I would assume that electrical code manadates disconnecting the house from the grid if there is solar and no grid power, but (where allowed) the solar can feed back into the grid when there is power. If power out means solar out, what’s the point? Grid power is not a requirement for the solar to operate. What sort of switching electronics would do that?
Hate to sound like I’m coming back with a “you’re wrong on the internet,” but…
When reading through the manual for my Tesla made solar inverter, it requires grid power to operate. There is a circuit that includes a solid state switch that is normally open. When grid power is detected the switch is powered and closes so electricity can flow from the panels to the inverter.
When the system detects a lack of grid power it cuts power to the switch, which prevents the solar panels from sending power to the inverter. This is considered a rapid shutdown, and cuts the backfeed to the grid within 30 seconds of losing grid power.
This also has the property of letting the solar breaker in the breaker panel turn off the whole solar setup. Flipping the breaker for my solar de-energizes my inverter and solar panels, even though the inverter has two sources of power.
The inverter can be setup to run without grid power when there is a battery present.
An automatic transfer switch. Solar Transfer Switch Guide: Why Grid-Tied Systems Fail in Outages
They can switch the power source from the grid to a generator, battery, or with the right inverter, the solar panels directly.
Normally you wouldn’t want to power your house directly from solar anyway because a momentary cloud might suddenly blip the output and cause a brownout or temporary shutdown of your appliances. Motors and some electronics don’t like unstable power like that.
More broadly speaking, the most basic and cheapest home solar setup is a grid tied one where you’re just selling excess power back to the grid, but your solar output is “blended” and synced with the grid’s own output. This is a good thing because the grid is typically much more stable than your small home solar system, and mixing the two gives you higher quality power. The downside is that it’ll stop operating when the grid is down. You CAN add battery backup to such a system but you don’t have to.
There are also off grid systems that can run without an utility connection at all, like for cabins in remote places.
There are also various hybrid and smart systems that combine the pros and cons of various configurations.
It really just depends on your equipment and configuration. For every person who wants solar to ensure uninterrupted power, there are probably a whole bunch more who don’t care, live in a stable utility district, and just want cheaper power bills. I’d guess maybe 70% of residential home solar is grid tied without batteries? But that’s quickly changing with new installs, as batteries get cheaper and better. Eventually they’ll be part of the building codes too. I think California is close (or might’ve already started to) mandate them in certain scenarios.
I think the takeaway here isn’t necessarily “you need X equipment for Y sort of setup”, but that solar systems are semi-custom designs specced to a customer’s particular needs. They’re largely made of commodity parts, but those parts are modular and can be hooked up and rearranged a dozen different ways depending on a project’s specific requirements.
The setup for an urban house would look different from a remote cabin, an apartment complex, a warehouse, a solar power plant, a telecom tower, etc. The actual modules (panels) are the simplest part of the system; it’s all the rest of the control electronics that manage various conversions and backup and switching and such that make them complicated. Plus the bureaucratic government and utility requirements on top of the engineering.
A good local installer should be able to help navigate those intricacies for you and figure out the appropriate technical, legal, regulatory, and financial constraints. But get a few quotes because some of them are outright predatory scammers.
You might look at this:
Basically these are small panels made to hang on your balcony. They are cheap and require no installation; just plug in to a wall socket. They are not yet legal everywhere but they will be. One panel may just enough to power your fridge, but that is not nothing. They are consumer items and will be relatively cheap. My apartment faces about 15 deg east of north, so very little sun but if I were across the hall, I would definitely be looking into them.
Those will be great once legalized and standardized. Until then, it might be a liability and insurance risk if you started using one and it ended up causing a fire or something.
Hopefully soon the state governments will push them through and the UL safety ratings will be commonplace.
They’re already in widespread use in Germany and some other European countries. If they were a fire hazard, I think that would be known by now.
The EU doesn’t have the same laws — consumer or otherwise — that we do. Those things are probably fine 99.99% of the time, but I’m not sure I’d want to be that 0.01% renter who has to deal with the fallout if something were to go wrong… or to try to defend it if a fire investigator or insurance adjuster tries to blame it in the event of some issue, even if it’s not at fault.
People do use them now anyway, it’s just in a legal gray area in most of the states. In a couple years, hopefully it’ll be a non-issue. And solar + batteries will hopefully be even better then.
Keep in mind that a plug-in 1200W system is saving maybe like $20/month in electricity fees. It’s not nothing, but I dunno that it’s worth going out on a limb for.
Ah, interesting, I gather from what you say it depends on the type of electronics involved. I hadn’t considered that someone would just be feeding the grid (along with their house) without blackout protection, but it seems that it is a fairly reasonable (and cheap) option
Interesting point - but then, if you were intending to just run off solar, you probably would not be providing a load on those occasions that’s the full capacity of the panels - after all, it’s less the further you are from noon, and depending on the season, also. I assume the inverter maintains basic 120V no matter the current provided the load is not too high.
