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Heating - Biomass system - Multiple buildings / Canada (Kapuskasing Airport)
Case study assignment
The director of public works for a small town in north-western Ontario, Canada has asked you to evaluate the installation of a wood-fired district heating system. The town is involved in community forest management activities that generate biomass waste. The majority of the buildings are heated with natural gas. Your study is to focus on providing district heating for the community hospital, two schools, a warehouse and an office building of the provincial Ministry of Natural Resources (MNR).
Site information
The nearest source of appropriate weather data is the airport at Kapuskasing. The town is located within Ontario's Boreal Forest region, which supports sustainable forest harvesting. The five buildings that are to be serviced by the district heating system, as well as the proposed distribution pipe layout, are shown in the figure below.
Case study assignment
The director of public works for a small town in north-western Ontario, Canada has asked you to evaluate the installation of a wood-fired district heating system. The town is involved in community forest management activities that generate biomass waste. The majority of the buildings are heated with natural gas. Your study is to focus on providing district heating for the community hospital, two schools, a warehouse and an office building of the provincial Ministry of Natural Resources (MNR).
Site information
The nearest source of appropriate weather data is the airport at Kapuskasing. The town is located within Ontario's Boreal Forest region, which supports sustainable forest harvesting. The five buildings that are to be serviced by the district heating system, as well as the proposed distribution pipe layout, are shown in the figure below.
The energy use of these buildings has been determined in an energy audit and is listed in the table below, along with floor areas. The annual efficiency of the old natural gas boilers in the buildings was estimated to be 68%.
The new biomass boiler is to be augmented by a natural gas peak load boiler, both rated at 1,500 kW (output basis). On average, the moisture content of the biomass (mostly wood chips) is 50%.
The conditions for burying the district heating piping are particularly favorable. The soil consists of sand and no other underground infrastructure is expected to interfere with the installation of the new medium temperature distribution pipe system. The majority of the pipes can be put in grass-covered areas at about 50% of the cost of typical installations under mixed (paved and unpaved) surfaces. Several other buildings representing about 20% more load are close to the proposed system.
Financial information
The customers will be billed the same as what they have been paying for natural gas heating. The average cost of biomass (mainly transportation costs) is $5/tonne, electricity rate is $0.10/kWh and the rate of natural gas is $0.33/m3 including delivery and monthly charges.
Some of the major cost items have been estimated in previous studies: the biomass combustion system will cost about $300,000 for equipment and about $105,000 to install; construction of the boiler house and biomass storage facilities is estimated to cost $185,000, including labour; the refractory insulation of the biomass boiler is expected to be replaced every 5 years at a cost of $5,000.
Typical financial figures for the analysis are provided by the municipality: fuel cost escalation and inflation rates of 2%, discount rate of 9%, debt ratio of 75%, debt interest rate of 7% and a debt term of 15 years. The project life is estimated at 25 years.
Prepare a RETScreen study, documenting any assumptions that you are required to make, and report on the significant conclusions from this analysis.
Solution
The worked-out solution is the data file selected from within the RETScreen Project Database. The user automatically downloads the Project Database file while downloading the RETScreen software.
Teacher's notes
Real project
Results
The town of Geraldton is a community of approximately 2,600 people in north-western Ontario. It is part of the Municipality of Greenstone, about 290 km northeast from Thunder Bay. The town is located within Ontario's Boreal Forest region and actively involved with community forestry management and sustainable forest industries. Partly because of its forestry focus, the community is interested in using local biomass for energy. A feasibility study demonstrated that a district heating system could be an attractive long-term investment for the community, which previously was heating most of its buildings with natural gas.
The construction of the Geraldton district heating system was completed in 1997. The district heating system serves two schools, a small office building and a warehouse. The customers were not required to make any capital contributions to the system and were not charged a connection fee. The final cost for the system was $1.6 million.
