TECHNOLOGY AREA(S): Ground/Sea Vehicles

ACQUISITION PROGRAM: PMS 320 Electric Ships Office

OBJECTIVE: Develop an innovative warm-to-cold high temperature superconducting power cable termination suitable for shipboard applications.

DESCRIPTION: The U.S. Navy is progressing toward increased electrification of ship systems and weapons requiring unprecedented levels of power distribution capabilities on ships. Electric propulsion motors are expected to demand 20-80MW per ship supported by multiple 10-40 MW generator sets. Additional high-power loads will include rail guns, lasers, electronic warfare systems, and high-power radar. These systems will be tied together through an integrated power system (IPS) that maximizes the utility and efficiency of installed power generation by routing power to loads on demand. A primary benefit of the IPS approach is an increase in overall power distribution density, electrical efficiency and fuel savings. Moving 10�s to 100�s of MW of power around a ship favors increased distribution voltages (greater than 450VAC and/or 6-18 KVDC) to minimize added cabling necessary to overcome the ampacity limits of traditional conductors. High Temperature Superconductors (HTS) are candidates for advanced conductor technology that can be used to increase the power distributed through a single lightweight cable without the necessity of going to higher voltage. Implementation of these technologies require HTS power cable termination suitable for shipboard applications. An additional benefit of a HTS cable system is the ability for co-axial or tri-axial cable designs that minimize externally emitted magnetic field thereby having no impact on ship magnetic signature. The compact cable termination will also enable center of gravity favorable power delivery to high elevation loads eliminating the negative weight impact using traditional copper conductors. Additionally, decoupling the cryogenic cooling system from the cable and termination would allow for additionally favorable placement of the heavier cryogenic system components lower in the ship.

HTS power cables have been successfully operated in several land-based demonstrations using liquid nitrogen as the cryogen. The primary benefit of HTS cables for in-grid land applications is the ability to utilize existing cableways, or right-of-way, originally intended for underground or overhead transmission cables to increase power distribution by 10. This is particularly useful in upgrading power distribution in cities with growing load demands where conventional approaches to expanded distribution is not feasible. While the HTS cable generally has an outer jacketing diameter in the range of 1.5 inches to 3 inches, the cable termination is usually several orders of magnitude larger. These terminations generally serve as the entry and exit point of the cryogen requisite to maintain the conductor�s superconducting state. Minimizing the physical size and weight of terrestrial HTS cable terminations has not been a focus of the community.� Existing terminations are unsuitable for the Navy shipboard environment since they impose a large footprint at each end of the cable.

The Navy has been developing superconducting cable technology using cryogenically cooled helium gas, which eliminates the logistic impact of handling a liquid cryogen and minimizes safety concerns related to the 700-time volumetric expansion of nitrogen from liquid to gas state. This gaseous helium cooling approach has been demonstrated in HTS degaussing cables as well as power cables. The cryogenic systems used in these cables have been optimized to provide gaseous helium at 50 K (-367�F) and up to 20 Bar (290 psi) charge pressure with mass flow rates up to 10 grams/sec.

Novel solutions are required to advance HTS cable technology through the development and testing of a compact cable termination to serve a wide range of naval power applications including shipboard power distribution and shore power. Proposed solutions should include flexibility to integrate with multiple HTS cable topologies including single and multiple-pole configuration of Conductor on Round Core cable (CORC�) or co-axial cable designs. The termination will enable the transition from the cryogenic superconducting cable to the ambient temperature environment and interface with conventional conductors or buss bar while also providing means for cryogen entry and exit. The termination should be scalable from 1kA-4kA, applicable for 450VAC and above and/or 12kVDC and above, for 2 MW to 100 MW of power while incorporating a McFee-based cryogenic current lead optimization approach. Proposed solutions shall include plans for verifying the design through testing within the Phase II effort. Cable termination concepts that include a compact termination, less than 6-in diameter by 12-in length at one end of the cable, and a requisite larger (24-inch diameter by 36-in) termination at the opposite end are acceptable under this topic. A successful termination product will enable the cost competitive acquisition of an affordable HTS system.

