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Solar in a blackout

  • 03-10-2021 10:10pm
    Registered Users Posts: 861 ✭✭✭

    In theory those of us with solar could have some power in a blackout - but the current installs (with grants) all have an auto-cut-off when the grid is out that disconnects the solar panels from the inverter.

    Some inverters (e.g. solis) have a secondary output that can run when the grid is out, but as the panels are disconnected this would only run until the battery is drained.

    So in a blackout, with the sun beating down, we're going to be SOL (pardon the pun).

    I was thinking of installing a grid isolation switch that would allow me to keep running - by basically shorting the secondary output to the primary output when the grid isolation switch is thrown (i.e. double pole switch - one side grid, the other side secondary output). Would this work, and allow the solar to keep running? If not, is there an alternative ?



  • Moderators, Home & Garden Moderators Posts: 4,922 Mod ✭✭✭✭graememk

    You can get a generator switch put in before your consumer unit - or a sub board with a few essential circuits.

    On the sub board you could have some plugs, lights enabled & a supply to the fireman's switch.

    Reason I'm suggesting a sub board, is that in chatting to my installer the inverters don't like/your not meant to feed the inverter it's own supply as if it's the grid.

  • Registered Users Posts: 2,265 ✭✭✭bullit_dodger

    I'm not an electrician, but it sounds like that probably wouldn't (shouldn't?) work. The whole thing about the inverter is that it pumps out a higher voltage than what it detects as the grid. So it would use it's voltage over the grids. So if the grid was reading 220v, the inverter would do 225v or something. If you feed it it's own supply, wouldn't that just create a circular feedback loop? Raising the voltage until it goes out of tolerance? (230v +/- 10%) I guess you could lower it (the voltage), but really, there are probably better solutions. Dedicated UPS boxes and the like.

    However, using your backup 3 pin outlet on the inverter, why not just run a 10m extension cord off it and plug in the telly or whatever you want into it. If there was a blackout, it probably would only be for 2-3 hrs max, no?

  • Registered Users Posts: 78,081 ✭✭✭✭Victor

    There are two main blackout scenarios at the moment.

    1. A localised blackout due to network damage. This is most likely in stormy weather, nearby construction works or network maintenance. Wind, but not so much solar.
    2. Insufficient supply in the network. This is most likely mid-winter, in cold weather, between the hours of 5-8pm. This would mean no wind and no solar.

    Managing you demand generally (insulation, heat storage, batteries, deciding what usage is important) and at such times (batteries, deciding what usage is important) is probably the most important thing you can do.

  • Registered Users Posts: 861 ✭✭✭tails_naf

    Good to see it can work, and good idea for turning off the primary supply to the inverter while the secondary is driving the full fuse board. So it sounds like we need to

    1) isolate the grid from main fuse board

    2) isolate the inverter primary output from the fuse board

    3) switch the secondary output to drive the fuse board. This allows it run all loads, up to the power limit of the secondary output which is about 3kw

    One item, I'd you don't have a fireman switch, do you rely on your inverter primary output shutting off in the event of an outage and you are not at home to switch off the mains?

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  • Registered Users Posts: 3,094 ✭✭✭irishchris

    Yes all approved inverters in Ireland from what I'm aware have anti islanding so designed to shut down in event of grid outage

  • Registered Users Posts: 861 ✭✭✭tails_naf

    Shame the grant requires the fireman switch so, seems unecessary, and will lockout the system if the battery goes low overnight it won't have enough juice to keep it open, so will have to remove or isolate that also.

  • Registered Users Posts: 3,094 ✭✭✭irishchris

    I suppose it's there to isolate in case of house fire the panels but in my case is in ground mount outside and easily reachable. But agree that surely one of the most important parts of having solar is that you will have continuous power as long as the weather plays ball. But to see a sunny day outside and house with no power during a grid outage is just wrong imo

  • Moderators, Society & Culture Moderators Posts: 16,055 Mod ✭✭✭✭Manic Moran

    We've been chewing on the same problem. A battery for the solar system (eg a Tesla Powerwall or the like) makes zero financial sense for us, its only utility would be for power cuts, so we don't have one.

    It narrowed down to two options. One was an external generator (running on natural gas or propane), which is a third the cost of system battery. Again, though, long power cuts are rare enough I'm not sure it's worth the cash.

