Dense Fluid Pumped Hydro Does not Make Any Sense & A Mea Culpa

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A current on-line dialogue on gravity storage introduced the same old suspects out of the woodwork. Proponents of heavy fluid pumped hydro reared their sludgy heads this time. Comply with alongside for why this can be a foolish concept, as all gravity storage choices that aren’t pushing water uphill develop into.

As a reminder, gravity storage could be very fundamental stuff. The mathematics is Grade 5. The science is Grade 7. Mass instances the acceleration on account of gravity instances peak. Kilograms instances 9.8 meters per second squared instances peak in meters. Joules are the unit of vitality this produces, and 1,000,000 of them is about 0.28 kWh. Sure, Joules are tiny. A ton of mass at 100 meters of peak has about that a lot potential vitality, so in the event you had been to droop it with a crane with an electrical regenerating winch, you’ll get about that a lot electrical energy out of it. This is the reason the mere considered suspending blocks of concrete or metal in mid-air with a crane would by no means happen to any rational, STEM-competent individual, until they had been venally promoting it to STEM-illiterate lovers with open wallets.

What’s heavy fluid pumped hydro? Effectively, let’s begin with pumped hydro, then let’s go on to the ‘drawback’ that heavy fluid pumped hydro ‘solves.’ We’ve been pumping water uphill to retailer electrical energy since 1907. All it takes is a hill, a reservoir on the high, a reservoir on the backside, a tunnel or some actually robust pipes, and a few reversible hydroelectric generators. Pump numerous grime low-cost water as much as a very easy higher reservoir by means of a tunnel by means of rock with actually easy electrical generators. Whenever you want electrical energy, let the water circulation again down by means of the tunnel and generators to generate electrical energy.

Hills have been round for the reason that Earth coalesced out of a ball of house mud. The primary reservoir was in all probability constructed round 2500 BCE in Egypt. We’ve been constructing tunnels since about 520 BCE, when a Greek tyrant named Polycrates constructed a kilometer-long tunnel to deliver contemporary water for the town’s 20- or 30-thousand residents. The primary hydroelectric turbine was in all probability in-built 1882 in Wisconsin, USA, of all locations. This isn’t remotely difficult know-how.

But some individuals suppose it actually wants enhancing on. A type of teams are the heavy fluids people. Their issues are some mixture of an absence of vertical distance, an absence of water, or an absence of locations to place pumped hydro. Let’s begin with the final one.

See all of these dots? A number of years in the past, the Australian Nationwide College and a bunch of individuals led by researcher Matt Shares did a geographical info system research. That they had a pc search for all of the locations on Earth for which there was respectable information the place it was doable to place a few reservoirs inside a small handful of kilometers. They ignored locations with lower than 400 meters of vertical distance between reservoirs (keep in mind that peak factor within the fundamental science). They eradicated wherever there was operating water, to keep away from messing up streams or rivers. They prevented locations that had been protected areas, principally parks and the like. They picked locations that had been pretty near current transmission traces, so it will be straightforward to deliver electrical energy to and from the reservoirs.

They discovered a slightly absurd variety of websites that met these standards. Lots of the massive clean spots on the map above are simply locations the place an extremely small variety of individuals stay, and there’s no transmission and even good information units. They discovered 100 instances the useful resource potential for pumped hydro as the entire quantity of vitality storage that their research concluded was required for all decarbonization. If solely 0.5% of the websites, one in 200, pan out, that’s 50% of the issue solved.

There aren’t a scarcity of web sites to place closed loop, off-river, pumped hydro electrical energy storage. That’s two of the objections knocked off the checklist, locations to place it the place there’s ample peak. Oh, wait, say the pumped hydro critics. What concerning the Nice Plains of the USA, the Prairies of Canada, and the Northern European Plain? These are a subset of the clean spots to the north of the map. Apparently these individuals have by no means heard that we will transmit electrical energy, or that there’s this factor referred to as the grid that we will have storage belongings on.

This leaves the third standards, having sufficient water. Let’s think about a fairly large pumped hydro facility, one with 30 GWh of storage, about 7,700 Tesla Megapacks, the massive grid storage one. Its peak distinction is 500 meters. Its round-trip effectivity is about 80%. It will require round 28 million cubic meters of water. That appears like so much.

