this post was submitted on 28 Sep 2023
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I just heard about gravity "batteries" that involve lifting concrete blocks to store potential energy, then dropping them to generate electricity with a turbine. It's probably the most interesting thing I've heard of in a while and such a clever way to store energy without needing a battery.
The math doesn't really work out for gravity batteries. A fifteen ton block dropping 100 feet releases about a kwh of energy.
Or you could just have $150 worth of lithium batteries.
How much energy is released is not as important as the ratio of how much it takes to lift vs. lower (AKA "efficiency")
This. Thanks for doing the math. The only way it makes any real sense is if you a have geographical features that can store the energy. Ie right near a mountain and a large body of water high up. And even with that, it often only makes economical sense at exsisting dams where you can pump the water back into the reservoir and the generation systems is already paid for and in place.
See I've been skeptical about the gravity battery, too. I'm glad to see it developed, toyed with, but I like very simple ideas with very few, if any, moving parts. Gravity battery? Moving parts, cables. Would be a nightmare to work on if it broke down, possibly dangerous with the stored potential energy.
Much safer: sand battery. BTUs are expensive, you're probably heating your water, and depending on the winter climate where you live, you are using electricity to convert to BTUs so you can heat your home/not die. I say skip the middle man!! Convert the extra energy generated from solar/wind/whatever....store it in the fucking sand as heat.
I also look at the sand battery's simplicity, serviceability from a post-nuke/EMP/grid-down/post-apocalyptic standpoint. Should I be unfortunate enough to survive. It's so...practical. Solar panels should only get hit <15% damage from EMP. It gets the electricity. Sent to large copper rods, acting as heating elements. Heat the sand. 🙌🏻 Sand will cost a few thousand & never degrade. Rods, cheap enough, have some spares. Those shitty LiPO batteries play out during the apocalypse, as they literally always do? You're SOL.
first, it stores heat only. you can make it work with 1000L or so barrel of water and this gets you supply for days. second, you'd want this thing to service entire small community, because otherwise square-cube law fucks you hard. you need also all the auxiliary devices like heaters, pumps, control hardware that looks the same no matter if you make it work for your house or small village
That is correct, it stores heat only. A little bit about my situation: I have a drafty AF, 3200 sq ft farmhouse. Yes, I know I need to fix that....all things cost a lot of money, to do well.
A hot water tank tie-in would be excellent too, of course.
Additionally, I'd put the heated sand to work heating a large concrete driveway, a sidewalk in the winter months. While this can be classed as a "luxury", I view it as an investment in my health & well-being, as well as reducing risk & increasing my reliability. Eventually I'd like to throw up a polebarn style garage, with heated concrete pad, pull on the sand battery to heat that as well. Winter is a big problem where I live!! And a massive pain in my ass.
Please be kind, I've heard talk like this before, but tbh I don't know what it means: > "because otherwise square-cube law fucks you hard."
What does this mean? 🤔 ELI5? TIA, I like these convos. 👍🏻👍🏻👍🏻
please invest in good winter shoes and shovel. first, you need massive amount of heat to warm up all that concrete and then melt ice, but it's not enough. you also have to get rid of liquid water entirely because otherwise it'll just freeze again but now it's glossy and flat surface of ice
when making sand battery, what you're actually interested in is mass of sand. however you can't conjure perfectly spherical globe of dirt suspended in vacuum, you have to put it somewhere. you need a tank, and one with hefty insulation. now: mass is proportional to volume, which is proportional to r^3 - cube. price of tank and amount of insulation needed is proportional to its surface - r^2 - square. the bigger you make it, the more sand you get per square meter of tank surface, meaning that storage costs go down with scale. that example from finland serves entire community for example
square-cube law provides some hard limitations on what is practical and what is not, for example it explains why big animals move slower than smaller ones. https://en.wikipedia.org/wiki/Square%E2%80%93cube_law
I have plenty of boots & shovels. 😂 Again, it's not a matter of "luxury"...I am concerned about both personal health & the snow being gone in a timely fashion after a snowfall.
