GB2550584A

GB2550584A - Solar Heating System

Info

Publication number: GB2550584A
Application number: GB1609039.1A
Authority: GB
Inventors: Thomas Dearman Peter
Original assignee: Greenline Renewables Ltd
Current assignee: Greenline Renewables Ltd
Priority date: 2016-05-23
Filing date: 2016-05-23
Publication date: 2017-11-29
Anticipated expiration: 2036-05-23
Also published as: GB2550584B; GB201609039D0

Abstract

A solar heating system comprises a solar panel 16, hot water tank 4 and a heat exchanger 12. The solar panel is thermally connected to the heat exchanger via a first closed circuit 18 and the hot water tank is thermally connected to the heat exchanger via a second open circuit 14. The second open circuit includes a supply conduit 6 that draws water from the tank and a return conduit 28 that returns water heated by the heat exchanger to the tank. Ideally the supply and return conduits of the second circuit are at least partially contained within a T-piece 32 fluidly connected with an outlet 30 of the tank and a hot water discharge outlet 24, e.g. a tap, such that the supply and return conduits share a common connection to the tank. The first and second circuits ideally include respective pumps 22,8 and temperature sensors 10,26. A cold water tank 2 and cold water tank inlet 20 may be provided and water in the tank may also be heated by an immersion heater or heating coil connected to a central heating system.

Description

Solar Heating System

The present invention relates to additional solar power for household hot water systems and more specifically to retrofitting of solar panels heated fluid circuits to augment conventionally plumbed and fossil fuel powered hot water systems.

There are a number of types of hot water system used in both residential and commercial property, most, though not all employ a hot water cylinder to store heated water, in preferably the most efficient way possible. The hot water cylinder is typically made of copper and is heavily insulated either by removable external thermal jackets or, more usually is contained within a foam insulation.

With a view to overcoming the preceding disadvantages, the present invention provides a solar heating system as set for in claim 1 of the appended claims.

The invention will now be described further by way of example with reference to the accompanying drawings in which

Figure 1 is a schematic diagram of a hot water system according to the present invention.

Figure 1 shows a conventional hot water circuit that has been provided with the additional features of a solar system. This results in a hot water system according to the present invention. The additional features require no modification to the conventional components and are connected in such a way as to be entirely reversible, using only conventional tools.

The diagram shows a hot water cylinder 4 supplied with cold water via a cold water inlet 20 at its lower end fed by a cold water tank 2. The level of water within the cold water tank is maintain at a higher level than the water in the hot water cylinder in order that the weight of the cold water in water tank 2 is sufficient to push water from the highest point of the hot water cylinder via hot water outlet 30.

The hot water cylinder 2 is typically heated by a coil (not shown) connected to the central heating system. The coil acts like any other radiator within the property except that heat is passed into the water in the cylinder rather than to the air around the radiator. As the water in the cylinder is heated it rises to the top of the cylinder displacing the cold water. This results in a temperature gradient increasing as you climb up the cylinder 2.

Heat is supplied to the coil from the central heating system under the control of a thermostat (not shown) connected to the tank. It measures the temperature of the water in the tank and shuts off the supply of heat to the coil when the temperature reaches a threshold level. The hot water cylinder 4 is typically very well insulated, this means that when the hot water in the cylinder remains unused it loses little heat. If a small temperature drop is detected by the thermostat the central heating system provides heat by of hot water to the inside of the coil to heat the water in the cylinder back up to the thermostat threshold temperature. This uses little energy as only the heat loss is compensated for. If a significant amount of the hot water in the cylinder is used, for example for a shower or a bath, the egress of hot and influx of cold water drops the temperature in the cylinder 4 substantially, and so more energy is required from the central heating system to recover to the threshold temperature of the thermostat.

Another source of heat includes an emersion heater (not shown) which is an electric element such as found in a kettle which is introduced into the cold water cylinder about half way up. This is provides an emergency back up heat source in the event of failure of the central heating system. It is considered a fall back as electrical heating of water is much more expensive than typical gas fired central heating systems.

The outlet 30 is connected to the hot water output system of the property indicated generally by reference 24. When any tap is open, the weight of water in cold water tank 2 forces cold water into the bottom of the tank via input 20 and hot water out of the hot water outlet 30 and ultimately out of the tap.

The level of cold water within the cold water tank 2 is maintained by a float valve connected to the mains water supply such that as the hot water is emptied from the cylinder 4, and is replenished by the cold water in cold water tank 2, the float valve opens the supply from the mains to refill the cold water tank.

The above description relates entirely to the workings of a gravity fed conventional hot water system within a property having a central heating system of some kind. There are other types of hot water system, but for the purposes of explaining the present invention, it is not necessary to discuss others.

Turning now to the features of the present invention, the solar powered hot water system includes a solar panel 16 and a heat exchanger 12 that are fluidly connected by a closed first circuit 18 of heat transfer fluid. This may be water or another suitable fluid. The fluid in the closed circuit 18 is circulated by way of a pump 22 between the heat exchanger and solar panel. The first circuit 18 is considered closed as the same fluid circulates inside it at all times. The solar panel 16 is placed in sight of the sun, typically on the roof of a building to absorb solar radiation in the form of heat. The heat is absorbed by pipework in the solar panel, resulting in heating of the fluid within the closed circuit 18. The newly heated fluid in the first closed circuit 18 is pumped by pump 22 to heat exchanger 12 where the fluid transfers its heat to water pumped from the hot water cylinder 4 in an open second circuit 14 external to the cylinder 4.

