Hybrid Power System for High Energy Density Space Systems

Compact rechargeable power sources with high energy density are crucial to sustained operation for robotic vehicles on the lunar surface as well as for many other space systems. Fuel cells that use hydrogen and oxygen to generate electricity can offer at least three times the specific energy of state-of-art rechargeable lithium-ion batteries, especially for missions that need to operate for more than several days continuously at nominally consistent power levels. Hydrogen and oxygen are generated by electrolysis of water. These reactants can be stored and used to power fuel cells. To achieve a power source that has high both specific energy and high specific power, fuel cells can be hybridized with high-power lithium-ion batteries. Energy can be harvested using photovoltaic arrays, microwave power receivers, and other power generating subsystems. A possible functional system architecture for such a hybrid power generation and storage intended for eventual sustained lunar surface operation has been developed and tested at JPL.