GB2127142A - Heating system - Google Patents

Abstract

A heating system comprises solar energy collectors (9, 10, 11, 12), a first, air/liquid, heat pump (13), a second liquid/liquid, heat pump (1) arranged to receive heat energy from the solar collectors or the first heat pump at a first temperature, and a liquid storage tank (19). The liquid storage tank is coupled to the second heat pump so that liquid contained in the tank receives the heat energy at a second temperature which is higher than the first temperature. <IMAGE>

Description

SPECIFICATION Heating system This invention relates to a heating system and more especially it relates to a liquid heating system.

The cost of energy is becoming increasingly significant and accordingly heating systems have been proposed which use the heat provided by solar panels or heat pumps. Solar panels and heat pumps however have certain disadvantages as a source of energy and one disadvantage which is common both to heat pumps and solar panels is that the heat energy provided by the heat pumps and solar panels may not always be at a sufficiently high temperature to be usable. Thus, for example, with solar panels on a cloudy day, although it may be possible to provide a sufficient quantity of heat, it may not be possible to provide heat at a usable temperature, i.e. at a usable energy level.

It is an object of the present invention to provide a heating system wherein the foregoing disadvantage is at least partly obviated.

According to the present invention a heating system comprises a solar energy collection means and/or a first heat pump, a second heat pump arranged to receive heat energy from the solar energy collection means and/or the first heat pump at a first temperature, and a liquid storage tank, the liquid storage tank being coupled to the second heat pump so that liquid contained in the said tank receives the heat energy at a second temperature which is higher than the first temperature.

Thus in a system according to the present invention, the second heat pump is used as an energy level converter whereby energy derived from the solar energy collector means or from the first heat pump at a relatively low temperature is upgraded to a higher more useful temperature.

The second heat pump may be a liquid to liquid heat pump comprising a compressor operative to circulate refrigerant around a first closed loop system including an evaporator and a condensor, the evaporator and the condensor being operatively associated for heat transfer purposes with liquid contained in a second closed loop system, the second closed loop system including the liquid storage tank and the solar energy collector means and/or the first heat pump.

The second closed loop system may comprise a circulating pump, liquid in the second closed loop system being driven by the pump from the evaporator to the solar energy collector means and/or to the first heat pump, and via the condensor and the storage tank back to the evaporator.

The system may comprise valve means operative for by-passing the second heat pump so that heat is transferred directly from the solar energy collector means and/or from the first heat pump to the liquid storage tank.

The valve means may be arranged to be controlled in dependence upon the temperature as sensed by temperature sensing means, of liquid fed from the solar energy collector means and/or from the first heat pump, whereby the second heat pump is arranged to by-passed only if the temperature sensed by the temperature sensing means exceeds a predetermined temperature.

Thus it may be arranged that the second heat pump is used only when it is necessary to raise the temperature of the liquid from the solar energy collector means and/or from the first heat pump.

Motorised valve means may be provided whereby the solar energy collector means and/or the first heat pump may be operatively coupled to the system.

The liquid storage tank may be indirectly heated and may include a heater coil through which liquid from the condensor is passed to heat the contents of the tank.

The liquid storage tank may be coupled to a first header tank via which cold liquid is supplied to make up the contents of the tank as liquid is used from the tank.

A second header tank may be provided for topping up liquid in the second closed loop system which includes the heater coil.

The first heat pump may be an air to water heat pump which is arranged to extract heat from the atmosphere.

The solar energy collector means may comprise one or more solar panels.

Some embodiments of the invention will now be described solely by way of example with reference to the accompanying drawings in which: Figure lisa generally schematic block diagram of a heating system; and Figure 2 is a table showing various modes of operation of the system shown in Figure 1.

Referring now to Figure 1, the system comprises a water to water heat pump 1. Although not shown in detail, the water to water heat pump 1 is of conventional construction and comprises a compressor which is arranged to compress a refrigerant such as Freon contained in a closed loop system, cooled refrigerant being fed to an evaporator and heat from the compressor and evaporator being transferred to a condensor.

Heat pumps which comprise a compressor, an evaporator and a condensor in a closed loop system are very well known and will not be described herein in detail.

