The Enwave Deep Lake Water Cooling (DLWC) System is an innovative cooling system that provides an alternative to conventional air conditioning to cool 140 buildings in Toronto’s downtown core. The Enwave DLWC System provides cooling to some of Toronto’s largest office buildings, saving more than 61 Mwh of electricity annually. This reduction in energy usage and green house gas emissions is equivalent to taking 15,800 cars off the road for a year.
The idea for DLWC dates back to 1982 when the Canada Mortgage and Housing Corporation presented results of a study describing ‘the concept of pumping water from the bed of Lake Ontario through a hydraulic heat transfer system to cool major downtown buildings.’ In 1987, TDH, the company that would eventually become Enwave, opened the chilled water plant in the south building of the Metro Toronto Convention Centre. In 1992, the design of phase II of DLWC was finalized, with plans to expand the chilled water distribution system north to serve a larger section of the downtown core.
The expansion project called for the addition of 16 new pumps to draw the lake water and serve the heat exchangers. Armstrong Vertical In-Line Pumps were selected because they are a high efficiency, low maintenance solution for commercial cooling. The vertical in-line orientation reduces the need for floor space, and allows operators to maintain mechanical seal without removing the motor, or disturbing shaft alignment.
To meet the specific flow and head requirements of the project, Armstrong designed a new size of the existing 4300 Vertical In-Line pump. Sixteen new 16×16×15 Vertical In-Line pumps with custom impellers and 350-horsepower motors were installed to provide high flow rates (10,000 gpm) at low head (86 feet). In addition to the 16 VIL pumps, 15 additional pumps were installed for the domestic water system and the distribution of chilled water around the city buildings.
Toronto’s Deep Lake Water Cooling system has become an example of efficient, renewable, clean cooling.
The DLWC system:
• Eliminates 79,000 tonnes of carbon dioxide annually
• Eliminates the need for 45,000 kg of polluting cfc
• Eliminates 145 tonnes of Nitrogen Oxide
• Eliminates 318 tonnes of Sulphur Oxide
Because the DLWC concept was still new at the time, design engineers could not foresee the actual operating conditions of the pumps. It later turned out that the system flow requirement was forcing the pumps to operate at a duty point that was substantially different from the originally specified performance curve. Responding to the customer’s request, Armstrong redesigned the pump impellers for higher pressure, lower flow operation. With that correction in place, the pumps have operated flawlessly since 1992, with very few maintenance requirements.
The choice of Vertical In-Line pumps reduced the installed cost by more than $120,000 and reduced the 5-year maintenance costs by over $3,500.
The DLWC system saves more than 61 Mwh of electricity annually – the equivalent power demand of 6,800 homes. This reduction in electricity demand relieves the pressure on an over-burdened electrical grid in the downtown core and eliminates the need to install expensive cooling equipment in each of the 140 buildings served.