Techniques for Maximizing Efficiency of Solar Energy Harvesting Systems (Invited Paper)

Energy harvesting capabilities enable totally untethered operation of mobile and ubiquitous systems for extended periods of time without requiring battery replacement. This paper examines technical issues with solar energy harvesting. First, maximum power point tracking (MPPT) techniques are compared in terms of solar cell model, tracking source, and controller style. For energy harvesting in conjunction with energy storage, this paper compares batteries and supercapacitors, and discusses trade-offs between complexity of charging circuitry and efficiency. Recent techniques for handling cold booting are also examined in terms of both hardware and software solutions. This paper assumes mainly small-scale photovoltaic sources, although many techniques apply to other sources as well. Together, the increase efficiency is expected to enable more compact, lower cost energy harvesters to bring longer, more stable operation to the systems.