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Balcony solar (sort of) in the US- how might I do this? (self.solardiy)

submitted 1 week ago by hittheskids to c/solardiy

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I live in the central US in a south-facing apartment with a TON of sunlight, and I've been wanting to set something up mostly for hobbyist/curiosity reasons. I know actual financial benefits are going to be pretty unlikely, and that's ok.

Balcony solar as I understand it to be an option in Europe is pretty much exactly the sort of thing I want to try, but my understanding is it's not compliant with code in the US. Basically I don't expect to be able to have enough solar capacity to power my whole home, but I'd like to be able to just offset as much as I can when the sun is out. And I think I want a battery in the system so it's not only useful when the sun is out.

I'd love something that works like this:

Prioritize powering the load from the panels (through an inverter, I assume) when available
If the panels alone aren't sufficient, backfill from the battery
If the panels + battery aren't sufficient, backfill from the grid
When the load does not consume all the power from the panels, use excess to charge the battery
Grid is only there as a fallback when the panels and battery aren't sufficient to power the load. Grid does not charge the battery or receive excess from the panels.

If it's not realistic to expect to be able to power the load first from the panels (bypassing the battery), skipping that part and just always powering from the battery and backfilling from the grid maybe would simplify things. I just thought it'd be nice to avoid the inefficency of charging and discharging the battery when the sun is out.

My hope is to have a single solar-backed outlet in my living room off my balcony. During the summer, I'd probably use it to partially offset my little window unit AC. Other parts of the year when I don't run the AC, maybe I'd use it to offset my TV.

Does anything like this exist? My preference would be to get a kit (Ecoflow etc) that includes as much of the functionality as possible and then add on if necessary for any missing functionality, but I would be interested in more piecemeal DIY solutions too of they're reasonably approachable for a beginner. I've watched a lot of "solar at various price points" videos on Youtube and sometimes some of the kits sound like they get pretty close to what I want, but I've never seen this exact combination of functionality discussed.

Thanks.

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[–] [email protected] 5 points 1 week ago (1 children)

I think your best bet is indeed the ecoflow scenario, where you just plug things into that as it's being charged by solar, then switch to grid power after it runs out.

Alternatively, it is viable to cut out batteries entirely. Low tech magazine did a couple good articles on that.

https://solar.lowtechmagazine.com/2023/08/direct-solar-power-off-grid-without-batteries/

https://solar.lowtechmagazine.com/2023/12/how-to-build-a-small-solar-power-system/

[–] hittheskids 1 points 1 week ago (1 children)

Thanks- these links are helpful. A system without a battery sounds more viable than I had considered, but I'm not sure how well it'd work for my intended loads. Maybe I could rethink what I want to run on solar, but I think it's maybe not really an practical option in my setup where the only two loads I have in mind (probably?) require steady power and wouldn't do well with momentary dropouts caused by cloud cover. Good to keep in mind though.

When you say "switch to grid power after it runs out," this is something I was hoping the kit would do automatically for me so I don't have to flip a switch or change plugs from the solar outlet to the grid outlet. If the kit doesn't support that, I wondered if something like this ATS would get me what I want. I'd wonder how exactly it decides to switch back and forth though (it switches to the backup automatically, but will it switch back to primary on its own, and if so, under what conditions? Will it constantly switch back and forth or is there any sort of hysteresis? etc).

[–] [email protected] 1 points 1 week ago* (last edited 1 week ago) (1 children)

I'm not sure if that ATS would do the trick, but perhaps a UPS would? The sysadmin for my instance has the server running off a battery charged by solar, but the UPS automatically switches to grid power once it's empty, and I believe automatically switches back to solar once the sun comes back up.

Do I have that right, @[email protected] ?

[–] [email protected] 2 points 1 week ago

Well it is a bit more complicate than that partially because of grid feed-in and safety regulations.

Basically what you want is a so called Hybrid Inverter. It will allow charging the batteries and also feed into the grid and the reverse all fully automatic. It usually comes with some different modes of what to prioritize (self-supply, full emergency batteries, maximum feed-in for sale etc.) and it will automatically switch over to grid (and back) when the batteries reach a configurable minimum charge level (usually 10-20%).

They also come with an electrical flow meter that is usually installed somewhere near the main grid connection point. This allows feeding into the house grid just so much electricity as the running appliances need and when it measures excess reverse direction flow into the grid it automatically reduces the power it feeds in. This is usually sufficient to comply with regulations that don't allow reverse-flow over the main grid connection meter.

The other thing to know is that to avoid issues with backflow during brown-out situations these grid connected inverters have to shut down during a power-cut. So you can't just continue running stuff from your battery through the regular outlets unless you install a manual switch that completely isolates you from the grid. Some inverters also have an entirely separate emergency power circuit where you could separately connect things like freezers or so, that you don't want to loose power no matter what, but they need to be entirely separate from the rest of the house electric network.

[–] [email protected] 0 points 1 week ago

This is really going to be highly-dependent on the regulations of your apartment. If you ask them they'll probably just say no to everything so you'll have to comb through the docs and see what's allowed. Even then it's likely they'll hit you with a violation regardless, even if technically allowed, and if you don't pay, collection, meaning you'll have to take them to court and prove it doesn't violate any rules. That's a whole lot of risk.

I would avoid any of those "solar generators" for cost reasons. These are expensive components and you want them to be modular so you can replace individual components rather than entire systems.

Will prowse does a "solar milk crate" design here. I would probably try to emulate that but with newer components. I think the "wattcycle" is probably your best bet for battery and Giandel still makes great inverters of various sizes.

Run the panel wires through wherever your window A/C unit is and keep all the components indoors.

A/C is going to be one of the top consumers of energy so you'd probably only get like 1 hour of power/day on a hot day. Better to connect your modem, router, and maybe a small fridge (also a large consumer).