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Must admit I thought this would never get off the ground - but they're building a pilot plant for this pumped hydro system which uses some sort of high-density fluid instead of water to get more energy in and out of the system for less fluid volume than if it was "just" water.

https://renews.biz/92824/new-hydro-syst ... eployment/

Same here Dan, I thought this was one of those 'interesting, but won't go anywhere' ideas. Assuming the dense fluid is cost effective, then it sounds like a great idea for closed systems.

How much does mercury cost at ~13.5x the density of water?

Mercury's a bit toxic though isn't it when it leaks!

Water is a nasty thing though - it'll work its way through any seal, it'll damage any bearing, wear out any pipe, turbine blade and impellor given enough time. Making it more dense with some dissolved chemical must surely just make all those problems worse?

Guess it's worth finding out.

dan_b wrote: ↑Mon Apr 29, 2024 1:51 pm Mercury's a bit toxic though isn't it when it leaks!

Water is a nasty thing though - it'll work its way through any seal, it'll damage any bearing, wear out any pipe, turbine blade and impellor given enough time. Making it more dense with some dissolved chemical must surely just make all those problems worse?

Guess it's worth finding out.

Last time I looked it was some proprietary mixture of kaolin clay or similar to increase the density of the water. I guess you just make the impellor wear surfaces hard enough to not be subject to excessive wear.

Oh that makes sense then. This system is being installed in, guess what, a kaolin clay mine.

Reminds me of those bottles of kaolin and morphine as a kid, that you had to shake well, overwise it was just morphine ....... ah, that explains why you don't see it any more.

Crikey yes I remember being given that as a kid when I had dodgy stomach once - goodness me - over the counter liquid morphine given to children - madness!

If they are using clay it will be as a carrier for another weighting agent. In the world of drilling fluids this would be barite which would be capable of being mixed at somewhere between 2 and 2.5sg. (Hematite is occasionally used to get slightly higher densities).

dan_b wrote: ↑Mon Apr 29, 2024 1:51 pm
Water is a nasty thing though - it'll work its way through any seal, it'll damage any bearing, wear out any pipe, turbine blade and impellor given enough time. Making it more dense with some dissolved chemical must surely just make all those problems worse?

We* find that a viscous fluid is much less likely to leak than water and pumping heavy fluids full of (very fine) solids is everyday stuff (eg a drilling mud pump would be expected to pump 1500 LPM at up to 400 bar pressure for many hundreds of hours without failure. This project won't be working at anything like those pressures (and temperatures) so I don't imagine the pumping will be a problem.

*I'm a drilling fluids engineer.

Thanks, great to learn new stuff each day.

Back to costs, is it fair to assume that the fluid mix will be cheap, so the 2.5x mass makes sense?

Not a trick question, not asking for a yes/no on viability, just interested to know if the basic idea has wings?

Yes, using very fine solids suspended in a carrier fluid is fairly cheap way to get a dense fluid.

It is possible to get true (solids free) fluids up to about 2.3sg (eg Cesium formate brine) but it is eye wateringly expensive (even for the oil industry).