Power and Water-Saving Advanced Hybrid Air/Wet Cooling System

Given reduced water supplies in arid regions of California, obtaining water permits for air conditioning and refrigeration condenser cooling use in commercial and industrial buildings is becoming a challenge. Water can be saved by driving users to dry-only cooling systems, but at a higher consumer cost. A hybrid system that operates dry most of the time and wet only when ambient air temperatures are high is one way to reduce water use and control capital costs since dry operation at low air temperatures requires a smaller condenser. However, with conventional heat exchanger technology, wet and dry operations require high air-fan power. An advanced hybrid heat exchanger (AHHEX) developed and tested meets the requirements of reduced water use and lower fan power. It operates efficiently when dry and only uses water for cooling at high temperatures. Under this project, a prototype hybrid condenser was designed, fabricated, and integrated with an available 10-ton chiller; performance data was collected over a range of ambient air temperatures. These test results were used to determine the power, water, greenhouse gas, pollutants, and cost-reduction benefits of AHHEX. Water and electric power reductions of up to 2.1 million gallons per year and 28,499 kilowatt hours per year would be expected for a 170-ton cooling system with a constant cooling load. Relative to the total potential California commercial and industrial markets, assuming a 20 percent market share, water and electric power savings from this technology would be 290 million gallons per year and 3.7 million kilowatt hours per year. Greenhouse gas emissions, methane emission and nitrogen oxides would be reduced by 994 tons, 30,316 pounds and 1,278 pounds per year, respectively. The AHHEX can also be applied to utility power systems and yield 25 times the benefit achieved for commercial and industrial systems.