Circular reasoning (Rolfe's solar energy system)

[GaryMG4]

After a few amazingly sunny days I'm now seeing what happens when it's dull. Seeing, not experiencing, because I'm staying with friends on the south coast and watching it all on the app.

It is incredible how much difference it makes. In the last 3 weeks we have generated a third of the amount for the previous 6 months! In 3 weeks I have purchased 130 kWh, put 140kWh through the granny charger and been paid £86 so far in FiT (381 kWh x 23p) payments. Hopefully this year the FiT payments will cover most of the standing charge and all the electricity used, all depends on the cap prices I guess.

 

[Rolfe]

Fingers crossed!

Well, today, with only a little more sun, it managed to get the battery to 100% and heat the water (how hot I'm not sure) and export a negligible amount.

 

[decrep]

If it exported anything at all, I'd hope your water was fully up to temperature

 

[Coulomb]

If it exported anything at all, I'd hope your water was fully up to temperature

Ideally, yes. But control systems are never perfect. An inverter will typically "accidentally spill" some energy back into the grid when a load suddenly turns off. So exporting a negligible amount doesn't necessarily indicate that the hot water is fully hot.

 

[Rolfe]

Yes, I've noticed that. There's a more or less constant noise of chatter between the house and the grid that amounts to bugger-all, even if there's an occasional transient spike of 100 or even 200 watts. Even if what I saw was a real attempt at export (it wasn't a spike) it was transient and didn't exceed about 120 watts.

 

[johnb80]

Yes, I've noticed that. There's a more or less constant noise of chatter between the house and the grid that amounts to bugger-all, even if there's an occasional transient spike of 100 or even 200 watts. Even if what I saw was a real attempt at export (it wasn't a spike) it was transient and didn't exceed about 120 watts.

You've been very quiet, how's it all going?

 

[Rolfe]

I've been away from home for over a week, just got back. There are a few teething problems, in that first the GivEnergy app/web site stopped talking to me, then the battery started to insist on being charged overnight on cheap rate rather than running the house till morning and charging on sunshine. This morning everything was all over the place for a couple of hours.

However the car is currently charging on sunshine which would otherwise be gifted to the grid (7.5 kWh added so far), the water is hot, and my installer is coming for a look-see this afternoon. Getting there.

 

[Bam Bam]

the GivEnergy app/web site stopped talking to me

I've had a 'comms failure' on a couple of occasions, where the link between givenergy and the inverter was down. I think it was caused by a spike which threw off the little meter in my consumer unit and it lost the connection until I reset it.

Fortunately I have not had any problems getting on my account with the app/web portal itself, in the 14 months I have had it.

then the battery started to insist on being charged overnight on cheap rate

Strange that your settings changed- did you give Octopus your login details?

I am on intelligent Flux and Octopus has in the last couple of days shifted from charging the battery during daylight to an overnight schedule, which I had not seen in the previous month I've had the tariff.

Hopefully your issues can get sorted.

 

[Rolfe]

I think it was related to downloading the MyEnergi app and inadvisedly trying to give that my Octopus details. I don't know how to reset anything, it may be that the inverter is playing silly buggers for some reason. Everything seems OK at the moment though, getting close to 10 kWh added to the car battery (just as well as I was relying on that for a 100-mile trip this evening), and hopefully the installer will be along this afternoon.

 

[gus]

I have GivEnergy with an Eddi, works well for me, I have it charging up to 60% in the summer on the overnight cheap tariff - I’m with EdF. I have the Eddi set to only heat the water when there is more than 300W available for more than 30 secs otherwise it is on and off all the time. I have also set the thermostat to be above the temp the boiler would heat it to, that way I can have the boiler heat the water in the morning if their wasn’t enough sun the day before.

 

[Rolfe]

I don't yet know how to alter these settings, but my Eddi seems to have a good session in the morning as soon as there's enough surplus solar to heat the water, then spikes in a bit more every couple of hours or so to keep it to temperature while it can.

