Solar heating systems
View Patent ↗Solar heating systems are provided which utilize an integrated fixture for transferring heat from a solar collector to a lower-temperature loop, e.g. a domestic hot water system or radiant heating system. The fixture provides a heat exchanger for transferring heat from the solar collector to the lower temperature loop. The fixture may also include a casting, in which are formed solar collector supply and return ports, lower temperature supply and return ports, a solar collector pump volute, and a lower temperature pump volute. The systems also include two pumps, and a temperature optimization control that varies the speed of at least one of the pumps depending on the temperature of the liquid in the solar collector.
1. A method of supplying heat to a solar hot water system including a higher-temperature loop and a lower-temperature loop, the method comprising:
(a) providing a transfer system for transferring heat from the higher-temperature loop to the lower-temperature loop, the transfer system comprising (i) a higher-temperature loop pump; (ii) a lower-temperature loop pump, (iii) a heat exchanger in fluid communication with both the higher-temperature loop and the lower-temperature loop; and (iv) a controller, integrated with the pumps and heat exchanger in a single unitary fixture, configured to control the operation of the lower-temperature loop pump and higher-temperature loop pump;
(b) heating liquid in the higher-temperature loop with a solar heating unit;
(c) delivering liquid from the higher-temperature loop to the heat exchanger, so that the liquid passes through a first side of the heat exchanger,
(d) delivering liquid circulating in the lower-temperature loop to the heat exchanger so that the liquid passes through a second side of the heat exchanger, receiving heat from the liquid in the higher-temperature loop,
(e) delivering a portion of the liquid in the lower-temperature loop that has been heated in the heat exchanger to an end use;
(f) determining the temperature differential between the temperature of the liquid exiting the solar heating unit and the temperature of the liquid in the lower-temperature loop after it has exited the heat exchanger, and
(g) controlling delivery of liquid from the higher-temperature and lower-temperature loops to the heat exchanger based on the temperature differential, to maintain a setpoint temperature differential (ΔT s ) between the solar heating unit and the end use, by:
(i) calculating the actual temperature differential between the solar heating unit and the end use;
(ii) turning both pumps on when the temperature differential is greater than ΔT s and running the pumps at a speed sufficient to transfer heat from the solar heating unit to the end use;
(iii) turning off one or both pumps when the temperature in the lower-temperature loop after it has exited the heat exchanger exceeds a predetermined maximum; and
(iv) turning off one or both pumps when the temperature at the exit of the solar heating unit falls below a predetermined minimum.
2. The method of claim 1 further comprising turning off operation of both of the pumps when the temperature at the exit of the solar heating unit falls below a predetermined minimum.
3. The method of claim 2 wherein the system further includes a supplemental heat source and a reservoir in communication with the lower-temperature loop, and the method further comprises activating a supplemental pump when temperature at the exit of the solar heating unit falls below the predetermined minimum, to deliver heated liquid through a supplemental loop from the supplemental heat source to the reservoir.
4. The method of claim 1 further comprising activating a heat dump pump when the predetermined maximum is exceeded, and diverting liquid from the lower-temperature loop to a heat dump.
5. The method of claim 1 further comprising (e) using the liquid in the lower-temperature loop as potable water.
6. The method of claim 1 further comprising adding to the liquid in the higher-temperature loop an additive that would not be suitable for use in potable water.
7. The method of claim 1 wherein the solar heating unit comprises a roof-mounted collector.
8. The method of claim 1 wherein the end use comprises a water heater for a domestic water supply.