Energy Scavenging (Harvesting) Methods

Alternative energy sources have become important for energy conservation, environmental preservation, increased energy demands, low-power electronics, and at scales both large and small. Our recent analysis of energy scavenging (harvesting) methods for driving long-term sensor deployment were used by the federal government to drive initiatives in micro-technology based thermoelectrics, photovoltaics (solar cells), vibration energy, and fuel cells.

Technology selection is driven almost exclusively by the end application and its operating environment, with each approach having advantages or disadvantages in cost, size, weight, and power density. Physics set an ultimate limit to total available energy (TAE) density, which for example in the case of thermoelectrics are limited by the Carnot efficiency, and hence, find the best utility in environments having large thermal gradients, e.g. combustion engines and computer CPU's. Our recommendation was that energy scavenging must incorporate system requirements, and in some case drive them, where focused efforts are placed on decreasing power requirements, especially in telemetry, improving electronics, and reducing quiescent power dissipation in low-duty cycle sensors. Off-the-self scavenging techniques are not widely available and materials improvements will be important to improve efficiency. The government will remain an important catalyst until costs are driven down and electronics find an effective way to integrate with these energy sources.

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