[ solar coupling ]
power to its maximum. As discussed earlier, this requires power electronics, which adds to both CAPEX and OPEX, and introduces curtailment losses as well as system sizing challenges and complexities.
In Fig. 3b, the operating method developed and implemented by XINTC is illustrated. In this system, the electrolyzer consists of 120 pairs of gas modules, dividing the total capacity into 120 discrete steps. Each active module pair defines a potential power curve, offering 120 available intersections with the solar power curve at any given moment. By adjusting the number of active modules, the system can continuously track the maximum available solar power. Effectively, the optimizer function is replaced by control software.
Location dependence of losses
This section provides a detailed analysis of how much of the generated solar power is potentially lost depending on the location and solar configuration type. As an illustrative example, an analysis is performed for Taragona, Spain. Solar irradiance data are adopted from the PVGIS website ¹¹ on an hourly basis. Curtailment and threshold losses are
calculated for a Typical Meteorological Year( TMY) at that location, also on an hourly basis. However, the results are presented on a monthly basis by summing the daily values and organizing the data accordingly, as shown in Fig. 4.
In Fig. 4a, monthly energy production is shown for method 3, as implemented by XINTC. A threshold loss of 10 kW is assumed for the electrolyzer, corresponding to the nominal power of a single pair of gas modules. It is clear that usable power, after accounting for threshold losses, is only marginally affected compared to the total solar energy produced by the solar panels.
In Fig. 4b, monthly energy production for a system corresponding to method 1 is calculated, accounting for:( 1) curtailment losses only and( 2) curtailment and threshold losses combined. The inverter efficiency model is based on NREL’ s PVWatts calculator.¹² The rectifier model assumes a linear ratio between 95 – 98 % for loads above 20 % of its nominal load, and an efficiency of 90 % for loads below 20 %. For a single electrolyzer stack rated at 1.2 MW, a minimum operational limit of 30 % is considered based on the hourly available energy.
Fig. 3. Comparison of MPPT principles.( a) A conventional stack with DC / DC converter: the operating point is set at the intersection of the PV and stack power curves, with the converter adjusting voltage to reach the maximum power point.( b) Modular system: multiple smaller modules offer many possible operating points. The system activates modules to stay near the PV maximum power, tracking it without dedicated MPPT hardware. Grey curves show increments from 2 to 120 module pairs.
18 Hydrogen Tech World | Issue 22 | June 2025