This Small Business Innovation Research Phase I project is intended to establish the feasibility of a novel sodium-sulfur FLOW battery for use in the storage of power generated from wind farms and solar arrays, which represent two of America's best options for reducing its dependence on foreign oil. Because of their variable rates of power generation, both need some form of power storage system in order to distribute the power produced more evenly. Sodium-sulfur (NaS) batteries produced commercially today have high power density and represent a viable choice for power storage; however, the current versions are bulky, expensive and operate at 350 °C. The project will investigate critically needed scientific data in support of the development of a novel flow NaS battery that has the potential to (1) operate at temperatures as low as 50 °C and (2) reduce the cost of battery NaS storage systems by as much as 50%. This project will isolate each of the critical elements of such a battery and assemble/test a planar 50 W feasibility demonstration of the battery that operates at 50 °C or less and the results should serve as the foundation for subsequent scaled up development to 5 kW.
The broader/commercial impact of this project will be a viable, large-scale power storage system for wind farms and solar power systems. If power produced by wind increases at the rate projected by the Department of Energy from 11.6 GW in 2006 to 300 GW in 2030, the total market for storage batteries is estimated to be $60 billion over the next 22 years. It is also estimated that as much as 10,000 MW of solar thermal power could come on stream in the next ten years providing an addition market for new storage batteries for that application of an estimated $10.5 billion. In addition, a flow NaS battery developed to be developed by this project can be used in the desulfurization of petroleum streams producing an additional market of over $10 billion through 2030. The basic concept and design of the sodium sulfur battery has remained essentially unchanged since its discovery the 40 years ago; and the proposed flow battery represents such a departure from the previous design that it has the potential to create new markets that have not been previously considered suitable for high temperature batteries.
Project Outcome Report This Small Business Innovation Research Phase I project provided critically needed scientific data in support of the development of a novel sodium-sulfur flow battery for use in the storage of power generated from wind farms and solar arrays, which represent two of America’s best options for reducing its dependence on foreign oil. Because of their variable rates of power generation, both wind and solar power generation need some form of power storage system in order to distribute the power produced more evenly. Sodium-sulfur (NaS) batteries produced commercially today have high power density and represent a viable choice for power storage; however, the current versions are bulky, expensive and operate at 350 °C. The work carried out during this Phase I proposal period addressed the development of a novel flow NaS battery that, if successfully developed, has the potential to (1) operate at temperatures below 50 °C and (2) reduce the cost of battery NaS storage systems by as much as 50%. The broader/commercial impact of this project is expected to be a viable, large-scale power storage system for wind farms and solar power systems. If power produced by wind increases at the rate projected by DOE from 11.6 GW in 2006 to 300 GW in 2030, the total market for large-scale storage batteries is estimated to be $60 billion over the next 22 years. It is also estimated that as much as 10,000 MW of solar thermal power could come on stream in the next ten years providing an addition market for new storage batteries for that application of an estimated $10.5 billion. What has not been previously appreciated is that a flow NaS battery developed under this program can also be used in the desulfurization of petroleuem streams producing an additional market of over $10 billion through 2030. The basic concept and design of the sodium sulfur battery has remained essentially unchanged in the 40 years since it was discovered by researchers at Ford Motor Company; and the proposed flow battery represents such a departure from the previous design that it has the potential to create new markets that have not been previously considered suitable for high temperature batteries. The SBIR Phase I program just completed isolated each of the critical elements of a NaS battery: (1) the electrolyte, (2) the sodium electrode and (3) the sulfur electrode. Electrolytes in commercially produced NaS batteries are typically dense β"-Al2O3 films 800-1,000 μ thick. Trans Ionics Corporation had previously created improved thin film composite (TFC) electrolytes having dense active layers < 50 μ thick supported on a microporous support, where the total thickness of the composite was < 1,000 μ. The Phase I program just completed resulted in the discovery of a strong, lightweight (0.025 gm/cm2) TFC with an active layer < 35 μ and a reduction on the total thickness of the supported electrolyte of 90% over our best previous electrolyte. This is expected to result in a significant increase in the Specific Energy (Wh/kg) and the Energy Density (Wh/L) of the battery. Proprietary sodium and sulfur electrode compositions were also developed that allow the battery to be operated in either a flow mode for large (1-10 MW) scale power storage or a batch mode for smaller (5-10 kW) batteries for electric vehicles. A small battery incorporating all of these unique features was assembled and tested. Results showed conclusively that the new battery behaves very much like the high temperature version with an output voltage of approximately 2.1 V. The significant advances in this battery design are expected to result in a cost of <$500/kWh versus $800/kWh for the high temperature battery, a savings of almost 40%.
