How much excess energy goes lost in solar and wind power stations?

  • #1
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Since solar and wind power are fluctuating energy sources not all of it goes into the grid when the consumer power demand is lower than that actually produced. This is a well-known drawback of solar and wind energy that everyone talks about. What I never found is an assessment of how much of the entire energy production goes lost (assuming that no kind of energy storage is used)? What is the order of magnitude, say for a big solar power plant supplying a little city/town? 10%, 30%, 50%? Does anyone know? Possibly with some respectable bibliographical source that makes this estimate?
 

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  • #2
jrmichler
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Your question is unclear, but here is some information that should help. Variations should really refer to the difference between generation and demand, because both vary.

There are short term variations, on the order of seconds to minutes, where utility scale batteries have been shown to respond faster than fuel burning power plants. Here is one link (there are others): https://www.washingtonpost.com/news...utages-in-record-time/?utm_term=.52e420d98702 . Batteries have been shown to be profitable for short term grid stabilization even without solar.

Then there is the diel variation in both demand and generation, which results in the duck curve (search that term): https://www.energy.gov/eere/articles/confronting-duck-curve-how-address-over-generation-solar-energy. This may be what you are asking about.

Hawaii, California, and Germany are dealing large amounts of solar generation relative to the total electric demand. I can't find the link where I read that Germany met 100% of their electric demand with solar for a couple of hours last summer, and about 30% of their total demand with solar. Here is one link (it's not the one I was looking for): https://www.cleanenergywire.org/news/renewables-cover-about-100-german-power-use-first-time-ever. I have read that solar without energy storage can realistically deliver about 30% of total demand.
 
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  • #3
russ_watters
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Since solar and wind power are fluctuating energy sources not all of it goes into the grid when the consumer power demand is lower than that actually produced. This is a well-known drawback of solar and wind energy that everyone talks about. What I never found is an assessment of how much of the entire energy production goes lost (assuming that no kind of energy storage is used)? What is the order of magnitude, say for a big solar power plant supplying a little city/town? 10%, 30%, 50%? Does anyone know? Possibly with some respectable bibliographical source that makes this estimate?
As far as I know, there is nowhere in the world - yet - that has enough solar generation capacity that they ever need to dump the power. In Europe they will occasionally say it happens for Germany with solar (or for wind in one of the Nordic countries), but then they just transfer the energy to other countries who aren't over-produced. Remember, electricity is transported very long distances, on giant, interconnected grids.

If we flip the question over, we can ask how much intermittent renewable capacity would be required before over-supply becomes a significant issue. The answer is probably somewhere on the order of 20-30% in annual energy production, which corresponds to about 100% of peak demand.
 
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  • #4
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Since solar and wind power are fluctuating energy sources not all of it goes into the grid when the consumer power demand is lower than that actually produced.
Usually, this is not true. To subsidy the generation of wind/solar electricity most countries has a policy to grant wind/solar power priority in the grid, and the regulation of the grid is completely done on the other sources. Based on this the right question would be about the increase of wear on the conventional power generation.
The relevant monetary part would also worth a rant but maybe some other time...

There are cases when the conventional power plants can't follow the changes of wind power, so to preserve the balance of the grid the operators are forced to touch the production of wind farms. This process is called 'curtailment': it will work as a search keyword. Pair it with 'renewables' or with 'wind' and give it a shot :smile:

As far as I know the sum rate of lost power due curtailment is/was around 5% of the sum of wind generation, but I lost tracking since the last PSTs were gone online around Germany.
 
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  • #5
tech99
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There is slight concern about how to manage the network now we have a lot of home solar generation in the UK. At the moment it is not managed as generating capacity, but as reduced consumer demand. It is conceivable that in summer, supply could exceed demand.
 
  • #7
anorlunda
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Since solar and wind power are fluctuating energy sources not all of it goes into the grid when the consumer power demand is lower than that actually produced.
Can you clarify your question? Your wording makes it sound like you are asking about curtailment. Indeed, that is what the answers so far address. But curtailment is a specialized term, usually not of interest to the general public.

Could it be that you meant to ask about capacity factor? i.e. The ratio of energy produced divided by the nameplate rating*elapsed time. That is a statistic discussed more frequently than curtailment.
 
  • #8
OmCheeto
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solar and wind power
As far as I know, there is nowhere in the world - yet - that has enough solar generation capacity that they ever need to dump the power.
Since Marco mentioned wind, I'd add that there have been several instances where, in my neighborhood, wind farms were forced to shut down due to lack of transmission infrastructure.

April 7, 2017​

Of course, this doesn't happen very often, and since wind capacity is currently so low, as a percentage as a power source, I'd say the answer to your question; "How much excess energy goes lost in solar and wind power stations?", Marco, is almost none.

From a previous post of mine on this topic:

Oct 27, 2012​
In all 10,100 megawatt hours of wind energy was curtailed over the two-day...

Interpolating the number of times this has happened, in my brain, and rounding a bit, I'm guessing the number is about 0.001% of tossed energy.

Which is close enough to almost none, IMHO.
 
