Cheap electricity from photovoltaics

Alongside wind energy, photovoltaics are the central cornerstone of the ongoing change in energy policy. Nowadays, no electricity can be generated more cheaply than from solar power. That is mainly thanks to the rapid technological development seen over the past decades. Which has caused costs to tumble by more than 90 per cent and the efficiency of solar modules to improve massively. 

Thanks to the fast pace of development in photovoltaics, power stations can now be built that supply electricity from solar power for less than two cents per kilowatt-hour in sunny locations. And there is a good prospect of those costs decreasing even further. After all, the full potential of this technology is far from being exhausted. To that end, research continues in laboratories all over the world with a particular focus on solar-cell design and the semiconductor materials used in them. One of the leading institutions in this field is the Fraunhofer Institute for Solar Energy Systems (ISE). It holds numerous world efficiency records for an array of photovoltaic technologies. Examples include both-sides-contacted silicon solar cells (26 per cent) or siliconbased tandem cells (35.9 per cent).

Hunting for higher efficiency with photovoltaics

Solar cells made of crystalline silicon dominate the global photovoltaics market with a market share of over 90 per cent. Previous record efficiency levels of around 26 per cent were achieved with IBC (interdigitated back contact) solar cells. In other words, cells with both metal contacts on the rear. However, both-sides-contacted solar cells have become established as the industry standard. Those low complexity makes them the option of choice in industrial production processes. Professor Stefan Glunz, Head of Division Photovoltaics – Research at the Fraunhofer ISE, and his team of solar-cell researchers achieved similarly high levels of efficiency as IBC cells by employing a new approach for both-sides-contacted cells. “Both-sides-contacted solar cells have the potential to achieve efficiency levels of up to 27 per cent, which also makes them candidates for beating the previous world record for silicon solar cells,” Professor Glunz explains.

Energy from multiple layers

Efficiency can be massively increased if various semiconductor materials are superimposed in layers. With these tandem solar cells, the varying absorption of the individual materials enables the solar spectrum to be used for energy generation with even higher efficiency. “Silicon-based III-V semiconductor materials are just one avenue of exploration involving the use of tandem structures – the combination of multiple high-performance materials – to achieve even higher levels of efficiency in solar cells,” says Professor Andreas Bett, Director of the ISE. “Nonetheless, it will take a few more years until modules from this solar cell are available on the market, but this is an important, forward-looking trajectory in terms of refining photovoltaics to provide a sustainable energy supply.”

Simplicity and efficiency go hand in hand

Perovskites are another group of materials that the photovoltaics industry is pinning its hopes on. At present, this semiconductor material achieves similar levels of efficiency to silicon solar cells. Up to 25.2 per cent in laboratory tests. However, what makes perovskites particularly interesting is the way they are manufactured. Unlike silicon-based elements, which are heavy and require high temperatures during production, perovskite components are light and require far less energy in production. Moreover, they are based on cheap and plentiful raw materials.

Furthermore, perovskite solar modules can be either rigid or flexible, opaque or semi-transparent. This opens up a wide range of potential applications. Among these are perovskite modules, such as the ones integrated into windows, roof tiles, building façades, roads, or car roofs. In addition, semi-transparent perovskite cells can be combined with conventional solar cells to form a tandem solar module that boosts overall efficiency to record levels. Solliance Solar Research has already achieved an efficiency of 28.7 per cent using such cells. Solliance Solar Research is a consortium of partner research institutes and universities from the Netherlands, Belgium, and Germany.

Reducing system costs 

Yet the semiconductor material used for a solar cell is not the only decisive factor in the efficiency of photovoltaic systems. Power electronics can also make a crucial difference in boosting overall efficiency levels. Wide-band-gap power electronics will play a particularly important part here. After all, gallium nitride (GaN) and silicon carbide (SiC) semiconductor materials produce smaller, faster, more reliable energy systems. Than conventional silicon-based semiconductor devices, and also work more effectively. In fact, these semiconductors can eliminate about 90 per cent of the energy losses during power conversion.

Photovoltaic inverters featuring SiC power electronics suffer much lower switching losses and improve system efficiency. “Silicon carbide enables us to build high-performance inverters that are also compact and reliable,” explains Sven Bremicker, Head of Technology Development Center at SMA, a leading specialist for photovoltaic systems technology. “Thanks to their compact design, the inverters are much easier to transport and much quicker to install.”

The European photovoltaics industry is booming

Germany and Europe continue to be at the forefront of research and development for solar cells and modules. The production has increasingly shifted to Asia over the past ten years. Yet this trend is starting to reverse. Parameters are assessed slightly differently today than they were a few years ago. Such parameters be the share of transportation costs for imported modules and sustainable production criteria. In the face of current production costs of less than 0.20 Euro per watt peak, the share of transportation costs for modules and subcomponents alike is increasing and now totals around 10 per cent. As such, regional production close to target markets in Europe is once again possible while remaining economical.


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