# US 4,397,301 A · Method of controlling a solar system collector loop

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- Number: US 4,397,301 A
- Document ID: US4397301A
- Status: Granted
- Kind: A
- Application number: 06/296,118
- Filed: 1981-08-25
- Granted: 1983-08-09
- Earliest claimed: 1981-08-25
- Assignees: Canadian Patents & Dev. Limited
- Inventors: Thomas Onno
- Web page: https://patentgrep.com/patent/US4397301A

## CPC

- G05D 23/1924: {using thermal energy, the availability of which is aleatory}
- F24S 50/40: responsive to temperature
- Y02E 10/40: Solar thermal energy, e.g. solar towers
- G05D: SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
- F24S: SOLAR HEAT COLLECTORS; SOLAR HEAT SYSTEMS (for producing mechanical power from solar energy F03G6/00)
- Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION

## Abstract

In a solar system collector loop, having a solar collector with an absorber plate, a heat storage unit and a pump for circulating a fluid between the collector and the storage unit, the stagnation temperature T.sub.Q of the collector absorber plate, the temperature T.sub.C of the collector absorber plate, and the storage temperature T.sub.S in the storage unit are measured. The stagnation temperature is measured by a heat flux transducer based on a small sample of the absorbed plate which is thermally isolated from the collector but in the same enclosure. This transducer generates temperatures near the stagnation condition for the instantaneous operating point. In the method of control, the pump is turned on when the temperature difference between the absorber plate T.sub.C or T.sub.Q and the storage T.sub.S, is greater than a predetermined value T.sub.on. The pump is turned off when the temperature difference between the stagnation temperature T.sub.Q and collector absorber plate T.sub.C is smaller than a predetermined value T.sub.off. The temperature signals T.sub.Q, T.sub.C and T.sub.S may also be used to control obvious abnormalities in the system as well as fast radiation changes such as those caused by small clouds.

## Claims

### Claim 1

A method of controlling a solar collector loop having a solar collector with an absorber plate, a heat storage unit and a pump for circulating a fluid between the collector and storage, comprising:
determining the temperature T.sub.C of the collector absorber plate;
determining the stagnation temperature T.sub.Q of the collector absorber plate;
determining the temperature T.sub.S of the storage unit;
computing the difference .DELTA.T.sub.C between the collector temperature T.sub.C and the storage temperature T.sub.S ;
turning the pump on when .DELTA.T.sub.C is greater than a predetermined value T.sub.on ;
computing the difference .DELTA.T.sub.Q between stagnation temperature T.sub.Q and the collector temperature T.sub.C ; and
turning the pump off when .DELTA.T.sub.Q is smaller than a predetermined value T.sub.off.

### Claim 2

A method of controlling a solar collector loop having a solar collector with an absorber plate, a heat storage unit and a pump for circulating a fluid between the collector and storage, comprising:
determining the temperature T.sub.C of the collector absorber plate;
determining the stagnation temperature T.sub.Q of the collector absorber plate;
determining the temperature T.sub.S of the storage unit;
computing the difference .DELTA.T.sub.CQ between the stagnation temperature T.sub.Q and the storage temperature T.sub.S ;
turning the pump on when .DELTA.T.sub.CQ is greater than a predetermined value T.sub.on ;
computing the difference .DELTA.T.sub.Q between the stagnation temperature T.sub.Q and the collector temperature T.sub.C ; and
turning the pump off when .DELTA.T.sub.Q is smaller than a predetermined value T.sub.off.

### Claim 3 (depends on 1, 2)

A method as claimed in claim 1 or 2 where T.sub.on consists of a fixed value minus the derivative of T.sub.Q.

### Claim 4 (depends on 1, 2)

A method as claimed in claim 1 or 2 where T.sub.off consists of a fixed value plus the integral of T.sub.Q.