N121-060 TITLE: Efficient and Lightweight Cryogenic Thermal Energy Storage System

TECHNOLOGY AREAS: Ground/Sea Vehicles

ACQUISITION PROGRAM: LCS Program, PMS 501, ACAT 1

RESTRICTION ON PERFORMANCE BY FOREIGN CITIZENS (i.e., those holding non-U.S. Passports): This topic is "ITAR Restricted". The information and materials provided pursuant to or resulting from this topic are restricted under the International Traffic in Arms Regulations (ITAR), 22 CFR Parts 120 - 130, which control the export of defense-related material and services, including the export of sensitive technical data. Foreign Citizens may perform work under an award resulting from this topic only if they hold the "Permanent Resident Card", or are designated as "Protected Individuals" as defined by 8 U.S.C. 1324b(a)(3). If a proposal for this topic contains participation by a foreign citizen who is not in one of the above two categories, the proposal will be rejected.

OBJECTIVE: Develop a compact, efficient, light-weight cryogenic thermal energy storage system for use in naval superconducting systems applications.

DESCRIPTION: The Navy is developing several superconducting systems for use in future ships and submarines to reduce system weight, energy usage and installed volume. These systems, such as degaussing, propulsion motors, electrical generators and power distribution systems rely on the use of cryogenic helium gas for operation. Current Navy superconducting systems rely on the mass of the system itself as thermal energy storage. This works well for rotating machines where the thermal constants are very large; however, in cable applications such as degaussing and power distribution this poses a real problem. Superconductors require cryogenic temperatures in order to benefit from zero electrical losses during operation. If the cryogenic system were to lose power and cease to provide any cooling, the temperature of the superconducting material would rise, superconductivity would be lost, and the material could undergo a catastrophic event. Maintaining cryogenic temperatures is paramount to superconducting systems. Significant amounts of heat from 100-3000W in the 20-120K range need to be removed from these systems on a continuous basis. The current state of the art in cable systems uses large tanks of liquid nitrogen as backup systems in the event that active cryogenic cooling is lost. This is not feasible on a ship because of the requirement to vent the gas when the system warms up and to provide make-up gas to recharge the system. If a cryogenic energy thermal storage system could be developed to allow the superconducting systems to handle transient heat loads and more rapid cool down times, the overall system efficiency, size and weight could be decreased.

This topic seeks innovative approaches to the development of compact, low-weight, high-capacity, cryogenic, thermal energy storage that is compatible with helium gas cooling at a high pressure (up to 25 bar) and temperature ranges (20 - 120K). In addition, proposed cryogenic thermal energy storage concepts must be able to provide better weight to volume density than what is now commercially available with the use of liquid nitrogen. Proposed concepts should also be rugged in order to handle a shipboard environment. Proposed concepts should be sized to be scalable from 100W to 3000W for up to an hour over a wide range of temperatures from 20-120K to maximize potential use of this technology. Thermal energy storage solutions such as salts and phase changing solutions exist at higher operating temperatures but do not exist at cryogenic temperatures or may not be suitable for use in a naval environment.

PHASE I: Develop concepts for a novel cryogenic thermal energy system design able to operate with Navy cryogenic systems as defined above. Perform bench top experimentation, where applicable, as a means of demonstrating the feasibility of the identified concepts. Establish validation goals and metrics to analyze the feasibility of the proposed solution. Provide a Phase II development approach and schedule that contains discrete milestones for product development.

PHASE II: Develop, demonstrate and fabricate a prototype as identified in Phase I. In a laboratory environment, demonstrate that the prototype meets the performance goals established in Phase I. Verify final prototype operation in a representative laboratory environment and provide results. Develop a cost benefit analysis and a Phase III installation, testing, and validation plan.

PHASE III: Upon successful Phase II completion, the company will support the Navy in transitioning the technology to military and commercial cryogenic or superconducting applications. Working with government and industry, install onboard a selected Navy ship and conduct extended shipboard testing. The company shall support the Navy in tests and validations to certify and qualify the technology for Navy use.

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: A cryogenic thermal energy system may be of use in land based HTS power cables and power delivery applications. As land based HTS power cables transition from R&D projects to commercial installations, these thermal systems will save on system downtime should a catastrophic event occur and cause a system-wide outage.

REFERENCES:
1. B. Fitzpatrick, J. Kephart, E. M. Golda, "Characterization of Gaseous Helium Flow Cryogen in a Flexible Cryostat for Naval Applications of High Temperature Superconductors," IEEE Trans. App. Super., Vol. 17, No. 2, 2007.

2. American Superconductor, "High Temperature Superconductor Degaussing Coil System," www.amsc.com, 2010.

3. R. Kniep, H. Klein, and P. Kroschell, "Hydrated Mg(NO3)3/NH4NO3 Reversible Phase Change Compositions," Patent Application 244785, September 1994.

KEYWORDS: Cryogenics; thermal energy storage; degaussing; superconductors; high temperature superconductors; HTS

** TOPIC AUTHOR (TPOC) **

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