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NATURAL GAS COOLING High Efficiency Alternative to Conventional Electric Cooling OPTION 1: NATURAL GAS ENGINE-DRIVEN COOLING Commercially proven vapor-compression (engine-driven) cooling systems from 25 to 4,000 tons cooling capacity are available today. These include engine-driven cooling systems suitable for commercial or industrial use. FEATURES & BENEFITS Benefits relative to conventional electric chillers include: • Lower operating cost • Release of electrical capacity for other applications • Supplemental heat source DEFINITION Engine-driven systems are cooling systems in which a natural gas-fueled reciprocating internal-combustion engine, often driving a screw compressor, replaces the traditional electric motor as the energy source. The screw compressors respond well to variable speeds and have good turndown ratios—which improve engine efficiency under part-load conditions. Centrifugal rather than screw compressors may be used in larger systems. INTRODUCTION Engine-driven systems are cooling systems represented by a thermodynamic cycle in which the refrigerant is compressed, cooled at constant pressure, condensed, and throttled in the conventional vapor-compression refrigerating cycle. The natural gas-fueled compressor engine is the energy source. HOW ENGINE-DRIVEN SYSTEMS WORK The traditional vapor-compression cycle The diagram on the right illustrates the vapor-compression refrigeration cycle. Shaft work is supplied to the compressor by either an electric motor, natural gas engine, or turbine. Refrigerant vapor is thus compressed to higher pressure (and temperature). The vapor must condense to liquid at this higher pressure and temperature. Because the temperature is greater than ambient, heat is rejected from the system and flows into ambient air. Vapor Compression Schematic The high-pressure liquid then passes through a throttling valve that reduces its pressure, which reduces its boiling point to approximately 40˚F at design conditions. The lowpressure liquid then passes into the evaporator and is boiled or vaporized at this lower temperature and pressure. Because the boiling temperature is now lower than the temperature of the conditioned air, heat moves from the conditioned air stream into the evaporator and causes the liquid to boil. Removing heat from the air in this manner cools it, fulfilling the purpose of the vapor-compression cooling system. LOCAL INSTALLATIONS Customer Carriage House Hockey Outlet Wilson Greatbatch Equipment Energen Technologies Energen Technologies Tecochill Size (HP) 250 150 300 ENGINE-DRIVEN CHILLER VENDORS • Carrier Corp. • Century Corp. • Energen Technologies • McQuay International (Sanyo) • Tecochill • Trane Co. • York International Corp. Page 1 of 2 Location Fredonia Wheatfield Clarence OPTION 2: NATURAL GAS ABSORPTION COOLING Commercially proven absorption cooling systems of from 3 to 1,700 tons cooling capacity, throughout the residential, commercial and industrial cooling capacity ranges, are available today. FEATURES & BENEFITS Benefits of absorption cooling include: • Lower operating cost • No ozone-damaging refrigerants—only water required • Safer, quieter operation • Lower-pressure or vacuum systems; no large rotating components • Less space required than electric chiller with separate boiler • Higher reliability • Lower maintenance DEFINITION Absorption systems are cooling systems where a refrigerant is allowed to evaporate due to its physical property of having an affinity for an absorbent. It is during this evaporation process where heat is also absorbed, thereby creating a cooling effect. Once the absorbent becomes saturated with refrigerant and can absorb no more, the solution needs to be separated or regenerated, so that it may be used again. Direct heat from a natural gas flame or indirect heat in the form of steam can be used to regenerate the absorbent and refrigerant solution. The heat absorbed during this process is then rejected in the condenser, along with the heat that was absorbed during the evaporation process (see diagram below). INTRODUCTION Absorption cooling systems represent a thermodynamic cycle that is driven by heat energy rather than by mechanical energy. Absorption chillers are either lithium bromide and water (LiBr/H2O) or ammonia and water systems. The LiBr/H2O system uses lithium bromide as the absorber and water as the refrigerant. The ammoniawater system uses water as the absorber and ammonia as the refrigerant. HOW ABSORPTION SYSTEMS WORK The single-effect absorption cycle Absorption chillers operate on the principle that some materials will absorb others—even when both are in liquid form. For example, ordinary table salt (sodium chloride) pulls water vapor out of the air, absorbing it and making the salt damp, coagulated, and hard to pour. For absorption cycle purposes, lithium bromide water solution, a liquid that absorbs water vapor, is used. A major difference between the conventional vapor compression cycle and the absorption cycle is the refrigerant used. Chlorofluorocarbons (CFCs) have been the most popular refrigerants for mechanical refrigeration systems for decades; however, distilled water is an adequate refrigerant in most large commercial absorption systems. Unlike mechanical compression systems, absorption cycles need a second fluid, lithium bromide water solution, which is non-toxic. Because lithium bromide (the absorbent) does not boil, water (the refrigerant) is easily separated from it by adding heat. Two variations of the absorption cycle that are more efficient and effective in certain conditions are the Double-Effect and Generator Absorber heat eXchanger (GAX) absorption technology. LOCAL INSTALLATIONS Customer Canisius College Mod Pac Equipment Hitachi York ABSORPTION CHILLER VENDORS • Carrier Corp. • Century Corp. • Hitachi • McQuay International (Sanyo) Size (Tons) 250 200 • • • • Location Buffalo Buffalo Servel (Robur Corp.) Trane Co. Yazaki Energy Systems, Inc. York International Corp. FOR FURTHER INFORMATION • National Fuel Gas Distribution Corp., 6363 Main St., Williamsville NY 14221-5887; phone (716) 857-7776 or http://www.nationalfuelgas.com/. • Energy Solutions Center Inc. 400 N. Capitol St., NW, 4th Floor, Washington DC 20001; phone (202) 824-7150; or http://www.energysolutionscenter.org/ NATIONAL FUEL STATEMENT At National Fuel, we believe in providing information on natural gas technologies, enabling our customers to make informed decisions on their energy needs. This information covers existing technologies, new technical developments, emerging breakthroughs in energy use, and energy-saving ideas still in development. Page 2 of 2