2 Micro-Hydroelectric Power
Hilly land streaked with small streams makes anideal spot for micro-hydroelectric power generators, each of which requires a meager water flow of just three gallons per second to turn. (To put this in perspective, the Mississippi's average flow at New Orleans is about 4.4 million gallons per second.) The Appropriate Infrastructure Development Group (AIDG) has helped to build three systems in Guatemala, and more communities are now saving up money for local installations.
At the end of Back to the Future, a little bit of garbage is all Doc Brown needs to fuel his DeLorean time machine. Biodigesters won’t quite generate "1.21 jigawatts" of power (as Doc's Mr. Fusion device seemed to), but they can create fuel for heating, cooking, and electricity while reducing waste and water contamination. In the salchicha-type biodigester (salchicha means "sausage" in Spanish), bacteria break down waste in a 15-to-30-foot-long polyethylene tube and release methane, which is captured and piped to a stove. The digested waste can then be used as a fertilizer. Biodigesters have been around since the 1870s, but current efforts focus on producing them on a larger scale. An award-winning system installed in Rwandan prisons reduced the need for firewood by half.
4 WindPower on $2 a Day
Who said wind turbines have to spin? Shawn Frayne, founder of Humdinger Wind Energy, developed a turbine-less generator that harnesses energy from the rapid wind-induced vibration (50 cycles per second) of a seven-to-ten-foot flap of taffeta fabric.This is the same phenomenon—aeroelastic flutter—that civil engineers try to eliminate so bridges don’t sway in the wind, and on a small scale, it greatly increases the efficiency of capturing power from wind for a very small cost, says Frayne. "For people making a dollar or two a day, it could be in the realm of possibility to have electricity," says Peter Haas of AIDG, who is helping Frayne test the generators in Guatemala. Depending on wind conditions, the generators can be positioned to power efficient lights in a few rooms on small electrical grids. Frayne hopes to make the product available within a few years.
5 Sunlight Stored in LEDs
In rural Indian homes, kerosene lamps are ubiquitous, posing health concerns from fumes as well as a fire risk. Solar-charged lights designed by Patrick Walsh, founder of Greenlight Planet, are one solution to this problem. The lights run for four hours on their brightest setting after charging in the sun all day. The lights also reduce fuel costs for families and pay for themselves in just one year. After testing the market with 20 lamps, Walsh is now scaling up production.
6 Solar Water Heater
Solar water heaters are generally expensive (they can cost $400–$1,000), barring easy access to hot water for many who are far from an electric grid. But engineer Ashok Gadgil at the University of California, Berkeley, working with AIDG, cut back on materials and came up with a solar heater that costs $100. It can produce 26 gallons of water warmed to 104 degrees Fahrenheit by 4 p.m. each day—enough for four showers. Tests are ongoing in Guatemala, after which the team plans to fine-tune the design and begin distribution.
7 Pedal-Powered Grid
People who live off the grid in rural corners of the world may soon have a new source of energy: 12-volt batteries charged by pedaling. Using a simple alternator, six hours of pedaling can create and store enough electrical energy in batteries to light about six homes for 30 days (in areas where people use less electricity than in the U.S.). Dissigno, the San Francisco–based company that distributes the devices, has one prototype up and running in Haiti and next hopes to install a "grid" in Tanzania connected by a network of pedalers instead of power lines.