THERMAVANT TECHNOLOGIES LLC — Department of Defense SBIR Phase II: OSD12-EP6

Description

Future military platforms will require more extensive use of electronic power systems to achieve required performance levels. Energy storage is becoming a key enabler for power systems operating with high levels of transient power requirements and supporting fuel-efficiency operations while maintaining capability. High density energy storage which operates continuously at high charge and discharge rates to support these loads under the combination of finite space, high power and energy requirements, stringent safety characteristics and wide upper temperature ranges drive the requirement for advanced cooling systems. Proper thermal management of these high power electronic systems becomes more difficult as increasing power density requirements push heat generating components closer together. This is made more severe due to relatively low full power operating temperature limits (in the range of 55-60C for certain components) which force designers to de-rate the components to ensure reliable operation. The combination of close proximity, volumetric self-heating, and platform coolant temperatures as high as 50C all contribute to increased system volume from redundant storage arrays operating with reduced energy density. While ongoing research efforts are attempting to develop components with higher operating temperature limits, improved methods of efficiently managing the thermal aspects of batteries, capacitors and flywheel motor/generators provides a near-term reduction in the need for component de-rating which would reduce component redundancy and increase system power density. Storage devices with a cylindrical, can-style structure cannot efficiently couple to the high performance cold plates and heat sinks being implemented to cool other components. Although air-cooling methods (including finned adapters, etc.) have been utilized in the past, system volume constraints and platform placement typically remove useful convective flow paths. Other proposed techniques for thermal coupling have included the use of inefficient thermal interface materials, thermal conduction through the electrical terminals, or significant modifications, none of which provide a cost and performance effective solution. Innovative R&D is needed to investigate cooling architectures which can be enabled for cylindrical geometry energy storage components that must be integrated into larger arrays. The technologies should be scalable from small 18mm type cells through motors of 100mm or greater diameter. The cooling architectures should be able to space-efficiently couple to a backplane, being integrated into shelving or cabinet designs to help maintain climate or thermal isolation and regulation throughout the device. The innovative products brought forth through this SBIR effort should not contain precious or hazardous materials, nor require significant interfaces in order to support. It is optimal for these devices to operate such that chilled water is not required, though fresh and/or seawater can be assumed to be available at 40C, with sufficient flow available to meet mission needs. Ambient spaces should be assumed to be up to 60C and worst-case device maximum temperatures should also be assumed to be 60C. In order to maintain density of the energy storage devices, these cooling structures should not expand the individual components greater than 10%, yet be capable of supporting pressure both from the inside in the form of cooling fluid flow, as well as external under compression of a battery pack, expansion during cycling operation, etc. If a special cooling fluid is to be utilized, the interface to facility/platform cooling fluid should be considered, along with the impact on efficiency and device/system density and packing factor.