Grid Integration of Large-Scale Renewables

Jim Martin

This says it all, that they're pretty much a waste of time & space!

Red Neck Hughie

http://www.eirgrid.com/operations/systemperformancedata/systemdemand/
yesterdays demand graphically, from 2.5 to 4.5GW.
In the same period wind varied from .4 to 1.4GW. How exactly is it difficult to incorporate wind when there are far bigger variations in daily demand anyway?

Chloe Pink

Red Neck Hughie wrote: »

How exactly is it difficult to incorporate wind when there are far bigger variations in daily demand anyway?

Off the OP to some degree but as you ask, it's the variations in the power source that are problematic not the variations in demand.

Macha

Chloe Pink wrote: »

Off the OP to some degree but as you ask, it's the variations in the power source that are problematic not the variations in demand.

Actually more accurately, it is the matching of the two.

Chloe Pink

Macha wrote: »

Actually more accurately, it is the matching of the two.

To a point but take the following scenarios:
1) non variable demand with controllable, predictable supply
2) variable demand with controllable, predictable supply
3) non variable demand with uncontrollable, unpredictable supply
4) variable demand with uncontrollable, unpredictable supply
The point is that even if we had a non variable demand i.e. a constant demand, an uncontrollable, unpredictable supply wouldn't be able to match it.

djpbarry

Chloe Pink wrote: »

Off the OP to some degree but as you ask...

[MOD]Just so everyone is aware, this is now a new thread for discussion of renewable intermittency & grid interconnection/integration.[/MOD]

Chloe Pink

djpbarry wrote: »

[MOD]Just so everyone is aware, this is now a new thread for discussion of renewable intermittency & grid interconnection/integration.[/MOD]

Thanks just noticed while responding to Macha's post

L

Chloe Pink wrote: »

The point is that even if we had a non variable demand i.e. a constant demand, an uncontrollable, unpredictable supply wouldn't be able to match it.

I think Macha's closer to the ball on this one. Nobody in their right mind would consider running a power system that couldn't be controlled.

All the power system really cares about is the difference between demand and available supply. If you can dump demand or increase power generation, it doesn't really matter to it which you do.

Red Neck Hughie wrote: »

How exactly is it difficult to incorporate wind when there are far bigger variations in daily demand anyway?

There's two major reasons:

one: wind and demand variability can add (as in, if you have 400MW of additional demand unexpectedly and 100MW less wind generation, you have 500MW of power supply to scrape together from somewhere).

two: wind and demand variability are quite different in nature. Demand is very predictable (as an example of some of the factors in plain English: night time demand will drop as people go to sleep, match day demand will probably have a peak around the time of a match). Wind much less so (wind forecasts are still good, they're just *different*).

Chloe Pink

L wrote: »

All the power system really cares about is the difference between demand and available supply.

Absolutely but if you can control the supply, meeting demand is considerably easier than if you can't control the supply.

To expand on RNH's valid observation, "How exactly is it difficult to incorporate wind when there are far bigger variations in daily demand anyway?":

As long as a power system only has about 10%-15% of its total installed capacity as wind, it can generally cope because fluctuations in supply from the wind generators are mangeable in the same way that a variation in demand or a power station outage is manageable.

It's as the level of installed wind capacity, as a percentage of the total power system, increases beyond this point that current systems struggle to cope.

Macha

Where are you getting the 10-15% limit from?

Chloe Pink

Macha wrote: »

Where are you getting the 10-15% limit from?

I've based it roughly on UK figures which refer to 10 GW (+/–25%).
"Ample evidence from relatively large wind systems in Denmark and Germany exists to prove that 10 GW (+/–25%) will be the probable safe upper limit of all wind capacity."
See footnote 2 at this link:http://www.ref.org.uk/publications/227-new-study-confirms-ref-intermittency-studies

Macha

Chloe Pink wrote: »

I've based it roughly on UK figures which refer to 10 GW (+/–25%).
"Ample evidence from relatively large wind systems in Denmark and Germany exists to prove that 10 GW (+/–25%) will be the probable safe upper limit of all wind capacity."
See footnote 2 at this link:http://www.ref.org.uk/publications/227-new-study-confirms-ref-intermittency-studies

Seems odd that you're so comfortable extrapolating to such an extent when the level of renewables that can be integrated depends on such varying factors.

