Energy has been able to generate energy from temperature differences for years. They use the thermoelectric effect, which occurs due to a temperature difference at the transition between two layers of material. When the heat from the hot side travels to the cold side of the material, there is a voltage difference and electric current is generated.
The thermal resonator (Picture: MIT)
Alternative energy generated from temperature fluctuations
For this effect, however, the difference in temperature between the layers must be considerable. MIT has now come up with a new technique that uses modest, daily temperature fluctuations to generate energy. Their design - the thermal resonator - can always be used through the use of these fluctuations. Waiting until it is blowing or the sun is shining to generate energy is no longer necessary with this technique.
Foam and wax
Conductive foam
In the resonator, the pyroelectric effect is used to obtain energy. This effect takes place in certain materials that are naturally electrically polarized. Heating of the material results in a different arrangement of the atoms, as a result of which the polarization changes. This change in polarization creates electrical tension. In contrast to the older technique, small temperature changes can already provide tension here.
The active component in the design is coated foam, made of copper or nickel. The foam is soaked with a special wax, consisting of octadecane. This substance is liquid or solid at different temperatures. This material mix is coated with the thermal conductor graphene.
Graphene (Credit: Leiden University)
The combination of these three materials ensures perfect thermal effusiveness: it can absorb and release heat very quickly. According to the scientists, this is the best 'thermal effusivity material' to date.
Balance
In the material of the resonator, heat therefore runs quickly from one side to the other. One side is always slightly cooler than the other, so the heat keeps going back and forth 'in the hope' of achieving a balance. Energy can be stored from this 'movement'.
The material has been tested for sixteen days. The scientists managed to generate 350 millivolt potential energy and 1.3 milliwatts of power. This is more than what a natural pyroelectric material of the same size can produce.
Modest
The generated energy with this technique remains modest, but according to the researchers, it is very promising. The small temperature fluctuations that are required to generate energy with this resonator take place everywhere and every day. Wind and solar energy is difficult to generate when it is not blowing or the sun is not shining.
Possibly the new technology will be used in the future to 'recycle' energy. The heat that is released by a refrigerator motor, for example, is constantly changing. The engine namely starts to cool the contents and goes off again when the refrigerator is at temperature. These small fluctuations can be used with the resonator of the MIT to generate energy.
'Recycle' energy. The heat that could be released by a refrigerator motor
By: Nature Communications, MIT News, New Atlas
Photo: MIT
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