“Clean tech’s rising tide won’t necessarily lift all of its boats: individual technology niches, companies and investors will no doubt see some stormy times.”
The Cleantech Revolution 
One of the first rules of investing is, of course, that different investments suit different people or institutions at different stages of their lives. This applies to green investments as much as it does any other kind, so when starting to build a green portfolio you need to be clear about your investment aims and how long you are planning to invest for.
You might need to be prepared to see some loss in the value of your investments in the short term in exchange for medium to long-term gains. Brigid Benson of the Gaeia ...