Technical and Economic Considerations In

1. Technical and Economic Considerations In Selection of Boiler Size and Thermal Storage Capacity For Commercial and Small Industrial Wood-fired Boiler Systems “Small can be beautiful” Raymond J Albrecht, P.E. Technical Consultant to Lopper North America rayalbrechtpe@gmail.com www.LopperNorthAmerica.com

2. Typical Wood Boiler Oversizing Impacts Oversizing factor of 2 X or even 3 X peak heating load Increased space requirements within boiler room Capital cost premium for boiler, fuel feeding components, multi-cyclones and electrofilters, etc. Efficiency penalty during start-ups for morning heat during Fall/Spring seasons Excess hours for low load operating conditions (smoldering) with increased PM 2.5 and UHC/CO emissions due to lower average flame temperature

3. Tool for sizing of wood boilers: ASHRAE Weather Data American Society of Heating, Refrigerating and Air-conditioning Engineers Thousands of US/Canada and global locations Averages and maximum/minimum values Temperatures Bin hour temperature data Humidity Wind Speed Solar Radiation Available at www.ashrae.org website

4. Heating Bin Hours vs. Outdoor TemperatureTypical northern US location Design Temp = Minus 5 deg F 4800 hours per year at 55 deg F or lower 3900 hours occur between 25oF and 55 deg F 80% of heating hours at 50% or less of peak heating load

5. Wood-fired boiler sized to provide 100% of peak heating load

6. Output Analysis - 2 MMBTU/hr wood-fired boiler for entire heating load Temp bin Annual Heating Wood boiler Oil boiler Total heating Wood boiler Oil boiler (deg F) hours Load output in bin output in bin output in bin output in bin output in bin in bin Btu/hr BTU/hr BTU/hr MMBTU/yr MMBTU/yr MMBTU/yr -5/-1 6 1917000 1917000 - 12 12 - 0/4 58 1750000 1750000 - 101 101 - 5/9 66 1583000 1583000 - 104 104 - 10/14 125 1417000 1417000 - 177 177 - 15/19 243 1250000 1250000 - 304 304 - 20/24 354 1083000 1083000 - 383 383 - 25/29 511 917000 917000 - 468 468 - 30/34 957 750000 750000 - 718 718 - 35/39 720 583000 583000 - 420 420 - 40/44 636 417000 417000 - 265 265 - 45/49 577 250000 250000 - 144 144 - 50/54 585 83000 83000 - 48 48 - Totals 4838 hrs 3144 3144 Wood-fired output = 3144/3144 = 100 percent of total system output Heating oil savings = Approximately 38,000 gallons

7. Wood boiler meets 100% of peak heating load Wood boiler provides 100% of annual heating output

8. Wood-fired boiler sized to provide 75% of peak heating load Can meet heating load down to about 10 deg F Supplemental boiler provides output only for portion of heating load in excess of 1.5 MM Btu/hr at temperatures below 10 deg F

9. Output Analysis - 1.5 MMBTU/hr wood-fired boiler plus 500,000 Btu/hr Oil-fired Boiler Temp bin Annual Heating Wood boiler Oil boiler Total heating Wood boiler Oil boiler (deg F) hours Load output in bin output in bin output in bin output in bin output in bin in bin Btu/hr BTU/hr BTU/hr MMBTU/yr MMBTU/yr MMBTU/yr -5/-1 6 1917000 1500000 417000 12 9 3 0/4 58 1750000 1500000 250000 101 87 14 5/9 66 1583000 1500000 83000 104 99 5 10/14 125 1417000 1417000 - 177 177 - 15/19 243 1250000 1250000 - 304 304 - 20/24 354 1083000 1083000 - 383 383 - 25/29 511 917000 917000 - 468 468 - 30/34 957 750000 750000 - 718 718 - 35/39 720 583000 583000 - 420 420 - 40/44 636 417000 417000 - 265 265 - 45/49 577 250000 250000 - 144 144 - 50/54 585 83000 83000 - 48 48 - Totals 4838 hrs 3144 3122 22 Wood-fired output = 3122/3144 = 99 percent of total system output

10. Wood boiler meets 75% of peak heating load Wood boiler provides 99% of annual heating output

11. Wood-fired boiler sized to provide 50% of peak heating load Can meet heating load down to about 20 deg F Supplemental boiler provides output only for portion of heating load in excess of 1 MM Btu/hr during temperatures below 20 deg F

12. Output Analysis - 1 MM BTU/hr wood-fired boiler plus 1 MM Btu/hr oil-fired boiler Temp bin Annual Heating Wood boiler Oil boiler Total heating Wood boiler Oil boiler (deg F) hours Load output in bin output in bin output in bin output in bin output in bin in bin Btu/hr BTU/hr BTU/hr MMBTU/yr MMBTU/yr MMBTU/yr -5/-1 6 1917000 1000000 917000 12 6 6 0/4 58 1750000 1000000 750000 101 58 43 5/9 66 1583000 1000000 583000 104 66 38 10/14 125 1417000 1000000 417000 177 125 52 15/19 243 1250000 1000000 250000 304 243 61 20/24 354 1083000 1000000 83000 383 354 29 25/29 511 917000 917000 - 468 468 - 30/34 957 750000 750000 - 718 718 - 35/39 720 583000 583000 - 420 420 - 40/44 636 417000 417000 - 265 265 - 45/49 577 250000 250000 - 144 144 - 50/54 585 83000 83000 - 48 48 - Totals 4838 hrs 3144 2915 229 Wood-fired output = 2915/3144 = 93 percent of total system output

