Webinar: Innovations in solar energy technologies

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However, there is still much more to be gained by further technology development on the following aspects:

• Higher power density and energy yield (more energy per m2) at lower cost
• Improved spatial and environmental integration: attractive, barely visible, eco-positive photovoltaics
• Sustainability: end-of-life strategies, application of earth abandon materials

Program

• Arthur Weeber, Program Manager PV Technologies at TNO, will give a brief overview on commercially available solar modules which can be seen as introduction to the program.
• Agnes Mewe, Program Manager Silicon solar cells at TNO, will discuss improvements in performance and customization possible with crystalline silicon solar cells and modules.
• Sjoerd Veenstra, Program Manager Perovskite solar cells at TNO, will elaborate about the unique properties and application options for solar energy foils.
• Gianluca Coletti, Program Manager PV Tandem technology at TNO, will explain the principle of stacked solar cells to surpass the current limits in conversion efficiency, and their scalability for industrial deployment.

Do you envision it?

Watch the webinar and discover more about innovations in PV technologies.

1. When will thin film be available for large scale usage on existing facades of existing houses at affordable prices?

Thin-film PV is already commercially available at larger volumes. The steep decline in prices for PV modules also holds for thin-film PV. Actually, the prices for the different PV modules (in Euro per Wp output power) are similar and therefore already competitive with other electricity sources. Moreover, the prices are still decreasing. However, most of the thin-film modules are so-called flat-plate modules with a glass front sheet, they can be used for building applied PV panels, and are not fully integrated in building elements. Our focus is on flexible thin-film PV and we are developing the so-called PV mass customization program to make integrated PV at affordable prices. Many projects have shown the potential of integrated PV, but these products are not manufactured with industrial scalable processes. With mass customization we aim to connect integrated PV with high-volume industrial manufacturing. This will allow building elements with PV fully integrated to generate electricity at low cost; this way we can combine functionalities. A separate supporting structure, such as a frame, will not be needed for these elements in which PV is fully integrated. In principle mass customization is independent of the PV technology behind it. It can be applied to thin-film, crystalline silicon and future PV technologies. However, because of its flexibility, thin-film can have advantages for specific applications.

2. When can we expect perovskite PV modules on the market?

We expect perovskite PV modules to be available at a large scale well before 2030, and possibly on a small scale within two years. This PV technology can significantly contribute to the energy transition and to reach the ambitions of 2030, 2040 and 2050 because of its potentially low cost, high conversion efficiency, and environmental profile. However, a lot of R&D is still needed to proof the industrial feasibility of perovskite PV technology.

3. Does doping the Si wafers with impurities affect the efficiency of solar cells? If so, by what percentage?

The silicon wafers used for solar cells are doped. One side / pole is doped with boron or gallium and the other with phosphorus. Without these doped layers the solar cell will not work. However, transition of metal impurities, but also oxygen and carbon, can indeed lower the performance of the solar cell. This depends on the type of impurity, its concentration and the cell concept. Even in the parts per billion range, metal impurities can significantly reduce the output of a solar cell.

4. Do you need more electronics for the module with small cells and if so, does it increase the module price?

If you want to improve the shade tolerance of a module, you can do this by combining small cells (e.g. quarter cells) with additional electronic components, such as by-pass diodes or optimisers, and this would indeed increase the cost. However, if you don't pursue fancy electronic designs the cost will only increase marginally.

5. Would Pulsed laser deposition be effective for large area deposition, homogeneity and throughput?

Indeed, pulsed laser deposition (PLD) can be an effective way to deposit functional layers in a well-controlled way and on a large area. A PLD system designed and built by Solmates has recently been installed at the TNO facilities and large area deposition is being developed for crystalline silicon PV. The system can be used for other PV technologies as well.

6. Smaller cells enable you to reduce the shading problem. What does this imply for the inverter regarding power optimization?

The impact on the power electronics depends on the way the cells are interconnected . In addition, the PV technology largely determines the reverse bias behaviour, i.e. how the cell responds to shading. A high reverse bias characteristic means you can series interconnect many cells before breakdown occurs. However, the disadvantage is that the power dissipation is higher if breakdown occurs. The solution needs to be found in the right combination of PV tech, module design and power electronics.

7. If the perovskite layer itself is cheap enough, what would happen when you make a bifacial module with a second perovskite on the bottom?

This is indeed a good proposition for vertical module installations where high bifaciality is required. Of course it has to be cost effective. On the other hand, perovskite solar cells can already be made bifacial, meaning a single cell that can collect light from both sides and convert it to electricity. Depending on details of processing and cell design, the efficiency when illuminated from the rear side can be comparable to the efficiency of front side illumination (the latter is of course the standard).

8. In the webinar the efficiencies for tandem PV cells up to 100 cm2 are showed; what is the expected efficiency for a scaled-up tandem PV module?

This larger area platform addresses the main performance upscaling challenges. When going to larger, it is not so much performance but process control and layer homogeneity that play major roles in addition to the engineering of tools.

9. Are tandem devices more difficult to recycle? What is done to also make tandem devices sustainable?

Not necessarily; it depends on the configuration and the design. Nevertheless, considerations on the sustainability across the entire value chain and beyond recycling are very important. In particular initiatives on sustainability for conventional modules can be applied to tandem and the use of abundant and non-toxic materials is currently under investigation. Extended LCA studies are part of the study.