What percentage of PV energy is usable?

Clive_Woody

A naive question from someone waiting for their solar panels to be fitted, do you have an app that tracks use and calculates utilisation or do people obsessively keep spreadsheets to track this?

We're getting panels, battery and an iBoost so lots of fun data to track 😁

JKenH

Martyn1981 said:

Petriix said:

Exiled_Tyke said:

Petriix said:

arty688 said:

Also people use the term free electricity usually around the iboost stuff , it's not free its what ever you export rate is say 5p. So if you are comparing against gas and savings you need to use that figure. Having said that it defiantly greener and is a good thing to do.

I don't think it necessarly is 'greener'. Exported electricity almost exclusively reduces gas generation at ~ 60% round trip efficiency. A gas boiler is typically 80% efficient so it's likely 'greener' to burn gas at home and export the electricity.

For those of us on deemed exports, however, it is use it or lose it. 

But apparently about 38% of UK electricity come from fossil fuels (27% gas)

https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/1032260/UK_Energy_in_Brief_2021.pdf

so the issue is whether your argument for 'almost exclusively reduces gas generation' is valid or not. I can see the logic for this but I'm not convinced it's necessarily the case. It could just as easily reduce imported nuclear leccy from France? 


The argument that each kWh of home useage is money saved does of course need more investigation. I'm sure most homes generating from solar change their habits, some more about convenience rather than pure money saving: putting on a tumble drier rather than hanging out washing on a sunny day, doing that extra load of laundry or dishwasher cycle because the electricity is free etc.. 

It doesn't matter how much of the overall generation comes from gas. The fact is that *immediate demand* is almost exclusively met by burning gas. They're the main type of power station able to ramp up fast enough so they effectively carry the load for all the small changes in usage across the grid.

It's obviously vastly more complicated than that. But, in practice, the more solar you export the less gas generation there is. Obviously there are some other technologies and, as grid scale storage increases, the picture is changing. However, I don't think it's reasonable to claim that the nuclear base load has any impact on the CO2 emissions caused by drawing an extra 3kW from the grid. 

Yep very complicated, and something that comes up every so often.

The 'marginal generation' argument for gas might now be starting to get questionable, especially whenever there is some RE curtailment.

It’s not that complicated at the moment. If you plug something additional into the grid  then most days the extra power to run it is going to come from gas or coal. We can’t step up wind or solar as they are nearly always running at max output. If we need more power we up the gas and coal. This is why we have been generating more than 50% of our electricity from fossil fuels these last few days. I take the point on days that wind has to be curtailed it may provide marginal generation but that is the exception.

Anyone who has filled their EV up in the last week has triggered an increase in coal or gas generation even if the sun was shining on their solar panels. It might not have cost them anything but their neighbours electricity got a bit less green. 

mickyduck55

as @Exiled_Tyke suggests we do alter our behaviour but personally I would never run the drier when the sun is shining.. re the dishwasher and washing machine I use them when I need to as the ancillaries used in these processes also cost .. tablets, powder, softener etc.  My dishwasher goes on when its full, the good news is that I dont have to switch it on at 2 am because I usually have the power either from solar, battery or a combination of both.

My main change even before the addition of batteries has been not running high usage items in parallel, I wont often have the washing machine and Dishwasher on at the same time.  Im retired so not time restrained. 

ATM I am baking bread.. no power is being taken from the grid as I have about 1.5 kWh from the solar topped up from my 100% charged battery... done LOL

JKenH

Solarchaser said:

Those who have batteries can play a good role in decarbonising the grid as most will be on a time of use tarriff, and so will be discharging the batteries to cover the house load when the grid is dirtiest and most expensive, and also refilling the batteries when the grid is greenest.
Win win really.

Not really over the last week or so. Any charging of batteries whether from your own solar or the grid has contributed to the amount of gas generation required because of the efficiency losses during the charging and discharging cycles. 10-20% more energy will have been needed from the grid than if you had simply powered the devices from live generation. It just isn’t possible for the grid to ramp up renewable energy to charge your batteries or car at night. Perhaps the proportion of gas in the grid is lower but you are adding marginal load. The only time that it is going to come from renewables is when we are curtailing wind.

There is a tendency to confuse cheap electricity with clean electricity.

arty688

Although you can't really look at these things on a day by day you have to look at the longer term . So over say 12 months do batteries help decarbonise ?
Is now what you would call normal or the new normal ?
I know when I was on Agile the cheaper periods usually greener where in the early hours.

Martyn1981

JKenH said:

Martyn1981 said:

Petriix said:

Exiled_Tyke said:

Petriix said:

arty688 said:

Also people use the term free electricity usually around the iboost stuff , it's not free its what ever you export rate is say 5p. So if you are comparing against gas and savings you need to use that figure. Having said that it defiantly greener and is a good thing to do.

