Neat breakdown with data + some code.
they generate about 3,800kWh per year. We also use about 3,800kWh of electricity each year
Obviously, we can’t use all the power produced over summer and we need to buy power in winter. So here’s my question: How big a battery would we need in order to be completely self-sufficient?
O, god, it’s going to be huge. You really can’t do the off-grid thing unless you have enough power production to satiate you over any given 3-day moving window. Trying to store power from summer until winter is going to be too expensive, instead buy more panel.
This isn’t even going into the fact batteries lose charge slowly. So any power generated in summer will be much diminished by winter, even if you have big enough batteries.
Seems to me his panel capacity is to small anyway.
We have 11 kWh panels, and yes in the summer we routinely produce 4 times more than we use, and we have a 7.5 kWh battery But November December and January it’s not even close to enough.In the Winter you can easily have a week with near zero production:
Our Import / export from grid last year:
November 215 / 59 kWh
December 300 15 kWh
January 268 / 34 kWhDespite we have almost 3 times the capacity, and produce more than twice what we use per year, and we have a decent battery and believe it or not, even the shortest day we can produce enough power for a whole 24 hour day if it’s a clear day! But we can also have clouds for 14 days!
But for those months we imported 783 kWh and exported 108 that could have been used with bigger battery. But the net import was still 675 kWh!! For those 3 months, and that’s the minimum size battery we could have managed with, and then we even need 10% extra to compensate for charge/discharge losses.TLDR:
Minimum 740 kWh battery in our case, and that’s without heating, because we use wood pellets.That means it would require at least the equivalent of 10 high end fully electric car batteries. But also a very hefty inverter, which AFAIK ads about 50% the price of the battery.
PS: Already in February we exported more than we imported.
(Author here) As I say in my post, our roof is full. We have 16x 320 Watt panels - 8 on each side of the roof.
OK I didn’t see that, that’s bigger than I expected, we make about 12.5 MWh per year on our 11.2 kWh panels = 1.1 MWh per kWh capacity.
Your system is 5.1 kWh but you only make 3.8 MWh per year = 0.75 MWh per kWh capacity.
Meaning we have 50% higher yield per kWh rated capacity!So our production remains 3.3 times higher than yours, despite we only have twice the capacity.
But our panels are pretty optimally placed towards the south.Considering you are further south compared to us, I’m surprised your yield is so low, despite London is infamous for being cloudy.
Damn, those winter numbers mean full off-grid is quite difficult with pure solar. A propane or diesel generator to occasionally top off the batteries would be required for winter.
It is not remotely close to economically viable to go off grid, and the exports of solar power to the grid pay for the connection anyway.
The reason to have a battery is that it lasts through the night, or even with a smaller system, it can handle dinner time, which is the most expensive time of day to buy electricity.
Now if you live in some remote area without a grid, a generator is a way better option than a huge battery.
Maybe if you live somewhere very sunny, like Spain and especially southern parts of USA you can probably do it with a modest battery that can handle a couple of days.
In the summer we can make enough electricity on by far the most cloudy days, but in the winter, the sun can’t penetrate the clouds nearly as well.
Admittedly London is south of where I live, which is close to the most southern part of Denmark, but on the other hand London is infamous for grey weather with heavy clouds.You could probably get by with a gas generator and only run it 2-3 times/year in many areas. It’s not 100% green, but it could get you off grid for a fraction of the price.
Diesel generatorsare significantly better on fuel consumption than a gas one and diesel takes alot longer to go bad than gasoline.
Diesel generators run fine on heating oil, which is cheaper since no fuel tax and has longer shelf life.
Stabil 360 additive to fuel.
Power the generator with vegetable oil. There are multi fuel generators that are designed to work well with that kind of fuel. You could also use them for heating which is very useful in Northern regions where you usually need heating and electricity during winter.
You also lose some energy to heat while charging and discharging. And depending on load profiles, you might not be able to load all of your excess solar power at once (depends on how many Watts the battery can be charged at) or fulfill your power requirement with battery alone (depends on how many Watts your battery can deliver).
they generate about 3,800kWh per year. We also use about 3,800kWh of electricity each year.
Holy shit. I think we used that much last month, which is higher than average but not that high for August around here.
You leave 5,278 LED light bulbs on 24/7?
…maybe.
I mean it’s probably their kids doing that.
glad I’m not the only one that noticed that.
last time I checked I was using around 4600-5800kwh from May to August. the rest of the year its 3300-4200.
I live in a dual zoned 5200sqft home and my average power bill is around $900.
I’ve had solar sales try to talk me into solar panels but once they see my consumption they stop answering my calls lol. could be because I told them I’ll buy once I can get net zero.
could be because I told them I’ll buy once I can get net zero.
I’m not following your logic. You aren’t willing to accept any savings unless you can completely zero out your power bill? Judging from your consumption I’m assuming a good chunk of that is for cooling your home? If so that means you’re likely in a pretty great place to harvest solar power. You’d reach payback of your investment on your array much faster than most, and be saving money for probably 35 years or more with little to no additional investment.
Making some guesses for how much your electricity rates are, and how much you’re consuming (assuming much from cooling), you might be a full payback in less than 7 years if you took advantage of the tax credit. Then, every month after that you’d be gaining money back.
my house is over 120 years old. it still has knob and tube in half the house. I have even found gas lines for the old sconces, that were “conveniently” used as grounds for said knob and tube in some places. the house is a nightmare, electrically speaking. the only new-ish electrical are the HVAC systems, the 200amp panel, and the basement (where the rack lives).
for me to get proper solar installed, it would cost more than the house cost to buy. For me to find it in any way cost effective, I would need my $900 a month power bill to pay for the $200k loan on top of my mortgage.
That house sounds like a terrible investment.
lol. all houses are terrible investments, too volatile.
