Solar panels and battery - any real world reccomendations?

HungryHippos · 2 Sep 2022 at 10:49

Semple said:
Does anyone have a setup and lives near an area that might be exposed to fast projectiles - not quite bullets . I live next to a cricket field, and we do get on occasion a cricket ball hitting the roof.

I've seen in the US they've been testing panels for golf-ball sized ice fired at high speed - to simulate the hailstones they can get.

I guess I'm just conscious of spending money on panels if one shatters from a cricket ball, and I'm not sure the cricket clubs insurers would pay out for it.

Would worry me if I had cricket balls hitting my roof, panels are effectively sort of tough glass covered.

Not got a side of your roof that doesn't face the wrath of the cricket balls?

SoliD · 2 Sep 2022 at 10:57

How many times has a cricket ball hit your roof in the past? Vaguely remember a post on pistonheads about golf ball smashing a window and they paid for it as they didn't have nets in that particular part so accepted liability.

HungryHippos · 2 Sep 2022 at 11:01

even if they pay though, it's potentially scaffold again and stuff, would be $$$ to replace.

sparkymark75 · 2 Sep 2022 at 11:11

Ron-ski said:
No, but you'll still need a qualified electrician to install/sign it off (Part P), you'll also need to inform the DNO, probably with a G99 application as I presume you already have solar and an AC connected battery can increase export.

Most utilities companies want MCS certificate for export, but if you already have an MCS solar install they are unlikely to know, but there are other ways to get the system signed off as acceptable for paid exports.

Thanks. Yeah I would get a qualified electrician to do it (I have a few as neighbours, but none are MCS).

SBo · 2 Sep 2022 at 11:11

WINTER IS COMING!

I've gone and done it, given up my Octopus Agile Incoming and Outgoing (averaged 28p kwh for export in August!!!) and moved to Octopus Outgoing SEG at 4.1p kwh (boo) and Octopus GO for nightime charging at 7.5p kwh off-peak and 39.84p peak fixed for 12 months.

Relieved to get in before prices go up again. Just flagging to anyone else thinking about this.

I'll set the immersion to charge in those hours on a timer but still can't see a solar diverter at £350-450 ever breaking even.

HungryHippos · 2 Sep 2022 at 11:17

I'm still learning the generation patterns a little.

I knew today would be lower as the weather is shoddy, but so far today it's just draining battery slowly because generation is about 150-300W or so at best, and usage is a bit over 400W baseline.

On GO I will look at setting it to fully charge the battery, I figured I'd try charging to 75% or so instead of 100% thinking generation might keep with load in the day today, but battery is down to about 50% since 04:30 so battery may run out before the end of today when I start adding stuff like cooking and using the PC for gaming/TV later on.

Will be interesting to see if I can limp along with remaining generation today (which looks like it won't be much above another few kwh tops if weather holds) and the last few kwh in the tank.

SoliD · 2 Sep 2022 at 11:22

You'll get good generation later today looking at the solar forecast, but yes all a learning process. Have you got the solar generation api set up in your account?

SBo · 2 Sep 2022 at 11:23

HungryHippos said:
I'm still learning the generation patterns a little.

I knew today would be lower as the weather is shoddy, but so far today it's just draining battery slowly because generation is about 150-300W or so at best, and usage is a bit over 400W baseline.

On GO I will look at setting it to fully charge the battery, I figured I'd try charging to 75% or so instead of 100% thinking generation might keep with load in the day today, but battery is down to about 50% since 04:30 so battery may run out before the end of today when I start adding stuff like cooking and using the PC for gaming/TV later on.

Will be interesting to see if I can limp along with remaining generation today (which looks like it won't be much above another few kwh tops if weather holds) and the last few kwh in the tank.

This is exactly what I need to trial and error now.

Just thinking out loud the price differential between exporting vs buying off-peak (3.4p) is so much smaller than the differential of buying at peak vs off-peak (32.5p) that I think I am going to fully or close to fully charge every night (as well as shifting all consumption at off-peak times to grid) as its such an asymetric bet vs chancing that my solar production will be sufficient on any given day. A good solar day should mean less chaging the following night is how I'm looking at it. But let's see.

