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

Join every day information updates from CleanTechnica on e-mail. Or comply with us on Google Information!

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 thought, as all gravity storage choices that aren’t pushing water uphill turn into.

As a reminder, gravity storage may be very fundamental stuff. The mathematics is Grade 5. The science is Grade 7. Mass occasions the acceleration attributable to gravity occasions top. Kilograms occasions 9.8 meters per second squared occasions top in meters. Joules are the unit of power 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 top has about that a lot potential power, so if you happen to have been to droop it with a crane with an electrical regenerating winch, you’d get about that a lot electrical energy out of it. Because of this 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 have been venally promoting it to STEM-illiterate lovers with open wallets.

What’s heavy fluid pumped hydro? Properly, 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 sturdy pipes, and a few reversible hydroelectric generators. Pump plenty of grime low-cost water as much as a very easy higher reservoir via a tunnel via rock with actually easy electrical generators. Once you want electrical energy, let the water circulation again down via the tunnel and generators to generate electrical energy.

Hills have been round for the reason that Earth coalesced out of a ball of area mud. The primary reservoir was most likely 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 carry recent water for town’s 20- or 30-thousand residents. The primary hydroelectric turbine was most likely in-built 1882 in Wisconsin, USA, of all locations. This isn’t remotely difficult know-how.

But some folks assume it actually wants enhancing on. A type of teams are the heavy fluids of us. Their considerations are some mixture of a scarcity of vertical distance, a scarcity of water, or a scarcity of locations to place pumped hydro. Let’s begin with the final one.

See all of these dots? A couple of years in the past, the Australian Nationwide College and a bunch of individuals led by researcher Matt Shares did a geographical info system examine. They’d a pc search for all of the locations on Earth for which there was first rate knowledge the place it was attainable 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 top factor within the fundamental science). They eradicated anyplace there was working water, to keep away from messing up streams or rivers. They averted locations that have been protected areas, largely parks and the like. They picked locations that have been pretty near current transmission traces, so it will be straightforward to carry electrical energy to and from the reservoirs.

They discovered a reasonably 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 folks reside, and there’s no transmission and even good knowledge units. They discovered 100 occasions the useful resource potential for pumped hydro as the full quantity of power storage that their examine 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 listing, locations to place it the place there may be adequate top. Oh, wait, say the pumped hydro critics. What in regards to 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 folks have by no means heard that we are able to transmit electrical energy, or that there’s this factor referred to as the grid that we are able to have storage property 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 top distinction is 500 meters. Its round-trip effectivity is about 80%. It will require round 28 million cubic meters of water. That seems like lots.

How a lot recent water does the USA devour every 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 daily, they simply 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 replenish with rainwater, though that’s pretty sluggish. Many are definitely replenished with rain sufficiently to require that extra water be fed into close by streams or rivers. Others run pipes or construct short-term channels from close by rivers or lakes.

If you need extra power 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 could have 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 amount and therefore the mass of water it may maintain improve by 10% to 70,400 cubic meters? No, it expands to 85,184 cubic meters, a full 33%. Double the edges of the dice to 80 meters and the amount isn’t doubled to 128,000 cubic meters however shoots as much as 512,000 cubic meters, a full 8 occasions as a lot water and therefore mass. Word that increasing quantity a number of meters in every path ends in an exponential acquire, not a linear acquire.

It’s a bit troublesome, in different phrases, to determine what drawback the heavy fluid of us assume 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 top or extra? Properly, no.

What are they claiming? That through the use of heavier fluids, they will scale back top or quantity of fluids, usually by 60%. Keep in mind, it’s mass occasions acceleration attributable to gravity occasions top. There aren’t any exponents in there, in contrast to with the amount of reservoirs cubing or wind power swept space squaring or wind velocity energy cubing. The rise of power for pumped hydro by making the fluid heavier is linear. Double the mass of the fluid and also you get double the potential power storage.

If the heavy fluid of us have been taking part in with one thing the place there was an exponent, like swept space of wind generators or velocity of the wind, they’d be on to one thing. However they aren’t. They’re taking part in with linear stuff, the mass of fluids.

How are they doing that? One proposed methodology includes 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 occasions denser. Fluorinated artificial oils (40% to 90% denser) and glycerin mixtures (15% to 25%) have additionally been thought-about attributable to their greater densities and secure properties. However nobody is making an attempt to commercialize any of the above, so far as I’m conscious.

There may be one agency on the market which is making an attempt to commercialize a distinct resolution, fine-milled solids in a suspension in water. What does that imply? A suspension is a bunch of stable particles floating in a liquid. Depart them alone they usually’ll sink to the underside or float to the highest ultimately. How dense the ensuing heavy fluid is set by the combination density components, 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 amount of the jar. The stable particles displace water.