The second circuit 14 is considered open as the water flowing through it is renewed from the water cylinder 4 in an ongoing basis.

The second circuit 14 is comprised of a flexible cold water supply conduit 6, a pump 8, the heat exchanger 12 for absorbing heat from the closed first circuit 18, and a return conduit 28.

The second circuit is introduced into the hot water output system 24 from the cylinder 4 by means of a t-piece 32. The cold water supply to the second circuit is achieved by feeding the flexible cold water supply conduit 6 through the T-piece 32 then concentrically through the hot water outlet 30 until it reaches approximately the bottom of the hot water cylinder 4.

The heated output from the heat exchanger 12 is fed through the T-piece 32 into fluid communication with the hot water outlet 30 of the cylinder 4. This allows water to flow into the second circuit regardless of the direction of flow of water at the hot water outlet 30.

In the event that no tap within the hot water output system is open, water will flow from the return conduit 28 of the second circuit through the T-piece 32 and into the top of cylinder 4 by way of the hot water outlet 30, gradually increasing the temperature of water in the cylinder 4 by supplementing its heat loss with energy recovered from the sun.

In the event that at least one tap is open, hot water will flow from cylinder 4 through hot water outlet 30 to the tap(s) via hot water output system 24. At the same time, pump 8 will draw cold water from the bottom of cylinder 4 through cold water supply conduit 6 and after heating it via heat exchanger 12, supply it back into hot water output system via T-piece 32. Due to the direction of flow of water from the cylinder to the open tap, the solar heated water will simply augment the hot water supplied from the cylinder until all hot water taps are closed. The solar heated water will then aid in restoring the cylinder to the desired temperature following the ingress of cold water resulting from it being partially drained.

While it is possible for the pumps 8 and 22 to operate at all times, this wastes electrical energy. It can additionally result In heat energy from the hot water cylinder 4 being dissipated by the solar panel 16 to the atmosphere when the fluid in the first circuit 18 is cooler than the water in the second circuit 14.

To prevent this, the solar heating system is provided with temperature sensors 10 and 26. Sensor 10 is arranged in communication with the first fluid circuit 18 and sensor 26 with the second circuit 14. It may also be feasible to use the existing temperature sensor connected to the hot water cylinder used by the hot water system for determining when the water should be heated conventionally.

Both pumps should be actuated to turn on simultaneously in the event that the fluid in the first circuit 18 is warmer than the water in the cylinder 4. Ideally the temperature of the fluid as indicated by sensor 10 should be a minimum of approximately 40 degrees centigrade before the pumps are enabled. The pumps are disabled in the event that the temperature input from sensor 26 is higher than that of sensor 10. The pumps are similarly disabled when the temperature of the water in the cylinder reaches a maximum value, typically around 70 degrees centigrade. For versatility of set up, the temperatures at which the pumps are activated or deactivated are variable by the user. 2 Cold Water Tank 4 Hot Water Cylinder 6 Flexible Cold Water Supply Conduit 8 Second Circuit Pump 10 First Circuit Temperature Sensor 12 Fluid/Fluid Heat Exchanger 14 Second Open Circuit 16 Solar Panel (Air/Fluid Heat Exchanger) 18 First Closed Circuit 20 Cold Water Inlet 22 First Circuit Pump 24 Hot Water Output System 26 Second Circuit Temperature Sensor (optional) 28 Return Conduit 30 Hot Water Outlet 32 T-Piece

Claims

1. A solar heating system for connecting to a hot water tank (4), the system comprising; a heat exchanger (12) for transferring heat between; a first closed fluid circuit comprising a solar panel (16) a circulation pump (22), and a second fluid circuit having a supply conduit (6) for drawing water from the hot water tank, and a return conduit for returning water to the hot water tank (4); characterised in that a second circulation pump (8) is provided for circulating water in the second circuit and the supply and return conduits are arranged one inside the other to permit a common connection of the conduits to the hot water tank.

2. A solar heating system as claimed in claim 1, further comprising a temperature sensor (10) arranged within the first fluid circuit and configured to activate the second circulation pump (8) in dependence upon the temperature of the fluid within the first closed fluid circuit.

3. A solar heating circuit as claimed in claim 2, further comprising a second temperature sensor (26) arranged to measure the temperature of incoming water through the supply conduit (6) and configured to de-activate the second circulation pump (8) when the temperature of the fluid in the first closed fluid circuit is less than the temperature of the incoming water from the hot water tank (4) in the supply conduit (6).

4. A solar heating system as claimed in claim 2 or 3, wherein the second circulation pump (8) is activated when the temperature of the fluid in the first circuit is greater than 40° Celsius.

5. A solar heating circuit as claimed in claims 1 to 4, wherein the supply conduit (6) is a pipe having a length extending beyond a length of the return conduit, such that when connected to the hot water tank, the supply conduit draws colder water from the bottom of the tank and the return conduit returns hotter water to the top of the tank.

6. A solar heating circuit as claimed in any preceding claim, in combination with a hot water tank (4).