HomeMy WebLinkAboutThorneBay School Wood Fired Boiler Biomass Case Study 02-2016-BIOThorne Bay, Alaska
Wood-fired boiler fosters local economy and education
Quick Facts
Total Project Costs: $516,686
Funding: Renewable Energy Grant Fund: $414,686
Local Funds: $102,000
Capital Costs
Design: $63,510
Construction: $453,176
Equipment
Make/Model: (2) Garn WHS 2000
Output: 325,000 btu/hr each
Thermal Storage: 1,830 gallons each
Fuel Oil Offset
Estimated annual: 17,500 gallons
Actual annual: 15,000 gallons
Fuel Savings
Estimated annual: $39,450
Actual annual: $36,000
Benefit/Cost Ratio: 3.18
Jobs Created: 6 part-time
Thorne Bay School Wood-Fired Boiler
Project Overview
In partnerhsip with the Alaska Energy Authority
(AEA), the Southeast Island School District designed
and constructed a cordwood boiler system for the
Thorne Bay School. The system was integrated with
the existing hydronic heating system in the school and
later expanded to heat a greenhouse. By using cord-
wood as a heating fuel, the school district has created
local jobs and started to develop a cordwood economy
on Prince of Wales Island.
Objectives
The objective of this project was to reduce the cost
of heating for the Thorne Bay School by using a local
wood fuel. A secondary objective of the project was to
integrate forest products into the school curriculum.
Product Selection
The GarnPAC is a factory designed “boiler in a box”
developed to reduce the cost and complexity of con-
struction in rural Alaska. This skid-mounted connex
can be placed on a gravel pad and only requires piping
and electrical connections on site. The Garn boilers
are third party certified for their emission levels and
are selected for the simplicity of operation and main-
tenance. Each boiler unit has about 2,000 gallons of
thermal storage, resulting in very efficient combus-
tion.
Economic Feasibility
The system became operational in 2013. In 2014, it
provided 1,633 MMBtu of thermal energy and dis-
placed 15,000 gallons of fuel oil. This displacement
saved Thorne Bay School $36,000. Over its 20 year
projected life span, the project has a calculated bene-
fit/cost ratio of 3.18.
Fuel and Storage Boiler storage facility, photo courtesy of Jonathan Fitzpatrick.
Fuel and Storage
The school is located in the heart of the Tongass Na-
tional Forest, the largest national forest in the United
States. Wood is supplied by local sawmills and small
local firewood cutters. Once the cordwood is pur-
chased, students are paid to stack the wood in a storage
building. Wood is stored for at least a year to ensure
that the moisture is less than 20 percent. Burning
wood with moisture content greater than 20 percent is
less efficient and creates more emissions.
Learning Experiences/Challenges
The Garn boiler systems operate most effectively at a
temperature range of 140 to 180 degrees F. The hy-
dronic system in the school was designed to operate
at the upper end of this range. On the coldest days,
the Garn system is unable to fully meet the school’s
heating demand. Additional heating registers in the
school and added wood boiler capacity will solve this
problem.
Initial design of the integration of heating systems
allowed heat to flow from the oil boiler to the biomass
boiler when the biomass system was not in use. This
wasted expensive fuel oil and was remedied with small
changes to the piping and controls.
The concept of this prototype portable boiler in a box
was very successful at simplifying the installation. The
next step in its development is to “value engineer” the
unit to reduce its cost, currently $125,000 per unit.
Community Benefits
With money saved on displaced fuel oil the schoiol
district built a greenhouse that is heated using the bio-
mass system. Students learn science, math, business,
and horticulture; they also grow fresh vegetables for
the cafeteria and to sell in Thirne Bay and meighboring
Communities.
The biomass boilers have become an integral part of
education at Thorne Bay School. Students are hired to
stoke the boilers between their classes and after school.
and they designed and built the cribs to hold the cord-
wood.
Six part-time jobs have been created to support the
biomass boilers in the Southeast Island School District,
including boiler operation, wood harvest/processing,
and wood handling.
Project Contact Information
Parties Involved:
Jonathan Fitzpatrick, SISD
Email: jfitzpatrick@sisd.org
Lauren Burch, SISD superintendent
Email: lburch@sisd.org
Phone: 907-828-8254
Case Study Author:
Zoe Tressel, AEA Intern
Website: Akenergyauthority.org
Student-built wood crates, photo courtesy of Dan Bihn.
Greenhouse vegetables, photo courtesy of Dan Bihn.
Thorne Bay School Wood-Fired Boiler
Updated February, 2016