Strategies for Controlling Blue and Green Hydrogen Flow Rate for Optimal Integration

Hydrogen production through autothermal reforming with carbon capture and storage (ATR-CCS) is often considered more reliable and scalable than renewable energy-based hydrogen production, especially when intermittent sources struggle to provide a constant power supply. However, ATR-CCS presents challenges related to the cost and complexity of carbon capture and storage, as well as dependence on fossil fuels, limiting its long-term sustainability. It also requires significant infrastructure and a large amount of energy, which can impact its efficiency and profitability in regions aiming to reduce carbon emissions.
Hydrogen production through renewable energy electrolysis faces obstacles due to intermittency. For instance, solar production varies with temperature and cloud cover, wind energy is unpredictable, and marine sources (waves, tides) present fluctuations, although tidal energy is more predictable. Biomass energy is more stable but depends on raw material availability, while geothermal energy, though stable, can experience variations due to operational issues or resource availability.
Proton exchange membrane water electrolyzers (PEMWE) and alkaline electrolyzers are well-suited for renewable energy sources, as they adjust well to rapid energy supply variations. PEMWE use an electric current to split water into hydrogen and oxygen, offering high hydrogen purity due to a solid polymer membrane. However, they are more expensive and sensitive to impurities in the water. Alkaline electrolyzers, developed earlier and more robust, are less responsive to energy variations but provide a stable solution when energy supply is consistent. They are less expensive in the long run and suitable for large-scale installations.
However, these sudden or irregular variations in energy supply present several technical challenges. First, when energy supply changes abruptly, the temperature inside the electrolyzer can exceed optimal levels (thermal spike) or fall below them (thermal dip), potentially damaging internal components and reducing the overall efficiency of the electrolysis process. Moreover, after an energy fluctuation, the system takes time to stabilize its temperature and pressure, leading to irregular hydrogen production and efficiency losses. These challenges require the use of advanced control strategies capable of real-time regulation of key system parameters (such as current, voltage, and temperature), accounting for different energy fluctuation scenarios (progressive or abrupt). Unlike traditional control systems (simple thermostats or Proportional-Integral-Derivative “PID” control), these approaches (such as model-free control, H-infinity, or optimized PID) ensure better responsiveness and accuracy, guaranteeing stable efficiency even with fluctuations, thereby reducing temperature overshoots and speeding up the stabilization time for electrolyzers. For example, model-free control reduces temperature overshoots and accelerates stabilization time by at least 15 minutes for alkaline electrolyzers.