No financial details were disclosed.
"Bringing together the disruptive thinking and innovations from cleantech start-ups and the global network and large-scale industrialization capabilities of Siemens Energy will create new value for our customers," Siemens Energy board member Vinod Philip said.
EIT InnoEnergy has already invested 690 million euros ($688 million) and holds stakes in Swedish battery cell maker Northvolt, steel venture H2 Green Steel, and lithium miner Vulcan Energy Resources.
Supported by the EU's European Institute of Innovation and Technology (EIT), EIT InnoEnergy helps to funds start-ups and companies active in the area of energy transition away from fossil fuels.
($1 = 1.0031 euros)
(Reporting by Christoph Steitz, Editing by Louise Heavens)