Circular reasoning (Rolfe's solar energy system)

It goes like this.
  1. I really should get a home charger.
  2. If I get a home charger, I need a variable electricity tariff.
  3. A variable electricity tariff will make my daytime usage more expensive.
  4. The answer is to get a home battery and fill it with cheap electricity overnight.
  5. Look at your roof, if you have a home battery it would be criminal not to install solar.
  6. That will be £13,700 altogether.
  7. But I could buy a hell of a lot of electricity for that. Um.
  8. But I really should get a home charger.
How do you get out of this loop?
Get a home charger , switch to octopus agile , get the home battery , add solar if you like . But get all the above that talk to home assistant so you can charge at the cheapest rates whenever they are
 
I thought you got a 5kw inverter, though.

In which case 5kw (plus any change - sounds like you can get an extra 0.3) is all that it can output.

Good idea to test it out with the car but my guess would be that it can put the power in the battery because the battery is also DC. However, it cannot convert to AC more than 5kw.

This isn't an issue for us because we are East-West. The two are never in perfect sun at the same time.

5kw is plenty of output, but if my theory is right it sounds like you want to be filling your battery only/primarily during those peak hours when you get over 5kw from the panels.

So use as much as energy as possible during the morning when you are getting under 5kw (fill the car, hot water, export more during that time if possible). Then fill up the battery during the peak of the day.

You could play with it on a sunny day when you've got time to focus. Set to export a set amount (say, 2kw) in the morning, so that the battery doesn't get quite so full. Then see if you get higher solar generation for longer during the sunniest hours.

Yes, I got the 5kW inverter, but there is this issue with the G99. I have no idea what's going on really, but trial and error will get me there. At the moment I don't even know how to "set up" anything. The system is what it is, and I'm just letting it do its thing and trying to understand it.
 
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I think it's clipping because of the lack of a G99. Probably. Possibly.
Though you would think that if it was G99 related you'd be limited to 3.68kW until you got the G99 at which time it would rise to 5kW.

Which is what makes me think the clipping is just the inverter getting to its maximum AC conversion capacity. Yet it can take more than this from the solar as long as it stays as DC and goes straight into the battery.

Does that theory make sense?
 
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Get a home charger , switch to octopus agile , get the home battery , add solar if you like . But get all the above that talk to home assistant so you can charge at the cheapest rates whenever they are

Well, I've done the charger, the home battery and the solar, and I'd switch to Octopus Agile if they would only get their act together and let me. Home assistant is probably a bridge too far for me right now.

Though you would think that if it was G99 related you'd be limited to 3.68kw until you got the G99 at which time it would rise to 5kw.

Which is what makes me think the clipping is just the inverter getting to its maximum AC conversion capacity. Yet it can take more than this from the solar as long as it stays as DC and goes straight into the battery.

Does that theory make sense?

Yes, it does make sense. I'll get there eventually.

Actually, if the 5.3 kW is the real limit of the inverter, that would make sense of the installer's comment that he hadn't messed with the system at all and we were basically on a "don't ask don't tell" footing until the G99 was official.

Indeed, I think I see what's going on. The base load of the house is about 300-odd watts. So if it's the case that the panels are able to import the current load (house base load, battery charging) plus 5 kW, that might figure. But then, why aren't they importing more when the house load goes up due to an appliance running. Dunno.
 
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Yes, I got the 5kw inverter, but there is this issue with the G99. I have no idea what's going on really, but trial and error will get me there. At the moment I don't even know how to "set up" anything. The system is what it is, and I'm just letting it do its thing and trying to understand it.
On the App under system mode you could set the discharge rate to scheduled and set up full export at 2kW from, say 9am until 11am.

It is a bit of a faff to be updating the settings regularly - I've only seen it happen as Octopus have access to our account and constantly set it up to charge/discharge the battery. Intelligent Octopus flux.

People who have set up home assistant can no doubt do all sorts of clever things with their export/battery settings.
 
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I'll work it out. There's not much point in exporting any more than the system is doing of its own accord until the G99 is through.
Yes until your export tariff is set up you are just giving away free energy to Octopus.

