At Siemens Gamesa’s (SGRE) La Plana R&D site near Zaragoza, Spain, a redox flow energy storage system has been commissioned. The system is connected to the hybrid controller of the combined wind and PV generation system and supplements the lithium-ion batteries that have been in use here for around two years.The La Plana test-site integrates the next-generation Vanadium redox energy storage system with a wind turbine, solar-PV modules and a diesel generator. The new redox flow battery offers a 120kW energy output with a storage capacity of 400kWh. A hybrid controller coordinates the generation of all energy sources to meet the electrical load and is targeting to achieve the maximum integration of renewable energy.