They’re asserting that their fluid has 2.5 occasions extra mass per cubic meter as water. Consequently, they will use 40% of the water or 40% of the peak and get the identical power storage. Provided that neither water or top are remotely restricted assets or notably exhausting to use, this can be a little bit of head-scratcher, however perhaps it’s cheaper?

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

Ball milling is a broadly used methodology, the place supplies are floor in a rotating cylindrical chamber with metal or ceramic balls, reaching particle sizes within the micrometer vary via repeated affect 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 — best for heat-sensitive supplies. Attrition milling includes grinding materials by friction and shear forces in a mill with rotating discs or arms, producing fantastic 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 stable they’re utilizing of their patented fluid, however they’ve stated in public statements that it’s a typical substance utilized in oral medicines, mainly a innocent substance that will increase quantity sufficient that sufferers can swallow or swish the energetic substances. The most typical 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 could be silicon dioxide, often known as colloidal silicon, generally used as a bulking agent in tablets. The colloidal half is essential for this. Colloidal suspensions are completely different than non-colloidal ones in a number of methods, however the vital one is that the particles don’t settle out, being fantastic sufficient to remain within the combination via Brownian movement. Milk is a colloidal suspension of fats globules, casein micelles, and dissolved lactose and minerals, as a typical 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% improve 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 occasions that of water, however you may solely combine 0.6 grams of silicon dioxide with 0.4 grams of water, and once you add the densities collectively it doesn’t come near 2.5 occasions the mass of water.

This means that they aren’t utilizing silicon dioxide, or if they’re, they’re getting the top mass unsuitable. 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 occasions 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, they usually or the folks reporting don’t know that it’s not a medicine, however used for diagnostic imaging.

Do not forget 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 occasions that of water, and it will be a colloidal suspension. It’s fully attainable to realize the two.5 occasions mass for a similar quantity that the corporate claims, in different phrases.

What would this price? What does water pumped from a lake or river price? Allow and utilization prices could 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.

Positive 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 tools). Bentonite prices about $100 per ton as properly. Selecting the averages, that implies that 5% bentonite and 41% barite would price about $87 per ton of substances, 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 occasions dearer for two.5 occasions as a lot power storage.

What would this do to the capital prices for a reasonably-sized pumped hydro resolution, that’s, one which was value constructing? Let’s take the 30 GWh resolution above. The large declare of the agency in query is about top, 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 fundamental pumped hydro facility would price $3 to $9 billion to construct, a mean of $6 billion. Filling it will price one other $112 million, a fraction of the development price.

Constructing a 200-meter top facility with the identical dimension tunnels and reservoirs saves a little bit of building 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 price $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 without spending a dime. Let’s assume that they must 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 associated fee. It’s now $1.7 billion extra, about 33% dearer, for a similar power 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 power storage.

Is there the rest? Sure, viscous fluids will affect turbine effectivity. A barite suspension with bentonite mud or a surfactant like polysorbate which may 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 entire system affect in a single path is 6% to fifteen% — my makes an attempt at calculations ended up with that vary — however that’s 12% to 30% roundtrip losses general. Pumped hydro tends to function round 80% roundtrip effectivity, so this technique is more likely to be round 70% or decrease.

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

Yet one more factor. Colloidal suspensions are usually not as secure as options. The solids do are likely to drift out of them ultimately attributable to aggregation and some different issues. Suspension components like bentonite mud and polysorbate degrade over time attributable to a wide range of fairly regular issues together with temperature modifications, mild, oxygen, and microbes. Whereas turbulence in a heavy fluid pumped hydro system would have a tendency to cut back sedimentation and the corporate intends to surround the tanks of fluids to cut back mild impacts, until they make it a sealed system with prime quality management and inert gases as an alternative of air — all of which provides extra price — the suspension will break down over time, requiring flushing and changing of all the water and components at nice expense.

A lot greater price of fluid. Decrease effectivity. Decrease lifespan. It’s an actual headscratcher.

To be clear, my evaluation of barite relies on the agency’s statements in regards to the substance on the whole, however they haven’t acknowledged that it’s barite, however a ‘high-tech’ powder additive to water. Different alternate options which were steered are lighter, poisonous or not, issues which may be added as a powder. It’s attainable that they’ve one thing which kinds a secure resolution, but it surely 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 is just not aiming to essentially scale up gravity storage, it’s aiming for 10 MW to 50 MW techniques and making an attempt to compete with cell-based batteries that are plummeting in price 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 circled 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’s going to work, it’s going to simply be costly and never notably long-lived. A part of my enjoyment comes from exploring new features of science and engineering, and generally which means I get the unsuitable finish of the stick utterly. This was a type of occasions.