Deciphering high-efficiency solar-thermochemical energy conversion process of heat pipe reactor for steam methane reforming

Abstract

• Solar-thermochemical conversion mechanism for the reactor was revealed. • The maximum solar-thermochemical conversion efficiency is 41% • The heat conduction is the prime heat transfer mode in the reactor cavity. The high temperature heat pipe reactor (HTPR) driven by solar energy via steam methane reforming opens up a new avenue to produce hydrogen as aviation fuel with low carbon emission. Herein, the energy conversion and transfer process of steam methane reforming in the HTPR was disclosed by experiments and simulations. Firstly, the solar to thermal conversion and the heat transfer process in the start-up stage of the HTPR were investigated. The solar thermal response was immediate, and the reactor temperature difference was merely about 30 °C from top to bottom, providing a uniform thermal boundary for the steam methane reforming reaction. Then, the thermochemical conversion performance of the HTPR was unveiled. Despite the uneven energy flux on the HTPR outwall, it still provided a uniform thermal boundary with a temperature of up to 750 °C because of its high thermal conductivity. Furthermore, the solar-thermochemical efficiency of the HTPR was about 41.0% after optimizing the operating parameters, surpassing that of the state-of-the-art solar thermochemical reactor. Finally, the heat loss of the HTPR and the heat transfer mode in the reactor cavity were analyzed. The radiation of the reactor outwall accounted for 44.5% of the total heat loss, and the thermal conduction was the major heat transfer mode in the cavity. This work deepens our understanding of the thermochemical conversion mechanism of the HTPR, paving the way for improving hydrogen yields.