Session: 03-04 Sensible Energy Storage

Paper Number: 105306

105306 - Energy Storage Using a High-Performance Adsorption System Storage Using High-Performance Adsorption System 

Waste heat harvesting is essential to minimize electricity consumption and cost. Thermal Energy Storage systems provide cost-effective, compact and scalable means to store heat compared to other storage systems. However, the current infrastructure of sensible and latent heat storage systems suffers from heat discharge, low energy density, and sluggish charging and discharging, and low energy density, especially those that utilize sensible heat storage. A latent heat storage system, such as a phase change material (PCM) system, improves the energy density and heat discharge at variable temperatures; however, the PCMs encounter various issues, such as segregation for salt hydrates and low thermal conductivity with paraffin wax. Thermochemical systems involving chemical reactions generally require high temperatures for charging through an endothermic reaction. Adsorption-based energy storage systems, when designed for fast charging and discharging, can cater to the needs of the energy storage landscape because they do not require high temperatures for regeneration while maintaining high energy density.

This paper documents the computational modeling of a fast-acting Thermal Energy Storage System employing an adsorbent-coated microchannel heat exchanger and condenser. The use of microchannels results in excellent heat and mass transfer performance of the systems. The heat exchanger consists of a monolithic structure over parallel rows of adsorbent-coated channels and uncoated heat transfer fluid (HTF) channels. The materials used for the simulations are silica gel adsorbent, water adsorbate and stainless-steel monolith. When starting from a saturated adsorbent layer, in the charging process, hot HTF water enters the uncoated microchannels desorbing the refrigerant water quickly to reach the condenser pressure. Then this refrigerant water is delivered to the condenser, which condenses this water vapor, recovering some heat from the refrigerant water, which is used to preheat the HTF during discharging phase.  In the discharging process the preheated water enters the uncoated microchannels, cooling the monolith and the adsorbent. This decreases the pressure adsorbent-coated microchannels, flash boiling the stored water and bringing it back to the adsorbent bed. The heat released during this adsorption of refrigerant water is contributes to the discharging output of the system.

The modeling results on the baseline case show that heat can be recovered at more than 87℃ when inlet charging HTF is at 90℃. For this case, the system volume is computed to be 6.03 liters at at an energy density of 31.67 kWh/  and a specific energy recovery of 0.2 kWh/kg-ads, which is 33% and at least 7 times higher than the standard PCM systems. The charging time in which all the heat is supplied is 60 s and the discharging time in which the heat at 87℃ can be recovered through the cold fluid through the HTF channel is 372 s highlighting the fact that this system can store energy quickly when it is available, and then returns it uniformly and for longer duration when it is required. Using both Stainless Steel and Copper as the base material for monolithic wall showed similar results which indicates that the thermal resistance is very low for microchannel which makes the heat transfer process very fast despite using lower thermal conductive material such as stainless steel. Lowering the velocity of the cold HTF during discharging process increased the thermal efficiency and recovery temperature. Further optimization of the operating parameters (velocity and condenser pressure), dimensions and materials are required to get the best performance for energy storage applications. Better adsorbent materials such as MOFs can yield better results.

In sum, this energy storage system provides an environmentally friendly, compact and rapid approach to discharge heat at competitive recovery temperatures, which can be used for domestic water heating, space heating, industrial process heating etc.

Presenting Author: Darshan Pahinkar Florida Institute of Technology

Presenting Author Biography: Darshan joined Florida Tech as an assistant professor of Mechanical Engineering in the Department of Mechanical and Civil Engineering in Spring 2020. He is the principal investigator of the Adsorption and Energy Technology Lab (AETL) at Florida Tech (https://research.fit.edu/pahinkar/). His research focuses on developing scalable and sustainable energy conversion and storage systems using computational and experimental techniques, characterizing integral fundamental transport phenomena, and demonstrating their practical applications. He advises three Ph.D. and three M.S. students, who lead research on various topics based on these energy systems.
Before this appointment, Darshan received his B.E. in Mechanical Engineering from the Government College of Engineering, Pune, India, in 2006 and his M.E. in Mechanical Engineering from the Indian Institute of Science, Bangalore, India, in 2009. For the next two years, he worked as a Manager (Development) in Tata Motors Engineering Research Center, Pune, and his work involved thermal management of automobiles. Darshan graduated with a Ph.D. in Mechanical Engineering from Georgia Tech in the fall of 2016. He was a post-doctoral fellow at Georgia Tech Electronics Manufacturing and Reliability Laboratory before joining Florida Tech.