GB2044915A

GB2044915A - Solar powered cooling system

Info

Publication number: GB2044915A
Application number: GB7923638A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1979-02-26
Filing date: 1979-07-06
Publication date: 1980-10-22

Abstract

The application describes a device for a solar energised night cooler for improving sleeping conditions for those who live in areas of the world where high night temperatures prevent relaxation. No electricity is required. A solar concentrator provides heat to the boiler of an absorption refrigeration circuit so that during the day a refrigerant is collected in a reservoir. At night by reversing shutters and/or valves the refrigerant is released so cooling a cold convector over which air falls by natural convection. Alternatively, in operation during the day, the refrigeration circuit cools a cold store over which air to be cooled passes during the night. <IMAGE>

Description

SPECIFICATION A device for solar night cooling Purpose This invention is concerned with providing night cooling in the Tropics without the use of electricity or other fuels. In areas where night temperatures are high there is a considerable loss of daytime working efficiency especially for those whose origins are in more temporate climates. This is normally overcome by the use or airconditioning in the sleeping quarters. In areas where electricity is not readily available airconditioning is not possible. This is the situation at many research and construction projects and in small rural communities.

Form - Type 1.

The invention (see first drawing) consists of a solar heat concentrator of the circular parabolic type which has a hand set angular elevation and a clockwork motor drive to follow the sun. The concentrator is focused by a secondary reflector to a point behind a hole at its centre to a receiver which is the bottom end of a heat pipe. The heat pipe is well insulated and supports the concentrator. The heat pipe is a high pressure sealed pipe designed to work at about 200-C. The top end of the heat pipe forms the the heat exchanger of an absorption refrigeration circuit. The absorption refrigeration circuit is part of the cooling unit which consists of an insulated box containinga. a cold store containing either water with an ice crystal forming additive of a suitable chemical storage material.

b. a cold convector. Similar two a modern finned central heating radiator but with a shutter at the bottom which when closed will prevent the convector surfaces from working.

The unit is mounted in the wall of the sleeping quarters with the refrigerator condensor on the outside, the cold store in the centre and the convector on the inside over the bed. The unit must be so positioned that the solar concentrator on the end of the heat pipe is exposed to the maximum number of hours of sunlight at all times of the year.

Action - Type 1.

The working cycle is as follows. In the morning the operator closes the shutter on the convector, windsup the concentrator clockwork motor and aims the concentrator at the sun. If the elevation is correctly set (a once a month operation the concentrator will then follow the sun, being driven by the clockwork motor. With the sun focused on the bottom of the heat pipe the temperature inside the pipe will rise until at about 200-C the water will boil inspite of the high pressure in the tube. The water will condense at the top of the pipe transfering the solar energy to the heat exchanger of the refrigeration circuit. Thus the refrigeration cycle is activated and cools the cold store so that during the day the fluid in the store and the convector is cooled with ultimately the formation of ice crystals to provide latent heat storage.At night the operator opens the shutter and allows cool air to fall through the cold convector surfaces and spread over the bed and its occupant below. The cooling unit must be mounted over the bed and space must be left between the ceiling and the top of the unit to allow a flow of air to enter the top. The system would work best with bed in a corner and a low screen around the bed may be used to contain the cooled air. The cold convector surfaces will need to be drained at the bottom of condensation. The resulting low humidity of the air about the bed will help in cooling the occupant. The drawing shows an alternative position for the concentrator at which it is focused directly on the underside of the heat pipe.

Form- Type 2.

The second drawing shows a similar devise with two main modifications. The first is that the solar concentrator is of the cylindrical parabolic type. This type is most suited to the Tropics (ie between about +12 latitude).

The long axis of the concentrator must be positioned approximately east-west and the angular setting adjusted monthly to aline with the path of the sun. This type of concentrator does not require a clockwork drive.

The second modification is in the use of an intermittent refrigeration cycle in which the refrigerant is stored during the day and released in to the cold convector at night by opening a valve. Close control of the rate of cooling of the air is not possible by the valve so a slidding shutter on the airflow is still necessary.

Action - Type 2.

The working cycle is as follows. In the morning the operator closes the on-off valve and once a month adjusts the concentrator elevation angle setting.

During the day the refrigerant is boiled off from the high pressure water boiler which runs the length of the focus of the concentrator. The refrigerant is condensed in the external section of the refrigeration circuit and drains into the refrigerant store.

At night the operator opens the on-off valve releasing the refrigerant into the cold convector where it evaporates so providing the cooling and returns to be reabsorbed into the water in the now cooled boiler. The action is then as for the Type 1.

On sunless days neither system will work but when the sleeping quarters have not been exposed to sunlight directly, sleeping conditions will be better.

This system could be used for water cooling as an alternative application.

Contents of drawing 1.

1. Cylindrical Parabolic Solar Concentrator 2. Heat Pipe 3. Focal Axis Heat Collector 4. External Container of Refrigeration Circuit 5. Internal Container of Refrigeration Circuit 6. Casing 7. Mechanical Control System 8. Bed 9. Wall of Room 10. East-West Additional contents of drawing 2.

11. Heat Insulating Lining of Casing 12. External Container with Silica-gel 13. Internal Container with Condensed Water 14. Shutter control lever with Day & Night positions (shown dotted as lever is on outside of casing, shown only on section B.) W, X, Y, & Z are the shutters

Claims

CLAIMS 1. I claim the system described underthe heading GENERAL DESCRIPTION (Page 3) and illustrated in Drawing 1. The concept of cooling a limited area of a room at night by use of an absorption refrigeration circuit energised during the day by solar energy is described with sufficient detail as to constitute a viable product. 2. 1 claim the following details from the system described under the heading PARTICULAR DESCRIP TION (Pages 4 to 7) and and illustrated in Drawing 2. a). The use in this devise of a low pressure waterisilica-gel intermittant refrigeration circuit, b). The system of shutters and casing which provides the correct conditions for the operation of the devise. New claims or amendments to claims filed on 5th June 1980. Superseded claims 1 and 2 New or amended claims: WHAT I CLAIM IS

1. A solar energised refrigeration circuit. which stores a coolant during the day, in sufficient quantity to provide improved sleeping conditions on a bed, by downward convection of air from the surfaces of the coolant container which is suspended over the bed. This devise requires no power soarce other than the solar energy collector.

2. The solar energy can be collected by any means compatable with the refrigeration circuit to be used.

3. The refrigeration circuit can be of any type to produce the coolant either by cooling a suitable storage medium or by collecting the refrigerant in the circuit during the day to be evaporated at night.

In the first case the refrigeration circuit could be an absorption system (Platen & Munters type) which would cool water to produce ice during the day. Or, in the future, when solar cells are much cheaper, the circuit could contain a battery driven compressor, the battery to be charged by the solar cells. In the second case an intermittant refrigeration circuit is required with a suitable refrigerant which may be stored in a domestic situation in the quantity re quired.

4. In particular the use of a low pressure water and silica-gel circuit is proposed. The silica-gel is heated by solar energy transmitted from the solar collector. This drives-off the water in the silica-gel which is collected in in a condenser. At night when the silica-gel cools the water evaporates to cool the condenser and is reabsorbed in the silica-gel. A set offlaps or shutters is required with this system to direct the air flow over the silica-gel container and the condenser via different routes for night and day.