GB1594711A

GB1594711A - Method of control for multi-store solar heating systems

Info

Publication number: GB1594711A
Application number: GB25547/77A
Authority: GB
Original assignee: Corbett J R G; Parkes R E
Current assignee: Corbett J R G; Parkes R E
Priority date: 1978-05-30
Filing date: 1978-05-30
Publication date: 1981-08-05

Description

(54) AN IMPROVED METHOD OF CONTROL FOR MULTI-STORE SOLAR HEATING SYSTEMS (71) We JOHN RICHARD GALLIERS CORBETT-British Subject of 32 Bibury Road, Benhall, Cheltenham, and ROBERT EDWARD PARKES of 7 Cleave Crescent, Woodford, Nr. Bude, Cornwall (late of 10 Hill Top Road, Cheltenham, Glos.)-British Subject, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention is concerned with an improved method of control for multi-store solar heating systems.

It is well known that by use of a solar absorber incident radiation can be used to heat a fluid. The heat energy in the fluid is subsequently stored by transferring the fluid from the solar absorber to a heat store. This transfer occurs when the temperature of the fluid in the solar absorber exceeds, by a prescribed difference temperature, the temperature representative of the fluid in the heat store. In this situation the fluid in the solar panel is transferred to the heat store thereby enabling it to dissipate its heat energy by raising the temperature of the heat store.

The transfer of fluid is effected by controlling a pump ad/or thermosyphon action.

This type of control is termed TYPE 1 Control. Such are simple solar heating systems.

The systems as described are unable to transfer heat from the fluid in the solar absorber to the heat store when the temperature representative of the fluid in the solar absorber is below the temperature representative of the fluid in the heat store. This situation could occur when the level of solar energy being absorbed by the panel is insufficient to raise the temperature of the fluid in the solar absorber to a difference temperature required above that of the heat store.

Hence systems employing two or more heat stores evolved. These systems direct the output of the solar absorber to the higher temperature heat store until the contents of this store exceed a prescribed temperature. Whilst the temperature of the high temperature heat store remains in excess of a prescribed temperature the output of the solar absorber is then directed to a lower temperature heat store.

Naturally occuring solar radiation varies in both intensity and duration. During periods of low intensity or during short periods of high intensity followed by periods of lower intensity a situation arises that during the period of time that the output is directed to the high temperature heat store, the incident solar radiation could cause the temperature of the fluid in the solar absorber to exceed that necessary for transfer to the low temperature heat store but insufficient heat energy is gained to raise the temperature sufficiently for transfer to the high temperature heat store and hence :no transfer of heat energy contained in the fluid within the solar panel occurs. This heat energy in the solar absorber acquired from solar radiation is subsequently dissipated by conduction convection and radiation.

An object of the invention is to minimize such losses. This is achieved by continuously monitoring the intensity of incident solar radiation with a sensor and sensors detecting the temperature of fluid in the stores and in the radiation absorber unit, the control arrangement being operative to selectively direct heated fluid from the absorber unit to a high or low temperature level store in dependence upon values detected by the sensors. A block diagram is shown in the Figure. During the time of high incident solar radiation the output of~ the solar absorber A is directed by a diverter valve B to a higher temperature heat store C and during the time of low incident solar radiation the output of the solar absorber is directed to a lower temperature heat store D.If the incident solar radiation is of a sufficiently high level to effect on increase in temperature of the solar absorber such that it would be suitable for transfer to a higher temperature heat store, but during the waiting period if the temperature difference between the higher temperature heat store and the solar absorber is not achieved within a prescribed duration of time, then the output of the solar absorber will be directed to a lower temperature heat store. Providing the required difference temperature exist between the solar absorber and the lower temperature heat store the fluid will be transferred to the lower temperature heat store, by operation of the pump E. This type of control is termed TYPE 2.

A further control is incorporated such that the output of the solar absorber is directed to the high temperature heat store until such time that the temperature of a high temperature exceeds that of a low temperature heat store by a given difference temperature. This type of control is termed TYPE 3.

A still further control is incorporated such that when the high temperature heat store is at or above a given temperature, as indicated by the temperature sensor F, the output of the solar absorber will be directed to the low temperature heat store irrespective of the level of incident solar radiation. The temperature of the low temperature heat store is indicated by the temperature sensor G. This type of control is termed TYPE 4.

The different types of control arrangements described are used in combination in the solar heating system, control being achieved by the decision device H.

A hierachy of control exists which could conveniently be in the following sequence: The TYPE 3 control will determine if the high temperature heat store exceeds the low temperature heat store by a given temperature difference and take subsequent action.

The TYPE 4 control will determine if the high temperature heat store has reached or exceeded the given temperature and take subsequent action.

The TYPE 2 control will determine the level of incident solar radiation and select the appropriate heat store for the transfer of energy at any particular time. Sensor I indicates intensity of solar radiation.

The TYPE 1 control will make the comparison between the temperature of the solar absorber and the previously selected heat store. If the prescribed difference temperature is exceeded the appropriate action will take place. Sensor J indicates temperature in solar absorber.

WHAT WE CLAIM IS: 1. A solar heating system comprising a solar radiation absorber unit, two or more heated fluid stores of respectively different fluid temperature levels, an automatic control arrangement including an incident solar radiation intensity sensor and sensors detecting the temperature of fluid in the stores and in the solar radiation absorber unit, the control arrangement being operative to selectively direct heated fluid from the absorber unit to a high or low temperature level store in dependence upon values detected by the sensors.

2. A solar heating system substantially as herein described with reference to the accompanying drawing.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. the required difference temperature exist between the solar absorber and the lower temperature heat store the fluid will be transferred to the lower temperature heat store, by operation of the pump E. This type of control is termed TYPE 2. A further control is incorporated such that the output of the solar absorber is directed to the high temperature heat store until such time that the temperature of a high temperature exceeds that of a low temperature heat store by a given difference temperature. This type of control is termed TYPE 3. A still further control is incorporated such that when the high temperature heat store is at or above a given temperature, as indicated by the temperature sensor F, the output of the solar absorber will be directed to the low temperature heat store irrespective of the level of incident solar radiation. The temperature of the low temperature heat store is indicated by the temperature sensor G. This type of control is termed TYPE 4. The different types of control arrangements described are used in combination in the solar heating system, control being achieved by the decision device H. A hierachy of control exists which could conveniently be in the following sequence: The TYPE 3 control will determine if the high temperature heat store exceeds the low temperature heat store by a given temperature difference and take subsequent action. The TYPE 4 control will determine if the high temperature heat store has reached or exceeded the given temperature and take subsequent action. The TYPE 2 control will determine the level of incident solar radiation and select the appropriate heat store for the transfer of energy at any particular time. Sensor I indicates intensity of solar radiation. The TYPE 1 control will make the comparison between the temperature of the solar absorber and the previously selected heat store. If the prescribed difference temperature is exceeded the appropriate action will take place. Sensor J indicates temperature in solar absorber. WHAT WE CLAIM IS:

1. A solar heating system comprising a solar radiation absorber unit, two or more heated fluid stores of respectively different fluid temperature levels, an automatic control arrangement including an incident solar radiation intensity sensor and sensors detecting the temperature of fluid in the stores and in the solar radiation absorber unit, the control arrangement being operative to selectively direct heated fluid from the absorber unit to a high or low temperature level store in dependence upon values detected by the sensors.