But your neighbours getting free solar from you is better than burning gas to power them.
 
Absolutely! (Well, my neighbours are getting solar they're paying Octopus for, which I gave Octopus for free, but there you go. This is day three.)
 
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The battery and the inverter are GivEnergy. I think it's clipping because of the lack of a G99. Probably. Possibly.
The inverter wont know that there isnt a G99 in place :ROFLMAO::ROFLMAO:

It looks likely that your installer has throttled it's performance, what rating inverter is it?

Is that taking your standing charge into account?
Yes, it's been a good month, doing my evening exports has made a huge difference. The last for quite a few days this month i've been exporting above 50 kWh via the solar and batteries which gets an export payment of £7.50 plus per day. Charging the batteries off peak only incurrs £1.65 cost or thereabouts, it seems almost too good to be true. Then it will rain and it all goes out of the window :)

I'm pretty sure that the solar would not clip if I plugged the car in. However, as the car is currently at 100% and has been since Friday, this experiment is not possible.
Take for a quick thrash down the road and back, then put it on charge, go on, you know you want to hehe.

I saw 5.76 kw this morning, momentarily, just as the sun broke through the complete cloud cover we had from daybreak to 11.15. (I saw similar yesterday, and on Friday there was a momentary peak at 7.37 kw during a blink of bright sunshine.) At that time the battery was still charging. But by the time the sun really got going, about12.45 the battery was full and it was clipping again.

View attachment 26679
Hoiw does it respong if you switch some loads on, oven / hob / tumble dryer etc?

I see that the system started getting the hot water going as soon as the sun broke through, prioritising that over the battery charging. Then after that was done it was export all the way (boo, hiss). Not quite sure why there's that little battery blip after each water-heating boost, looks as if each time the immersion heater has used a little bit of the battery.
Do you know if your system is controlled by a generation meter oir a CT (Current Transformer)? If it's a generation meter, they can be slower to respond to step changes in load, CT's respond quicker but are poor at low current levels (import or export).

It didn't do that yesterday. Maybe because the sunshine was a bit intermittent at the time?
Maybe your hot water demand was different yesterday too?

But then, mid-afternoon, I had two thoughts. One was that I'd spilled something on the clean jeans I was wearing yesterday evening, that I wanted to travel in on Tuesday, and I wanted to wash them. So I chucked them and a few other items in the washing machine.
That will make a difference

The other was vanity. Yesterday evening on a Zoom call I didn't like the colour of my hair. This afternoon I saw myself in the mirror and REALLY didn't like it. Again, I wanted it right for going away. So I decided to colour it, which involves having a shower. So after I'd started the washing machine I did that. I'm now dressed and decent again, but the washing machine hasn't quite finished. (Get on with it, I want these things on the line in the sun.) Oddly enough though, all that usage seems to have been mopped up and the system is back to exporting.
Do I detect some smugness there? it's amazing. I look at my house in winter time, all lit up, heatpumps running, oven and hob on and then consider all of the energy is coming from my little shed with my battery in it, it just seems unreal.

Hopefully I'll at least have the cheap night-time tariff by the time I get back from my trip to England. I don't know why they're being so obstructive about the G99. Still, I'm better off than before I had the system, at least if you don't count the cost of the system, which is where we came in.
You must have a great feeling of satisfaction with this project, it still staggers me how we allow new builds without having some basic solar installation compulsorily .
 
You say the inverter doesn't know about the lack of a G99, but I was wondering if my installer was supposed to tell it.

Although I see a blip this afternoon when it wasn't clipping, that coincided with a blip where the battery was recharging after the immersion heater had been on. Looking at yesterday, where it's clearer, there's no sign that the clipping was discontinued while the actual immersion heater was running.

I have to take the car out this evening, but only for six miles to choir practice and back. Tomorrow is forecast to be dull right through to early evening so there may not be much scope for experimentation. It can wait till later. I need to replace that charge as I have to leave on Tuesday morning with 100%, but since it's only going to be about 2 kWh it can come from anywhere, any time. I'll see if there's any export happening tomorrow and probably charge the car then, if it does.
 
