French energy giant Engie has developed a transfer function method based on a model used to assess PV plant variability. Its researchers claim that the new approach does not overestimate the levelized cost of hydrogen of an alkaline electrolyzer powered by offgrid solar.

Researchers at Engie Laborelec, a unit of French energy giant Engie, have developed a new way to determine the levelized cost of hydrogen (LCOH) generated by alkaline electrolyzers powered by offgrid, utility-scale solar power plants.

“The study is exclusively based on off-grid electrolyzers as this is a use-case that we have experienced,” researcher Jonathan Lehmann told pv magazine. “In a grid-constrained environment, due to the cheap cost of PV electricity, powering up a 50 MW electrolyzer with a 100 MW off-grid PV plant coupled to a battery might be cheaper than investing in a grid connection upgrade to purchasing electricity from the grid.”

The current LCOH produced from fossil fuels ranges between $1.34 and $2.4 per kg, depending on the technology and location. Solar-powered hydrogen may already compete with blue hydrogen in certain locations, according to the researchers – particularly in Australia, where an LCOH of $2.36 per kg is already considered achievable.

The researchers studied the LCOH impact of the data used to simulate the PV production. When designing a photovoltaic plant coupled to an electrolyzer, the consideration of irradiance or hourly typical meteorological year (TMY) measurements does not accurately represent the dynamic behavior of the plant. This can cause an underestimation of the power produced by the solar plant and, as a consequence, an overestimation of the LCOH.

Their analysis was conducted on a seven-month set of historical data from a 36 MW photovoltaic plant located in Brazil's Rio Grande do Norte state. The LCOH was calculated using power production simulated by two different methods, both based on irradiance measurement.

One of the two methods is the system adviser model (SAM) developed by the U.S. Department of Energy's National Renewable Energy Laboratory (NREL). This modeling software combines time-series weather data and system specifications to assess the electricity production of a renewable energy system.

The second method, described as a transfer function method, was developed by the Engie research group on a model conceived by researchers at the Universidad Pública de Navarra in Spain to assess PV plant variability. It purportedly can precisely simulate the output power of a PV facility from incident irradiance measurement by considering the plant itself as a low-pass filter in the frequency domain.