Circular reasoning (Rolfe's solar energy system)

[Rolfe]

The sun came out. I saw over 6 kW from the panels at one point.

The battery and inverter in their final configuration.

And Zappi.

Now all I need is to learn how to use all this kit.

 

[Archev]

The sun came out. I saw over 6 kw from the panels at one point.

View attachment 26580

The battery and inverter in their final configuration.

View attachment 26581

And Zappi.

View attachment 26582

Now all I need is to learn how to use all this kit.

That’s tremendous and a really tidy looking job - Caliban’s looking chuffed ?

 

[Rolfe]

And the Zappi has a long enough lead that he can charge while sitting on the drive even though it's fitted in the garage.

That’s tremendous and a really tidy looking job - Caliban’s looking chuffed ?

Caliban, actually, barely got a taste of sunbeam before he was switched off. I set up a <10% to 100% charge last Friday but ditched the entire thing a third of the way through to go and watch the aurora. A video going on about hysteresis curves convinced me that this negated the entire exercise.

So I'm trying to get back down to under 10% tomorrow afternoon to try again. Testing the Zappi is not helping here.

 

[Smudger558]

I'll just use the one from my installer - seems only polite!

Not a lot to show for it so far, the roofing guys have gone off to another job, see you tomorrow.

View attachment 26521

And the electrician has just left too.

View attachment 26522

Nevertheless he says he reckons the solar system will be up and running tomorrow, though it might be Thursday before the car charger is done.

I've got givenergy batteries 2x8.2 and inverter and they have been spot on

 

[Archev]

Caliban, actually, barely got a taste of sunbeam before he was switched off. I set up a <10% to 100% charge last Friday but ditched the entire thing a third of the way through to go and watch the aurora. A video going on about hysteresis curves convinced me that this negated the entire exercise.

So I'm trying to get back down to under 10% tomorrow afternoon to try again. Testing the Zappi is not helping here.

He he that makes an interesting change. Twice today in Banchory and then in Braemar I blathered on when ansked about range not being of any real interest nowadays as the ev can usually outrange the bladder. Yet here we are trying to bleed off some range in order to balance things and monitor that available distance more accurately???
Och, you get the drift. Did I just disappear up my non existent exhaust pipe

 

[Rolfe]

Caliban is getting the sunbeams after all, albeit second hand. Although economy was great going to Glasgow in the late afternoon, on the way home the temperature had dropped to 10°C and of course it's uphill. And I was driving Caliban like I'd stolen him, don't judge me.

So I needed about another 15 miles to be comfortable about tomorrow morning's trip to Edinburgh. It was nearly half past eleven when I got home and no way was I going to try to get to grips with the Zappi, so he's on the granny charger, taking the electrons stored in the battery from Thursday's sun.

I'll stop the charge manually about two in the morning, I hope he'll only have taken about half of the battery. Hopefully it will all start again at five in the morning, with the sunrise.

Unless there's a haar.

 

[GaryMG4]

Caliban is getting the sunbeams after all, albeit second hand. Although economy was great going to Glasgow in the late afternoon, on the way home the temperature had dropped to 10°C and of course it's uphill. And I was driving Caliban like I'd stolen him, don't judge me.

So I needed about another 15 miles to be comfortable about tomorrow morning's trip to Edinburgh. It was nearly half past eleven when I got home and no way was I going to try to get to grips with the Zappi, so he's on the granny charger, taking the electrons stored in the battery from Thursday's sun.

I'll stop the charge manually about two in the morning, I hope he'll only have taken about half of the battery. Hopefully it will all start again at five in the morning, with the sunrise.

Unless there's a haar.

Our panels are SSW facing so it wasn't until 8:30 this morning we started to produce excess above our base load. time to get the washing on then plug the car in.

 

[Rolfe]

It's all going rather well, learning curve, trial and error and all that. Yesterday was a bust because I decided I wanted to do the long charge on the car come hell or high water. Might have been better to do it today which is very sunny (also I could have started it in the morning), but I didn't want it sitting there at 7% for nearly 24 hours in case I needed it. So, I have credit with my old supplier (whose electricity I was still using, though over to Octopus today) and I thought, just get it done. I did manage to get most of yesterday's sunshine into the car one way or another, although there was still a big chunk of grid used.