The heat pump 1 is described as a water to water heat pump because water is used to transfer heat to and from the heat pump. Water is pumped to the evaporator section of the heat pump 1 by means of a circulating pump 2 via a pipe 3 and a valve 4. Liquid from the evaporator section is fed via a valve 5 and a pipe 6 to a motorised valve 7. The motorised valve 7 is operated to divert liquid to a pipe 8 from where it passes to a solar energy collection means in the form of solar panels 9, 10, 11 and 12, or to a pipe 8a from where it passes to an air/water heat pump 13. The solar panels 9,10, 11 and 12 are used to heat the liquid fed thereto from the evaporator and heated liquid is fed via a pipe 14 and a valve 15 to the condensor section of the water to water heat pump 1.

The heat pump 1 operates to raise the temperature of the liquid fed thereto and liquid heated by the heat pump 1 is fed via a valve 16 and a pipe 17 to the heater coil 18 of an indirectly heated water storage tank 19.

The solar panels 9, 10, 11 and 12 are operatively associated with inlet valves 20, 21, 22 and 23 respectively and output valves 24, 25, 26 and 27 respectively, whereby liquid flow therethrough can be controlled.

The air to water heat pump 13 is a conventional heat pump comprising a compressor which derives heat from atmospheric air and transfers this heat to water which is circulated in the pipe 8a. If the air to water heat pump 13 is used, the liquid fed thereto via the pipe 8a is heated by the heat pump 13 and returned to the condensor of the heat pump 1 via the pipe 28. Valves 29 and 30 are provided for isolating the air to water heat pump 13 if the solar panels only are to be used.

In order to top up the liquid level in the hot water storage tank 19, a header tank 30 is provided which is coupled to the storage tank 19 via a pipe 31. Similarly, a topping up header tank 32 is provided which is coupled via a pipe 33 to the heater coil 18 of the storage tank 19.

In order to bypass the water to water heat pump 1, bypass valves 34 and 35 are provided. In order to isolate the circulating pump 2 for maintenance purposes isolating valves 36 and 37 are provided adjacent to the input and output ports of the circulating pump 2.

In order to provide both for automatic control of the system and for system operation monitoring heat meterlng devices 38,39,40 and 41 are provided together with thermometers 42,43,44,45,46,47,48, 49, 50, 51 and 52. The thermometers are operatively associated with remote reading facilities and with a temperature recording arrangement whereby operation of the system can be monitored and recorded.

In addition to the thermometers, two thermostats 53 and 54 are provided at the top and bottom of the storage tank 19, whereby system operation can be controlled in dependence upon temperatures sensed at these points.

The apparatus shown in Figure 1 may be operated in accordance with various operational modes which will hereinafter be described and the valves shown will be opened or closed as shown in Figure 2 in accordance with the mode of operation selected.

In accordance with a first mode of operation, heat transfer liquid fed from the heater coil 18 in the storage tank 19 is circulated through the pipe 3 under operation of the pump 2. The heat transfer liquid is pumped via the evaporator section of the heat pump 1 and the solar panels 9, 10, 11 and 12 to the condensor of the heat pump 1 from where it is returned via pipe 17 to the heater coil 18 of the storage tank 19. Thus in accordance with this mode of operation of the system, heat is collected from the solar panels 9, 10, 11 and 12 and transformed to a higher temperature by the water to water heat pump 1 before being fed to the heating coil 18 of the storage tank 19.In operation of the system, the heat transfer liquid will be pumped around the system until the temperature sensed by the thermometer 44 and/or the thermostat 54, indicates that a predetermined temperature has been reached by the liquid leaving the storage tank 19. If the temperature of the liquid leaving the solar panels 9, 10, 11 and 12 is sufficiently high, it will normally be arranged that the valves 15, 16,4 and 5 are closed and the valves 34 and 35 will be opened, whereby the water to water heat pump 1 is bypassed and heat is transferred directly from the solar panels to the storage tank 19.

It will be appreciated that the temperature in the storage tank 19 will be dependent on the condensing temperature of the heat pump 1 and the full advantages of this mode of operation can only be exploited if a heat pump with a condensing temperature in the region of 80" to 90"C is used.

