Heating - Biomass system - Multiple buildings / Canada (Chibougamau-Chapais)

Case study assignment

You have been hired by a Canadian Aboriginal Community to prepare a pre-feasibility study on their behalf. They wish to construct a new village in northern Quebec, Canada, using renewable energy as the main source of heat. Logging is one of the main economic activities in the area, and local sawmills could provide waste wood for a biomass heating system for the village. Sawmills only utilise a fraction of the harvested log; the wood waste from a sawmill with dry kiln includes bark, sawdust, shavings, and chips from wood that can not be cut to dimensional lumber. The village planners would like to know if a biomass district energy system using this wood waste would be more cost-effective than electric baseboard heaters or oil-fired furnaces sited in each individual building. They are interested in looking at the initial phase of the community with the understanding that if this proves financially viable, then they will invest in a larger design study to provide heat for the entire community as it grows in the future.

Site information

The community will construct 30 single family homes, each 125 m², built to specifications exceeding the Canadian R-2000 building standard. The houses are offset 12 m from the centre of the road and each property is 20 metres wide. The community will also construct a school (700 m²), band office (500 m²) and a clinic (200 m²). A new cultural centre (600 m²) is planned for the next few years. The public buildings are offset 30 m from the centre of the road. The planned layout of the village is such that any further expansion of housing for the village will be directly to the north of the heating plant. The plan of the community is provided here.

The area planned for development has sandy soil, without rock. A sawmill is located approximately 26 km from the proposed site. The nearest meteorological station is at Roberval Airport, Quebec, Canada.

Financial information

Typical financial figures for the analysis are provided by the community: debt ratio of 90%, debt interest rate of 8%, discount rate of 12%, and a debt term of 20 years, and inflation rate of 2.5%. The community will not pay income tax. The system is assumed to last 25 years.

Wood waste is available free of charge from the sawmill, but transporting it will cost about $7/tonne. The average price of electricity is $0.15/kWh and oil is delivered to the community at $0.45/litre. Fuel costs are expected to escalate at the same rate as inflation. The cost of conventional oil-fired boiler heating systems will average about $2,500 per building. The community is somewhat remote and labour costs are relatively high.

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

• When the type of wood waste is unknown, assuming a medium heating value and about 40% moisture content is often reasonable. This has been done here.
• The village has been broken into 14 clusters. Since there are more buildings than clusters, the seven houses at the end of each of the residential distribution lines have been put in a single cluster (see the cluster and piping diagrams). The main distribution line pipe for the last seven houses is lumped in with the DN 32 secondary pipe. Thus this 144 m of "secondary pipe" involves 3 x 20 m = 60 m of main distribution line pipe and 7 x 12 m = 84 m of true secondary distribution line pipe.
• The cultural centre is included as a load, such that the main distribution pipe and the boilers will be able to accommodate it when it is built.
• The pipe oversizing factors are set to 0% because the village will not grow further in this direction.
• The energy transfer station costs and the main distribution line pipe costs have been multiplied by a factor of 0.8 while the secondary distribution line pipe costs have been multiplied by a factor of 0.7. Costs are low because the district energy system and village are constructed concurrently: streets and sidewalks will not need restoration and other services will not interfere.
• The renewable energy equipment installation costs are higher than normal because of the relatively remote location and associated high labour costs.
• The district energy system is compared with the option of putting an oil-fired furnace in each individual building. The district energy system is even more financially attractive when compared with electric baseboard heating, or when the maintenance costs of all the oil furnaces throughout the community are included.
• Energy delivered by a district heating system is sometimes sold for 100% more than the avoided cost (i.e., than the cost of competing energy sources). This reflects the benefits of the district energy system to the local community: jobs are created and money stays within the community. These benefits are not considered in this analysis.