So today is pretty sunny and I'm getting to grips with it all. I could see a few watts coming from the panels as early as 4 am (sunrise is at 5 am) and by 6.30 am they were producing enough to cover all the baseline house load. The battery started charging soon afterwards. The system was exporting a bit by 9 am and this ramped up.

I ran the washing machine to mop up some of the pointless export (I'm not getting paid for it yet), then as it was finishing I realised I hadn't switched on the immersion heater as my installer had told me to, and the water wasn't very hot. So I did that, and that scooped up a lot more that might have been exported. Once it was done I turned on the dishwasher (by now full of a lot of mugs, as I had to give the installer and the roofer a constant supply of coffee). It's interesting to see the pattern of usage of the different appliances. I can see why my aunt, not well off and very frugal, was paranoid about using her immersion heater as little as possible.

The sunshine fluctuated in the early morning, but after 8.30 the sky must have cleared because it just ramped up and up. Then about 11 am, when it was reading 6.4 kw, it eased off to 5.3 kw and it has remained stable since then. My panels face the sun at about 11-11.30 am so I think the easing off must have been the sky hazing over, although it's not that obvious from the ground. That 5.3 kw generation has now been constant for an hour and a half.

I should take the washing in from the line as it's already dry, but I'll have lunch first. It really is a scorcher. Certainly no reason to see what the tumble drier uses today! Once the dishwasher is done (in about 15 minutes) there's nothing special to do, and I'll just watch these electrons going to the grid as a free gift.

Such a sunny day has been a good exercise in seeing how much everything takes, and figuring out how and when to run things without needing battery power or grid power. The system has taken nothing from the grid since about 6.20, when the solar really kicked in, and I don't think I was switched over to Octopus until about 8 am. New game. See how long I can go from now without actually drawing from the grid. (I haven't yet managed to switch to a variable tariff.)

 

[Rolfe]

Just for my own interest, here's the power graph of this morning, from the point (6.25 am) where the panels were able to supply the house, and then start recharging the empty battery.

Export began at 8.50 and ramped up. The first peak in demand, about 9.30, was the washing machine going on. The second, about 10.45, was the immersion heater. That took a lot. The third and fourth peaks were both caused by the dishwasher. Interesting that the second peak was so high - about 5 kw - although short.

Also interesting is the ramping up in the solar as the morning progressed, which is what I would have expected, then the drop and levelling off at 5.6 kw from 11 am, which is not what I expected. The sky doesn't look hazy, but there must be enough there to diffuse the light and smooth out changes caused by the height and angle of the sun.

So now I have a full battery, a tank of hot water, washing to take in and a dishwasher to empty. I can't think of anything else to do with all these photons except make a present of them to the grid. Tonight I will find out how an ordinary evening goes with switching on lights and the TV and so on, and how much that takes from the battery.

 

[Bam Bam]

Just for my own interest, here's the power graph of this morning, from the point (6.25 am) where the panels were able to supply the house, and then start recharging the empty battery.

View attachment 26628


Also interesting is the ramping up in the solar as the morning progressed, which is what I would have expected, then the drop and levelling off at 5.6 kw from 11 am, which is not what I expected. The sky doesn't look hazy, but there must be enough there to diffuse the light and smooth out changes caused by the height and angle of the sun.

Strange that the PV input dropped at the point your battery was full. Is that a coincidence or by design?

I can't see the KW figures here, but is it because the export is limited? So you can exceed the limit amount when the battery is available but once it is full you can't? Is the inverter limited until you get the G99 approval for instance?

If true then you might want to set it up to export more earlier on if possible, so that the battery doesn't fill up as quickly and you can get more of the midday peak into the battery.

Just a theory!

 

[Rolfe]

I don't think there's anywhere to put the surplus solar except into the grid. If there's a way to limit the actual generation by the PVs then I don't know about it. But there's a lot I don't know.

I ended up a bit hazy about whether the inverter was limited until I get approval. My impression was he had expected to get approval quickly but when it didn't come through he went ahead anyway. The message I got was "don't ask don't tell" until the approval came through, not that he would then come and delimit something. But I could be wrong. It could be as you say.

