Gravity Storage 101, Or Why Pumped Hydro Is The Solely Remotely Actual Gravity Storage

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In my current article celebrating the nice month that pumped hydro had, between the Loch Ness Pink John facility promoting to Statkraft, the UK lastly selecting cap and ground for the know-how and China having 365 GW of energy and 4 to eight TWh of power storage underneath building, I included a throwaway line.

As a reminder, pumped hydro is the gravity storage answer that truly works, in contrast to concrete blocks, elevators and hillside rail techniques.

This triggered all the individuals who suppose that lifting small lots small distances is a remotely smart power storage know-how, those who suppose unused workplace elevators, water towers, and mines and massive piles of sand are a large supply of untapped storage as effectively.

So it’s time, as soon as once more, for the fundamentals and a bunch of examples so that individuals can cease fantasizing about elevators, water towers, or trains, and concentrate on water and current hills as an alternative.

Let’s begin with the fundamentals of the physics. Gravity storage works due to potential power. That’s merely a mass increased up. Because it goes down, the potential power turns into kinetic power, the power of motion. Because it goes down, we are able to harvest that power. It takes power to maneuver the mass upward, and might get various levels of power again from it on its means down.

That is all topic to the legal guidelines of thermodynamics. Let’s use British writer and scientist C.P. Snow’s model:

• You’ll be able to’t win (that’s, you can not get one thing for nothing, as a result of matter and power are conserved).
• You’ll be able to’t break even (you can not return to the identical power state, as a result of there may be at all times a rise in dysfunction; entropy at all times will increase).
• You’ll be able to’t get out of the sport (as a result of absolute zero is unattainable).

What which means is that in the event you put 100 MWh into an power storage system of any type, you’ll get lower than 100 MWh again. That’s often necessary, however not with power storage techniques that aren’t pumped hydro utilizing current hills. There’s no means across the three legal guidelines, there’s no reinterpretation of them that allows them to be sidestepped (as one remark I noticed not too long ago mentioned for his or her know-how) and everybody has to play by the identical guidelines.

Okay, so it’s power and we’re going to get much less out than in. How will we work out how a lot power? That’s straightforward. Multiplying the mass occasions the acceleration as a result of power of gravity occasions the peak will get the potential power, the utmost quantity you will get again. That’s in joules, which isn’t useful for the common one that by no means makes use of joules, however 1,000,000 joules is 0.277778 kWh. The opposite means round, a kWh has 3.6 million joules.

Multiplication like that is taught in Grade 5. The physics of potential power attributable to gravity is taught in Grade 7. If at any level this can be a bit powerful for you, ask a 13-year-old to assist out.

As a result of that is metric, we use meters and kilograms, and gravity is measured in meters per second squared, 9.8 of them to be considerably exact. Let’s begin with a hypothetical scenario, a one metric ton or 1000-kilogram block we transfer up 100 meters. Good spherical, easy numbers.

1,000 kg * 9.8 m/s^2 * 100 m = 980,000 joules. That looks as if a giant quantity, however that’s solely about 1,000,000 joules which suggests it’s equal to about 0.277778 kWh.

A Tesla wants about 14.4 kWh to journey 100 kilometers, so this one-ton block transferring down 100 meters is sufficient to drive a Tesla slightly below two kilometers. One other means to consider it’s that it is sufficient to boil a pot of water.

For these unfamiliar with metric, that’s near the size of an American soccer area, however straight up and a couple of,200 kilos. To boil a pot of water. Electrical vehicles are actually environment friendly.

Okay now that now we have the fundamentals, let’s take a few examples. Let’s begin with the varied rail-based gravity storage options. I’m pretty acquainted with heavy freight rail and know that they need to play by the principles similar to everybody else.

Metal wheels on metal rails signifies that heavy trains require lower than 2% grades, in any other case they’ll’t go up hills. Which means you want a really lengthy set of rails to get very a lot top. The size of the prepare signifies that it will possibly’t get all of it up or down the hill, so you’re working with a portion of the slope.

Let’s load the rail vehicles as much as the utmost 130 metric tons for heavy freight rail every. Let’s use comparatively customary 18-meter vehicles. Let’s use 50 vehicles for a good size and mass prepare. That makes it 900 meters, nearly a kilometer lengthy.

