Numerous researchers suggest utilizing renewable energy to replace fossil fuels, which have limitations and contribute to pollution. Renewable energy sources are boundless and do not generate pollution during their operation. However, the use of renewable energy is hindered by certain restrictions. These sources are only accessible in specific locations, and some, like solar and wind energy, are unpredictable and cannot offer a continuous supply of energy. To surmount these challenges, renewable energy sources can be modified by integrating them with hydrogen production systems.
Hydrogen has multiple benefits over other energy carriers and can be stored and transported, thereby resolving the challenges linked with renewable energy sources. Electrolyzers that use water, currently under development, are particularly promising because they can harness intermittent clean energy sources such as wind, tidal, and solar power to produce hydrogen from an infinite water source.
Currently, there are some types of electrolyzers on the market, the most common ones are proton exchange membrane (PEM)electrolyzers and alkaline water electrolyzers (AWE) technology, both of which have drawbacks such as the utilization of raw materials or low yields. Recently, anion exchange membrane (AEM) electrolyzers technology has been proposed to overcome the limitations of the existing systems. AEM could be a technology that combines the benefits of AWE and PEM electrolyzers, even though many technological aspects of AEM have not yet been achieved, particularly those related to durability and hydroxide conductivity.
In this thesis, a combined system Wind-to-Hydrogen with AEM technology has been analyzed. The electrical input for the devices is obtained from a wind farm that includes ten wind turbines connected to a central hub, in which one AEM and one PEM electrolyzers are positioned. The first two electrolyzers enable the hydrogen production, while the third one is responsible for its electrochemical compression up to 200 bar. Subsequently, a prototype of under-water compressed air energy storage system (UWCGES) with a total capacity of 50 000 m3 was adopted.
The storage system is essential in order to use hydrogen in future. Depending on the application of the system itself, different functions of this energy carrier can be defined.
Considering that the aim of the thesis is limited to production only, as the coupling with intermittent sources and a new technology such as the AEM electrolyzer is analyzed in detail, several potential applications for hydrogen are nevertheless proposed.
Hydrogen will be available for a variety of uses as it is a versatile fuel, useful to diversify the fuel mix, and, if produced from low-carbon sources, to support the transition to a cleaner energy system:
• In the industry: nowadays, hydrogen is used for oil refining (33%), ammonia production (27%), methanol production (11%) and steel production (3%) and more than 60% of the hydrogen used in refineries is produced from natural gas. With this type of technology, it will be possible to purchase green hydrogen produced only by renewable sources [1].
• In the marine field: green hydrogen could be adopted as fuel for ship propulsion.
• Power to mobility (P2M): According to the source, for heavy vehicles that need to store a large amount of energy and have quick recharge rates, like long-haul trucks, buses, and hybrid trains, hydrogen is currently the most effective non-fossil fuel option.