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You say the inverter doesn't know about the lack of a G99, but I was wondering if my installer was supposed to tell it.

Although I see a blip this afternoon when it wasn't clipping, that coincided with a blip where the battery was recharging after the immersion heater had been on. Looking at yesterday, where it's clearer, there's no sign that the clipping was discontinued while the actual immersion heater was running.

I have to take the car out this evening, but only for six miles to choir practice and back. Tomorrow is forecast to be dull right through to early evening so there may not be much scope for experimentation. It can wait till later. I need to replace that charge as I have to leave on Tuesday morning with 100%, but since it's only going to be about 2 kwh it can come from anywhere, any time. I'll see if there's any export happening tomorrow and probably charge the car then, if it does.

The immersion is running off spare AC power, so it won't reduce the scope for pre-transformation DC clipping (assuming my earlier AC max theory is correct).

You've got loads of solar anyway this time of year, but the missing generation may be happening because your battery can't take any more (captain).

I see what you mean about not getting paid for the export so you don't get any benefit. However, but if you can export more earlier on in the morning (thus battery isn't full) then during the peak times the battery can absorb more of this peak sunshine. It would mean you were exporting more in total, though you don't get any personal financial benefit from that (for now).

Or you could buy another big battery for the hallibut ;)
 
I was chatting to the husband of a friend of mine after church this morning and he was telling me how their system works. He has a 5 kWh battery. When I said mine was 9.5 kWh, he exclaimed "that's a monster!" I remarked that I had a 51 kWh battery in the car, just to put it all into perspective.

It'll all be fine when I get the export tariff. And it's a bit irrational to be irritated by the present situation when for the past 17 years these sunbeams have been falling on to that roof and doing me no good whatsoever.

I only need to add 2 kWh (and balance) to get the car back to 100% for the big adventure on Tuesday. I'm not quite sure when and how to do that, but frankly I could probably take it out of the battery at midnight and still not go into the red, so it's all cool.
 
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I was chatting to the husband of a friend of mine after church this morning and he was telling me how their system works. He has a 5 kwh battery. When I said mine was 9.5 kwh, he exclaimed "that's a monster!" I remarked that I had a 51 kwh battery in the car, just to put it all into perspective.

It'll all be fine when I get the export tariff. And it's a bit irrational to be irritated by the present situation when for the past 17 years these sunbeams have been falling on to that roof and doing me no good whatsoever.

I only need to add 2 kwh (and balance) to get the car back to 100% for the big adventure on Tuesday. I'm not quite sure when and how to do that, but frankly I could probably take it out of the battery at midnight and still not go into the red, so it's all cool.
When you get the export tariff you'll probably be emptying the battery every day from 4pm-7pm. Octopus do that to ours. Then top it up a little bit at 7pm before leaving it at 20% overnight ready to get filled (slowly) from solar the next day.

That's the Summer mode anyway - maximize export during the evening peak.

We've made over £6 today! (but we were away this weekend and got back this evening).
 
I have a lot to learn. I'm thinking right now that I might turn on a fan heater rather than fire up the central heating for a couple of hours. I think the battery can afford it. But then it's going to be overcast tomorrow, and I don't know how overcast it can be before the battery has trouble recharging. One way to find out...
 
I have a lot to learn. I'm thinking right now that I might turn on a fan heater rather than fire up the central heating for a couple of hours. I think the battery can afford it. But then it's going to be overcast tomorrow, and I don't know how overcast it can be before the battery has trouble recharging. One way to find out...
For us in the Summer a very overcast day usually gets around 10kWh, a sunny one 30+kWh.
In the winter 10kWh would be a great day, 4kWh the norm.
 
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I have a lot to learn. I'm thinking right now that I might turn on a fan heater rather than fire up the central heating for a couple of hours. I think the battery can afford it. But then it's going to be overcast tomorrow, and I don't know how overcast it can be before the battery has trouble recharging. One way to find out...
... at the end of each day as long as you have a few kWh in your battery, then you are at an optimal level - you are only going to see you running out this in Dec / Jan
 
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When you get the export tariff you'll probably be emptying the battery every day from 4pm-7pm. Octopus do that to ours. Then top it up a little bit at 7pm before leaving it at 20% overnight ready to get filled (slowly) from solar the next day.
If youre on IOG thats not the best way to operate, FIT not being available nowadays.

