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Microbial Fuel Cells, which work in a similar way to a battery, use bacteria to convert organic compounds directly into electricity by a process known as bio-catalytic oxidation.

Piezoelectric energy harvesters are typically vibrating cantilevers, covered with a piezoelectric layer that converts mechanical strain to an electrical charge to power devices. Most developers cover the entire length of the cantilever with piezoelectric material in an attempt to maximise the conversion efficiency.

ScienceDaily (Sep. 6, 2010) - Plants are good at doing what scientists and engineers have been struggling to do for decades: converting sunlight into stored energy, and doing so reliably day after day, year after year. Now some MIT scientists have succeeded in mimicking a key aspect of that process.

Researchers at LaserMotive have devised a way to beam lasers to power military bases and drones, possibly helping to save lives, since delivering fuel to battle zones can be a dangerous task in wartime. Although still largely in the R&D stage, laser power beaming has many other potential uses, which include powering vehicles, replacing electric power wiring and transmission lines in difficult places, and even launching rockets into orbit. The beam is about 8 inches wide as it leaves the transmitter - and then spreads wider as it travels. The beam emitter is located at a ground-based unit and operated by a person, who could control it from the same location or remotely from an entirely different place altogether. The operator uses the machine to fire the laser beam at a photovoltaic collector located on an unmanned autonomous vehicle (UAV), small plane, or helicopter. The current range of the system is about a kilometer. When the laser hits the photovoltaic device, the photons in the light beam are converted to electricity to fly the AUV. Topics: AI/Robotics | Energy | Physics/Cosmology | Survival/Defense

Engineers at Stevens Institute of Technology have developed a technique to optically modulate the frequency of a laser beam and create a signal that is disrupted significantly less by environmental factors, says Dr. Rainer Martini. The research provides for enhanced optical communications, allowing mobile units not tied to fiber optic cable to communicate in the range of 100 GHz and beyond, the equivalent of 100 gigabytes of data per second. Eventually, the team hopes to extend the reach into the terahertz spectrum. The frequency or amplitude modulation of middle infrared quantum cascade lasers has been limited by electronics, which are barely capable of accepting frequencies of up to 10 GHz by switching a signal on and off.  Marini and his team have developed a method to optically induce fast amplitude modulation in a quantum cascade laser to control the laser's intensity. Their amplitude modulation system employed a second laser to modulate the amplitude of the middle infrared laser, using light to control light. The current detector is only capable of detecting frequencies up to 10 GHz, but Dr. Martini is confident that a new detector will make the system capable of much higher frequencies. With an optical system that is stable enough, satellites may one day convert to laser technology, resulting in a more mobile military and super-sensitive scanners, as well as faster Internet for the masses, says Martini. Ref.: "Optically induced fast wavelength modulation in a quantum cascade laser," Applied Physics Letters, July 7, 2010.