    What I ended up doing was concluding that we didn't need to run the whole house. All we needed to do was keep the refrigerators cold, the 'phones charged, the fish tank at the right temperature, and have the coffee machine functional. To do it, I bought a camping battery. In my case, the 1.2kWh Ecoflow Delta, though there are a couple of other companies such as Jackery. It'll run the necessities of the house for most of the day. Plus, it's portable, so if I ever am out and about in the wild and need power, I'm sorted. I also need to go buy the panels for the thing, so that I can get a charge into it for possible multi-day cuts, not that they are common.

  • Registered Users Posts: 184 ✭✭harderthanf

    I grabbed two 100aHr (2.4 kwhr) lesiuire batteries (400 cycles AGM) for around 130euro each, a 1000W pure sine wave inverter, a mppt charge controller and 300W panel. This easily keeps the house going with broadband , access point, lights and tablets for longer than any outage we've had.

    All this was around 550 euro and should do me for most of the rest of my life. 🤣

    I've a fire man on my ground array and can't think of an easy way around it either!

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  • Registered Users Posts: 17,211 ✭✭✭✭VinLieger

    Just stumbled across this thread as ive begun to look into solar and storage as im guessing have many with the potential blackouts we may have going forward during winters. But this sounds like it makes the whole thing a bit pointless if during a blackout your system also automatically stops even if you have power stored? What is the reason for this and is it likely to change?

  • Registered Users Posts: 2,265 ✭✭✭bullit_dodger

    The reason (briefly) is that the wiring is a two way circuit. When you house needs power you take it from the grid, when you have excess you can give it out.

    Problem with a powercut/blackout, is that your inverter doesn't know if the grid is down for a deliberate outage, or the electricity cable down the road knocked down by a tree. So for the tree issue, ESB "power down" that area so the electricians can go work out and safely work on the fault. If in the meantime, you are quiet happily chucking 220v out into the wild, while ESB have turned off their side, your about to give some poor electrician a bad day.

    So when inverters detect no grid voltage, for safety reasons they will go inoperative. Now in theory you could safely set one up that it can work in an outage, but it requires creating separate isolated circuits in your house. Most people, unless you have some skill in the area should avoid. I know enough, to know enough that it's not worth it for me.

  • Moderators, Society & Culture Moderators Posts: 16,055 Mod ✭✭✭✭Manic Moran

    In fairness, VinLieger's specifically asking about 'if he has power stored'.

    I don't know if there's any specific regulation on the matter in Ireland, but around here, systems with storage systems will switch to drawing from the storage system during an outage, though systems without storage (mine included) will cease solar production for the exact reasons you give. I don't know if the panels will recharge the storage during an outage, however (i.e. if, for safety, they can draw from the battery, but not produce for anything).

    "All this was around 550 euro and should do me for most of the rest of my life. 🤣"

    How the hell did you find 4.8kWh of battery for EUR550?

  • Registered Users Posts: 184 ✭✭harderthanf

  • Registered Users Posts: 1,395 ✭✭✭sozbox

    Where did you buy yours if you don’t mind me asking?

  • Moderators, Society & Culture Moderators Posts: 16,055 Mod ✭✭✭✭Manic Moran

    Still a good deal. Amazon's showing the Ecoflow at $1,100 right now, that's just 1.2.

    Soz, at Amazon.

  • Moderators, Recreation & Hobbies Moderators, Science, Health & Environment Moderators, Technology & Internet Moderators Posts: 89,278 Mod ✭✭✭✭Capt'n Midnight

    Germany had a partial eclipse a few years ago where 15GW of solar dropped off the grid for a few minutes and it was managed.

    Have a plan B. Grid outages aren't normally long and your phone has a light build in. Work out what else you need over short time scales. My parents got a bottled gas cooker as a backup for cooking, could have been used for boiling water if needed.

    Longer time scales would require you to have more backup. Go read a book.

  • Registered Users Posts: 184 ✭✭harderthanf

    I am not familiar with the Ecoflow. I just took a look and the battery chemistry is different to that battery I have. As it's lithium if will have a better depth of discharge, closer to 0% (but I'm not getting into that argument !), where as most LA batteries shouldn't really drop below 50%. Also, the weight difference is huge. Still, for what I need the AGM's are perfect.

    I see the Ecoflow is just 18650 cells. If you were anyway handy you could make a pack with new (or used) 18650's, a BMS, inverter and the sockets/ports for an awful lot less that what they're advertised as. The do look handy though!

  • Registered Users Posts: 184 ✭✭harderthanf

    Coincidently we just had an unscheduled power cut here from 10am until 14:00 - happy I had that battery and kit in place. Broadband, wireless, laptops all working. Hope this isn't the start of things to come this winter

  • Registered Users Posts: 12 Nutzfahrzeuge

    Sorry for asking a dumb question - but how do you get an Ecoflow to power your house during a black out? Presume you cant just plug it into a socket and it works in "reverse" ?