13. Wood boiler meets 50% of peak heating load Wood boiler provides 93% of annual heating output

14. Heating Output vs Wood and Oil Boiler Capacity Percent Percent Of Peak Of Annual Heating Heating Output/ Load Oil Savings 25% 63% 50% 93% 75% 99% 100% 100% 125% 100% 150% 100% 175% 100% 200% 100% Horizontal Axis: Wood Boiler Capacity – Percent of Peak Heating Load Vertical Axis: RED Percent of Annual Wood Heating Output (also percent Oil Savings) BLUE Percent of Annual Oil Heating Output

15. Eliminating the Smoldering Mode 300 kW wood-fired boiler plus 150 kW wood-fired boiler plus 150 kW oil-fired boiler for Peak and Low Loads Use oil -fired boiler until heating load reaches at least 20-30 percent of capacity of smaller boiler (i.e., about 50 kW) depending on thermal storage “On” temperature for wood-fired boiler about 10 deg C Wood-fired boiler still provides 95% of total annual output

16. Thermal Storage 1 BTU = 1 lb Water X 1 deg F delta T Typical practical delta T = Approximately 40 to 60 deg F One gallon Water = 8.33 lbs 100 gallons Water X delta T of 40 deg F = 33,320 BTU of thermal storage 500 gallons Water X delta T of 60 deg F = 250,000 BTU of thermal storage 20,000 gallons Water X delta T of 40 deg F = 6,650,000 BTU of thermal storage 20,000 gallons Water = 2666 ft3 = Tank dimensions of 18 ft L X 18 ft W x 8 ft H

17. Case Study: Large Institutional Logwood-fired Boiler System Abbey of St Benoit du Lac St Benoit du Lac, Quebec Canada

18. Twin Commercial Size Logwood-fired Boilers Ultra-low PM 2.5 emissions (0.01 to 0.02 lb/MMBtu ) Less than 100 ppm NOx 82 – 84 percent efficiency (HHV) Lambda (air/fuel ratio) control with independent primary and secondary air flow control Vertical extension to primary gasification chamber to double wood loading capacity up to 16 hours full-capacity burn time Decoupling of wood loading capacity from firing capacity important factor in meeting user interest in reduced frequency of reloading Each boiler has 1.1 million BTU/hr (320 kW) thermal capacity Total thermal capacity of 2.2 million BTU/hr (640 kW) Peak heating load is about 2.5 million BTU/hr (730 kW) Approximately 150,000 square feet of heated space

19. Storage Tank Benefits include smoother boiler loads plus pre-charging to handle peak heating loads Approximately 6000 gallons 6000 gal X 8.33 lb/gal X 40 deg F delta T = 2 million Btu storage capacity Can boost system capacity by 500,000 Btu/hr for 4 hrs during peak morning loads

20. Storage barns for logwood 350 cords per year One year drying time Steel racks for logwood bundles Boilers can handle up to 48 inch log lengths Approximately 1/3 cord wood per bundle One logwood bundle provides for 8 hours of boiler operation under full-load conditions Boilers can handle two bundles maximum wood loading

21. Tractor loading of logwood bundles Tractor with front end loader carries logwood bundles from storage barn to boiler house System includes small overhead crane Bundle is lowered into top loading door Chains are then released and removed with bracket assembly

22. Economics of Logwood Boiler Installation Purchase cost of approximately $50,000 per boiler Installation cost of approximately $50,000 including labor and accessories Total system installed cost of approximately $150,000 Heating oil savings = 60,000 gallons per year Heating oil cost savings = about $220,000 Logwood consumption = 350 cords per year Total logwood fuel cost = $35,000 per year Labor/equipment cost = $50,000 per year (estimate) Total cost savings = $130,000 per year Payback period = Just over one year Payback period would have been more than two years if boiler oversized by 2 or 3 X factor especially if larger building required Payback period would be about 9 months if only one boiler had been installed Abbey of St Benoit du Lac St Benoit du Lac, Quebec Canada

23. Craftsbury Outdoor Center Craftsbury, Vermont Integrated energy system of industrial-grade logwood-fired boiler (240,000 Btu/hr) with 150 kW biodiesel-fired CHP and solar thermal plus 20,000 gallons thermal storage system Photos courtesy of WR Boilers of Fairfield, Vermont and Lopper North America

24. Conclusions • 25 % undersizing only 1 % loss of total annual wood heating output and heating oil savings • 50 % undersizing only 7 % loss of total annual wood heating output and heating oil savings • Reducing boiler size by 50 % can save 20 to 30 % in capital cost and • length of payback period • Using oil or propane-fired boiler for low load conditions can prevent • smoldering conditions with just small increase in oil/propane use • Shorter payback periods More customers • Higher efficiency  Lower Fuel Costs • Lower emissions  Happier neighbors • “Small can be beautiful”

25. Thank You!