GB2106633A

GB2106633A - Solar heater

Info

Publication number: GB2106633A
Application number: GB08128527A
Authority: GB
Inventors: Norman Brown
Original assignee: Individual
Current assignee: Individual
Priority date: 1981-09-21
Filing date: 1981-09-21
Publication date: 1983-04-13

Abstract

A solar heater comprises a relatively shallow large-diameter concave dish (11). A spiral of tubing (12) is coiled inside the dish adjacent its concave surface with a fluid-entry at or towards one end of the spiral and a fluid-exit at or towards the other end thereof. Respective and separate power-driven motors move the dish about azimuth and altitude axes so as to keep it trained on the sum. A reflective surface moving with the dish reflects the sun's rays onto the back of the spiral coil so that the front of the coil is heated by direct solar- radiation, the back of the coil is heated by a combination of reflection from said surface and conduction from the heated front of the coil, and the risk of the coil being warped by excessive direct radiant heat is minimised. A lens system (16) may be supported across the dish and a translucent cover (17) may cover the dish, the enclosed space containing nitrogen. <IMAGE>

Description

SPECIFICATION Solar-based fluid-heating apparatus The invention relates to solar-based fluid-heating apparatus.

Apparatus of this general kind has been proposed and known for some years now. The so-called solar heating panels sometimes seen mounted in the roofs of domestic buildings are one example of such apparatus. However the general principle of solar-based fluid-heating systems has not yet received widespread acceptance. For example the solar heating panels just referred to suffer the obvious drawback that they have to be positioned so as to catch a proportion of the sun's rays but they cannot, in general, move to accommodate the change in angle of the sun. They are therefore not efficient and, at best, they can provide only relatively modest amounts of fluid-heating.

The invention seeks to exploit the potential heating effect of the sun's rays in an altogether more efficient and carefully-thought-out manner.

According to the invention in its broadest aspect a solar-based fluid-heating apparatus comprises a relatively shallow large-diameter concave dish; a spiral of tubing coiled inside the dish adjacent its concave surface with a fluid-entry at or towards one end of the spiral and a fluid-exit at or towards the other end thereof; means to move the dish about respective azimuth and altitude axes so as to keep it trained on the sun; and a surface which moves with the dish to reflect the sun's rays onto the back of the spiral coil.

Thus the front of the coil is heated by direct solar radiation, the back of the coil is heated by a combination of reflection from said surface and conduction from the heated front of the coil, and the risk of the coil being warped by excessive direct radiant heat is minimised.

With the coil so heated from both sides, and the dish trained constantly on the sun, the sun's rays can be used to maximum effect to heat fluid flowing through the coil.

Said surface reflecting onto the back of the coil may be the concave surface of the dish itself, suitably treated. Alternatively or additionally, other surfaces (for example lens surfaces and/or mirrors) may be mounted on the dish for this purpose.

Preferably a lens (or a lens system) is mounted on the dish in front of the coil to direct the sun's rays onto said surface which reflects onto the back of the coil. Such a lens or lens system could also intensify the rays impinging directly onto the front surface of the coil.

Preferably such an intensifying lens (or lens system) mounted in front of the coil is protected by a cover which can be moved-possibly automatically-across the lens or lens system, and/or across the coil, to shield the lens or lens system (and/or the coil as the case may be) from the sun in certain circumstances.

The coil, the reflecting surface or surfaces of the dish, and any lenses are preferably encapsulated in a translucent envelope containing an inert gas, for example nitrogen.

This together with the other preferred features outlined helps the apparatus to function at optimum efficiency.

One apparatus embodying the invention is shown in the accompanying drawing. It will now be described with reference to the drawing. It is only one example of forms which the apparatus might take within the broad inventive concept.

The apparatus consists essentially of a relatively shallow iarge-diameter concave dish which in the drawing is referenced 11. Coiled inside this dish adjacent its concave surface is a spiral 1 2 of tubing. A fluid-entry is defined at or towards the outer end of the spiral 1 2 and a fluid-exit is defined at or towards the centre of the spiral.

In this particular apparatus the spiral of tubing starts adjacent the outer edge of the dish 11 and spirals inwards towards the centre.

