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Leveraging bacterial spores to generate and store energy

For evaporation to become an economically feasible source of renewable energy, useful work needs to be generated with high efficiency, long term sustained performance, and preferably without consuming fresh water. Bacterial spores are dormant cells that can withstand harsh environmental conditions for long period of time and still maintain biological functionality. The spores are extremely dynamic structures that can respond to change in relative humidity (RH) in the environment by expanding and shrinking their diameter anisotropically by as much as 12%. By assembling a single layer of spores on a rubber sheet, researchers at Harvard demonstrated the transfer of more than one Joule to each square meter of rubber as the spores dried at low RH. The resulting forces were strong enough to generate electricity by bending a piezoelectric transducer. Furthermore, spores sustained their energy conversion performance even after a million cycles of high and low relative humidity. The demonstrated speed and efficiency of energy conversion may permit generating renewable energy from natural evaporation across open water with low cost rubber based devices at an area power density comparable to existing renewable energy technologies. Comparing to traditional tidal and wave based energy generation technologies, this invention do not require significant current flow and can be more broadly applied to anywhere standing water exists. This makes it ideal for remote, off-the-grid power generation for small energy consumption devices.

Intellectual Property Status: Patent(s) Pending

Applications

On wet surfaces and open water, evaporation provides an effective way to release the heat coming from solar radiation to the surrounding air. Under dry atmospheric conditions evaporation also allows for doing useful work. In nature, trees harness this phenomenon to transport water from soil to the leaves. These processes have inspired engineered systems that have demonstrated novel capabilities as actuators, pumps, and even as energy scavengers and biological sensors. However, the prospects of natural evaporation in providing utility scale renewable energy have not received attention thus far. The present invention used bacterial spores that show promise for efficient and sustainable energy conversion from evaporation with low cost and scalable device architectures. This technique provides a unique way to generate energy near water sources (run-off, sea water etc.), especially at remote, off-the-grid locations and storing generated energy in a convenient, low-maintenance form factor that can released at appropriate environment to do work. Additional applications include scavenging the heat released from human body to power micro-electronic devices and latent heat capture for use in next generation, energy efficient, sustainable buildings.

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