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  • #9
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Information about renewable statistics and Wind/Solar curtailment in California.
https://www.pv-magazine.com/2018/05...-solar-power-renewable-energy-output-records/
Interesting bias in that story, complaining about how hydro and nukes can't change their output quick enough and should/are being turned off, I thought the overarching goal was zero carbon electricity, which both of those already produce, so does it not make sense to throttle the already highly variable zero carbon source (wind and solar) and let the constant output plants keep on trucking? So the diablo canyon plant was producing a steady 2.3GW zero carbon power 24hrs a day and thats actually the problem. lol.

Is it not the responsibility of the highly variable source to come up with some sort of storage scheme to deal with that excess if they randomly produce power no one needs that instant?
 
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  • #10
OmCheeto
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Interesting bias in that story, complaining about how hydro and nukes can't change their output quick enough and should/are being turned off, I thought the overarching goal was zero carbon electricity, which both of those already produce, so does it not make sense to throttle the already highly variable zero carbon source (wind and solar) and let the constant output plants keep on trucking? So the diablo canyon plant was producing a steady 2.3GW zero carbon power 24hrs a day and thats actually the problem. lol.

Is it not the responsibility of the highly variable source to come up with some sort of storage scheme to deal with that excess if they randomly produce power no one needs that instant?
Thanks for re-pointing out that link. I hadn't read it.

Interesting how I viewed the article as being mostly positive, while you seem to view it as being negatively biased. hmm.......

Btw, is this the section where you say they are complaining?:


"However, the state is showing less flexibility in other resources. Hydroelectric plants (purple) only reduced output slightly, falling to 2.3 GW during the middle of the day from 3.2 GW overnight. The Diablo Canyon nuclear power plant (tan) continued to run full bore, producing another 2.3 GW continuously."

Seems like less of a complaint, and more a statement of fact.

In any event, interesting data can be extrapolated from the article:


"The amount of curtailment is still low compared to overall generation. The 10 GWh of wind and solar curtailed on Saturday"​

Although they claim a 1% "dumping" figure, that's just for California.
If one includes the entire nation, you get back to my 0.001% dumped number.

Infrastructure, infrastructure, infrastructure..............
 
  • #11
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Thanks for re-pointing out that link. I hadn't read it.

Interesting how I viewed the article as being mostly positive, while you seem to view it as being negatively biased. hmm.......

Btw, is this the section where you say they are complaining?:

"However, the state is showing less flexibility in other resources. Hydroelectric plants (purple) only reduced output slightly, falling to 2.3 GW during the middle of the day from 3.2 GW overnight. The Diablo Canyon nuclear power plant (tan) continued to run full bore, producing another 2.3 GW continuously."

Seems like less of a complaint, and more a statement of fact.

In any event, interesting data can be extrapolated from the article:

"The amount of curtailment is still low compared to overall generation. The 10 GWh of wind and solar curtailed on Saturday"​

Although they claim a 1% "dumping" figure, that's just for California.
If one includes the entire nation, you get back to my 0.001% dumped number.

Infrastructure, infrastructure, infrastructure..............
It is a statement of fact, but to me its kind of backwards thinking though.

You have power sources that you knew in advance you cannot change their output quickly (hydro, older nuke) and then you have a power source that is highly variable and weather dependent. Then, because you have a personal preference for the highly variable weather dependent source(s) (I'm assuming this since its called pv magazine . com), you now say the issue is that these other plants can't adapt to this new power, rather than recognizing the actual issue, that the highly variable sources are not that useful if you need constant steady power unless they have some sort of storage (eg some of the solar thermal plants being proposed that store heat and use it when demand needs it).

There is also this quote:
"Nuclear advocates have repeatedly attempted to paint their chosen technology as a victim of unreasonable bias by environmentalists. However, utility Pacific Gas & Electric Company has acknowledged that inflexible nuclear power plants do not fit in a future of increasing wind and solar, which requires a higher degree of flexibility from the rest of the generation fleet. As such it is planning to close Diablo Canyon by 2026. "

What I don't understand is that based on their own data over a 24hr period the power consumed is more or less constant at 20GW, peaking at 25GW around 930pm, so I cannot understand the rationale of shutting down a continuous clean power stream because it can't throttle, your load is not throttling that much, the only reason you need to throttle it now is because oh, suns out from behind the clouds oh its gone again.

I'm for a rational, ideally bias free approach to carbon free energy production, its just doesn't seem like that is whats happening.

Now its not certain how the "imported" electricity is generated, but when you look at Califs other sources an un-biased analysis might be that California is already producing the bulk of its power carbon free (hyrdo, nuke, wind, solar), is only turning on gas to make up the short term difference, and is almost zero emissions from 10A till about 6pm. Quite an achievement IMO.

Maybe the better use of that excess wind/solar is pump the hydro back up the hill for use later.
 
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  • #12
anorlunda
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Thanks everyone. There are a number of misconceptions posted in this thread. That gives me the motivation to write a new Insights article on how power grid operators work both technically and economically. That just happens to be one of my favorite subjects, because that is the last thing I did before retirement; so I'm thanking you.

