As you walk around your yard on a typical day, energy in the form of light, thermal, wind, mechanical and electromagnetic radiation is present at virtually every turn. The harnessing and collection of this ambient energy into a useful form is called Energy Harvesting, Energy Scavenging or sometimes Micro-Energy. If you think about a large commercial scale windmill, the turbine blades only capture high potential energy directly in contact with the blades. They need a fairly high-sustained wind speed to turn this potential into usable electricity. All the potential energy in between one windmill and the next, and between each wind farm and the next is lost potential and so on. In the past, standard methods of capturing energy were not efficient enough to convert the relatively low levels of energy into usable amounts for powering electric or electronic devices. Further, efficient long-term energy storage has presented additional challenges.
In recent years, ambient energy harvesting has become a practical and logical advancement in energy systems development. Through thin film batteries and new transducer technology, energy harvesting may well be the next great frontier in the renewable energy industry.
To capture, convert, store and distribute energy in a form that can be used to power electrical systems, Energy Harvesting uses a variety of highly efficient components. Depending on the energy being sourced, an energy harvesting system may have solar panels for light energy, vibration transducers, piezoelectric for converting pressure, kinetic for movement, inductive for rotational or motion, thermoelectric for heat or temperature differential, and electromagnetic or similar devices for input power sources. These energy resources will be converted into useful energy further down the system once they are stored. (See Diagram)
In portable or remote sensor applications, Energy Harvesting can use one or more rechargeable batteries or storage capacitors to store the collected energy for operation. There can be drawbacks to each of these storage methods because of rechargeable battery life cycles of a few hundred charge/discharge cycles and super capacitors with discharge potential of up to 20% per day. This can cause much of the converted energy to be wasted. Thin-film batteries may provide a more practical energy storage solution since it can support more than 5000 charge/discharge cycles and can have a self-discharge rate of less than 3% per month.
What does all this mean to you?
As new systems are developed, small-scale low energy systems will be able to capture, store and use energy from a very wide array of sources for an almost limitless number of applications. Energy is all around us so lets keep our minds open to all the potential opportunities for powering our lives both now and in the future.
Energy Harvesting Block Diagram
