Dielectric elastomer generators (DEG) are well suited to harvest energy from natural motion sources (e.g. water, human locomotion). DEG require a source of high voltage charge to generate energy. In low cost, low power DEG, a high voltage charge source is expensive and impractical to implement. The Self Priming Circuit (SPC) can be used to remove the high voltage charge source and replace it with a low voltage one. The SPC works by moving charge onto and off the DEG in synchrony with DEG compression to enable voltage boosting. For the initial cycle a low voltage source is still required in the form of a battery or similar device which in some instances can completely discharge, rendering the DEG useless. Another approach is to include an electret into the DEG design. The electret acts as a permanent voltage source for the DEG and SPC. This allows the DEG to receive a medium voltage (much higher than a battery) from the electret and then boost this voltage up to a high voltage where generation efficiency is improved. This paper presents an integrated SPC with an electret charge source that is capable of boosting quickly to a high voltage without the addition of external charge.
Dielectric Elastomer Generators (DEG) can capture energy from natural movement sources such as wind, the tides and human locomotion. The harvested energy can be used for low power devices such as wireless sensor nodes and wearable electronics. A challenge for low power DEG is overcoming the losses associated with charge management. A circuit which can do this exists: the Self Priming Circuit (SPC) which consists of diodes and capacitors. The SPC is connected in parallel to the DEG where it transfers charge onto/o_ the DEG based on changes in the DEG capacitance. Modelling and experimental validation of the SPC have been performed in the past, allowing design and implementation of effective SPCs which match a particular DEG. While the SPC is effective, it is still an external circuit which adds additional mass and cost to the DEG. By splitting the DEG into separate capacitors and using them to build an SPC, the Integrated SPC (I-SPC) can be realized. This reduces the components required to build a SPC/DEG and improves the performance. This paper presents a mathematical model with experimental data of a first order I-SPC. Additionally, comparisons between the SPC and I-SPC are drawn.
Soft and stretchy dielectric elastomer (DE) sensors can measure large strains on robotic devices and people. DE strain measurement requires electric energy to run the sensors. Energy is also required for information processing and telemetering of data to phone or computer. Batteries are expensive and recharging is inconvenient. One solution is to harvest energy from the strains that the sensor is exposed to. For this to work the harvester must also be wearable, soft, unobtrusive and profitable from the energy perspective; with more energy harvested than used for strain measurement. A promising way forward is to use the DE sensor as its own energy harvester. Our study indicates that it is feasible for a basic DE sensor to provide its own power to drive its own sensing signal. However telemetry and computation that are additional to this will require substantially more power than the sensing circuit. A strategy would involve keeping the number of Bluetooth data chirps low during the entire period of energy harvesting and to limit transmission to a fraction of the total time spent harvesting energy. There is much still to do to balance the energy budget. This will be a challenge but when we succeed it will open the door to autonomous DE multi-sensor systems without the requirement for battery recharge.
Dielectric Elastomer Generators (DEG) offer an opportunity to capture the energy otherwise wasted from human motion. By integrating a DEG into the heel of standard footwear, it is possible to harness this energy to power portable devices. DEGs require substantial auxiliary systems which are commonly large, heavy and inefficient. A unique challenge for these low power generators is the combination of high voltage and low current. A void exists in the semiconductor market for devices that can meet these requirements. Until these become available, existing devices must be used in an innovative way to produce an effective DEG system. Existing systems such as the Bi-Directional Flyback (BDFB) and Self Priming Circuit (SPC) are an excellent example of this. The BDFB allows full charging and discharging of the DEG, improving power gained. The SPC allows fully passive voltage boosting, removing the priming source and simplifying the electronics. This paper outlines the drawbacks and benefits of active and passive electronic solutions for maximizing power from walking.