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Biomass-based Urban Central Heating Demonstration

Lead proponent:  SSQ, Société immobilière inc.
Location: Québec City, QC
CEF contribution:  $ 4.7 M
Project total:  $ 13.3 M

Project Background:

Boiler plant housing

Boiler plant housing four Viessmann Pyrotec KPT-1250 wood-fired boilers.

There are very few properties in the Quebec City core large enough to accommodate the construction of a new housing development.  In 2005, SSQ Financial Group (a Quebec-based insurance, investment/retirement and real estate services institution) acquired a 93,000 m² parcel of land in the Saint-Sacrement district from the Congrégation des Soeurs du Bon-Pasteur de Québec.  On this site, SSQ planned the construction of La Cité Verte – the first large-scale, multi-residential project in Quebec comprised of green, intelligent buildings.  More than 800 housing units would be constructed and intermingled with community features such as green spaces, stores and services (7,000 m2 of commercial space) to encourage pedestrian movement and social interaction.  A number of the existing historical buildings would be preserved and designated for restoration

Moreover, SSQ aspired to equip La Cité Verte with the most advanced biomass district heating system in North America for its space heating and domestic hot water needs.  To that end, the Clean Energy Fund contributed $4.7M to the “Biomass-based Urban Central Heating Demonstration” project to evaluate the performance and efficiency as well as to determine the financial and technical feasibility of the system in climatic conditions prevalent in the Quebec City surrounding area.


At the heart of La Cité Verte’s heating system is a boiler plant housing four Viessmann Pyrotec KPT-1250 wood-fired boilers (each rated at 1,250 KW) in a 5 MW cascade system. The cascade arrangement provides maximum boiler plant efficiency with high turndown ratio (1:16) that precisely matches load.  A 5.2 MW natural gas boiler provides emergency backup for the biomass boilers, and a 650 KW diesel generator will ensure continuous operation of the entire district heating system in the event of an electric power failure.

The boilers heat two 22,000 L buffer water tanks before the heated water (90 °C supply/50 °C return) is distributed through a highly efficient, low temperature hydronic heating network for district DHW and space heating.  A 2.2km pre-insulated underground piping system takes the heated water to row houses and other buildings throughout the site.  Substations in each Cité Verte building distribute the appropriate amount of heat and calculate fuel bills for the individual units. Water flow throughout the network is driven by a 25 HP pump in the winter and a 5 HP pump during the summer, when space heating requirements are significantly reduced.

A Viessmann boiler control system integrated seamlessly with Smart Heat Network controls developed by Regulvar and project engineers Génécor and Poly-Énergie. The integrated system monitors energy consumption data collected from individual units and district substations along with boiler data, in order to optimize efficiency throughout the district.

The biomass heating system went online in October 2011.  The Pyrotec hot water boilers met their published performance ratings for combustion efficiency (up to 85%).

Benefits to Canada:

When completed, La Cité Verte will use 30% less total energy than conventional developments. A successful demonstration will confirm the technical feasibility of urban central heat production using a renewable energy source and encourage the deployment of the same or similar technologies across Canada.

Next Steps:

SSQ Real Estate will remain the operator of the system up until March 31st, 2019.  Operation of the power plant and network will continue to be monitored and its performance monitored.  New buildings will be connected to the existing underground network of piping as they are built.

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