Performance of miniaturised devices turning heat into electricity

What is it about?

Silicon technologies, the same technologies that have supported the frantic development of microelectronic digital devices, such as memories and microprocessors, and also a bunch of advanced microsensors, are used to build miniaturised thermal harvesters. Moreover, these devices feature silicon nanowires as the key to convert heat into electricity. This is something that other materials can do fair enough but that requires some tricks (like moving into the nanosize domain) for silicon. The reward is to acomplish an all-silicon device so that it can be fabricated easily and cheaply in large volumes as it is the case of the devices mentioned before. The amount of electricity depends on the temperature difference that can be established across the nanowires. Since they are quite small, the power extracted is low, but this paper show that if the aire around of the device is moving, performance increases, because the moving air helps to make the cold part colder. In conditions of still air, you need to build on the device an additional structure with large contact area with the surrounding air. At this stage, the gain of such approach has been simulated.

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Why is it important?

Scavenging low-grade energy available environmentally, such as waste heat, and to produce electricity from it is a way of powering small sensors for the Internet of Things where hot surfaces are available, such as in industrial scenarios. They can subsitute batteries and their periodic need of replacement, which has associated economic, logistics and environmental costs.

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