As someone who electrically renovated houses without beeing an electrician. If you find an electrician who is willing to work with you: do a full planning of the house. (What lines go where etc) ask them to go over this, and pay them for their time. If all goes well this will cost them an evening or three (depending how many flaws they find in your design). Do the wiring and drilling raw sockets yourself. Buy the top sockets wholesale, then have the electrician make a fixed price for installing sockets and wiring your fuse box , it will be much cheaper.
appreciate the sound advice. I’ve rewired plenty of houses that I’m comfortable with DIMS and know most of the NEC.
the problem is time and effort. I’m getting older and just don’t have the drive I used to have 20 years ago. the biggest problem is the house is still mostly original plaster lathe which is a huge pita for running new electrical across four floors. add to that the other litany of projects I have to do plus daily life/work. it’s a lot.
if I was 10 years younger I’d probably start one room at a time, but I’m old enough now that I look forward to taking my daily naps before bedtime.
I reserved myself to a modest retirement when I bought this house because I knew the risks going in.
Plaster Lathe. My old nemesis. Probably with reed or peat for stabilization, so it explodes everywhere once you touch it… Wish you the best of Luck.
Also: napping is important at our age.
Wtf?? Are you running a crypto farm or something?? $900 is insane
that’s an average btw. last months bill was $1100.
this month is already at $960 and we’re only halfway through the month.
this year has been lower than previous. I had new insulation installed last November.
highest bill I have ever seen was around $2200 which is over my monthly mortgage.
no crypto farm. though it would probably be higher if I was.
I have personally never seen a bill of more than 60€ per month. I have some friends living in bigger houses, not apartments, and they tell they can get over 100 fairly frequently, the bigger ones more in the North can get over 200 in the winters, but even still, I’ve never even heard of anything reaching 300.
But I’m in my thirties and don’t really know anyone from beyond upper middle class. That might help explain my experience if it happens to be the outlier, but just reading the responses to this, I might not be the outlier here.
Anything four figures is just crazy surreal to me. I can not even imagine what it takes to reach that kind of electric usage. Or maybe it’s just extremely expensive, not the usage itself being crazy? I would think living in a place where sustaining one’s existence requires that kind of resource usage would be very hostile against settling and building in general?
But if it’s just personal usage rather than the regional climate or whatever, and an insane price of electricity isn’t the main reason, then I don’t even know what to say. That’s crazy.
it’s kind of a mix of everything.
I grew up poor. like, “take a nap for dinner” poor. I was afforded great opportunities that allowed me to become comfortably wealthy, as in I can freely go to the store and just buy groceries without concern. This is important because I always promised myself that when I grew up I would live comfortably.
I keep my house between 68F-72F year round. I don’t open my windows because I have terrible allergies (that my kids have also inherited). at least half of my bill is just heating and cooling. the other half is likely a mix of the servers and the regular appliances.
I have family ranging from 30-60 years old. when I told them how much I spend on power their eyes popped out. they don’t run their hvacs as much as I do, and actually use their windows and attic fans. they also don’t have the allergic reactions I have either so 🤷.
in my old home, 1600sqft, our highest bill was around $300, and that was still high for the area. our neighbors were average between $100-$150. they were in their 70s though, so likely they didn’t use their hvac as much either, nor the technology I was running.
Fair enough, that’d explain it. I did expect air conditioning to be a big part of it, kind of makes a lot of sense that you do run servers as well.
Still, that’s a huge bill to eat each month.
Thats awful, im so sorry. Our entire house is usually $200ish but it jumped to $400ish because they put in a data center nearby and are using residents to subsidize it
is that per-month, or for the whole span?
per month.
I assume that’s HVAC. Makes more sense to fix that before solar.
I’m a fan of small scale wind, if there’s climate and space for it. 20hrs a day of a (small) 500w adds up really quickly compared to more panels, especially in grey winter weather. The problem is that there’s a bigger difference between megawatt scale solar vs homeowner scale, and megawatt scale wind vs homeowner scale, so there’s limited investment.
Wind isn’t great small scale. You rarely can get high enough for constant wind energy. They are noisy. They don’t produce a lot. In many or even most cases solar will be better than wind.
I’d go so far as building both sun oriented and a solar “fence” line going north/south to get more non-peak solar before putting up small-scale wind.
How big a battery would we need in order to be completely self-sufficient?
Exactly. Haven’t read all details of the link,so I react your comment, and have immersed myself a bit in this earlier.
You need to change your way of thinking and energy usage. Start with your daily energy supply and then change your energy consumption pattern to day time use Then, with for example a dynamic energy contract or if you can spare solar energy, buy or store cheap electricity in your storage ( battery ). The energy management system ( charge / uncharge and which cells) is very important.
Also, realize that battery life is tied to charge cycles and need replacing like every 10 years when talking about the better quality Lithium battery . Sodium systems could and maybe should be used in parallel, if you want more storage, safety and longevity (20 years).
It is yet all quite expensive, though imo having a half day reserve like 5 - 10 kwh, battery, would already create more independence (at around € 3K to € 10 K in Europe) .
Basically why the grid exists to begin with. You’re not supposed to be solving these engineering problems on a household budget inside a single home.
You’d be better off simply reducing your consumption or finding alternative methods of power (nat gas or maybe wind or geothermal) during the longer winter nights.
If you really want to go crazy, you should consider investing in a bigger home with better insulation and roommates. An apartment/condo block can at least leverage economies of scale, if you’re dead set on DIY. More people benefiting from the setup dilutes the cost per person.
Basically why the grid exists to begin with
Agreed this is the best option. Economy of scales and our consumers wishes should dictate the Grids plan to incorporate cheap energy ( and emergency) storages.
And, also like you said, change your energy life style and insulate your house wherever you can.
I’m very ignorant on this subject, but couldn’t you just sell excess to grid and get it back for a minimal markup? Seems like a good governmemt incentive to even supplement an even exchange program. Scaling things to everyone having their own giant batteries seems like a waste of the existing infrastructure.
