On the electrolysis demo, how do I configure a larger cell?

I started the elysim demo (Cloud-based simulation of electrolysis systems for H₂ production) on https://saas.simevo.com/, I created a new case with the default configuration, and as soon as it runs in the Outputs tab I get for powerIn (Total electric power consumption) 11 kW, which is more or less consistent with the publication Sánchez et al. 2020.

Now I would like to try a larger cell so I doubled both Stack cell length and Stack cell width:

but surprisingly I get a lower powerIn = 7.24 kW. What I am doing wrong?

Hi @tizz and welcome to our community! I managed to get closer to 40 kW total electric power consumption using this case configuration:

As you can see I have doubled stack cell length and width as you did, but I also multiplied by 4 the estimates for H2- and O2-side electrolyte recycles (from 0.124 kg/s i.e. 447 kg/h to ~1810 kg/h).

The results is now what you were expecting:

The reason I had to quadruple those estimates is due to the way the STACK is specified:

we set the fractional conversion of water per pass through the electrolyzer to 0.54 %! This low water conversion per pass is required to have a large excess of circulating electrolyte solution for cooling the stack.

The way you had specified it, you had a larger cell area with the same electrolyte recycles and water conversion per pass; this resulted in lower areic current, lower resistance and lower losses. The total electric power consumption was 25% lower with the same H2 production!

The model developer can choose to make it easier for you to manipulate the power rating by adding to the model a mechanism that sets the recycles for you, but this has not been done in this very bare-bone demo!