this post was submitted on 02 Oct 2024
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To be honest, at grid scale, I don't see why the answer to this today isn't that the government/energy companies just build a shit load of gravity batteries and use the basically free power times to build grid supply for when the sun's gone down.
Paying billions for mega projects to save millions on cheap electricity makes no sense.
Napkin math gravity battery Last figures I found are from 2022 the costs storing 1GW 24 hours is $150 per installed kWh
My apartment has an estimated electricity consumption annually of 2000kWh, I'll need to store half that for $150 per kWh in a structure that lasts 100 years without maintenance, then crumbles into dust and needs to be rebuilt. It would average out to $1500 per year.
My current electricity bill is about $600 per year.
2000kwh a YEAR? Do you live in 70° weather year around and have all gas utilities or what?
No. It's district heating and not included on the electricity bill. I live north of the Arctic circle and a house from the same year with a heat pump would use an order of magnitude more.
The example was meant to highlight the absurd costs despite ludicrously favorable assumptions.
Interesting. For reference, I use more than that most months, but I live in Texas and it is very very hot.
I think your calculations are way off based on what I've just checked.
Firstly the average UK house (which is on average a fair bit smaller than American houses, for example), which typically doesn't use AC and electric heating/cooking uses 2,700kWh (and around 10,000kWh of gas). I imagine that most other countries that don't typically use gas and have AC, have a significantly higher average.
Secondly I'm seeing several sources saying <$0.20/kWh is what pumped hydro battery storage costs, which is roughly 2/3 of the price of grid electricity in my country.
Finally, we spend billions on power plants—why not power storage too? It's necessary infrastructure spending whichever way you go about it.
I don't live in the US either.
I think the actual value on my bill is 2300kwh. But we can use 2700.
I can't find any source for $0.2/kWh. I used https://www.energy.gov/eere/analysis/2022-grid-energy-storage-technology-cost-and-performance-assessment and eyeballed the cheapest gravitational storage. PSH is still above $50. Well let's assume $0.2 per kWh per year and that half of it can be stored it's $270 per year in storage fee
My actual price for electricity is much lower than €600 per year, most of it is taxes and fees that does not get benefit from storage. Looking up the invoice from March i paid $0.07 per kWh, September was $0.01. Half of 2700 would be $95 using March price for the entire year.
We are spending billions, we must spend billions, but we have to spend them where it makes sense. Spending 270 to save 95 is insanity.
Wow your electricity prices are insanely cheap to me! I knew it was a bit more expensive here, but not by over 3x or even 30x based on your September estimate! We also have standing charges that amount to something like £250 a year even if you use no electricity whatsoever. My electricity & gas bill is over double yours for two people in a 2 bed house and we basically never use the heating. I think the economy of it makes sense with my situation but it definitely doesn't for you
If you don't mind me asking, where is it you live? Does your country have a lot of oil reserves or something?
North Scandinavia.
Most of the electricity here is hydroelectric that has been built many years ago so the power plants are paid off.
The price during summer is very low. In the winter especially the cold months is much higher with Dec-Feb being the peak.
The determining factor is still the capex for storing it. At $50 it makes no sense. At $0.2 it makes sense in some places. I don't know which assumption is correct, I expect to be wrong in 50% of the cases when I argue on the internet.
Your electricity usage isn't equally distributed. You use more power during the day - primarily for cooling your house - than you do at night.
We also get a glut of wind power in the mornings and evenings, during big swings in temperature. Plenty of opportunity to harness cheap energy at the moment it is available.
And even after that, battery prices have been falling for years. Current EV batteries are $133/kWh with expectations of $100/kWh by next year and under $80/kWh by 2030.
That's before we get into the benefits of High Voltage DC transmissions, which can move large volumes of electricity across regions with minimal loss. Peak production on one coast can offset higher than expected usage on another.
And just like that you've shown that gravity batteries aren't feasible.
Storage is going to be a big part of the solution going forward. But it's going to be chemical batteries and thermal batteries, not gravity batteries.
Give it a few years and I've got my hopes up for batteries.
The calculations showed the absurdity in gravity storage today, not batteries in the future.
Gravity just isn't a good store of energy relative to chemical and nuclear alternatives.
It's a simple method for storing energy but not an efficient method. That's why the human body uses ATP instead of a bunch of pebbles that get lifted to our heads and dropped to our perineum.
But hey, we'll always have Dams. And tidal generators are gaining momentum. They're basically gravity batteries.
Because "gravity batteries" is a stupid inefficient concept peddled by techbros to solve a huge problem with "a magic solution". In reality, they require either digging straight down like a mine shaft, but at huge scale, or a high rise building with all the weight concentrated on its top floor when the batteries are "charged". Wind would sway that shit left and right, the weight concentration would undermine / damage the building if it even was possible to build at scale.
Well, you can use dams.
The problem is really down to finding places where you can actually build something like a hydroelectric power plant.
You need a large area you can safely flood. (No villages in the area or only villages you can buy out the owners of) or a high up lake.
The area to flood needs to have the geology required to construct a dam safely.
And finally, the area needs to be pretty high up and have an area below you can direct the outgoing water to.
Yeah, but there are already built hydroeletric dams that can be reused like that.
so-called "gravity batteries" is pretty much exactly a dam with a mini-dam/reservoir at the bottom. When there is an excess, you run the motor to reverse the waterflow to pump uphill into a highe-elevation water retention pond/mini-dam.
This also helps reduce the amount of outflow water "lost" due to high-demand. Since you could take almost a day to fill the bottom reservoir and spend "wind"/solar to pump back the "lost" water downstream back into the higher-level reservoir.
Even if things are inefficient wind/solar are "renewable", so you can keep "wasting" excess to replenish the dam and still make enough money back ( think in-terms of drought, flooding, windy, sunny, cloudy, etc ) you can basically keep the high-output "system" always topped-up with water. And still supply water + electricity as it is needed. There is no "downside".
Not everyone agrees. So opinions can differ.
With the situation in Ukraine, we really should spend on home scale storage for the resiliency against any disaster, even though it’s not as cost efficient