I’m very ignorant on this subject, but couldn’t you just sell excess to grid and get it back for a minimal markup?
Sure, but it depends on the incentives in your country. Afaik, excess energy could be sold, but you’ll have to checkout your local incentives and energy suppliers for specifics. In most parts of Europe, the are scaling down the prices for excess energy. Therefore, battery systems are being forwarded in some cases as sort of solution for solar panels maintaining like ca. 80% +? integrity efficiency over 20 to 30 years.
For example, I read that in The Netherlands the solar panel market has crashed completely or is crashing. Note here that saturation of the market ( many existing solar panels) can also cause that.
You need to find out;
- energy usage
- insulation options and materials
- costs /benefits
- energy contracts and energy incentives.
- check out current physical electricity wiring and fuses in the house
- DIY or professional?
- budget etc
TLDR: dont buy solarpanels if you want to be rich. And buy them according and after you’ve done everything possible to insulate your house, whether in the colder or warmer climates. The efficiency, added value, and comfort reached by insulation outweighs everything else. Then , after doing that, check your kwh usage, and buy solars according to that.
Hope this is helpful, but seems you need to go outthere and do some exploration on the topic.
(Ed: layout)
And buy them according and after you’ve done everything possible to insulate your house, whether in the colder or warmer climates.
In the USA there are silly rules that you can only get 120% capacity of your last years worth grid consumption as solar installed. So if one were to follow your advice and do all the energy efficient improvement prior to solar, then you would be restricted to getting a much smaller array. I understand why they have the rule, but its easy to circumvent by just having artificially oversized consumption for a year in your house, and you can then get the larger array you want before then doing all the energy improvements post-array installation.
In the USA there are silly rules that you can only get 120% capacity of your last years worth grid consumption as solar installed.
Yes , I can see how that impacts the process. indeed checking the rules and doing some prior info digging is essential.
It’s also important to check whether solar overcacity is worthwhile in the UsA. Her3 it is not( anymore).
It’s also important to check whether solar overcacity is worthwhile in the UsA. Her3 it is not( anymore).
I’ll say generally speaking in most places it isn’t, however, once you go solar, you may increase your electricity usage as you move away from carbon based energy. Before solar we had natural gas furnace heating and two gasoline cars. Now we have two EVs and a cold climate heat pump with zero natural gas and zero gasoline consumption. So I wanted the larger solar capacity to cover the increases in electricity we knew we’d have.
Its worked out pretty well. We have fairly large electricity bills ($400ish) in Jan and Feb, a small bill in March, and usually a tiny bill (under $10) in April. Then no bills for the rest of the year. Also keep in mind that is TOTAL energy costs, no gas or gasoline bought anymore.
nicely done.
(Author here) Yes, this is how it works in the UK. I sell my excess electricity back to the grid. The selling price is a bit smaller than the buying price.
Something very important that anti-nuclear but otherwise environmental minded people should realize is this sentence: " There’s no practical way to build domestic batteries with this capacity using the technology of 2025."
Also applies to grid storage. There does not exist a chemical energy storage solution that can substitute for “baseload” power. It’s purely theoretical much like fusion power. Sure maybe in 50 years, but right now IT DOESN’T EXIST. Economically, practically, or even theoretically.Why do I bring this up? Because I’ve seen too many people think that solar and wind can replace all traditional power plants. But if you are anti-nuclear, you are just advocating for more fossil fuels. Every megawatt of wind or solar, has a megawatt of coal or gas behind it and thus we are increasing our greenhouse gas emission everytime we build “green” generation unless we also build Nuclear power plants. /soapbox
It’s very infuriating talking to people about this because they never really accept that nuclear power is necessary. They spend all their time complaining about how it’s dangerous (it isn’t) and how it’s very expensive, and how you don’t have a lot of control over its output capacity. And yeah, all of those are true, but so what, the only other option is to burn some dead trees which obviously we don’t want to do.
Just because nuclear has downsides doesn’t mean you can ignore it, unless of course you want to invent fusion just to spite me, in which case I’ll be fine with that.
The new tack is to conflate nuclear energy with fossil fuels. As in assuming that nuclear energy is “legacy” power generation, and that obviously we need to use modern gernation like solar and wind, and magical grid-level storage technologies that don’t exist. Also ignore that baseload power is still required, and is currently fulfilled with Natural Gas and Coal.
Well, unfortunately some people are using nuclear as an excuse to argue that we don’t need any renewables at all and that they should be banned entirely. They do this because they know that nuclear faces extreme regulatory and societal challenges and it would allow coal, diesel and gas to continue unabated.
So it creates a backlash where renewable advocates feel they have to fight nuclear to survive.
In US, and EU is having similar nightmare, nuclear was last built at $15/watt. Installing solar is under $1/watt, and for 20 equivalent hours of nuclear per day (less demand at night means not full production even if available) equivalent to $5/watt-day. $1/watt capital costs is 2c/kwh for solar, and for full day production needs 10c/kwh. All before financing. Nuclear is 30c/kwh. It adds 10 extra years of construction financing, requires political bribes to suppress alternative supply whenever they decide to begin operations, uranium purchases/disposal, expensive skilled operations staff, security, disaster insurance.
Solar does need batteries for time shifting its daily supply. At current LFP prices of $100/kwh, 1c/kwh full cycle is prefinancing cost. and so 3c/kwh if triple the charging/discharging daily capacity. 6 hours of storage is a very high number in power systems. It will capture all energy from a northern summer. It will rarely fully discharge with any time shifting incentives to daytime (much higher convenience to consumers and industry) providing resilience to rainy days. A 2c/kwh value (before financing which is apples to apples comparison to nucclear) means a 5gw solar + 30gwh (much lower if enough private EVs are available for time shifting needs) battery costs 12c/kwh or $8B vs a $15B equivalent 1GW nuclear solution. Both last 60 years due to low battery charge/discharge rates and capacity cycle use, with much lower maintenance costs/downtime for life extension costs for solar/battery system vs keeping a nuclear reactor operational. No/minimal operations costs.