Real project

Results

In 1992, the Oujé-Bougoumou Cree Band Office near Chibougamau (approximately 250 km north west of Roberval, Quebec, Canada) contacted the CANMET Energy Technology Centre of Natural Resources Canada. The Band Office was planning a new community and wanted to know whether it would be possible to install a district energy system similar to that used in the recently closed Distance Early Warning (DEW) radar station in Chibougamau. Specifically, they wished to know whether a biomass-fired district energy system would be more cost-effective than heating with electrical baseboard heaters or oil-fired furnaces in each building.

The original study, prepared by a consulting engineer and sponsored by CANMET, demonstrated that a district energy system using biomass for base load and oil-fired boiler for peak load would be cost-effective. During the summer of 1992 construction started on the village with a low temperature (90 ºC) biomass-fired district energy system.

In 2000, biomass provided 89.2% of the energy used to fuel the district heating system and accounted for approximately 17.8% of the fuel costs. In that year, the system generated 7,688 MWh of heat using biomass and 873 MWh using oil.

The community of Oujé-Bougoumou has received many awards in the domain of sustainable development:

• The United Nations honoured the community with the "We the Peoples: 50 Communities Award," in the category of Human Settlements. This was an award issued to commemorate the 50th anniversary of the founding of the United Nations.
• The Together Foundation and the United Nations Centre for Human Settlements (UNCHS) worked as partners in 1995 to compile a "knowledge base" of best practices for human settlements, collected from communities around the world. The Technical Advisory Committee cited Oujé-Bougoumou as one of the top initiatives, and the community was awarded a Best Practices designation.
• In 1994 the Canada Mortgage and Housing Corporation (CMHC) awarded Oujé-Bougoumou honourable mention in a competition for housing innovations in the category of "Technology and Production."
• In 1995 the United Nations Association awarded the community the "Global Citizen" award in recognition of Oujé-Bougoumou having built a community which was both environmentally and people-friendly.

System description

In 1992 the community installed a 1,200 kW biomass boiler from KMW Energy of Ontario and a 1,500 kW oil-fired standby and peaking boiler. The biomass boiler was also fitted with a back-up oil-fired burner. The distribution system consisted of 600 metres of steel pipe and approximately 2,300 metres of plastic pipe. Pipe sizes varied from 108 mm down to 32 mm. The first years construction included 40 residential units and 5 public buildings.

The energy system, district heating pipes and energy transfer stations that were installed in 1992 cost approximately $1.3 million. The boiler plant and main distribution lines were designed to accommodate the growth of the community expected during the first 5 years.

The village expanded and by the year 2000 the system was connected to 89 detached homes, 11 duplexes, 11 four-plexes and 17 public buildings. By that time, the system consisted of two wood-fired boilers and two oil-fired boilers for back-up and peaking.

Sawdust is purchased for $6/tonne and residents pay $192, on average, every two months for their heat and hot water.

Lessons learned

• The use of local labour must be maximised to build competence and reduce installation costs and time.
• The relatively short construction season in a northern location makes careful planning critical.
• Construction can be slowed significantly when a few critical parts or tools are missing. It is important that spare parts and all tools are transported to the site.
• The building of the community should be planned to avoid empty lots.

The big picture

When a community is built or expanded a district energy system should be considered. With a central energy production plant, biomass and other renewable technologies can provide base load energy and thus be utilised more efficiently. These system can also take advantage of variable utility rates better and include technologies, such as heat storage, that are not suitable for smaller loads. District heating and central boiler plants incorporating renewable energy systems have been built around the world and have proven to be reliable and cost-effective.

Photo

Community - District heating - Oujé-Bougoumou, Quebec, Canada

References

Meloche, Nathalie, "Personal communication," CANMET Energy Diversification Research Laboratory, 2000.

Natural Resources Canada, Buyer's Guide to Small Commercial Biomass Combustion Systems, 2000.

Oujé-Bougoumou - The Place Where People Gather, Website: http://www.ouje.ca/expo2000/index.html.

Snoek, Chris, "Personal communication," CANMET Energy Technology Centre (CETC), 2000.

Ziegler, Urban, "Personal communication," PEMtec, 2000.