Alexandra District Energy Utility
The City of Richmond retained Kerr Wood Leidal Associates to design the Phase 3 expansion of the Alexandra District Energy Utility (ADEU), which is the largest ambient heating and cooling district energy system in North America. It uses ground heat as an energy source and has an ultimate capacity of 13.4 megawatts of heating and 5.8 megawatts of cooling for 3.1 million square feet of space (or 3,100 residential and commercial units). Running at full capacity, it is estimated to offset 1,300 tonnes of carbon equivalents annually.
This project has won several awards including the 2016 System of the Year Award from the International District Energy Association (IDEA).
ADEU Phase 3 included the design, PLC programming, onsite commissioning, and on-going support of the electrical, instrumentation and control (EIC) systems.
Challenges in this project included designing a control system that was implemented in two separate stages, and incorporating the existing EIC systems in to the new EIC systems.
This facility is unique among district energy plants in that KWL chose to implement an “industrial grade” control system; commercial grade systems are the norm.
How it Works
The district energy system derives its heating and cooling energy from three sources: geoexchange fields, natural gas boilers, and cooling towers. Two geoexchange fields exchange heating and cooling with the earth by gathering renewable heat from 25 kilometres of buried pipe. Natural gas boilers provide back-up heat, and two cooling towers use ambient air and evaporation to provide peak cooling during the summer season. The ambient system also allows for cooling heat recovery and energy sharing between buildings: when one building is rejecting heat into the network, another connected building, in need of heat, can make use of it.
The plant expansion was completed in two fully functional stages to meet seasonal heating and cooling needs. The first stage provided cooling capacity for the summer season, allowing existing customers to enjoy the benefit of cooling during the summer of 2015, the hottest summer on record for North America. The second stage saw the continuation of a second geoexchange field and back-up boilers for the winter season.
The building, located in a park, is constructed of locally manufactured, cross-laminated timber panels that act as structural members and limited the use of high-energy building materials, such as carbon steel and concrete. Its appealing design includes an extensive use of windows that invites the public to view how local homes and businesses are heated and cooled. A green roof provides many benefits such as mitigating the ‘urban-heat-island effect’, improving air quality, reducing storm water flows from the roof and into the City’s storm sewers, and improving building cooling particularly in the summer months.