Date of Graduation
Bachelor of Science in Chemical Engineering
Silicon wafer fabrication facilities require a significant amount of temperate cooling water to meet high internal cooling loads. The tertiary chilled water systems operate year round to fulfil the constant cooling load needed for production. Conventional chillers require a large amount of electricity to cool the water by the vapor compression cycle. As energy costs increase and environmental stewardship becomes the norm in industry, sustainable technologies are needed to chill process cooling water without the significant energy consumption of today’s chillers. Night sky radiation cools a medium by radiating heat from a warm medium to the colder night sky. The Intel silicon wafer manufacturing facility in Rio Rancho, New Mexico was selected to be an ideal location for the implementation of two full-scale designs. Numerous system designs were examined during a thorough literature survey, and an open water system was chosen as the best alternative because of its superior heat transfer ability and lower construction cost. At the suggestion of an external auditor, a closed system was studied further, designed, and economically analyzed. Recommendations for system choice are based on economic analyses, system operability, and environmental considerations. To aid in model construction and full-scale design, an extensive research program was developed to confirm literature correlations and determine the effectiveness of radiation to the night sky as a method used to cool water. Experiments that cooled an aluminum plate through the ambient temperature were used to confirm and verify the accuracy of Berdahl and Martin’s correlation for calculating the effective temperature of the night sky. A prototype for the open water system was built to demonstrate the cooling ability of the design. Operation of the prototype successfully demonstrated radiative night sky cooling, showed the benefit of convective heat transfer when the ambient air temperature is below the water temperature, and validated Berdahl and Martin’s model. With the experimental stage complete, the prototype system was scaled-up to a system for the Intel facility in Rio Rancho. The system diverts cooling water from Intel’s cooling water system into surge tanks. From the surge tanks, water is pumped up to the roof and is distributed among corrugated metal roofing units placed on top of the Intel central utilities building. The corrugated panels are supported by a pressure treated lumber frame. The chilled water isdistributed and collected by a PVC piping network. Model simulations of the full-scale system determined the cooling capability of the system. The full-scale simulation predicted that the system would eliminate over 90% of the night-time chiller cooling loads during the winter. Throughout the year, the chillers use $280,000 worth of electricity1. The radiative cooling system will save the company $75,000 in annual electricity costs, a decrease in electricity consumption of 27%. The electricity generation portfolio of PNM, Intel’s electricity provider, was used to determine that the system will prevent approximately 930 tons of carbon dioxide from being released into the atmosphere. The reduction of produced electricity will also conserve 4,220,000 gallons of water, a scarce resource in the southwestern Unites States. For the open system, the total capital cost is $353,500 and the operating cost, including electricity to operate the unit, is $31,600/year. For the closed system, the total capital cost is $636,500 and the operating cost, including electricity to operate the unit, is $12,000/year. The average net reduction in annual electrical usage is 1,282 MW-hr and the average yearly electrical cost savings is $75,265 for both systems. The payback period for the open and closed systems are estimated to be 4.77 years and 6.8 years, respectively. The radiative cooling system will economically benefit the Intel facility; however, the reduction in carbon emissions and water usage is of immense importance to the public and a company as dedicated to environmental initiatives as is Intel.
Enderlin, A. R. (2015). Radiative Cooling to the Night Sky. Chemical Engineering Undergraduate Honors Theses Retrieved from https://scholarworks.uark.edu/cheguht/62