Waste to energy is an important topic in the space technology field as it addresses energy recycling and generations in environment where it is scarce. The Naval Research Laboratory (NRL) has been dealing with this topic and tries to join together the space qualified actuators, electronics, and different mechanisms. The research group set out a goal to investigate low power microbiotic systems that are powered by microbial fuel cells. Generally, there is a key issue with this method, though - at low masses and volumes these systems provide very low power availability. The authors of the paper investigated the possibilities to increase the power generation of these systems and reduce overall electronics consumption in space systems.
The goal of the research was to advance the current state of the integrated robotic systems that unite the following research areas:
- Low power electronics (develop an low power electronics board, monitor and control the power consumption of all components)
- Low power mobility (develop a low power robotic locomotion system that would be suitable for surface or microgravity environment on 1 kg sized vehicle)
- Microbial fuel cell energy generation (develop a microbial fuel cell, test it and determine the power output of it, and use it to charge the energy storage device)
Several successes were achieved in the low power electronics area. The main concern was that the energy transfer between the microbial fuel cell (BFC) and the energy storage or the actuators will not be efficient enough. This step required low power electronics with low losses and optimized components that are carefully chosen for this specific task. Different simulations were performed to obtain the best combination of the components. The authors were able to show that the BFC was able to charge a super-capacitor to a point where an LED is turned on and also power a small 1.5V motor.Specific areas and methods were identified that allows the possibility to carefully narrow down the possible components that can be used for increased efficiency in the power harvesting and energy conversion circuitry. Also, range of components were identified that allows to conserve the area and volume on the board.
Creating systems that involve electro-mechanical systems leads to many precautions that have to be considered prior the creation of the final design. The most important aspect in the context of this research, is that all the systems have to be energy efficient. The authors also decided that small but more frequency movements are more important in the locomotion part of the research. This allows faster recharge times of the energy storage device. Small electrical charge was used to build up the mechanical potential, but this lead to long operation time of the system. The authors carefully examined each component in different systems to find ways how to transfer more power to the actuator mechanism. The authors were able to summarize the important characteristics of the components that will lead to more optimal results - higher voltage, terminal resistance, torque constant, speed torque gradient, and capacitance. The capacitor (energy storage) is the mots important component and has the largest effect on the capabilities of the actuator. It was concluded that the MFC does not practically produce enough energy to power any investigated actuator at the size scale of the proposed designs.
Ultimately, it seems that authors have significantly contributed to the advancement in the field of low power electronics powered by microbial fuel cells. The most important achievement of the research was the proof that microbial fuel cells can be used as a power source for microrobotic systems. The proof was not obtained not only by simulations but with real life prototypes that were able to provide real-life data. The authors believe that this technology is still far from practical use in daily life, and further research is required to optimize the systems, find more efficient ways to design the systems, increase the power transfer efficiency between the sources and the actuators, and obtain a more capable microbial fuel cell with higher power output.
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