Energy harvesting (EH) or scavenging is the use of ambient energy to provide electrical power for small electronic and electrical devices.
The technologies employed variously convert human power, body fluids, heat differences, vibration or other movement, dirt, vegetation, ultraviolet, visible light or infrared to electricity.
Most are in the laboratory and many are solutions looking for problems, yet practical applications of some harvesting technologies have been around for some time. They vary from the bicycle dynamo to the solar powered calculator or road sign.
Proven solutions often store the energy usually either with a capacitor, as with some bicycles, or with a rechargeable battery as with some wind-up lanterns. However, certain wind-up radios manage this with clever clockwork that releases the energy at a required steady rate.
We therefore have a considerable repertoire of energy harvesting technologies and uses today but there is a tsunami wave of new technologies and applications that they will be both affordable and usable in the next few years.
The emerging applications include:
1. Buildings - a huge market, where over 500,000 wireless control devices with no battery or ac mains connection have already been sold. These sharply reduce up front and ongoing costs, including huge gains in the cost of energy used for air conditioning etc. in buildings.
2. 90% of envisaged uses of Wireless Sensor Networks (WSN) are impractical without energy harvesting. These mesh networks are rarely feasible because, in the biggest projects envisaged, such as those where nodes are embedded in buildings and machines for life or on billions of trees, the batteries would be inaccessible or prohibitively expensive to access.
3. Getting almost free power for electronics and lighting to Africa where batteries are not affordable: indeed, they are rarely even obtainable.
4. Bionics and sensors are needed in the human body that stay there for the life of the patient. These are the focus of a huge new research effort.
5. Mobile phones and laptop computers have batteries that frequently go down. Indeed, the power situation gets worse as more functionality is added, this inconvenience involving two billion people.
In all these applications there is now a delightful conjunction of progress by which new forms of lighting and electronics need far less electricity and new forms of energy harvesting are better able to provide it. They can meet in the middle in just a few years.
These are analysed in more details in the IDTechEx report, "Energy Harvesting and Storage for Electronic Devices 2009-2019"
Dr Peter Harrop is chairman of IDTechEx