Low-power microcontrollers have done much to improve longevity in energy-harvesting systems. Clever architectures and use of low-power modes lets micros draw nano amperes of current while preserving registers and configuration data. This allows designers to use smaller and less dense energy storage solutions that were not feasible in the past.
Nevertheless, energy storage, which plays a key role in ambient-energy-harvesting systems, is still needed in most cases as a power buffer to store enough energy to provide the power bursts needed to acquire and transmit data during peak demand, particularly if data is going to be transmitted across a wireless network. These energy storage devices generally take the form of either a battery or a super capacitor (super cap).
Super caps, which bridge the gap between conventional capacitors and rechargeable batteries, offer performance characteristics that are well suited for energy-harvesting environments. Super caps can provide capacitance values up to 10,000 times that of conventional electrolytic capacitors. Moreover, while in the past super caps could only provide about 10 percent of the energy storage density of chemical batteries, new super cap chemistries and architectures are yielding higher-density energy sources that can be charged relatively quickly.
Read More: Supercapacitor Options for Energy-Harvesting Systems