Look at the following photo that was shot at Nextreme Thermal Solutions Inc of the US. This is a demonstration in which the heat of a candle flame was converted into electric power to turn on an LED.

Most energy of a candle flame turns into heat, so, an LED lamp powered by the heat glows brighter than the candle flame itself, according to the company.

This technology is based on a well-known principle called "thermoelectric conversion". Many manufactures are paying close attention to it because it requires no microphone speaker or any other moving parts, making it easy to enhance durability and reduce size unlike the aforementioned thermoacoustic technology. The technology had once been developed in Japan's national project. And it seems that it will be commercialized in several fields in the near future.

These technologies are all an effort to efficiently convert waste heat, which has been a nuisance thus far, into electricity. Potential heat sources include boilers, hot water pipes, automotive emissions and engines, ICs, microprocessors, transmitters in high-speed telecommunication devices, the sun and human bodies.