Central at Garden City District Energy System Mini-Plant

Project Highlights

The City of Richmond retained Kerr Wood Leidal Associates Ltd. (KWL) to design and administer construction of the Central at Garden City District Energy System Mini-plant.  The project includes a central heating and cooling plant powered by low-carbon air-source heat pumps (ASHPs) that provide heating and cooling to 284,000 sq. ft. of new retail space.  This project reduces greenhouse gas (GHG) emissions by reducing natural gas use by up to 70% compared to conventional alternatives.

Central at Garden City District Energy System Mini-plant is Phase 4 expansion of the Alexandra District Energy Utility (ADEU), the largest ambient heating and cooling district energy system in North America.  The overall goal of the system is to reduce the City of Richmond’s carbon footprint.  Phase 4 was developed to meet the unique needs of Central at Garden City shopping mall, while also integrating with the main ADEU system, which is based on geoexchange technology.  Since retail buildings require significantly larger cooling and less heating capacity than surrounding residential buildings, the KWL team designed a ‘mini-plant’ to satisfy these load conditions while remaining within cost-of-service targets.  The plant’s energy source is a bank of ASHPs which were selected as the energy source due to their highly efficient operation, since they run on BC’s low-carbon electricity supply and offer heating and cooling capabilities, including heat recovery.

Unique System Features

This project is the first district energy system in Canada to provide heating and cooling to large-format retail buildings using ASHP technology and has several unique features. Buildings at Central at Garden City can share energy through the central heating and cooling mini-plant.  Additionally, an energy transfer station links the mini-plant to the main ADEU system, allowing the ASHPs to back-feed the entire Alexandra neighbourhood and share excess cooling energy or heat captured from the outside air with the larger neighbourhood or recharge the geoexchange loop.  Few, if any, district energy systems in Canada use multiple low-carbon heating and cooling sources, which adds to the project uniqueness.

Responsive Operating Modes

From a process perspective, the on-site distribution system can be configured in multiple operating modes depending on site conditions.  During the coldest weather conditions, where outdoor air temperature is less than -1 °C (less than 5% of hours/year for an average year), ASHPs cannot operate, hence high-efficiency boilers provide the development’s heating requirements.  When outside air temperature is above 5 °C, the ASHPs can provide all the development’s heating requirements.  From spring to fall, the heat pumps can provide simultaneous heating and cooling to the site.  The cooling pipes can also be switched to a low-temperature heating mode to feed the ADEU system with the ASHPs while the boilers provide on-site heating.  This extends the range of the ASHP operation and reduces gas use in the surrounding neighbourhood.  A complex instrumentation and control scheme was developed to enable remote operation and monitoring of the fully automated mini-plant.

“This is a very innovative implentation of district energy to reduce CO2 emissions and address climate change. This type of energy storage could be the way of the future.” Jury, 2017 Canadian Consulting Engineering Awards

Resources:
Article: Canadian Consulting Engineer magazine (application/pdf, 0.678Mb)