HungryHippos · 2 Sep 2022 at 11:24

SoliD said:
You'll get good generation later today looking at the solar forecast, but yes all a learning process. Have you got the solar generation api set up in your account?

The forecast thing? I saw that, not set it up yet.

Tied in Octopus account to the system which seems to be working well.

SBo · 2 Sep 2022 at 11:25

HungryHippos said:
The forecast thing? I saw that, not set it up yet.

Tied in Octopus account to the system which seems to be working well.

Can you share a bit more on this pls? A Lux/Octopus thing?

HungryHippos · 2 Sep 2022 at 11:26

SBo said:
This is exactly what I need to trial and error now.

Just thinking out loud the price differential between exporting vs buying off-peak (3.4p) is so much smaller than the differential of buying at peak vs off-peak (32.5p) that I think I am going to fully or close to fully charge every night (as well as shifting all consumption at off-peak times to grid) as its such an asymetric bet vs chancing that my solar production will be sufficient on any given day. A good solar day should mean less chaging the following night is how I'm looking at it. But let's see.

Assuming like me no payment for SEG at the moment, If we're talking hyper-efficiency then you would charge less overnight if you knew generation would fully top it up in the day.

Looking at the forecast for the next week or so here though, looks fairly miserable.

Common sense would dictate that fully charging now may be a good shout anyway, and the cost to do so isn't that great (8kwh * 7.5 = £0.60).

When spring/summer kicks back in, changing to charging a bit less might be good, I wonder if forecast thing could be smart enough to figure out how much to charge by?

HungryHippos · 2 Sep 2022 at 11:30

SBo said:
Can you share a bit more on this pls? A Lux/Octopus thing?

On the Givenergy app I can add Octopus API info so it can pull data into the inverter side. Need stuff from the Octopus portal (MPAN, Serial Number, Account Number, API key).

Stuff is a little mixed with portal/app and what you can do, but once it's in the site I can add some automation stuff around battery charging. You don't need that to configure scheduled charging though.

SoliD · 2 Sep 2022 at 11:30

@HungryHippos I've never charged my batteries in 2 months. Can't see there being little enough generation even on a miserable day like today at this time of year. I'd Give it time and see how it is at the end of the day.

Mercenary Keyboard Warrior · 2 Sep 2022 at 11:34

Always going to be tricky in the changeable periods isnt it.
Spring/autumn

Worth looking at it from the Minmax point of view.
So if you didnt charge the battery, assuming lowest case normal generation what would the cost of the imported energy be less the saved charge cost, ie the worst case variance.
Then compare to the opposite, say you fully charge the battery then generate enough energy that it would have filled the battery.

Even with no SEG it would appear the risk is far higher by not charging this time of year (topping up in effect). Where as the risk of filling it up and then exporting would seem fairly minor in comparison.

Hope that makes sense

Edit, to clarify that is based on a GO position not normal rates.

HungryHippos · 2 Sep 2022 at 11:40

SoliD said:
@HungryHippos I've never charged my batteries in 2 months. Can't see there being little enough generation even on a miserable day like today at this time of year. I'd Give it time and see how it is at the end of the day.

Last 2 months before this week have been fairly good though, your system is a little bigger than mine (panel wise) and you possibly have a deeper pool of battery storage as well?

When the weather goes poor/rainy, I think you could be dipping into the grid some more maybe, at least based on what I'm seeing today in terms of generation.

Your baseline load will also play into it, i.e. how long your battery would take to rundown if no solar was coming in.

Mercenary Keyboard Warrior said:
Always going to be tricky in the changeable periods isnt it.
Spring/autumn

Worth looking at it from the Minmax point of view.
So if you didnt charge the battery, assuming lowest case normal generation what would the cost of the imported energy be less the saved charge cost, ie the worst case variance.
Then compare to the opposite, say you fully charge the battery then generate enough energy that it would have filled the battery.

