I am wondering if it may be a foreign global technology company instead of US based? I have seen sometimes with newswires, headlines do not always match with article content or not actually written by the company. Focusing on the "synergistic" comment from Eric. Also foreign companies more likely to buy small stakes. Any "major" US tech company could easily takeover ZBB outright.
If foreign, my first "major" global company guess was Siemens with their ultracaps, wind rotors, HVDC lines, EV chargers, smart meters, and building efficiency services. Did not find any news of them with existing grid-scale battery development. Also ABB maybe.
If US, it could even be GE since recent news of their sodium battery development scarce. Maybe early stage investing in a back-up plan if can't get sodium battery into cost effective production. Though more "major" wind player than global technology, how about Northern Power with their mid-scale turbines and micro-grids. They have link with new board member.
Not to shoot down other guesses but to add to discussion. Google does have history of green investments, but they usually announce them and don't see much synergy. HP and IBM maybe? with their containerized data centers running on micro-grids, but out of their core areas.