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Wiktionary
micropower

a. Of or pertaining to generating, storing or using extremely small amounts of power.

Wikipedia
Micropower

Micropower describes the work that researchers at several universities are doing to develop very small electric generators and prime movers or devices to convert heat or motion to electricity, for use close to the generator. These devices offer the promise of a power source for portable electronic devices which is lighter weight and has a longer operating time than batteries. Micropower differs from microgeneration in being concerned with universities, mobility and milliwatts or watts rather than individuals, homes and kilowatts.