The customer has contracted Proton to supply fuel cell emergency power units for the region of Bavaria, in a deal worth £11.4m.
This new deal follows on from a previous order last month, and will see the AIM-listed company supply units with power ranges of between 6-8 kilovolt-amps (kVA).
The units will be contained in outdoor cabinets which include hydrogen storage, fuel cells, UPS (Uninterruptible Power Supply) and auxiliary components.
These units use different forms of clean hydrogen fuel cell technology and offer long backup time, even for customers with high power rating requirements.
Chief executive Faiz Nahab said: “This framework agreement is another milestone that will provide year on year revenue streams as commercialization of our core technology is now realized.
“Our continued investment in our manufacturing capability is now bearing fruits.
"This is the proof that the fuel cell technology is commercially attractive to customers resulting in projects which will provide years of revenues for Proton.
"This order demonstrates our expertise in providing complete solutions with a fuel cell as part of a UPS system with a very long backup time."