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DIY solar package

Does what it says on the tin
scotview
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Re: DIY solar package

#508171

Postby scotview » June 18th, 2022, 8:18 pm

GrahamPlatt wrote:Re running the electrics for your gas boiler. Wouldn’t it be a lot simpler just to have a small petrol generator as backup?


Yes maybe but theoretically, with a battery, you should be able to capitalise on solar, off peak tariffs and emergency standby. The technology is all there but is becoming frustratingly difficult to implement. Its not rocket science.

My wife would cope with a UPS on auto changeover and maybe a reset button. Filling a messy generator tank, getting it to restart without flooding and all that noise and smelly stuff.

GrahamPlatt
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Re: DIY solar package

#508173

Postby GrahamPlatt » June 18th, 2022, 8:22 pm

scotview wrote:
GrahamPlatt wrote:Re running the electrics for your gas boiler. Wouldn’t it be a lot simpler just to have a small petrol generator as backup?


Yes maybe but theoretically, with a battery, you should be able to capitalise on solar, off peak tariffs and emergency standby. The technology is all there but is becoming frustratingly difficult to implement. Its not rocket science.

My wife would cope with a UPS on auto changeover and maybe a reset button. Filling a messy generator tank, getting it to restart without flooding and all that noise and smelly stuff.


It’s not your wife’s job!
Or, speak to Mike4 and get him to show her the charm of a marine diesel.

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Re: DIY solar package

#508222

Postby 9873210 » June 19th, 2022, 8:39 am

GrahamPlatt wrote:
scotview wrote:
Now, a battery having stored 4kWh will keep a 150 Watt, gas boiler system running for say 5 Days.

Thing is, Electricity can power the electronics and pump, whereas gas has ten or 20 times the thermal density.



Re running the electrics for your gas boiler. Wouldn’t it be a lot simpler just to have a small petrol generator as backup?


It would be simpler* just to have a small gas generator.

Gas burns cleaner than petrol so there is less maintenance and of course no need to store and handle smelly, carcinogenic fuel.

* Simpler than petrol, the merits of gas v. battery are not considered here.

9873210
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Re: DIY solar package

#508223

Postby 9873210 » June 19th, 2022, 8:50 am

Mike4 wrote:I've never really understood how the grid can have the "feed in tariffs" we have here in the UK, I think they must be of little use and a monumental PITA to the grid system designers and managers as you don't have to go far up the grid (often just a few feet!) before the voltage changes to three phase and then steps up. So without thinking too deeply, I'd imagine any solar feed-in happening can actually only power the few houses in the same street on the same phase and voltage.


Transformers work either way. Feed one side they step down, feed the other they step up.

The one phase to three phase will work if roughly a third of the feed-in is on each phase. (Which is essentially the way the load gets balanced across three phases.)

There are technical details that matter*, but the grid can in principle distribute any feed-in power as far as is needed.

* Some managers and engineers regard this as a monumental PITA, others as an interesting challenge they are being paid to solve.

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Re: DIY solar package

#508251

Postby UncleEbenezer » June 19th, 2022, 11:11 am

richlist wrote:Yes there are always exceptions. With any subject you'll find people somewhere who have experienced an unfortunate event......but it's not the norm is it ?

Brief power cuts (under an hour) are pretty common.

Middling power cuts quite rare: last one I recollect was something over five hours in September 2007.

Long power cuts: that'll be Snorvey and Arwen.

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Re: DIY solar package

#508252

Postby Snorvey » June 19th, 2022, 11:15 am

Many thousands were affected by days long power cuts after Arwen (and the subsequent storm - I can't remember it's name) and if the climate bods are to believed, many more events like this are likely to happen.

Saying that, I did recall the National Grid saying that during Arwen the UK was running on 100% renewable energy for the first time ever. Every cloud I guess.

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Re: DIY solar package

#508257

Postby doolally » June 19th, 2022, 11:22 am

Snorvey wrote:Many thousands were affected by days long power cuts after Arwen (and the subsequent storm - I can't remember it's name) and if the climate bods are to believed, many more events like this are likely to happen.

Saying that, I did recall the National Grid saying that during Arwen the UK was running on 100% renewable energy for the first time ever. Every cloud I guess.

So Arwen produced the wind which drove the windmills which produced the electricity which could not reach the consumers because of the damage caused by Arwen.

Hmmm
doolally

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Re: DIY solar package

#508718

Postby gryffron » June 21st, 2022, 8:48 pm

It’s dead easy to use solar+battery to push power back to the grid.
It’s dead easy to use solar+battery to power standalone devices.

It’s extremely difficult to do both. At first thought it sounds easy. But the issue is that your standalone sockets wouldn’t be synchronised to the grid when the grid comes back up. Big Bang! So after an outage there’s no way to re sync the sockets without disconnecting everything and starting it up again from scratch. Which is precisely what you don’t want to do with a standby generator. Sort of defeats the point.

The only way to do it would be to have TWO inverters off the same battery. One synchronised and pushing power to the grid. One independent and pushing power to the standalone sockets. But this is an expensive solution, and difficult to manage, and probably wouldn’t sell enough units to be worth the trouble.

