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Cooling - Free cooling - Office - Sea water

Template assignment

Base case

• Cooled floor area for building is 32,550 m²
• Cooling load for building is 35 W/m²
• Non-weather dependant cooling is 70%
• Total peak cooling load around 1,150 kW
• Conventional chiller with a COP of 5.0
• Cooling tower used to reject heat; annually consumes 9 million litres of fresh water costing $2,500 plus $2,000 for treatment
• Electricity rate is $0.065/kWh

Proposed case

• Project located in Halifax, Canada
• Sea water, pumped into building through a short (approximately 250 m) PVC pipe, cools fresh water in a closed-loop building circuit via a titanium heat exchanger, and is then returned to sea
• Sea water enters heat exchanger at 7 to 8°C year-round, exits heat exchanger at temperature 2 to 3°C higher than entering temperature
• Sea water free cooling requires electricity for pumping but has a COP of 30
• Maximum pumping capacity of around 4,000 L/min results in 850 kW of cooling
• Conventional chiller with a capacity of 300 kW used for peak cooling load
• Conventional chiller dumps heat to sea water at 10°C with COP of 6.0 (no cooling towers required)
• Cost of free cooling system plus peak cooling chiller is $200,000 more than cost of conventional (base case) system
• Sea water system requires one less full-time person for operation and maintenance than base case system, saving $49,000 per year in labour
• Chlorine treatment to prevent marine growth in heat exchanger costs $4,500 annually

Solution

The worked-out solution is the data file selected from within the RETScreen Project Database. The user automatically downloads the Project Database file while downloading the RETScreen software.