I don't think it necessarly is 'greener'. Exported electricity almost exclusively reduces gas generation at ~ 60% round trip efficiency. A gas boiler is typically 80% efficient so it's likely 'greener' to burn gas at home and export the electricity.

For those of us on deemed exports, however, it is use it or lose it. 

But apparently about 38% of UK electricity come from fossil fuels (27% gas)

https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/1032260/UK_Energy_in_Brief_2021.pdf

so the issue is whether your argument for 'almost exclusively reduces gas generation' is valid or not. I can see the logic for this but I'm not convinced it's necessarily the case. It could just as easily reduce imported nuclear leccy from France? 


The argument that each kWh of home useage is money saved does of course need more investigation. I'm sure most homes generating from solar change their habits, some more about convenience rather than pure money saving: putting on a tumble drier rather than hanging out washing on a sunny day, doing that extra load of laundry or dishwasher cycle because the electricity is free etc.. 

It doesn't matter how much of the overall generation comes from gas. The fact is that *immediate demand* is almost exclusively met by burning gas. They're the main type of power station able to ramp up fast enough so they effectively carry the load for all the small changes in usage across the grid.

It's obviously vastly more complicated than that. But, in practice, the more solar you export the less gas generation there is. Obviously there are some other technologies and, as grid scale storage increases, the picture is changing. However, I don't think it's reasonable to claim that the nuclear base load has any impact on the CO2 emissions caused by drawing an extra 3kW from the grid. 

Yep very complicated, and something that comes up every so often.

The 'marginal generation' argument for gas might now be starting to get questionable, especially whenever there is some RE curtailment.

It’s not that complicated at the moment. If you plug something additional into the grid  then most days the extra power to run it is going to come from gas or coal. We can’t step up wind or solar as they are nearly always running at max output. If we need more power we up the gas and coal. This is why we have been generating more than 50% of our electricity from fossil fuels these last few days. I take the point on days that wind has to be curtailed it may provide marginal generation but that is the exception.

Anyone who has filled their EV up in the last week has triggered an increase in coal or gas generation even if the sun was shining on their solar panels. It might not have cost them anything but their neighbours electricity got a bit less green. 

Yep, most days, so as I said, the marginal argument is now getting ever more questionable. The additional demand may be addressed by additional RE if there is localised curtailment, or from intraday storage of RE generation now that grid supply storage is starting to roll out, and of course last month we saw gas down to just a few GW's, so it's possible soon that additional demand at times may come from national RE curtailment as I suggested and you except is now an exception but crucially, not zero going forward. Though of course I appreciate that this will depend on locality and transmission issues.

So, yes, the iffy marginal argument is getting iffier. [Wow, didn't even know that was a real word!]

Petriix

Some great points here. I still think reducing 'peak' grid usage, even with 20% round trip losses, is a good thing. It's the peak demand which dictates whether the coal power stations are spun up at all. If we keep our peak imports low then we directly impact the overall make-up of the generation mix.

Regarding tracking usage: many systems have apps, APIs and stats which we can view. I currently use a combination of my smart meter data and the information from the Myenergi app attached to my Zappi car charging point.

Solarchaser

JKenH said:

Solarchaser said:

Those who have batteries can play a good role in decarbonising the grid as most will be on a time of use tarriff, and so will be discharging the batteries to cover the house load when the grid is dirtiest and most expensive, and also refilling the batteries when the grid is greenest.
Win win really.

Not really over the last week or so. Any charging of batteries whether from your own solar or the grid has contributed to the amount of gas generation required because of the efficiency losses during the charging and discharging cycles. 10-20% more energy will have been needed from the grid than if you had simply powered the devices from live generation. It just isn’t possible for the grid to ramp up renewable energy to charge your batteries or car at night. Perhaps the proportion of gas in the grid is lower but you are adding marginal load. The only time that it is going to come from renewables is when we are curtailing wind.

There is a tendency to confuse cheap electricity with clean electricity.

I'm tempted to say speak for yourself, but instead I'll remind you once again that the generation in Scotland is alot more green than Middle England.
Mid day today southern Scotland was by Scottish standards pretty dirty, i seen 180g on eso app, so the fact I was using solar plus batteries to fill the leaf (for the wifes work tonight) rather than charging from the grid makes them somewhat more green.

Now we are under 100g, its definitely greener to charge the batteries just now, which will be much more likely to be excess wind rather than getting them to turn on more gas middle of the day, and we seem to be supplying quite a bit of Northern England's power too which brings the North of England a bit cleaner.
Certainly better than getting supplied by middle England which is unfortunately burning well over 300g (dont even look at east midlands)including rather a large amount of coal 😥

Which is not to say my whole motivation for batts was being green, it wasn't.
However charging batts when there is much less strain on the grid, and so much less likely to be coming from dirty coal can only be a good thing surely??

JKenH

Solarchaser said:

JKenH said:

Solarchaser said:

Those who have batteries can play a good role in decarbonising the grid as most will be on a time of use tarriff, and so will be discharging the batteries to cover the house load when the grid is dirtiest and most expensive, and also refilling the batteries when the grid is greenest.
Win win really.