It’s very infuriating talking to people about this
Yes. Nuclear shills are frauds who should be frustrated in their theft of the commons.
What conspiracy do you think is happening here? You think I’m being paid by big nuclear power to try to convince everyone that it’s necessary when it isn’t.
I agree with this assessment of battery technology, I’m curious what your thoughts on storage through other means, such as dams, kinetic batteries, heat batteries, that style of thing? I understand that it’d be a massive undertaking, but if we really put our nose to the grindstone we might be able to pull off a good amount of power storage through methods that already exist.
Another myth is that hydroelectric is “green.” It’s absolutely not. The huge amount of land required to build something like the hoover dam or the three-gorges dam is massively destructive to the existing ecology. It’s often overlooked, but land use has to be part of any environmentally sound analysis.
I would say that while the Hoover Dam, or the Three-gorges dam by themselves are acceptable, they are wholly impossible solutions for grid level storage for the entire united states/China. How practical do you think it would be to build thousands of hoover dams?
Other options like kinetic batteries etc, all come down to energy density. The highest energy density options that humans can harness are nuclear Isotopes like Uranium 238, or Plutonium 239 (what powers the voyager probes) After that is lithium batteries at ~<1% density of a nuclear battery. Everything else is fractions of a percent as efficient. Sure there are some specific use cases where a huge fly-wheel makes sense to build (data centers for example) but those cases are highly specific, and cannot be scaled out to “grid-level.” The amount of resources required per kilowatt is way too high, and you’d be better off just building some more power-plants.
Unclear if you’re misinformed or disingenuous.
Hoover Dam does generate power, but it’s not an energy storage project to time-shift intermittent clean energy generation to match grid consumption. That’s known as pumped hydroelectric energy storage, and it requires having paired reservoirs in close geographic proximity with a substantial elevation difference. It’s not an ideal technology for several reasons, but it’s the largest type of grid-scale storage currently deployed. Fundamentally it’s gravitational potential energy storage using water as the transport medium.
A higher-efficiency but not yet fully proven technology also uses gravity and elevation differences, but relies on train rails and massive cars. Here’s one company leading the charge, as it were.
Nuclear isn’t a good option to balance out the variability of wind and solar because it’s slow to ramp up and down. Nuclear is much better suited to baseline generation.
There are plenty of other wacky energy storage ideas out there, such as pumping compressed air into depleted natural gas mines, and letting it drive turbines on its way back out. That might also be riddled with problems, but it’s disingenuous to claim that chemical energy storage is the only (non-) option and therefore increasing wind and solar necessarily also increase fossil fuel scaling.
Again, i’m talking energy density. All those other wacky ideas aren’t viable at all. Yes I know that the hoover dam is for generation, but the idea of pumped reserve power is literally identical to hydroelectric generation. The only difference is we would have a man-made solar/wind powered pump fill the resevoir, instead a natural source of solar power fill the resevoir. Either way, it’s a huge amount of land use for it to be considered “green.”
Additionally I never claimed nuclear power should be used as a peak generation, it should 100% used for baseload replacing all of our fossil fuel generators, with huge taxes being applied to carbon generators.
As an aside:
A higher-efficiency but not yet fully proven technology also uses gravity and elevation differences, but relies on train rails and massive cars. Here’s one company leading the charge, as it were.
This idea is trash and as far as I can tell the hypothetical existence of this is an oil industry fud campaign. The only viable version of this is pumped hydro, which has the land use problem I’ve already described.
Pumped hydroelectric storage obviously works with the same kind of turbines as dams located on rivers, but the land use is far from “literally identical”. For one, I agree with you that damming rivers is generally a bad thing. Large dam sites are chosen to min-max construction effort and reservoir capacity, and usually double as flood control. A grid storage project only needs to hold enough water for its daily power use, and it doesn’t need to be located directly on a water course. That’s not to say that there are unlimited suitable sites, but it’s more flexible.
Pumped hydro storage is quite green in its lack of carbon emissions and ability to time-shift green generation capacity to match grid demand timing. Land use is a consideration, but large anything requires land. You haven’t actually attacked the weakest part of pumped hydro, which is that there just aren’t very many geographically suitable locations for it.
You’ve also neglected to acknowledge the pesky spent nuclear fuel storage problem, which is unsolved and distinctly not eco-friendly. There are potentially better paths available such as the thorium fuel cycle, but they all either have no economic traction or are actively opposed by various governments (which don’t have any good solutions for existing spent fuel).
The solution to nuclear waste is recycling it, which was something France has done quite successfully. The US can’t do it because of cold-war era treaties, but realistically it’s because Nuclear power is the only thing that can threaten fossil fuel primacy in our society and obviously there are trillions of dollars in the fossil fuel status quo.
As an aside, the aftermath of Chernobyl shows exactly how eco-friendly massive radiation events are, Prypiat is a lush nature reserve now. Human activity is much worse for any given area then radiation is.Non recycled radioactive waste could be incinerated like we do with Coal and no one seems to be upset about it. /s
nuclear power is the only thing that can threaten fossil fuel primacy
Solar and wind are cheap and easy to build now, and a huge threat to fossil fuel primacy, which in turn makes them a threat to the dominance of the petrodollar as the world’s reserve currency. That’s why the Trump administration has gone all-out to quash their momentum.
Spent nuclear fuel reprocessing is theoretically possible but not politically or economically viable at present. Neither is 100,000+ year storage that has been the concept of a plan of record in the US for decades. I’m not saying that nuclear is inherently unworkable, but your net viewpoint doesn’t seem to be based in reality.
The disaster response in Chernobyl was absolutely heroic but also incredibly lucky. If the melted core had reached the water underneath the concrete pad, the steam explosion would have spread the core atmospherically with devastating results. You’re making light of the disaster that was, and ignoring how close it came to being so much larger. Furthermore, the enormous irresponsibility of the Russian military’s damage to the sarcophagus cannot be overstated. If maintaining isolation for a few decades is difficult, there’s just no chance over 100,000+ years.