PHASE I: Develop a concept and demonstrate the economic, technical and manufacturing feasibility of a compact superconducting power cable termination design that meets the needs of the Navy as defined in the Description. Demonstrate the design and manufacturing concepts through modeling, analysis, and bench top experimentation where appropriate. Document the identification of the size, weight, and cryogenic thermal load vs current, along with ability and impact of scaling voltage and current ratings. Include, in the Phase I final report at a minimum, the technical and economic feasibility and the ability to complete more than one prototype termination iterations with the Phase II funding. The Phase I Option, if exercised, should include an initial detailed design and specifications to build a prototype with the Phase II effort.

PHASE II: Develop, fabricate, and test prototypes of compact HTS cable terminations of a quantity to fit within the scope of work and accomplish tasking. Perform testing activities that include demonstration and characterization of key parameters and objectives at the proposer�s facility or other suitable testing facility identified by the offeror. Design the compact cable terminations for rated voltage and current, integrated with a HTS cable, and test them using a gaseous helium cryogen. Test the terminations to demonstrate the ability to meet the design characteristics. Deliver the Phase II prototypes consisting of HTS cables and terminations to the Navy for further testing.� Submit the design and drawings of the tested superconducting compact cable termination prototypes to the Navy. In addition, submit to the Navy any updated designs, design changes, and related drawings that result from lessons learned discovered during prototype testing. Ensure that the final submitted design will pass Navy qualification testing (MIL-S-901D, MIL-STD-167-1, and others) once manufactured.

PHASE III DUAL USE APPLICATIONS: Support the Navy in transitioning the technology for Navy use. Perform market research, analysis, and identification of teaming opportunities with industry partners to establish production-level manufacturing capabilities and facilities that will produce and fully qualify a HTS cable and compact termination. Transition the compact superconducting cable termination to the Electric Ships Office for incorporation into shipboard power systems. Develop manufacturing plans to facilitate a smooth transition to the Navy.

This technology has potential high-value application in the commercial electric power industry, including the electric power transmission and distribution; and high-power-use industries (e.g., Data storage and Supercomputing centers). It is expected this technology will enable compact superconducting cables to serve high power loads without the traditional termination footprint requirement.

REFERENCES:

1. Zhang, Zhenyu.� "Superconducting Cables �Network Feasibility Study Work Package 1.�� Next Generation Networks, Western Power Distribution, Aug 19 2017. https://www.westernpower.co.uk/downloads/2402

2. PMS320 Electric Ships Office. �Naval Power Systems Technology Development Roadmap (NPS TDR).� https://www.navsea.navy.mil/Portals/103/Documents/Naval_Power_and_Energy_Systems_Technology_Development_Roadmap.pdf

3. van der Laan, D., Weiss, J.D., Kim, C.H., Graber, L. and Pamidi, S. "Development of CORC � cables for helium gas cooled power transmission and fault current limiting applications." Superconductor Science and Technology, vol. 31, no. 8, p. 085011, 2018.
http://iopscience.iop.org/article/10.1088/1361-6668/aacf6b/meta

4. Kephart, J.T., Fitzpatrick, B.K., Ferrara, P., Pyryt, M., Pienkos, J. and Golda, E.M. "High Temperature Superconducting Degaussing From Feasibility Study to Fleet Adoption." IEEE Transactions on Applied Superconductivity, Article vol. 21, no. 3, pp. 2229-2232, Jun 2011. https://ieeexplore.ieee.org/document/5672800

5. Bromberg, L., Michael, P.C., Minervini, J.V. and Miles, C. "Current Lead Optimization For Cryogenic Operation At Intermediate Temperatures." AIP Conference Proceedings, vol. 1218, no. 1, pp. 577-584, 2010.� https://aip.scitation.org/doi/10.1063/1.3422405.

KEYWORDS: High Temperature Superconducting Cable Termination; High Temperature Superconducting; Advanced Conductor; Power Distribution; Cryogenic Helium System; Cryocooler