If the apparatus is operating in the Northern Hemisphere the spiral 1 2 is a right-hand spiral. If the apparatus operates in the Southern Hemisphere the spiral is a left-hand spiral. In either event the dish 11 is of relatively shallow concavity in relation to its diameter but is sufficiently deep to accommodate the spiral within it.

The spiral 1 2 need not necessarily be planar when viewed end-on. It could for instance sink into the dish as it travels inward towards the centre of the dish, so that the tubing is at substantially the same distance from the dish surface throughout the spiral.

The dish 1 2 is held between the extreme ends of a 'wish-bone' mounting 1 3. It is pivotally secured at each such extremity so that it moves about an axis which, with the apparatus on level ground, is substantially horizontal. The wishbone 1 3 is itself mounted for pivotal movement about another axis 14 set into the base structure 1 5 of the apparatus.

Separate motors, not shown in any detail or referenced in the drawling, drive the dish 11 about its horizontal pivot axis and drive the wishbone 1 3 about its vertical pivot axis. This particular apparatus is a large-scale installation and the motors are controlled by a microprocessor and associated electronic circuitry which is programmed to keep the dish trained constantly on the sun by moving the separate pivot-axis drive motors as the sun waxes and wanes throughout the course of normal daylight hours.

A lens system 1 6 is carried across the front of the dish 11 and mounted in front of the coil 1 2. The individual lenses of this system split the direct radiant solar energy impinging on the system onto the suitably-treated concave surface of the dish 11. The incoming radiant heat is reflected from that surface onto the back of the spiral 1 2 and is also rereflected by the central lenses of the system 1 6 onto the front surface of the coil. Thus the risk of warping the coil by excessive heating from one side only is minimised.

The lens system 1 6 also intensifies the rays impinging directly onto the front of the coil 12.

The treated concave surface of the dish 11, the spiral 12, and the lens system 1 6 are all encapsulated in a translucent glass envelope 1 7 containing nitrogen. The envelope 1 7 is gas-tight and in this particular apparatus it is made of suitably toughened glass.

A shutter 1 8 of the camera-shutter type shields the glass envelope 1 7 and its contents from the sun's rays when the shutter 1 8 is closed. During normal use of the apparatus for fluid-heating, the shutter 1 8 is fully opened. It is driven by electric motors, which need not be illustrated or described in any detail and are not shown or referenced in the drawing. A photo-electric cell automatically closes the shutter 1 8 in a variety of circumstances, for example if the coil 1 2 is trained on the sun with no fluid inside it; if a failure occurs at any point in the system; or when enough hot fluid has been supplied by the coil and the apparatus temporarily need no longer be used.

A fluid, for example water, flowing through the coil will be heated by the sun and will be heated all the more quickly by the combination of direct radiant energy and reflected heat to which the coil 1 2 is subject. Flexible armoured hoses, which again need not be illustrated in the drawing or described by any detail, would supply the initially unheated fluid from a tank or reservoir and would draw it off from the fluid-exit of the spiral. They would be sufficiently long and sufficiently flexible to move with the moving dish 11 and wishbone 1.3 as the latter two components followed the sun throughout the day.

The fluid flow path to and from the spiral 1 2 can take a number of forms. In one presently proposed form, initially unheated water is drawn from a tank and pumped through the spiral 1 2 to be heated; it is then drawn-off and returned to the tank to heat the water in the tank. A heat-exchange coil in the tank has water, or another fluid, circulating through it, and as the water in the tank is heated it gives up its heat to the fluid circulating through the heat-exchange coil. That fluid can then be used for example to run a domestic hot-water-radiator system.

In the arrangement just outlined, the water in the tank, having given up its heat to the fluid circulating in the heat-exchange coil, is heated up again by supplies of freshly-heated water from the coil 1 2. The tank may be lined for example with fire bricks to conserve heat, and the piping-possibly including the flexible armoured hoses moving with the dish 11-may also be lagged to conserve heat.

- The microprocessor control unit may incorporate an accurate quartz clock set to GMT and programmed to accommodate values of latitude, longitude, Greenwich Mean Time (GMT) and height above sea level of the site of the apparatus; and so compute the daily waxing, waning and setting of the sun.

