Harvesting energy using the pyroelectric effect has seen growth as a potential energy source for low power applications, such as self-powered and autonomous wireless sensor networks. The scavenged energy is generally at low power levels, from mW to less than µW. While the voltages generated by pyroelectrics can be appreciable, the electric currents can be low in the order of nano-amps. In the case of pyroelectric harvesting the frequency of operation can also be low, typically much lower than 1 Hz, due to the slow temperature oscillations and transients in systems of large thermal mass. The combination of low power levels and low frequency of operation means that methods of storing electrical energy generated by pyroelectrics and the influence of inherent second order losses is of importance to create efficient harvesting devices. This paper examines the second order characteristic effects of practical capacitors and diodes for storage. The stored energy decay characteristics for commercially available components are examined and the data is used to characterise the second order effects. Selected components are then used in a pyroelectric harvesting system to determine potential improvements by appropriate selection of components with low loss.

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The emerging field of living technologies aims to create new functional hybrid materials in which living systems interface and interact with inanimate ones. Combining research into living technologies with emerging developments in computing architecture has enabled the generation of organic electronics from plants and slime mould. Here, we expand on this work by studying capacitive properties of a substrate colonised by mycelium of grey oyster fungi,Pleurotus ostreatus. Capacitors play a fundamental role in traditional analogue and digital electronic systems and have a range of uses including sensing, energy storage and filter circuits. Mycelium has the potential to be used as an organic replacement for traditional capacitor technology. Here, were show that the capacitance of mycelium is in the order of hundreds of picofarads and at the same time a voltage-dependent pseudocapacitance of the order of hundreds of microfarads. We also demonstrate that the charge density of the mycelium 'dielectric' decays rapidly with increasing distance from the source probes. This is important as it indicates that small cells of mycelium could be used as a charge carrier or storage medium.