Storing excess renewable power
Germany already faces situations in which more renewable power is generated that can be consumed. The country is focusing on storing this excess electricity as gas.
Germany plans to largely replace the nuclear plants it is phasing out with gas turbines – a move that has brought about a lot of criticism because gas turbines have greater carbon emissions than nuclear plants. The result is ironic: countries that have not fulfilled their Kyoto targets for lower carbon emissions are now criticizing Germany, one of the few countries that has already overshot its Kyoto target and therefore theoretically has some carbon emissions on credit.
More importantly, these critics fail to realize that flexible gas turbines are exactly what a grid with a large amount of intermittent solar and wind needs. No wonder the country is looking so heavily into producing gas with "excess" renewable power.
This week, Germany's Network Agency and Fraunhofer IWS held a workshop in Berlin on renewable power to gas. In cooperation with the Center for Solar Energy and Hydrogen Research of Baden-Württemberg (ZSW), a concept was worked up: "Our simulations show that a 100% supply of renewable power would require up to two weeks at a time to be bridged during the winter. The only option for such long-term fluctuations is fluids and gases, such as hydrogen and methane," explains Jürgen Schmid, director of Fraunhofer IWES. While this gas would be quite expensive – probably twice as much as the electricity used to produce it – Germany's natural gas network could easily store several weeks of "renewable gas," thereby offsetting consumption of natural gas in the process. This approach would also provide at least some renewable fuel for vehicles, thereby killing two birds with one stone.
The private sector is also interested. Power giant Eon is currently investing five million euros in a pilot plant for the conversion of wind power into hydrogen in Brandenburg. By 2013, the system is to start making around 360 m³ of hydrogen from green power by means of electrolysis. The hydrogen will be sold to the local gas network and mixed in with normal natural gas, according to the firm.
Eon points out that 5% hydrogen can already be mixed in with natural gas, but the target for the midterm is up to 15%. While the company believes that it will still be a few decades before renewables provide more than half of the country's power supply, thereby requiring a great amount of storage, even before then the grid will reach its limits as the supply of power increasingly exceeds demand – which is why the firm says it is investing in power storage now.
Christian Drepper, Eon's corporate spokesperson, says, "Natural gas is the perfect way to store energy because it is flexible and can be used in a wide range of applications. Furthermore, its efficiency does not drop the longer it is stored." Eon already has a biogas division, which refines biogas to the quality of natural gas at five locations within Germany. (Regine Krüger / Craig Morris)
