Energy harvesting from atmospheric variations – Theory and test

• An experiment was designed to harvest energy from atmospheric variations.
• Bellows containing ethyl chloride transformed temperature change into displacement.
• Bench-top experiment was fabricated and tests conducted to validate the concept.
• 6 Joules (J) of energy were harvested for a 23 °C temperature change.
• A nonlinear mathematical model was validated through experimental data.

The last two decades have offered a dramatic rise in the use of digital technologies such as wireless sensor networks that require small isolated power supplies. Energy harvesting, a method to gather energy from ambient sources including sunlight, vibrations, heat, etc., has provided some success in powering these systems. One of the unexplored areas of energy harvesting is the use of atmospheric temperature variations to obtain usable energy. This paper investigates an innovative device to extract energy from atmospheric variations using ethyl chloride filled mechanical bellows. The apparatus consists of a bellows filled with ethyl chloride working against a spring in a closed and controlled environment. The bellows expand/contract depending upon the ambient temperature and the energy harvested is calculated as a function of the bellows' length. The experiments showed that 6 J of energy may be harvested for a 23 °C change in temperature. The numerical results closely correlated to the experimental data with a deviation of 1%. In regions with high diurnal temperature variation, such an apparatus may yield approximately 250 μW depending on the ambient temperature range.