Men who shovel snow are at an increased risk for heart attacks. And that's just heart trouble; let's not forget general sprains, strains, & aches. Possible slip-and-falls, I can't imagine having a bad fall when I'm in my 70s, 80s+.We often see a few significant snow events per year, and to have a surefire way to automatically melt it would be great.
To be fully transparent about my situation...I have a big-ass tractor, too. I can clear the snow without physical exertion. But it's over at another property, and after a fresh snowfall, I sometimes have to "schedule" time with the tractor jockeying against my parents & my sister, BIL. Annoying.
...but that's not all, with the tractor method. Extremely, dangerously cold situations can even become too cold for tractors to operate. The diesel will gel unless more questionable additives, methods are used. Operating a tractor is not free, either, and puts more hours on an expensive piece of machinery. There have also been maybe 4 times where I'm clearing the snow, and some kid is on the road in his $2K car, and gets way too close to my $90K tractor when we're all slogging in terrible, soggy/cold/poor visibility conditions. I'm always polite, of course, but then they leave & I audibly bellow to myself I don't fucking need this. I don't!! Why should I haggle with family, operate this good equipment, around the general public if I could avoid that entirely with a heated concrete driveway?
So the only real concern with the square-cube law is physical space occupied, and/or cost. Space isn't an issue on the farm. 🤠 And sand by the ton is cheap. I was personally thinking about digging a big-ass hole to hold the sand. Line it with junk bricks and/or more concrete, only put money into an insulated "cap".
The water left on the driveway is an interesting thought, but the driveway won't be perfectly flat. It'll have a downward slant, towards the road. If you think it's enough of an issue, I could maybe put some designs in the concrete that route snow melt run-off off the concrete & into some grass on either side. I know people that heat driveways & they're fine/dry; it can be done, I'll ask around. I know it's marketed as a luxury, but I want heated driveways normalized.
I DO need a lot of heat for this heated driveway, I know it's ambitious, but I have plenty of reasons for wanting it. Outlined above. Heart attacks/hospital visits? Expensive, waste of time. Tractors, "sharing" operation costs, risk of accidents...expensive. Waste of time. I'm going to pay any way you look at it. Why not pay for a recirculating heat pump, its operation & watch my problems literally melt away??
you need a lot of insulation on all sides. putting it all above ground would be easier because of no risk of groundwater ingress. structural steel container, fire-resistant brick and lots and lots of mineral wool around (we're talking about insulating red-hot (600C) sand so that it stays hot for months). we're talking about several tons of dirt suspended above ground and insulated on all sides, including bottom. you could put that heat to better use if it stays contained within another insulated container, that is as a hot water source or for space heating. these things are not free, and this comes before any heaters, pumps, piping, automation needed for it to work
if you want to go for a solution, then all good, but for it to be practical you also need to make sure it's better than alternatives. i think that getting another tractor would be cheaper and more practical in your situation
Yes. And it works.
It's called a Dam.
The catch is we spend 0 energy on the upstream water.
Timberborn has those, it's a city builder game with beavers.
there are plenty issues with wear of all moving parts involved. fortunately it can be improved on in a pretty straightforward way https://www.youtube.com/watch?v=iGGOjD_OtAM
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Energy storage is THE issue…. You want to be a billionaire? Figure that out.
Pumped hydro, is great, but there are very few places where it is feasible
there are many nifty ways to do it. i like molten silicon for example https://silbat.com
but how about shift in perspective? if you want to get in on all renewable power source, maybe it's you who should adjust power consumption a little bit instead? fortunately most of energy used is used up for heating, and you can plug all excess energy into heater, store energy in big barrel of water for all your heating needs, and skim electrical power when available + maybe batteries as a higher priority
What makes you think they haven't already?
in some places energy for individual customer is cheaper at night, but the real deal is with large industrial power consumers, like arc furnaces or aluminum smelting plants. these things have special arrangements that allow grid operator to regulate some % of power in return for cheaper energy, either by remote control or on schedule. in principle the same thing could work for thousands to millions of water heaters, making it work like a large, one way "battery" soaking up peaks in energy production