Combining Renewable Sources Towards Negative Carbon Emission Hydrogen

Multi-energy systems that combine different energy sources and carriers to improve the overall technical, economic, and environmental performance can boost the energy transition. In this paper we posit an innovative multi-energy system for green hydrogen production that achieves negative carbon emissions by combining bio-fuel membraneintegrated steam reforming and renewable electricity electrolysis. The system produces green hydrogen and carbon dioxide, both at high purity. We use thermo-chemical models to determine the system performance and optimal working parameters. Specifically, we focus on its ability to achieve negative carbon emissions. The results show that in optimal operating conditions the system can capture up to 14.1 g of CO2 per MJ of stored hydrogen and achieves up to 70% storage efficiency. Therefore, we prove that a multi-energy system may reach the same efficiency of an average electrolyzer while implementing carbon capture. In the same optimal operating conditions the system converts 7.8 kg of biogas in 1 kg of hydrogen using 3.2 kg of oxygen coming from the production of 6.4 kg of hydrogen through the electrolyzer. With such ratios we estimate that the conversion of all the biogas produced in Europe with our system, could result in the installation of additional dedicated 800 GWp - 1280 GWp of photovoltaic power, or of 266 GWp - 532 GWp of wind power, without affecting the distribution grid and covering yearly the 45% of the worldwide hydrogen demand while removing from the atmosphere more than 2% of the European carbon dioxide emissions.