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Home installations just cut it off. In both of these cases.

I did my own battery backed installation. When I'm underproducing I can shed load (I turn off my AC - almost always that's enough, and it's automated by relay). When I'm overproducing (ex - my battery is full and my load is still not enough to consume input) I just don't let the panels generate more current than I can consume.

Managing grid scale power is different concern, and not particularly relevant to small household generation. Especially not relevant in the 800W category for "balcony solar" (which is much smaller than what I'm working with).

Solar is fucking coming, whether you continue to shove head into the ground or not.

It's just way more affordable. Getting easily more affordable as batteries continue to improve.

I honestly doubt I'll still be connected to a local utility grid for electric 10 years from now, and I live in a region of the US that has considerably cheaper grid power than most areas.

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My current EV has a 38kW battery.

When it's too worn out for car use (SoH around 60-70%), it's still perfectly enough to run _everything_ in my house for multiple days - except for the electric sauna, and I'm smart enough to turn it on if there are production issues :D

There's a reason why EV's will never be as cheap as the cheapest ICE shitbox. Just the bare metals in the battery are worth thousands when recycled, even more if the battery is still viable.

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The value of the metals will depend a lot on the battery chemistry. LFP batteries don't need nickel or cobalt and sodium-ion batteries can also replace the expensive copper foil on the anode with cheaper aluminium foil.

I'm somewhat sceptical that used batteries will ever be worth much other than as scrap given the cost and complexity in testing, installing, and managing a mixed set of used batteries in larger installations.

With new batteries halving in price every 4 years or so the value of the raw materials in old NMC batteries alone should make it economical to sell for scrap and buy new batteries for stationary use cases after 10 years or so!

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If you ever are looking to implement that EV battery as house backup, this repo might be useful: https://github.com/dalathegreat/Battery-Emulator

I did mine with it and old leaf 24kwh battery (~60k km). After all the safety margins I get ~15 kwh out of the battery.

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Sorry, the consequences are too dire for me to delegate household battery control to a vibe-coded project.

I'm curious what your home insurance provider has to say about your installation.

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This is not how curtailment works.

Curtailment is when an energy company has successfully bid on delivering electricity for the next block of time (an hour, for example) but it can’t provide that agreed amount of power because it would overload the grid. There are various reasons why that would happen: faults and unexpected lack of demand, for example. In that case the company is paid for the energy it was contracted to deliver, only for that period of time, even though it did not provide power.

It is wrong to say that overproducers HAVE to be paid. They don’t. They only have to be paid if there was an agreement to buy that power but for whatever reason the grid can’t take it. Normally if there is a generation surplus, the cheapest companies will win the bid to provide power and the others will simply not be paid.

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The utility SHOULD ensure there is enough power for the worst case. Which is why they will sometimes pay someone to not generate power.
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> When solar OVERproduces you have to literally pay someone to consume that energy,

Can't we just throttle the solar panel? In a worst case, you just pull the plug. It's not like a nuclear power plant which needs to be shut down carefully, or am I misunderstanding something?

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Yes that's exactly how it works, it's called curtailment.
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You can limit amount you feed back into network.

Not sure how is situation with home installations, factory i work for runs 150kw plant for our own consumption and don't bother with selling, but i know that we can set up how much we want/are allowed to feed back.

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> When solar OVERproduces you have to literally pay someone to consume that energy, most probably wind farms, which could be producing energy instead.

You don't have to do this with solar, you can just disconnect the panel and have it go a bit hotter. For producers that have a long-ish bringup time, yes, you might need to do this at time.

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The situation is slightly complicated by dispatch order, and domestic solar isn't usually dispatchable at all. Grid-scale farms are.

Wind farms don't consume energy, but there is a real issue with how often they have to be "curtailed" (paid to turn off). That is to a great extent due to issues with grid connectivity between Scotland and the rest of the UK, which are (slowly) being worked on.

