Highlights from the Energy Harvesting Technology Event, London

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Raghu Das, CEO at IDTechEx, attended this one day event in London held by the UK Government Knowledge Transfer Network (KTN). Energy harvesting is the use of technologies to generate electricity from the environment, which can be used to power electronics and electrics.

Different technologies can be employed depending on the energy source. For movement, mechanical harvesters can be used (which can work from electrostatic, piezoelectric and electromagnetic movement), light, thermal, EM transmission or Human. The consistency of the energy delivered depends on the environment but the aim is 200microWatts as a minimum to be useful in most envisaged applications (excluding losses from storage/conditioning).

A common application of energy harvesting devices is to power wireless sensors. One presenter reported results of a survey that said that 70% of users did not want to roll out wireless sensors after successful trials because the battery life in the sensor is the critical limiting factor. Even though the battery may be cheap, the cost to manually access the sensor and replace the battery can be prohibitive.

Ideally, energy harvesters can be employed to power the wireless sensors for decades. EnOcean, presenting at the event, described how they have installed 4200 wireless and battery-less light switches, occupancy sensors and daylight sensors in a new building construction in Madrid. These are powered by energy harvesters and embedded in the building. This saved 40% of lighting energy costs by automatically controlling the lighting in the building, 20 miles in cables, 42,000 batteries (over 25 years) and most of the cost of retrofitting.

Roy Freeland of Perpetuum covered another case study in the industrial sector. Their energy harvesters are powered by vibration and are being attached to pumps to monitor the condition and activity of the pump. This is being used in oil and gas, water utility and other plants. The power produced from the energy harvester powers the wireless sensor at pre set intervals. More recently, working with The Technology Partnership in Cambridge, UK, Perpetuum have developed a battery-free cellular communications platform - the vibration harvester can power a low power GSM module to radio back condition and other sensed parameters over the GSM network.

Micropelt are developing MEMs based energy harvesting using thermal energy. The device has a heat sink on one side and is attached to a source of temperature. The temperature gradient can be used to generate electricity using n and p type materials. Different materials have different efficiencies depending on the temperature of the source. A challenge with smaller energy harvesters is that they tend not to produce much energy but Micropelt have tackled this by having many of the circuits in series on a chip surface.

There are a significant amount of developments emerging from universities too. For example, Imperial College, UK, is working on smaller, higher power devices. The University of Southampton has demonstrated screen printed piezoelectric harvesters, supplying 118microWatts with a voltage of 4.1 Volts into a load of 140KOhms.
Battery technology not keeping up
There was agreement from many that battery technology needs more development. Usually the energy harvested is not enough to power a wireless radio, so it needs to be stored until the burst needed to power the wireless radio. A rechargeable battery can be used but these can only be recharged a set number of times, which means the device may need a battery replacement after 5 years or so. The aim is to have devices which do not have to be touched for decades. Alternatively, some employ super capacitors, but these tend to be more expensive and typically have less energy density. There is now new work on super cabatteries, blurring the boundaries of batteries and super capacitors.

New standards are also beginning to emerge for energy harvesters. The International Society of Automation (ISA) is working on lower power wireless devices and also a common interface so different energy harvesting solutions can be compared.

For more information read Wireless Sensor Networks.

IDTechEx is also releasing a new report "Energy Harvesting & Storage 2009-2019" in January 2009 and followed by an event - "Energy Harvesting & Storage" pertaining to electronic devices which will be held in Cambridge, UK in June 2009.

The event will focus on the application of energy harvesting, including Wireless Sensor Networks, with needs from major end users. This will be followed by presentations from leading developers and universities covering energy harvesting technologies and storage solutions. Progress with standards, low power circuit development, case studies and forecasts will be covered.

Presenters, exhibitors and attendees will be international. The two day event will feature optional masterclasses and tours to local companies developing the technology. It will be held in Cambridge where there is significant activity on the topic - from companies such as Philips, The Technology Partnership, Nokia, Cambridge Consultants, Auto ID Labs and others. Cambridge is conveniently accessible to Europe from Stansted airport. More details will be available shortly at www.IDTechEx.com.

If you would like to get involved, please contact Raghu Das at r.das@IDTechEx.com.

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