> inefficiencies inherent in the compressors and turbines This is not why such thermal engines/plants perform (well below) 100% efficiency. You could have isen

> inefficiencies inherent in the compressors and turbines This is not why such thermal engines/plants perform (well below) 100% efficiency. You could have isentropic (i.e., ideal, working losslessly) components and will probably still land below 50% thermal efficiency, limited simply by the Carnot efficiency. That is to say, it's a fundamental physical limit, not an anthropological limit (e.g. component quality). I also don't understand the point you're making. If you burn these three fuels, they have certain carbon footprints. What's wrong with that comparison? You cannot "compare hydrogen to internal combustion engines" --- that's apples and oranges, comparing a fuel to an energy conversion machine. You can compare hydrogen and fuel cells to gasoline/Diesel and ICEs, which gets closer to the whole chain (but still ignores how the fuels were procured). Lastly, ICEs are not "wildly inefficient". Large-scale maritime Diesel engines are some of the most efficient machines we have in this sector. It's not about what's lacking to 100% --- 100% is physically unobtainable. It's about the delta to Carnot efficiency, which gets very small for these. It's important to regard energy qualities and types, since you are comparing apples and oranges otherwise. With energy, there's no free lunch, and a number like 90% efficiency might be entirely meaningless, e.g. for electric water kettles (doesn't stop advertisers).