The microprocessor controls the photo-electric cell previously referred to. As well as opening and closing the shutter 18, another function of this microprocessor is to control the rate of fluid flow through the coil 1 2. On overcast days there is little point in feeding a high, or possibly any, volume of fluid through the coil. The microprocessor may therefore be programmed to switch the fluid pump on when the atmosphere surrounding the site reaches a pre-determined degree of brightness (i.e. when the sun radiates light of a predetermined intensity); and to switch it off below that level of light intensity; and to increase or decrease the flow rate through the coil, as the light intensity varies, to maintain a steady temperature in the fluid tank.

The coil 1 2 may be coated externally to increase its heat-transferring efficiency. It could for example be matt black to absorb a greater proportion of the sun's heat.

Other modifications are within the scope of the invention and will become apparent to those skilled in this general field.

Claims

1. A solar-based fluid-heating apparatus comprising a relatively shallow large-diameter concave dish; a spiral of tubing coiled inside the dish adjacent its concave surface with a fluid-entry at or towards one end of its spiral and a fluid-exit at or towards the other end thereof; means to move the dish about respective azimuth and altitude axes so as to keep it trained on the sun; and a surface which moves with the dish to reflect the sun's rays onto the back of the spiral coil.

2. The invention of Claim 1 in which said surface reflecting onto the back of the coil comprises the concave surface of the dish itself, suitably treated if needs be.

3. The invention of Claim 1 or Claim 2 in which other surfaces, for example lens surfaces, are mounted on the dish to reflect the sun's rays onto the back of the coil.

4. The invention of any of the preceding Claims in which a lens, or a lens system, is mounted on the dish in front of the coil to direct the sun's rays onto the or each surface which reflects onto the back of the coil.

5. The invention of Claim 4 in which said lens or lens system intensifies the rays impinging directly onto the front surface of the coil.

6. A solar-based fluid-heating apparatus substantially as described herein with reference to, and as illustrated in, the accompanying drawing.

6. The invention of any of the preceding Claims in which the coil, and any lens or lens system mounted in front of it, is protected by a cover which can be moved across the coil and across any such lens or lens system to shield the coil, lens, and lens system if fitted, from the sun.

7. The invention of Claim 6 in which the cover is moved automatically into its shielding position in response to a signal from a photoelectric cell or other automatic triggering means.

9. The invention of any of the preceding Claims in which the coil, the reflecting surface or surfaces of the dish, and any lenses are preferably encapsulated in a translucent envelope containing an inert gas, for example, nitrogen.

1 0. The invention of any of the preceding Claims in which the dish is movable about its azimuth and altitude axes by respective and separate power-driven means.

11. A solar-based fluid-heating apparatus substantially as described herein with reference to, and as illustrated in, the accompanying drawing.

12. Means, relating to an essential element of the invention defined in any of the preceding Claims, for putting the invention into effect.

CLAIMS (16 July 1982)

1. A solar-based fluid-heating apparatus comprising a spiral of tubing coiled inside a concave dish with a fluid-entry at or towards one end of the spiral and a fluid-exit at or towards the other end thereof, and means to move the dish about respective asimuth and altitude axes so as to keep it trained on the sun, characterised in that the dish is a relatively shallow large-diameter concave dish; in that the coils of the spiral lie adjacent the dish surface and are spaced from that surface by substantially the same amount across the spiral; in that a lens, or a lens system, is mounted on the dish in front of the coil to intensify the rays impinging onto the front surfaces of the coils; and in that the sun's rays are reflected onto the back surfaces of the coils by a relfector which moves with the dish.

2. Apparatus according to Claim 1 and characterised in that the said reflector comprises the concave surface of the dish itself, suitably treated if needs be.

3. Apparatus according to Claim 1 or Claim 2 and characterised in that the said reflector comprises other surfaces which are mounted on the dish to reflect the sun's rays onto the back of the coil surfaces.

4. Apparatus according to any of the preceding Claims and characterised in that the spiral coil, and the intensifying lens or lens system mounted in front of it, are protected by a cover which can be moved across the coil and across the lens or lens system to shield them from the sun.

5. Apparatus according to any of the preceding Claims and characterised in that the coil, the intensifying lens or lens system, and the concave surface of the dish, are encapsulated in a translucent envelope containing an inert gas.