My installer has been and gone and the GivEnergy stuff is back online. He also says he's fixed it so the battery won't try to charge from the grid overnight. The car is now at 91% (from 61% this morning when I plugged it in to the sunshine, having gobbled up 15.95 kWh) although the sun is going in now. Anyway, I have enough charge to get to Glasgow and back tonight and to Edinburgh and back tomorrow morning, so we'll see how long it takes to get to 100% after that lot, on sunshine alone. I'm not going anywhere much over the weekend (it's the start of the village gala week here) and it's supposed to be quite sunny, so we'll see what the system is capable of.

It's now raining...

 

[johnb80]

I have the Eddi set to only heat the water when there is more than 300w available for more than 30 secs otherwise it is on and off all the time.

Just out of interest, why do you see that as an issue?

My installer has been and gone and the GivEnergy stuff is back online. He also says he's fixed it so the battery won't try to charge from the grid overnight.

Why? surely you will be losing out here if the weather is poor / wintertime etc, you need to charge overnight.

 

[Rolfe]

It can be changed, obviously. When he set up the system the battery was charging from the sunshine during the day, powering the house all night, then charging on sunshine again the next day. This is perfect, and correct for summer.

However at midnight on Saturday it changed, and the battery started drawing from the grid to recharge itself at midnight, then the house ran from the grid until 4am. This was causing an entirely unnecessary grid usage of about 2.5 kWh every night. Not a lot at cheap rates but it adds up, and the game in summer is to avoid grid usage whenever possible.

He said it should be possible to leave it all running from sunshine all summer maybe in October it will start to be necessary to put some grid energy into the battery overnight as there won't be enough sun.

Right now, since I'm not being paid for grid export and I'm chucking a lot of excess sunshine their way in the afternoons, I do resent unnecessary grid draw.

Well, it's past midnight and all is well. House running nicely from the battery, no grid import. Considering that sunrise is about 4.40 am it's not going to have to do it for long. Next objective, to see if I can run the car entirely on excess solar till the end of next week (when I'm going away again).

I realise priorities will change once I'm getting paid for the excess solar, but that could take another six weeks.

 

[johnb80]

It can be changed, obviously. When he set up the system the battery was charging from the sunshine during the day, powering the house all night, then charging on sunshine again the next day. This is perfect, and correct for summer.

It may be correct from the green perspective but it isnt from the financial angle. Export all you can during the generation times, run the house on the battery alone. As you approach evening time you also export the spare battery capacity. All of the exports will earn 15p/kWh on Octopus. At 23:30 you then charge the batteries fully and run the immersion via EDDI to charge and reheat at 7.5p/kWh Car is also charged at this time.

However at midnight on Saturday it changed, and the battery started drawing from the grid to recharge itself at midnight, then the house ran from the grid until 4am. This was causing an entirely unnecessary grid usage of about 2.5 kWh every night. Not a lot at cheap rates but it adds up, and the game in summer is to avoid grid usage whenever possible.

Initially those were my thoughts until I looked further into the game we play with energy supply.

He said it should be possible to leave it all running from sunshine all summer maybe in October it will start to be necessary to put some grid energy into the battery overnight as there won't be enough sun.

Yep, its definitely noticeable the drop off after September and the generation as we pass through March.

Right now, since I'm not being paid for grid export and I'm chucking a lot of excess sunshine their way in the afternoons,

Have you applied for an export tariff with Octopus (or someone else)? It took them about 5 days after I had sent them copies of all of the paperwork (MCS Cert etc).

I do resent unnecessary grid draw.

Agreed, me too, but think about the service you can offer and turn the situation around completely that you would be a net exporter of energy to the grid for the same 6 months as above but still reduce your energy costs more by exporting all generated energy and running on batteries charged off peak, buy at 7.5p, sell at 15p whats not to like?

