How does a solar thermal heat pump with SPRING MAX panels work?

Solar thermal heat pumps operate on the same principle as a geothermal heat pump, i.e. calories are drawn from the environment (via solar panels here) and transported via a heat transfer fluid to supply the heat pump's evaporator.

The heat pump is the central component and controls the fluid flows in the cold circuits and hot of the system.

The cold circuit (to the left of the heat pump) captures the calories present in the air outside the house and in solar radiation, via the heat exchanger integrated into the back of the Dualsun SPRING4 panel, and transmits them to the evaporator of the heat pump.
This circuit must be filled with a heat transfer fluid containing antifreeze (as little viscous as possible at low temperature): Which glycols are compatible with SPRING4 panels? 

A specific feature of the integration of solar panels into this circuit is the use of a mixing valve (thermostatic or electronic), as shown in the figure above, protecting the heat pump evaporator from excessively high temperatures that can come from the solar field, particularly during the summer period.

The hot circuit (to the right of the heat pump) distributes the calories generated by the heat pump to the various heating circuits (radiators and/or underfloor heating) and domestic hot water in the house. This heat is produced using the electrical energy consumed by the compressor in addition to the calories captured by the evaporator in the cold circuit.

Here is a video system presentation which summarizes the operation of a heat pump system coupled with our SPRING MAX hybrid solar panels.

The system operates during night and bad time thanks to the specially designed SPRING4 panel to effectively capture calories present in the air in addition to those present in the sun if there are any.

During operation, the heat pump uses the cold source a temperature delta more than an absolute temperature. So if the heat transfer fluid enters the heat pump evaporator at -5°C and comes out at -10°C for example, the efficiency of the heat pump remains very good.

In this example, even if the air temperature is negative, the fluid will be “heated” as it passes through the heat exchanger of the solar panels.

The heat pump therefore operates day and night, whether the weather is nice or cloudy, even with negative outside temperatures (up to the limit given by the minimum temperature on the evaporator side of the heat pump, after which the electrical backup takes over).

For more details on the impact of the various phenomena that can occur on the heat exchanger of SPRING MAX panels operating in the middle of winter, consult this FAQ: What is the impact of condensation, frost or snow on the performance of a solar thermal system with SPRING4 MAX solar panels?

A water/water heat pump has a maximum temperature limit at the inlet of its evaporator, lower than the stagnation temperature of the SPRING4 MAX panels, which is 63°C. This is why we recommend installing a mixing valve on the return of the panels, the setpoint of which will be adjusted according to the maximum limit of the heat pump.

When the heat pump is started to heat the domestic hot water, the mixing valve (see technical diagram above) mixes the hot return from the panels with the cold flow from the collection to reach the maximum inlet temperature of the heat pump.

Due to the stagnation temperature of the panels at 63°C, there is no risk for the installation when it is stopped.

To observe the operation of a mixing valve you can watch this video: Install ESBE Controller - CRA

Here is an example of summer operation in Marseille when the temperature of the solar panels was 45°C with a mixing valve setpoint at 30°C. We see that following the activation of the circulator in the collection circuit, the flow in the solar installation is limited by the activation of the mixing valve. This prevented excessively hot temperatures (> 35°C, the valve setpoint) at the evaporator inlet despite a higher temperature measured in the panels.

> To find out the list of PACs compatible with this coupling, consult this FAQ.
> To find out how to install and use a solar thermal heat pump, consult the solar thermal heat pum p manual.