Chillers and Energy Savings
ENERGY SAVING FACT SHEET
Introduction
Central building cooling options include water chillers and direct-expansion (DX) A/C units. Chillers use a refrigeration cycle to cool water to 42º F to 55º F for pumping to chilled water cooling coils. Air is then blown over the chilled water cooling coils to provide cool air to the conditioned space. DX systems also use a refrigeration cycle, but distribute refrigerant directly to DX cooling coils – some are packaged in a single housing, others are split (evaporator coil remote to condenser and compressor). High-efficiency chillers can produce chilled water using less than 0.50 kW per ton of cooling capacity. A refrigeration system must also reject the heat that it removes using a cooling tower for water cooling the condenser (most efficient) or using fans for air cooling the hot refrigerant of the condenser coil.
Chiller Performance Facts
Chillers consume more than 50% of electrical energy during seasonal periods of building use. More than 120,000 chillers in the U.S. are expending more than 30% in additional energy through operational inefficiencies. (Estimated by DOE survey) Water cooled condenser water (cooling tower) temperature decrease of 1ºF can increase efficiency of the chiller compressor by 1% to 2 % in most situations; however, there is a limit and optimum lower condenser temperature for a given partial loading of the chiller compressor. A neglected or poorly maintained cooling tower can reduce chiller efficiency by 10% to 35% and a dirty coil condenser of an air cooled chiller as much as 5% to 15% Chemical cleaning of the inside of the condenser and evaporator heat transfer surfaces can result in a 5% to 10% energy savings – kw/ton Air-cooled chillers are less efficient than water-cooled chillers but cost less as well. to determine, with today 's chiller machines this instantaneous input (kw)/(ton) output relationship. Most have a control panel that looks at all of the motor drives connected kw for
Introduction
Central building cooling options include water chillers and direct-expansion (DX) A/C units. Chillers use a refrigeration cycle to cool water to 42º F to 55º F for pumping to chilled water cooling coils. Air is then blown over the chilled water cooling coils to provide cool air to the conditioned space. DX systems also use a refrigeration cycle, but distribute refrigerant directly to DX cooling coils – some are packaged in a single housing, others are split (evaporator coil remote to condenser and compressor). High-efficiency chillers can produce chilled water using less than 0.50 kW per ton of cooling capacity. A refrigeration system must also reject the heat that it removes using a cooling tower for water cooling the condenser (most efficient) or using fans for air cooling the hot refrigerant of the condenser coil.
Chiller Performance Facts
Chillers consume more than 50% of electrical energy during seasonal periods of building use. More than 120,000 chillers in the U.S. are expending more than 30% in additional energy through operational inefficiencies. (Estimated by DOE survey) Water cooled condenser water (cooling tower) temperature decrease of 1ºF can increase efficiency of the chiller compressor by 1% to 2 % in most situations; however, there is a limit and optimum lower condenser temperature for a given partial loading of the chiller compressor. A neglected or poorly maintained cooling tower can reduce chiller efficiency by 10% to 35% and a dirty coil condenser of an air cooled chiller as much as 5% to 15% Chemical cleaning of the inside of the condenser and evaporator heat transfer surfaces can result in a 5% to 10% energy savings – kw/ton Air-cooled chillers are less efficient than water-cooled chillers but cost less as well. to determine, with today 's chiller machines this instantaneous input (kw)/(ton) output relationship. Most have a control panel that looks at all of the motor drives connected kw for
References: & Resources: 1. Manufacturers; Trane, York, Carrier, McQuay, 2. ASHRAE Journal /www.ashrae.org/ 3. Air-Conditioning and Refrigeration Institute (ARI) , www.ahrinet.org Sponsored by the State Energy Office, N.C. Department of Administration and the U.S. Department of Energy, with State Energy Program funds, in cooperation with the Land-of-Sky Regional Council (Waste Reduction Partners) and the NCDPPEA However, Land-ofNCDPPEA. any opinion, findings, conclusions, or recommendations expressed herein are those of the author(s) and do not necessarily reflect the views of either the N.C. Department of Administration or the U.S. Department of Energy. An online version of this fact sheet is available at: www.wastereductionpartners.com and www.energync.net Revised by Waste Reduction Partners— 05/2010