| The purpose of this project is to develop a theory for thermal energy storage systems in confined aquifers which can be utilized at temperatures over 212 F. Operating temperatures in the neighborhood of 400 F are investigated. The theoretical relations developed are verified by experimental data. In this system, energy injection and withdrawal are accomplished by reversing flow through a system of wells connecting the aquifer to the surface. Each well contains a submerged pumping system and controls.; The transfer of thermal energy to the confined aquifer is made with pressurized water injection and withdrawal through a unique system devised by Schaetzle and Ansari('36) and described herein.; Two computer programs have been developed for the proposed system. The first program computes the location of a fluid particle as it moves between the injection well and the withdrawal well for a given period of time. The second program computes the rate of heat transfer within the storage system during injection and withdrawal periods.; Thermal energy injection and withdrawal cycles investigated operate on: (1) a daily basis for night-time energy requirements, (2) a few-day basis for poor weather energy requirements, and (3) an annual basis for lower winter insolation requirements.; The results of the numerical computations indicate that the recovered energy for a 120-ft. thick aquifer is: (1) 97 percent for an unconditioned aquifer, based on a daily cycle; (2) 99.9 percent for a conditioned aquifer, based on a daily cycle; (3) 94 percent for an unconditioned aquifer, based on a few-day cycle; (4) 99.5 percent for a conditioned aquifer based on a few-day cycle; (5) 75 percent for an unconditioned aquifer, based on an annual cycle; and (6) 83 percent for a conditioned aquifer, based on an annual cycle; and that the thermal energy recovered decreases as the aquifer thickness is decreased.; The thermal energy storage system is analyzed in conjunction with a solar power plant system. The storage system provides energy during night time, bad weather, and winter low insolation periods. The power plant system consists of a Rankine steam cycle, a two-dimensional concentrating solar collector system, and the aquifer thermal energy storage system.; The per kilowatt solar plant capital cost is approximately {dollar}10,000/kW. The storage system is only {dollar}40/kW of 0.4 percent of capital cost. Assuming an interest rate of 10 percent, a sinking fund depreciation rate for 20 years with 10 percent interest, and 90 percent utilization, the capital cost per kW-hr. is 14.5 cents. |
