Wood-Chip Heating Systems - Biomass Energy Resource Center

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WOOD CHIP HEATING SYSTEMS 72 Mount Wachusett Community College, Gardner, Massachusetts System Size: 8 MMBH Manufacturer: Messersmith Manufacturing The separate boiler house shown on the left heats the main college building and a fi tness center with pool. The system uses advanced emissions control equipment to meet stringent air quality standards. The tall stacks help reduce on-site air impacts to a negligible level. smoothly in settings such as schools, hospitals, and commercial buildings. This process of taking wood combustion out of the sawmill and putting it into public buildings has been successful, as evidenced by the scores of facilities now burning wood chips and other forms of biomass. In the early 1990s, the question of combustion effi ciency in our existing institutional and commercial biomass systems was explored through testing in the Northeast and eastern Canada. Manufacturers and engineers involved in the next generation of installations have integrated the lessons learned from these tests into the system designs. The result has been more routine combustion testing and tuneups by manufacturers, better effi ciency and cleaner emissions. Although stack emissions have not been a problem for most existing institutional and commercial biomass burners, emissions from wood systems are an area of growing concern on the part of environmentalists and the general public. Large utility, sawmill, and industrial wood boilers are tested regularly for air emissions, but plants in schools and businesses are small enough that air quality regulators have not spent much time testing and gathering data about them. More precise, clearly articulated and broadly available information in this area is needed. Over the last ten years, vendors have made numerous small changes to their systems that have signifi cantly improved reliability and made operation smoother for users. Problems with bin unloading equipment and fuel conveyors have been addressed and largely solved. Control panels have been improved so that they carry out more sophisticated functions while remaining simple for the operator to use. Daily
maintenance time has been reduced to less than 30 minutes in most cases. All parties have listened to and acted on what operators have been saying: that larger bins make life much easier for the user, compared to bins that only hold only one truckload of chips. Fuel supply is an area that continues to require ongoing vigilance, on the parts of both users and state offi cials. Users rarely have the luxury of long-term, stable relationships with a single chip supplier without the need for yearly reassessment. When users regularly stay on top of chip prices and the competitive fuel market, prices tend to stay low. Having said that, users fi nd that keeping a stable relationship with a single, reliable fuel supplier is an invaluable asset. Users have learned that mill residue chips provide the most trouble-free operation. They tend to prefer mill chips over fuel chipped in the woods. However, in some regions mill chips may be hard to fi nd at a reasonable price. Bole-wood chips from logging operations have been used successfully in many cases. The critical factor is that the supplier of forest chips be very interested in serving the institutional market and be committed to producing a uniform quality chip similar to a mill chip. If a forest chipper slips into delivering school customers loads with too many oversized chips, they will quickly lose the confi dence of their customers and their business. State forestry and education offi cials can play a critically important role in helping to create and maintain a stable fuel market for school users. Vermont’s energy offi ce, in partnership with the state forestry agency and the school superintendents’ association, created a support program that has benefi tted schools with wood energy systems. Each year a meeting is held for system operators to discuss issues of concern and share information about fuel supply and other matters of common interest. The state collects and shares data on wood fuel prices, energy consumption and fuel supply, so that all users (and others) can see who is supplying who at what price and can compare their fuel consumption with other schools on a square-foot basis. The state initiative also helps to link individual schools with fuel suppliers and to solve short-term fuel supply problems. New Uses on the Horizon In the future we may see more use of biomass in heating plants, both for smaller commercial facilities and for applications larger than those discussed in this guide. On the large side, using biomass to fuel “district heating” plants is becoming a recognized option, economically viable in some settings. District heating is the use of a central boiler facility with buried piping that serves the heating needs of a number of nearby buildings. District heat systems have been common in settings such as college and university campuses for many years. Since one of the