as claimed in Claim 1 , wherein the expansion of said expansion vessel is reversible.

6. The improvement as claimed in Claim 1 , wherein the expansion vessel is provided with at least one holder capable of limiting deformation of said expansion vessel.

7. A solar water heating system comprising: a storage tank for heated water provided with inlet and outlet pipes; a heat exchanger provided within said storage tank; solar collectors fluidically connected to said heat exchanger wherein fluid is adapted to circulate between the solar collectors and the heat exchanger; expansion vessel fluidically connected to said heat exchanger, wherein said expansion vessel is capable of receiving excess water from said heat exchanger and to discharge the excess water back into said heat exchanger.

8. The heating system as claimed in Claim 7, wherein said expansion vessel is made of a flexible metallic material.

9. The heating system as claimed in Claim 8, wherein said material is selected from a group of materials such as aluminum.

10. The heating system as claimed in Claim 7, wherein said heat exchanger is serpentine.

11. The heating system as claimed in Claim 7, wherein said expansion vessel is positioned above the higher inlet to the heat exchanger.

12. The heating system as claimed in Claim 7, wherein the expansion of said expansion vessel is reversible.

13. The heating system as claimed in Claim 7, wherein the expansion vessel is provided with at least one holder capable of limiting deformation of said expansion vessel.

14. Fitting for solar collectors of solar water heaters comprises a spherical flare at one end of at least one pipe adapted to seal with an O-ring a connection between said pipe and pipes of manifolds in any angle between them while aligning the pipes in a desired angle using a bracket.

15. The fitting as claimed in Claim 14, wherein the fittings are made of plastic material.

16. The fitting as claimed in Claim 14, wherein said bracket is enclosed on said pipes.

17. The fitting as claimed in Claim 14, wherein at least one spring firmly holds said bracket.

18. the fitting as claimed in Claim 14, wherein said pipes of manifolds are in the different shapes selected from a group of "T", "L", or straight pipes.

19. An improvement in solar water heaters substantially as described in the above specification, attached Figures and appending Claims.

20. Fitting for solar collectors of solar water heaters substantially as described in the above specification, attached Figures and appending Claims.