Green for less: Ma Yanjun's beer bottle water heater

When considering green technology, one key question has to be utility. While bamboo flooring or $160 composting bins might be environmentally sound and socially responsible, they also don't fill a really common need. The best technologies are, arguably, the most plebian ones; after all, a green advance that fills an unnecessary need isn't really much of an advance at all.

One of the most basic needs is clean water. To that end, my buddy Nick, who used to be a Peace Corps worker in Cape Verde, helped develop a low-cost still that uses solar power to de-salinize water. The prototype cost about $200 to make, but future models should be much more cost-effective. Best of all, it was constructed of locally-available materials. Here's a little video about it. In addition to addressing the problem of fresh water, which is a major issue in Cape Verde, he created something that can be endlessly replicated (and improved) by the people who need it.