At 2% grade, you’d want 10 kilometers of monitor to get 200 meters of head top. However the prepare’s size truly means you’d be solely getting about 9 kilometers of rise of the middle of gravity, so it’s truly 180 meters.

50 vehicles * 130 metric tons is 6,500 metric tons whole mass.

Mass * gravity * top = 6,500,000 kg * 9.8 m/s^2 * 180 meters = 11,466,000,000 joules. That’s about 3.2 MWh.

The present Tesla Megapack is customary delivery container measurement in top and width, 29 toes lengthy and eight.5 toes excessive, and shops 3.9 MWh. You’ll be able to put them within the nook of parking heaps.

Yeah, an nearly kilometer-long prepare with ten kilometers of monitor has lots much less power storage than a delivery container filled with Tesla’s batteries.

There are funicular railroads that go up steeper pitches, however they’ve vastly much less mass as a result of the pressure on the cables will get so excessive that they snap. Shorter distances up steeper slopes contain comparable heights however vastly much less mass, so power storage drops by one or two orders of magnitude.

That is bleedingly apparent to anybody who has spent any time doing mass and power calculations or remembers something they realized earlier than highschool, which is why individuals like me assume that companies selling mechanical gravity power storage that isn’t pumped hydro will fail and disappear and not using a hint, forgetting the gullibility of enterprise capitalists, the venality of SPAC pump and dumpers and the credulity of retail buyers. Fools and their cash are quickly parted. Hopefully it will inoculate just a few individuals.

What about water tower power storage? By now, you understand what the questions are. How tall is the middle of gravity of the mass? How a lot mass is there? Be at liberty to make use of that extremely tough scientific instrument, Google, that can assist you reply these questions.

Nah, I’ll simply do it. They vary from 40 to 50 meters. Should you’ve learn this far, your spidey sense shall be tingling already. That’s simply not that a lot. What about mass? On common, about 3,800 metric tons of water. Effectively, your spidey tense should be ringing alarm bells proper now. However nonetheless, let’s do the mathematics. Let’s give it a break and assume a 50-meter water tower.

However that mass isn’t all 50 meters off the bottom. Water has a thousand kilograms per cubic meter, which is an instance of why the rational components of the world use metric. Which means 3,800 cubic meters in a ball. How massive on a facet is that with the shell? About 16 or 17 meters in diameter. My guess earlier than calculating was 15 meters, which is 0.6 meters off the diameter if the ball of water was simply floating in house. Not a foul guesstimate, and par for the course for anybody who spends any cheap period of time with this sort of factor. My being shut isn’t a function or one thing particular in different phrases, it’s simply an occupational hazard.

Okay, so the middle of gravity of the water is barely 37.5 meters off of the bottom. Massive purple lights and sirens must be going off now.

3,800,000 kilograms * 9.8 m/s^2 * 37.5 = round 390 kWh. That’s possibly half a Tesla Semi battery pack and a tenth of a Tesla Megapack.

However wait, there’s extra. Why do water towers exist? To supply water stress to communities in order that water truly comes out of faucets and hearth hydrants when wanted in ample volumes. What’s water stress? Power. Oh, wait. If we take all the power out of the water because it comes out of the water tower, which means there’s no power left for water stress. Dribbling showers and firehoses aren’t any enjoyable in any respect.

What haven’t we ripped to shreds with Grade 7 physics but? Oh, yeah, mines and sand. I actually want individuals weren’t severe about this, however they’re.

There are a few concepts, however the looniest one is sinking sand into an empty mine in massive buckets with regenerating winches, dumping the sand out on the backside, and having massive automobiles push the sand down facet tunnels. To ‘retailer’ power, the automobiles working underground would scoop up the sand and dump it again into the buckets which might be raised to the floor.

Cease and take into consideration that for a minute. Utilizing lots of power underground to push sand round when the purpose is to retailer power. Why is that being finished? Effectively, sand isn’t a liquid, it’s only a bit liquidy a few of the time. Sand flows, however not like water. Pour water right into a mine and it’ll fill each nook and crevice as a result of it’s molecules of dihydrogen monoxide.

Water molecules are 0.275 nanometers. Sand grains common a millimeter. Nanometer, millimeter, what’s six orders of magnitude amongst pals? Water molecules are about 4 million occasions smaller than sand, and so they aren’t all lumpy, coarse, and spiky. They slip previous each other higher than the best high-thread rely Egyptian cotton or silk sheets it’s attainable so that you can think about.

