Fueling up with wind and sun

The energy transition will happen – states Professor Eicke Weber of the Fraunhofer Institute for Solar Energy Systems ISE.

However, right now the German energy transition is having trouble getting going. There are many discussions about rising electricity prices, new high-voltage transmission lines, and concerns about grid stability. But there are some good news too. For example, new technologies can help better match the power supply from renewable sources with power demand – without requiring new transmission lines.

We all know that the weather will be like this: You plan a barbecue with friends and family, and will it rain? Oh, yes. You take a day off to go sailing and end up drifting lazily in the deadest of all possible calms. It spoils the fun. When sun and wind are needed to generate power, though, the weather can spoil much more.

In Germany, the energy transition is currently facing some serious acceptance issues because of exactly this situation: the wind blows stronger in the northern parts of the country, but not always, and the south enjoys more intensive sunshine – but just during the day, of course. As a consequence, there are supply peaks, and these do not always match the demand peaks, either in terms of time or location. The transmission system operators (TSOs) must provide costly reserve capacity for power generation when supply from renewable sources is too low, and wind turbines and photovoltaic plants must be disconnected when there is oversupply to prevent overload – cutting into earnings for the plant operators. Plus, consumers often are far away from the location of renewable power generation, necessitating the construction of expensive new transmission lines – and many people do not welcome such projects, especially not in their own backyard.

Power storage is a key pillar of the energy transition

Some of these issues could be readily resolved if power storage capacities were large and, especially, cost-efficient enough. But there is a certain gap between the existing 7 GW storage capacity available as pumped power or compressed air storage plants and the estimated 14 GW storage capacity needed in Germany by 2020. Professor Weber considers extending storage capacity to be the fourth pillar of the energy transition – in addition to enhancing energy efficiency, increasing power generation capacities from renewable sources, and power grid expansion. The Association of German Engineers (VDI) shares this view and is organizing a special symposium in June on the role of energy storage for the energy transition.

Power to gas: wind and solar energy becomes fuel

In addition to technologies such as compressed air storage, batteries, and pumped power storage, an alterative technology has emerged: storing surplus power as hydrogen or methane. Power-to-gas plants have competitive efficiency, and projects in this area are being promoted also by engineering and even automotive companies. What makes power to gas such an interesting technology is that the products – hydrogen and methane – can be distributed and stored as “hitchhikers” in the natural power infrastructure, with no extra power lines needed.