Plug and Play Energy Harvesting Systems

Small electronic devices are normally powered by batteries, which are quite limiting because they need to be replaced or recharged when they run out. This project is looking at getting rid of batteries, and instead using 'free' energy which is present in the environment (such as light, wind, heat, or vibrations) to provide electricity for low-power electronics. We are concentrating on powering wireless sensors, which can monitor things like machines in factories, or even the engine on a car, to make sure there aren't any problems which could cause them to break down. To conserve energy, these sensors spend most of their time asleep, but wake up every so often to take a measurement and transmit it wirelessly.

It is not possible to change the energy sources of existing systems without modifying their electronic circuitry (a process which is costly and time-consuming). You can't simply unplug a solar cell and plug in a wind energy harvester because the circuitry needed to process the energy is completely different. This means that, before installing a system, you need to know exactly what energy sources you will be using, and it's impossible to change systems after they have been deployed. This is a big limitation and means that developing and installing an energy-harvesting sensor system is not straightforward.



This research has developed a system that lets you plug in whatever energy source is appropriate (e.g. a tiny solar cell or a small wind energy harvester) to provide energy to your system. It also allows it to see how much energy is available, which means that it can decide how often it can wake up and do the measurements. This is a big step forward over the state-of-the-art, because the existing systems have to be redesigned to cope with different types of energy. You can connect up to six different energy modules to our system, meaning that it is very flexible. You can even connect batteries if there is no 'free' energy available!

The system is based on two new developments: the "Common Hardware Interface" (CHI), which provides the electrical connection between the different components of the system; and the "Energy Electronic Data Sheet" (EEDS), which stores the operating parameters for the energy resources on the devices themselves. The CHI allows the wireless sensor's microcontroller to individually monitor each of the energy modules (to look at how much power is generated or energy is stored). The EEDS stores the data which allows the microcontroller to interpret these measurements.

The plug-and-play system supports up to six energy modules: for example, if it's appropriate to your application, you could connect a few energy harvesters and a couple of energy storage devices. The energy modules we have developed so far include energy harvesters for light, temperature difference, vibration, and wind; and energy storage devices including rechargeable and non-rechargeable batteries, and supercapacitors. We have also developed a module which lets you power your node from mains electricity, which is useful if your sensor is near a power socket.

This is a really flexible system, as it allows you to attach appropriate energy sources and storage devices when you deploy your system, and even allows you to reconfigure your system after deployment. It's a step-change over the existing technology, for which you have to re-design the hardware to cope with different types of energy. It's a plug-and-play system which allows sensor nodes to be energy-aware and adapt to how much energy is available to them. It has the potential to reduce the deployment cost of wireless sensors, and ensure that sensors can adapt to their energy status so that they can be reliable over many years.

For more information, please contact Dr Alex Weddell, University of Southampton.