But I don’t think you’re arguing in good faith, so I’m done here. I hope you can find your way to more nuanced views in the future.
Hoover Dam does generate power, but it’s not an energy storage project to time-shift intermittent clean energy generation to match grid consumption
All hydro is automatically “time shifting storage” when new solar is added to power the daytime. Just turn on the turbines at evening peak full blast, and at night. Average global capacity factor of hydro is 45% because the water reservoir is not sufficient to go full blast 24/7/365. Obviously, hydro time shifting is also highly complementary to wind.
Hoover dam’s water release schedule is driven by requests from water rightsholders further downstream. Power generation is great, but the dam’s primary design purpose has always been facilitating agricultural irrigation.
That said, I bet you’re right that the water flow rate could be varied throughout each day to help balance electric grid needs. I assume that will likely come into play as we get further along the path to intermittent green power generation.
Flooding levels updam is a concern (but not for Hoover) in general. Yes, daily/weekly flow rate downstream is also a concern. But not hourly flow rate.
Building a dam causes massive amounts of ecological damage, plus unless you’re building it in the middle of nowhere you’re probably going to be turning people out of their homes, out of their entire towns. We could never build enough dams to be able to meet demand so even trying would be pointless. You would be destroying huge amounts of landscape for no reason.
Kinetic batteries can only store power up to a point, the more power you want them to store the larger they need to be. Again to compensate for base load you would have to have a either a lot of kinetic batteries or a few enormous ones. Plus they are maintenance intensive since they are giant spinning things, or great big heavy falling things.
Heat batteries are a good idea and have relatively little in the way of downsides, but they only work where it’s hot, not just sunny but hot. So the number of places you can build them is limited.
If only we could get hold of some astrophage or something.
Pumped hydro exists.
Do some quick math. How much pumped hydro in terms of acre-feet would be required to power a hypothetical city like Chicago at night? Where would this theoretical reservoir be built?
acre-feet
I can’t stop laughing at this as a unit of measurement
It’s easier to visualize than 325 kilo-gallons.
I guess if you don’t understand units of water per area, then there is no reason to expect you to be able to do any kind of critical analysis about why “pumped hydro” is a problem.
I am not American, so why would I use an American unit of measurement?
You can use whatever moon-units you want. I prefer to use people-centric units.
Ok, if you want an approximate American unit equivalent to a megalitre think of it as cube that can fit a blue whale
Dude, people can laugh at a term while still being able to do “critical analysis” 🙄 “foot pound” sounds funny too. People can giggle about Uranus and still be astronomers.
But is extremely limited to specific areas with the right geography that are also relatively close to a population centre.
It isn’t so much limited by the geography but is made far more cost effective because of it. A long valley with a narrow exit means you don’t need to build much dam and store a vast amount of water.
As far as distance from populated areas, I dunno, I live in the UK so its kinda close enough not to matter too much.
First of all nuclear energy is a fossil fuel.
Yikes. If words have no meaning, then sure. But there is no world where radioactive elements that come from stars have anything to do with fossil fuels that come from decayed biomass.
I’m pro-nuclear energy in theory. But I’ve got to ask - where do you get them spicy rocks from? Do you have to dig them up from a mine? Do they regularly replenish themselves? Does the energy generation have to be constantly checked for pollution leaks?
OK, they may not literally be fossilised bio-matter - but the end result is pretty much the same. Scar the landscape as you dig, release pollutants as you refine, hope you don’t run out of material, make sure someone else pays to clean up the mess.
Yes mining still exists. Unlike how Solar Panels and Wind Turbines grow like plants and replenish year over year with no other industrial process required right?
But again, you don’t appreciate the energy density that is contained in a reactor fuel. The volume of material is minuscule compared to coal. While oil/gas are a lot better then coal energy density-wise, they have the significant downside of greenhouse gases and causing global warming.
Guessing it would be more practical to have enough solar panels to fulfill energy needs in winter.
Not really. As I say in my article, our roof is full. On a bad day in winter, we might generate 0.5kWh (assuming the panels aren’t covered in snow). So we’d need 20x the panels - there’s no room for that.
Hmm, I missed the part about being maxed-out on roof space. Great article and blog by the way!
To be fully self sufficient you have to meet your energy consumption during the most cloudy days in winter.
2 days storage gives you a 5% chance of a blackout at some point during the year.
4 days storage gives you a 1% chance of a blackout at some point during the year.
You will not get to 0%.
You will not get 0%.
I see we are including the nuclear winter scenarios!
Actually, I was thinking volcanos. They can reduce sunlight over a large area for prolonged periods.
How come we can’t design energy storage that lifts something heavy when there’s excess power, and lets it fall to generate electricity when needed?
It’s an idea that’s been played with a few times, but there are many energy loss points in such a system, as well as logistics for keeping the “stack” from falling over. The best so far is pumping water up to an artificial lake, but that’s still not very efficient.
The energy math doesn’t make sense for grid scale applications with solid objects.
However if you can get water between two places it can work quite well. You need to live close to a big change in altitude and do a bit of geoengineering to create the upper and lower reservoirs, which can be destructive to local ecology, but not as much as a dam.
https://en.m.wikipedia.org/wiki/Pumped-storage_hydroelectricity
You can also use pumped air underwater with higher energy losses than pumped storage hydro because of compatibility of air.
1 Watt is the equivalent of moving 1Kg 1 metre in 1 second.
If you want a kilowatt - you need to move 1,000Kg 1 metre in 1 second. Or, I guess, 1Kg a Km.
Plug the numbers together and you’ll see that you need a massive physical load and a huge distance in order to store a useful amount of energy.
This seems like a way different conclusion than the car * 7.3m / day guy
The secret ingredient is gravity!
Hmm
You got your units confused.
