Continuous hydrogen production and supply Integrated system operation with electrolytic production, storage and supply

Green Hydrogen Supply System in Maximized Simultaneous Generation and Storage Associated with use on demanding various gases, such as natural gas, methane, carbon dioxide, hydrogen, etc., are stored under pressure, requiring high levels of this variable for greater accumulations, which are limited according to the nature and characteristics of the gaseous medium.

Developments have sought alternatives to increase storage levels by raising pressure or maintaining the same level under lower pressures. In both cases, there is an impact on the choice of reservoir material, ensuring the same resistance or using reservoirs with lower resistance and reduced costs.The introduction of porous solid materials inside the reservoirs allows for significant increases in the stored volumes of gases. When adsorbed on the total surface of the solid, more gas volume occupies the reservoir at the same pressure.

The need to store gases, whether available or in production, for direct or later use, under accumulation, has motivated the development of reservoir systems with efficient adsorbent materials for storage.Hydrogen, produced and separated from water by electrolysis, supplied electrically by a solar source, is compressed and stored in a reservoir filled with adsorbent.

The use of MOF material allows the storage of this gas at a level approximately 50% greater in volume, compared to the accumulation made by compression in a cylinder without adsorbent.Considering the electrolytic production of H2, which is exhaustive in electricity, its simultaneous generation and supply when demand arises makes the process the most suitable. For this, a supply accumulator reservoir filled with MOF proves efficient.

In the present development, an optimized hydrogen generation, storage, and supply system is characterized by including:

- Solar electrical source;

- Electrolytic production;

- Storage by compression and adsorption;

- Simultaneous release by decompression and desorption.

Solar energy with lower electricity costs involved in water electrolysis is only needed during the use demand, whose generated H2 is compressed and stored at a higher level. In the system, the gas accumulates advantageously by adsorption and is simultaneously released on demand. Internal heat transfer occurs in the reservoir, ensuring superior accumulation and high release of the gas. In conclusion, this proposal outlines a groundbreaking reservoir system designed to utilize efficient adsorbent materials for gas storage, particularly hydrogen.

By integrating an adsorbent reservoir device, the system not only facilitates the generation and storage of hydrogen but also ensures its immediate availability for use. Operating under solar energy input and leveraging electrolysis, this innovative approach maximizes gas accumulation, achieving a storage capacity that is 70-84% greater than that of conventional reservoirs.

Considering the operation of a 1.4 kW electrolyzer producing 300 NL/h, during 24 h, a 340 L reservoir is filled with 1.08 kg of H2, maintained at 35 bar. Under these pressure conditions and at room temperature (300K), using the reservoir filled with 62 g of MOF, it is possible to store 1.14 kg H2/reservoir, representing an increase of 5.5%wt.

In the production conditions of the electrolyzer (solar source), integrating it into a new system to improve storage, making H2 available for immediate and continuous use, the coaxial system is used with adsorbent MOF contained in the two reservoirs, contiguous and concentric. In this case, 1.22 kg/reservoir can be stored, representing an increase of 13.2%wt. The co-axial system is schematized in Figure 1, consisting of two concentric cylinders with the same reservoir volume available for H2 storage. Each reservoir is filled with an equal mass of MOF adsorbent. The outer cylinder has thermal insulation.?

The system operates by supplying the external reservoir with H2 produced in the electrolyzer, compressed to 35 bar. At the same time, the gas contained in the internal reservoir (35 bar) is decompressed and released for supply (1.5 bar). At the end, a second cycle begins, filling the internal reservoir and supplying H2 from the external cylinder.

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