## 3 Recent Trends in Hydrogen Storage: Gas, Liquid, Solid
### Current Hydrogen Storage  
The various types of hydrogen storage systems now in use are depicted in Figure 15[68; 69]. Compressed gas and cryogenic liquid are the two types of hydrogen \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Technology** & **Pros** & **Cons** & **Ref** \\ \hline Gallium–Aluminum-Composite & 1. & Concentration of gallium in the composite. & \\
1. & The use of gallium–aluminum composite enables hydrogen production from water at room temperature. & 2. & Provides control over the hydrogen output. \\
2. & Eliminates the need for high temperatures or additional energy sources. & 3. & Availability and cost of gallium can pose challenges for large-scale implementation. \\ Gallium–Aluminum-Composite & 3. & This technology is applicable to various water sources, including wastewater, commercial beverages, ocean water & 4. & Cost associated with extracting and utilizing gallium in the composite may affect economic viability. \\ Gallium–Aluminum-Composite & 3. & This technology is applicable to various water sources, including wastewater, commercial beverages, ocean water & 5. & Further research is needed to assess: \\
4. & Offers versatility and accessibility in hydrogen production. & 2. & Scalability and practical implementation on a larger scale. \\
5. & Provides control over the hydrogen output & 3. & Feasibility of integrating sound wave-assisted electrolysis systems into existing infrastructure. \\  & 1. & & \\  & 2. & & \\  & 3. & & \\  & 4. & Addressing potential challenges and limitations. \\  & 5. & Further investigation required to ensure \\  & 1. & Enables decentralized hydrogen generation through a hydrogen panel. & 1. & Further research and development required to optimize efficiency and scalability of Solhyde technology for large-scale deployment is needed in three key areas: panel durability, cost-effectiveness, and integration with existing infrastructure. \\ Solhyde & 4. & Results in lower operational costs and reduced environmental impact compared to conventional electrolysis methods. & deployment is needed in three key areas: panel durability, cost-effectiveness, and integration with existing infrastructure. \\  & 5. & Hydrogen panel can be installed in homes, enterprises, and communities. & 1. & \\  & 6. & Allows for decentralized hydrogen production. & 1. & \\  & 7. & Promotes energy independence. & 1. & \\ \hline \hline \end{tabular}
\end{table} 
Table 3: _Cont._storage that are most often used. In various shapes, sizes, and capacities, metal or composite cylinders or tanks are used to store compressed hydrogen gas. Often, the gas is compressed to pressures between 350 and 700 bar, requiring a significant amount of energy. High pressures also put a strain on container materials, which can lead to wear and failure over time. Cryogenic liquid hydrogen is stored at very low temperatures (\(-253\)\({}^{\circ}\)C) in specially designed containers that minimize heat transmission. Although this method has a higher energy density than compressed gas, cryogenic storage and transportation systems are complicated and costly. Additionally, the danger of asphyxiation and frostbite makes it crucial to handle and store cryogenic liquids carefully. Chemical storage in metal hydrides, chemical hydrides, and ammonia are further hydrogen storage possibilities being considered. These technologies have the potential to offer higher energy densities and lower operating pressures than compressed gas storage, but they also come with their own set of technical and financial difficulties [70]. Hydrogen storage containers necessitate the use of robust materials that can resist high pressures while also preventing leaks. In the design of hydrogen storage tanks, materials including metals, polymers, and carbon fibers are frequently employed. Composite materials have played a significant role in the development of the green hydrogen and ammonia industry. One application of composites in this industry is in the construction of pressure vessels used for storing hydrogen and ammonia.