Conversion of Low Quality Waste Heat to Electric Power with Small Scale Organic Rankine Cycle (ORC) Engine/Generator Technology

EW-201251

Objective

The U.S. Department of Defense (DoD) is the nation's largest energy consumer, representing about 80% of federal sector energy consumption. One of the largest sources of wasted energy is in the form of waste heat--hot exhausts, thermal management systems associated with engine and other electric generator systems, waste heat from steam or heat distribution, waste heat from boiler exhausts, and heat produced by renewable energy systems (biogas generators, solar thermal, biomass, and others). The Organic Rankine Cycle (ORC) engine-generator can convert low quality waste heat directly into electrical power, providing significant energy cost savings, reducing emissions per unit of energy, improving energy security via on-site energy production, and resulting in increased production of renewable energy. Until recently, however, small-scale ORC generators that utilize low-quality waste heat were not widely available. The objectives of this project are to install and independently evaluate the performance, economics, and operational impacts of a 50-65 kW ORC system operating on waste heat from a diesel-fueled engine generator and to develop guidelines for use of the ORC in a variety of applications throughout DoD.

Back to Top

Technology Description

The basic components of ORC generators are: (1) a heat exchange loop to transfer heat from the waste heat source to the ORC; (2) an evaporator where the ORC working fluid is boiled and expanded using the waste heat, creating a pressurized hot vapor stream; (3) a device that allows gas expansion and converts the energy into rotational work (turbine or positive displacement twin screw); (4) an electric power generator connected to the turbine or other rotating machinery; and (5) a liquid condenser and working fluid heat management system. The ORC selected for this demonstration, ElectraTherm's Green Machine GM-4000, produces 30-65 kW of emissions-free power with:

  • Nontoxic, nonflammable working fluids
  • A patented, twin-screw expander instead of a traditional turbine
  • Operation on hot water loop at 190-240°F
  • Two patented components: (1) innovative twin screw expander profile and (2) process lubrication--lubricant suspension in working fluid, resulting in no oil pump, gear box, or oil changes
  • Power variability, i.e., generators turn down capability to produce 30-65 kW.

Demonstrations will be conducted at Naval Auxiliary Landing Field, San Clemente Island, California, and at Port Hueneme, California.

Back to Top

Benefits

For potential applications such as remote power generation facilities with diesel-fueled engine generators greater than 1 MW and high power costs ($0.50/kWh), the payback period for implementation of an ORC system can be as little as 1.5 years. Estimated lifetime savings of more than $3-5 million are predicted. For other applications, such as waste heat utilization in central steam plants or combined heat and power systems, the economic impact can be calculated as a change in the electricity cost from the CHP system. An analysis of one example site provides a reduction in the cost of electricity from $0.0775/kWh to $0.0631/kWh, providing an estimated 7-year payback period potential. The ORC system does not produce emissions as a result of power generation and provides greenhouse gas and other pollutant emission reductions associated with offset of standard fossil fuel-based power generation systems. For one 1.1 MW diesel genset, carbon dioxide reductions of 509 tpy are predicted. (Anticipated Project Completion - 2014)

Back to Top

Points of Contact

Principal Investigator

Mr. Tim Hansen

Southern Research Institute

Phone: 919-282-1052

Fax: 919-282-1060

Program Manager

Energy and Water

SERDP and ESTCP

Document Types

  • Fact Sheet - Brief project summary with links to related documents and points of contact.
  • Final Report - Comprehensive report for every completed SERDP and ESTCP project that contains all technical results.
  • Cost & Performance Report - Overview of ESTCP demonstration activities, results, and conclusions, standardized to facilitate implementation decisions.
  • Technical Report - Additional interim reports, laboratory reports, demonstration reports, and technology survey reports.
  • Guidance - Instructional information on technical topics such as protocols and user’s guides.
  • Workshop Report - Summary of workshop discussion and findings.
  • Multimedia - On demand videos, animations, and webcasts highlighting featured initiatives or technologies.
  • Model/Software - Computer programs and applications available for download.
  • Database - Digitally organized collection of data available to search and access.