Where are the PV cells of the DualSun panels manufactured?

The PV cells of the hybrid PVT DualSun panel are sourced in Taiwan.

It is important to note that the PV cells represent only 25% of the added value of the hybrid PVT DualSun panel whereas more than 55% of the added value of the DualSun panel is French.

Are the DualSun panels approved for the RHI scheme in the UK?

DualSun panels are not yet registered in the government financial incentive for the use of renewable heat (Renewable Heat Incentive) among the eligible technologies yet. However, we are working on including the RHI scheme soon.


What is the maximum mechanical load for DualSun panels?

During certification testing of the DualSun panels, the TÜV Rheinland laboratory results demonstrate that the DualSun panels with the appropriate mounting system can resist a maximal positive mechanical load (ex. snow) of 5.400 Pa and maximum negative load (ex. strong winds) of 2.400 Pa.

Moreover, the DualSun Wave panel (stainless steel version) underwent additional tests and can resist a max positive load of 6.600 Pa, which is particularly important for installations in high-altitude mountain ranges.

For the DualSun Spring panel, here is part of the Solar Keymark report  (report-21236476) regarding mechanical loads:

What is the link between the normative power output Wth/m2 and the a0 coefficient (optical efficiency)?

The thermal power output (Wth/m2) listed on the front page of the technical data sheet is a normative value calculated from the η0 coefficient (0.57) determined during the Solar Keymark certification (n°011-7S2783 P) and a reference insolation G = 1000 Wth/m2:

Thermal power output = 0.57 x 1000 = 570 Wth/m2

The a0 and a1 values on the backside of the datasheet are characteristics used in modelling software to simulate thermal performances of panels with a wind applied in order to best simulate real-life conditions:

a0 = η0 – c6 * windspeed

a1 = c1 + c3 * windspeed

In the Spring datasheet, a windspeed of 1m/s is applied to determine a0 and a1 values in order to be consistent with module power values given on the first page of the Solar Keymark annex.

For more information, please consult our article on the subject.

Does the hybrid concept of the DualSun panel have an impact on the backsheet?

No. The presence of the heat exchanger on the backside of the panel has no impact on the backsheet’s durability.

Moreover, with a stagnation temperature of 80°C, the panel’s temperature also does not have an impact on the backsheet’s durability.

The Isovolta backsheet used for DualSun panels undergoes a temperature of 150°C during the lamination process and maintains all of its properties.  Also, during certification testing, the DualSun panel underwent TC200 (thermal cycling with 200 cycles from -40°C to +85°C) and DH (humid heat: 85°C et 85%H), each test lasting approximately 1.5 months (1,000 hours).

Moreover, Isovolta has also validated 2,000 hours of DH without issues and indicates on their technical datasheet: “”Relative Temperature Index (RTI): 105°C”.  The “Relative temperature index (RTI)” is the maximum service temperature at which the important properties of the material are not impacted by thermal-chemical degradation.

Is there a risk of clogging within the polypropylene heat exchanger over time?

No. Clogging occurs by metallic corrosion. The material of the DualSun heat exchanger is a polymer and will not be affected, but other elements of the circuit could be affected:

The pressure of the circuit will tend to force out oxygen by diffusion through the polymer lining, nonetheless we recommend to:

  • make sure to degas the system correctly during commissioning,
  • use systematically demineralised water and an anti-corrosion glycol (TYFOCOR) during filling of the closed circuit.

What happens if there is a leak in the panel?

The DualSun panel has undergone numerous accelerated ageing tests to guarantee that the heat exchanger will not have any leak issues.

In the case a leak does occur, we must remember that the DualSun panels have successfully passed the complete set of electric tests associated with the photovoltaic certification (IEC 61215 and 61730), taking in consideration the combined PV/T aspect of the DualSun panel.

In fact, DualSun is the first panel in the world to integrate the “hybridisation” aspect of the panels in the certification tests.

Furthermore, an important test including in the certification (“Wet leakage current test”) which includes full immersion of the panel in water, confirms that the DualSun panels maintain full electric operation, even in full contact with water and humid conditions.

Isn’t there a risk that a polymeric heat exchanger impedes the heat transfer efficiency of the panel?

We often think that polymeric materials are not adapted for efficient heat transfer: everything is relative.

We must keep in mind that the photovoltaic laminate is composed of multiple layers that are not good thermal conductors: glass, EVA film, back sheet (also a polymeric material).  Each of these layers has a thermal resistance that accumulates to give the global thermal resistance of the photovoltaic laminate.

Behind the photovoltaic laminate, we are adding a polymeric thermal heat exchanger with a skin width of 0.7mm.  Indeed the polymer is not a great thermal conductor, but it comes after the PV laminate which is even less so!  In other words, the “thermal resistance” of the heat exchanger is negligible as compared to the thermal resistance of the PV laminate.  And thus the heat that arrives on the backside of the PV laminate will efficiently transfer to the water in the heat exchanger, despite the fact that the heat exchanger is made of polymer.

The result is quite remarkable: the thermal power output of the DualSun Spring panel (with a polymeric heat exchanger) is only 2% less than the DualSun Wave panel with a stainless steel heat exchanger, normally considered to be a good thermal conductor!


What is the design of the Spring heat exchanger?

The polypropylene heat exchanger of the DualSun Spring panel is composed of 188 canals, each with a 5mm exterior diameter, and two collectors which serve to distribute the liquid through the canals.

This design is specific to DualSun and protected by international patents.