PhD Project by Jens Munk Nielsen

Project Title: Interdigitated Solar Electrochemical Capacitors (INSECTS)
Group: Biomaterial Microsystems
Supervisor: Stephan Keller
 
Project description
The increasing importance of the Internet of Things (IoT) for applications within e.g. climate monitoring for agriculture, water quality measurements or industrial process control drives the development of compact microelectronic systems for portable wireless sensors. In consequence, the demand for miniaturised power sources is growing rapidly. The next generation of compact energy systems should not only provide safe operation, long time stability and high energy efficiency, but also be based on sustainable materials and technologies to minimise the impact on our ecosystem. A transition from coin cell batteries to a more sustainable energy source would be highly beneficial.

Photovoltaic cells (PVC) are an established technology for large scale harvesting of solar energy. However, the use of conventional PVC in off-grid sensor systems remains challenging. For sensor measurements and wireless signal transmission typically a peak output power of a few mW is required which is difficult to achieve with a miniaturized PVC on a cloudy day. Furthermore, short-term shadowing effects (e.g. a bird flying by) cause glitches in the power supply, which can be detrimental for signal transmission. Microsupercapacitors (µSC) have emerged as promising candidates for sustainable energy storage in microchips and portable systems. Potentially, µSC could be employed to increase the peak output power of PVC-based energy systems and provide a more stable energy supply without power glitches. However, simple assembly of commercial µSC and PVC results in energy losses, bulky systems and the risk of connection failures. 

The overall aim of INSECTS is to develop a novel compact sustainable energy system with the potential of replacing batteries in wireless sensor networks and portable devices. More specifically, we will conceive a solar electrochemical capacitor (SEC) combining solar energy conversion in PVC with energy storage in µSC in a single integrated platform. During illumination, the PVC will charge the µSC and allow for temporary storage of the harvested energy, after which the µSC will discharge and provide the peak power required for sensor actuation or signal transmission.