WASHINGTON, DC - Using a Department of Energy - funded coal-fired technology, a greenhouse in northeast Ohio is saving more than $1,000 a day in heating costs. The efficient fluidized-bed combustion unit provides an alternative to natural gas systems and, using locally available coal and limestone, surpasses state EPA standards for sulfur capture and stack emissions.
"The promise of the unit lies in its novel design," said Donald Bonk, a senior technical advisor for the National Energy Technology Laboratory (NETL), which manages the project for the Energy Department. "The fluidized-bed combustion system features flue-gas recirculation, replacing conventional, more expensive boiler tubes. By recycling the flue gas, the system better controls internal temperatures to burn fuel, reducing the formation of pollutants."
Not only is the system environmentally sound, but it eliminates the need for expensive external emission controls as well - two desirable features of the new coal-fired system. And while unit installation costs may appear high when compared with natural gas systems, capital expenses are quickly regained - within about 3 years - through low-cost operation and fuel efficiency.
The unit is installed at Cedar Lane Farms, a commercial wholesale greenhouse in Wooster, Ohio. According to Tom Machamer, the greenhouse owner, the system's operational efficiency and reliability are impressive.
"The system has been fully functional since 2003 and has shown a 96.9 percent reliability rate," said Machamer. "Under continuous computerized control, the unit easily generates hot water for heating two of the farm's five acres of greenhouses. On average, the system requires only two man-hours of labor a day to load coal and limestone and remove ash from the system. The system can also run on demand, shutting down when the greenhouses no longer need to be heated."
With the potential for application in small-scale institutions, light industry, and commercial buildings, the project has shown signs of commercial success. Schools, hospitals, food processing plants, apartment complexes, and shopping centers could use a system like this one and benefit from the savings.
The technology can also be applied on a larger scale or adjusted to meet specific needs. While Cedar Lane Farms requires only 9 million Btus per hour (2.6 megawatts) to heat all of its buildings, larger systems can be built to produce up to 40 million Btus per hour with relative cost savings. The unit can also be modified for steam generation or the co-generation of heat and power, depending on facility needs.
The technology behind the system began as bench-scale work in 1991 when the Department of Energy partnered with Ohio Agricultural Research and Development Center to conduct research on alternative fluidized-bed designs. With the Energy Department providing up to 80 percent of the initial funding, the project has moved from research and pilot tests to the successful commercial unit at Cedar Lane Farms. By 1999, the project received only 20 percent federal funding, with remaining sponsorship provided by the State of Ohio and private entities. Cedar Lane Farms will be handling and maintaining the unit independently by the end of 2005 and plans to use the system to heat the remaining three acres of greenhouses.
The project was funded under NETL's former Advanced Combustion Program, created to develop innovative, highly efficient solid-fuel combustion systems that are cost effective and environmentally acceptable.