On April 9th, Nikkei newspaper reported the technology of converting heat to sound to electricity. Researchers are trying to commercialize thermal acoustic phenomenon, which uses a heat temperature difference to induce sound, which can be converted to electricity with high efficiency.
Although this technology has not a short history, it holds enormous potentialities to produce several energy saving systems. The Associate Professor, Biwa, at Tohoku University experiments the conversion from heat to air vibration energy with multi-stage type thermal acoustic apparatus. Once he heats one side of a pipe consisting of a series of small parallel channels, referred to as a ‘stack’, “Bo” sounds come from the other side. According to the Associate Professor Biwa, heat engine reciprocates the solid piston. In thermal acoustic phenomena, heat makes shaking fluid itself “air”. As this type of engine has few moving parts, in principle, it is possible to achieve efficient energy conversion. The Biwa’s group is researching the system that generates sound wave with several heated portions. It will enable to generate energy from low temperature heat efficiently. So far the research group has succeeded in moving system with low-temperature difference of under 60 degree Celsius (140 degree Fahrenheit).
Some researchers are trying to apply to larger system such as a liquefied natural gas plant. “The thermoacoustic natural gas liquefier converts heat into sound waves and then converts the hot sound wave energy to cold refrigeration using highly pressurized helium contained in a network of welded steel pipes. First, the system combusts a small fraction of the natural gas to heat one end of the steel pipe network. Then, the resulting acoustic energy refrigerates the opposite end of the network, which cools the rest of the natural gas.” “Capturing natural gas requires costly ultra cold natural-gas liquefier the size of oil refineries. But our thermoacoustic liquefier should be economical at a smaller size, useful for remote corners of the world where smaller gas fields are available. I’m especially eager to capture the associated gas that often comes out of the ground as a byproduct of oil production” said the Denver-based company Swift LNG.
As many plant workers in developing countries are required to work in hot condition, I feel that this technology may help to improve working condition with clean energy such as solar or waste heat. I also think that it will increase the production of natural gas through developing growing number of small-mid size natural gas projects. This is critical for island countries such as Indonesia or Japan that relies on imported natural gas, LNG.