How a lot contemporary water does the USA devour each day? About 1,200 million cubic meters. Do pumped hydro services devour the water? No, it simply goes up and down, with a little bit of evaporation requiring topping off. Pumped hydro services don’t require a brand new 28 million cubic meters of water every single day, they only play with the water they’ve. 30 GWh of storage requires about one-fortieth of a single day’s water consumption, and doesn’t devour it. That’s about one sixteen-hundredth of the USA’s annual water consumption. When pumped hydro services are constructed, generally the builders simply allow them to refill with rainwater, though that’s pretty gradual. Many are actually replenished with rain sufficiently to require that extra water be fed into close by streams or rivers. Others run pipes or construct non permanent channels from close by rivers or lakes.

If you would like extra vitality storage, simply make the highest and backside reservoirs larger. Larger reservoirs are remarkably straightforward to construct. They’re the least troublesome and least costly a part of pumped hydro. Due to the character of reservoirs as three-dimensional volumes, increasing them 10 meters in all instructions produces non-linear outcomes. Let’s take a easy instance. Suppose you’ve got a dice 40 meters on a facet. It has a quantity of 64,000 cubic meters. Let’s broaden it 10% in all instructions, turning it right into a dice 44 meters on a facet.

Does the quantity and therefore the mass of water it might maintain enhance by 10% to 70,400 cubic meters? No, it expands to 85,184 cubic meters, a full 33%. Double the perimeters of the dice to 80 meters and the quantity isn’t doubled to 128,000 cubic meters however shoots as much as 512,000 cubic meters, a full 8 instances as a lot water and therefore mass. Word that increasing quantity a couple of meters in every route ends in an exponential acquire, not a linear acquire.

It’s a bit troublesome, in different phrases, to determine what drawback the heavy fluid people suppose that they’re fixing. Are they making it cheaper? Are they making it extra handy to seek out fluids? Are they rising the variety of websites with 400 meters of head peak or extra? Effectively, no.

What are they claiming? That through the use of heavier fluids, they’ll cut back peak or quantity of fluids, usually by 60%. Keep in mind, it’s mass instances acceleration on account of gravity instances peak. There aren’t any exponents in there, not like with the quantity of reservoirs cubing or wind vitality swept space squaring or wind velocity energy cubing. The rise of vitality for pumped hydro by making the fluid heavier is linear. Double the mass of the fluid and also you get double the potential vitality storage.

If the heavy fluid people had been enjoying with one thing the place there was an exponent, like swept space of wind generators or velocity of the wind, they might be on to one thing. However they aren’t. They’re enjoying with linear stuff, the mass of fluids.

How are they doing that? One proposed methodology entails utilizing brine options, that are mixtures of water and excessive concentrations of salts like sodium chloride or calcium chloride and are 10% to 40% heavier for a similar quantity. Magnetorheological fluids, iron filings in water or oil, are 2.5 to 4 instances denser. Fluorinated artificial oils (40% to 90% denser) and glycerin mixtures (15% to 25%) have additionally been thought-about on account of their increased densities and secure properties. However nobody is attempting to commercialize any of the above, so far as I’m conscious.

There’s one agency on the market which is attempting to commercialize a distinct answer, fine-milled solids in a suspension in water. What does that imply? A suspension is a bunch of strong particles floating in a liquid. Depart them alone and so they’ll sink to the underside or float to the highest finally. How dense the ensuing heavy fluid is decided by the combination density system, which is fairly fundamental. These aren’t options, that are like a full jar of marbles that you simply add water to with out rising the quantity of the jar. The strong particles displace water.

They’re asserting that their fluid has 2.5 instances extra mass per cubic meter as water. In consequence, they’ll use 40% of the water or 40% of the peak and get the identical vitality storage. Provided that neither water or peak are remotely restricted sources or significantly exhausting to take advantage of, this can be a little bit of head-scratcher, however perhaps it’s cheaper?

Larger, heavier particles sink to the underside sooner. Larger, lighter particles rise to the floor sooner. Therefore, fine-milled solids, on the size of micrometers or nanometers. There are 1,000,000 micrometers and 1,000,000,000 nanometers in a meter. They’re tiny particles. You may be considering to your self, how can we make particles of stuff that small, and the way a lot does it value? Good query.

