There are probably in thousands of potential greentech companies that could achieve profitability on 10 - 100 million. Probably the best example here is solar, as many companies already have achieved profitability, but there are tons of opportunities in fuels, materials, building technology, vehicle technology, water supply, agriculture, construction, data centers, refrigeration, industrial processes, road construction, and so on. There might exist companies you'd need to pump a billion into, but why attempt it?