Our Research

Case Studies of Energy-Driven Computing

Energy-driven computing typically requires a rethink into how the system can deliver the required functionality. On this page, we feature some of the application case studies that we have considered to explore the potential of energy-driven computing, including a battery-free fitness tracker and cycle computer.

Battery-Free Cycle Computer

Traditional bicycle computers (or trip counters) measure the rotation of the wheel by sensing when a magnet mounted on the wheel passes a reed switch (or similar) mounted on the fork. The sensor is wired (or has its own battery to transmit the data wirelessly) to a battery-powered embedded computer which records and displays statistics on the journey.

In this case study, we present a transiently-powered wireless cycle computer which measures distance, speed and active cycling time, and transmits data wirelessly. The system sustains operation by harvesting energy from the rotation of the wheel, operating from minimum speeds of 6kph.

Associated Publications

Battery-Free Step Counter

Over the past decade, there has been a rapid increase in the popularity of wearable and portable devices, such as step counters, to monitor fitness performance. However, these devices are battery-powered, meaning that their lifetimes are restricted by battery capacity. Ideally, wearable devices could be powered by energy harvested from human motion.

In this case study, we developed an intermittently-powered energy harvesting step counter for integrated wearable applications, which removes the energy storage element. The step counter sustains operation by harvesting energy from footsteps using a ferroelectret insole, which also works as an event detection sensor, i.e. the system is powered by the parameter that is being sensed. Designing this required the characterization of the insole to evaluate the amount of energy provided, and analysis of the energy needed by the overall system. The system has an error in steps counted of less than 4% when walking.

Associated Publications