Nitinol Based heat Engine for Solar Energy Harvesting

The most abundantly available renewable energy source on the earth is solar energy. Conventionally, this energy is converted into electric energy with the help of photovoltaic cells. The efficiency of this commercially available technology is around 5-25%. This article deals with the investigation of an innovative energy harvesting system that uses a Shape Memory Alloy (SMA) to utilize solar heat for generating electric power. SMA shows significant deflection when heated and this characteristic is used to develop a SMA based heat engine. This work proposes a heat engine where a SMA wire is used to convert solar radiation to perform mechanical work. Further, the mechanical work is used to drive a rotary electric generator to produce electric energy. The SMA used for this purpose is Nitinol wire, which absorbs heat from the solar radiation and transforms the same initially to mechanical motion, which later is used to produce electric power. Initially, the SMA element is curved in shape, and it shows a significant deflection when it receives the heat from solar radiation. This deflection of the SMA element is used to operate a rotary electric generator to produce electric energy. The theoretical calculations for balance of the energy flow from incident solar radiations to output electric energy is discussed. The developed prototype shows around 4.5% efficiency with an average power of 2.4 mW.