1 Watt = 1 J/s = 1 N m/s = 1 kg m^2 / s^3
Just moving things horizontally changes does not take energy (except for friction). But when we move something upwards, we move it against the surface acceleration of earth of g = 9.81 m/s^2. So we can say:
1 W ≈ 0,1 kg m/s
This means to store 1 kW, we would need to raise e.g. 1 ton with 0.1 m/s. So 1 minute of medium power cooking (1 kW), corresponds to lifting 1 ton approximately 6 meters.
Potential energy (in joules) is mass (in g) times height (in meters) times 9.8 m/s^2 .
So in order to store the 30 kWh per day that the typical American house uses, you’d need to convert the 30 kWh into 108,000,000 joules, and divide by 9.8, to determine how you’d want to store that energy. You’d need the height times mass to be about 11 million.
So do you take a 1500 kg weight (about the weight of a Toyota Camry) and raise it about 7.3 meters (about 2 stories in a typical residential home)?(this is wrong, it’s only 0.001 as much as the energy needed, see edit below)And if that’s only one day’s worth of energy, how would you store a month’s worth? Or the 3800kwh (13.68 x 10^9 joules) discussed in the article?
At that point, we’re talking about raising 10 Camrys 93 meters into the air, just for one household. Without accounting for the lost energy and inefficiencies in the charging/discharging cycle.
Chemical energy is way easier to store.
Edit: whoops I was off by using grams instead of kg. It actually needs to be 1000 times the weight or 1000 the height. The two story Camry is around a tablet battery’s worth of storage, not very much at all.
So do you take a 1500 kg weight (about the weight of a Toyota Camry) and raise it about 7.3 meters (about 2 stories in a typical residential home)?
Honestly that is way, way more reasonable than I was expecting. This isn’t half as bad of an idea as I thought it would be
Pumping 1500L of water up into a tower doesn’t seem difficult or expensive.
Sorry whoops I was off by a factor of 1000 because I used grams instead of kilograms. The Camry needs to be raised 7.3 km. Or you need 1000 of them in one house.
There seems to be an error in your calculation: Up to the 11 000 000 kgm required it is correct. However the Toyota Camry with 7.3 m provides only 11 000 kgm. So you miss a factor of 1000. You would need 1000 cars lifted the height of your home. For just one day (or a few days in more efficient home)
You’re absolutely right.
I don’t know why I thought to use grams instead of kilograms. I knew kg was the base unit for these conversions but just slipped for some reason.
Actually, yes. Lifting the weight of a Toyota Camry 2 stories seems reasonable for a day’s worth of energy storage for a house.
I’m not sure how expensive the lift and generator will be, but the weight itself can be anything that’s sufficiently heavy.
You say chemical energy is way easier to store, but is it really easier and cheaper to store the energy needed for a home in a chemical battery?
is it really easier and cheaper to store the energy needed for a home in a chemical battery?
Yes. A 5kwh battery is about 50kg and smaller than a carry-on suitcase. String 6 of them together and you’ve got 30 kWh stored with no moving parts. Anker has that for about $15,000, maybe $30k installed.
How much does a 3-story elevator cost? What about one that can capture the stored potential energy on the way down, and not break down?
And not just that, but safety and cheapness akd accessibility of the materials. Water is pretty cheap and common. If it spills, probably no big deal (flooding notwithstanding) unlike battery acid. Not as likely to explode (sometimes steam explodes stuff).
Hmm… this might be easier to do with an electric car. Put it on an inclined track, and then drive uphill to store energy, and go downhill to release the energy.
You would just use the car wheels itself if you’re doing all that - how do you think it would store energy driving uphill?
Well you want some weight which is why I’m suggesting the whole car but sure if you want some custom solution you can build something better.
We have, pump storage hydropower: https://old.reddit.com/r/askscience/comments/chm70g/askscience_ama_series_were_from_the_pacific/
Basically they store water up high to act as a battery. Some combine this with a solar lens and turbine (can be sourced from old tvs, it’sa Fresnel lens for a solar death ray) and boil the water with the sun/ray to get it to evaporate and then condensate in the elevated position.
battery and solar at the home level is what makes the most sense.
60% of the planet lives between the subtropics and tropics. There is way more than plenty of sunlight hitting our earth to support all of our energy demands, and any naysaying around battery technology is missing the forest for the trees.
Need to wire the whole world. Let’s go.
The most straightforward path to world peace is to increase the global supply of energy to the point of negligibly low prices
I believe it would attribute to cheaper of free energy and to more peace. I am agreeing with you.
And I imagined a all encompassing " worldgrid" across all continents and islands. We did it with phone networks, now we should do energy.
I like the idea that the real reason for all of the atrocities is that people don’t have enough power to play Xbox.
Author’s diagram is about summer. Fall, winter, spring is about heating-degree days. If you’re heating your home with electricity, you’ll not get there with batteries.
So, working towards a solution, there are other ways to store excess energy than in batteries. One example is sand, which can be heated to very high temperatures. Insulate a sand container well and its storage can do a lot of home-heating.
We’ll need to put a lot of different methods into use. There are many practical ideas out there, and they’ll need to be tried.
There was an article posted somewhere on Lemmy a few months back where someone tried to do similar calculations for the US as a whole. What I took from the result was 95% renewable was achievable and still cheaper than fossil fuels. However the over provisioning of renewables and over double the storage needed to reliably achievable 100% made that infeasible with today’s proving and technology. Basically you can install storage to cover when the sun is not shining but it’s much more difficult to cover weeks of gloominess
Solar isn’t the only renewable choice, though. It’s just the easiest to do on an individual level. Also, there are plenty of areas for which weeks of gloominess will never (on human timescales) be an issue.
It’s practical for someone with limited space for panels on a small room, but I ran these calculations by moving almost all loads to daytime, sizing the panel array to the (minimum daily usage + efficiency losses) * buffer factor for days long storms or equipment failure.