 

[johnb80]

Well, it's past midnight and all is well. House running nicely from the battery, no grid import. Considering that sunrise is about 4.40 am it's not going to have to do it for long. Next objective, to see if I can run the car entirely on excess solar till the end of next week (when I'm going away again).

Its a very nice feeling, rates highly on the smugness scale running a car on daylight

I realise priorities will change once I'm getting paid for the excess solar, but that could take another six weeks.

Why 6 weeks ?

 

[Rolfe]

John, I DON'T HAVE AN EXPORT TARIFF. Scottish Power are playing hardball for reasons best known to themselves. It's all very well saying "export all you can at 15p" if you can do that, but I can't, yet. I'm forced to make them a free gift of the excess. So obviously I'm using as much solar for myself as I can to avoid grid usage.

Water now hot, washing machine running, and when I get back from Edinburgh the car will be plugged in.

I can change it all around once I get that export tariff, but there's no point telling me what to do as if I had it already.

 

[johnb80]

John, I DON'T HAVE AN EXPORT TARIFF.

Rolfe: NO NEED TO SHOUT, I'M NOT DEAF.
I was responding to your statement "This is perfect, and correct for summer." It isnt really, thats all, it may be a good way to operate in view of your current no export status but it aint perfect.

Scottish Power are playing hardball for reasons best known to themselves.

Fight back, contact the Ombudsman.

I'm forced to make them a free gift of the excess. So obviously I'm using as much solar for myself as I can to avoid grid usage.

Of course, goes without saying

I can change it all around once I get that export tariff, but there's no point telling me what to do as if I had it already.

Well thats me told, gob well and truly shut, enjoy your solar no matter how you decide to run it.

 

[Rolfe]

Sorry, I just got tired of the repeated "but it's better to export as much as you can for 15p" because I can't do that yet. I do appreciate that priorities change when the export tariff is available, but at the moment, the way my system is is perfect for me in summer, using no grid energy and grabbing all the solar I can for my own use.

Today I had piping hot water when I got up, put a load of washing on before I went out, lost almost 15 kWh because I was out so no way to put it in the car, then got back, and since then have grabbed 12 kWh and counting. And the sunshine is drying the washing the old-fashioned way.

Tomorrow is looking quite sunny and the car isn't going anywhere. I doubt if I'll get enough to fill it, but I'm going to give it a try. (I'd need about 30 kWh, which seems a bit ambitious.)

 

[Alb]

Sounds like cheap electricity in exchange for 5 years off your life through added stress

 

[Rolfe]

It's a learning curve. I'm currently figuring it out so that I can operate it without thinking about it once I know how it works. It's just an irritant that the G99 is taking so long. I think it will be a lot easier once that has come through, but it's educational to see how it works when export payments aren't available.

Its a very nice feeling, rates highly on the smugness scale running a car on daylight


Why 6 weeks ?

John, I'm genuinely sorry if I upset you. I very much value your advice. My post you replied to, which was under this one, was in fact a reply to the post before it - I hadn't seen this one.

It is highly smug. I reckon if it's as sunny as I hope tomorrow I might just get the car up to 100% and balance, with luck. That's after bringing it back on about 28% late last night, then driving it down to 18% this morning.

Why six weeks, you ask? My installer thought it would be quick, but they knocked him back. Why, he asked. He said there's nothing at the premises before this installation, no complications at all. They said it's not the property it's the street. We're simply guessing that it's something to do with my next door neighbour having the same set-up installed over a year ago. There is also a house across the road that has had 16 PV panels and a FIT tariff for a long time.

Although his last comment when I asked why they were being obstructive was probably nearest the mark. "Because they can." Apparently they have a certain number of working days to respond, and that takes us into July. I can't make any waves because apparently he shouldn't have made the system live at all prior to the G99 being issued, or at the very least limited the inverter to 3.5 kW. However he didn't, and we're on a "don't ask don't tell" basis here.