With the economic downturn that hit in full force last fall, many cleantech VCs' minds made a pretty big shift away from capital-intensive solar, EV and biofuels investments, and (to the extent that checks were still being written) toward relatively more capital-efficient smart grid and energy efficiency bets. 

Regular readers of this column will know that I've been beating the drum for these kinds of investments for a while, for market and investment model reasons.  But it's sure true that they look that much more attractive in an environment where exits are a long way off and LPs aren't putting capital into new funds -- capital-efficiency looks better when capital is scarce, naturally.

However, as a (hopefully not temporary) sense of stability starts to return to the marketplace (and even accounting for the more bad news undoubtedly yet to come), many investors are starting to dream big again.  In the spring, a VC's fancy lightly turns to thoughts of radically reinventing the electricity industry, as it were.

Two strong potential candidates for the Next Big Th