Circular reasoning (Rolfe's solar energy system)

[Tangoed Man]

Just get a small petrol generator for goodness sake.

 

[Bam Bam]

I've splashed out on an EPS facility to add to the system.

Which option did you go for?

I went for the one where you have to manually switch it over, so I'd have to go outside.

It isn't automatic, which would be more convenient but that was much more expensive to add and I'm hoping not to have to use it often, all being well.

If the power goes out, the central heating boiler will continue to operate from the home battery (and that will heat the water tank as well), and I have a double power point in the fuse box cupboard that will be live.

From that I can run extension leads into the living room and kitchen to power the necessities. So now I think, how would I operate this if it ever turns out to be needed? I'm thinking maybe a four-socket extension lead from each of the live sockets.

That would probably work OK. Then at night, in a prolonged outage, the fridge and the freezer could be plugged in overnight and the'd hold their temperature reasonably well during the day. I'd just need to watch that just about everything else was turned off if I wanted to boil the kettle, or I'd trip something. The battery won't deliver much more than 3.5 kw.

Oh I see - you've got a few circuits?

That was the original option for the Givenergy system but they later added more options.

We've got the whole house backed up but will have to make sure to turn off all large appliances (like the car charger) before switching it over as the battery only offers 16a.

It is more convenient in some ways, but more risky I suppose because we might accidentally overload the inverter and it will shut down for 10 minutes and potentially reduce its lifespan.

I'd also have the option of running another extension cable in from the car and using that directly - as I did this morning when the whole system was off for the installation. I was able to hand the electrician a mug of hot coffee while he was working with the electricity off.

Like you I did this when we were having the backup system installed.

Haven't used it since!

For a day or so this would be absolutely fine, but what if it was more prolonged? (A friend of mine lost power in Sussex for a fortnight after the big storm of '88.) So long as there's a working charger close enough I could go get more electricity there. There's a big motorway service station with a stack of Applegreen chargers about 22 miles away, and Edinburgh is closer than that. However, I have no way (at the moment anyway) of getting power from the car into the home battery. I have no real idea what the boiler takes in a day - it depends on how hard it's working, and of course it cycles on and off.

We've got a heat pump now so that will require a lot of power.

It is only 16a though I think and rarely uses more than 1kW at a time so it might be fine to run off the battery, though the battery wouldn't last long.

I'm considering raising the idea of adding an additional battery with Pebbles and the extra backup potential could be another bonus I hadn't considered.

The solar will provide a top-up for the home battery during the day, but if the weather is bad I think it's possible it won't be enough. Of course I could run everything but the boiler directly from the car and just keep whatever is in the home battery for the heating, and probably over the days there would be enough solar.

I have to beware of hoping there will be a power cut just to try this out! It's just in case, for an emergency. But I do need to think about what I would do, to be prepared just in case.

If it is like ours you can just switch it over whenever you feel like it.

There was one time when I switched to backup power but was stuck on the backup long after the power came back on (it wasn't off for long). This was because I didn't want to interrupt a process that had started in the meantime. Can't remember what it was, maybe a software download/update process or bread making or laundry or something.

 

[Bam Bam]

Just get a small petrol generator for goodness sake.

Rolfe already had an expensive system that has a backup power option built in.

Why add an extra, separate, technology?

 

[Rolfe]

Rolfe already had an expensive system that has a backup power option built in.

Why add an extra, separate, technology?

Precisely. It had occurred to me to do something like this, at various points over the past 15 years or so. I have no idea how the power from that would be fed into the house and what it could support anyway. My former singing teacher had a generator but I never asked her how it interacted with the house wiring.

My backup plans were always to go to a neighbour who has a wood-burning stove if there was a power cut. This addition to the system is to avoid that necessity, particularly as these neighbours aren't getting any younger. If I can run the central heating reliably, I can manage fine for anything else with the live sockets in the house and the car's battery.

My only question is really, how much does the boiler take when it's running, and how likely is it that the solar would keep up? If it didn't, well, the neighbours are still there.

 

[Rolfe]

Which option did you go for?

I went for the one where you have to manually switch it over, so I'd have to go outside.

It isn't automatic, which would be more convenient but that was much more expensive to add and I'm hoping not to have to use it often, all being well.



Oh I see - you've got a few circuits?

That was the original option for the Givenergy system but they later added more options.

We've got the whole house backed up but will have to make sure to turn off all large appliances (like the car charger) before switching it over as the battery only offers 16a.

It is more convenient in some ways, but more risky I suppose because we might accidentally overload the inverter and it will shut down for 10 minutes and potentially reduce its lifespan.


Like you I did this when we were having the backup system installed.

Haven't used it since!

We've got a heat pump now so that will require a lot of power.

It is only 16a though I think and rarely uses more than 1kW at a time so it might be fine to run off the battery, though the battery wouldn't last long.