That's the Summer mode anyway - maximize export during the evening peak.
Feed in tariff is flat rate 15p so it's easy to calculate and feed in later ready for import from 23:30

We've made over £6 today! (but we were away this weekend and got back this evening).
This month my daily bill is around 10p this includes running 2 x EV, Air Conditioning, washer, tumble dryer, immersion heater etc. My export income is over £7.50.

Running SEG is really good for the grid and you exporting at peak times very helpful.

I have a lot to learn. I'm thinking right now that I might turn on a fan heater rather than fire up the central heating for a couple of hours. I think the battery can afford it. But then it's going to be overcast tomorrow, and I don't know how overcast it can be before the battery has trouble recharging. One way to find out...
Plan in the future to put Air Conditioning in busy rooms, it works really well with batteries being so efficient.
 
... at the end of each day as long as you have a few kWh in your battery, then you are at an optimal level - you are only going to see you running out this in Dec / Jan

What I did worked OK. The battery had already begun its overnight discharge by 10 pm, and was on 92%. I ran the fan heater for a couple of hours while I watched a film, and by the time I went to bed at midnight the battery was down to 50%. So more than 40% of the battery was used by the fan heater just in those two hours.

The battery was down to 28% by about 6.30 am, when the solar input had grown to the point where it could start recharging. So it was fine for a couple of hours on an evening when the sun was going to come up pretty early, but there clearly isn't scope to do much more than that.

For us in the Summer a very overcast day usually gets around 10kWh, a sunny one 30+kWh.
In the winter 10kWh would be a great day, 4kWh the norm.

Today is fairly overcast although I think there might have been the odd break in the cloud, and I've already got 8.1 kWh before one o'clock. I don't see any way to look back and see how much I got on each day, but the system has been live since Thursday and the total generation has been 136.5 kWh. That sounds about the same as what you're saying - these days were fairly sunny, Saturday was very sunny.

... at the end of each day as long as you have a few kWh in your battery, then you are at an optimal level - you are only going to see you running out this in Dec / Jan

Yes, but running a fan heater in the evening rather than fire up the central heating is a strictly small-scale operation, only good for two or at the most three hours.

If youre on IOG thats not the best way to operate, FIT not being available nowadays.

Feed in tariff is flat rate 15p so it's easy to calculate and feed in later ready for import from 23:30

This month my daily bill is around 10p this includes running 2 x EV, Air Conditioning, washer, tumble dryer, immersion heater etc. My export income is over £7.50.

Running SEG is really good for the grid and you exporting at peak times very helpful.

Plan in the future to put Air Conditioning in busy rooms, it works really well with batteries being so efficient.

I have managed to shift to IOG this morning. Current situation is car fully charged and battery on 71%. Hot water hasn't done a thing since yesterday afternoon and isn't particularly hot, but it's OK and I'll wait to see what happens.

Panels had been hovering between 1.3 and 2 kw most of the time, with only a small amount of export about 9.30 when there must have been a blink of sun. However it seems to be brightening up now, the panels just shot up to 4.3 kw, and again I'm seeing a small amount of export, so maybe the Eddi will do its thing some time this afternoon.

I had to charge the car this morning in order to get IOG initiated. It only needed about 2 kwh to be full so that was fine. I had intended to do it on the granny charger to ensure the charge came from the battery, but on the Zappi it still mostly came from the battery with only 0.3 kwh of grid import when the car's demand momentarily exceeded the battery's discharge rate. This was fine, but it makes me think I am indeed in danger of the problem mentioned earlier of the Zappi sucking everything out of the house battery. I did mention it to my supplier but I wasn't sure what I was talking about and maybe neither was he. It's all OK so far though.

I'm going away for a week, tomorrow morning, so the house and the solar will be left to get on with whatever they want to do. I can watch what's happening while I'm away and maybe get a better handle on it all.

John, I live 760 feet up in the hills at 55 degrees north. Air conditioning isn't even on my radar.
 
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