Wood pellet boilers should be considered at all hot-water heated federal facilities where natural gas is unavailable, particularly in northern regions, according to the U.S. General Services Administration. The GSA’s Green Proving Ground just released a study of the retrofit done at the Ketchikan Federal Building in Ketchikan, Alaska, that installed a state-of-the-art pellet-fired biomass boiler.
GPG commissioned researchers from the National Renewable Energy Laboratory to evaluate the efficiency, cost-effectiveness, and operational functionality of the 1-million Btu boiler. NREL gauged the technology’s deployment potential by combining information from GSA’s Energy Usage and Analysis System with independent research to locate wood-pellet biomass sources, estimate delivered costs, and identify additional candidate facilities. After one full year of boiler operation, researchers performed a measurement and verification assessment over the course of one day in January 2012 to ascertain biomass boiler operational efficiency.
Because weather conditions were mild on that day and the boiler is oversized, it was operating at only 45 percent of load, but still maintained 85 percent efficiency, the report said. Payback for Ketchikan, in which the retrofit included the replacement of the entire legacy heating system, is estimated at 30 years. In part, that is due to the oversizing of the boiler, the report said. “Over the course of a year, the boiler installed at Ketchikan is capable of generating 8,760 million Btu but estimated use in 2011 was 1,150 million Btu, or 13 percent of full capacity. Under more favorable conditions, including but not limited to appropriate system sizing, simple payback can be less than five years.” A table in the report reported the payback periods for various pellet prices and differently sized systems. Paybacks are less than three years at prices between $200 and $250 per ton for systems ranging from 1 million Btu per hour to 4 million Btu per hour.
The report listed several benefits of pellet boilers, summarizing them as having high operational functionality and low operating and maintenance costs. Of the more than 1,500 GSA-owned buildings across the U.S., researchers identified approximately 150 as potential candidates for biomass heating. “Wood-pellet- fired biomass boilers should be considered at all hot-water-heated facilities where natural gas is unavailable. Deployment should target facilities that have an extended heating season and where pellet fuel is available within 50 miles.”
The full report can be found on the GSA website here >>