Start with the comparitively cheap panels if you have the space, move electrical loads to the daytime and design the house for thermal momentum, and size storage to the minimum inclusive efficiency losses times buffer. If you have the roof space the panels are the cheapest part and you should usually way, way over panel.
The most important thing is having thermal mass enough or living in a climate that allows your home to not need thermal input or extraction at night. Heat is expensive and exponentially moreso if you need to produce it from conventional storage.
It is possible that, not too long in the future, every home could also have a 1 MegaWatt-hour battery. They would be able to capture all the excess solar power generated in a year.
Braindead strategy, that most likely is discrete fossil fuel shilling, for purposes of making decision inpractical.
The cost of storage as a baselines is how much you can charge/discharge per day. Bonus for smaller (= cheaper) that can have more discharge/charge than its capacity per day. Plus the resilience/reserve capacity value which is a convenience factor. Resilience alternatives include fire places or gas generators (that are not expected to be used often) which tend to be cheap per kw. But noise, smell, variable costs, and startup effort are all inconveniences. Driving an EV to a public charger can be a similar inconvenience level to a generator for resilience value. If a 1mwh battery is used 10kwh/day it costs 100 times more per kwh than a 10kwh battery.
OP gives an example of 12kwh summer use (no AC?) which is very high for most people, but can include cooking and floodlights.
The braindead analysis parts are “because 100 days of 10kwh surpluses happen, I need 1mwh battery”. Actual battery storage requirements are the lowest theoretical winter solar production over 1-2 weeks, together with running pumps for heat (stored mostly in fall) distribution. A 10kwh/day maximum deficit for 1 week straight, with 60 day average deficit of 5kwh/day (without requiring additional heat input), means that any consideration for a large static battery should stop at 70kwh. This is sharply reduced with 1 or 2 EVs where summer surpluses are free fuel, and EV provides backcharging at 3kw whenever needed. 30kwh battery is plenty to charge an EV overnight (300km range for small car) before next day’s sunlight exceeds needs. Even less battery with 2nd lightly used EV, but 30kwh will be cheaper than un-needed EV.
Instead of relying on batteries for heat generation, which is where $100k 1mwh delusion proposition comes, heat generated from solar stored in under $1/kwh hot water and dirt storage. Outside of winter, this also provides completely unlimited showers and hot tub use, and a $10-20k heat pump and heating system (fossil fuel systems often cost the same) and insulation improvements is the the unquestionable non-distracting path.
That scales down to the home level easily. Box filled with cement dust, dirt, sand, gypsum, gravel is all free material. Water gets more heat lift from heat pumps, but can’t store as much heat in a volume as dirt. Both are highly complimentary, because delivering hot water to everywhere in a home is efficient, quiet, dust free, heat. But if you are lucky enough to have centralized option, that is easier.
hot water to everywhere in a home is efficient, quiet
Have you never lived in an apartment building?
I don’t know why we haven’t come up with better solutions for piping. Or maybe it’s just because this building was built very cheaply. But anyway… the pipes make quite a loud banging sound if you shut them fast enough. And a lot of whoooshing in the walls just when using hot water.
High rise apartment buildings have a challenge with pumping water up more than 3-5 floors. This can be solved with intermediate storage on floors, but for high rises, forced air is the usual solution. Heat storage still works well enough with forced air, but water is much better due to internal piping through heat source, where air volume is harder to do there, and if gaining heat from outer shell, then insulation meant to keep heat in is not as good at heat transfer. Water is most perfect heat fluid in world. Air not so much.
And a lot of whoooshing in the walls just when using hot water.
This doesn’t apply for heat delivery. Tends to be continuous. A faucet is different.
This doesn’t apply for heat delivery.
Pegging your pardon, mister.
It takes an extremely large volume of any of these materials to store any useful amount of heat to get you through a cold night or something. The volume looks more like a room than a box, unless you can somehow make it molten that is
I did math for Toronto, Canada. 2000l of hot water was enough (2m3). Winters here have gotten cloudier from great lakes warming. Instead of more water as a buffer, dirt is much more space efficient, and just needs the hot water routed through it to get heat transfer.
The volume looks more like a room than a box, unless you can somehow make it molten that is
If hydronic heating system was already being directed towards outer walls instead of straight up from water storage, then a tall “hot dirt” storage, and dual cold water mixing valves (pre and post dirt flow) next to each other, it’s less in additional storage costs per heat unit than water, though it does use more electricity to input heat compared to heat pump.
No need for temperatures higher than melting/softening point of copper to get useful heat storage for a home. Just water can be enough if you have the room.
Interested in your calculations for 2kl, do you have a small, highly efficient house? For my house, IIRC I needed something like 3000L (glycol, so a little less capacity than pure water) at 30C to maintain 16C in the house for 12h. That’s calculating losses at average winter night temps of -8C and a relatively efficient adobe house of 150m2, and including estimated losses for a buried tank surrounded by foam installation.
Roughly: 3kw/hr worst case home losses, times 12h is 36kw, 36/0.00114 kWh/L is 31.5k liter-degrees, 31.5k/14 degree temp drop is 2.2kL, so 3kL inclusive losses. Experimentally verified heat loss calcs after installation of the 9kw resistive boiler which used around 30kwh for the coldest 12h winter nights which ends up being about a 50% duty cycle at the medium heat setting of 5kw. Yes my electricity bill was $500/month for two months a year when pulling it all from the grid.
If I was building the house i’d spec a 1m mixed layer slab and run two layers of hydronics through it. The bottom layer is the heat storage side and the top layer is the home comfort side. The waste heat from the storage dumps into the house and you’ve got a ready made heat battery right where you need it. Run your resistive boiler while the sun is shining to get your heat battery toasty and at night use your pumps to move the heat up when home envelope losses are more than the heat battery leaks up through the floor.
Heat pump didn’t make sense in my climate because there is no need for cooling, when heat is needed it’s usually way too cold for heat pumps to be efficient, and we have basically unlimited sun and therefore energy. High desert New Mexico.
