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Commercial gas consumption could be 25 percent higher in 2020. Today, 3 quads of gas are consumed annually in the commercial sector. Under the assumptions of the accelerated projection, consumption could increase
to 5.5 quads by 2020, roughly 25 percent above the current projection of 4.4 quads. The more aggressive scenario reflects continued success in space and water heating and in food-service establishments as well as significant growth in the markets for commercial cooling and various forms of distributed generation.
Natural gas accounts for more than 40 percent of commercial energy consumption. The commercial sector includes office buildings, schools, hospitals, hotels, restaurants, malls and other retail establishments. Energy consumption in the commercial sector totals about 7.7 quads annually, including 3.1 quads of natural gas, slightly less than the commercial consumption of electricity. The primary commercial sector uses for energy are space heating (36 percent), lighting (19 percent), cooling (12 percent), water heating (8 percent), cooking (6 percent) and drying (3 percent). Gas is dominant in the space and water heating, cooking and drying segments. Gas now also accounts for 13 percent of the commercial cooling market.
Commercial gas cooling has multiple applications. A number of gas cooling products are making inroads in the marketplace. The three basic types of gas cooling equipment are engine-driven chillers, absorption chillers and desiccant dehumidifiers. Engine-driven chillers use a gas engine rather than an electric motor to drive a compressor. These systems are particularly attractive because they offer the option of recovering waste heat that can be used to generate hot water or steam. Sales of commercial gas engine-driven chillers jumped from 7,000 tons in 1994 to almost 50,000 tons in 1996.
Absorption cooling produces a cooling effect by evaporating a refrigerant. These systems, which use water or ammonia rather than a synthetic refrigerant, commonly are used to cool large commercial buildings such as hotels, offices and hospitals. The number of heat exchanger "stages" of absorption systems can be increased, thereby increasing system efficiency. Double-stage absorption systems increase efficiency by 50 to 60 percent compared with single-stage systems. Triple-stage systems currently under development offer potential savings of an additional 50 percent over those of the double-stage systems.
Gas-based desiccant dehumidification systems reduce humidity in commercial establishments, thereby reducing the energy required for cooling. When humid air is cooled, about half the energy of conventional cooling systems is actually used just to dry the air. Desiccants dry the air prior to cooling. The clean, dry air produced by desiccants can eliminate frost buildup in the frozen-food section of supermarkets, reduce airborne spores and bacteria in hospitals, prevent mold and mildew problems in hotels, and improve indoor air quality in offices and retail establishments.
The government hopes to double combined heating and power by 2010. Almost all energy-related processes waste some energy, often
in the form of heat. Sometimes this energy can be captured and used for other processes. The capture and use of energy that otherwise would be wasted ultimately leads to conservation of our energy resources and also reduces the environmental impacts that stem from energy production, transportation, conversion and use. Combined heat and power (CHP) and combined cooling, heating and power (CCHP) refer to integrated systems that can provide these multiple products with one energy input, usually natural gas.
Natural gas is ideally suited for CHP and CCHP applications. Heat released by gas power generators or engine-driven chillers can be used to run cooling equipment such as desiccant dehumidifiers or absorption chillers, or to run space or water heaters. The energy efficiency of these systems is being recognized by building managers seeking to reduce energy costs and by government officials with environmental objectives. For example, the Assistant Secretary of Energy Efficiency and Renewable Energy of the U.S. Department of Energy has challenged industry to double CHP capacity by 2010. He sees similar prospects for CCHP.
Distributed generation is available for a variety of commercial establishments. CHP and CCHP are both forms of distributed generation that have multiple energy products. However, other forms of distributed generation offer a single output-electricity-that is produced on-site. Reciprocating engines, turbines and fuel cells can all be used to generate electricity at commercial sites. These options offer increased freedom from power disruptions, consistent high-quality electricity and control over the energy supply.
The movement of distributed generation technologies into the commercial sector is a natural evolution. Related technologies have prospered in the industrial sector for decades. Over time, units have become smaller and more efficient and reliable. Whereas the economic threshold for standalone turbines 20 years ago may have been 20 megawatts, today's microturbines use 30 or fewer kilowatts. Thus, today we see not only turbines the size of a house providing electricity to an industrial facility, but also engines or turbines the size of a refrigerator meeting the electricity needs of fast food restaurants and drug stores. Such evolution will inevitably continue.
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