I'm considering raising the idea of adding an additional battery with Pebbles and the extra backup potential could be another bonus I hadn't considered.


If it is like ours you can just switch it over whenever you feel like it.

There was one time when I switched to backup power but was stuck on the backup long after the power came back on (it wasn't off for long). This was because I didn't want to interrupt a process that had started in the meantime. Can't remember what it was, maybe a software download/update process or bread making or laundry or something.

I thought I was getting one that would have to be manually switched over and I was OK with that, but when he was showing me the finished product it turned out that the switchover will happen automatically. I hope I don't get a nasty shock when I get the bill!

I'm slightly hazy about the specifics, but basically I've got the central heating boiler being fed from the battery, and that double power point to use as I like. It should be OK, because the boiler is using kerosene to produce the actual heat, the electricity is just running the pumps and so on. If you were using electricity to produce the actual heat I imagine it would be a different equation.

On the other hand, if export tariffs are going to be slashed, will we all be adding extra battery storage to keep our solar rather than exporting it? That would make a difference!

 

[Bam Bam]

My only question is really, how much does the boiler take when it's running, and how likely is it that the solar would keep up? If it didn't, well, the neighbours are still there.

According to an internet blog post I just read an oil burning boiler will use about 0.9kWh a day so not nothing but also not a huge amount.

 

[GaryMG4]

I guess but for a prolonged outage with little or no solar you will be hard pushed to run everything off a 13A socket.. a gas cartridge stove is a no brainer, 1970s or not.. or even a woodburner fire, now that is going back

When we moved here we seemed to get a lot of power cuts that lasted a couple of hours or so. Fortunately we already had a wood burner but I did buy a cartridge gas burner. Good insurance as we haven't had one since, of course now I can plug the boiler into the car if needed.

 

[Bam Bam]

I thought I was getting one that would have to be manually switched over and I was OK with that, but when he was showing me the finished product it turned out that the switchover will happen automatically. I hope I don't get a nasty shock when I get the bill!

I'm slightly hazy about the specifics, but basically I've got the central heating boiler being fed from the battery, and that double power point to use as I like. It should be OK, because the boiler is using kerosene to produce the actual heat, the electricity is just running the pumps and so on. If you were using electricity to produce the actual heat I imagine it would be a different equation.

On the other hand, if export tariffs are going to be slashed, will we all be adding extra battery storage to keep our solar rather than exporting it? That would make a difference!

I'm sure the price has come down as these things get more common.

I got this added when the car charger was put in. Didn't want to be stuck with a non-working potential backup system and regrets during a future power outage.

We shouldn't get power outages in Didcot given we are in the middle of England with a power station and power lines running in every direction but it did happen when they demolished the cooling towers which caused a fire in the local electricity network infrastructure.

 

[GaryMG4]

According to an internet blog post I just read an oil burning boiler will use about 0.9kWh a day so not nothing but also not a huge amount.

I think ours uses around 150w when running according to the IHD.

 

[Bam Bam]

On the other hand, if export tariffs are going to be slashed, will we all be adding extra battery storage to keep our solar rather than exporting it? That would make a difference!

Especially because there is a rumour that with an extra battery and a software update the Givenergy systems like ours might be able to output at higher rates in the future.

 

[Rolfe]

According to an internet blog post I just read an oil burning boiler will use about 0.9kWh a day so not nothing but also not a huge amount.

It's not many days I get less solar than that. Today was dull but I still got 2.1 kwh. (On Ne'erday this year I only got 340 watt-hours, but that was exceptionally bad.) If that's about all it takes, what with some days being better, it should be fine. If there was a prospect of a prolonged outage in very dull winter weather I could divert other uses from the home battery to the car.

I think ours uses around 150w when running according to the IHD.

It's not at all constant though. I see the usage go up when I turn the temperature up, and fall away when the set temperature is reached and the boiler goes back to sleep. It all depends on how much work it's being asked to do. If its peak draw is only 150 watts though, it's not going to add up to a huge amount given that it's intermittent. Maybe 1 kwh in a day is realistic.

For some reason I had been under the impression that the panels wouldn't work or feed into the system if the mains power was out. Maybe someone told me that they wouldn't export, which obviously they won't, and I misinterpreted it? But since that's not the case then I hardly need the car to charge the home battery, all I need to do is reserve the home battery for the boiler if things might be looking tight, and run everything else directly off the car.

 

[Rolfe]

Especially because there is a rumour that with an extra battery and a software update the Givenergy systems like ours might be able to output at higher rates in the future.

That I had not heard about. We'll see what happens. If they make it uneconomical to export then we'll just have to pump the Aussies for advice.

 

[T1 Terry]

That I had not heard about. We'll see what happens. If they make it uneconomical to export then we'll just have to pump the Aussies for advice.

