[robomartin]

Where is the math? All I see is a link to a book.

Without going too deep: If you need 100% backup for solar, why use solar?

I built a 13 kW array. During recent rains I saw it go down to 600 W peak output. Without 100% backup it would be pointless. I can’t charge electric cars with this, it isn’t enough. I’d have to install a ridiculous amount of storage to to make it viable for a range if use cases. Four years ago, when I installed it, I was idealistic about solar. Four years later I understand the hard-cold reality vs. the fantasy of solar.

[Schroedingersat]

> Without going too deep: If you need 100% backup for solar, why use solar?

In addition to this being a lie, if we pretend it's true then there's a sufficient reason. Solar costs less than the marginal cost of other generation except wind.

[robomartin]

What is a lie? That solar is so unreliable that you need 100% backup or accept shutting down entire buildings or towns?

That is far from a lie.

I just got back from a business trip to Singapore. Among other places, I visited a food production building where we have installed some of our technology for more efficient indoor farming. This building houses some 240 companies. They have a massive solar array sourcing a good deal of their power.

It rained almost constantly for two weeks. That massive array went to nearly zero output during that time.

The only way that building could function was with 100% backup for solar, provided by the grid.

Batteries? The batteries were drained within a day. They could only be replenished by the use of grid power. Once again, 100% backup.

Not sure how you can possibly call it a lie.

This backup can take many forms. Where it makes sense, batteries might be able to help (yet batteries are not magic and they need a reliable power source to charge). A reliable power grid that can provide 100% of the load at any given moment is a must. This grid might be fed by solar (at a different geographic location), wind, hydro, nuclear or burning something. I believe in Singapore's case it is mostly burning gas.

It might seem sensible to think in terms of a wide geographic distribution of solar arrays to supply city A when weather events render the local solar resources unusable. OK, well, at a minimum, then, you need a 100% backup array located elsewhere. Let's call it 1000 km away.

Sounds great. You are betting on the statistical improbability of both arrays being unusable. Weather patterns being what they are, this might be a sensible bet.

What nobody brings into these conversations is: What happens with cities and towns B, C, D, E, F, G, etc.

If both A and C rely on a B's array for weather event mitigation, B's array has to be overbuilt by a massive factor to, at any given time, supply all of A, B and C's power requirements (or combinations thereof). The same become the case for A and C, as they might be required to supply their 1000 km neighbors.

At the end of the day, I think everyone is starting to understand the ways in which solar and wind are unreliable. The idea that mitigation requires 100% backup can't really be disputed at scale.

Put a different way, as I have said elsewhere, one would have to overbuild solar by an obscene multiplier (some have estimated as much as 70x) to achieve the equivalent of a reliable power source across a wide geographical area.

The UK have a massive solar and wind project bringing them power from Morocco, some 4000 km away. Sounds great...until there's a problem. If the cities using this power don't have 100% reliable backup there will be trouble.

Frankly, it does not help that articles such as this one provide false information that get repeated and becomes widely distributed:

https://www.energy.gov/eere/articles/how-much-power-1-gigawa...

Here, the energy department claims 3.125 million 320 W panels give you 1 GW.

Not even close. First, 320 W panels NEVER make 320 W.

Why?

That rating is at 25° C and ideal lighting conditions. Panels have a negative temperature coefficient. At real operating temperatures they do not output the rated peak output. At actual operating temperatures you will lose 5% to 7% of that. Add other real-life installation factors and 10% is likely a very safe estimate.

That means a 320 W panel will, at best, under ideal condition, produce somewhere in the range of 290 to 300 W peak for a few seconds at the top of the solar day.

That would bring the 3.125 million panel installation down to 938 MW (assuming 300 W peak per panel) for 15 to 30 seconds per day.

Just to deliver a 1 GW peak for a few seconds we have to multiply the number of panels by a factor of almost 7%. That brings the count up to 3.344 million panels.

However, these panels will not produce the equivalent of 1GW of power for 24 hours. If the intent is to get there with solar, we need more panels and lots of batteries.

How many panels?

Well, on a perfect day the power generation curve is an inverted parabola. The integral of that curve over time gives us the energy generated during that period. Doing the math we see that is 66% of the equivalent 12 hour constant power period.

That means we need to multiply the size of the array by 1.5 to collect the equivalent constant power energy over 12 hours. That brings us to 6.688 million panels.

And, yes, lots of batteries are required for this to work.

Next, we need to at least double this to collect energy to supply at night. That gets the count up to 13.376 million 320 W panels. And millions of batteries.

That number is 4.3 times larger than what the energy department mistakenly quotes in the linked article.

And yet this does not stop there. One could (should?) easily double the size of this array yet again to account for weather, dirt and failures. If I round that out to a 10x multiple, we now need 31.25 million panels to supply a steady 1GW day and night while only using solar power.

What remains to be calculated is the massive land use this represents. One cannot just use the size of the panels. Solar installations have a packing factor. The idea is that you need space around the panels for access, maintenance, installation and other needs.

That number seems to be in the order of 10 acres per MW of peak generation:

https://www.nrel.gov/docs/fy13osti/56290.pdf

In the case of this realistic 1GW plant with 31.25 million panels, the land requirement would be about 100K acres. This is about 156 square miles or a square of over 12 miles per side.

