Low-Cost, Durable Organic Batteries for Dispatchable Solar Applications

The declining cost of solar technology for electricity generation has led to a dramatic increase in its deployment. However, the intermittent nature of solar photovoltaic generation presents a significant challenge for grid operators, and it is widely recognized that co-located, inexpensive and reliable energy storage is required to promote the stability and operational flexibility of the grid. Ideally, such systems would be fully integrated in order to provide an efficient and inexpensive means of storing energy from a photovoltaic installation on a time scale ranging from a few hours to several days. This project takes advantage of a recently developed organic redox flow battery that uses a single active material in three different oxidation states to achieve low cost, robust energy storage. By incorporating a unique control system to dynamically adjust certain functional parameters in the cell stack, the battery can be efficiently charged from a highly variable, relatively low voltage source such as a photovoltaic array. Likewise, these parameters can be effectively tuned upon battery discharge in order to optimize power output to the grid. The overall goal of Phase I is to fabricate a 12 Volt test rig incorporating a photovoltaic array, a multi-cell flow battery stack, and a fully functional control system with all associated pumps, valves, and hardware. Specific tasks will include (1) measure and optimize single cell operational parameters for several different cell geometries; (2) construct a fully functional 6- cell bench test system; (3) fabricate and perform final adjustment of an electrical and flow control system to optimize charging with the variable output of a photovoltaic array; (4) upgrading the control system to govern dispatchable power generation, and (5) creating a final test report with complete performance specifications. An opportunity for a larger Phase II pilot installation upon the successful completion of this project has already been arranged. This pilot will allow a more thorough analysis of the operational costs, use cases, and overall “real world” performance of the system. The ultimate objective of the project is the commercial implementation of these systems to provide efficient energy storage for dispatchable solar generation, thus improving grid stability and fostering the increased adoption of renewable sources.