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Wind curtailment is the deliberate reduction of electricity output from wind turbines, despite their capability to generate power under existing wind conditions. This practice is typically implemented by grid operators to maintain the stability of the electrical grid or to address specific operational constraints.

https://www.enlitia.com/resources-blog-post/what-is-wind-cur...

"paid to turn off" Wind energy providers in some countries are compensated for curtailment, this a form of subsidy for renewables. It can be payed directly by the goverment, or it is added to the price of electricity for consumer.

https://www.cleanenergywire.org/news/renewable-curtailment-c...

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My understanding is that all inverters sold at this moment, in the EU, need to have demand response and grid curtailment mechanisms by law.
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>you have to literally pay someone to consume that energy,

Here's the thing. That's a rule and not a technical problem. Absolutely no reason to do this other than rules and regulations.

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Yes, but even more so, it's a good sensible rule!

People don't even bother to argue why it's bad, they've just seen so many headlines telling them it's bad they don't question it.

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I'll question it. Why does it exist? Why can't we just shut off the panels or dump excess energy into a metal rod? Why do we need to have a buyer at all?
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It's not a buyer, people are paid to take the energy that would otherwise be wasted. And when energy use is shifted it means you need to generate less later, saving money.

The people who pay that cost to the people using the energy are people running energy generators that suffer wear and tear when they ramp down.

Or sometimes it's a subsidy for the use of clean energy being passed on to ensure the clean energy is actually used, not wasted.

All upside, no problems at all.

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Because otherwise the incentive structures for solar-as-baseload, sweeping the actual cost on the consumers, collapse. The system is built on putting equality sign between oversubscribed solar and coal/gas backups during times of undersubscription.
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Cheap home solar installations usually have a disconnect- do they not use those in larger scale installs?

I'm also surprised they aren't using batteries to capture overproduction. They've been clutch in the US, and we're not exactly pushing the envelope of green energy nowadays

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Here in Finland electricity prices can drop to under 1c/kWh due to renewables, basically every time it's sunny and/or windy electricity is practically free (the transfer costs are static though).

A few times the price has actually been negative, people got paid for using electricity due to overproduction =)

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In Finland you produce more electricity from nuclear energy, than from hydropower, wind, or solar.

https://ourworldindata.org/grapher/electricity-prod-source-s...

The amounts for year 2025: Nuclear 32 TWh, Wind 22 TWh, Hydro 12 TWh, Solar 1TWh.

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There will be connected batteries in every home solving this problem faster than the fossil fuel lobby can come up with a new talking point about why it’ll never work.
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I'm not convinced we'll ever see mass deployments of batteries to homes, not because of the fossil fuel lobby but because of the economies of scale from installing grid sized batteries at strategic points in the transmission network.

In California grid scale batteries have capital costs of around $125/kWh to $155/kWh while a home battery might be 20x that including installation.

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Inverters can be configured with export limits to limit, or entirely halt, energy exports based on market or grid signals. Term of art is "curtailment."

https://en.wikipedia.org/wiki/Curtailment_(electricity)

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No you don’t, you could just ground it. Paying them is a choice.
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When there's an OVERproduction of energy, that really means there's an UNDER-availability of storage. Battery tech continues it's march towards cheaper prices, and alternatives such as thermal storage are making inroads as well.

It borders on criminal to have abundant energy production be disservice.

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I'm no energy markets analyst, so take this with a grain of salt, but I think the next major breakthrough for solar (not the slow, inevitable rollout we're seeing now) will be when somebody figures out an economical way export this periodic overproduction. There is basically never a time when humanity as a whole has an overproduction of free energy, but at present we also don't have a way to make money turning this surplus into a tradable product (like oil, coal, LNG, etc.) because all the electric-powered processes for making such products (ammonia, methane, primary aluminum production, etc) require big hunks of capital equipment that lose money unless they're operated more or less continuously. Battery, thermal, pumped hydro, etc. help here, in that enough of it can theoretically turn off-and-on solar/wind power into a continuous load to power your aluminum smelter or whatever.