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  • Registered Users Posts: 184 ✭✭harderthanf

    Technically that will work, but do not do it!

    I have the battery pack as a stand-alone unit. When the power goes I roll in the pack and just unplug the devices I need (from the mains) and plug them into the inverter sockets on the pack. I have a few low power (~7W) lamps that I can plug in around the place too. So bare minimum I can light the house and keep the kids occupied with phone/Switch/YouTube etc. while herself can gander at Netflix etc on the tablet. It's not a full drop in replacement but it definitely helps

  • Registered Users Posts: 1,867 ✭✭✭garo

    LifePO4 is safer than 18650. Also cheaper. The set about was 1275 last week. 10.24kWh.

  • Registered Users Posts: 10,230 ✭✭✭✭the_amazing_raisin

    It depends on the inverter, but some of them have a system called anti islanding built in. Or it can be installed separately

    Basically if it detects any unusual behaviour from the grid, it'll isolate the house from the grid. So the solar and batteries (or generator) can continue operating

    It's very similar in function to an automated transfer switch you'd have with a backup generator

    Here's an example of one system

    "The internet never fails to misremember" - Sebastian Ruiz, aka Frost (Escapist magazine)

  • Registered Users Posts: 2,265 ✭✭✭bullit_dodger

    Anyone got any recommendations for some UPS boxes? Thinking of maybe ~1.0 Kwhr or there abouts for the telly.


  • Registered Users Posts: 3,300 ✭✭✭randombar

    So I've a back up cable coming back into my main fuse board.

    My understanding is that, that is essentially wired into the fuse board and I can switch over to that when the power goes, but I would have to disable a few CBs if I don't want that power going to every device / plug ?

  • Moderators, Society & Culture Moderators Posts: 16,055 Mod ✭✭✭✭Manic Moran


    Part of the reason I picked the Ecoflow unit which I did is that it has a 'draw limit' sufficiently high that it will run some more power-hungry items at the same time. It's not just a matter of how many kWh the battery stores, but whether it can provide that power quickly enough to meet devices which use electricity more rapidly. You can imagine that charging your iPhone will take far less of a draw than running my American-sized fridge-freezer. Most camping batteries will have multiple power sockets, but are not expected to run major appliances, so if I want to run, say, my main fridge-freezer, the deep freezer, the fish tank and charge my 'phone all at once, with the high draw limit I can do it with the unit I have (Using 50' extension cables, granted), although, of course, for less time than running just the one item.

    Plus, of course, I can use it for other things. It's in the garage right now, powering my tyre inflator.

    Post edited by Manic Moran on

  • Registered Users Posts: 861 ✭✭✭tails_naf

    If you allow the backup to power your main fuse board, you have to cut off the supply to the grid, that's the crux. That'd why I'd like a single switch that connects in the backup supply while at the same time disconnecting the grid (and inverter primary output). This would allow the fuse board to supply the house but also make it safe to someone working on the grid. If there was a switch like a double pole double throw, capable of handling grid current it would be ideal.

  • Registered Users Posts: 1,484 ✭✭✭MAULBROOK

    If you have a Solis inverter their is a backup plug on it, so i just put a single socket on it and during a power failure I just run the extension lead out to it.

    Now depending your battery output that is. I'm lucky our setup can output 3.5kw. no problem for coffee makers or a kettle. I could easily run the TV router and sat box for a number of hours, god forbid we have to acutely talk to other members of your family.

    Knowing your setup is key to this, you need to understand what it can or cant do.

    Many people with solar and a battery have this in place without knowing it. TBF you paid a lot of money for it, why would you not try and learn what it CAN do for you.

    NOTE, not all setups are the same and some don't have this facility.

  • Registered Users Posts: 184 ✭✭harderthanf

    Yeah, that is a good point. That really comes down to the inverter though and for small (relative) current an SLA battery is comparable to any other chemistry regarding max C-rating and/or in rush amp limits.

    The Ecoflow's are nice bits of kit but extremely overpriced for what you actually get. However, for most people, the price is easily offset against the hassle of building a pack yourself!

    edit: just looking over the Ecoflow spec and although it doesn't say it, it must be using a pure sine wave inverter as it mentions be able to use devices with motors etc. This would bring a "self-build" pack price up a little bit.

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  • Registered Users Posts: 1,875 ✭✭✭randomname2005

    Any links/brand names and models for the components for us newbies to this game?