@sd:

?? They are talking about combined electrical plus thermal efficiency, ie the heat they can use, not detailing the losses, which no doubt go to all sorts of things like heating the equipment, surrounding air and to on.

@SJC

Here are Topsoe Haldor's test results for their SOEC:

https://www.topsoe.com/blog/breakthrough-in-green-hydrogen-topsoes-soec-demo-reveals-strong-results

' The tests have shown a high on-time factor with very few interruptions. The demo test in Frederikssund has demonstrated that with over 2250 hours of operation, Topsoe’s SOEC only had 150 hours of downtime, most of which was planned and none of which was due to the SOEC unit.

The test has also demonstrated high efficiency of around 93% at core level, making Topsoe’s SOEC solution 25%-30% more efficient than alkaline and PEM electrolysis alternatives. This efficiency is bolstered by a system that has shown itself to be robust to transients such as several start-ups, shutdowns and load changes. This efficiency is also based on an optimized electricity consumption of less than 36 kWh/kg H2 at the core, with a hydrogen LHV of 33.3 kWh/kg H2. '

They do add though:

' Topsoe recognizes that the road to net-zero by 2050 will not be paved by any one single idea or technology. Like most complex problems that need to be addressed at a global scale, the energy transition can only be enabled through an ecosystem of complementary solutions that prioritize equitable, sustainable, and scalable energy systems. Topsoe is committed to making SOEC one of these solutions. With the remarkable results demonstrated by the demo team at Frederikssund, it is evident that after decades of development, SOEC technology is on its way to becoming a transformative technology in the energy landscape.'

It's not weird it's thermodynamics the electrolysis is endothermic it takes heat in to do the process you put enough heat in it can go above unity because it's an external heat source

Information about steam turbine operation temperatures from the hypertext book (https://hypertextbook.com/facts/2003/AlanFurmanov.shtml):

"A steam turbine consists of stationary and rotating blades on an axle. High pressure steam enters the turbine. The steam can be anywhere from 200C to 400C."

200C is 392F. At this temperature and higher the heat could be used to run a steam bottoming cycle, and one can argue that the quoted electrical SOEC electrical efficiency should take account of this fact.

Here's good explanation of thermodynamics in SOECs
https://www.sciencedirect.com/science/article/pii/S2214157X21004032

And more to the point, critiques of using hydrogen as part of the energy chain made by so many so repeatedly for so many years on the grounds of supposedly hopeless inefficiency are incorrect, as very good real world efficiency can be obtained.

In addition, it is perfectly practical to pipe hydrogen about, including through repurposed natural gas pipes.

What hydrogen can provide is the ability to store energy, essential if we are to move from a high proportion of renewables to 100%,

This includes for long periods of time for inter seasonal use, which batteries can't manage, especially important in northerly areas like Europe.

This is also rather more attractive financially, as the cunning plan by battery and electric only one-eyed enthusiasts was simply to scrap the vast investment in the gas network.

Even if there are some repurposing costs, it is a lot cheaper to repurpose rather than scrap it.

@sd

A lot depends on what the application is.
My references are old now, and dead, but home fuel cells in japan have been routinely hitting 90% plus electrical plus thermal efficiency for a decade or so.

But you need hot water in a home, and it does not have to be extremely hot unlike in some industrial applications, where however they can reduce how much you have to boost the temperature by and hence energy consumption.

For cars, they have done a good job of using surplus heat for chilly mornings, giving high total electrical plus thermal efficiency, but it ain't always cold, so the heat is simply chucked, so the same tech can give variable total efficiency!

The upper limit of pure electrical efficiency for a fuel cell is not yet in sight, and present values of maybe 60% or so may go up to perhaps 80%..

But presently most of the time a fuel cell might run at maybe 45% or so electrical efficiency, as just like a diesel engine most of the time they are not absolutely in the sweet spot, although batteries integrate better in a fuel cell solution to get nearer optimum more of the time

Just as Topsoe Haldor says, there is no one ultimate solution, just pragmatic optimisation for particular applications.