drawbacks of biomass heating plants is their relatively high capital cost, it makes sense to have one plant provide heat to a number of buildings. Large district heat systems that burn biomass are fairly common today. A number of colleges in the Northeast and elsewhere currently have biomass-fi red district heating systems. St. Paul, Minnesota, has a very large urban-district heating and cooling system that burns biomass, as do the complexes of government buildings in Montpelier and Waterbury, Vermont. The St. Paul system uses hot water to distribute heat, while the Vermont state district systems (and most older campus systems) use steam as the medium. In Scandinavia, district heating is widely used and the technology is highly developed. The capital of Prince Edward Island, Charlottetown, has a 20-yearold modern Scandinavian-style downtown hot-water district heating system that burns whole-tree chips and other forms of waste biomass. Small district heating systems are also common in settings where one plant may heat two or more adjacent buildings. Examples include schools with two or three buildings on the same property, and hospitals with plants that also heat nearby medical offi ce buildings or nursing homes. A fi rst-of-its-kind district system was installed in 1991 to provide low-cost wood-chip heat to nine buildings of a 50-apartment, low-income family housing project in Barre, Vermont. This system now has over a decade of reliable operation, with a monthly fuel cost of $26 per apartment for all heat and hot water, averaged over ten years. In 2003, the fi rst school wood energy system in the Rocky Mountains was installed to serve a three-school campus in western Montana. On the small side, expect to see an expanded use of semi-automated systems to serve smaller schools and commercial buildings. Fully automated systems have proven to be economically viable in large schools, but the high capital cost sometimes puts them out of reach of smaller schools, facilities with less access to capital, and those that expect a quicker return on investment. Gasifi cation: Promise for the Future Gasifi cation of biomass is an exciting technical development that promises to open up new and more effi cient uses of wood chips and other forest fuels. 1 A WOOD CHIP HEATING SYSTEMS 73
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Wood-Chip Heating Systems A Guide F
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Wood-Chip Heating Systems A Guide F
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TABLE OF CONTENTS How to Use This B
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The appendices may be consulted as
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urners in the biomass fuel-producin
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Fuel Hardwood Chips No. 2 Fuel Oil
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Randolph Union High School, Randolp
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CHAPTER TWO Wood Chips and Other Ty
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Barre Town Elementary School, Barre
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in a system designed to burn hardwo
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Figure 3.1 A Typical Biomass System
Page 23 and 24: An Important Relationship: Fuel Sou
Page 25 and 26: Murray Farms Greenhouse, Penacook,
Page 27 and 28: oiler facility. However, the backup
Page 29 and 30: The use of powerful and potentially
Page 31 and 32: in effi ciency: the higher the mois
Page 33 and 34: an effi ciency of 69%. This differe
Page 35 and 36: at a higher capital cost. For examp
Page 37 and 38: Older Residential Stove 1 EPA Certi
Page 39 and 40: CHAPTER SIX Types of Biomass Combus
Page 41 and 42: Figure 6.2 Two-Chamber Combustion S
Page 43 and 44: Cost-Effectiveness of Wood-Chip Sys
Page 45 and 46: Figure 7.3 Existing Gas Cost/ccf $3
Page 47 and 48: a value, independent of concerns ab
Page 49 and 50: • initial system equipment/instal
Page 51 and 52: engineering fi rms that specialize
Page 53 and 54: CHAPTER NINE Finding Capital to Pay
Page 55 and 56: installation and do not incur the r
Page 57 and 58: CHAPTER TEN Putting Together and Im
Page 59 and 60: The Importance of the System Operat
Page 61 and 62: Q: Will wood smoke cause acid rain?
Page 63 and 64: Data on the installed cost of bioma
Page 65 and 66: say exactly how it should do that.
Page 67 and 68: Green Acres, Barre, Vermont Facilit
Page 69 and 70: Contracting and Project Structure O
Page 71 and 72: fully trained in operating, maintai
Page 73: CHAPTER TWELVE The Future of Biomas
Page 77 and 78: APPENDIX A Northeast Regional Bioma
Page 79 and 80: APPENDIX C Wood-Fuel Energy Data I.
Page 81 and 82: APPENDIX D Assumptions Used in Deve
Page 83 and 84: Current year oil price . . . . . .
Page 85 and 86: Net Annual Savings $100,000 $90,000
Page 87 and 88: Glossary Appliance effi ciency: The
Page 89 and 90: Furnace: The primary combustion cha
Page 91 and 92: Sizing: The process of specifying t
Page 93: Jarrett, Branyon O. “Catch 22 in
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