MS, University of Cincinnati, 2021, Engineering and Applied Science: Mechanical Engineering

In effort to both save operating expenses and be environmentally friendly, thermal energy storage provides a means for companies to handle daytime HVAC requirements while using off-peak (nighttime) electrical power. This paper sets out to compare three of the most common techniques used for thermal energy storage, by comparing both the analytical modeling of their energy storage and actual experimental data for their energy storage, using the same exact test apparatus for each of the techniques. The results of this experiment show that using normal HVAC temperatures, sensible water chilled to its maximum value after only about two hours, while PCM would take nearly six hours to achieve “linkage,” or solidified material merging between the helix coils. Ice building, done with -7° coolant, took 4.5 hours to achieve linkage. Initial heat transfer was proportional to the difference between initial tank temperature and the coolant temperature, and went asymptotically towards zero for sensible as the temperature of the tank and coolant reach equilibrium. For ice, the heat transfer rate was always more than twice that of PCM during latent storage, which is attributed to the difference between coolant temperatures and freezing points for the respective materials. Sensible water cooldown would require 232.8% of the tank volume to store the same energy relative to the environment compared to ice building, and 126.3% of the tank volume compared to phase change material. This is to be weighed with the benefit of using existing HVAC condensing units to chill the water, and the fact that water itself is inexpensive. The high latent heat of freezing for water meant it held more energy than both the water sensible cooldown and PCM freezing, but with the downside of requiring medium temperature condenser units in order to be efficient (instead of the high temperature units used in typical HVAC). After 4.5 hours, PCM would surpass the energy stored in the same volume as water sensi (open full item for complete abstract)

Committee: Michael Kazmierczak Ph.D. (Committee Chair); Ahmed Elgafy Ph.D. (Committee Member); Sang Young Son Ph.D. (Committee Member) Subjects: Mechanical Engineering

Doctor of Philosophy, The Ohio State University, 2023, Civil Engineering

Satellite gravimetry (Gravity Recovery and Climate Experiment (GRACE)) detects spatiotemporal gravity variations resulting from mass changes in the cryosphere and hydrosphere. However, it is confronted with challenges, such as limited spatial resolution (approximately 330 km) and signal leakage at the ocean–land interface. This study employs alternative satellite geodesy methods providing higher spatial resolution than typical methods. Accordingly, they enable more detailed analysis for exploring mass changes in the Greenland Ice Sheet (GrIS) and fluctuations in terrestrial water storage (TWS) across the United States. In the context of ice melting studies, satellite radar and laser altimetry deliver precise measurements of surface elevation changes (SECs) with spatial resolutions ranging from a few hundred meters to several kilometers. This enables a thorough investigation of variations in individual glaciers. Additionally, the continuous Ku-band radar altimetry missions allow for the generation of SEC time series dating back to 1992. However, the previous methods are incapable of incorporating data contributions from neighboring grids, potentially introducing biases or artificial signals. To resolve this problem, an innovative Kalman filter integration method is developed. The resulting monthly SEC product offers unprecedented accuracy. Furthermore, a stochastic filter is employed to estimate time-dependent rates instead of relying on constant rates over specific periods. Complex patterns of acceleration and deceleration in SEC have been observed across various ocean-terminating glaciers. Notably, the GrIS did not experience significant mass loss from 1995 to 2000. However, before 2000, the melting of GrIS began to accelerate, with the most severe melting occurring from 2011 to 2013, especially along the western Greenland coastal areas. Subsequently, ice melting gradually decelerated until 2017; however, it accelerated again in 2019–2020. Presently, the GrIS is (open full item for complete abstract)

Committee: Lei Wang (Advisor); Gil Bohrer (Committee Member); Michael Bevis (Committee Member) Subjects: Civil Engineering