Session: 17-05: Symposium Steinfeld - Concentrated solar power and thermal/thermochemical energy storage

Paper Number: 142446

142446 - Barium Peroxide/ Barium Oxide Redox Based Thermochemical Energy Storage in a Lab-Scale Packed-Bed Reactor 

Abstract: 

Concentrated solar power (CSP), photovoltaic (PV), and wind power are in use worldwide for electricity generation. One major disadvantage of solar and wind renewables is that they are intermittent. Thermochemical energy storage (TCES), where the reactions can be driven by a solar furnace or an electric furnace powered by PV or wind, is a promising and attractive approach for renewable energy storage to accommodate intermittency due to its high storage density, high operating temperature, and minimal heat loss over a long period. The high-quality heat output from the chemical reaction can be released on demand and used through a heat exchanger for space heating, hot water heating, or for electricity generation through a power block. This work presents the design, modeling, and testing of a lab-scale packed-bed reactor with BaO₂/BaO pellets undergoing reduction-oxidation (redox) cycling, i.e., BaO₂ + heat ↔ BaO + ½ O₂. The material availability, low capital cost, moderate heat storage capacity (474 kJ/kg), moderate redox temperatures (550-980°C) and stable redox reactions are the key points for implementing the BaO₂/BaO redox pair in this work. The reactive materials were prepared by mixing 15 wt% MgO with 85 wt% BaO₂ for enhanced stability and longevity. In the present experimental setup, for the charging step where BaO₂/BaO-based pellets (~ 320 g) were thermally reduced around T_reduction ~ 850°C, the required heat was provided by a fibrecraft electric furnace under oxygen partial pressure of 0.2 bar. For the discharging step where the pellets were oxidized around T_oxidation ~ 600°C with the same oxygen partial pressure. Temperature-dependent thermophysical properties are considered in the reactor heat transfer model as the operating temperature of the present reactor ranged from 25 °C to 850 °C and the published kinetics for the BaO₂/BaO redox pair was used for reaction kinetics modeling. In this present packed-bed TCES reactor design, oxygen is the mobile reactant which enables effective operation under high-pressure air, and the direct heat transfer between high-pressure air and the packed bed eliminates the need for heat exchangers. Experimental results from six consecutive redox cycles are reported which shows great cyclability over the entire period of about 30 hr. The numerical results were validated with the experimental results in terms of bed temperatures, O₂ concentrations, chemical conversions, and rate of chemical energy storage. On average, about 60 W of chemical energy was obtained from the experiment conducted by using 318.5 g pellets and about 95% conversion was achieved for the redox cycling. The current computational model and lab-scale experimental study will be helpful for future reactor design and scale-up investigations, as well as for operating parameters optimization to maximize reactor round-trip efficiency.

Presenting Author: Like Li University of Central Florida

Presenting Author Biography: Like Li is an Associate Professor in the Mechanical and Aerospace Engineering Department at the University of Central Florida. Prior to that, he was Associate Professor and Assistant Professor at Mississippi State University. He received his Ph.D. in Mechanical Engineering from the University of Florida in 2013. He leads the Thermal Energy Storage and Decarbonization (TESD) Lab focusing on advanced energy storage technologies research, development and demonstration (R&DD) to contribute to the transition to a clean and decarbonized energy future. His group has received funding from federal agencies and industries including the NSF, DOE Solar Energy Technologies Office, NASA, and Tennessee Valley Authority (TVA). The current research in his group focuses on fundamental understanding of gas-solid reactions and thermal/chemical transport in complex materials and reactors, characterization of particle flow properties at high temperature, and thermochemical reactors design, development, and demonstration for solar and other renewable energy storage and utilization.

Authors:

Mahbubur Rahman University of Central Florida
David Korba Mississippi State University
Jian Zhao Mississippi State University
Nick Auyeung Oregon State University
Like Li University of Central Florida