System description
The heating system consists of one 1.6 MW biomass fired boiler and a 1.6 MW peaking boiler designed and supplied by Sylva Energy Systems of nearby Thunder Bay, Ontario. Wood waste is supplied free-of-charge (with exception of transportation costs) from the community forest program and local saw mills. The fuel from the different sources is mixed in a specially designed two-bin storage system, the combustions system is a sloping reciprocating design with automatic ash handling, and the boiler is mounted on top of the combustion chamber. A wet scrubber cleans the particulates in the flue gas and the plant is equipped with a full emission monitoring system. The peaking and back-up boiler is a fully automatic natural gas fired system. Initial problems with contamination of the free biomass created unexpected downtime for the biomass boiler and more natural gas was used than expected.
During the summer months the boilers and district heating system are shut down and domestic hot water is heated with natural gas in the individual buildings.
The district heating system consists of approximately 1,200 m of pipe. The pipes are installed with a leak detection system, so that problems can be identified quickly. The district heating pumps are controlled with a variable frequency drive system. Each customer is equipped with an energy meter and bills are issued on a monthly basis. Initial problems with the implementation of the energy transfer stations reduced the system's ability to deliver the contracted amount of energy.
Also, despite early plans to do so, the hospital was not connected to the district heating due to initial concerns about the reliability of the wood fired system. However, the system was sized so that the hospital can be connected at a later date. The pipe distribution system was also oversized so that other existing and planned buildings can connect to the system in the future.
Lessons learned
The big picture
Communities with a cluster of larger buildings and available low-cost biomass fuel are viable candidates for district heating systems. Biomass from community forest projects and commercial forestry operations as well as waste wood from industrial processes are valuable resources that can be effectively used as a source of energy and thus diverted from landfill sites.
Biomass-based community energy systems also create local job opportunities and contribute to reducing greenhouse gas emissions.
Photo
District heating - Boiler - Wood waste, Ontario, Canada
References
The conditions for burying the district heating piping are particularly favorable. The soil consists of sand and no other underground infrastructure is expected to interfere with the installation of the new medium temperature distribution pipe system. The majority of the pipes can be put in grass-covered areas at about 50% of the cost of typical installations under mixed (paved and unpaved) surfaces. Several other buildings representing about 20% more load are close to the proposed system.
Financial information
The customers will be billed the same as what they have been paying for natural gas heating. The average cost of biomass (mainly transportation costs) is $5/tonne, electricity rate is $0.10/kWh and the rate of natural gas is $0.33/m3 including delivery and monthly charges.
Some of the major cost items have been estimated in previous studies: the biomass combustion system will cost about $300,000 for equipment and about $105,000 to install; construction of the boiler house and biomass storage facilities is estimated to cost $185,000, including labour; the refractory insulation of the biomass boiler is expected to be replaced every 5 years at a cost of $5,000.
Typical financial figures for the analysis are provided by the municipality: fuel cost escalation and inflation rates of 2%, discount rate of 9%, debt ratio of 75%, debt interest rate of 7% and a debt term of 15 years. The project life is estimated at 25 years.
Prepare a RETScreen study, documenting any assumptions that you are required to make, and report on the significant conclusions from this analysis.
Solution
The worked-out solution is the data file selected from within the RETScreen Project Database. The user automatically downloads the Project Database file while downloading the RETScreen software.
Teacher's notes
- The total heating energy demand was calculated by adding the space heating and domestic hot water (DHW) heating energy for all buildings. The domestic hot water heating base load is then expressed as a fraction of this total.
- The heating energy demand for each building cluster was calculated by adding the space heating and DHW heating energy, as provided in the data table. The heating load for each cluster (in W/m2) was then set to yield the correct heating energy demand. The Microsoft Excel "Goal Seek" function may also be used to find the right input (e.g. heating load) when the output (e.g. heating energy demand) is known.