Even better though, would be a cheap electrically operated methane plant that you could afford to run intermittently. This, plus a peaker natgas generating plant make, effectively, a battery of infinite size, or you can sell it to any of the many eager buyers of natgas.

Building a small, prefab, plant like this, if possible, would seem to be mainly a problem of scale, and therefore it seems likely that China will get to it pretty soon.

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"If you find dollar bills on the ground you need to pay someone to collect it as litter"

Charge batteries, do electrolysis, or a multitude of other uses (I know some companies do that already)

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This is literally the only sane usage for hydrogen outside of industrial uses, when you have a massive excess of renewables, use it to turn water into pressurised hydrogen.

And when the prices go up, you run that through a grid scale fuel cell and feed it back to the network.

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Storing hydrogen is no small feat. Especially for long duration
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Used 240w modules built in 2010-2012 are worth $60-100 CAD at the moment in small quantities. There will be hundreds of thousands hitting the market (as long as they didn't hit the ground with careless removals) in ~2030+ as microFIT contracts in Ontario expire.

There is no clear path to switching these arrays to Net Metering, as of yet. Prepare for all sorts of unrecycled solar panels and potential loss of renewable capacity that is already installed.

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Net metering is really, really smart when the installed base is small relative to the fossil fuel power plant capacity. But it doesn't scale forever. Once it gets up towards 20-40% of the fossil fuel capacity, it goes from an asset to a liability.

Suppose I have a 100MW gas turbine. And suppose there's 1MW of solar installed in my generation network. I don't really care if I sell 80MW at noon and 90MW around dinner time and 50MW through the night, or if instead it's 79MW at noon and 91MW at dinner and 51MW at night. The gas costs about the same irrespective of when I burn it so a bit of a fuel shift doesn't really matter.

But take that 1MW and turn it into 20MW and suddenly we go from 80MW at noon to 60MW at noon, 90MW at dinner to 110MW at dinner and uh oh. You see the problem? Whatever losses I endured at noon I don't get to make up for at dinner because my plant only goes up to 100MW and now we're not just shifting when we burn how much fuel, we're literally having to shift the power generation to a different plant.

Is this example precisely accurate? Absolutely not. But it helps you get a feel for the problem of net metering at scale. The grid can act as a battery for a few % of total generation, but by the time you hit some number, maybe 20% maybe 40% net metering turns from a cool math trick to a real cost on the grid.

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Net metering only makes sense as a way to incentivize solar installations. Looking at the economics, it's not something any utility would offer willingly.

It's like if the grocery store let you give them milk for a credit at full price. (Let's ignore the sanitary/health/quality issues that would come up.) You decide to buy a cow and you drink that milk. Sometimes you need more than your cow can give so you buy extra from the store. Sometimes you need less and you sell the extra to the store. Long term, you use as much as your cow produces on average, so you pay the store nothing. But the store has provided a valuable services to you and has incurred expenses in doing so. They have to keep the lights on and maintain a building and pay workers to handle your transactions but they make no money from you. The only way it would work at all is if they made enough money from their non-cow-owning customers to make up for it, and that can only take you so far.

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> It's like if the grocery store let you give them milk for a credit at full price.

I know of quite a few places where through net metering you don't get full price, you get the wholesale rate for your production which is significantly less.

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Could you elaborate on this? Why would people remove a working solar system?
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Buildings get torn down. Roof needs a replacement and the owner doesn't feel like it is worthwhile to redo the solar install for panels that only have 5 years of warranty left, or maybe they want to replace them with higher power models with a fresh warranty. There are any number of reasons why someone might need to offload otherwise functional solar panels.
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Currently used solar panels are a hot commodity, with many groups selling them by the pallet, because 10 year old solar panels are still efficient enough to easily pay for themselves. Very few installations will care about specifically how many panels they want, they just want a nameplate output per dollar figure.

Old inverters might not have a second life though.

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