How much energy storage will we need in order to ensure grid stability as more and more electricity is generated from renewable sources? Estimates for Germany covering the next four to six years vary from as little as 3 gigawatts (GW) to as much as 30 GW. A study conducted by Fraunhofer, Europe’s largest application-oriented research organization, predicts that the country will need 13 to 50 GW of energy storage by 2030. These figures vary so greatly because of the complex and differing assumptions that underlie such studies.
The Future of Energy
Developing a Mix of Energy Storage Solutions
Storage technologies are vital if both the transition to a new energy mix and global decarbonization are to succeed. As more and more electricity from fluctuating renewable sources flows through power lines, grids will have to become increasingly flexible to prevent blackouts. Researchers from Siemens Corporate Technology are developing solutions.
Huge Advance in Battery-Based Systems
“Storage technologies are a key, not only to the transition to a new energy mix in Germany, but also for decarbonization at a global level,” says Karl-Josef Kuhn, head of the Storage Solutions innovation project at Siemens Corporate Technology. Energy storage solutions range from conventional pumped-storage plants to advanced battery-based systems. The former are used to store large volumes of water, which can be used to generate electricity. Germany currently has nine pumped-storage facilities capable of collectively generating about seven gigawatts.
But that falls well short of what will be required in the future. “Pumped-storage power plants have limited potential for expansion, which means we have to find alternative storage technologies that will accommodate large volumes of electricity,” explains Kuhn. Battery solutions, such as Siemens’ modular, lithium-ion-based SIESTORAGE system, have made huge advances. Siemens’ system combines high-performance batteries with the power electronics needed for connection to the grid. The system can accommodate, and subsequently release, an output of up to 500 kilowatt hours with a capacity of one megawatt. Other traditional short-term storage solutions include capacitors, flywheel storage systems and compressed-air storage.
Toward Long-Term Solutions
The drawback with all of the above is that they offer storage periods measured only in minutes or hours. With this in mind, Siemens researchers are therefore focusing on solutions that will convert electricity into forms of energy that lend themselves to long-term storage, such as hydrogen, as well as chemicals such as ammonia and methanol.
These power-to-gas technologies convert water and electricity to chemical raw materials using electrolysis. An initial pilot project, for instance, is Siemens’ hydrogen generation Mainz Energy Farm which, at up to six megawatts, is the largest plant of its kind anywhere in the world. The facility has the capacity to produce enough hydrogen for around 2,000 fuel-cell cars.
In addition to electrolysis-based hydrogen, Siemens is looking at methane. Both hydrogen and methane can be stored in the natural gas network and be used for reconversion into electricity. Siemens experts are also working on conversion processes using CO2-free fuels such as methanol.
Other subjects of research are thermal and mechanical storage, as well as systems that store electrical energy in the form of compressed air. “The key factor in making the transition to a new energy mix succeed,” says Kuhn, “is that we will need a combination of storage technologies