Evaporative Cooling for a Growing Southwest: Technology, Markets, and Economics

摘要

The Southwest is growing rapidly—a 37% increase in population is projected from 2000 to 2020 versus 16% for the total US. This is placing great pressures on an electric grid that must meet this new demand, much of which is caused by compressor-based air conditioning, a technology increasingly becoming the norm in both the residential and commercial sectors. Yet the region's climate is ideally suited for evaporative cooling, both because of its low humidity and large diurnal temperature swings. Lower front end costs and substantially lower energy and demand costs continue to characterize evaporative cooling systems as new sensors and controls coupled with longer-life, more-efficient, and easier-to-maintain equipment for the residential and commercial sectors have become available in the marketplace. Both compressor-based cooling and evaporative cooling systems are becoming more efficient, but on a Btu-of-cooling-per-kWh-of-electricity basis, modern evaporative cooling systems are at least four times more efficient and demand is less by a factor of four or more. This paper examines: ? The range of new technologies and trends in upgrading existing technologies in evaporative cooling; ? The cost-effectiveness of evaporative cooling versus compressor-based cooling; ? The market status of evaporative cooling in the Southwest and barriers to penetration; and ? Recommendations for promoting evaporative cooling systems in all sectors, including ongoing programs in the Southwest. The stakes are high. Assuming a penetration of high-efficiency evaporative coolers in efficient new homes built in the Southwest between 2000 and 2020 reaches 40% by the end of 2020, we estimate that savings (versus SEER 13 air conditioning units) in the year 2020 will be 4,228 GWh of electric energy and 2,874 MW of peak demand savings. This will avoid the need for building four 700 MW power plants. Since incremental costs versus conventional air conditioning are negative, paybacks are instantaneous. However, water use must also be taken into account. High-efficiency residential evaporative coolers use an average of 5,100 gallons of water per year in the Southwest, about 3% of average annual residential water use. This amount of water costs $5 to $20 per cooling season. However, since evaporative coolers save on the order of 3,200 kWh per year, about 1,600 gallons of water are saved at the power station, for a net water use of 3,500 gallons. Net dollar savings for new homeowners are $254 per year.