ATHOL-ROYALSTON REGIONAL SCHOOL DISTRICT WOOD ENERGY HEATING CONVERSION PROJECT

PROJECT DESCRIPTION & SUMMARY

White Paper

February 2002

Prepared by: 

Rob Rizzo, Associate Director
Forest & Wood Products Institute

ABSTRACT:

In 1998 the Athol-Royalston Regional School District installed a wood chip heating system in the Athol High School to replace/supplement an aging fuel oil system. This report summarizes the data from their first three heating seasons during which the School District realized an estimated savings of over $26,000.00 through the utilization of a biomass heating system.

PROJECT DESCRIPTION:

• Wood chip heating system installed summer 1998 and first operated fall 1998
• Athol High School building is 89,000 sq. ft., serving 800 students
• Four components needed to be addressed to renovate/replace the existing #2 fuel oil heating system:

1. Remove asbestos from the boiler room
2. Remove two underground fuel tanks
3. Remove one of two existing boilers, burners and associated controls; one oil burner/boiler remains as a back up
4. Install a new wood boiler system

• The existing oil system supplies forced hot water to meet the space heating and domestic hot water needs of the High School.
• The new wood chip system utilizes the same hot water distribution plumbing with the only difference being that the domestic hot water is heated by wood only during the months that the system is operational (October - mid March). During other times, the domestic hot water is heated by fuel oil.

PROJECT COSTS:

• Total project cost: $450,000
• The School District appropriated: $300,000 (Total cost to replace the existing equipment including asbestos abatement and the removal of two leaking underground fuel oil storage tanks)
• The Massachusetts Legislature appropriated: $150,000 (additional cost to install wood chip system)

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EQUIPMENT DESCRIPTION:

The wood chip equipment is comprised of a number of elements to establish a complete, automatic operating system:

1. Chip delivery and storage system
2. Chip handling system
3. Combustion system
4. Heat exchange
5. Boiler room, backup fuel system, and domestic hot water
6. Emission control system
7. Ash removal system
8. Safety devices
9. Chimney

In the original design, the planned capacity of the fuel storage system was limited to 20 tons (approximately one trailer load) of chips. This resulted in problems with truck delivery scheduling. At times the system had to be shut down resulting in burning more fuel oil than anticipated. During the summer of 2001, the staff has resolved this problem by increasing total capacity to approximately 30 tons.

The School District purchased a complete turnkey package from CHIPTECH Corporation of South Burlington, VT. Included were:

• CHIPTECH fuel storage and handling system
• CHIPTECH Model C-3, 3MM BTUs/HR., 90HP Gasifier Firing Rate @ 40% Moisture Content (MC) = 705lbs./hr.
• Hurst Boiler Inc., Model 4462 heat exchanger/boiler with a maximum water pressure of 30 PSI.
• Automatic ash removal system
• Cyclone air emission control system
• Associated controls and safety devices

The existing chimney did not need replacement
Installation was completed by: Royal Steam Heater Co., Gardner, MA

FUEL SOURCE & SPECIFICATIONS:

• The system is capable of burning hardwood or softwood chips, but the District has decided to purchase the more expensive hardwood chips which produces higher BTU values.
• Hardwood sawmill chips with the bark removed (paper quality chips) are specified in the District's current 'request for bid' sheet (available upon request).
• Whole tree chips refer to tree stems including bark, branches, leaves (in season) and/or needles (softwood).

ANNUAL FUEL CONSUMPTION:

Prior to the conversion, the High School burned fuel oil with no emission controls in place.

TABLE 1.  ANNUAL FUEL CONSUMPTION (prior to conversion to wood)

At the end of the 1996 -1997 heating season, the District chose to use the lighter, more refined #2 heating oil to 'extend the life' of the aging oil burner.

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TABLE 2. 

ANNUAL FUEL CONSUMPTION and COST SAVINGS SINCE CONVERSION

Table 2 illustrates that during the 2000-2001 heating season a number of changes occurred to contribute to a 58% increase in annual savings over the previous year. During this heating season, the school switched from burning whole tree chips to sawmill residue chips. It should be noted that although sawmill chips cost 60% more/ton than whole tree chips, the efficiency and BTU value output increased by 28% due to a lower MC of the sawmill chip. In addition, the consumption of 72% more chips than the previous year greatly increased the total annual savings. As mentioned earlier, whole tree chips are less consistent in size and quality than sawmill residue chips. At times, the chip feed system would become clogged at the out-feed of the storage bin due to an over-sized branch, twig, a piece of bark, or wood becoming jammed and stopping the flow of the feed stock. This resulted in the wood system shutting down and the back-up oil system starting up. The automatic switching by the system to fuel oil contributed to the overuse of fuel oil for the first two years of operation. School maintenance personnel retrofitted the out-feed of the storage bin at the end of the second season, which they believe ended their clogging problem. A more likely scenario is that the change from whole tree chips to sawmill residue chips remedied the problem.  It is unknown if the manufacturer is aware of this chip-handling problem, or if it has been a problem in other applications. Future purchasers may wish to consider alternative designs, using whole tree chips that have been screened to remove over-sized pieces, or working with the manufacturer to remedy this potential problem.

