My experience? 99% of green tech, like almost all other startups, is either trying to reinvent the wheel, solely depending on VC, banking on legislative change that will never happen, green in name only, or just a straight up scam. And investing itself is part of the problem, because a lot of the business nowadays is just appearances to attract investors, cash out, move on. You can't invest in any company and hope they stay true to their word, because sooner or later some MBAsshole is going to maximize shareholder value the place either into the ground or into suck-the-planet-dry for profit country.
Where does that leave you? Use your money and invest in yourself, your home, your family, possibly build a doomsday bunker or a self sustaining farmstead.