AWARD OF EXCELLENCE / NATURAL RESOURCES, MINING, INDUSTRY & ENERGY Alexandra District Energy Geothermal System
Juror Comments: "Well integrated into a growing community, this project makes possible a large reduction in greenhouse gases that is a model for future projects."
Juror Comments: “Well integrated into a growing community, this project makes possible a large reduction in greenhouse
gases that is a model for future projects.”
Recognizing the benefit of a district energy system in advancing towards a more sustainable community, the City of Richmond engaged Stantec Consulting to design the Alexandra District Energy Utility (ADEU) geothermal system.
Having started operating in July 2012, the system currently provides space heating, cooling and domestic hot water, serving over 400 residences as well as a daycare.
The system provides a safe, clean and reliable energy source, while reducing greenhouse gas emissions. The system is currently reducing up to 750 tonnes of greenhouse gas emissions annually, and reducing our dependency on non-renewable energy sources.
Due to Richmond’s beneficial geology and tidal effected high water table, ADEU’s vertical closed-loop geothermal district system is expected to be significantly more energy efficient and cost-effective than most other geothermal systems. As a result, the system can meet the client’s mandate of ensuring that end users will pay equal or lower rates for heating and cooling than they would using a conventional system. And since the utility is self-financing, no cost will be incurred by taxpayers.
Massive geo-exchange field
The ADEU system extracts energy from the ground using a network of 385 boreholes, each 76 metres deep, drilled in a massive geo-exchange field beneath a city greenway corridor. Using this greenway corridor provides the community with multiple benefits: open green space and an energy source.
From the geothermal field, 1.3 km of 500-mm high density polyethylene supply and return mains distributes water to the energy centre and to the connected buildings. Inside each building an energy transfer station monitors the heating and cooling requirements and modulates the flow of water from the utility. Heat pump units in each building elevate the water temperatures for heating, or reject heat into the ADEU system for cooling.
During the peak heating season, the system operates at a minimum supply temperature of -1°C with a 6°C temperature drop. During the peak cooling season the system will operate at a maximum supply temperature of 32°C with the same 6°C temperature rise. The flow rate is carefully managed to ensure that pump energy is not wasted by circulating water when it is not required. A 1.0 MW condensing, gas-fired boiler is used as a back-up energy source for the geothermal system, as well as providing supplemental heating at peak loads.
Achieving scale was critical
The system is designed to allow future phases to use different renewable energy sources such as open and closed loop geo-exchange systems, solar thermal, biogas and sewer heat recovery. Initially the system is operating without any antifreeze. The loop temperatures is being monitored and logged, and in the event that temperatures approach freezing, glycol can be added.
The entire utility is controlled by an automated DDC system that allows the city to monitor the energy use and consumption recovery rate.
Achieving scale was critical, so a service bylaw that makes hook-up to the ADEU mandatory secured the customer base to support the long-term investment business case. Working with developers and owners prior to construction allowed for them to immediately connect to the district system, which was essential to reducing their upfront in-building equipment cost and long term maintenance costs.
It is estimated that at build out, ADEU will achieve a reduction of up to 6,000 tonnes of GHG emissions annually, which is equivalent to removing approximately 2,000 cars off the road each year. cce
Alexandra District Energy Geothermal System, Richmond, B.C.
City of Richmond
Other key players:
Hemmera Envirochem (concept design); Compass Resource Management (prefeasibility study); Barnett Dembek (architecture); H.Y. Engineering (civil); Weiler Smith Bowers (structural); GeoPacific (geotechnical).