Supercritical CO2 Binary Mixtures for Recompression Brayton s-CO2 Power Cycles Coupled to Solar Thermal Energy Plants

Paul Tafur-Escanta,Luis Coco-Enríquez,Javier Muñoz-Antón,Robert Valencia-Chapi,Ignacio López-Paniagua

doi:10.3390/en14134050

Paul Tafur-Escanta, Luis Coco-Enríquez + Show 3 more

Open Access

https://doi.org/10.3390/en14134050

Copy DOI

Abstract

In this work, an evaluation and quantification of the impact of using mixtures based on supercritical carbon dioxide “s-CO2” (s-CO2/COS, s-CO2/H2S, s-CO2/NH3, s-CO2/SO2) are made as a working fluid in simple and complex recompression Brayton s-CO2 power cycle configurations that have pressure drops in their components. These cycles are coupled with a solar thermal plant with parabolic-trough collector (PTC) technology. The methodology used in the calculation performance is to establish values of the heat recuperator total conductance (UAtotal) between 5 and 25 MW/K. The main conclusion of this work is that the cycle’s efficiency has improved due to using s-CO2 mixtures as working fluid; this is significant compared to the results obtained using the standard fluid (pure s-CO2). Furthermore, a techno-economic analysis is carried out that compares each configuration’s costs using pure s-CO2 and a mixture of s-CO2/COS with a molar fraction (70/30), respectively, as working fluid where relevant results are obtained. These results show that the best configuration in terms of thermal efficiency and cost is the RCC-RH for pure sCO2 with values of 41.25% and 2811 $/kWe, while for the mixture sCO2/COS, the RCC-2RH configuration with values of 45.05% and 2621 $/kWe is optimal. Using the mixture costs 6.75% less than if it is used the standard fluid (s-CO2).

Highlights

In response to the increase in electrical energy needs and climate change globally, solar energy has become the fundamental pillar of the renewable energy market
Supercritical carbon dioxide (s-CO2 ) Brayton power cycles have been identified as a suitable candidate for next-generation concentrated solar power plants (CSP) (CSP Gen3) applications as they can operate at higher temperatures achieving increased thermodynamic performance [3,4,5]
CO2 as working fluids in Brayton power cycles. They mention that it has been shown that mixing CO2 -N2 O4 and CO2 -TiCl4 can increase efficiency above 49%, assuming an inlet temperature to the turbine equal to 700 ◦ C, which achieves at the same time a reduction of the complexity and costs of the power block

Summary

Introduction

In response to the increase in electrical energy needs and climate change globally, solar energy has become the fundamental pillar of the renewable energy market. In order to reduce costs and improve the economic viability of solar thermal energy power plants (STE), researchers have focused on increasing the operating temperature, testing new heat transfer fluids (HTF) and cycles of power, thereby increasing system efficiency. In this sense, supercritical carbon dioxide (s-CO2 ) Brayton power cycles have been identified as a suitable candidate for next-generation CSP (CSP Gen3) applications as they can operate at higher temperatures achieving increased thermodynamic performance [3,4,5]. Various configurations of the s-CO2 Brayton cycles (simple, recompression, recompression with main compression intercooling and partial cooling) are currently under study [6,7,8,9,10].

Objectives

Methods

Findings

Discussion

Conclusion