Energy on tap
By 2050, Germany wants to source 80 percent of its electricity from renewables, mainly from wind turbines and PV systems. When clouds suddenly appear or the wind drops without warning, the country needs an electricity system that can adapt quickly and flexibly to the situation. Energy storage systems provide a solution. When there is plenty of wind and sunshine, they can store electricity, which they then release as needed during times of low production, darkness or overcast weather.
There are many types of storage solutions. Short-term storage options, such as batteries, capacitors and flywheel systems, can take in and release electrical energy several times over the course of a day. However, their capacity is limited.
Germany mainly uses pumped storage plants to store electricity for a longer period of time. These plants, some of which are in Luxembourg and Austria, currently have a capacity of around nine gigawatts connected to the German grid. Although this gives Germany the largest pumped storage capacity in the EU, there is only limited scope for expansion. Germany is therefore working closely with countries that have large storage capacities. Austria, Switzerland and Norway are the most important countries.
Compressed air storage is another alternative for storing energy for a longer time. It uses surplus energy to compress air into underground space such as caverns in salt domes. When needed, the compressed air powers a generator, thus producing electricity.
Power to gas is a more promising concept for long-term storage. It uses electrolysis to convert electricity from renewable energies into hydrogen or synthetic natural gas. The advantage is that hydrogen and natural gas can be stored, used immediately or fed into the natural gas network. These gases are easy to transport and can be used flexibly. Power plants can convert them back into electricity and heat as needed, while consumers can use them to cook, heat, or power their car.
The German Government is therefore promoting research and development to bring down storage costs. Since 2011, it has been running a storage funding initiative. Since 2013, it has also been funding small, decentralised storage systems linked to PV systems. Rapidly balancing out minor imbalances in the power grid is a new way of using batteries. This means that electric vehicles that are not in use can help stabilise the electricity supply. The market launch of these battery systems will foster research and innovation and reduce costs.
Over the coming years, the demand for electricity storage will grow, especially in electric vehicles. Low cost systems for all storage technologies across the grid will only be possible in the long term, when renewable energies make up a very large part of the electricity mix. In the short to medium term, other options are less expensive. These include grid expansion or managing generation and consumption for efficient energy use.