What is energy harvesting?
Energy harvesting is the extraction of usable energy (usually converted into electrical energy) from otherwise wasted energy available in the environment. On the macro scale (MegaWatts – MW) this includes hydro-electricity, wave power, solar panels, and wind turbines. However for wireless sensing, we are talking about harvesting immediately available energy such as vibration, heat, light, and RF energy to produce milliWatts – mW.
So why is there so much interest in energy harvesting? Simply, you cannot get the full benefit of wireless unless the power source is also wireless. This means either a battery or some form of energy harvester. Until recently, the usual power source available to power a wireless sensor node or network (WSN) has been batteries. With their limited and non-deterministic life span, hazardous content, shipping and disposal requirements, batteries alone are not likely to provide a power source that will last the life cycle of the WSN application without maintenance intervention. The ideal solution is an energy harvester that is “fit and “forget” and will have a lifespan in excess of the WSN that it is powering. …
End users who have trialed battery powered WSNs have generally become very enthusiastic about the benefits. However, we are now seeing views being expressed that the power supply issue must be resolved, and changing batteries is not acceptable in most industrial situations. This is not only because of the cost of the work to order, stock, organize, and physically replace batteries but also, particularly in hazardous area and inaccessible areas, there is an understandable reluctance to send maintenance staff into potentially dangerous areas. The major systems builders are, therefore, almost without exception working on offering energy harvesting powered options for their WSNs.
A good example is the GE Bently Nevada wireless condition monitoring system installed as a pilot at Shell’s Nyhamna Gas Plant for predictive maintenance. This was a site built in Norway to process natural gas from the Ormen Lange field in the North Sea and pump it across to England. Although it was a greenfield site, it was found the cost of hard wiring was excessive to monitor most of the plant. Therefore a wireless system powered by vibration energy harvesters was used on a number of machines to provide full vibration data from accelerometers to the central data processing system.