Masayuki Miyazaki, a senior researcher at Hitachi Co. Ltd.’s central lab in Tokyo, recently made a tiny generator that converts building movements into electricity, creating enough energy to run a temperature or light sensor once an hour.

Though the output is small right now, only about 10 microwatts, scientists predict the generator’s potential could be huge in coming decades — possibly used in battery-free computing systems.

Dr. Miyazaki’s work is part of a growing movement by scientists to find, create, or capture alternative sources of energy — even in small amounts much less than one watt. Researchers hope to harvest power from anything from the vibrations of walls and windows to the movements of air and the human body.

While alternative energy sources alone might not produce much electricity, they could help power small devices such as computer chips, wireless sensor networks, or cellphones.

The idea is simple…

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