Small-scale District Heating based on Biomass

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Small-scale District Heating based on Biomass

• Joakim Lundgren
• Division of Energy Engineering
• Luleå University of Technology

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Background

• Nuclear power phase out
• A large amount of electricity is today used for
  heating purposes
• Important to reduce the electricity demand
• One measure is to convert to district heating
  an activity in progress

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Background

• Biomass based district heating for larger
  communities is well established in Sweden
• Increasing taxes on fuel oil and distribution
  network developments have made DH interesting
  also for smaller communities
• Space for at least 10 GW new installed thermal
  power in small biomass fired DH networks

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Problems

• Studies show that boilers (0.5-10 MW) emits large
  amounts of hazardous products (CO, THC, PAH, VOC)
  during low and varying heat loads
• Economy

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EU project 1998-2001

• Develop a boiler concept suitable for small DH
  systems
• Broad thermal output span (10-100)
• High fuel moisture content
• Manage heat load fluctuations
• Low emissions of harmful products in the complete
  thermal output span

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Applications

• Public buildings
• Small industries and shopping centers
• Small DH networks in villages
• in purpose to change from fossil fuels in
  existing boilers or to convert from electricity

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Layout of the research plant
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Primary combustion chamber
Gases to the sec. zone
Fuel feeding

• Partitioned combustion chamber
• Drying zone

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Secondary zone
To the boiler

• High gas temperatures
• Good mixing with combustible gases and secondary
  air
• Designed by using CFD

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Experimental results
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Conclusions

• Very low emissions of hazardous products
• Can manage fuel moisture contents up to 58
• Can handle heat load variations with kept low
  emissions
• Great potential. 10 GW means approximately 2000
  new boilers

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New projects

• Replacing an oil fired boiler in a school
  building (Demonstration unit)
• BIO-SOL. Biomass based DH in combination with
  solar energy
• Combustion of horse manure

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BIO-SOLConventional system
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BIO-SOL

• Problem
• Large heat losses during summer time, calculated
  as percentage of the generated heat
• Our idea
• Let the customers produce their own heat during
  summer

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Distributed solar collectors and heat stores
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Combustion of horse manure

• Large costs for depositing waste materials, up to
  100 per ton
• One horse produces 10 tonnes per year
• 300 000 horses in Sweden, resulting in a total
  amount of 3 million tonnes annually
• Year 2005, there will be a prohibition for
  depositing organic materials

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Combustion of horse manure

• Very large economical benefits for stable- and
  trotting course owners
• Decreasing the demand for fuel oil and
  electricity
• The only condition is that the combustion process
  must be environmentally friendly

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Experimental results