How Would Wood Biomass Heat Work in Haines

Part III in a Series about Biomass Heat for Haines

Boiler Building for the Craig Schools

At our farm in the Ozarks my father was always good-naturedly rebuking my mother for keeping the house too hot and always throwing another chunk of wood in the stove. He would quip to me, “Your mother burns wood like it grows on trees!”

I would snicker at that remark but the reality of it was we, on the farm, were fairly energy independent. Because our property was large enough to have timberland and my father was conscious of good forestry, our heating supply was sustainable right there on the farm. My mother could keep the house as warm as she wanted and we did not even pay attention to oil prices. Our trees were a renewable energy source.

Wood Chip Bin at Craig Boiler

It is exciting to think that Haines that can do the same thing with heat utilizing hydro, wood and other renewable energy right here in the Borough. In the two previous articles I discussed the abundant wood supply and examined the issue of air pollution from biomass heat. But the question remains in the minds of many as to how such a system would work to heat multiple, large, public buildings with wood?

Misconceptions abound concerning wood heat. It is tempting to visualize someone having to throw large cordwood chunks into a massive boiler many times a day to keep the heat up. Such labor-intensive operations are not viewed with favor.

Although there are many different types of systems, the concept is simple. A large boiler is fed woody biomass, usually in the form of wood chips, where it is burned cleanly in several stages to heat water. Water is circulated underground to multiple buildings, usually to tap into their existing hydronic heating systems.

In the Haines proposal, the school and votech buildings, library, administration office and swimming pool would be connected to a centrally located boiler building. Insulated piping would deliver the hot water where it overrides the existing heating plants in each building. The water is returned in a loop to the boiler for re-heating.

Biomass wood heat can be provided in the form of cordwood (what you use in your woodstove), pellets, or chips. For large, district heating systems, wood chips have been found to be the least expensive. However, that may change as more and more pellet manufacturing facilities are coming on line in the Northwest including some here in Southeast Alaska.

Chip Tech Boiler that heats Craig Schools

For the sake of example, let us use the wood chip model since there is a current history of that in Alaska. The schools in Tok and Delta Junction are currently installing such systems and Craig has been using one for several years. Tok and Delta Junction will be utilizing the spruce-budworm killed trees as their primary wood supply for chips and Craig utilizes wood waste from the Vikings Sawmill.

In the Craig example, a dump truck brings chips to the boiler site twice a week where they are dumped in a concrete bin. A grate across the bottom of this bin allows heat from the adjacent boiler room to be blown under the chips to assist in drying. Chips contain about 70% moisture content when they are first added but are dried to 20-40% by the time they make it to the bottom where the auger automatically feeds them into the burner.

The heat from the boiler heats the hot water through heat exchangers where insulated underground pipe carries it to the school buildings. In the Craig example, two large school buildings and the community swimming pool are heated by this hot water before the loop returns it to the boiler. The system is completely automatic. The buildings retain their old heating systems for use in the summer when the boiler is shut down or for back up for boiler maintenance.

We are waiting any day the arrival of a design report for a Haines biomass heating proposal being prepared by CE2 Engineering from Anchorage. Using energy grant funds, CE2 was awarded a conceptual design contract to design a central biomass heating facility for the downtown public buildings. This design should be at what grant writers call the 35% design phase where the proposal could then be presented to the legislature for a construction grant.

Although wood chip heating has been around for a long time, the technology is constantly changing and we are unsure what type of system CE2 will recommend. Unlike other communities where wood chips are being used or proposed, Haines does not have a current supply of waste wood or chippers in operation and that will have to be addressed. Will wood pellets or other forms of woody biomass be considered? Will they propose a system large enough to expand the central heat to other buildings in the downtown area? We will have to wait and see. But it is exciting to think that our heat in downtown Haines might indeed, grow on trees.

Photos and Craig information courtesy of Karen Petersen, University of Alaska Fairbanks – Cooperative Extension Service.

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