In the meetings we usually hold, it’s very common for the question to arise, “What PV-to-hydrogen ratio do you use?” Well, the answer isn’t simple or uniform. Some people are working with ratios of 60%, and others with ratios of 20%.
We like to work with 25%, meaning four times more installed PV power than hydrogen. It’s important to mention that we’re talking about grid-connected plants. Off-grid plants require a more detailed analysis because hydrogen becomes your only source of revenue (whereas in grid-connected systems, you can profit from what you don’t use for hydrogen production). Analyzing photovoltaic plants, we see that, at least in Andalusia, with that ratio, you can reach the technical minimum (if the electrolyzer is 1 MW, the technical minimum depends on the manufacturer but is around 10%—about 100 kW) only a few times (on average, three times a year). Depending on the electrolyzer technology you use and the design of the installation, this could be more or less problematic.
Now, let’s translate these ratios into quick numbers. Imagine a 4 MWp PV plant, which implies 1 MW (nominal, in hydrogen we don’t use “peak”) of installed electrolysis power (25%, remember?). A plant sized to this ratio has more equivalent hours than with peak power, in the province of Cádiz, for example, about 3,000/3,200 equivalent hours, we’ll settle at 3,100 hours.
Then, a 1 MW electrolyzer produces 18 kg/h at that power, so annually it produces 55,800 kg, averaging 152 kg/day. Of course, it will produce more kilograms in summer than in winter. Additionally, 1 kg of hydrogen requires roughly 15 liters of “raw” water (this depends greatly on the quality of the available “raw” water), which translates to 2.3 m³ of water per day.
We hope you found this helpful. If you have any questions about how to execute your hydrogen project, visit our website www.leanhydrogen.com and get in touch with us. We can be your hydrogen department instantly.
