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Webinar Q&A: A recipe for improved performance

In a recent pv magazine webinar, module degradation experts took our audience through the role of temperature and mechanical stress in causing modules to under-perform. We were treated to a look at some impressive results for modules integrated with Coolback – a solution that replaces the backsheet/rear glass and frame in a conventional panel and promises lower operating temperatures and better mechanical strength. Here, Simon Meijer and Alex Masolin, from Coolback – along with Fraunhofer ISE’s Andreas Beinert – answer some of the questions we didn’t have time for during the live broadcast.

From left, Simon Meijer, founder and CEO of Coolback; Andreas Beinert, researcher at Fraunhofer ISE; and Alex Masolin, R&D application specialist at Coolback.

The three speakers from our pv magazine webinar on 26 April have taken the time to answer more of the questions posed by the audience during the live broadcast. Click here to view the webinar and access presentations.

Have you also tested potential-induced degradation (PID) implications for the Coolback solution? How does this compare to glass-glass or glass-backsheet modules?

Simon Meijer: PID resistance is a combination of parameters set by the manufacturer of the solar module and their choice of materials.

Alex Masolin: PID occurs when there is a high voltage potential between the internal electrical circuit and the frame of the PV module. Humidity and temperature are known to accelerate PID and these can be influenced by the solar cell design, module glass selection, and system grounding strategies. Coolback provides the backsheet and aluminum profiles and thus has no influence on the selection of other materials needed to manufacture a solar module.

How do the energy yield gains achieved with Coolback compare to those with a bifacial module?

AM: Direct comparison between Coolback and bifacial technology is not possible, due to the major differences in the laminate. It can, however, be said that bifacial gains are heavily dependent on the rear irradiance (albedo, shading from mounting structure or wiring…) and optimization of such [a] set-up is not straightforward. Sometimes, such optimization is not even possible. For example, on floating installations, where albedo is extremely low, the benefit of using a bifacial module is hindered. On the other hand, Coolback is more resilient to possible inaccuracies of the plant design and, therefore, equipped to provide an enhanced energy gain in more situations, compared to bifacial.

Do you have any future plans for a bifacial solution? How does Coolback compare to bifacial modules in terms of finance?

AM: Coolback covers the back side of the module. This works to expand the surface area and to replace the frame. Bifacial modules are, in principle, able to use Coolback, but this will block the functioning of solar harvesting at the rear side of the cell. For this reason, we primarily focus on monofacial modules.

SM: The energy output of bifacial modules varies per location, but also over time. This makes a straightforward estimate difficult to calculate. Also, the cost of bifacial modules might be higher than Coolback modules. A detailed plan should be evaluated for a more accurate calculation.

Does the expected yield gain vary significantly between climate regions?

AM: Coolback is designed to tackle the high operating temperature of a PV module, which mainly occurs in hot climates. Indeed, the gains are reduced in cold climates or in very windy regions. Nevertheless, even in the worst case, a Coolback module will perform at least as well as a framed reference module with the same laminate. It also provides superior mechanical strength in any climate, reducing degradation and extending module lifetime.

Are there any challenges or downsides to modules using the Coolback solution? How are these managed?

SM: Since the modules are frameless, transport and mounting can cause vulnerability to the laminate. To reduce the risk of damage here, safety corners are applied during production and can be removed after installation.

How do Coolback modules compare to “traditional” glass-backsheet modules in terms of transportation and manual handling? Is palletizing more difficult?

AM: 30-40% more Coolback modules can fit on a pallet, compared to conventionally framed modules.

Thanks to the rear cooling fins of the Coolback module, the modules can be stacked back-to-back for transport. The position of the aluminum profiles and fins is designed to make the most efficient use of space when stacked. Stacking aids have been developed to allow for the safe transportation of the modules and allow 30-40% more modules on a pallet than conventional framed modules.

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Furthermore, the rigidity of Coolback modules prevents microcracks during handling, transport and installation in the field.

Roughly what is the added cost per Wp to integrate Coolback in a standard module?

SM: There is no added cost per Wp in using the Coolback system, which replaces the conventional backsheet/frame and mounting system at a competitive price. Additionally, the increased energy output and module lifetime results in a lower LCOE.

When will modules featuring Coolback be available on the market?

SM: Modules with Coolback are available from May 2021. We do not produce modules ourselves but instead deliver our patented technology to module manufacturers for integration with their own products. We also offer the option to license our technology, including the lease of a Coolback assembly station for high-speed production, which follows standard operating procedures.

Coolback is continually expanding its certification of different module brands. It is currently certified on modules from HaiTai and Sunerg.

Does Coolback have any implications in terms of electrical safety – it seems that having metal on the entire rear side would increase the risk of leakage in the case of a small defect in the insulating polymer? Could you comment on electrical safety when operated at 1500 V?

AM: Our solution is designed to exceed the strictest requirements, in terms of safety. The inner insulating component is over-engineered to ensure proper insulation with no risk of defect for the entire life of the module. The Coolback backsheet is IEC certified by TÜV for 1500-volt systems and validated for extended aging tests to ensure reliability and full system safety in every climate condition during the module’s entire lifetime.

How does the aluminum react to temperature changes throughout the day – is there expansion or contraction, and does this impact the cells?

AM: Aluminum deformation due to temperature changes are extremely limited and easily absorbed by the design configuration and by the inner plastic part, with no influence on the cells. Coolback modules have been extensively tested in the most severe environments with extreme temperature differences, and have shown no problems.

Andreas Beinert: Additionally, FEM simulations are used to investigate thermal expansion and contractions. By this digital prototyping, critical temperature changes can be identified in the computer, rather than the field, and the design can be optimized accordingly.

Has Coolback been tested in floating PV installations?

SM: Coolback is a perfect solution for floating PV installations, due to its waterproof moisture barrier and cooling performance. Testing installations are ongoing in some areas. A large project on the sea is currently in development. This installation will benefit enormously from the superior mechanical strength of the Coolback System to protect against severe sea weather conditions.

Is Coolback compatible with standard encapsulants & lamination processes?

AM: Yes, fully compatible with every standard encapsulating material and process. The backsheet can be used as a standard backsheet without requiring line modification, and with using the standard lamination recipe.

Coolback will also be participating in our Roundtables Europe 2021 event, to be held on June 9 and 10. Click here to register!

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Source: pv magazine