Total Savings to the School District from first three years of operation: $26,535.66

Annual Savings have been calculated as follows:

• Assumption: Based upon historical data of fuel oil usage prior to conversion, the average gallons consumed in any given year are 52,703 gallons.
• Actual fuel usage and cost savings calculations:

1998-1999 heating season:

52,703 gallons x $.54/gallon = $28,459.62 (assumed total fuel cost without the conversion)
328 tons x $18/ton = $5904 (actual cost for chips)
27,830 gallons x $.54/gallon = $15,028.20 (actual cost for fuel oil)
$5904 + $15,028.20 = $20,932.20 (actual total cost of all fuel consumed)
$28,459.62 - $20,932.20 = $8,431.42 (Total Savings)

1999-2000 heating season:

52,703 gallons x $.63/gallon = $33,202.89 (assumed total fuel cost without conversion)
337 tons x $18/ton = $6066 (actual cost for chips)
31,934 gallons x $.63 = $20,118.42 (actual cost for fuel oil)
$6066 + $20,118.42 = $26,184.42 (actual total cost of all fuel consumed)
$33,202.89 - $26,184.42 = $7,018.47 (Total Savings)

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2000-2001 heating season:

52,703 gallons x $.89/gallon = $46,905.67 (assumed total fuel cost without conversion)
578 tons x $28.75/ton = $16,617.50 (actual cost for chips)
21,600 gallons x $.89/gallon = $19,202.40 (actual cost for fuel oil)
$16,617.50 + $19,202.40 = $35,819.90 (actual total cost of all fuel consumed)
$46,905.67 - $35,819.90 = $11,085.77 (Total Savings)

$8,431.42 + $7,018.47 + $11,085.77 = $26,535.66 Total Savings
to the School District from the first three years of operation.

Contracts have been executed for the 2001 -2002 heating season:
Sawmill wood chip residue: $28.75/ton
#2 fuel oil: $.89

The District purchased whole tree chips from a local land clearing company for the first two years of operation. It was decided to purchase debarked, hardwood sawmill residue chips from local sawmills at the start of the third-heating season.

This was done primarily to obtain:

• A more uniform size chip
• A higher BTU fuel
• A relatively stable moisture content

Table 3. Differing heat values based upon average MC

A science class at the High School analyzes each load of chips for MC as a component of the curriculum. During the 2000-2001 heating season, the sawmill residue chips averaged 28% MC. As illustrated in Table 3, this is not typical of hardwood chips in the Northeast. Possible reasons for the lower MC might include; incorrect laboratory analysis or calculation of MC, a wide variety of species, or delivery of chips from logs that were not freshly cut.

CONCLUSION:

The annual savings to the District in the third year of operation (2000-2001) is significant. A reduction of over 10,000 gallons of #2 fuel oil from the previous year, and an overall reduction of over 31,000 gallons per year as compared to the fuel oil usage before the conversion demonstrates that the District is saving money. In fact, in the first three years of operation the conversion has saved $26,535.66 and has offset 76,745 gallons of #2 fuel oil.

The Athol High School wood chip heating system is saving the School District money over the fuel oil system that it has replaced. This system is capable of greater savings as has been documented in case studies in Vermont where over 20 schools have installed wood chip heating systems. Further investigation is recommended to examine some of the interacting components of the system such as the efficiency and cycling of the back-up oil burner, the electrical controls to analyze how the wood boiler interacts with the back-up burner, the electrical engineering design, the heat exchange system, the ventilation control strategies, and the stack temperature. The above should be components of a complete energy audit performed at the school to ensure that the system is at the maximum efficiency. Other Energy Conservation Measures (ECM's) should be examined to further reduce the heating load and increase the climate control efficiency of the school building. The local electricity utility company has professionals on staff to assist in this regard.

This report has not attempted to calculate the total impact on the local economy, but it should be noted that Hubbard Forest Industries, Inc. of Royalston MA has been supplying the sawmill wood chip residue fuel, and the Royal Steam Heater Co, Inc. of Gardner MA completed the installation.

Every heating system will perform differently based upon the interacting components mentioned above, other ECM's that have been employed, and the fuel source and consistency. These factors must be taken into consideration in the planning and engineering of a new or replacement system. This report has attempted to summarize the Athol biomass conversion project based upon the facts presented by school personnel.

CONTACTS:

Rob Rizzo, Associate Director
Forest & Wood Products Institute
Mount Wachusett Community College
444 Green St., Gardner, MA 01440-1000
978-630-9137
r_rizzo@mwcc.mass.edu

Special thanks to Bob Muzzy, Maintenance Operations Supervisor, Athol-Royalston Regional School District, 250 S. Main St., Athol, MA 01331; 978-249-2400; and

Tim Maker, Director, Biomass Energy Resource Center, P.O. Box 1611, Montpelier, Vermont, 05601. Tim can be reached at 802-223-7770 or fax 802-223-7772

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