Hydrogen: A Storage Means for Renewable Energies

Among electricity storage technologies candidates, hydrogen production from electrolysis presents interesting features. It is a suitable technology to renewable energy sources as it can adapt its power consumption to available input power. It also offers the advantage to be a fully scalable technology allowing systems in the range of a few kilowatts to several tenths of megawatts. Unlike most storage technologies (batteries, flywheels, etc.), electrolysis allows to separate the charging power and the stored energy which can be of a great interest when designing a system with contrasted power and energy needs. When produced by electrolysis from renewable energies, hydrogen can be considered as a low carbon footprint energy carrier and can also be used in several industrial applications which grant electrolysis with multiple opportunities of valorisation. The connection to renewable energy sources, due to their intrinsic properties, is imposing challenging operating modes to electrolysis systems. Intermittency, variability and voltage characteristics introduce increased complexity in electrolysis systems to allow frequent start‐stop operation, dynamic behaviour and power adaptation. This complexity is often detrimental to system efficiency especially at low power load. A few demonstration projects have highlighted difficulties in managing the intermittency at system design and operation levels. Experimental feedback dedicated to intermittent operation from these demonstrations is still limited but it has appeared that control system remains a key component for such complex systems as it drastically impacts efficiency. However, even though further research needs to focus on the improvement of dynamic operation, system efficiency across the entire load curve, reliability of stack, power electronics, balance of plant and lifetime it seems that no absolute technology barriers impede the integration of electrolysis with renewable energy. From a techno‐economic point of view, even though improvements on components and system costs (capital and operation) must be addressed to reinforce the competitiveness of electrolysis, new business models can emerge multiplying the potential valorisation of hydrogen. To evaluate these opportunities, modelling and simulation become critical to properly assess the economic viability of each business case in order to favour integration of hydrogen production by electrolysis with renewable production sources.