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Sustainable Campus Initiative

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Workshop on E.O. 13514

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IT Sustainability

How can another way of boiling water save energy?

WHY BIOMASS-FUELED? Johnson Controls, Inc., first suggested a woodchip-fueled steam system, as part of its search for ways to save energy at ORNL. Once ORNL management showed interest, Johnson Controls conducted a detailed feasibility study before the biomass system was chosen. The biomass steam plant is the largest energy conservation measure in the Energy Saving Performance Contract (ESPC) with Johnson Controls. The woodchips will be supplied by nearby businesses. The change should reduce fossil fuel consumption by over 80% from the current system, and the gasification process will reduce greenhouse gas emissions. More information can be found in an ORNL Review article and a presentation on the project.	LOCATION ORNL’s biomass gasification boiler system will be built at the current steam plant site. The system will include the refurbished steam plant building and two new buildings, to be located behind the refurbished building. One new 10,000-square foot building will house the new $60-million super boiler system, and the other 14,000-square foot structure will handle the wood chips that fuel the system. The efficiency of the two newer existing gas-fueled boilers will be improved, and they will be retained to handle peak demand. The current renovated steam plant building will serve as the control center for ORNL utility operations and a visitor area for the new steam plant.	TECHNOLOGY Nexterra Energy Corporation is supplying the entire boiler system, from fuel handling to the exhaust stack. Wood chips, heated in a low-oxygen environment in one of the three gasifiers, produce synthesis gas, or “syngas,” a mixture of mostly carbon monoxide and hydrogen. This syngas is burned cleanly in an common oxidizer. The hot flue gas passes through a hot water boiler where it produces steam. Heat recovered from flue gas is used to preheat the boiler water, before the gas is released out the stack. A reducer unit and an electrostatic precipitator will be available to clean the flue gas before release, if necessary to meet emission goals. Click here to see a graphic of the process.

graphic of biomass steam plant

ORNL’s biomass steam plant, which produces gas from wood chips
to boil water, is under construction.

OPERATION System components, including the new boiler, are now arriving on the ORNL campus. A new water treatment process for the boiler water will be the first change. An additional temporary (gas/oil) boiler will be hooked to the steam system during construction and testing to ensure that peak demand can be met before the new system comes on line. Construction of the new steam plant should require about 30 months. The plant is expected to come on line in March 2011. Once the plant is operational, it will provide the base load steam for ORNL. At that time, 10–12 truckloads of wood chips will be delivered each day. ORNL is negotiating contracts for wood chips with companies within a 100-mile radius. The fuel will be unloaded and transferred to a storage building holding about a 3-day supply of chips to be fed to the gasifiers. Ash from the wood chips will be trucked to a landfill at Y-12.	R&D BENEFITS ORNL researchers have made suggestions to help improve some aspects of the steam plant, such as examining the biomass-feed augers and recommending better materials. Laboratory space is included in the steam plant building for related research. Long-term research may involve gasifier modeling and performance analysis, investigation of the possibility of fuel cells running on syngas, and other ideas related to conversion of syngas, flue gas, or other materials in the process. Potential research opportunities include such areas as fuel analysis, process metering and monitoring, and residual fuel analysis. Environmental scientists are investigating uses for the waste ash, including possible use as a soil additive.	F&O BENEFITS The construction of the biomass steam plant will be accompanied by the addition of a secondary steam plant with a high-efficiency fossil fuel boiler for the Melton Valley area. The secondary plant will enable ORNL to remove the long, high-pressure steam line from the main campus to that area. There will be additional savings from removing four inefficient old boilers, installed in 1948. The biomass steam plant is expected to save $4.5 million a year, a savings guaranteed by Johnson Controls under the ESPC. The conversion will help ORNL meet DOE’s goals for use of renewable energy, save water compared to the previous system, and reduce greenhouse gas emissions.

(Last updated: November 11, 2009.)