We have quite a few hrs per day that the coal fired power stations have to pay to put power into the grid. This is because the grid is over supplied, they can switch off the solar on rooftops, turn wind turbines out of the wind, but coal fired power stations can't just turn off the steam turbine as they need to keep them spinning to be online and generating when the peak loads hit as the sun goes down.

The latest tech being built here in our home state, roughly 100kms away, is a device to connect the EV to the house and grid, and/or recharge from either supply.
This means, when the grid doesn't want your solar, the system charges the EV battery but also uses that battery to stabilise the energy supply if the sun has a cloud floating by and blocks production or the production drops significantly.

To add to the gains, particularly here in South Australia, they actually pay customers to take power from the grid for battery storage, but I expect that will dry up soon with some many big batteries coming on line throughout the state.

We have a lot of wind turbines and if the sun isn't shiny, you can count on the wind to be blowing, the problem is when both happen at the same time ..... so having a spare EV battery available to soak up some of that better than free electricity, can be a real bonus ......

T1 Terry

 

[decrep]

We have quite a few hrs per day that the coal fired power stations have to pay to put power into the grid. This is because the grid is over supplied, they can switch off the solar on rooftops, turn wind turbines out of the wind, but coal fired power stations can't just turn off the steam turbine as they need to keep them spinning to be online and generating when the peak loads hit as the sun goes down.

The latest tech being built here in our home state, roughly 100kms away, is a device to connect the EV to the house and grid, and/or recharge from either supply.
This means, when the grid doesn't want your solar, the system charges the EV battery but also uses that battery to stabilise the energy supply if the sun has a cloud floating by and blocks production or the production drops significantly.

To add to the gains, particularly here in South Australia, they actually pay customers to take power from the grid for battery storage, but I expect that will dry up soon with some many big batteries coming on line throughout the state.

We have a lot of wind turbines and if the sun isn't shiny, you can count on the wind to be blowing, the problem is when both happen at the same time ..... so having a spare EV battery available to soak up some of that better than free electricity, can be a real bonus ......

T1 Terry

I was hoping that would come to WA, but we are behind SA.
Also there's the matter of the car doing V2G.
We are signed up to the VPP, but that doesn't involve the car only the house battery.

 

[Everest]

My only question is really, how much does the boiler take when it's running, and how likely is it that the solar would keep up?

Ours (gas boiler for CH and HW) uses about 100W when it is running. The actual boilers themselves don't use much power, it is the water circulation pump that will typically be in the 60W to 90W range for an average sized house.

It's not at all constant though. I see the usage go up when I turn the temperature up, and fall away when the set temperature is reached and the boiler goes back to sleep. It all depends on how much work it's being asked to do. If its peak draw is only 150 watts though, it's not going to add up to a huge amount given that it's intermittent. Maybe 1 kwh in a day is realistic.

As above, when it is running and pumping it is consuming power. When idle, virtually nothing. So if you assume about 100W which is on for 25% to 50% of the time (depending on external temperature, humidity, wind etc. and how well your house is insulated) then from 600Wh to 1200Wh per day would be my finger-in-the-air estimate.

For some reason I had been under the impression that the panels wouldn't work or feed into the system if the mains power was out. Maybe someone told me that they wouldn't export, which obviously they won't, and I misinterpreted it? But since that's not the case then I hardly need the car to charge the home battery, all I need to do is reserve the home battery for the boiler if things might be looking tight, and run everything else directly off the car.

Depends on your inverter, but typically a hybrid inverter will use solar to top up the storage batteries when there is no AC Grid supply.

I thought I was getting one that would have to be manually switched over and I was OK with that, but when he was showing me the finished product it turned out that the switchover will happen automatically. I hope I don't get a nasty shock when I get the bill!

Then it sounds like your sparky has wired the household boiler and the two extra sockets to run from the backup output of the inverter, with an automatic switch that will perform a neutral to earth bond when the grid goes down. Typically they will have installed a new earth rod and RCD to provide protection should a fault occur in your boiler when running off the backup supply. If not, the nasty shock may not just be the bill!

Sounds like it has all be tested OK though.

 

[T1 Terry]

I was hoping that would come to WA, but we are behind SA.
Also there's the matter of the car doing V2G.
We are signed up to the VPP, but that doesn't involve the car only the house battery.

Your call there, but it will allow the electricity supply to charge your battery when power is at it's cheapest, then draw that power during peak periods, that rapid charging and discharging will not do a house battery any favours, but they don't care it's not their battery that getting excessively heavy cycling .....

T1 Terry

 

[T1 Terry]

I was hoping that would come to WA, but we are behind SA.
Also there's the matter of the car doing V2G.
We are signed up to the VPP, but that doesn't involve the car only the house battery.

This is the unit being manufactured in an Adelaide suburb Australian-made bidirectional (V2X) EV charger hits the market

A bit pricy at the moment, but the price will come down as more units are manufactured.

Rosie makes a good case for these units


T1 Terry