Methanol and ammonia as emerging green fuels: Evaluation of a new power generation paradigm

In the current context of the energy transition, the use of liquid fuels is attracting attention to be used as energy storage, due to the inherent fluctuations of the main renewable energy sources. In addition, these liquid fuels have also been proposed as energy carriers, to introduce renewables in hard-to-electrify applications. Methanol and ammonia emerge as the two most promising green liquid fuels for energy purposes. In this work, a systematic assessment of the transformation of methanol/ammonia into power is performed. Two different routes have been studied: thermochemical (through fuel combustion) and electrochemical (using fuel cells). From a technical analysis, the methanol process reaches the highest efficiency, around 38%. In general, thermochemical processes show better performance in terms of energy efficiency. From an economic perspective, the current costs of the thermochemical route are around 0.3 €/kWh and 0.6-1 €/kWh for the electrochemical. Electricity cost is expected to be reduced as process efficiency increases down to values of around 0.1 €/kWh. A progressive introduction of these green liquid fuels will be necessary to achieve a 100% renewable energy system in all areas, guaranteeing the long-term sustainability of the planet.