TECHNOLOGY AREA(S): Ground/Sea Vehicles

ACQUISITION PROGRAM: PMS 320 (Electric Ships Office) and the Power and Energy FNC Pillar

OBJECTIVE: Develop innovative technology improvements to propulsion and power generation prime movers through increased power density and improved fuel efficiency.

DESCRIPTION: Some current commercial applications perform waste heat recovery primarily from the exhaust gases of the prime movers. Typical gas turbine exhaust temperatures are 800° F and higher. Diesel engine exhaust temperatures can be 700° F and higher. Industrial gas turbines have achieved efficiencies up to 60% when waste heat from the gas turbine is recovered in a combined cycle configuration. Although waste heat recovery systems are commonly used in industrial power generation, the highly transient operation of U.S. Navy engines and the stringent requirements applied to the gas exhaust introduce significant technical challenges to heat exchanger durability, caused by the resultant high thermo-mechanical stresses (fatigue and material failure). As such, this STTR topic seeks methods to recover energy from sources as low as 200° F and below (e.g., jacket water) so that heat exchangers do not experience thermal cycling challenges.

The Navy seeks to develop innovative technology improvements to propulsion and power generation prime movers (which convert fuel to rotational energy) through increased power density and improved fuel efficiency. Typical gas turbine engines are less than 35% thermally efficient at full power, and significantly less efficient at partial power. Diesel engines have better partial power efficiency, but thermal efficiency generally does not exceed 45%, and power density and longevity are lower. Currently these engines are very inefficient when operating at reduced power levels. Research and development is needed to determine if there is a feasible concept that is power dense and can achieve an overall 10% gain in thermal efficiency.

By utilizing technology that will increase the power density and generation efficiency as well as enabling an Integrated Power and Energy System (IPES) on smaller surface combatants, these smaller ship classes will be better able to implement high power/energy weapons and sensors, such as larger directed energy weapons, sensors with further range and fidelity, and higher speed operations.

Recovering useful energy in the form of electrical power or alternative heating and cooling applications from these engines over varied operational demands would directly reduce system fuel consumption, increase available electric power, and improve overall system efficiency. Energy recovery will also help to meet the Navy’s need for reliable redundant power. Using recovered energy to augment the power produced by the prime mover will enable system operation at a lower net power with lower net fuel consumption. Other examples of uses for recovered energy may include, but are not limited to, powering small unique loads, supplementing refrigeration systems, precooling chilled water, or charging energy storage systems.

As an example, the Navy Landing Platform/Dock (LPD) class amphibious ships each have five Ship Service Diesel Generator Sets (SSDGs) rated at 2,500 KW of electrical output power. Proposals should incorporate technologies that will increase the efficiency of an electric plant like what is on the LPD class by providing at least 150KW of additional power output and an overall system thermal efficiency of greater than 55%.

The proposer will develop and test a reduced scale technology demonstrator in the 50-100 KW range that can provide the target performance metrics, scalable to 2500 KW. Solutions should be able to meet future higher power demands of directed energy weapons by incorporating Supercritical carbon-dioxide (sCO2) as the working medium or an alternative working medium that can achieve similar results. All proposed solutions will be analyzed for their impact on engine design and energy heat recovery capability.  The technologies must not impose limitations on engine operations and must not impede the airflow of the intakes or uptakes. In addition, the installation of the new technology should not increase the combined generator weight and volume by more than 6% (threshold) or 4% (objective). Emphasis will be placed on modularity and scalability to higher power applications. The proposer must also address shock and vibration requirements covered under MIL-S-901 [Ref 6] and MIL-STD-167 [Ref 7].

PHASE I: Develop a conceptual design for a power dense waste heat recovery system for application to naval ships. Discuss the salient features of the performance as well as the physical and functional characteristics of the proposed system(s). Using best practices, develop thermodynamic models to predict system performance and provide justification for the model assumptions.  Use the results from the modeling study to assess the ability of the proposed solution to meet the performance goals and metrics. Develop a Phase II plan. The Phase I Option, if exercised, will outline the specifications and capabilities to build the prototype in Phase II.

PHASE II: Develop, fabricate, deliver, and demonstrate a reduced scale prototype of the module as identified in the Description with a power level of at least 10 kW. Demonstrate the same technology that can support full-scale operation for shipboard power generation. In a laboratory environment, demonstrate through test and validation that the prototype meets the performance goals established in Phase I. Perform all analyses and effort required to refine the prototype into a useful technology for the Navy. Provide detailed drawings and specifications, document the final product in a drawing package, and develop a Phase III installation plan.

PHASE III DUAL USE APPLICATIONS: Working with the Government, conduct detailed design and fabrication of a shipboard module to provide to the Navy for qualification and other testing as required by the fleet technical authorities in preparation for a shipboard installation. Transition opportunities for this technology include commercial ship and offshore systems that could benefit from reduced volume of mechanical equipment and increased system efficiencies.

REFERENCES:

1. “The 2015 Naval Power and Energy Systems Technology Development Roadmap.” http://www.navsea.navy.mil/Portals/103/Documents/Naval_Power_and_Energy_Systems_Technology_Development_Roadmap.pdf

2. Markle, Stephen P., PE “Surface Navy Electrical Leap Forward.” Sea-Air-Space Exposition Presentation 1.1. 03 April 2017. http://www.navsea.navy.mil/Portals/103/Documents/Exhibits/SAS2017/Markle-ElectricShips.pdf?ver=2017-04-03-155727-897

3. “Waste Heat Recovery: Technology and Opportunities in U. S. Industry.” BCS, Incorporated, U.S. Department of Energy, Industrial Technologies Program, March 2008. https://www1.eere.energy.gov/manufacturing/intensiveprocesses/pdfs/waste_heat_recovery.pdf

4. Gibson, S., Young, D., and Bandhauer, T. M. “Technoeconomic Optimization of Turbocompression Cooling Systems.” Paper IMECE2017-70934, ASME International Mechanical Engineering Congress and Exposition, Tampa, FL, 2017. http://proceedings.asmedigitalcollection.asme.org/proceeding.aspx?articleid=2669116

5. Yuksek, Errol L. and Mirmobin, Parsa. “Waste Heat Utilization Of Main Propulsion Engine Jacket Water In Marine Application.” ASME 2015, 3rd International Seminar on ORC Power Systems, Brussels, Belgium, October 2015. https://www.researchgate.net/publication/301301713_WASTE_HEAT_UTILIZATION_OF_MAIN_PROPULSION_ENGINE_JACKET_WATER_IN_MARINE_APPLICATION

6. MIL-DTL-901E, Detail Specification, Shock Tests, H.I. (High-Impact) Shipboard Machinery, Equipment, and Systems, Requirements for. http://quicksearch.dla.mil/qsDocDetails.aspx?ident_number=2640

7. MIL-STD-167, Fiber Optic Cabling Systems Requirements and Measurements. http://quicksearch.dla.mil/qsDocDetails.aspx?ident_number=277227

KEYWORDS: Supercritical CO2; Heat Exchanger; Energy Recovery in Electrical Generators; Waste Heat Recovery; Thermal Efficiency; Jacket Water