Ball milling is a broadly used methodology, the place supplies are floor in a rotating cylindrical chamber with metal or ceramic balls, attaining particle sizes within the micrometer vary by means of repeated impression and friction. Jet milling employs high-velocity jets of compressed air or fuel to speed up particles and trigger them to collide, successfully producing sub-micrometer particles. Cryogenic milling cools supplies to cryogenic temperatures utilizing liquid nitrogen earlier than milling, making them extra brittle and simpler to grind — excellent for heat-sensitive supplies. Attrition milling entails grinding materials by friction and shear forces in a mill with rotating discs or arms, producing tremendous and uniform particles for numerous industrial functions.

Is any of this low-cost? Probably not. Let’s begin with the uncooked supplies. The agency in query is coy about what fine-milled strong they’re utilizing of their patented fluid, however they’ve stated in public statements that it’s a standard substance utilized in oral medicines, principally a innocent substance that will increase quantity sufficient that sufferers can swallow or swish the lively elements. The commonest of those is microcrystalline cellulose produced from wooden pulp, however its density is far decrease than water.

My first thought was that the key sauce may be silicon dioxide, also referred to as colloidal silicon, generally used as a bulking agent in tablets. The colloidal half is essential for this. Colloidal suspensions are totally different than non-colloidal ones in a couple of methods, however the important one is that the particles don’t settle out, being tremendous sufficient to remain within the combination by means of Brownian movement. Milk is a colloidal suspension of fats globules, casein micelles, and dissolved lactose and minerals, as a standard instance. If a substance isn’t colloidal, all of the heavy bits fall out of the liquid and create a layer of mud on the underside of no matter they’re in.

The utmost for suspended silicon dioxide is about 60%, which coincidentally offers solely a 60% enhance in weight. Silicon dioxide is the densest substance I used to be capable of finding that’s additionally utilized in oral medicines, so there’s a sniff take a look at drawback. Its density by itself is 2.65 instances that of water, however you may solely combine 0.6 grams of silicon dioxide with 0.4 grams of water, and whenever you add the densities collectively it doesn’t come near 2.5 instances the mass of water.

This implies that they aren’t utilizing silicon dioxide, or if they’re, they’re getting the tip mass flawed. Not getting the fundamentals of physics proper is comparatively widespread for individuals who attempt to outdo fundamental pumped hydro, however let’s assume that they’re competent.

What else would possibly they be utilizing? Probably barite, aka barium sulfate, which is 4.5 instances denser than water. It’s broadly used within the oil and fuel business as a weighting agent in drilling fluids. It’s additionally broadly used as a radiopaque distinction agent for X-ray imaging and different diagnostic procedures. That people are given it to drink means that that is what the agency meant, and so they or the individuals reporting don’t know that it’s not a drugs, however used for diagnostic imaging.

Keep in mind that bit about colloidal suspensions? Barite doesn’t tick that field by itself. Usually bentonite is added, a clay which will increase the viscosity of water in order that the bentonite particles stay colloidally suspended. That is generally utilized in drilling. We’ll come again to that viscosity later.

A little bit of serviette math suggests a combination of 5% bentonite and 41% barite in water would have a density about 2.5 instances that of water, and it will be a colloidal suspension. It’s fully doable to realize the two.5 instances mass for a similar quantity that the corporate claims, in different phrases.

What would this value? What does water pumped from a lake or river value? Allow and utilization prices may be a greenback per cubic meter. Pumping it a kilometer prices 10 to 50 cents. Assuming the water supply is ten kilometers away, that turns into per $2 to $6 per cubic meter. A cubic meter of water weighs a ton.

Advantageous milled barite usually prices $100 to $300 per ton in bulk per what I used to be capable of finding on-line (not being an individual who operates drilling gear). Bentonite prices about $100 per ton as properly. Choosing the averages, that means that 5% bentonite and 41% barite would value about $87 per ton of elements, with 54% water added to make it 100%.

Plain water prices maybe $4 per ton. The colloidal suspension prices about $90 per ton. That’s 22.5 instances dearer for two.5 instances as a lot vitality storage.