- The formula method was used to calculate the heating network costs and a cost factor of 0.5 was applied to both the main and secondary distribution lines to reflect the favourable conditions for burying pipe.
- This analysis is done from the perspective of the municipality, which is proposing to install and operate the district heating system. The five buildings that are to be heated will continue to pay the equivalent rates for energy as they were paying for the old natural gas heating, but these payments will now be an income stream to the municipality. For the building owners, financial benefits of the new system will include protection from price volatility of natural gas and elimination of the capital and maintenance costs associated with operating their old heating systems.
Real project
Results
The town of Geraldton is a community of approximately 2,600 people in north-western Ontario. It is part of the Municipality of Greenstone, about 290 km northeast from Thunder Bay. The town is located within Ontario's Boreal Forest region and actively involved with community forestry management and sustainable forest industries. Partly because of its forestry focus, the community is interested in using local biomass for energy. A feasibility study demonstrated that a district heating system could be an attractive long-term investment for the community, which previously was heating most of its buildings with natural gas.
The construction of the Geraldton district heating system was completed in 1997. The district heating system serves two schools, a small office building and a warehouse. The customers were not required to make any capital contributions to the system and were not charged a connection fee. The final cost for the system was $1.6 million.
System description
The heating system consists of one 1.6 MW biomass fired boiler and a 1.6 MW peaking boiler designed and supplied by Sylva Energy Systems of nearby Thunder Bay, Ontario. Wood waste is supplied free-of-charge (with exception of transportation costs) from the community forest program and local saw mills. The fuel from the different sources is mixed in a specially designed two-bin storage system, the combustions system is a sloping reciprocating design with automatic ash handling, and the boiler is mounted on top of the combustion chamber. A wet scrubber cleans the particulates in the flue gas and the plant is equipped with a full emission monitoring system. The peaking and back-up boiler is a fully automatic natural gas fired system. Initial problems with contamination of the free biomass created unexpected downtime for the biomass boiler and more natural gas was used than expected.
During the summer months the boilers and district heating system are shut down and domestic hot water is heated with natural gas in the individual buildings.
The district heating system consists of approximately 1,200 m of pipe. The pipes are installed with a leak detection system, so that problems can be identified quickly. The district heating pumps are controlled with a variable frequency drive system. Each customer is equipped with an energy meter and bills are issued on a monthly basis. Initial problems with the implementation of the energy transfer stations reduced the system's ability to deliver the contracted amount of energy.
Also, despite early plans to do so, the hospital was not connected to the district heating due to initial concerns about the reliability of the wood fired system. However, the system was sized so that the hospital can be connected at a later date. The pipe distribution system was also oversized so that other existing and planned buildings can connect to the system in the future.
Lessons learned
- The benefits of a district heating system need to be communicated to the building owners.
- Continuous troubleshooting by experienced engineers during the construction process will iron out flaws quickly and efficiently.
- The biomass handling system needs to be able to deal with contaminated fuel.
- Non-uniform moisture content and size of the biomass fuel can lead to technical problems. This should be addressed at the project design stage.
- High system reliability is critical to attracting more customers.
- Connecting all core municipal buildings will increase the profitability of the system.
- Local contractors without previous experience with district heating can be successfully used to install the system provided that they receive proper guidance.
- The profitability of the system can change dramatically when a large potential customer decides not to get connected.
The big picture
Communities with a cluster of larger buildings and available low-cost biomass fuel are viable candidates for district heating systems. Biomass from community forest projects and commercial forestry operations as well as waste wood from industrial processes are valuable resources that can be effectively used as a source of energy and thus diverted from landfill sites.
Biomass-based community energy systems also create local job opportunities and contribute to reducing greenhouse gas emissions.
Photo
District heating - Boiler - Wood waste, Ontario, Canada
References
- McConnell, Tom, "Personal communication," Municipality of Greenstone, 2002.
- Ziegler, Urban, "Personal communication," PEMtec, 2002.
