Renewable energy storage solutions
By Drs. Robert & Sonia Vogl
President and Vice President, Illinois Renewable Energy Association
One of the challenges facing the renewable energy industry is that electrical production from wind and solar installations is intermittent and does not always match the grid demand.
Some initial solutions to the mismatch between renewable energy production and consumption have taken the form of having highly dispersed wind and solar installations, grid expansion to distribute electricity to other markets, and having customers agree to shift some of their consumption away from times of high demand. Other approaches include improving battery storage techniques to lower their cost and reliability.
The new Tesla gigafactory targeted at producing batteries for electric cars could improve the economics of using batteries to store electricity from renewable energy sources.
In State of the Art Electricity Storage Systems, Auer and Keil discuss the various potential storage systems envisioned for Germany to accommodate increasing levels of electricity produced from solar and wind sources.
Germany expects short-term power storage needs of a few minutes to a few days to at least double by 2025. The authors believe the demand can be met by existing strategies along with adding pumped and compressed air storage and storage power stations.
By 2040, increased renewable production is expected to require systems that can store energy from several weeks to months at a time. A storage potential being explored is using several levels of abandoned coal mines to store water. The stored water would be allowed to flow from the higher mine levels to lower levels and generate electricity from the flow. When surplus electricity is available, the water is pumped back up to the higher level to be used again as needed. Major challenges include finding suitable sites along with an adequate supply of water. Such an approach would rely on existing technologies and skills, and would avoid the limits of suitable above ground sites.
Hydrogen and methane storage systems can be created to meet the demand. Existing technologies can convert electricity to gas for later consumption. Water can be electrolyzed to produce oxygen and hydrogen. A small amount of hydrogen can be injected into the natural gas grid or used in natural gas vehicles. A mixture of 15 percent hydrogen in natural gas has been used to create hythane, used as a vehicle fuel. Methane, which can be used in the natural gas grid, could be produced from hydrogen combined with carbon dioxide or from wood gas or a biogas plant.
Using renewable energy, a plant in Wertle, Germany, has produced methane from carbon dioxide waste from a biogas plant, which customers can then use in a compressed natural gas car produced by Audi.
Through power storage, grid expansions can be minimized or delayed. The storage systems could eventually break the existing challenge of providing electricity from renewable energy sources to meet electrical demand.
If gas storage becomes the system of choice, it can unite the electric grid with the natural gas grid.
The Germans are confident the storage problem can be solved using existing technology and skills. While the U.S. seems more focused on battery storage and electric vehicles, between the two approaches, solutions do exist. With the proper investment and political will, we can solve the problem as well.
Drs. Robert and Sonia Vogl are founders and officers of the Illinois Renewable Energy Association (IREA) and coordinate the annual Renewable Energy and Sustainable Lifestyle Fair. E-mail firstname.lastname@example.org.
From the Sept. 24-30, 2014, issue