What would this do to the capital prices for a reasonably-sized pumped hydro answer, that’s, one which was price constructing? Let’s take the 30 GWh answer above. The massive declare of the agency in query is about peak, so let’s take the five hundred meters within the instance and divide it by 2.5, giving us a pleasant even 200 meters. The identical quantity of water is required, 28 million cubic meters.

The essential pumped hydro facility would value $3 to $9 billion to construct, a mean of $6 billion. Filling it will value one other $112 million, a fraction of the development value.

Constructing a 200-meter peak facility with the identical measurement tunnels and reservoirs saves a little bit of development prices, however not that a lot. Name it $2 to $7 billion for a mean of $4.5 billion. That’s a saving of $1.5 billion maybe. Filling it with 28 million cubic meters of $90 per cubic meter fluid, nevertheless would value $2.5 billion. A lot for that saving. Add a billion to the capital prices.

Really a bit extra. The bentonite and barite aren’t going to get to the positioning totally free. Let’s assume that they need to journey 500 kilometers, 400 of it by rail and 100 by truck. Freight trucking within the USA prices about $0.25 per ton kilometer. Rail prices round $0.04 per ton kilometer. Add one other $700 million to the price. It’s now $1.7 billion extra, about 33% dearer, for a similar vitality storage.

Is that this a showstopper? Not essentially, though it’s a head-scratcher as to why anybody would pay a full third extra for a similar vitality storage.

Is there anything? Sure, viscous fluids will impression turbine effectivity. A barite suspension with bentonite mud or a surfactant like polysorbate which might additionally allow a colloidal suspension has a centipoise (cP) — the measure of viscosity — within the 50 to 200 vary, usually round 100 cP. That’s a bit extra viscous than olive oil and a bit lower than maple syrup, however they’re options, not suspensions. The full system impression in a single route is 6% to fifteen% — my makes an attempt at calculations ended up with that vary — however that’s 12% to 30% roundtrip losses total. Pumped hydro tends to function round 80% roundtrip effectivity, so this technique is more likely to be round 70% or decrease.

Anything? Sure, turbine blade abrasion. Colloidal suspensions of solids nonetheless have particles of solids. Hydroelectric turbine blades have excessive tip velocities and so they degrade with an excessive amount of sand and grit. That is like having fixed very tremendous grit, so generators gained’t final as lengthy.

Another factor. Colloidal suspensions are usually not as secure as options. The solids do are likely to drift out of them finally on account of aggregation and some different issues. Suspension components like bentonite mud and polysorbate degrade over time on account of quite a lot of fairly regular issues together with temperature adjustments, mild, oxygen, and microbes. Whereas turbulence in a heavy fluid pumped hydro system would have a tendency to scale back sedimentation and the corporate intends to surround the tanks of fluids to scale back mild impacts, until they make it a sealed system with top quality management and inert gases as a substitute of air — all of which provides extra value — the suspension will break down over time, requiring flushing and changing of all the water and components at nice expense.

A lot increased value of fluid. Decrease effectivity. Decrease lifespan. It’s an actual headscratcher.

To be clear, my evaluation of barite is predicated on the agency’s statements concerning the substance usually, however they haven’t acknowledged that it’s barite, however a ‘high-tech’ powder additive to water. Different options which were recommended are lighter, poisonous or not, issues which could be added as a powder. It’s doable that they’ve one thing which types a secure answer, however it doesn’t align with the articles the place it’s asserted to be one thing utilized in medical situations the place people swallow it.

However that stated, the agency in query will not be aiming to essentially scale up gravity storage, it’s aiming for 10 MW to 50 MW programs and attempting to compete with cell-based batteries that are plummeting in value and have 85% to 95% spherical journey efficiencies. Like different makes an attempt to make small-scale gravity storage make the least sense, it falls over of its personal weight with out delivering a lot worth.

Mea culpa: In a earlier model of this text I used to be utterly rotated on the viscosity calculations. The effectivity impacts are usually not almost as excessive as that article acknowledged. The earlier model of the article asserted that the dense fluid pumped hydro wouldn’t work, however that’s not true. It should work, it should simply be costly and never significantly long-lived. A part of my enjoyment comes from exploring new points of science and engineering, and generally meaning I get the flawed finish of the stick utterly. This was a kind of instances.