Give me 4-5 days and the article should be up. I'll post in this thread when it is.
 
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  • #13
OmCheeto
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Maybe the better use of that excess wind/solar is pump the hydro back up the hill for use later.
That's almost exactly what @zoobyshoe wrote 2 years ago.


Jun 1, 2017
zoobyshoe; "I don't know where you are posting from, but here in California I think we're at the point where we need storage:
http://www.pe.com/2017/03/18/heres-how-california-ended-up-with-too-much-solar-power/
I'm not sure what level of strain of the system you think is best, but there is already a strain, at least here.
" [bolding mine]​

We discussed it for quite a while.

I just found an interesting number in the article he referenced; "Last year 305,241 megawatt hours of solar and wind electricity were curtailed"

From that, I get a "dumped" number of 0.008%, which is 8 times higher than my earlier estimate. [pats self on back for trying to stay on topic. :oldbiggrin:]

That gives me the motivation to write a new Insights article on how power grid operators work both technically...
I've been corresponding with my sister in California again, and discovered that they have a program where you can install solar that matches your current electrical usage.
I've been an advocate of that for some time now. Mostly because I'm poor. hmmm..... I wonder how @Artman and his solar array are doing? [PF, circa 2009]

Anyways, if my neighbors were to hypothetically cut down their trees, so I could get some sun in the winter, and I were hypothetically to go back to work(fat chance!), how would the electricity from a 2 kilowatt solar array on my roof be distributed? I was originally thinking I would drive to work, plug in, and get my power from my array across the grid. But then I was thinking, that electricity takes the path of least resistance, and my array would power a bunch of my neighbors refrigerators, and my car would be powered from somewhere else.

Positive feature: This would cut down on line loses, if my assumption is correct.
 
  • #14
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Anyways, if my neighbors were to hypothetically cut down their trees, so I could get some sun in the winter, and I were hypothetically to go back to work(fat chance!), how would the electricity from a 2 kilowatt solar array on my roof be distributed? I was originally thinking I would drive to work, plug in, and get my power from my array across the grid. But then I was thinking, that electricity takes the path of least resistance, and my array would power a bunch of my neighbors refrigerators, and my car would be powered from somewhere else.
I've been contemplating solar as well, however quite different, my loose plan of sorts is put insulated water reservoir in my basement, at least a few cubic m, likely some glycol mixture for freeze/corrosion protection, then app 10m2 collector, use to warm reservoir during day, then heat pump to take that low grade heat and heat house in winter. So totally off topic, but at ~1kW/m2 heatflux seems decent way to knock out some of the fermented dinos I'm burning today.
 
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  • #15
OmCheeto
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I've been contemplating solar as well, however quite different, my loose plan of sorts is put insulated water reservoir in my basement, at least a few cubic m, likely some glycol mixture for freeze/corrosion protection, then app 10m2 collector, use to warm reservoir during day, then heat pump to take that low grade heat and heat house in winter. So totally off topic, but at ~1kW/m2 heatflux seems decent way to knock out some of the fermented dinos I'm burning today.
You need to do the maths!
I don't know where you live, but where I do, that system would save me about 0.01% of my heating bill. [Total guess on the percent. But I'm guessing it's within an order of magnitude.]

Btw, I don't think it's totally off topic. An expansion of Marco's question might be; "What would happen to the Fossil Fuel industries, if everyone installed just their baseline electrical and thermal needs to their homes?*"

hmmmm...... Could hydroelectric cover the storage deficit?

*ps. Mentors, OK! I'll start a new thread.........

[edit] Done!
 
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  • #16
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You need to do the maths!
I don't know where you live, but where I do, that system would save me about 0.01% of my heating bill. [Total guess on the percent. But I'm guessing it's within an order of magnitude.]

Btw, I don't think it's totally off topic. An expansion of Marco's question might be; "What would happen to the Fossil Fuel industries, if everyone installed just their baseline electrical and thermal needs to their homes?*"

hmmmm...... Could hydroelectric cover the storage deficit?

*ps. Mentors, OK! I'll start a new thread.........

[edit] Done!
I have lol, which is why I keep coming back to it. Even just running my chincy little air source heat pump as long as I can into fall before I kick the furnace on and then as soon as its warm enough in the spring saves me maybe ~450L oil a winter. The first winter paid for the heatpump (on sale for ~$600), and I don't really notice a significant impact on electric bill.
 
  • #17
sophiecentaur
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There is slight concern about how to manage the network now we have a lot of home solar generation in the UK. At the moment it is not managed as generating capacity, but as reduced consumer demand. It is conceivable that in summer, supply could exceed demand.
One factor that would make controlling solar power production relatively easy is the fact that we are only dealing with 1kW/m2. A cheap solution would be to use silvered blinds to cover excess PV area. An instant and very undramatic form of control. Motors could use local power.
 
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A cheap solution would be to use silvered blinds to cover excess PV area.
Erm... I think an even cheaper solution would be to tell the uController in the inverter of the PV-field the required output to follow through the so called 'IoT' :wink:
 

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