# Innovative Strategies for Combining Solar and Wind Energy with Green Hydrogen Systems
## 4 Case Studies and Applications
### Case Study 2: Environmental Siting of Hydrogen Production Hubs  
The combustion of hydrogen has proven to be a clean, versatile, and efficient energy carrier (see Equation (3)). \[\mathrm{H_{2}}_{\mathrm{(g)}}+\mathrm{\
u_{2}}\mathrm{O_{2}}_{\mathrm{(g)}}= \mathrm{H_{2}}\mathrm{O_{(Liquid)}}+\mathrm{Energy} \tag{3}\]  
Hydrogen helps in energy generation through fuel cells, direct combustion, and various industrial applications, and hydrogen can produce electricity, provide high-temperature heat, and support a wide range of energy needs without the carbon emissions associated with fossil fuels (see Figure 9). This makes hydrogen a crucial component in the transition to a sustainable and decarbonized energy system. At present, the world consumes around 65 million tons of hydrogen each year, with almost 95% of it produced through carbon-intensive methods. For example, the most common source of hydrogen is by reacting methane from natural gas with steam (CH\({}_{4}\) + 2H\({}_{2}\)O \(\rightarrow\) CO\({}_{2}\) + 4H\({}_{2}\)). Although, a cheaper and well-established process, the release of CO\({}_{2}\) is still a challenge not contributing to the clean energy sustainable goals of 2050. There is therefore a global call for alternative ways for hydrogen production using renewable energy sources. Numerous research studies have explored the performance and cost of hydrogen production using green energy sources like solar and wind. Renewable energy sources such as solar and wind significantly reduce the environmental impact of hydrogen production by powering the electrolysis process, in which water (H\({}_{2}\)O) is split into hydrogen (H\({}_{2}\)) and oxygen (O\({}_{2}\)) using electricity. When this electricity is generated from renewable sources, the hydrogen production process becomes almost entirely carbon-free. However, there is a limited amount of research on the application of renewable energy sources specifically for hydrogen production. Currently, Chile and Argentina, with their world-class variable renewable energy (VRE) resources, have significant potential to become leading producers and exporters of renewable energy stored in hydrogen-rich chemicals. Figure 9: Uses of hydrogen (State of Hydrogen 2022 Report). Comparison of Hybrid Systems in Different Environments  
The setup of hybrid renewable systems at varying environments requires utmost study to achieve potent results when deplored in certain environments. Ref [69] hinted that the location of hydrogen production is a key factor in determining the final cost, as it influences the capacity factor of a plant harnessing renewable energy. Furthermore, factors such as (a) geographical climatic factors, (b) infrastructure and logistics, (c) economic and technical challenges, (d) environmental and land use concerns, (e) technical integration, and many others are great determiners of cost. Herein, we reviewed several case studies that explored the use of solar and wind energy for hydrogen production in rural, urban environments, or in industrial regions. The initial evaluations indicate that Australia ranks among the countries with the greatest potential for green hydrogen production. Currently, Australia has committed to decarbonizing its mineral processing, fertilizer production, and oil and gas industries and utilizing them domestically to produce hydrogen [70]. For example, the Gladstone Hydrogen Project located in Gladstone, Queensland, Australia (an industrial region), invested USD 3 billion in their Electrolyzer Manufacturing Plant, making it one of the biggest hydrogen plants in the world. Gladstone's location is advantageous for hydrogen production, thanks to its established industrial base, port facilities, and access to nearby renewable energy resources. However, one significant challenge in Gladstone is that the capital expenditure, along with operational and maintenance costs for solar and onshore wind energy production in that area, are twice as high compared to hydrogen production from sources like brown coal [71].