University spin-off launches novel power source for sensors

Citation

(2007), "University spin-off launches novel power source for sensors", Sensor Review, Vol. 27 No. 1. https://doi.org/10.1108/sr.2007.08727aaf.004

University spin-off launches novel power source for sensors

University spin-off launches novel power source for sensors

Perpetuum Ltd, a spin-off from the University of Southampton, UK, has launched a unique microgenerator that harvests kinetic energy from vibrating machines and equipment and converts it into electrical power. The idea arose from the need for a battery-free power source during research into embedded sensors. Following the development of prototype microgenerators the company was set up with seedcorn funding from SULIS and IP2IPO in 2004 and received a further $4 million investment from Quester funds and Top Technology in 2006.

The microgenerators are based on an electromagnetic coil and magnet arrangement and operate via Faraday's law of induction. They are designed for use on any type of AC synchronous motor-powered equipment and resonate at mains frequencies (50 or 60Hz) with a bandwidth of 0.2Hz. The amount of power generated varies according to the magnitude of the vibration, e.g. 0.4mW at 25mg and up to 5mW at 100mg. It can generate sufficient power to activate a wireless transmitter sending up to 6Kbytes of critical data every few minutes or smaller amounts of data, such as temperature readings, several times each second. Previously, wireless sensors based on IEEE 802.15.4 and other low power transmitters had to rely on battery power but the model PMG7 (Figure 4) is matched to the power requirements of 802.15.4 systems, although they can also be used for other applications with appropriate duty cycle energy requirements such as low power sensors, microprocessors and transceivers. The 802.15.4 wireless standard defines a short range, low power, low data rate wireless interface, designed specifically for devices that use limited power and is the basis of the Zigbee open standard specification and many proprietary systems. These developments have been made possible by low power chip sets such as the Chipcon CC2420 from Texas Instruments which is the industry's first 2.4GHz 802.15.4 compliant RF transceiver.

Figure 4 The PMG7 microgenerator (Perpetuum)

Perpetuum has worked with US partner RLW, Inc., a specialist in condition monitoring systems, who has developed the S⁵NAPe remote sensing module which combines the PMG7 generator with an accelerometer, temperature sensor and the electronics (Figure 5). The module uses the microgenerator's power to charge an external storage capacitor which, once fully charged to 3.3V, powers the circuitry. These units are totally wire- free and offer a number of benefits over hard-wired or battery-powered devices: installation is simplified; costs and maintenance requirements are reduced; they can be used almost anywhere; and reliability is high. They have been the subject of several recent trials and a major international oil company has used three S⁵NAP modules for a trial installation on a test pumping circuit. The devices were mounted with magnets onto pumps, motors and pipe-work to generate condition monitoring data. With support from the American Office of Naval Research, a module has been installed on a compressor at the US Navy's base at Philadelphia and has successfully demonstrated the transmission of vibration and temperature data. In the UK, Yorkshire Water is using six S⁵NAP units to monitor the condition of sludge pumps, air compressors and fan motors at its Esholt plant (Figure 6). The aim is to detect blockages, cavitation and other faults as well as ascertaining whether more effective maintenance strategies could be adopted. These units could play a vital role within the company, as pump repairs typically cost around £1.2 million per year. According to Yorkshire Water, the S⁵NAP modules cost around a third of a conventional, hard-wired alternative. As well as boosting the condition monitoring market, Perpetuum hopes that the technology will satisfy a range of other applications that would benefit from wireless sensors.

Figure 5 Inside the S⁵NAP module (Perpetuum)

In addition to investigating further uses for its existing products, working with Southampton University Perpetuum is planning to develop a far smaller device based on silicon MEMS technology. Work has already started and it is anticipated that a silicon package with dimensions of 5 x 5 x 1.5mm could produce a few hundred microwatts of power under suitable conditions.

Figure 6 S⁵NAP module mounted on a pump at a Yorkshire Water plant (Perpetuum)

For further information, contact: Perpetuum Ltd, Epsilon House, Southampton Science Park, Southampton, Hants., SO16 7NS, UK. Tel: +44 (0)23 8076 5888. E-mail: info@perpetuum.com, Web site: www.perpetuum.com