Not really over the last week or so. Any charging of batteries whether from your own solar or the grid has contributed to the amount of gas generation required because of the efficiency losses during the charging and discharging cycles. 10-20% more energy will have been needed from the grid than if you had simply powered the devices from live generation. It just isn’t possible for the grid to ramp up renewable energy to charge your batteries or car at night. Perhaps the proportion of gas in the grid is lower but you are adding marginal load. The only time that it is going to come from renewables is when we are curtailing wind.

There is a tendency to confuse cheap electricity with clean electricity.

I'm tempted to say speak for yourself, but instead I'll remind you once again that the generation in Scotland is alot more green than Middle England.
Mid day today southern Scotland was by Scottish standards pretty dirty, i seen 180g on eso app, so the fact I was using solar plus batteries to fill the leaf (for the wifes work tonight) rather than charging from the grid makes them somewhat more green.

Now we are under 100g, its definitely greener to charge the batteries just now, which will be much more likely to be excess wind rather than getting them to turn on more gas middle of the day, and we seem to be supplying quite a bit of Northern England's power too which brings the North of England a bit cleaner.
Certainly better than getting supplied by middle England which is unfortunately burning well over 300g (dont even look at east midlands)including rather a large amount of coal 😥

Which is not to say my whole motivation for batts was being green, it wasn't.
However charging batts when there is much less strain on the grid, and so much less likely to be coming from dirty coal can only be a good thing surely??

It is no surprise that the East Midlands generation is so dirty as that is where the coal fired stations are located. It is very virtuous of you Scots to consume such green electricity when those of us in the East Midlands are so dirty in our consumption. 

I am sure, however, those of you living in the Central Belt were grateful when you put the kettle on for a cuppa this morning that the whole grid is interconnected so you could enjoy the contribution from coal in the East Midlands. At 7am today renewables (which I presume are the mainstay of Scotland’s clean generation) were providing just 0.42GW of the total UK demand of 30 GW, and probably around a tenth of consumption in the Central Belt. 

Edit: it was interesting to see that in the early hours of yesterday North Scotland’s grid was 30 times dirtier than that of the North East.

https://carbonintensity.org.uk/

Petriix

JKenH said:

Solarchaser said:

JKenH said:

Solarchaser said:

Those who have batteries can play a good role in decarbonising the grid as most will be on a time of use tarriff, and so will be discharging the batteries to cover the house load when the grid is dirtiest and most expensive, and also refilling the batteries when the grid is greenest.
Win win really.

Not really over the last week or so. Any charging of batteries whether from your own solar or the grid has contributed to the amount of gas generation required because of the efficiency losses during the charging and discharging cycles. 10-20% more energy will have been needed from the grid than if you had simply powered the devices from live generation. It just isn’t possible for the grid to ramp up renewable energy to charge your batteries or car at night. Perhaps the proportion of gas in the grid is lower but you are adding marginal load. The only time that it is going to come from renewables is when we are curtailing wind.

There is a tendency to confuse cheap electricity with clean electricity.

I'm tempted to say speak for yourself, but instead I'll remind you once again that the generation in Scotland is alot more green than Middle England.
Mid day today southern Scotland was by Scottish standards pretty dirty, i seen 180g on eso app, so the fact I was using solar plus batteries to fill the leaf (for the wifes work tonight) rather than charging from the grid makes them somewhat more green.

Now we are under 100g, its definitely greener to charge the batteries just now, which will be much more likely to be excess wind rather than getting them to turn on more gas middle of the day, and we seem to be supplying quite a bit of Northern England's power too which brings the North of England a bit cleaner.
Certainly better than getting supplied by middle England which is unfortunately burning well over 300g (dont even look at east midlands)including rather a large amount of coal 😥

Which is not to say my whole motivation for batts was being green, it wasn't.
However charging batts when there is much less strain on the grid, and so much less likely to be coming from dirty coal can only be a good thing surely??

It is no surprise that the East Midlands generation is so dirty as that is where the coal fired stations are located. It is very virtuous of you Scots to consume such green electricity when those of us in the East Midlands are so dirty in our consumption. 

I am sure, however, those of you living in the Central Belt were grateful when you put the kettle on for a cuppa this morning that the whole grid is interconnected so you could enjoy the contribution from coal in the East Midlands. At 7am today renewables (which I presume are the mainstay of Scotland’s clean generation) were providing just 0.42GW of the total UK demand of 30 GW, and probably around a tenth of consumption in the Central Belt. 

Edit: it was interesting to see that in the early hours of yesterday North Scotland’s grid was 30 times dirtier than that of the North East.

https://carbonintensity.org.uk/

The grid is (unfortunately) less 'interconnected' than you would hope. There are severe limitations on getting the green generation from the outlying areas to where the demand is. This is something that is improving and the subject of significant investment.