It's hard to tell anything from yesterday as the sun was more intermittent. The battery reached full about three o'clock, and before that there was a short peak of generation that reached 7.37 kw. Afterwards I could perhaps persuade myself that there was a shoulder where generation levelled off around 5.3 kw. Maybe.

Certainly when I strolled round to my neighbour's house a little while ago the sky appeared clear and the panels were in full sun. So your explanation seems plausible. Every day is a school day.

 

[johnb80]

I ran the washing machine to mop up some of the pointless export (I'm not getting paid for it yet), then as it was finishing I realised I hadn't switched on the immersion heater as my installer had told me to, and the water wasn't very hot. So I did that, and that scooped up a lot more that might have been exported. Once it was done I turned on the dishwasher (by now full of a lot of mugs, as I had to give the installer and the roofer a constant supply of coffee). It's interesting to see the pattern of usage of the different appliances. I can see why my aunt, not well off and very frugal, was paranoid about using her immersion heater as little as possible.

Did you not get EDDI installed as part of your setup? I'm sure you talked about it. If you do have, leave it switched on all of the time.

 

[Rolfe]

Yes, that's what my installer said to do. I thought he had left it switched on, but when I realised the water wasn't very hot this morning I checked and it had been sitting there switched off. So when I switched it on it had a bit of catching up to do.

I see it seems to be cutting in from time to time with a spike of usage. At least I assume that's what it is, there isn't anything else on that could do that. I was going to ask, should I switch it off once the sun has gone, because there really isn't any point in keeping on boosting the temperature unless there are free photons. But you have confirmed what my installer said. So it keeps the water scalding while there's free solar, and then what? How does it work when there isn't?

 

[johnb80]

Yes, that's what my installer said to do. I thought he had left it switched on, but when I realised the water wasn't very hot this morning I checked and it had been sitting there switched off. So when I switched it on it had a bit of catching up to do.

I see it seems to be cutting in from time to time with a spike of usage. At least I assume that's what it is, there isn't anything else on that could do that. I was going to ask, should I switch it off once the sun has gone, because there really isn't any point in keeping on boosting the temperature unless there are free photons. But you have confirmed what my installer said. So it keeps the water scalding while there's free solar, and then what? How does it work when there isn't?

EDDI works in two ways, one on a schedule so you can heat the water off peak and the second it diverts all export thats going to the grid into your immersion, it aims to keep your export at zero. If theres say 700w being exported it will feed that 700w into your immersion. As the Solar increases or decreases and / of house loads change, so does EDDI, it's a brilliant piece of kit. Set the schedule for peak and then forget it, it will do its stuff. If you need to boost the hot water for any reason, in the app you can set it to boost for 'x' hours etc.

 

[Rolfe]

By the way, I think you're dead right about the system limiting generation when the battery is full. The pattern of the top being sliced off the curve is very clear now, and as you say, it starts when the battery is full.

You can also see the peaks of the hot water. I think what I thought was a very high peak just before the dishwasher finished was actually a hot water boost coinciding with the dishwasher doing something.

EDDI works in two ways, one on a schedule so you can heat the water off peak and the second it diverts all export thats going to the grid into your immersion, it aims to keep your export at zero. If theres say 700w being exported it will feed that 700w into your immersion. As the Solar increases or decreases and / of house loads change, so does EDDI, it's a brilliant piece of kit. Set the schedule for peak and then forget it, it will do its stuff. If you need to boost the hot water for any reason, in the app you can set it to boost for 'x' hours etc.

Thanks. I'm not at the stage of messing with the settings as yet, baby steps. The installer did say something about this, but it's a lot to take in. Clearly I'm not going to need to boost the hot water for a while though! And I do have the option of asking the oil-fired central heating to do a hot water boost if I want. Although the installer said, now we're in the business of you not using any more oil until autumn.

I need to experiment, but it might be cheaper (or indeed even free) just to run an electric fan heater in the living room in the evening for a bit, if it gets chilly then, than to crank up the central heating boiler.

It's tea-time, and I'm tempted to put something on to cook, just to see how it works. Probably use a bit of battery. But it's too hot to eat a hot meal!

 

[Bam Bam]

By the way, I think you're dead right about the system limiting generation when the battery is full. The pattern of the top being sliced off the curve is very clear now, and as you say, it starts when the battery is full.

