GB2383384A

GB2383384A - Solar powered thermal pump

Info

Publication number: GB2383384A
Application number: GB0224162A
Authority: GB
Inventors: Peter Mckay
Original assignee: Individual
Current assignee: Individual
Priority date: 2001-10-18
Filing date: 2002-10-17
Publication date: 2003-06-25
Also published as: GB0124996D0; GB0224162D0

Abstract

A solar powered pump comprises a solar collector 10 that absorbs heat from solar radiation and transfers the heat to an evaporation screen 11 which holds a small amount of liquid converting part of the liquid to vapour creating vapour pressure in an expansion chamber 31, the pressure puts force on the liquid in a reservoir 35 connected to the expansion chamber 31, pumping the liquid past a non-return valve and up the outlet pipe 32 to a higher level, as the liquid in the reservoir falls it actuates float valves that releases pressure allowing liquid to flow onto the evaporation screen 11 actuating a condensing phase that makes the process cyclical, the expansion chamber is enclosed in an outer container which reflects solar radiation onto the solar collector 10.

Description

The invention relates to a solar powered thermal pump. The embodiment of the invention in the description is a solar powered water pump, although the said pump could be used to pump other liquids or mixture of liquids that will evaporate and condense with in the working parameters of said pump. Wind driven water pumps have long been used to raise and move water e.g. for irrigation in agriculture, for economic and environmental reasons renewable resources are desirable for this work. An object of the present invention is to provide a method of moving water from a source to a higher level e.g. from an irrigation channel to a crop in a field.

The present invention obtains its energy from the same part of the solar spectrum as a water heater solar panel and would be a compatible pump for said heater panels, automatically starting, stopping and sensing the strength of the radiation without the need for electrically powered pumps or sensors. A combination of the invention and aforementioned heater panel could be used to construct a solar disinfecting unit for improving poor quality drinking water.

With a very large array of the invention in the form of water pumps it maybe possible to construct a pumped storage hydroelectric generator for isolated dwellings in areas with predominantly clear skies.

The devices disclosed in the G. B. Pat. 2,342,958 is provided with an expansion chamber with a flat solar collector wall, the other walls of the expansion chamber have to be substantially lined with thermal insulation. According to the present invention, there is provided a solar powered pump comprising a rigid cylindrical container with a tubular wall functioning as a solar collector, said wall is made of or coated on outer surface with material known to absorb solar radiation and converting said radiation into heat, the heat is conducted to the inner surface of the solar collector wall, said inner surface which is absorbent holds a film of liquid, the heating of said liquid creates vapour pressure in the container said pressure puts force on liquid in a reservoir connected to

said container, pumping the liquid to a higher level than a feed level, when the level of liquid in said reservoir falls a valve mechanism releases the pressure, or the pressure escapes to atmosphere via a reservoir outlet pipe allowing liquid to flow under the influence of gravity and surface tension, onto the inner surface of the solar collector wall cooling the solar collector wall, refilling the reservoir, and actuating a drop in temperature thereby causing the vapour to condense, completing a cycle, the expansion chamber, is enclosed in an outer container, the back and base walls of said outer container are flat and lined with a reflective material, said expansion chamber is fixed relative to said walls at a point where solar radiation is reflected onto the solar collecting wall not receiving direct solar radiation, front wall of said outer container is made of transparent plastic or glass.

The invention will now be described by way of example and with reference to the accompanying drawings in which:- Figure 1 is a side cross-sectional view illustrating the flow of water and air through the atmospherically sealed embodiment of the invention, Figure 2 is a detail sectional view, to a larger scale of the float chamber as shown in Fig.l,

Figure 3 shows the front view of the pump with a partially sectioned view showing the evaporation screen, Figure 4 illustrates a detail sectional view, to a larger scale of the wall of the expansion chamber that also functions as the solar collector, and shows the distribution of water on the evaporation screen. Figure 5 is a side cross-sectional view illustrating the flow of water and air through a gravity fed, atmospherically open embodiment of the invention.

Figure 6 shows the invention in a simple positive pressure pumping system. The solar pump illustrated in Figure 1 comprises an expansion chamber 31 the said chamber consist of an evaporation screen 11 which is bonded to the wall 10 of the expansion chamber 31, the wall 10 functions as the solar collector and would typically have a pigmentation known to absorb solar radiation if made from synthetic plastics material, or made of narrow gauge steel or aluminium,(a typical gauge would be 0.25mm up to 1.50mm) coated on outer surface with material known to absorb solar radiation and convert it to heat.

As shown in Figure 4 the evaporation screen 11 would typically be a narrow gauge woven or fibrous material e.g.fibreglass, preferably the weave should allow the incoming water to run through the material at the refill phase, and then hold part of the water in the weave to create a large surface area at the interface between the water and the air in the expansion chamber 31.