Chloe Pink

Macha wrote: »

Seems odd that you're so comfortable extrapolating to such an extent when the level of renewables that can be integrated depends on such varying factors.

It's not just that:
Every power system is built with a degree of over capacity to cope with unexpected and planned outages.
Assume an intermittent and unpredictable power source is built to replace a controllable power source.
Taking into account the probablilty that peak demand and an unexpected and/or planned outage occur simultaneously, some of the over capacity could be used to replace the loss of the intermittent and unpredictable power source.
Thereafter, another means of replacing the loss of the intermittent and unpredictable power source is needed.

pljudge321

Chloe Pink wrote: »

It's not just that:
Every power system is built with a degree of over capacity to cope with unexpected and planned outages.
Assume an intermittent and unpredictable power source is built to replace a controllable power source.
Taking into account the probablilty that peak demand and an unexpected and/or planned outage occur simultaneously, some of the over capacity could be used to replace the loss of the intermittent and unpredictable power source.
Thereafter, another means of replacing the loss of the intermittent and unpredictable power source is needed.

Is that installed capacity or capacity credit?

Macha

Chloe Pink wrote: »

It's not just that:
Every power system is built with a degree of over capacity to cope with unexpected and planned outages.
Assume an intermittent and unpredictable power source is built to replace a controllable power source.
Taking into account the probablilty that peak demand and an unexpected and/or planned outage occur simultaneously, some of the over capacity could be used to replace the loss of the intermittent and unpredictable power source.
Thereafter, another means of replacing the loss of the intermittent and unpredictable power source is needed.

Renewables are not intermittent and unpredictable. They are variable but predictable to a point - and predictions are improving. Traditional fossil fuel & nuclear plants can shut down with no warning so it isn't accurate to portay power sources as you have.

You haven't considered the issue of demand management, which is becoming more likely as the technology develops.

And I'm still not convinced that extrapolations out from the UK system are at all valid (or indeed useful) for other power system.

L

Macha wrote: »

And I'm still not convinced that extrapolations out from the UK system are at all valid (or indeed useful) for other power system.

They're not valid for another power system. The UK isn't set up with the same plant mix we have and plant mix is king when it comes to the amount of wind you can integrate. Offhand, I think we've actually got a higher percentage of wind on the system at the moment than those limits suggest.

Chloe Pink

Macha wrote: »

Renewables are not intermittent and unpredictable. They are variable but predictable to a point - and predictions are improving.

It depends on the renewables you are referring to; tides for example are predictable, wind remains tricksy to predict.

Oxford dictionary
Intermittent - occurring at irregular intervals; not continuous or steady
Variable - not consistent or having a fixed pattern; liable to change
Call it as you will, but some renewables are not baseload or demand generators except hydro and biomass although it could be argued that hydro is a form of storage rather than a generator.

Macha wrote: »

Traditional fossil fuel & nuclear plants can shut down with no warning so it isn't accurate to portay power sources as you have.

I refer to post 60 of this thread (page 4) where EON UK describe the difference between the availability of conventional generator output and the availability of wind generation output; 95% versus 8%.
It is completely misleading to compare the unexpected outage of a conventional power station to the unexpected outage of a renewable such as wind for example.
http://www.publications.parliament.u...95/8061708.htm

Macha wrote: »

You haven't considered the issue of demand management, which is becoming more likely as the technology develops.

See pdf at this link, http://www.poyry.com/media/media_2.html?Id=1301471113.html
"Overall we found that, while ‘demand-side’ involvement may be attractive, the wide range of likely deployment patterns and technological developments will further complicate investment decisions – and quite possibly slow deployment."

Macha wrote: »

And I'm still not convinced that extrapolations out from the UK system are at all valid (or indeed useful) for other power system.

Any suggestions on what might be...

pljudge321

L wrote: »

They're not valid for another power system. The UK isn't set up with the same plant mix we have and plant mix is king when it comes to the amount of wind you can integrate. Offhand, I think we've actually got a higher percentage of wind on the system at the moment than those limits suggest.

We've got ~6 GW of dispatchable plant and ~1.9 GW of wind with a capacity credit of around 300 MW.

