Turning water into a high density slurry ?

Not sure how the powder get to the top of the hill as pumping it back up must obey the First Law.

BBC News

The 'secret sauce' helping to store renewable energy in D...

A 100-year-old idea for hydro electricity generation is being refashioned to help the energy crisis.

Edited Thursday at 09:14 PM1 day by studiot

It’s offered as energy storage, so it’s pumped storage with a higher density than water. No 1st law issues.

not sure what advantage us gained by increasing the density of the water to a slurry.
Sure, you can use a lower height for storage, but the pumping load increases proportionately with the increase in density.
I haven't done, or seen, calculations so I'm not sure of any benefits other than convenience of using existing geological formations.

1 hour ago, MigL said:

not sure what advantage us gained by increasing the density of the water to a slurry.

The main advantage IS being able (potentially) to locate high capacity gravity storage in areas of lower relief, perhaps locating them closer to regions of high demand cutting distribution losses.

A secondary benefit maybe the lower liquid head to volume flow ratio may better facilitate the use of mixed flow (Francis vane type) pumps and turbines which may help hydraulic efficiency.

No mention of the high rates of mechanical wear typically associated with slurries though.

The fact and figures offered are few and far between.

However I did notice that they were talking about a slurry of density slightly greater than 2.

The only experience I have of pumping anything like that is for cementitious materials which have a density in the range 1.8 to 2.8.

The problem I worrry about is the flow rate/ fluid velocity.

It is not only mass that is important for generators attached to turbines, fluid velocity is also important.

Will pushing the slurry up to a high enough velocity not add to the unrecoverable energy costs ?

That is how fast will it flow back under gravity against pipe friction ?

6 hours ago, studiot said:

It is not only mass that is important for generators attached to turbines, fluid velocity is also important.

Will pushing the slurry up to a high enough velocity not add to the unrecoverable energy costs ?

For the same unit power output per unit volume of fluid, a denser fluid needs: less elevation difference; shorter pipe runs; lower fluid velocity.

Without knowing the exact nature of the fluid, it's impossible to say whether losses would rise or fall. For some dense fluids (e.g. mercury) I imagine that losses could fall significantly.

There is potential to increase power output per unit volume of fluid, but now losses would rise in rough proportion (also to square of velocity) though this does seem to imply that efficiency doen't take a serious hit.

Key algebra is h = v²/2g = 'velocity head'

Edited 11 hours ago11 hr by sethoflagos

43 minutes ago, sethoflagos said:

For the same unit power output per unit volume of fluid, a denser fluid needs: less elevation difference; shorter pipe runs; lower fluid velocity.

Without knowing the exact nature of the fluid, it's impossible to say whether losses would rise or fall. For some dense fluids (e.g. mercury) I imagine that losses could fall significantly.

There is potential to increase power output per unit volume of fluid, but now losses would rise in rough proportion (also to square of velocity) though this does seem to imply that efficiency doen't take a serious hit.

Key algebra is h = v²/2g = 'velocity head'

This is not what I am exploring.

here is a couple of extracts from the British Hydropower Organisation for slow moving fluids under gravity

8.2.3 Gravity Turbines

The Archimedes Screw has been used as a pump for centuries, but in recent decades has also been

operated in reverse as a turbine. It’s principle of operation is the same as the overshot waterwheel, but the

clever shape of the helix allows the turbine to rotate faster than the equivalent waterwheel and with a high

efficiency of power conversion (over 80%). However they are still relatively slow-running machines,

which require a multi-stage gearbox to drive a standard generator.

A key advantage of the Screw is that it is proven to be a ‘fish-friendly’ turbine, so avoids the need for a

fine screen and automatic screen-cleaner because fish and smaller debris can pass safely through the

turbine.

https://british-hydro.org/wp-content/uploads/2023/09/BHA-Micro-Hydro-Guide-2024-3.pdf

Edited 10 hours ago10 hr by studiot

Michael Barnard at Cleantechnica did a critique of Dense Fluid Pumped Hydro that may or may not have addressed this specific version.

A solution in search of a problem seems to summarise a lot of his article; yes there would be more suitable locations but there isn't actually a shortage of locations or water for pumped hydro, not when a transmission line can readily accommodate storage at a physical distance. And reducing the elevations needed doesn't reduce the quantities of fluid needed (which are still enormous) and the kinds of materials that can be mixed with water to increase the fluid density are not cheap and depending on what is used, bring other problems, including changed viscosity and increased wear and tear. And, inevitably, leaks.

My own view is pumped hydro does have enormous potential for long, deep storage but the levels of planning and forethought and commitment to investment have been lacking, not suitable sites. Getting the approvals can be problematic and time consuming but not really for regulators that rate decarbonising as essential; governments have the power to push through critical projects, if they so choose.

Until (too) recently the confidence that the solar and wind capacity to need pumped hydro would be built was largely absent - but batteries offer a short term, fast fix, with enough convenience and added benefits that investment that might have flowed to pumped hydro is going to batteries irrespective of lower overall costs per MWh. I think batteries have managed to take advantage of being less impeded by siting approvals process - and from being able to help defer transmission upgrades rather than requiring them. Dense Fluid Hydro startups may see that as an advantage applying to them but I don't think so; batteries will always be easier to site.

Australia has a large pumped hydro project in construction, Snowy 2, somewhat remarkable for being committed to ahead of the solar and wind it is intended for; that project has not been going well (which should not be seen as typical) but the time scales as well us up front costs are still an issue for pumped hydro and the additional transmission capacity is a big cost.

I note that Snowy 2 was committed to the same year as South Australia committed to the first 'large' battery installation (to widespread derision); the battery was in operation before the end of that year and in power delivery terms (MW) batteries now exceed what Snowy 2 will add when it does come online - and are catching up fast in total energy capacity term (MWh). LFP has displaced and exceeded NMC and very possible Sodium will displace and exceed LFP; can't rely on assumptions about batteries being unsuitable for long deep storage.