Commercial Scale Wood Pellet Fired Boiler - An Emerging Energy Technology Grant Project
In 2010, the Sealaska Corporation (Sealaska), the regional native corporation for Southeast Alaska, converted the heating system of its headquarters in Juneau from an oil-fired boiler to a wood pellet-fired boiler. Wood pellet-fired boilers have been used effectively for over 30 years in many different countries and environments but have had limited application in Alaska, and no commercial-scale project had been installed yet. Sealaska’s overall project goal was to demonstrate that biomass heat can be feasible and is a cost-effective option for larger commercial, industrial and municipal buildings. This project also has the potential to influence the demand for a densified wood product made of Southeast Alaska’s waste wood fiber.
Sealaska Plaza, the headquarters for Sealaska, is a four-story office building located in Juneau. Prior to 2010, the main heating system was an oil-fired boiler system that used over 30,000 gallons of heating oil annually. Interest in a wood pellet boiler system retrofit stemmed from several factors, including the need for a major system upgrade/replacement due to operational life, the high cost of heating oil, and interest in developing sustainable economics for Southeast Alaska. Leadership for the project came from a Sealaska Board of Directors green initiative to introduce renewable energy into Sealaska and eliminate the use of imported fuel oil for heating. Sealaska and applied for funding through the Denali Commission EETG program for this project with the stated objectives to:
- Demonstrate that wood heat can be cost-effective and feasible for large commercial, industrial, and municipal buildings.
- Investigate the potential creation of demand for Southeast Alaska second-growth wood fiber.
Project activities formally commenced in February of 2010 with the finalization of system design and engineering plans and the ordering of equipment and supplies. Installation commenced in September 2010, with the removal of the old oil-fired boiler system and the pouring of concrete pads for the new boiler system.
Originally, the oil-fired system was to remain as a backup or supplemental heating system. Given the Sealaska green initiative however, the oil-fired system was completely removed and a new electric heating system was installed as backup, resulting in a building that was completely powered by renewable energy. The new system was installed in the existing boiler room of Sealaska Plaza, which posed some typical design and installation challenges since the project needed to conform to the dimensions of the existing space and electrical, mechanical, and plumbing infrastructure. It was reported that the installation was, however, “very easy and not unlike doing a conventional oil boiler replacement.”
Given the limitations of the existing space and the location of Sealaska Plaza in a downtown, urban environment, pellet storage was another critical consideration during the design and planning of the system. The resulting design was a pellet silo outside the building near the existing boiler room and adjacent to Main Street. The proximity to the street allowed for truck access and delivery while the proximity to the existing boiler room allowed for automated auger transport of pellets from the silo to the pellet boiler.
The system commenced operation on November 23, 2010, and the electric boiler system was installed in December; system commissioning was finalized in January 2011.
As a demonstration of wood pellet boiler technology, the Sealaska project in Juneau has been very successful. Since operations commenced in November 2010, Sealaska has held a number of public and private tours of the system and has given many public presentations discussing its experience in designing and operating the system. The success of the project can be directly attributed to the implementation of several commercial-scale wood pellet businesses in Southeast Alaska. As a result of the Sealaska demonstration project, many other communities have decided to move from fuel oil to wood pellets. Sealaska has been available for feedback and assistance in the review process for designing, constructing and managing boiler systems in other community buildings.
The following are additional findings and lessons learned through this project:
- Premium pellets are more expensive than lower-quality pellets, but have less ash content; the wood material, as well as the manufacturing process, accounts for the difference between premium quality and lower-quality pellets. A high-quality pellet will likely be more durable during shipping and will be less likely to create sawdust than a lower-quality pellet. Silos with less than premium-quality pellets are advised to draw down the supply at least once a year to remove sawdust. Sealaska found that its supply of Pacific Northwest pellets rarely produced sawdust and drawdown was not necessary.
- Biomass boilers require considerable expertise in their design, selection, and installation. The same practices used for fossil fuel boilers may not be applicable with biomass boilers. Thus it is essential to bring in a team of professionals with strong biomass boiler experience to help ensure that the system installed has the fewest number of ‘teething pains’ possible. In addition, availability beyond the installation and commissioning of the system.
- Pellet production is reliant on the availability of feedstock and market demand, and unlike fuel oil distribution, it may not be consistently reliable. There are only 140 pellet mills across the United States and many of those are small manufacturers. The first main pellet supplier to Sealaska won an account for a large retail store, and it no longer wanted to ship smaller amounts to Alaska. Finding a reliable vendor of high-quality pellets is essential if a large-scale pellet boiler is to be installed.
- Some pellet boiler systems can burn both pellets and woodchips. In some situations, it may make more sense economically and practically to use locally available woodchips. One drawback to woodchips is that they are not as consistently sized as pellets, and they may also contain more moisture. But the delivered cost of premium pellets is much higher than that of woodchips. The efficiency may be decreased by the moisture, but it is a consideration for communities that do not have a local pellet mill or access to a pellet vendor such as Sealaska.
- One of the design lessons with the Sealaska pellet boiler was fitting a new boiler system into an existing building. Industrial-sized boilers are generally installed as part of a new building project, and the building designs can be adjusted to account for the boiler size and piping. The boilers can be fit into existing space, although this can be a challenge when working around the boiler and when adequate space is needed for safety.
Project data reflects unexpected system performance during peak ambient (summer) temperatures, which warrants further investigation by system operators. Appropriate sizing of a wood pellet system is of particular importance in Southeast Alaska and requires further detailed data collection and analysis to inform future system sizing and optimization.
In addition, the economics of a project outside the context of a demonstration project still need to be proved. A reduction in project capital costs is critical, as is reducing the cost of wood pellets, which, presumably, can only be addressed through an increase in regional wood pellet demand. Sealaska has had success in procuring a steady supply of premium pellets from the Pacific Northwest, and it will continue to act as a vendor to supply Southeast with pellets and supplement local production from mills. It has been reported that since the Sealaska project, a flood of new boilers have come onto the North American market, primarily from established European companies. Price competition is evident in this growing arena, and may be reflected in a drop in project capital costs. In addition, it has been reported that there may be a significant trend in pellet price reduction for the Pacific Northwest, although the price impact for Juneau and other Southeast Alaska communities is unknown at this time.
Photo 1: Sealaska Wood Pellet Silo and Project Manager, Nathan Soboleff. Courtesy of Kirk Hardcastle.
Photo 2: Sealaska Wood Pellet Boiler in Operation. Courtesy of Jason Meyer, ACEP.
Photo 3: Sealaska Wood Pellet Boiler System. Courtesy of Kirk Hardcastle.