Re-reading the title and the first paragraph of the OP, the initial premise of this thread started out being that this novel concept would raise the efficiency of existing Rankine cycle plants by the stated percentages-or that is the way I understood it.
I think it has been well established by valued contributors to this thread that to modify an existing large steam turbine power plant's steam cycle by the addition of a T-turbine would require serious modifications to the main turbine's steam flow path, probably more extensive (and expensive) than physically (and financially) possible with a 20-30 year old machine short of complete rotor/diaphragm (spindle/dummy ring) change out which, while expensive and a major undertaking, are not totally unheard of. I think GE has some GER's on their site to this effect.
However, that effort, with the other required cycle modifications, such as to the power piping to the FWH's now served by extractions from the T-turbine rather than the main turbine's IP and LP sections as well as the FWH's themselves as they now have to be designed ground up with new steam and water conditions and flows make this project more daunting by the minute.
While I have warmed somewhat to the overall concept, my fuzzies will have to strictly be limited to projects that start with a clean sheet of paper as we used to say.
I do like what it does to the second point heater which in the normal (single RH at least) cycle is furnished steam by relatively high temperature superheated steam from the first extraction point of the IP turbine and which in my experience is a trouble spot in the FWH string. The DSH sections of that heater and occasionally the third point heater take a beating at those temperatures. The high temperatures place limitations on certain tube metallurgy's too.
Again, while taking at face value the thermodynamics of the steam flows through the T-turbine I do have to wonder why the t-turbine doesn't exhaust it's remaining steam to a LP heater in the main turbine's condenser neck rather than a separate condenser called a regenerative heater; but who am I to say?
Seriously, however, I do have to wonder what type of generator that it will take that will turn via the SSS clutch at the same speed as the turbine and BFP. Will that be a half or 3/4 pole machine since it is stated that the T-turbine and pump need to turn ~5K rpm for optimum stage efficiency purposes. So, oops, now we need a gear box somewhere in the T-turbine train; more expense, not to mention the cost and complexity of the additional generator itself.
I will also have to concede that by loading the T-generator when the main turbine is at partial loads, steam flows can be maintained through the T-turbine insuring that the FW temperature stays as high as possible, only limited by the temperature of the cold RH rather than the decay of temperatures throughout the entire main turbine steam path.
So, I still have to wonder what we have accomplished. Even with a clean sheet of paper design, the additional components required make me wonder if the capital expense will ever be recouped. While I can be convinced if I see the real numbers that prove it out, however, let's just say that the first of these plants will have to be located at Missouri P&L for me to believe it.
BUT, and that is a capital BUT, I still say that this has been an excellent peer to peer discussion of an interesting emerging technology. Thank you DAVEFITZ for bringing this to our attention. I'll be interested to see where this concept goes-if it goes, that is.
Weigh in if you have any more thoughts or comments to my thoughts.
rmw