If you can do a lot of work with expensive machines to get 20MW from that plant, but you can also do less work and spend less money getting an extra 20MW by burning some cheap primary fuel (with higher quality heat/aka a bigger delta), then they’re just going to burn more primary fuel. It’s a bit silly to do it any other way (barring legislation or market pressures or whatever) if you care about the amount of energy you are getting for the money you are paying.
And that is a fundamental issue, as reclaiming energy from secondary heat is always going to be less ‘nice’ than from the primary fuel.
If you can do it easily enough that it doesn’t add a lot of extra cost, then chances are the primary turbine/power system could be built efficiently enough to not throw that waste heat out the back in the first place. They do so because the math doesn’t check out generally.
> primary turbine/power system could be built efficiently enough to not throw that waste heat out the back in the first place
It sounds like this might be a situation where maybe an older turbine already exists for generating mechanical power (pumping), and the add-on kit is supposed to capture more energy without having to replace the existing systems?
If the input is expensive, then the economics change and it’s more worthwhile to pay more in equipment to get more out of the input.
I bet someone has a really detailed set of calculations that would tell you exactly when that line is crossed. But I doubt they are hanging out here.
The problem isn't the technology, it is the economics.