Solar direct power (at least for photovoltaic, as opposed to solar thermal) is generally pretty rare, because there aren’t many loads that a typical household would want to run only when the sun is out.
Maybe some variable speed water pumps (like to fill a water tank), air circulation fans, vaccine fridges, water heating, that sort of thing. Basically stuff where you have to move air/water/heat around in large quantities through the course of a day, but not necessarily at a specific time.
Otherwise, a battery adds a LOT more flexibility and consistency. And the grid kinda acts like a giant battery.
Off grid, you’d normally see a battery bank, a generator, and probably also secondary fuel sources for heating and cooking (like propane or a wood stove).
There is a common safety rule that when you disconnect from the grid, the house is safely powered down, and you can touch all the wires.
It’s not universal, lots of places have “backup power”, military installations often have resilient power supplies with safety a non-priority, but the regulatory environment is more complex.
There are a host of thing that need to be set up if you want power out backup capability.
Foremost as described above, the entire building supply must disconnect from the grid. This isn’t cheap as the isolation system must be rated to withstand significant fault current and not weld itself shut in the face of problems. These are large and expensive components. Part of the expense is the testing, certification and liability costs inherent in a device which if it failed could easily kill someone.
The next problem is that basic solar and battery systems are designed to slave themselves to the mains supply. They need to exactly determine their frequency and phase wrt the grid in order to precisely inject power. Without a grid connection they don’t have a reference. In which case they simply stop creating electricity. So a standalone system needs additional control to operate standalone and to be able to reconnect to the grid seamlessly.
This adds more expense and complexity.
An integrated battery and solar system can combine a lot of this, but the grid isolation is never going to be inexpensive.
Then there is the problem that most people can’t afford a system capable of running their entire house from backup power. Now you have the inconvenience and mess of allocating backup power within the house which likely involves modifications to the house circuits and breaker board, maybe even dedicated power runs, and more money.
Most people don’t want the standalone capability enough to actually pay the premium. Very much a nice to have, but how much is the inconvenience of odd power outage worth to you to avoid?
If it is a few thousand dollars to avoid the occasional glitch, most people will keep their money.
I have about 12kW of solar. Peak. In the summer it is fabulous. I can keep the AC running throughout the day and when it is 40C outside it is blissful inside and costs essentially nothing. Winter is not so fabulous. Much less power. Even with heat pump heating, the solar is falling well short of the power required. But it helps. Charging the car is harder as I’m at work in the week and running around on weekends. Perhaps when I retire I’ll charge the car from solar more. Short answer is, solar can help in lots of ways, but very lifestyle and location dependent. For a group of attached dwellings the life style of individual residents could make a big difference to who benefits. Something that could make negotiating difficult.
I used to live in a set of six apartments. Long time ago. However I noticed that solar panels have appeared on the roof of my old apartment. And on the roof of one other. So clearly something was done there. Those appartments had individual metering. Thus it was likely not too hard to make everything work. Separate roof areas as well. Owners do not have individual title, rather a share in a body corporate that owns the land and shared structure with explicit limited title to their appartment. Something I imagine is common elsewhere.
Depends on what you use your computer for and how it is set up.
If you have the company standard Windows 11 set up, for example, it pretty much requires an active internet connection. But you can have local “accounts” that will work fine without the internet, for things that don’t require you to be on-line. Then there are things like cellular phone hotspots and Starlink that can connect you to the internet even if more typical methods are off the table.
The devil is always in the details.
So…
OP, what do you want the power generated by a hypothetical solar set up to do? Is is for lighting on the grounds and hallways?
Is it for emergency purposes? Do you need emergency lighting or the ability to open a garage door even when the grid is down?
Or is this to contribute to the daily electrical usage of the buildings and the units, and reduce bills?
Then there are details of the set up. I’m working with a group of individuals to design our retirement home and we did look into solar. Aside from disparities of day length between summer and winter, the optimal angle for summer is 15° and for winter 70° - trying to find an “all season” setting means diminished power most of the year, and the alternative is some mechanism to adjust the angle on a regular basis. So yes, your latitude matters a lot The closer you are to the equator the less extreme those differences will be.
Then there are nutty people like me - I have a small, foldable panel that will charge something like a phone over several hours. I use it when camping, and in the event of a power outage I can hang it in my bedroom window (faces south, second floor, lots of sun most of the day) and use to charge the phone, a powerbank, run a fan, etc.
Whether or not solar is helpful for apartment buildings depends entirely on the goals of the people using/living in that building.