/ Solar panels and power cut

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KingStapo - on 23 Jan 2014
If I have solar panels on my roof and there's a power cut in the street - do i suffer the power cut with the rest of my neighbours or do my panels keep my appliances going?

Assuming the panels are generating electricity at the time.
ow arm - on 23 Jan 2014
In reply to KingStapo:

not enough
Jordangask - on 23 Jan 2014
In reply to KingStapo:

It depends if you have a feed in tariff... If you get money back from the National Grid for the electricity you generate your solar panels won't work in a power cut as the panels won't be connected to the mains of your house.

Or at least that's the case with mine!
Dave Reeve - on 23 Jan 2014
In reply to KingStapo:

The unit which converts the DC output from the panels into AC (known as the inverter) requires mains power in it's own right. If you have a power cut it won't work regardless of whether you are on the FIT or not.
Denzil - on 23 Jan 2014
In reply to KingStapo:
The grid connected systems rely on the mains supply for them to synchronise and hence feed back into the grid. If there is no mains, the inverter will have nothing to synchronise to and will stay in shut-down (safe) mode. Hence you will have no power from your panels.

Off-grid systems provide power to batteries, and the power inverter then runs from the batteries. These systems do not need to synchronise with the mains and will hence operate completely independently.
alexcollins123 - on 23 Jan 2014
In reply to KingStapo:

If you are connected to the grid and you did still produce power during a power cut, your panels liven up the whole grid in the local area and risk injury to anybody working on the problem assuming its dead (although this should never happen anyway)

It will auto-cut off the power generated.
KingStapo - on 24 Jan 2014
In reply to KingStapo:

suspected as much.

so is there anything i can install that isolates me during a power cut and give me direct electricity from my own cells?
Denzil - on 24 Jan 2014
In reply to KingStapo:

> suspected as much.

> so is there anything i can install that isolates me during a power cut and give me direct electricity from my own cells?

You would need to install a system of the type used in hospitals which have a back up generator. A master isolating switch (power transfer switch) to disconnect from the mains network, then a small generator connected to your house. Once this is providing power to the PV system, the inverter will turn on and provide additional power to the house.
http://www.justgenerators.co.uk/pages/powertransfer.htm
jkarran - on 24 Jan 2014
In reply to KingStapo:

If they feed into the mains via an inverter (the normal set-up) then the inverter AC output will shut down during a power cut. It's a safety feature and legal requirement to protect power line workers.

If it's running circuits that aren't grid connected then those will continue working while ever you have enough sunlight or energy in your batteries.

In short: 'It depends' but most likely you'll also suffer the powercut.
jk
jkarran - on 24 Jan 2014
In reply to KingStapo:

> so is there anything i can install that isolates me during a power cut and give me direct electricity from my own cells?

Yes but what's the point, how often do you get a powercut on a sunny day and you'll be adding layers of cost and complexity to achieve something that will likely never work for you assuming you're in the uk. If you want emergency power during winter or hours of darkness then you can add the cost, bulk and maintenance requirements of a battery and charger system. Personally I'd buy some candles.

jk
jimtitt - on 24 Jan 2014
In reply to Denzil:

> You would need to install a system of the type used in hospitals which have a back up generator. A master isolating switch (power transfer switch) to disconnect from the mains network, then a small generator connected to your house. Once this is providing power to the PV system, the inverter will turn on and provide additional power to the house.


Yup, we have a small generator to activate the inverter for our solar panels which then delivers enough power to activate the generators for the biomass plant to provide enough power to keep the plant alive and running, not so simple this regenerative power stuff!
Denzil - on 24 Jan 2014
In reply to jimtitt:

> Yup, we have a small generator to activate the inverter for our solar panels which then delivers enough power to activate the generators for the biomass plant to provide enough power to keep the plant alive and running, not so simple this regenerative power stuff!

Good to hear of someone who has tried it out! Was thinking of a small mains inverter running off a 12v battery, to activate the PV inverter, to then provide power for the house and keep the battery charged. Don't get power cuts often enough to have tried it yet.
wintertree - on 24 Jan 2014
In reply to KingStapo:
Grid connected feed-in tariff systems almost never work without grid power - partly because they lack any local storage (batteries) to regulate supply and demand, and partly because they can't isolate the AC they output from the grid, so their puny power would either be wiped out by grid demand or electrocute the linesman working to fix the problem.

Getting a solar backed up supply that is normally grid fed is more complicated, and is likely to introduce more failure prone pieces of equipment into the supply, and it still would be a limited supply under grid failure. Key words to search for are "grid tie" and "inverter charger".

SolarCity in the USA are making a big bruhah about their battery backed grid tie systems, and rather excitingly they use lithium ion batteries instead of deep cycle lead acid.

I am more interested in a small capacity solar as an independent back-up source than as a feed in, so I am considering a shed with a panel rated to a couple of hundred watts, a small lead acid battery and an inverter-charger. No grid tie nonsense and a single burried mains cable back to the house to run key devices. Also interested in getting a thermoelectric generator on the backboiler connected as a ~50W charging source to the lead acid. Fun hobby projects to approach with a definite air of caution!
Post edited at 21:55
MikeYouCanClimb - on 24 Jan 2014
> Good to hear of someone who has tried it out! Was thinking of a small mains inverter running off a 12v battery, to activate the PV inverter, to then provide power for the house and keep the battery charged. Don't get power cuts often enough to have tried it yet.


Don't even think of this. This is not just a relatively complex electric task, but you would likely be in breach of UK regulations as well. There are serious safety issues for anyone working on the grid if there is any chance that mains voltage can appear on a line that is presumed dead.

It could be that you have just not worded your reply very well or maybe you have just misunderstand Jim. He can correct me, but his solution reads like' it is completely off line and it is not grid connected.


Denzil - on 24 Jan 2014
In reply to MikeYouCanClimb:

> Don't even think of this. This is not just a relatively complex electric task, but you would likely be in breach of UK regulations as well. There are serious safety issues for anyone working on the grid if there is any chance that mains voltage can appear on a line that is presumed dead.

> It could be that you have just not worded your reply very well or maybe you have just misunderstand Jim. He can correct me, but his solution reads like' it is completely off line and it is not grid connected.

Having already mentioned in previous posts about the necessary isolation from the mains network, I'm well aware of the requirements. If it wasn't isolated I'd be running the entire local network as well as my house!
jimtitt - on 25 Jan 2014
In reply to MikeYouCanClimb:

> Don't even think of this. This is not just a relatively complex electric task, but you would likely be in breach of UK regulations as well. There are serious safety issues for anyone working on the grid if there is any chance that mains voltage can appear on a line that is presumed dead.

> It could be that you have just not worded your reply very well or maybe you have just misunderstand Jim. He can correct me, but his solution reads like' it is completely off line and it is not grid connected.

Your electrician just fits a power transfer switch (and probably an extra earth spike) into the circuit, a domestic one probably costs a couple of hundred quid. They are standard for this application and for boats using shore power or generators. Automatic ones are more expensive.
Ours is a bit bigger as it has to take 400kW and is connected into the German Rail grid!
ads.ukclimbing.com
arch - on 25 Jan 2014
In reply to KingStapo:

Very dangerous for us power workers and can have other effects on people who do not have their own form of home generation. If you really need electricity that badly during a power cut, get a small generator, and feed back into your own house with that. (Making sure you switch your Consumer unit off first) Should be enough to keep the boiler running.

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