Are Dualsun SPRING panels compatible with water-to-water heat pumps?

Yes, Dualsun SPRING hybrid panels can be installed in combination with glycoled water-to-water heat pumps (GWHP). 

When the hybrid panels are installed on the heat pump collection circuit, the use of the non-insulated version of the PVTs, which has a higher efficiency at low temperatures compared to the insulated version, is recommended.

For more details, see these online articles:

• What is the thermal output of the SPRING panel ?

• What is the difference between the insulated and non-insulated panel ?  

This coupling offers a dual service system providing both domestic hot water and space heating (or even triple service with pool heating).

Several configurations are possible, depending mainly on the characteristics of the heat pump, the available cold sources and the height of the solar installation. We explain these different configurations in this article. 

When our SPRING panels are installed on the collection circuit of a heat pump, they provide an efficient cold source for the heat pump, thus improving the performance of the system and ensuring your heating and hot water needs in winter as well as in summer.
In fact, in addition to the self-consumption of the electricity produced by their front face, the heat recovered by the exchanger on their rear face is effectively used by the heat pump.

The mixing valve at the outlet of the hybrid panels panels is necessary to prevent excessively high temperatures from the solar field from reaching the heat pump evaporator, especially in summer.

It should be noted that the use of the non-insulated version of the hybrid panels, which have greater efficiency at low temperature compared to the insulated version, is recommended when they are integrated into the primary circuit of the heat pump.

To make a proper sizing of your installation you can check : How many Dualsun SPRING panels are necessary to provide heat to a ground source heat pump ?

We will explain to you in the rest of this article the other possible diagrams of this coupling according to the characteristics of the project.

Indeed, particular attention should be paid to the operating limits of the heat pump with the simplest diagram presented above:

• The maximum allowable temperature at the evaporator inlet: if it is lower than the stagnation temperature of the non-insulated hybrid panels (see here What is the stagnation temperature of the Dualsun SPRING panel? ), a mixing valve should be installed upstream of the evaporator. The setpoint temperature of this valve will be set according to its reaction time: generally speaking, it is wise to set a temperature slightly lower than the maximum temperature limit.

• The minimum admissible pressure at the level of the evaporator: expressed in bar, if it is lower than the height of the solar installation in relation to the evaporator expressed in meters divided by 10 (see this article online for better understanding of  the mechanical relaxation effect  SPRING which naturally leads to a drop in pressure following commissioning): Pmin[bar] < ((Hhybrid panels-HHP) [m])/10

it is important to separate the solar circuit from the evaporator circuit. It can be done by adding a hydraulic separator or an intermediate cold buffer tank (see configurations 2 below).

As mentioned in the previous section, when the height of the solar installation is not sufficient to ensure the minimum pressure limit to the evaporator, it will be important to hydraulically separate the solar and heat pump capture circuits.
To do this, a plate heat exchanger or a small intermediate pressure-breaking cold tank should be added between the SPRINGs and the heat pump evaporator. In these cases, an additional solar circulator will be required.

The solar circulator will be activated at the same time as the activation of the heat pump collection circuit circulator. Consequently, the circulator will be controlled by the heat pump and no additional regulator will be necessary.

In situations where the space inside the technical room allows it, and if the surface of the panels is substantial, it may be interesting to add an intermediate cold buffer tank between the hybrid panels and the heat pump. In addition to hydraulically separating the two circuits, it will have the effect of increasing the inertia of the hybrid panels by taking advantage of the solar thermal contribution at times of best sunshine during the day:

In this configuration, in addition to the solar circulator, a solar regulator and two temperature sensors will be required to control the solar circuit. The temperature probes will be inserted in the hybrid panels and in the bottom of the tank. The solar circulator is only activated when the temperature difference between these two sensors is sufficiently positive.

In order to make the most of solar thermal energy during spring, autumn and summer (when the solar thermal potential is sufficient), hybrid panels can also bring solar thermal energy directly to the bottom of the domestic hot water buffer tank for free by passing the HP. In the case of direct coupling, this option can be illustrated by the following diagram:

Even if this configuration makes the system a bit more complicated, it could have the advantage of extending the life of the heat pump by requiring it significantly less (or even never depending on the location of the installation) during the summer period.

Here we present the configurations with an W/W heat pump with a double cold source. Only heat pumps capable of managing several heat sinks can be used in these configurations.

More specifically, the programming of the heat pump must know how to manage the two 3-way valves marked A and B on the diagrams below. This makes it possible to optimize the performance of the system by drawing the calories from the cold source thehotter offering greater energy potential.

The only cold source of the heat pump here is geothermal energy. The integration of our hybrid panels panels serves to significantly improve the performance of such a system thanks to both the electricity produced which could be self-consumed and the recovered thermal energy which could be used to recharge the geothermal probes offering a medium suitable seasonal storage of useful solar energy.

> To go further : How many Dualsun SPRING panels are necessary to provide heat to a ground source heat pump ?