Analysis of indirect power cycles for a novel methanol-to-methane TCES-CSP system

Abstract

The security of the supply of clean energy resources and the production of renewable fuels for industry are some of the strategies to combat climate change. In this sense, the massive implementation of green fuels that is foreseen forces the industrial park to operate on hydrogen and/or ammonia, methanol and others, with a cost overrun for stakeholders. This work proposes an alternative through a methanol-to-methane conversion system from the intermediate step to synthesis gas. Methanol decomposition is a process that can be produced with solar energy (CSP) at moderate temperatures (<350 °C) and at low cost, whereas methanation is a well-known and industrially mature process that occurs at temperatures < 625 °C. The integration of both processes is employed as a method of solar storage, namely through high-pressure syngas and its discharge for power production in conventional cycles. Recuperative ORC configurations, Rankine steam, and a sCO2 Brayton cycle were integrated; all of them of techno-economic interest, offering round-trip efficiencies higher than 50 % and levelized costs (LCOE) lower than EUR 55/MWh, considering a high-energy methane stream at the outlet. This offers a system that proposes a solution for the massive deployment of methanol as a green hydrogen carrier molecule, where it is capable of cleanly and efficiently storing thermochemical energy and producing high-purity methane at the output, usable in other power cycles, or as an industrial feedstock.