More Power from the Sun

Feature Article | June 28, 2011 by Frank Völkel

Organische Zelle vom Fraunhofer Institut

Flexible solar cell made from synthetic material by Fraunhofer ISE (photo: Frank Völkel)

Times have definitely changed. Just four years ago, the Intersolar Europe exhibition comprised only a few halls and its visitors were mainly amateurs and technology enthusiasts. This year, however, all the halls at the Munich Trade Fair Center in Riem were booked out and people from many different walks of life mingled. Somewhat fittingly, the situation looks much like the dotcom bubble in the IT industry at the end of the 1990s. More than 2,500 exhibitors and over 100,000 visitors flocked to the three-day event in Munich. And some of the attendees really did have the impression that the solar industry is bursting at the seams.

Germany is one of the world’s most important markets when it comes to photovoltaic modules. It has more solar cells installed on roofs and buildings than anywhere else on the planet. And the percentage of solar energy in the electricity mix is set to almost quadruple between now and 2020. If everything goes according to the plans of the German government, the country’s last nuclear power plant will be decommissioned in 2022. As a result, renewable energy sources must make an increasing contribution to the power supply.

Compared with other countries, Germany is quite advanced in terms of its commitment to solar power, as was reported in the press on March 21 this year: On this day in spring, solar energy overtook nuclear power for the first time in Germany. The Germany-wide solar systems produced 17 GW, while the nuclear power plants generated a mere 15 GW.

However, another picture is painted when we look at the energy produced annually by photovoltaic plants: The share of solar energy in the electricity mix is around 2.5%, although many new plants were constructed in the past two years.

Carport mit Solarzellen zum Laden des Smart ed (Foto: Frank Völkel)

Carport with solar cells to recharge the Smart ed (photo: Frank Völkel)

Rekord beim Wirkungsgrad: Sharp Solarpanel mit 22,7% (Foto: Frank Völkel)

World record: Sharp solar panel with 21.6% efficiency (photo: Frank Völkel)

Power and Demand When the Sun Shines

The reason for this is simple: The solar modules only feed power into the grid when sufficient sun shines on the cells. Conventional power stations, on the other hand, can permanently provide the same energy, in case it is needed by consumers via the grid.

On the whole in 2010, the nuclear power stations produced around 10 times more energy than the photovoltaic plants on the roofs and in the fields of Germany. The high intensity of the sun around lunch time means that the amount of electricity generated by photovoltaic cells is also particularly high at this time – because that’s when demand is the greatest, too.

Synthetic Film Generates Power

Up to now, solar modules have been stiff and mainly based on metallic silicon. But in around 10 years, synthetic film will be mature enough to hit the market and transform sunlight into electrical energy. The organic photovoltaic cells such as those demonstrated by the Fraunhofer Institute for Solar Energy Systems ISE at the Intersolar exhibition are based on polymers that can be produced comparatively cheaply and easily.

They are currently not very effective – less than 3% – which means that a much greater area is required to produce electricity than with conventional thin-film or crystalline modules. What’s more, work still needs to be done to establish how the synthetic material will react to the outdoor elements over a longer period.

Dünnschicht-Zellen als Fassade von Schüco (Foto: Frank Völkel)

Thin-film cells as a facade by Schüco (photo: Frank Völkel)

Integrating Solar Modules with Walls and Roofs

While most solar modules are still being installed on roofs and open spaces, there is a growing trend toward integrating them into buildings, roofs, and facades. After all, solar cells are not only functional and do not only produce energy, but they can also make a contribution to a building’s attractiveness. At the exhibition, thin-film modules were on display in a variety of colors other than black – including blue, green, and silver. And before too long, we may well see conventional building materials for roofs and facades being replaced with integrated thin-film modules.

Photovoltaik-Zellen zur Dachintegration

Photovoltaic cells for integration into roof constructions (photo: Frank Völkel)

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