Neat breakdown with data + some code.
Factorio has prepared me for þis challenge…
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.
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.
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.
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.
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.
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 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).
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.
As is mentioned in the article 😉 What is also mentioned is the fact that battery prices are going down. Soon it seems they’ll be down to $10/kWh!
There’s also alot of new battery tech on the way.
There will be a market for batteries at home, and they will exist with the best suitable tech for it - and it’s probably not lithium.
How many years, I dont know. What will it be, and who will do it, no clue. Otherwise my stock portfolio would look better if I knew these things haha.
I wish the second-hand battery market were more lively. Using half-worn car battery packs seems optimal for home use.
It is. Some of them are getting snapped up to help with powering factories.
I think this is car companies using the incoming battery packs from replacing worn out packs. Time to look it up…
https://www.autoblog.com/news/toyota-just-found-a-clever-new-use-for-old-ev-batteries
This is the article I was thinking of. It’s more of an idea than a common use case to use old packs to help power factories.
Sodium batteries?
BTW that’s the wish for trend line, $10/kWh right?
I mean… they are at ~$16/ kwh right now, so…
https://www.alibaba.com/product-detail/CATL-75AH-220Ah-Grade-a-Sodium_1600972483761.html
No?
I have seen some wild priced on Ali, in your link the 75Ah and the 210Ah are priced the same, so I guess it’s for the smaller one, 30€ for ~0.225kWh or 133€/kWh.
Could be wrong ofc, but it sort of fits what I thought it would roughly be.
I mean even ~133/kWh…
Whats an average, perhaps even gratuitous, level of consumption per household? 24kwh if you are running a clothes drier and an AC nonstop? Lets go nuts, say you are a DIY enthusiast and hosting your own servers, so 36kwh daily.
3192€-4788€ to be and you can be effectively energy independent with a small solar system.
Triple that and you are truly energy independent are any where south of the English channel. I mean obviously its money out of pocket, but its a fixed cost that you pay now, instead of a variable cost that continuously goes up. It just seems basic.
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) .
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.
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.
I recently got a solar system and came to the conclusion that if you can sell power back to the grid (not everyone can) for some reasonable percentage of what it costs to buy it, then it will always be worth it to be connected (assuming you already are).
Quite simply, if you have enough solar capacity to get you through the winter (no house is going to have months of battery storage), then you will always be creating far more than you need in the summer. Selling this excess will easily cover any costs associated to being on the grid.
Also at current prices batteries are good for backup power only, it’s always cheaper to sell excess power to the grid in the day and buy it back at night than it is to have battery capacity to get through the night. I worked out it would take 40 years for our battery to pay for itself (assuming the battery kept a constant battery capacity for 40 years…) but less than 10 years for the rest of the system to pay for itself.
We can’t, but we can do net metering, meaning we can offset costs but not get paid. So the best investment is to pay nothing through Dec. 31 and keep costs manageable at the start of the year (net metering ends with the calendar year).
Net metering is potentially better, as you are effectively getting free night usage based ob day generation. My setup pays me, but I get paid 20c per Kw (NZ dollar) and pay about 30c to buy, so there’s a 10c difference. Just as long as whatever you lose on 31st Dec is not too high, you’d be better off than me.
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)
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.
