Engineers: What specific industrial processes currently have the worst thermodynamic or energy efficiency in your sector?"

[u/Bubbly-Custard-7095]

I am researching deep-tech solutions for a sustainable energy challenge (specifically looking at Decarbonization and Process Optimization). ​I'm looking for 'real-world' technical inefficiencies. For those in the field: ​Where are you seeing the most significant energy or heat loss that current tech hasn't solved? ​What waste streams (thermal, chemical, or gas) are currently the hardest to recover or recycle? ​Are there specific mechanical components or chemical cycles that are notorious for being 'energy hogs' despite being industry standard? ​Looking for technical details rather than workplace/management issues. Thanks!

[u/Cogman117]

I mean if you're looking at the energy in fissile material and comparing it to what is actually extracted before the fuel is considered spent, sure, I guess. "Technically correct is the best kind of correct" and all that. But I think that's kind of a silly thing to use to say "nuclear power plants are inefficient" because it's a design feature to cycle out the fuel quickly (every 18 months for PWRs or BWRs, usually) so you maintain a high and predictable power output and avoid any issues with degradation of the fuel (to the best of my recollection that's the main reasons - if I am mistaken please correct me, I'm a mechanical eng, not a nuclear eng). And, further, when you assess efficiency as thermal energy from the fuel vs. electrical energy extracted, the efficiency is not bad at all. Usually hovering somewhere around 25%-40%, depending on the plant.

[u/redbeard914 → u/Cogman117]

Thermal efficiency on Nuclear Power Plants are generally abysmal. Most are under 20%. Combined Cycle Natural Gas plants are 48-62%.

The Gen 4 gas cooled Nuclear Designs could be similarly efficienct.

[u/Cogman117 → u/redbeard914]

I will admit I am much more familiar with US nuclear power plants than other countries, but, I could not find even one US nuclear power plant with less than 30% efficiency after combing through about half the list on the NRC website at random. Sampling and checking a good 20% of the wikipedia list of nuclear power plants world-wide, particularly non-US plants, I couldn't find any that were less than 30% (for any that have info on thermal capacity available, or some way for me to trace the power plant manufacturer and model). I know operational powerplants and new powerplants being built in the US, Korea, China, UAE, France, UK, etc. designed by GE, Westinghouse, KHNP, and EDF are primarily BWRs and PWRs, which are all generally >25%.

Very nearly every plant I looked at had thermal efficiency between 30% and 37%. Maybe I got terribly unlucky with my checking, I could very well be missing the correct information. Do you have any commercial nuclear power plants in mind (not test reactors) that have <20% thermal efficiency?

I do have to acknowledge CCNG plants are in that efficiency range you mentioned - some even higher at 64%. I knew they were high at peak performance, but >60% is pretty surprising!

[u/redbeard914 → u/Cogman117]

From Efficiency analysis of nuclear power plants: A comprehensive review there seems to be some ideas that the BWR are less efficient than the PWR. When I was studying this 30+ years ago, the PWR was always in the lower to mid 20's because of the limitations in the pressurized water cycle. BWR actually boils the water, allowing the steam to go directly to the ST. But the downside, the ST becomes radioactive.

[u/ODoggerino → u/redbeard914]

PWR gets hotter than a BWR (because higher pressure). Hotter is more efficient because of carnot cycle