So that is clearly a deeply silly concept, and but I’ve seen individuals who severely suggest it. The inefficiency is off the charts, and simply think about even autonomous electrical front-end loaders driving continuously by a mud cloud of smaller sand particles, which will get of their gears.

The choice concept is to place lots of sand on a single elevator with enormous winches that simply goes up and down in a giant, deep mine shaft. This one at the very least has the potential to be viable. Let’s faux we are able to discover a kilometer-deep mine shaft that’s deserted and hasn’t full of water as much as 30 meters under floor degree. Oh, wait, we are able to’t discover one thing like that as a result of floor water? Ignore actuality for a minute.

Mine shafts have a diameter of 5 to twenty meters. Let’s faux now we have an enormous 20-meter mine shaft that’s a kilometer deep and never filled with water. Okay, how massive a load of sand can we placed on an elevator in a 20-meter diameter shaft? Let’s assume we are able to put it in a giant bin 10 meters tall. In order that’s 20 meters in diameter and 10 meters tall of sand. That’s lots. For Individuals, that’s 66 toes throughout and 33 toes tall.

The amount of a cylinder that measurement is 3,142 cubic meters. By the best way, calculating that’s taught in eighth Grade. We’ve superior all the best way to 13-year-old youngsters in fundamental faculties in our math and physics.

Sand has a density of about 1,600 kilograms per cubic meter. That’s about 5,000 tons of sand. Hmmm. Do now we have winches that may elevate 5,000 tons? Errr. No. That’s nearly precisely ten occasions larger than huge winches for deepwater building. Okay, let’s pare that again. Possibly 1,000 tons of sand? Reduce the depth to 2 meters as an alternative? Positive. Let’s try this math, as soon as once more, for this fictional, enormous, water-free, deep mine shaft, one among which could exist on this planet.

1,000,000 kilograms * 9.8 m/s^2 * 1000 meters = about 1,360 kWh. That’s 1.4 MWh.

That isn’t very spectacular. A kilometer-deep shaft with a large elevator filled with two meters of sand labored by a few the largest winches ever constructed and it’s solely as a lot as a 3rd of a Tesla Megapack that’s 29 toes lengthy and eight.5 toes tall.

By the best way, sand is grime low cost and the physics of winches signifies that it actually doesn’t matter in the event you make the load denser, for instance by utilizing lead. Doubling the load nonetheless solely will get to 2.7 MWh, which is an terrible lot of engineering and building for a return effectively under one thing you’ll be able to order and have dropped within the nook of a car parking zone.

Are we finished but? Not an opportunity. There are a bunch of people that suppose that workplace constructing elevators are an untapped useful resource of power storage.

They suppose that at night time, massive dollies of heavy stuff will be shoved into freight elevators within the basement, lifted as much as the seventy fifth ground, and rolled into government workplaces and board rooms, then within the morning, dropped down once more to generate electrical energy.

I actually want individuals weren’t saying this severely. I actually, actually do.

Okay, let’s make consider for a bit. How a lot weight can workplace constructing freight elevators elevate? Massive ones can handle 9 tons. What’s that sound? The sirens of spidey sense whooping. What’s that noise? The multicolored lights of spidey sense flashing. 9 tons? We’ve been speaking about hundreds of tons. 9 of them? Actually?

Okay, however 75 tales. That’s lots, proper? That’s like, actually excessive? Positive. Possibly 225 meters. Okay, Grade 7 math time once more.

9,000 kilograms * 9.8 m/s^2 * 225 meters = about 5.5 kWh.

Some sweaty lackey goes to load 9 tons of paper or sand or stale birthday cake onto a large dolly, grunt it right into a freight elevator, then grunt it right into a boardroom, then reverse this course of the subsequent day, and that is an power storage answer? The primary Tesla Powerwall held 7 kWh, if reminiscence serves, and was mild sufficient to mount on a wall out of the best way, the place it simply sat and presumably blinked with little LED standing lights.

Let’s simply throw a giant bucket of ice water onto this already absurd nonsense. Have you ever heard of counterweights? Elevators have these huge weights that go up when elevators go down and vice versa to counteract all the load of the elevator, cable, friction, and the workplace employees. The purpose of that’s effectivity in transferring weight up and down. All of these elevators don’t have even 5.5 kWh to spare as a result of they’ve been designed to keep away from needing it.

