The URL can be used to link to this page

Home My WebLink AboutWood Boiler StudyWOOD HEAT BOILER DESIGN & PERMITTING JUNE 2, 2010 For ATTN: LAMAR COTTEN LAKE & PENINSULA BOROUGH P.O. BOX 495 KING SALMON, ALASKA 99613 SUBMITTED BY: KOHKANOK AERIAL VIEW ANTHC KOKHANOK CLINIC DESIGNED BY RBA CCSS WOOD BOILER SUMMARY RBA ENGINEERS, INC. HELE Wood Boilers for Lake & Peninsula Borough EXECUTIVE SUMMARY RBA Job No. LP-02 June 1, 2010 The main goal of this project is to offset the heating fuel costs in the Lake & Peninsula District by installing wood boilers. RBA Engineers examined different wood boiler manufacturers as well as different wood fuels (cords, chips and pellets) for the proposed installations. The sites with low fuel consumption can be equipped with high efficiency cord wood boilers. Larger installations, with higher fuel consumption, need a larger and automated boiler system which can only be achieved by using wood chips or pellets. For the cord wood boilers, the simple payback per boiler is estimated to be 4-19 years1. For wood chip boilers, the pay back is estimated between 6-7 years. Village Potential Wood Boiler Site Fuel Consumption in Gal/yr Suggested Boiler System\ Manufacturer Investment Cost in $ Payback in Yrs Iguigig School & Teacher’s Housing 4,627 Cord Wood / Central Boiler – E Classic 2400 $117,000 5 Iliamna Maintenance Shop, Firehall & Shed 4,336 Cord Wood / Central Boiler – E Classic 2400 $185,000 8 Kokhanok-I Firehall 4,600 Cord Wood / Central Boiler – E Classic 2400 $149,000 6 Kokhanok- II KVC Office & Community Bldg 3,000 Cord Wood / Central Boiler – E Classic 2400 $143,500 9 Newhalen School 18,000 Wood Chip Boiler - Viessmann or Chiptec $650,0002 7 Nondalton-I Option 1: City Hall 10,400 2 x Cord Wood / Central Boiler – E Classic 2400 $199,500 4 Nondalton- II Option 2: School, Houses (1-10), City Hall 30,810 Wood Chip Boiler - Viessmann or Chiptec $950,0002 6 Pedro Bay VC & School 4,575 Cord Wood / Central Boiler – E Classic 2400 $188,500 8 Port Alsworth School & Improvement Center/Firehall 2,000 Cord Wood / Central Boiler – E Classic 2400 $192,000 19 More detailed analysis for each site is provided within this report. RBA ENGINEERS, INC. If grant money is available and 25% of the investment cost is to be contributed by the Lake & Peninsula Borough, the following table shows the paybacks based on 25% of the investment cost. Village Potential Wood Boiler Site Fuel Consumption in Gal/yr Suggested Boiler System\ Manufacturer 25% of Investment Cost in $ Payback in Yrs Iguigig School & Housing 4,627 Cord Wood / Central Boiler – E Classic 2400 $29,500 1.5 Iliamna Maintenance Shop, Firehall & Shed 4,336 Cord Wood / Central Boiler – E Classic 2400 $46,500 2 Kokhanok-I Firehall 4,600 Cord Wood / Central Boiler – E Classic 2400 $37,500 1.6 Kokhanok- II KVC Office & Community Bldg 3,000 Cord Wood / Central Boiler – E Classic 2400 $36,000 2.5 Newhalen School 18,000 Wood Chip Boiler - Viessmann or Chiptec $162,500 1.7 Nondalton-I Option 1: City Hall 10,400 2 x Cord Wood / Central Boiler – E Classic 2400 $50,000 1 Nondalton- II Option 2: School, Houses (1-10), City Hall 30,810 Wood Chip Boiler - Viessmann or Chiptec $237,500 1.5 Pedro Bay VC & School 4,575 Cord Wood / Central Boiler – E Classic 2400 $47,000 2 Port Alsworth School & Improvement Center/Firehall 2,000 Cord Wood / Central Boiler – E Classic 2400 $48,000 5 Cord Wood Boiler Description: Cord wood boilers are fairly simple systems since the only wood processing steps are chopping the tree into large pieces followed by stacking, storage and air drying. Most cord wood boilers are manually operated. Depending on the unit size and outside temperature, the boilers need to be loaded 1-3 times a day. The ash needs to be removed after every complete burn. While older designs of cord wood boilers had issues with incomplete combustion and emissions, many manufacturers have been working on RBA ENGINEERS, INC. improving their systems to meet the new EPA standards (Phase I - 4.5 g/h, Phase II – 18 g/h). The Central Boiler outdoor furnace is located outside, typically 30 to 200 feet away from the building served, and can be either tied into the existing heating system or it can supply a secondary heating system that operates independently. A water jacket surrounds the furnace firebox and heat exchanger, and heated water is circulated to the building through insulated underground pipes. The outdoor furnace is designed to work with any existing heating system. Water-to-air or water-to-water heat exchangers or direct circulation conveys the heat into the structure's forced-air furnace, radiant baseboard, or radiant floor heating system. This allows normal thermostatic temperature control. The outdoor boiler can also provide heat for domestic hot water by adding a water-to-water heat exchanger4. Further, multiple buildings can be heated with one outdoor boiler. The manufacturer claims efficiencies up to 90% for the E Classic model that has been evaluated. Wood Chips Using wood chips are the first step up from using raw wood logs. Wood chips use eliminates the expensive pellet making process. A wood chipper needs to be purchased to process the trees. Morbark 100 HP wood chippers are available in the price range of $30,000 to $100,000 each. When compared to cord wood system, some of the overall wood supply cost (including labor) should be recovered as the harvesting is faster and