[ solar coupling ]
Hydrogen generation at different scales
For large-scale hydrogen production, electrolyzers are typically connected to the electricity grid and operated at a high load factor. In this setup, hydrogen costs are closely tied to grid electricity prices. Achieving competitive pricing usually requires scaling to several hundred megawatts, with a growing trend toward increasingly large grid-connected installations. However, relying on grid electricity presents challenges. Supplying large electrolyzers can strain existing grid infrastructure, often requiring new high-voltage( HV) lines, which are expensive, time-consuming, and visually disruptive. Due to the scale of high-load-factor, grid-connected projects, hydrogen production costs are strongly influenced by the electricity price, E electricity
(€/ kWh). A higher electrolyzer conversion efficiency, η H2 in kWh / kg H2
, clearly leads to a lower Levelized Cost of Hydrogen( LCOH). The LCOH can be calculated from the following equation( see Eq. 1), where CAPEX and OPEX are capital and operational expenditures, and
m H2 is the amount of produced hydrogen.
LCOH =
CAPEX + OPEX
m H2
+ η × E electricity
( Eq. 1)
For smaller-scale or decentralized hydrogen projects, off-grid solar systems offer a promising alternative. They provide greater flexibility in land selection, avoiding the need for existing grid infrastructure and competition with gridconnected PV sites or transmission expansions. Energy transmission via hydrogen pipelines, rather than HV cables, also reduces visual impact and can be more cost-effective at scale. Since hydrogen production in off-grid systems operates at lower load factors and smaller scales than grid-connected projects, the LCOH, as defined in Eq. 1, becomes more sensitive to CAPEX. Thus, minimizing components to only essential equipment can significantly reduce both CAPEX and OPEX, improving cost competitiveness. Lean system design is therefore critical for realizing economically viable green hydrogen production from off-grid solar installations.
Solar coupling methods
In off-grid configurations, several technical architectures are being explored to optimize the coupling between solar PV and electrolyzers. 5 For solar coupling projects, three main methods are emerging, each with distinct characteristics.
Method 1 This approach involves constructing a dedicated high-voltage microgrid, typically in the range of several hundred megawatts. In this setup, electricity generated from the PV panels is first converted from DC to AC using inverters. It is then transported over a private HV line to the electrolyzer site, where it is transformed again and rectified to DC for use by the electrolyzer. While technically mature, this approach adds cost and complexity due to the multiple power conversion stages and infrastructure requirements. 5
Method 2 This method proposes using DC current for the entire field by coupling the PV array directly to the electrolyzer via DC / DC converters. It eliminates the need for inverters and AC infrastructure, resulting in significant CAPEX savings and retaining operation at low- voltage DC levels. However, very large DC / DC converters at multimegawatt scale are not yet widely available. Moreover, DC power cannot be transported efficiently over long distances due to Joule losses and cable sizing constraints, requiring the electrolyzer to be co-located with the PV field. This promotes a more decentralized design and supports modular project development with potential economies of scale. 5
Method 3 Developed by XINTC 6 for multicore advanced alkaline electrolyzer systems, this approach directly couples solar panels to the electrolyzer. It takes direct solar coupling a step further by completely eliminating power electronics between the solar field and the electrolyzer. Only blocking diodes are
Hydrogen Tech World | Issue 22 | June 2025 15