TECHNOLOGY AREAS: Ground/Sea Vehicles

ACQUISITION PROGRAM: PMS 320, Electric Ship Office

OBJECTIVE: Explore the development of innovative approaches to enable compact, durable, engine waste heat recovery, power generation module designs suitable for naval shipboard application.

DESCRIPTION: Typical gas turbine engines are less than 35% thermally efficient at full power, and significantly less at partial power. Although diesel engine efficiency is more uniform across its operating power range, thermal efficiency typically does not exceed 45%. The engine exhaust stream is the primary pathway of engine waste heat, see Table 1. Recovering useful energy, in the form of electrical power, alternative heating and cooling, from engine exhaust waste heat would directly reduce system fuel consumption, increase available electric power and improve overall system efficiency by augmenting the power produced by the prime mover and enabling it to operate at a lower net power with lower net fuel consumption. Industrial gas turbines have achieved efficiencies�up to 60%�when waste heat from the gas turbine is recovered by a heat recovery system in a combined cycle configuration. Identification and development of a viable shipboard waste heat recovery system in this effort will provide reduced ship service electric power fuel consumption.

Table 1: Typical Marine Gas Turbines

Although waste heat recovery systems are commonly used in industrial power generation, the highly transient operation of U. S. Navy engines introduce significant technical challenges to heat exchanger durability, caused by the resultant high thermo-mechanical stresses (fatigue and material failure) as per Table 1, and shipboard space constraints may limit the applicability of commercially available systems. Past U.S. Navy efforts, utilizing steam-based systems, ref (1) and (2), have been conducted, but the additional complexity and maintenance intensive nature of steam systems represent a major life cycle cost risk. Consequently, only non-aqueous solutions shall be considered for this effort.

This topic seeks to explore innovative, affordable, advanced concepts and technologies to develop compact, durable waste heat recovery systems for application to naval ships. Primary technical risks to be addressed by the offerors include (a) high thermo-mechanical stresses on the heat exchanger which may result in high rate of failure, (b) high engine back pressure (exhaust losses 20") which may reduce prime mover power capability, and (c) system integration. The proposed system should enable a goal of 20% reduction in fuel consumption, for a given power requirement, compared to baseline gas turbine fuel consumption (available upon request) and shall not impose any limitations on engine operations. Attention shall be paid to solutions that minimize weight as well as the overall footprint specified earlier, with emphasis on modularity and scalability. A key challenge is going to be identifying and overcoming material fatigue based on high temperature, high flow exhaust gases in the range of (800�F � 1200�F), coupled with limited footprint constraints of the ship.

PHASE I: Demonstrate the feasibility of innovative, affordable, advanced concepts and technologies to develop compact, durable waste heat recovery systems for application to naval ships. Develop a design discussing the salient features of the performance as well as the physical and functional characteristics of the proposed system(s). Establish performance goals and metrics to analyze the feasibility of the proposed solution. Outline a notional post-Phase I plan that contains development schedule, tests and evaluations, long lead, discrete product development milestones for verifying performance and suitability and other events as required to reach production.

PHASE II: Develop, fabricate, install and demonstrate a full scale prototype of the module as identified in Phase I. In a laboratory environment, demonstrate that the prototype meets the performance goals established in Phase I. Perform all analyses and effort required to update all Phase I products to reflect the Phase II design. Develop a Phase III installation, testing, and validation plan.

PHASE III: Working with Government and industry, conduct detail design and fabrication of shipboard module to be provided to Navy for transition into advanced naval power systems demonstrations and tactical design development programs. Conduct extended testing to verify performance.

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: Waste heat recovery systems are featured in commercial industrial applications. Advances in waste heat recovery for naval applications will provide enhanced capability directly applicable to commercial and marine applications, resulting in improved performance, higher reliability and increased durability.

REFERENCES:
1. T.P Mastronarde, "Energy Conservation Utilizing Waste Heat Boilers, The Challenge, Problems and Solutions", Naval Engineers Journal (1982)

2. Bureau of Energy Efficiency. (2009, December 30). Waste Heat Recovery. Retrieved from website: http://www.emea.org/Guide%20Books/book2/2.8%20Waste%20Heat%20Recovery.pdf

3. MIL-STD-1399 Interface Standards for Shipboard Systems, Section 300 Electrical Power, Alternating Current

4. Doerry, Norbert "Next Generation Integrated Power System (NGIPS) Technology Development Roadmap", Naval Sea Systems Command, Ser 05D/349, 30 Nov 2007.

KEYWORDS: engine exhaust; waste heat recovery; heat exchanger; Rankine cycle; recuperate; gas turbine

** TOPIC AUTHOR (TPOC) **

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