Gryff

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Re: DIY solar package

#508729

Postby 9873210 » June 21st, 2022, 9:48 pm

gryffron wrote:It’s dead easy to use solar+battery to push power back to the grid.
It’s dead easy to use solar+battery to power standalone devices.

It’s extremely difficult to do both. At first thought it sounds easy. But the issue is that your standalone sockets wouldn’t be synchronised to the grid when the grid comes back up. Big Bang! So after an outage there’s no way to re sync the sockets without disconnecting everything and starting it up again from scratch. Which is precisely what you don’t want to do with a standby generator. Sort of defeats the point.

The only way to do it would be to have TWO inverters off the same battery. One synchronised and pushing power to the grid. One independent and pushing power to the standalone sockets. But this is an expensive solution, and difficult to manage, and probably wouldn’t sell enough units to be worth the trouble.

Gryff

Resynchronization is not that hard. Once the grid comes back you monitor the grid frequency and run your island at 49Hz-51Hz for a minute or so until it synchs with the grid. Then you close the isolator to reconnect to the grid. In most systems this is all software. At most you might need a minor hardware change such as adding a monitor on the grid side of the isolator.

Also you are seriously misreading what a standby generator is for in a domestic context. Unless you're running a data center outages of a few seconds to a minute are fine*, the generator is to prevent outages of hours or days.

* At worst you have to reset a bunch of cheap clocks. If this is a problem buy better clocks.

jaizan
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Re: DIY solar package

#511346

Postby jaizan » July 2nd, 2022, 1:22 pm

richlist wrote:I'm surprised that this thread has migrated to discussing power cuts. In the past 20 years I don't believe we have had more than 3 short power cuts in that time.


In those last 20 years, we have been closing our coal plants and closing our nuclear plants.

We now rely more on wind and imported gas, however, the problems with this are obvious.
The wind output frequently drops to about 1% of installed capacity.
Russia is a major gas supplier to Europe.

So the risk of prolonged power cuts is increasing.

We don't even seem to do sensible things like dispersing the wind farms over a wider area -they seem to be keen on building more of them close together in the North Sea, rather than trying to disperse them, with more off the west coast and so on.

Also, global coal use for electricity generation was at record levels last year. Whilst we are pursuing an expensive energy policy that puts our manufacturers out of business and puts bills up for consumer, it's pretty pointless if countries like India and China keep building more coal fired electricity generating plants.

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Re: DIY solar package

#511369

Postby DrFfybes » July 2nd, 2022, 2:53 pm

gryffron wrote:It’s dead easy to use solar+battery to push power back to the grid.
It’s dead easy to use solar+battery to power standalone devices.

Gryff


I have been looking more and more at going totally off grid. It started with the shed, and is moving toawrds the whole house. We use about 12kWh per day, perhaps slightly more in winter as the fish tank needs more heating. For circa £15k (plus installation!) one can get a 10kW solar system with 40kWh effective storage (actually 80kWh storage, but apparently only half is available, but still enough for 3 days) assuming the 10kW system can provide 15kWh/day in winter in the midlands.

At current capped prices, our annual 4100kWh costs £1150, plus £164 standing charge, so £1300/year, which is only going to go up in the near future (long term who knows). It is teetering on the edge of being viable. In summer we would use the surplus to heat the water, so reducing the gas bill slightly (current gas use is about 8kWh/day, which is hot water and the hob for 15 min or so for tea) so another £15/month for much of the year.

Of course going off-grid completely removes the option of selling surplus back in summer, so there is some maths to be done.

Paul.

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Re: DIY solar package

#511394

Postby ReformedCharacter » July 2nd, 2022, 6:08 pm

DrFfybes wrote:
gryffron wrote:It’s dead easy to use solar+battery to push power back to the grid.
It’s dead easy to use solar+battery to power standalone devices.

Gryff


I have been looking more and more at going totally off grid. It started with the shed, and is moving toawrds the whole house. We use about 12kWh per day, perhaps slightly more in winter as the fish tank needs more heating. For circa £15k (plus installation!) one can get a 10kW solar system with 40kWh effective storage (actually 80kWh storage, but apparently only half is available, but still enough for 3 days) assuming the 10kW system can provide 15kWh/day in winter in the midlands.

At current capped prices, our annual 4100kWh costs £1150, plus £164 standing charge, so £1300/year, which is only going to go up in the near future (long term who knows). It is teetering on the edge of being viable. In summer we would use the surplus to heat the water, so reducing the gas bill slightly (current gas use is about 8kWh/day, which is hot water and the hob for 15 min or so for tea) so another £15/month for much of the year.

Of course going off-grid completely removes the option of selling surplus back in summer, so there is some maths to be done.

Paul.

Thanks, interesting, I've been thinking about going off-grid too and planning to get our house rewired at some point. In theory I'd like to have solar + battery but with the option to switch to mains as a backup. The particular area we live in does not do well for sunshine during the Winter months, so battery only looks unfeasible but if a mains backup could be added at reasonable cost, it might be worth looking into a bit more.

RC


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