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70 Dossier | Teledyne Energy Systems EDR fuel cell additional reactant tanks for more kWh of energy, or additional fuel cell modules for more kW of charging output. Larger variants are being tested in different configurations. These subsea superchargers are expected to run for 5-10 years between servicing, while being inspected every 6-9 months. That is standard for infrastructure maintenance practices in oil and gas fields, where many of them are expected to be used to provide back-up power to subsea umbilicals or recharge persistently stationed UUV fleets. In addition, Teledyne offers the fuel cell as a product or customised solution for lightweight, long-endurance electrical power wherever access to clean air (as a reactant source) is problematic. That would include UGVs operating in dusty environments, USVs in high sea states or any amphibious UAVs and UGVs that could be splashed or immersed in water for hours at a time but which must be able to continue operating regardless of any changes in their surroundings. Project history The system’s architecture has been greatly inspired by the work of the late Arturo Vasquez, who first conceived the EDR technology and pioneered its development at NASA’s Johnson Space Center prior to his passing in 2013. Development of the Teledyne cell has been led by Robert Wynne (technical specialist at the company) in Dr Thomas Valdez’s team. Wynne had previously worked with (and learned from) Vasquez at NASA, as did Dr Valdez more recently until 2016 – the year he joined Teledyne as manager of chemical systems. “It was around 2010 when Art developed the first prototype of an EDR fuel cell, and the first field-commissioned one was produced for a US Navy UUV in 2013,” explains Dr Valdez. Wynne adds, “That Navy-spec version was our first-generation system, and we unveiled our second-generation system in 2016 – the one that’s standardised as a 15.4 kg, 6 kW unit. The first-gen EDR cell had its ejector, manifolds and several other key parts machine-cut into a block of stainless steel, mainly for simplicity. Doing so meant that essentially the whole balance of plant [BoP] was composed of a single solid part, instead of seven or eight different parts.” However, this also meant the first- generation fuel cell was very heavy. While that was perfectly fine for the US Navy’s large-displacement UUV and its buoyancy requirements, the weight, size and overall design were unsuitable not only for NASA spacecraft but also most commercial UUVs, as well as some UAVs and UGVs that Teledyne could see being developed on the horizon. Hence, development on the more weight- optimised version started between 2013 and 2015. Reactant management The efficiency improvements have come largely from optimising the ejector system inside the manifolds in the BoP, which sits below a water management system, atop which is the cell stack. As with all parallel-flow PEMFCs, hydrogen and oxygen are delivered into the fuel cell from one end – in this case, via separate pressure regulators at the bottom-left of the BoP, piped straight through the water management unit and up into the cells. There, as current is drawn and an operating temperature of 50-70 C is maintained, electrons are extracted from the hydrogen December/January 2021 | Unmanned Systems Technology Approximate layout of the EDR fuel cell and its ejector-driven reactant management system The first-gen EDR cell had its ejector, manifolds and several other key parts machine- cut into a block of stainless steel, mainly for the sake of simplicity