Alaska federal building warms to GSA requirements with wood pellet boiler
The GSA chose the Ketchikan project to demonstrate state-of-the-art wood pellet boiler technology that meets these goals. This project also is aligned with an October 2009 Presidential Executive Order that mandated government-owned buildings to increase renewable energy use and reduce greenhouse gas emissions. It is the first GSA building to install a commercial-scale wood pellet boiler system.
INTO THE FUTURE
An ACT Bioenergy 1.0 MMBtuh pellet boiler was selected for the project by RSA Engineering of Anchorage, AK. Warren Williams of RSA stated, “The ACT boiler which is manufactured in Schenectady, NY was one of the only boilers made in the U.S. that could meet the GSA’s criteria for efficiency, low-emissions, and fully-automated operation.”
A biomass boiler, along with a BAS to manage it, saves the GSA $10,000 a year in operating costs at the Ketchikan Federal Building.
The ACT biomass boiler design includes automatic ignition, firing-rate modulation, and automatic ash cleaning. The boiler monitors oxygen levels and pressures in the combustion chamber and the PLC controller adjusts airflows to achieve complete and clean gasification of the wood fuel. Regular automated cleaning brushes in the heat exchanger tubes ensure that the boiler continually operates at high efficiency. Ash is typically removed from the collection in the boiler every two to three weeks. Also, it is anticipated that with the new biomass boiler, the overall system thermal efficiency will increase from 58% to 78%.
Although the ACT boiler can also burn wood chips, pellets were chosen to minimize fuel handling and storage requirements on site. Wood pellets, which are made from compressed sawdust, are approximately three times denser than wood chips and therefore require much less storage space. Wood pellets are typically made from sawmill byproducts, and are considered a sustainable, renewable fuel that can be produced locally instead of importing heating oil.
Furthermore, since the wood pellets are between 30% to 50% cheaper than heating oil, the project will reduce building operating costs by at least $10,000/yr based on the replacement of an estimated 9,000 gal/yr of heating oil.
The wood pellets are stored in a 20-ft high, 11-ft dia silo that stores that holds about 24 tons of pellets. The silo is sized to be refilled an average of five times per year via bulk delivery with an auger truck. Currently, the silo is refilled with “super sack” tote bags that each hold a ton of pellets and are lifted and dumped into the silo, but it is expected that bulk delivery with an auger truck will start soon supply the growing bulk pellet market in Southeast Alaska. Once the pellets are in the silo, all the fuel feeding for the boiler is automatically controlled and the boiler modulates similarly to a fossil fuel boiler. The upgrades related to the pellet boiler represented about 13% of the total project cost.
A Burnham MPC-8 1.0 MMBtuh oil boiler manufactured in Lancaster, PA was also installed in the building to provide 100% redundancy in the case of any disruptions in pellet boiler operation. The integrated operation of the two boilers is achieved through a Siemens APOGEE® BAS, which modulates the boiler supply temperature with a 4-20mA signal in response to outdoor air temperature.
Ron Blazer, building management specialist for the GSA, reported that after four months of operation, the pellet boiler was supplying virtually all of the building’s heating load and the building tenants have noticed an increase in comfort with the new biomass heating system.”
The project was overseen by Southwest Construction, a small, woman-owned business with operations in Anchorage, AK. Dave Trudeau, vice president for Schmolck Mechanical which installed the system said, “Although this was our first biomass project, the system installation was straightforward and comparable to a fossil fuel boiler. Based on this experience, we see great potential for additional biomass boiler in Alaska where current costs of heating oil can exceed $4/gal.”