In accordance with a second mode of operation, heat is derived also from the air to water heat pump 13 and consequently the motorised valve 7 will be set to a modulation mode M, so that liquid from the evaporator section of the water to water heat pump 1 is fed both to the solar panels 9, 10, 11 and 12 and via the pipe 9 to the air to water heat pump 13. Thus according to the second mode of operation, heat will be provided by the solar panels 9, 10, 11 and 12 and by the air/water heater pump 13.

In accordance with a third mode of operation, the valves 34 and 35 will be opened and the valves 16, 15,4 and 5 will be closed as indicated in Figure 2. The motorised valve 7 will be controlled so that the solar panels and/or the air/water heat pump 13 will be used. In modes of operation during which both the solar panels 9, 10, 11 and 12 and the air/water heat pump 13 are used, temperatures throughout the system will be noted and the motorised valve 7 will be operated accordingly so that the correct proportion of heat is provided by the solar panels 9, 10, 11 and 12 or by the air to water heat pump 13.

It will be appreciated that the system will always be weighted in favour of use of the solar panels 9, 10, 11 and 12 since the operating cost of the solar panels is low.

Various modifications may be made to the arrangement shown without departing from the scope of the invention and for example it will be appreciated that the temperatures and operating conditions throughout the system may be monitored and controlled by means of a computer, the motorised valve 7 and other valves being operated to achieve maximum efficiency.

Claims (12)

1. A heating system comprising a solar energy collection means and/or a first heat pump, a second heat pump arranged to receive heat energy from the solar energy collection means and/or the first heat pump at a first temperature, and a liquid storage tank, the liquid storage tank being coupled to the second heat pump so that liquid contained in the said tank receives the heat energy at a second temperature which is higher than the first temperature.

2. A system as claimed in claim 1 wherein the second heat pump is a liquid to liquid heat pump comprising a compressor operative to circulate a refrigerant around a first closed loop system including an evaporator and a condensor, the evaporator and the condensor being operatively associated for heat transfer purposes with liquid contained in a second closed loop system, the second closed loop system including the liquid storage tank and the solar energy collection means and/or the first heat pump.

3. A system as claimed in claim 2 wherein the second closed loop system comprises a circulating pump, liquid in the second closed loop system being driven by the pump from the evaporator to the solar energy collector means and/or to the first heat pump, and via the condensor and the storage tank back to the evaporator.

4. A system as claimed in any preceding claim comprising valve means operative for by-passing the second heat pump so that heat is transferred directly from the solar energy collector means and/or from the first heat pump to the liquid storage tank.

5. A system as claimed in claim 4 wherein the valve means are arranged to be controlled in dependence upon the temperature as sensed by temperature sensing means, of liquid fed from the solar energy collector means and/or from the first heat pump, whereby the second heat pump is arranged to be by-passed only if the temperature sensed by the temperature sensing means exceeds a predetermined temperature.

6. A system as claimed in any preceding claim comprising motorised valve means via which the solar energy collector means and/or the first heat pump is operative coupled to the system.

7. A system as claimed in any of claims 2 to 6 wherein the liquid storage tank is indirectly heated and includes a heater coil through which liquid from the condensor is passed to heat the content of the liquid storage tank.

8. A system as claimed in any preceding claim wherein the liquid storage tank is coupled to a first header tank via which cold liquid is supplied to make up the contents of the tank as liquid is used from the tank,

9. A system as claimed in claims 2 and 8 comprising a second header tankfortopping up liquid in the second closed loop system which includes the heater coil.

10. A system as claimed in any preceding claim wherein the first heat pump is an air to water heat pump which is arranged to extract heat from the atmosphere.

11. A system as claimed in any preceding claim wherein the solar energy collector means comprises one or more solar panels.

12. A heating system substantially as herein before described with reference to the accompanying drawings.

FIGURE 2 Valve positions in different modes of the installation List of First Second Third Valves Mode Mode Mode 16 0 O C 15 0 O C 34 C C O 4 0 O C 5 0 O C 35 C C O 29 C O 0 30 C O 0 23 0 0 0 22 0 0 0 21 0 0 0 21 0 0 0 27 0 0 0 26 0 0 0 25 0 0 0 24 0 0 0 0 = OPEN C = CLOSED M = MODULATING NM = NON MODULATING (SET IN ONE DIRECTION)