Germany’s E.ON has announced plans to build two battery systems totaling nearly 20MW that will be charged by its massive Roscoe wind complex in central Texas, continuing its push into the growing US grid-scale storage market.

E.ON will build the Texas Waves storage projects alongside Virginia-based Greensmith, a provider of storage software and services, in which E.ON’s venture-capital arm took a stake in 2015.

The short-duration storage facilities, which will use Lithium-ion batteries, are due online by the end of 2017, and will provide ancillary services to Texas’ grid operator, ERCOT.