Article
Bright outlook for energy harvesting
This article has been taken from The Gen newsletter - Summer 2009.
Click here to download the pdf.
Energy harvesting - the use of local energy sources such as wind, sun or vibration to power devices to operate in environments previously thought 'out of bounds' - is growing up fast and making news.
The technology, which is also known as energy scavenging, now has specialist publications and web forums devoted to it. Earlier this year I attended the Energy Harvesting and Storage conference and exhibition in Cambridge where new applications and technologies were showcased.
While the idea of energy harvesting is not new - think water wheels and windmills - its modern day use has focused on applications where it is impractical or too expensive to use batteries, or too remote (or the device too disparate) to access grid electricity.
Potentially, an almost limitless number of energy sources can be used and include radiation, machine vibration, thermal gradients, wind, sun, tides and human movement. Unlike renewable energy technologies, which predominantly generate energy remotely before transporting it through electrical cables to the end user, harvested energy is collected and used locally - no more than a few metres or even millimetres away from the source.
Many energy harvesting applications are already very familiar, most notably the solar powered calculator and kinetic watch. What is particularly exciting right now is that energy harvesting is moving beyond 'gadgets' and small devices and the rate at which it is being commercialised is accelerating. Improved product design, especially in power storage, means that the concept is now valid even for safety critical applications. Medical implants powered by blood flow for instance would have been unheard of ten years ago. Now, industry is predicting that this application could be on the market within the next decade.
Energy harvesting can add real value to existing products, services and processes by cutting costs (especially ongoing running costs), extending operational time, and delivering greater convenience. For example, many bus stops now feature electronic information boards. In urban areas, these are easily powered by mains electricity, but in rural areas, where perhaps the information is even more valuable, connecting to the grid is too expensive and batteries too costly to monitor and maintain. But by using the power harvested from a solar cell and wind turbine, an information panel can operate with very little maintenance.
In industry, production and processing operations are hugely reliant on sensors to monitor machine performance. An array of battery powered sensors is both expensive to buy and time consuming to maintain; the installation of additional wiring across a complex industrial plant, in order to access mains electricity, can be prohibitively expensive. A wireless sensor network powered by harvested energy from machine vibration is cheap to install and maintain, yet still delivers the level of accuracy, robustness and reliability required.
Of course, energy harvesting is not the best solution for every product. Expertise is required to match the energy needs of a device to the energy sources available, and the business case behind its use must be proven. In particular, power generaion must not be confused with energy saving. For example, a ticket machine could be powered by the physical vibrations of commuter footfall, but the energy harvesters required would be expensive to install, and the energy collected would be trivial. If energy savings are the objective, it would be better to improve the efficiency of the heating, lighting and ventilation systems in the ticket hall.
Energy harvesting, used appropriately, can lead the way to exciting new applications in almost every industry sector, and in almost any physical location. The key to successful energy harvesting is a thorough understanding of the science behind it and the environmental context in which it will operate, backed by a realistic business appraisal, in order to create practical and profitable solutions which really meet market needs.