View attachment 26634

You can also see the peaks of the hot water. I think what I thought was a very high peak just before the dishwasher finished was actually a hot water boost coinciding with the dishwasher doing something.



Thanks. I'm not at the stage of messing with the settings as yet, baby steps. The installer did say something about this, but it's a lot to take in. Clearly I'm not going to need to boost the hot water for a while though! And I do have the option of asking the oil-fired central heating to do a hot water boost if I want. Although the installer said, now we're in the business of you not using any more oil until autumn.

I need to experiment, but it might be cheaper (or indeed even free) just to run an electric fan heater in the living room in the evening for a bit, if it gets chilly then, than to crank up the central heating boiler.

It's tea-time, and I'm tempted to put something on to cook, just to see how it works. Probably use a bit of battery. But it's too hot to eat a hot meal!

Yes I'm not sure how it works exactly but surely it must happen - if you had a smaller inverter than the panels could produce in full soon then it is "clipped off." Perhaps if the inverter cannot make a circuit then the electrons won't move in the panels?

I'd be curious to know what those levelled off amounts are between 1130 and 1630 - the yellow and orange. Are either of those 5kw or 3.68kw? That would indicate export-based clipping I think.

 

[Archev]

Yes, that's what my installer said to do. I thought he had left it switched on, but when I realised the water wasn't very hot this morning I checked and it had been sitting there switched off. So when I switched it on it had a bit of catching up to do.

I see it seems to be cutting in from time to time with a spike of usage. At least I assume that's what it is, there isn't anything else on that could do that. I was going to ask, should I switch it off once the sun has gone, because there really isn't any point in keeping on boosting the temperature unless there are free photons. But you have confirmed what my installer said. So it keeps the water scalding while there's free solar, and then what? How does it work when there isn't?

By all means keep the water in the cylinder very hot but have it at around 50 C at the kitchen and a max of 38 / 42 C at the taps on the wash hand basins and baths. Temperature blending valves can be fitted beneath / behind those taps to regulate the max temperatures at those taps. This leaves the storage cylinder at max temperature which makes the hot water “last“ longer and prevents bacteria build up.
I went to a tragic case of a wee laddie of three who had been scalded because the cylinder thermostat was set to max allowing nearly 80 C water to all taps in the house. That wee soul lost I think three fingers and suffered many skin grafts after trying to be helpful washing his own hands when everyone else was distracted.

 

[Rolfe]

Yes I'm not sure how it works exactly but surely it must happen - if you had a smaller inverter than the panels could produce in full soon then it is "clipped off." Perhaps if the inverter cannot make a circuit then the electrons won't move in the panels?

I'd be curious to know what those levelled off amounts are between 1130 and 1630 - the yellow and orange. Are either of those 5kw or 3.68kw? That would indicate export-based clipping I think.

It clips at 5.3 kw. The orange is just 5.3 minus the current house load, so the exported power.

 

[Archev]

By the way, I think you're dead right about the system limiting generation when the battery is full. The pattern of the top being sliced off the curve is very clear now, and as you say, it starts when the battery is full.

View attachment 26634

You can also see the peaks of the hot water. I think what I thought was a very high peak just before the dishwasher finished was actually a hot water boost coinciding with the dishwasher doing something.



Thanks. I'm not at the stage of messing with the settings as yet, baby steps. The installer did say something about this, but it's a lot to take in. Clearly I'm not going to need to boost the hot water for a while though! And I do have the option of asking the oil-fired central heating to do a hot water boost if I want. Although the installer said, now we're in the business of you not using any more oil until autumn.

I need to experiment, but it might be cheaper (or indeed even free) just to run an electric fan heater in the living room in the evening for a bit, if it gets chilly then, than to crank up the central heating boiler.

It's tea-time, and I'm tempted to put something on to cook, just to see how it works. Probably use a bit of battery. But it's too hot to eat a hot meal!

I’m loving these progress reports. Why not make a loaf or two of bread while you have a salad ? ??

 

[Bam Bam]

I’m loving these progress reports. Why not make a loaf or two of bread while you have a salad ? ??

Yeah I started using a bread machine we inherited much more when we had the solar installed!

The electricity expense of it had been putting me compared to store-bought. Once I got on the givenergy App I realised it wasn't drawing as much as I feared anyway.