Abstract
Coupling solar thermal energy with the hybrid TC/CG-ES (thermochemical/compressed gas energy storage) is a breakthrough option used to overcome the main challenge of solar energy, i.e., intermittent resource and low density. This paper proposes an innovative storage system that improves the competitiveness of solar thermal energy technologies compared to conventional fossil-based power plants, potentially leading to deep decarbonization of the energy and industrial sectors. This study uses thermochemical energy storage based on the calcium looping (CaL) process and takes advantage of a number of factors: high energy density (2 GJ/m3), absence of heat loss (seasonal storage), high operation temperature (high efficiency of the power plant), and use of cheap and environmentally friendly reactant feedstock (CaO/CaCO3). This work deals with the integration of the solar CaL storage system with an unconventional supercritical CO2 (s-CO2) Brayton cycle. We analyze different s-CO2 Brayton cycle layouts suitable for direct integration with the storage system. Energy integration via pinch analysis methodology is applied to the whole system to optimize the internal heat recovery and increase the efficiency of the system. A parametric study highlights how the integration of solar CaL with an intercooling Brayton cycle shows better results than the combination with the Rankine cycle that we investigated previously, resulting in net and global system efficiencies equal to 39.5 and 51.5%. Instead, the new calculated net and global system efficiencies are 44.4 and 57.0%, respectively, for TC-CG-ES coupled with the Brayton power cycle.
Highlights
The main possible solutions to decouple CO2 emissions from economic growth are (i) switching to a low carbon economy, (ii) increasing system efficiency, and (iii) implementing carbon capture utilization and storage (CCUS) technologies to allow a gradual transition from fossil fuels to other more sustainable or renewable fuels
We have investigated four different configurations of the supercritical CO2 (s-CO2) cycle (Modeling Approach of s-CO2 Brayton Cycle Section), and the best performing one was chosen in Results of the Parametric Analysis Applied to the Power Island Section
The simple regeneration cycle does not depend on the split ratio (SR), but it is reported in the graph to compare all the cycle efficiency
Summary
The main possible solutions to decouple CO2 emissions from economic growth are (i) switching to a low carbon economy, (ii) increasing system efficiency, and (iii) implementing carbon capture utilization and storage (CCUS) technologies to allow a gradual transition from fossil fuels to other more sustainable or renewable fuels. Conventional fuels produce a great quantity of greenhouse gas (GHG) during their combustion. They are limited resources, which translates into a volatile market with daily price changes. Solar energy is one of the most feasible energy sources among all renewable sources because it is low cost and potentially largely available (Islam et al, 2018). One of the most promising technologies is the solar tower power (STP) plant. STP plant consists of many suntracking mirrors (heliostats), which concentrate the solar irradiation onto an absorber, called a receiver, usually located atop a tower. The concentrated radiation is transformed into heat that is transferred by the heat transfer fluid and used to produce electricity. There are many different receiver technologies (e.g., gas, liquid, and solid particle receiver), which work with varying shapes of receiver and heat transfer fluid (Ho and Iverson, 2014)
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