An experimental and techno-economic assessment of solar reforming for H2 production

Abstract

Steam reforming of natural gas is a ubiquitous industrial process which is well suited to solar-thermal integration due to its high energy requirement. To date, however, the high temperature required (800–900 °C) and inherent intermittency of the solar resource has hindered the deployment of solar reforming as a means of producing H2. Lowering the reforming temperature to <600 °C through use of a membrane reformer increases efficiency of reforming and solar heat collection, and allows integration with thermal energy storage, thereby potentially allowing 24/7 operation. As the first step towards assessment of a hybridized solar reforming plant, a prototype membrane reforming system, featuring a 4-tube membrane reformer and pre-heater, was fabricated and tested. The solar input was simulated by using hot air as a heat transfer fluid. With a commercial reforming catalyst and a 0.5 m-long, Pd-based membrane in each tube, a feed flow of 4 lN/min of methane was converted at a rate of 70%, with an H2 yield as high as 95%. A techno-economic analysis shows that the membrane reformer along effectively increases the plant cost by ∼1.5× relative to conventional technology, but with the advantage of ∼15% reduction in natural gas consumption and a significant reduction in the levelized cost of H2, even without any solar heat input. Solar integration provided modest gains in efficiency, but these were offset by significantly higher capital costs. Expected future decreases in the cost of Pd-based membranes and concentrated solar thermal technology will further enhance the economic case for this technology.