Chloe Pink

L wrote: »

... plant mix is king when it comes to the amount of wind you can integrate. Offhand, I think we've actually got a higher percentage of wind on the system at the moment than those limits suggest.

Could you elaborate please L on the mix in Ireland and the percentage of installed wind capacity it could cope with etc

djpbarry

Chloe Pink wrote: »

...wind remains tricksy to predict.

That really depends on the time-scale.

Chloe Pink wrote: »

It is completely misleading to compare the unexpected outage of a conventional power station to the unexpected outage of a renewable such as wind for example.

But nobody is comparing them - the wind is extremely unlikely to suddenly stop blowing.

Chloe Pink wrote: »

See pdf at this link, http://www.poyry.com/media/media_2.html?Id=1301471113.html
"Overall we found that, while ‘demand-side’ involvement may be attractive, the wide range of likely deployment patterns and technological developments will further complicate investment decisions – and quite possibly slow deployment."

That looks like little more than an off-hand dismissal.

Macha

Chloe Pink wrote: »

It depends on the renewables you are referring to; tides for example are predictable, wind remains tricksy to predict.

Of course. But I wouldn't say wind is "tricky" to predict. We do it quite well, actually. Biogas is not only predictable, it's dispatchable.

Chloe Pink wrote: »

I refer to post 60 of this thread (page 4) where EON UK describe the difference between the availability of conventional generator output and the availability of wind generation output; 95% versus 8%.
It is completely misleading to compare the unexpected outage of a conventional power station to the unexpected outage of a renewable such as wind for example.
http://www.publications.parliament.u...95/8061708.htm

Why? Sorry but a wind load factor of 8% is totally incorrect. Off the wall stuff.

Chloe Pink wrote: »

See pdf at this link, http://www.poyry.com/media/media_2.html?Id=1301471113.html
"Overall we found that, while ‘demand-side’ involvement may be attractive, the wide range of likely deployment patterns and technological developments will further complicate investment decisions – and quite possibly slow deployment."

I wouldn't agree with that, and neither does the IEA. Load shifting is one of a suite of measures that allow greater integration of RES and studies have shown consumers respond strongly to better pricing signals. This paper has a few references: http://www.iea.org/papers/2011/sg_cust_pol.pdf

Chloe Pink wrote: »

Any suggestions on what might be...

On what might be what? Sorry this doesn't make sense to me.

Re: energy mix data - you've been posting on energy here long enough to know where to find Ireland's energy mix statistics: http://www.seai.ie/Publications/Statistics_Publications/EPSSU_Publications/ or CSO.

L

Chloe Pink wrote: »

Could you elaborate please L on the mix in Ireland and the percentage of installed wind capacity it could cope with etc

Well, without going into too much detail (and again without looking the specific figures up), we've a large amount of plant capable of starting up quickly to compensate for variation between demand and supply (off the top of my head, I think we've about 4000 MW of assorted gas and distillate midmerit and peakers, but that's without figures so I'm probably out by a bit).

In contrast, Britain IIRC, is mainly Coal/Nuclear (IIRC about 50,000 MW from a 90,000 MW total). Large chunks of their system is sluggish to start up and designed to just keep running once it's generating.

In other words, Britain needs to be looking further out along their forecasts to match their demand. With demand, that's not so bad. With wind forecasts, each additional hour you have to look ahead increases the possible error you have to look at (that's a bit of a simplification but it's broadly correct). In other words, the higher proportion of quick start up plants you have, the higher percentage of wind you can accommodate because you can plan with less uncertainty.

Chloe Pink wrote: »

Macha wrote: »

And I'm still not convinced that extrapolations out from the UK system are at all valid (or indeed useful) for other power system.

Any suggestions on what might be...

The All Island Grid Study would be a reasonable place to start. They did some simulation with a chunk of different portfolios Ireland could have by 2020. There's also some work Eirgrid did on how much wind capacity we could cope with but I can't for the life of me remember what it's under or the specifics of it.

pljudge321

L wrote: »

Well, without going into too much detail (and again without looking the specific figures up), we've a large amount of plant capable of starting up quickly to compensate for variation between demand and supply (off the top of my head, I think we've about 4000 MW of assorted gas and distillate midmerit and peakers, but that's without figures so I'm probably out by a bit).

