GB2034457A

GB2034457A - Solar heating

Info

Publication number: GB2034457A
Application number: GB7844408A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1978-11-14
Filing date: 1978-11-14
Publication date: 1980-06-04
Also published as: GB2034457B

Abstract

A fluid heating system comprises a cylinder (10) having a cold water inlet (11) and a hot water outlet (12) supplied with heated fluid from a solar heated panel through a pipe (14) to a heat exchanger (15) in the cylinder. Fluid from the heat exchanger flows to an insulated tank (16) shaped so that fluid from the solar heating system surrounds the base of the cylinder. From the tank (16) fluid flows through an outlet (23) to a pump which urges the fluid through a return pipe (18) to the solar panel. A branch supply of water from the cold inlet pipe (11) is controlled by a ball valve (17) to maintain the fluid level in the tank (16) constant in use. <IMAGE>

Description

SPECIFICATION Improvements in or relating to solar heating installations The invention relates to solar heating installations.

According to the invention there is provided solar heating apparatus for heating fluid in a cylinder, which apparatus comprises a solar panel, ht!at exchanger means positioned in use in the cylinder through which heat exchanger means fluid from the solar panel passes, fluid container means for surrounding a portion of the cylinder into which fluid container means fluid from the heat exchanger means flows, outlet means from the fluid container means connected to the solar panel to allow return of fluid to the solar panel and means for circulating fluid through the solar heating apparatus.

The circulating means is preferably a pump, and the fluid container means is preferably a tank surrounding, in use, a base portion of the cylinder.

The tank, in use, may surround the cylinder up to a depth not greater than one third of the height of the cylinder.

According to a further aspect of the invention there is provided a fluid heating system comprising a cylinder having a cold fluid, for example cold water, inlet at or adjacent the base of the cylinder and a hot fluid, for example hot water, outlet at or adjacent the top of the cylinder and solar heating apparatus according to the invention.

The cylinder may be provided with an immersion heater for heating fluid in the cylinder.

The cold fluid inlet is preferably supplied through a pipe and there is preferably a branch supply from the cold fluid supply to the fluid container means, there being valve means to control supply of fluid through said branch supply to maintain fluid level in the fluid container means at a substantially constant level. The valve means may comprise a floating ball valve.

The dimensions of the fluid container means and the fluid level in the fluid container means in use are preferably such that, when fluid is no longer circulated through the solar heating apparatus, said solar heating apparatus fluid is able to drain into and to be contained in the fluid container means.

Conventional cylinders are usually formed with a concave base. Accordingly, a fluid heating system according to the invention may further comprise a siphon pipe arranged with one end lying adjacent the centre of the base of the cylinder and the other end lying at a level above the level of said one end of the siphon pipe.

By way of example, one embodiment of a solar heating apparatus and a fluid heating system according to the invention will now be described with reference to and as shown in the accompanying drawings in which: Figure 1 is a sectional view through a cylinder and tank assembly; and Figure 2 is a plan view of the assembly of Figure 1.

A water heating system, for example for heating domestic hot water, has a hot water cylinder 10, usually of copper, into which cold water is supplied through a cold water supply pipe 11. The cold water supply pipe 11 feeds the bottom of the cylinder 10.

Heated water is taken from the cylinder through a pipe 12. Conventional heating means such as an immersion heater 13 are included in the cylinder 10.

Further heating apparatus comprises a solar panel (not shown) of which there are many types available and which allow energy from the sun to be harnessed to heat fluid flowing through the panel. Fluid having being heated in the solar panel is passed through piping 14 into a heat exchanger 15 positioned in the cylinder 10. Afoot tank 16 surrounds a base portion of the cylinder 10 up to a depth equal to approximately one third of the height of the cylinder 10, although the base portion of the cylinder may be surrounded up to different depths.

Fluid having passed through the heat exchanger 15 discharges into the foottank 16.

The foot tank 16 is shaped so that fluid from the solar heating system surrounds the cylinder 10. The tank 16 is shaped to permit the cold water supply pipe 11 to enter and provides a sump for a ball valve 17. The pump (not shown) is mounted on the base of the tank 16 to circulate fluid through the solar heating system and the pump urges fluid out of the tank 16 at outlet 23 and through return pipe 18 to the solar panel.

The ball valve 17 previously mentioned controls a branch supply of water from the cold inlet pipe 11 into the tank 16. This arrangement allows the fluid level in the tank 16 to be maintained at a desired level, indicated in Figure 1 by the line 19. If fluid is lost from the solar heating system, the ball valve will open the branch supply and replenish the system to the desired level.