Shown in Figure 1 the atmospherically sealed embodiment of the invention, at the refill phase the water flows down tube 19 through the open float valve 25 and then back up to the ducts 17 and then cascades down the evaporation screen 11 this effectively isolates the interior of the expansion chamber 31 from the heat source, the wall 10 actuating a rapid drop in temperature and pressure inside the expansion chamber 31 causing most of the water vapour to condense out. The incoming water flows on down the outlet duct 18 into the float chamber 35 until the

inlet control float 23 closes the inlet valve 25, at the same time the pressure release valve 26 also closes, the small amount of water held in the evaporation screen 11 starts to heat up giving off water vapour this causes an increase in pressure in the expansion chamber 31, when the pressure is sufficient water in the float chamber 35 is forced past the non-return valve 21 and up the outlet tube 32 to a higher level than the feed level gaining potential energy. As the air in the expansion chamber 31 becomes saturated with water vapour the pumping action slows down at this point in the cycle, the water level in the float chamber 35 as dropped causing the inlet control float 23 to drop leaving the ball valve 25 held in place by pressure, the pressure release valve 26 is integrally

connected to the float 24 as the water level drops more, the mass of the float 24 overcomes the pressure and the pressure release valve 26 snaps open, releasing the saturated air to top sealed container 29 via tube 20. The equalisation in pressure causes the inlet ball-valve 25 to open bring the cycle back to the refill phase, as the water runs through the evaporation screen 11 during the refill condensing phase, the pressure in the expansion chamber 31 drops below the atmospheric pressure causing water to be drawn up feed tube 32 into the

expansion chamber 31 this continues till the water level in the float chamber 35 closes the inlet valve 25 and the pressure release valve 26. If the pressure in the expansion chamber 31 falls below the atmospheric pressure whilst the two float valves are closed e.g. if cloud obscures the sun part way through a cycle, air will be drawn in through breather valve 22.

The embodiment of the invention shown in Fig 5 is a simpler alternative form of the invention, in a gravity fed atmospherically open embodiment of the invention the vapour is vented to the atmosphere at the end of each cycle. This embodiment of the invention has good reliability and is economical to manufacture.

The positive pressure pumping system shown in Fig 6 is an alternative way of lifting water from a level lower than the solar collector. Fig 6 shows the system at the point of the cycle where pressure from the solar collector 10 starts forcing water out of the sump reservoir 44 up to top reservoir 43 and through the outlet pipe, when all the water is forced out the sump reservoir 44 the pressure escapes to atmosphere through the outlet pipe, the drop in pressure allows water from the top reservoir 44

to flow past non-return valve 41 into solar collector 10 actuating a further drop in pressure, the sump reservoir 44 refills through non-return valve 45, the water from the top reservoir 43 runs through the solar collector 10 into the intermediate reservoir 42 the amount water in this part of the system should be limited to the amount needed to actuate a substantial drop in temperature in the solar collector 10. As the solar collector begins to heat up again the pressure forces the water from the intermediate reservoir 42 to the top reservoir 43 via the sump reservoir 44 completing a cycle. Non-return valve 46 is optional.

Claims

1. A solar powered pump comprising a rigid cylindrical container with a tubular wall functioning as a solar collector, said wall is made of or coated on outer surface with material known to absorb solar radiation and converting said radiation into heat, the heat is conducted to the inner surface of the solar collector wall, said inner surface which is absorbent holds a film of liquid, the heating of said liquid creates vapour pressure in the container said pressure puts force on liquid in a reservoir connected to said container, pumping the liquid to a higher level than a feed level, when the level of liquid in said reservoir falls a valve mechanism releases the pressure, or the pressure escapes to atmosphere via a reservoir outlet pipe allowing liquid to flow under the influence of gravity and surface tension, onto the inner surface of the solar collector wall cooling the solar collector wall, refilling the reservoir, and actuating a drop in temperature thereby causing the vapour to condense, completing a cycle, the expansion chamber, is enclosed in an outer container, the back and base walls of said outer container are flat and lined with a reflective material, said expansion chamber is fixed relative to said walls at a point where solar radiation is reflected onto the solar collecting wall not receiving direct solar radiation, front wall of said outer container is made of transparent plastic or glass.

2. A solar powered pump according to claim 1, wherein said valve mechanism releases the pressure into a sealed top reservoir the said sealed top reservoir is positioned above the level of the top of solar collector wall, the sealed top reservoir is refilled with liquid by the force of atmospheric pressure.

3. A solar powered pump according to claim 1 or 2, wherein said outer container, back and base walls are replaced with a parabolic reflective wall.

4. A solar powered pump according to claim 1 or 2, wherein said front wall of outer container is a fresnel lens.

5. A solar powered positive pressure pumping system according to claim 1, wherein said pump puts pressure on liquid in a sump container fixed in a body of liquid at a lower level than a solar collector, raising liquid above solar collector.

6. A solar powered pump substantially as herein described and illustrated in the accompanying drawings.