New energy-scavenging systems being developed by Massachusetts Institute of Technology (MIT) researchers could provide power for sensors just from differences in temperature between the body (or other warm object) and the surrounding air, eliminating or reducing the need for a battery. The unique aspect of the new MIT-developed devices is their ability to harness differences of just one or two degrees, producing tiny (about 100 microwatts) but nevertheless usable amounts of electric power.
The researchers say, that as a result of research over the last decade, the power consumption of various electronic sensors, processors and communications devices has been greatly reduced, making it possible to power such devices from very low-power energy harvesting systems such as this wearable thermoelectric system.
Such a system, for example, could enable 24-hour-a-day monitoring of heart rate, blood sugar or other biomedical data, through a simple device worn on an arm or a leg and powered just by the body’s temperature (which, except on a 98.6°F summer day, would almost always be different from the surrounding air). Or it could be used to monitor the warm exhaust gases in the flues of a chemical plant, or air quality in the ducts of a heating and ventilation system.
The key to the new technology is a control circuit that optimizes the match between the energy output from the thermoelectric material (which generates power from temperature differences) and the storage system connected to it, in this case a storage capacitor.
The present experimental versions of the device require a metal heat-sink worn on an arm or leg, exposed to the ambient air. The researchers say that there’s work to be done on miniaturizing the whole system, and that this might be accomplished by combining and simplifying the electronics and by improving airflow over the heat sink.