The individuals who suppose this concept is nice have zero data of power, Grade 7 math, or absolutely the fundamentals of elevators. Maybe they had been homeschooled within the prairies by Luddites or one thing. Decide your motive why this utterly absurd concept was truly gaining traction.

So let’s speak closed loop, off-river, pumped hydro storage. Because the article headline says, it’s the one actual gravity storage choice. Why? Effectively, as a result of it has billions of kilograms of mass tons of of meters of distance between prime and backside. Geography creates the peak without spending a dime, simply requiring a 10-meter diameter tunnel be dug by it, which admittedly is dear and has long-tailed dangers associated to building. And water’s tiny molecules don’t want any assist to prepare themselves. None of these sweaty confused workplace employees. None of these huge front-end loaders pushing sand down tunnels. Simply pumps.

The mass and top are each massive numbers. The mass particularly is a very massive quantity. And water is grime low cost. This isn’t filtered, bottled, purified, chlorinated water. It’s simply lake or river water. The water isn’t consumed. It goes up. It goes again down. It goes up once more. Advert nauseum. If water may get bored, it will. A few of it evaporates yearly, so the system must be topped up. Nothing-burger.

Okay, let’s do some math. Let’s go to the Australia Nationwide College greenfield GIS research of potential paired reservoirs that aren’t on current water pathways, which might be near transmission, that aren’t on protected land, and which have over 400 meters of distance between prime and backside reservoir. It discovered 100 occasions the potential capability for power storage as your complete world requirement for power storage in the long run sport.

Just one% of the websites need to work out with a view to present all of the power storage for a totally electrified world powered by renewables. And some blockers have already been eradicated. Near transmission and never on protected land, keep in mind? Somebody complained to me not too long ago that precisely one among 616,000 websites recognized had 14,000 individuals that will be displaced. So go to the subsequent web site already.

Math, although. Let’s choose a 500-meter head top web site. Let’s choose a billion liters of water, a gigaliter weighing a billion kilograms, 1,000,000 tons. Wait, what’s not taking place? Your spidey sense isn’t flashing lights and blaring alarms. These are massive numbers on each side.

1,000,000,000 kilograms * 9.8 m/s^2 * 500 = 1.4 GWh of grid storage.

Oh. GWh. Important grid storage. Okay, now we’re speaking!

Effectively, these should be massive reservoirs for a gigaliter at 500 meters, proper? No. A sq. kilometer up prime, a sq. kilometer on the backside. Ponds.

Let’s take the three Clever Land Funding websites in Scotland, together with the Loch Ness Pink John web site that was not too long ago bought to Norway’s Statkraft. They’re designed to make use of lochs as their decrease reservoir and turkey’s nest reservoirs on overlooking hills as higher reservoirs. Plenty of water. Plenty of top. Free water as a result of it’s simply sitting there within the lochs, ready to be pumped uphill in a really low environmental impression means.

2.5 GW of energy capability. 60 GWh of power capability.

Tesla Megapacks can ship about 2 MW of energy. That is like 1,250 of them. They’ll retailer about 3.9 MWh of power. That is like 15,000 of them.

Pumped hydro is the one actual gravity storage answer as a result of it makes use of a mud low cost, excessive density, simply pumped liquid that finds its degree routinely and makes use of current geographical function to create massive top variations. Each different gravity storage answer is children taking part in round in a sand field.

I’ll repeat this. Grade 7 math is all that’s required to determine this out. Entitled Hollywood belief fund children Chad and Buffy, who get gold stars for attending class, are anticipated to have the ability to do that actually fundamental math in checks to cross and get to Grade 8, maybe with examples of caviar on facet tables falling on the ground. Anybody who thinks that something aside from pumped hydro is remotely smart is a number of of some issues. They’re silly. They by no means made it by Grade 7. They’re deeply lazy. They’re credulous. They’re gullible.

Don’t be that individual. That is concerning the lowest bar in power that’s attainable to search out. Should you can’t determine this out, you aren’t remotely competent to have discussions about any of the truly fascinating stuff in power, like Ohm’s Legislation or substituting aluminum for copper in HVDC cables or why baseload power is an archaic time period left over from tiny grids enshrined in regulation gone its sell-by date.