more highly automated. Also there is no cord wood stacking necessary. Further, there is a greater supply, partly because all parts of a tree can be chipped, whereas small limbs and branches can require too much labor to be worth converting to cord wood. Wood chips are similar to wood pellets, in that the movement and handling is more amenable to automation than cord wood, particularly for smaller systems. For example, a small loader can move wood chips but cord wood has to be handled much more manually. Cordwood generally needs to be "seasoned" or "dry" before it can be burned cleanly and efficiently. On the other hand, woodchip systems are typically designed to cleanly and efficiently burn "green chips" with much higher moisture content of 43-47% (wet basis). Manufacturers for wood chip boilers include Viessmann, Messersmith, Chiptec, etc. Chiptec manufactures the Phoenix Series wood chip boilers from 1,500MBH to 20,000MBH, all with a 20:1 turn down ratio. It should be noted that Chiptec equipment has been successfully demonstrated at the Craig, AK wood boiler plant. The facility uses wood shavings, chips, hog fuel and dried planer shavings to heat the school and municipal pool. This project was funded by AEA, Denali Commission, USDA Forest Service, USDA National Resource Conservation Service, and the City of Craig. For the Newhalen School, the smallest Chiptec Phoenix unit could be used. The manufacturer quoted a packaged system including fuel receiving and handling (fuel bunker), automated fuel feeding system (metering auger), gasifier, boiler, fly-ash- removal (cyclone), induced draft fan, controls, stack and breeching for $270,000. The RBA ENGINEERS, INC. total construction cost including setting up a structure that houses the boiler is estimated to be $650,000. The efficiency of the unit is about 80%. Wood Pellets (Not Suggested) The advantage of pellets is the higher heating output and that there is virtually no dust. Different from wood chips, which vary in size and are often mixed with twigs and sawdust, manufactured wood pellets are smooth and of uniform shape. For wood chips, the probability of jamming in feed mechanisms is small. Thus, jams hardly every occur. MES makes the Okofen, which was developed in Austria but is manufactured in the US. The vessel is made in Pennsylvania and the unit is assembled in Maine. MES would provide a packaged system of 4 boilers (4 x 180MBH each) installed in a container including controls, automatic pellet feeding and ash removal. The container also houses a 20-30 ton storage area. The system would cost $140,000 plus shipping. However, the challenge is to supply the boiler with high quality pellets to insure proper input. It was estimated that about 150 tons of pellets would be needed to supply the school for one year. Since there is no pellet mill near Newhalen, the pellets would have to be made locally. Pellet makers are available for small (residential) and large application (industrial size mills). The 150 tons per year is neither small nor large, it is medium size; there is very little equipment & technology available for the medium range. In order to make a high quality pellet, a comprehensive mill process including forced drying would be necessary. A micro-mill would likely cost $250,000 while a large mill can cost up to $16,000,000. Also, the manufacturer requires the installing contractor to obtain training at the factory which is essential to the success of the operation. Due to the much higher investment requirement, this system is not suggested for the Lake & Peninsula Borough at this time. Notes: 1) Based on 7$ per gal of fuel oil and $250 per cord of wood. 2) These are rough cost estimates – Detailed cost break downs can be provided upon request. _______________________________________________________________________ This report has been prepared by Raj Bhargava, PE and Michael Hauke in consultation with Lamar Cotten, Borough Manager, and Bob Loeffler (Jade North). The authors may be contacted at (907) 276-3768. School Fuel Oil Survey Lake & Peninsula School District Fuel Oil Used [Gallons Per Year] Community School Area [Square Feet] No. of Students Waste Heat From Power Plant [Yes/No] 2008 2009 REMARKS Please give any reason why a wood boiler should not be considered for this school Iliamna None Kokhanok School 16,480 Housing 4,920 32 Yes 7,488.5 6,658.0 Waste heat system minimizes usage. Upgrades improved utilization by housing and out buildings. Newhalen School 20,560 Housing 6,384 74 No 17,887.3 18,442.8 Working with INNEC to install electric boilers to utilize excess generation from Tazmina and expected geothermal power for electric boilers. Nondalton School 16,396 Housing 4,263 32 No 10,945 20,410 Working with INNEC to install electric boilers to utilize excess generation from Tazmina and expected geothermal power for electric boilers. Pedro Bay School 6,700 Housing 1,876 10 Yes 3,014 2,678 Waste heat system minimizes usage. Potential for closing Pedro Bay school in the fall of 2010 is great. Not expected to have 10 students for the October 2010 student count. Port Alsworth School 8,580 Housing 3,176 40 Yes 1,727 550 Waste heat upgrades added housing units to the loop. As a result the usage has dropped to a minimal level. It would cost more to purchase wood/pellets. Fuel is mostly for housing boilers seldom run. Iguigig School 8,120 Housing 1,150 18 No 5,931.7 4627.2