Materials scientist Aaswat Raman led a team of Stanford and UC students to develop a prototype "nighttime" power generator. It is based on the phenomenon of temperature difference at the onset of darkness, when objects heated by sunlight during the day begin to give off heat to the cold air. If a generator is placed on the border of two environments, it can turn this process into a renewable energy source.
The idea for such a generator came about while discussing ways to improve solar panels. Due to the daily rhythm in the conditions of our planet, they stand idle for half the time, while darkness reigns. However, sunlight also carries heat, which accumulates in illuminated objects during daylight hours, and then can be used at night. It remains to apply the well-known thermoelectric effect and design a suitable generator.
In the center of the unit there is a heat exchanger in the form of a black painted aluminum sheet. It is hidden in a polystyrene shell that only transmits infrared radiation. A conventional thermocouple is connected to the heat exchanger, and a signal LED is connected to it. When the metal heated during the day begins to release heat into the cold night air, the thermocouple generates electricity and activates the LED.
The prototype generates 25 milliwatts per square meter. The developers have calculated that with optimal calibration and under ideal conditions, they can achieve up to 500 milliwatts per square meter. A little, but not bad - after all, we are talking about a passive and renewable energy source. There are many places in the world where the use of classic solar panels is unprofitable, but there is enough sunlight. And there similar generators can be used for secondary purposes, such as illuminating buildings or recharging gadgets.