I found the book “heating with renewable energy” helpful when designing my system
It’s been a while, but in general based on having too much solar tilted +15 from latitude to maximize winter production, and relying on 14 sun hours/week as a minimum, even if 20 -22 would be expected average. While solar has fixed bs/costs, an extra 300w is fairly cheap, and adding to that often less expensive than more btu (or kwh) storage, or more insulation. Monetizing summer surpluses into crypto (back then) or gpu dataserver rental, also means never having too much solar. Full ROI on all solar, compared to overdoing it on heat storage.
I looked into one of these thermal systems for my own place but the outlay is just massive for the 11 weeks a year I really need heat, and the rest of the year it’s just a stupidly oversized hot water heater that is cooking my glycol and DC pumps.
I ended up paneling up and putting a dumb 9kw resistive boiler for my hydronic floors. The house slab is the battery and although inefficient in terms of strict energy use, winter sun on my cheap pallet of panels dumps plenty into the slab all day. I do have to light the stove if we get a snow storm for a day or two though
Yes. Hydronic flooring is cheap at construction time. Complicated if drilling into finished ceilings/floor with thicker under floor space making. But instead of 9kw of winter electricity you are forced to import, it is free fall surplus generation. 100w of pump circulation.
But you are saying, a resistive boiler made more sense than a heat pump, with the hydronic floor conversion. At first I thought you were just saying resistive heating electric floor. The latter, to me, would be the cheapest capital outlay conversion, and then a heat pump would beat a resistive boiler on operation costs if hydronic.
Did you investigate all of these alternatives?
Yeah I already had the hydronic floors and ran numbers on heating the floors off thermal solar panels, propane, heat pump, and the resistive boiler. The thermal panels made the least sense because they are useless eight months of the year.
The heat pump might have worked but when I really needed it my semi-outdoor closet would be in single digits and full of water supply pipes so the heat pump would be least efficient when I needed it most, and would not help keep the closet warm.
The resistive boiler meant I could add a bunch of panels to run it during the day and get the floors up to 85F, then run all electric appliances with no worries during the day the rest of the year with the extra capacity. So instead of being net positive generation from 10am to 4pm in summer, its now 8 am to 6pm with way more than I can use at peak.
(OP here) Sorry mate, are you accusing me of being in the pocket of Big Oil? Here’s everything I’ve written about solar over the last decade - https://shkspr.mobi/blog/tag/solar/ - feel free to point out where I’ve said “yay fossil fuels!”
I didn’t include AC because that’s not a thing in the UK.
Oh, and I don’t use electricity for primary heating. Solar thermal is pretty useless in my part of the world because you don’t need much hot water in summer (mmmm! Cold showers!)
As I said in my post, this is a purely theoretical discussion about what future technology might look like. Your argument is like someone from 2001 going “a recordable CD can hold 650MB - so you only need two for a really long car trip. There’s no way people in the future will have 1TB hard drives! For anything else, just use AM radio.”
Basically, one of us is braindead - and I’m not so sure it is me!
Ok, to be polite, you were just mistaken in portraying a 1 mwh battery as a reasonable idea. It is just so absurdly stupid that motives for the proposal need to be looked at. I accept your admission of stupid instead of evil.
I’m sorry you didn’t read my article. If you had, you would have seen me say…
Remember, this is just a bit of fun. There’s no practical way to build domestic batteries with this capacity using the technology of 2025.
And
Is this sensible? Probably not, no.
And
remember, this is an exercise in wishful thinking.
At no point did I say it was a reasonable idea. I went out of my way to demonstrate how impractical it was.
I accept your admission that you didn’t read my post means you are stupid rather than evil etc.
But there are sensible paths to going off grid. Why you would write about an impractical fantasy path was my puzzlement.
There’s this thing that writers do called “thought experiments”. It is a form of intellectual exercise to examine what happens at extremes.
It helps us explore an idea by future gazing and, yes, getting a little ridiculous. Imagine someone in 1975 saying “what would the world be like if we all had Gbps Internet?”
There was nothing of that speed available for domestic use, but thinking about an “impractical” technology means they can ask “would video conferencing disrupt the travel industry?”
That’s what I’m doing. 25 years ago home solar was too expensive to be practical. 25 years ago having a 5kWh battery in your home was close to impossible.
In 25 years time will batteries be cheap enough for us each to have a MWh in the loft? I reckon so. What does the world look like when every home has the ability to be energy self-sufficient using solar?
In 25 years time will batteries be cheap enough for us each to have a MWh in the loft?
At $20k/$30k per mwh would make 100 kwh $2-$3k. 100kwh would still be more than you need, and so it is pretty affordable now.
There are some cheap/“bad discharge rate” chemistries like iron air. They’d be too heavy for loft, but could be foundation walls or crate in your back yard. Not a technology likely to be mass produced enough, and shipping costs very high.
What does the world look like when every home has the ability to be energy self-sufficient using solar?
We were at this point in 2019. The raw materials are 1/3 the price today. 100kwh is already more than you need. Corruption of tariffs, and artificial price barriers by electric monopolies and their regulator minions inflate prices in our countries.
I don’t need to get through winter, I just need to get from dusk to when the cheap energy is starts. Currently that’s about 4kwh - or a small portion of my car battery before or recharges on the cheap rate.
We have a whole home generator that runs in natural gas. They’re not the quietest things. Been tossing around the idea of having batteries added so that when the power cuts we go to battery. Then when the battery gets low the generator cuts on just long enough to charge the batteries. Wash rinse repeat.
What a detailed and rigorous inquest into a question he admits from the outset is absurd and not applicable.
You can plug your system into a free platform like opensolar, which allows you to play with the design to see what the effect of upgrades would be during the course of the year.
Why limit it to an electric battery rather than some subterranean storage where the excess electricity is turned into stored heat.
Make a flow battery
