[ solar coupling ]
Fig. 1. Overview of three off-grid solar hydrogen architectures.( a) Method 1: DC solar power is inverted to AC, transmitted via a private HV microgrid, then rectified back to DC for the electrolyzer.( b) Method 2: large DC / DC converters retain DC to match electrolyzer voltage.( c) Method 3( XINTC): eliminates power electronics entirely, enabling deep turndown ratios( 1:120).
used to prevent unwanted current feedback to the solar panels. This is made possible by the multicore architecture of XINTC’ s electrolyzer system, which uses 120 modular building blocks – pairs of 10 kW electrolyzer stacks, known as gas modules – collectively forming a 1.2 MW system. Each pair operates independently, enabling turndown ratios as low as 1:120 at the module level. This approach allows highly modular scaling, simplified integration, greater flexibility in decentralised deployment, and direct reduction of CAPEX and OPEX associated with power electronics.
These architectures are illustrated in Fig. 1. They highlight the trade-offs between centralization, complexity, and cost, with direct DC coupling and modularity offering promising directions for future off-grid hydrogen production systems.
System-level losses in off-grid solar electrolysis
Peak-power shaving PV systems often produce peak power for a short time during the day( e. g. around noon). Conventionally, solar panels are oversized relative to the inverter’ s AC capacity. This results in periods, typically during high irradiance conditions, where the DC power output exceeds the inverter’ s maximum conversion capacity. By undersizing the inverter, it operates closer to its nominal capacity for a longer portion of the day. However, excess DC power above the inverter’ s capacity is‘ clipped’ during peak times. This situation applies to methods 1 and 2 discussed in this article. For cost reasons related to power electronics, peak shaving is typically set at around 70 – 80 % of the PV field’ s peak power. 7 This is also referred to as curtailment loss.
It is important to note that electrical efficiency is primarily determined by the performance of the AC / DC or DC / DC converters, which operate most efficiently at their nominal operating point( i. e., nominal current). Their efficiency decreases at partial loads, which frequently occurs due to fluctuations in solar power availability.
When green hydrogen production is the objective, significant cost reductions and gains in hydrogen output can be achieved by eliminating or minimizing the number of power electronic components in the solar field. Power inverters in conventional solar systems account for about 10 % of the capital expenditure and require more maintenance due to their shorter lifespan of approximately eight years, compared to the 20 – 25-year lifetime of the solar panels.
16 Hydrogen Tech World | Issue 22 | June 2025