Even with no SEG it would appear the risk is far higher by not charging this time of year (topping up in effect). Where as the risk of filling it up and then exporting would seem fairly minor in comparison.

Hope that makes sense

Edit, to clarify that is based on a GO position not normal rates.

Simply based on the forecast for the next week I am seeing, and how I see panels working on (admittedly only a few days) I'd be inclined to agree, filling battery/topping up to 100% at the moment makes sense.

If the weather turned sunny for a week, then yeah maybe you'd get away with not doing that

All a balancing act.

jonneymendoza · 2 Sep 2022 at 11:47

Mercenary Keyboard Warrior said:
Always going to be tricky in the changeable periods isnt it.
Spring/autumn

Worth looking at it from the Minmax point of view.
So if you didnt charge the battery, assuming lowest case normal generation what would the cost of the imported energy be less the saved charge cost, ie the worst case variance.
Then compare to the opposite, say you fully charge the battery then generate enough energy that it would have filled the battery.

Even with no SEG it would appear the risk is far higher by not charging this time of year (topping up in effect). Where as the risk of filling it up and then exporting would seem fairly minor in comparison.

Hope that makes sense

Edit, to clarify that is based on a GO position not normal rates.

At least with a solar panel, you can install a proper ac unit around you're property and during the hot summer days, turn it on and use it for practically free...

Mercenary Keyboard Warrior · 2 Sep 2022 at 11:54

jonneymendoza said:
At least with a solar panel, you can install a proper ac unit around you're property and during the hot summer days, turn it on and use it for practically free...

Kind of

What your really doing in that case is saying I got the decision wrong so to avoid exporting I will use more energy to make it look like the decision was correct after all

I suspect most of the time Hippo (who has AC as well) would be expecting higher elec demand as well as higher generation in hot (assumed sunny) weather

HungryHippos · 2 Sep 2022 at 12:00

I would welcome the solar on a hot sunny day for that reason, though I added AC when prices were a lot better for electric.

By adding solar to the mix I also re-open the usefulness of the AC units.

AC can also heat at around 300-400% efficiency (1 kwh of elec = 3-4kwh worth of heating), I could in theory schedule them to come on for a bit and heat in the winter on the GO pricing for a few hours, I am not sure if it's worth it really as some of that would just dissipate before you woke up :cry:

SoliD · 2 Sep 2022 at 12:10

HungryHippos said:
Last 2 months before this week have been fairly good though, your system is a little bigger than mine (panel wise) and you possibly have a deeper pool of battery storage as well?

When the weather goes poor/rainy, I think you could be dipping into the grid some more maybe, at least based on what I'm seeing today in terms of generation.

Your baseline load will also play into it, i.e. how long your battery would take to rundown if no solar was coming in.

Simply based on the forecast for the next week I am seeing, and how I see panels working on (admittedly only a few days) I'd be inclined to agree, filling battery/topping up to 100% at the moment makes sense.

If the weather turned sunny for a week, then yeah maybe you'd get away with not doing that

All a balancing act.

We've had a couple of challenging few days in a row, but i've hit the 4% battery threshold once, had it down to 5,6,7% a couple of times.slowly going up to 1kwh now after a morning of 500wh.

HungryHippos · 2 Sep 2022 at 12:18

SoliD said:
We've had a couple of challenging few days in a row, but i've hit the 4% battery threshold once, had it down to 5,6,7% a couple of times.slowly going up to 1kwh now after a morning of 500wh.

Did you double up on batteries in the end? I can't remember if you said, I think that would extend things nicely but I didn't want to add two of them when it was a bit more of an edge case.

Guess beyond that your system is a bigger 6kwp compared to my 4.8kwp, and my base load might be a little higher than yours (at 400w and change currently, think you said yours was 250-300?).

With just the 1 battery though and only charging to about 85% yesterday with a slightly higher base load, I'm definitely finding that without topping up last night a few kwh I would be running out on a day like today.