According to Aviation Week, “the integration of nanoelectrofuel (NEF) flow batteries with rim-driven electric motors” is being investigated by the National Aeronautics and Space Administration (NASA), to “produce a safe, clean and quiet propulsion system for aircraft.”
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The idea behind the research is to produce a new battery, containing rechargeable liquid batteries, that can propel a small uncrewed aircraft. Unlike traditional motors, which are fueled using aviation gasoline or kerosene, the new battery would allow for rechargeable, greener, and quieter flights while also mitigating the fire risks associated with lithium-ion batteries.
The integration of liquid batteries with rim-driven electric motors is in the very early stages of development. Although there has not been much progress made so far, NASA researchers believe that the technology has a lot of untapped potential.
The research is part of the agency’s ‘Armstrong Flight Research Center’s Aqueous Quick-Charging Battery Integration for Flight Research’ (Aquifer) project, which aims to develop non-explosive energy storage technology. The aim is to combine this project with research already undertaken by the Argonne National Laboratory and Illinois Institute of Technology.
The R&D alliance, known as Influit Energy, headed by founder John Katsoudas, claim that their NEF battery has an energy density which is l.5 times larger than conventional lithium-ion batteries, at half the cost. Another advantage is that it can conform to different shapes, and is capable of rapid charge refueling; meaning that they could, in theory, be used for aviation purposes.
The battery can be recharged by pumping new liquids into storage tanks, which is an advantage as it enables the battery to be recharged from a vehicle rather than a single location connected to the grid.
The battery works by pumping positively and negatively charged fluids through a ‘flowcell’ and into a larger chamber. The fluid is a contains nanoparticles of battery-active materials, which are suspended in a water-based fluid to create an electrolyte.
Currently, this research has produced a battery that contains approximately 60% active materials. This is more than double the content of traditional batteries, which need to include casing, separators, and binders amongst other elements.
NASA aims to produce a NEF battery with a current density of 100mA/cm2 by 2020. This density would allow the system to generate energy at around 125 Watt-hours per kilogram, which is more than that of the traditional lithium-ion.
A lot of development must be undertaken to complete this technology. According to NASA electrical engineer, Kurt Papathakis, in 2018, the project only was able to create a prototype NEF flowcell that was able to produce only a few mA per square centimeter.
We have demonstrated multiple recharge cycles and seen minimum to zero degradation. Also, unlike Li-ion batteries, NEF does not pay a penalty in cycle life for charging above 80-percent capacity or discharging below 20 percent.
Kurt Papathakis, NASA Electrical Engineer
The battery has the potential to eliminate carbon emissions from air travel. In theory, the fluid batteries could be recharged using solar or wind power, therefore dramatically reducing the quantity of greenhouse gasses released into the atmosphere. With more funding and research, this theory could become a reality in the near future.