|Researchers at MIT and Stanford found a new way to transform waste heat into electricity, particularly in situations where the temperature gradient is small, below 100oC (180° F). The technology uses widely available materials, and could be used to recycle large amounts of wasted heat generated in industrial processes and electric power plants. The research study was published in the journal Nature Communications. Researchers at MIT and Stanford led by Prof. Gang Chen devised an alternative approach that takes advantage of the thermogalvanic effect, which describes a peculiar relationship between the temperature of a battery and the voltage at which it can effectively be charged up.
The scientists built a system that allows waste heat to first raise the temperature of a battery. Because of the thermogalvanic effect, the battery can be charged at a lower voltage than would normally be required. The battery is then allowed to cool down, and at this point its lower temperature allows it to be discharged at a higher voltage, releasing more energy than was put into it through the electric grid. The difference in energy was gathered from waste heat. Compared to the original system, Chen et al., achieved the capability to harness much smaller differences in temperature with relatively high efficiency (a difference of 50° C (90° F), with 5.7 percent efficiency)