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‘If 1.5m Germans have them there must be something in it’: how balcony solar is taking off
(www.theguardian.com)
this post was submitted on 22 Dec 2024
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While the panels are important, the main reason why its important to also have the battery component is because most people tend to work when daylight is out (where the house is theoretically using up the least amount of power) thus, if one didn't have a battery, its pushing the power back into the grid. At the same time, power usage tends to spike when it gets closer to night, where solar is ineffective, and relies thus back on the grid if there's no battery. While personally(not the original person) would never claim it does essentially nothing, the battery component is extremely critical for energy independence as the time period people want to minimize grid usage the most should be during the peak hours, which inconveniently is when the sun is down.
These units do not push electricity into the grid unless their fail-saves are bypassed deliberately or fail catastrophically.
Anyway, no, it's not that important. You already have a battery at home- your entire home. If you're overproducing electricity then you can convert it to another medium such as hot or cold air depending on the time of year and save on AC. You can run preload your washer and make it run when production is at peak automatically. Be creative. Most people will not be overproducing electricity with one of these kits.
Additionally, local energy independence is not about being off-grid, it's about being able to charge and use a radio or the internet in an emergency where the grid is out. A solar panel on the balcony provides that, it makes you independent of the grid even if you're still using the grid to run your washing machine and the oven in a non-emergency scenario. A battery will only be a boon to you if you expect the grid to go out for days at a time regularly or if your kit is large enough to actually overproduce at any point, which again, most don't; they supplement.
I don't understand what you mean by this. The time people want to minimize their grid usage is during the hours of 16-19 which is peak usage and when electricity is most expensive. These panels will still provide a decent supplement in that time during the summer half of the year.
In summary, I just don't think a battery is going to add much unless you're expecting to overproduce regularly which a balcony panel isn't gonna do.
edit: I should mention that the larger kits do come with battery options, because those could be expected to overproduce, and thus would be useful.
What are you talking about? Of course, energy that isn't used in the household is pushed back to the grid.
No, that’s not how it works in the general case. There are ways to setup a house to back power but it’s more complicated than just plugging it in.
Without proper safeties in place back flowing power to the grid becomes extremely dangerous for line technicians
On loss of power these inverters cut off within 20 ms or so. These are grid-tied, not insular (though with hacked firmware some of the models can be made insular-capable).
20ms are exactly 1/50th of a second i.e. our grid frequency I think there's some more leeway. A whole oscillation being gone surely is suspicious and you want to shut off but that might take another millisecond or two.
It's not a hard realtime cutoff spec, more a relais native actuation time. And from the behaviour I've seen they are ramping up slowly over minutes when the mains power is back, which seems a sensible thing to do.
Maybe just look at how these inverters work before babbling about. These kits all come with standard off the shelf micro inverters, or rarely bigger string inverters, and will feed back up to 0,8wk into the grid if the energy is not used in the household. If the connection to the grid is lost they turn off within less than 50ms, making them completely safe for line technicians
Even more precisely: If the energy isn't used on the exact phase the inverter is connected to. You might be simultaneously backfeeding 800W on one phase and draw 3000W from the grid for your kettle on another, pretty much every single installation (at least in Germany) is three-phase at the main breaker panel, then distributing (and three-phase for the stove). Good ole Ferraris meters only record the total sum (the wheel would turn at the speed of 2200W) but you're still using grid infrastructure which is one of the reasons why the installations have to be small: Because your utility can't bill you for grid usage.
Yes that’s the setup I was talking about. Not every grid in every country is setup for this though
So what you're saying is that the general case is that it feeds back into the grid unless there are additional measures taken? But at the same time, it's not the general case? Huh?
Which is why, where I live, you have to register your devices with the utility company.
I was saying the general case is that they aren’t tied to the grid, but that they could be setup to do so. I’m almost definitely wrong about how often these are tied to the grid though.
Yup! I’d be shocked if a country didn’t make you inform your utility.
Do you know how these kits work? The whole point is that they're plug-and-play. If the feed back into the grid, they are not plug and play and will require coordination with your power company lest you accidentally kill someone because you're backfeeding into a line they turned off so they could work on it.
The kits have built-in measures to avoid backfeeding, or they would be illegal. Where I live, they've been deemed so unsafe, failsafe or not, that you're just not allowed to use them.
They cannot back feed when there is no grid power, yes. But they cannot differ between power used inside the house or outside the house. They can and will definitely push power back out to the grid as long as they detect grid power from other sources.
https://en.m.wikipedia.org/wiki/Grid-tie_inverter
https://www.inverter.com/what-is-a-grid-tie-inverter
These kits absolutely can push power into the grid, usually with payment for the generation. Just because they may not be allowed where you live doesn't mean they don't exist.
If you happen to have an old Ferraris meter without a ratchet it can even run backwards when you produce more than you consume. And, of course the 800 Watt EU limit is a worst case limit. If you feed in on a dedicated (no other consumers or generators) line with its own fuse and sufficient wire crossection you can feed in up to about 2 kW. Be aware that the fuse will not trigger if you have a near-short while you generate peak or near peak which can cause overheating and is a fire hazard. While none of the above is legal and you will lose house insurance in case some electric-related fire event occurs it is safe technically.
Yes I do. Had one for some time before we got our own house and ramped it up to a "real" 8 kWp array.
Which is exactly why there are harsh regulations about the index of these things in Germany. Before you plug it in, you have to register exactly where you're plugging what in.
Why dont they install switches on both ends of the line? Seems obvious. Power is no longer unidirectional.
Decentralized grids are the future.
the suns only up during that time period over the summer. during other parts of the year, it's only partially up. If you have to go for a specific time of the year in order to fix a problem, then it hasn't fixed much of the problem if it only addresses 1/4 seasons. solar is often not that strong during peak usage. It's basically effective if you have a lot of appliances at home that are timed specifically to run when most people are away, which is the part that you have to train an audience to do.
These days we have lots of people with home office. There are appliances like refrigerators and home electronics which contribute to the domestic baseload. With battery buffering and higher production capacity you can flatten the generation peak and increase self-consumption, for the price of longer ROI.