ENERgy Harvesting

ENERgy Harvesting
Energy Harvesting is the process of capturing minute amounts of energy from one or more of these naturally-occurring energy sources, accumulating them and storing them for later use. Energy-harvesting devices efficiently and effectively capture, accumulate, store, condition and manage this energy and supply it in a form that can be used to perform a helpful task. Similarly, an Energy Harvesting Module is an electronic device that can perform all these functions to power a variety of sensor and control circuitry for intermittent duty applications.
Energy harvesting (also known as Power harvesting or energy scavenging) is the process by which energy is captured and stored. Frequently this term is applied when speaking about small autonomous devices, like those used in sensor networks. A variety of different sources exist for harvesting energy, such as solar power, thermal energy, wind energy, salinity gradients and kinetic energy.
Traditionally electrical power has been generated from fossil fuels in large, centralized plants. Large-scale ambient energy, such as sun, wind and tides, is widely available but trickier to harvest. In urban areas, there is a surprising amount of electromagnetic energy in the environment as a result of radio and television broadcasting.
Energy harvesting devices converting ambient energy into electrical energy have attracted much interest in both the military and commercial sectors. Some systems convert random motion, such as that of ocean waves, into electricity to be used by oceanographic monitoring sensors for autonomous operation. Future applications may include high power output devices (or arrays of such devices) deployed at remote locations to serve as reliable power stations for large systems. All of these devices must be sufficiently robust to endure long-term exposure to hostile environments and have a broad range of dynamic sensitivity to exploit the entire spectrum of wave motions.


Energy can also be harvested to power small autonomous sensors such as those developed using MEMS technology. These systems are often very small and require little power, but their applications are limited by the reliance on battery power. Scavenging energy from ambient vibrations, heat or light could enable smart sensors to be functional indefinitely. Several academic groups have been involved in the analysis and development of vibration-powered energy harvesting technology, including the Control and Power Group and Optical and Semiconductor Devices Group at Imperial College London, MIT, UC Berkeley and Southampton University.
Typical power densities available from energy harvesting devices are highly dependent upon the specific application and design of the harvesting generator. For motion powered devices , typical values are a few μW/cc for human body powered applications and hundreds of μW/cc for generators powered from machinery.