The desired operating level 19 of the fluid in the solar heating system corresponds to the level of blocked in portion 20 of the tank. In this way, the surfact area of fluid in the tank 16 over which heat can be lost other than to the cylinder 10 is minimised.

Since conventional cylinders 10 have a concave base 21, it is possible for air to become trapped below the base 21. In order to overcome this problem and to maximise the area of contact between the solar heated fluid and the cylinder 10, a siphon pipe (not shown) may be positioned with one end near the centre of the base 21 of the cylinder and the other end lying on for example, along a vertical side of the cylinder above the level of the first end. In this way, air trapped by the concave base 21 of the cylinder will be allowed to escape.

The walls of the tank 16 are shaped so that a space indicated at 22, not used when the system is in operation, is provided to allow all fluid in the solar heating system to drain into it. This feature offers the significant advantage of being able to empty the solar panel at night or in cold weather, to prevent any risk of fluid freezing in the solar panel and thereby causing damage. Furthermore, when the system drains back into the foot tank 16, the fluid in the solar heating system will be as hot as the base portion of the cylinder 10. As soon as hot water is drawn off from the cylinder 10, this heat can be given up to incoming cold water, so that heat from the solar heating system is not wasted.

It will be appreciated that the exterior surfaces of the tank 16 are insulated to prevent heat loss.

Afurther advantageof this system is that the total heat exchange surface is considerably increased compared to just a pipe coil in the hot water cylinder.

The significance of this advantage is that in a solar heating installation, the heat from the sun is low grade heat, and in order to improve efficiency, heat transfer fluid should be at a temperature only just above the temperature of water to be heated. This requires a highly efficient heat exchanger. Further to this, in a practical application, the quantity of heat transfer material must be kept to a minimum otherwise energy is wasted by heating it. Many solar heat absorbing panels in order to reduce the heat transfer liquid to a minimum have only a few pipes in them into which heat is transferred for example, metal plates. This generally is less efficient than a panel with a complete film of heat transfer liquid absorbing the solar heat. However, the latter type of solar heat absorbing panel inevitably means a larger volume of heat transfer liquid which would reduce system efficiency. By using a system incorporating a tank as described in the preferred embodiment, the quantity of fluid in the system becomes less critical since more heat is given up to the water in the cylinder.

Claims

1. Solar heating apparatus for heating fluid in a cylinder which apparatus comprises a solar panel, heat exchanger means positioned in use in the cylinder through which heat exchanger means fluid from the solar panel passes, fluid container means for surrounding a portion of the cylinder into which fluid container means fluid from the heat exchanger means flows, outlet means from the fluid container means connected to the solar panel to allow return of fluid to the solar panel and means for circulating fluid through the solar heating apparatus.

2. Solar heating apparatus as claimed in claim 1 in which the circulating means is a pump.

3. Solar heating apparatus as claimed in claim 1 or claim 2 in which the fluid container means is a tank surrounding in use a base portion of the cylinder.

4. Solar heating apparatus as claimed in claim 3 in which the tank in use surrounds the cylinder up to a depth not greater than one third of the height of the cylinder.

5. Afluid heating system comprising a cylinder having a cold fluid inlet adjacent the base of the cylinder, a hot fluid outlet adjacent the top of the cylinder and the solar heating apparatus as claimed in any preceding claim.

6. A fluid heating system as claimed in claim 5 in which the cylinder is provided with an immersion heater for heating fluid in the cylinder.

7. A fluid heating system as claimed in claim 5 or claim 6 in which the cold fluid inlet is supplied through a pipe, there being a branch supply from the cold fluid supply to the fluid container means, there being valve means to control supply of fluid through said branch supply to maintain fluid level in the fluid container means at a substantially constant level.

8. Afluid heating system as claimed in claim 7 in which the valve means comprise a floating ball valve.

9. A fluid heating system as claimed in any one of claims 5 to 8 in which the dimensions of the fluid container means and the fluid level in the fluid container means in use are such that when fluid is no longer circulated through the solar heating apparatus, said solar heating apparatus fluid is able to drain into and to be contained in the fluid container means.

10. A fluid heating system as claimed in any one of claims 5 to 9 in which the cylinder is formed with a concave base, a siphon pipe being arranged with one end lying adjacent the centre of the base of the cylinder and the other end lying at a level above the level of said one of the siphon pipe.

11. A fluid heating system substantially as hereinbefore described with reference to and as shown in the accompanying drawings.