In contrast, Britain IIRC, is mainly Coal/Nuclear (IIRC about 50,000 MW from a 90,000 MW total). Large chunks of their system is sluggish to start up and designed to just keep running once it's generating.

In other words, Britain needs to be looking further out along their forecasts to match their demand. With demand, that's not so bad. With wind forecasts, each additional hour you have to look ahead increases the possible error you have to look at (that's a bit of a simplification but it's broadly correct). In other words, the higher proportion of quick start up plants you have, the higher percentage of wind you can accommodate because you can plan with less uncertainty.



The All Island Grid Study would be a reasonable place to start. They did some simulation with a chunk of different portfolios Ireland could have by 2020. There's also some work Eirgrid did on how much wind capacity we could cope with but I can't for the life of me remember what it's under or the specifics of it.

Britain rely on gas for around 45% of their electricity generation, they have loads of CCGT plants.

From what I remember from the All Island Study it found that the grid would become (n-1) unstable if the instantaneous amount of the load being met by wind exceeds around 70%.

Chloe Pink

L wrote: »

Offhand, I think we've actually got a higher percentage of wind on the system at the moment than those limits suggest.

Just to be clear, the limits were given with reference to "replacing" installed capacity; "adding" capacity to an already fully functioning system is another matter.

Chloe Pink

Macha wrote: »

Of course. But I wouldn't say wind is "tricky" to predict. We do it quite well, actually. Biogas is not only predictable, it's dispatchable.

I used the word "tricksy" actually and included the fact that biomass offers demand side management which means its despatchable.

Macha wrote: »

Why? Sorry but a wind load factor of 8% is totally incorrect. Off the wall stuff.

Eon UK, part of Eon Netz - you know the big guys in Germany with lots of experience of wind, are not referring to load factor here!

Macha

Chloe Pink wrote: »

I used the word "tricksy" actually and included the fact that biomass offers demand side management which means its despatchable.

What exactly is the difference in meaning?

Chloe Pink wrote: »

Eon UK, part of Eon Netz - you know the big guys in Germany with lots of experience of wind, are not referring to load factor here!

Let's not lower this into an argument from authority. Eon UK are not the guardians of the truth on wind any more than any other private energy company.

If they're not referring to load factor, what are they referring to?

Edit: Oh and that link isn't working.

Chloe Pink

Macha wrote: »

What exactly is the difference in meaning?

Tricky (of a task, problem, or situation) requiring care and skill because difficult or awkward
playful or mischievous.
Tricksy ingenious, intricate, or complicated

Macha wrote: »

Let's not lower this into an argument from authority. Eon UK are not the guardians of the truth on wind any more than any other private energy company.

If they're not referring to load factor, what are they referring to?

Edit: Oh and that link isn't working.

Here's the link and I believe they're referring to capacity credit, http://www.publications.parliament.uk/pa/ld200708/ldselect/ldeconaf/195/8061708.htm

Macha

Chloe Pink wrote: »

Tricky (of a task, problem, or situation) requiring care and skill because difficult or awkward
playful or mischievous.
Tricksy ingenious, intricate, or complicated

In the context of your post, I still don't understand the difference. Can you explain further?

Chloe Pink wrote: »

Here's the link and I believe they're referring to capacity credit, http://www.publications.parliament.uk/pa/ld200708/ldselect/ldeconaf/195/8061708.htm

Can you explain what you mean by capacity credit in this context?

Chloe Pink

Macha wrote: »

In the context of your post, I still don't understand the difference. Can you explain further?

There isn't alot of difference, it was just a matter of accuracy regarding quoting another poster.

Macha wrote: »

Can you explain what you mean by capacity credit in this context?

I can't really put it any more clearly than has already been done by Eon in the link provided which I also quoted from in post 60. Eon wrote the document for non energy experts so it's fairly easy to understand.
But in it's simplist form, it's the percentage of installed capacity that can be relied upon to be there when it's needed.

Chloe Pink

djpbarry wrote: »

That really depends on the time-scale.

Which timescale please?

djpbarry wrote: »

But nobody is comparing them - the wind is extremely unlikely to suddenly stop blowing.

Macha was

djpbarry wrote: »

That looks like little more than an off-hand dismissal.

Hardly, if you look at the report; can you provide any evidence to contradict Poyry's findings.