The closed-cycle hydrogen-oxygen PEM regenerative fuel cell (RFC) at the NASA Glenn Research Center (NASA Glenn) has successfully demonstrated closed cycle operation at rated power for multiple charge-discharge cycles. During charge cycle the RFC has absorbed input electrical power simulating a solar day cycle ranging from zero to 15 kWe peak, and delivered steady 5 kWe output power for periods exceeding 8 hr. Orderly transitions from charge to discharge mode, and return to charging after full discharge, have been accomplished without incident. Continuing test operations focus on: (1) Increasing the number of contiguous uninterrupted charge discharge cycles (2) Increasing the performance envelope boundaries (3) Operating the RFC as an energy storage device on a regular basis (4) Gaining operational experience leading to development of fully automated operation (5) Developing instrumentation and in situ fluid sampling strategies to monitor health and anticipate breakdowns This publication is available from the NASA Center for AeroSpace Information, 301-621-0390.
NASA Glenn Research Center (GRC) has recently demonstrated a polymer electrolyte membrane (PEM) based regenerative fuel cell system (RFCS) that operated for five contiguous back-to-back 24h charge/discharge cycles over a period of 120h. The system operated continuously at full rated power with no significant reactant loss, breakdowns, or degradations from June 26 through July 1, 2005. It demonstrated a closed-loop solar energy storage system over repeated day/night cycles that absorbed solar electrical power profiles of 0–15kWe and stored the energy as pressurized hydrogen and oxygen gas in charge mode, then delivered steady 4.5–5kWe electrical power with product water during discharge mode. Fuel cell efficiency, electrolyzer efficiency, as well as system round-trip efficiency were determined. Individual cell performance and the spread of cell voltages within the electrochemical stacks were documented. The amount of waste heat dissipated from the RFCS was also reported. The RFCS demonstrated fully closed-cycle operation without venting or purging, thereby conserving reactant masses involved in the electrochemical processes. Smooth transitions between the fuel cell mode and electrolyzer mode were repeatedly accomplished. The RFCS is applicable to NASA’s lunar and planetary surface solar power needs, providing lightweight energy storage for any multikilowatt-electrical application, where an environmentally sealed system is required.
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