[Schroedingersat]

An incredibly incoherent and long winded way of saying you don't know the term 'capacity factor' and don't understand what dispatchable loads are isn't evidence you weren't lying.

As to the amount of backup needed: https://www.nature.com/articles/s41467-021-26355-z

Then consider all the dispatchable loads that decrease the gap even further.

[robomartin]

You excel at insulting people online. We've been here before. This is what you do instead of having conversations. Not taking your bait.

My claim is that solar requires 100% backup.

OK, let's break it down:

    Solar Output:
    Under ideal conditions, roughly inverted parabolic output

    1.00 ┼                       ╭────╮                   
    0.90 ┤                     ╭─╯    ╰─╮                 
    0.80 ┤                   ╭─╯        ╰─╮               
    0.70 ┤                  ╭╯            ╰╮              
    0.60 ┤                 ╭╯              ╰╮             
    0.50 ┤                 │                │             
    0.40 ┤                ╭╯                ╰╮            
    0.30 ┤               ╭╯                  ╰╮           
    0.20 ┤              ╭╯                    ╰╮          
    0.10 ┤              │                      │          
    0.00 ┼──────────────╯                      ╰───────── 

    Clouds and weather can cause up to 100% drop in output any time
    Rain will drop your peak output practically down to zero all day
    Dirt will drop total output by a variable amount until cleaned

    1.00 ┼                        ╭───╮                   
    0.90 ┤                     ╭─╮│   ╰╮                  
    0.80 ┤                   ╭─╯ ││    │ ╭╮               
    0.70 ┤                  ╭╯   ││    │ │╰╮              
    0.60 ┤                 ╭╯    ││    │ │ ╰╮             
    0.50 ┤                 │     ││    │ │  │             
    0.40 ┤                ╭╯     ││    ╰─╯  ╰╮            
    0.30 ┤               ╭╯      ││          ╰╮           
    0.20 ┤              ╭╯       ││           ╰╮          
    0.10 ┤              │        ││            │          
    0.00 ┼──────────────╯        ╰╯            ╰───────── 

    Daytime:
      You need up to 100% backup to be available at any time.

    Night:   
      To state the obvious, 100% backup is required.

    Conclusion:
      If you need reliable 100% backup at any point
      during 24 hours, this backup capacity has to be 
      available 24/7/365.

The above is absolutely true.

Regarding the link you provided. I am familiar with this article, which, of course, confirms my point.

Figure 5, which is titled "Maps of electricity system reliabilities under the most reliable solar-wind mix without excess generation or energy storage", puts the US at less than 88%.

This means that, ON AVERAGE, 12% of the time you need 100% backup for the most optimal form of solar and wind combined.

I loudly highlighted ON AVERAGE because it is important to understand this is a problem when dealing with statistics. You cannot apply the average of the average of the average to an entire population. This is known as the tyranny of the averages.

Averages are fantastic to wave hands around and talk about generalities. They do not cover my little town of 300K residents going dark for two hours because the solar system powering it had no backup.

The real numbers, once you start to get closer to local realities, are not represented by these average. The real numbers are much worse.

Solar cannot exist without external backup. Solar and wind cannot exist without external backup. That's the real conversation we have to have.

Somehow people read this to mean that I am saying solar and wind are bad and not usable. That is not AT ALL what I am saying. I am simply highlighting that we cannot "go green" just with these technologies. And it gets much, much worse, when we start to throw in hundreds of millions of electric vehicles. My point, in the aggregate, is that we, in the US, desperately need to change our thinking with regards to nuclear. Otherwise we are going to end-up with a bunch of solar and wind backed-up by massive amounts of power being generated by burning stuff.

    Try again.
    No personal attacks this time.
    Where, exactly, did I lie?
    Show your work.

[Schroedingersat]

Read the article I linked. Then stop posting lies and long-winded demonstrations that you don't understand that weather can be anything other than 100% correlated over a region and is forecastable.

Then note w2e, hydro and other average-energy-limited dispatchable sources exist. A hydro system which can provide 100MW on average can provide 1GW peak. There are a few tens of GW of waste stream methane available in the US alone. It can be stored and burnt at any time to meet unshiftable demand.

Then note that dispatchable loads such as EV charging exist and exceed non-dispatchable ones. They make VRE easier to use, not harder as you claim.

Then note when pools are pumped, water towers are fied, thermal storage in buildings is charged, zinc refineries and so on are run. It's not done in the middle of the night in regions with thermal generation because people just love noise and graveyard shifts.

If you have 1 watt of constant load, 2 watts (average over 6 months) of dispatchable load, 2 net watts of solar (ie. 4 nameplate watts), long distance transmission, 2 net watts of wind, and 1 net watt of hydro and green fuel burnable in an OCGT, then you have plenty of power.

You're willfully ignoring systems and demand shifting and trying to claim only always-on thermal generation works. This is a lie.

Even assuming fossil fuel for the week a year the system has low output, a VRE dominated grid still cheaper and greener than alternatives and you still don't need to run your electrolysers or zinc refineries or arc furnaces or thermal storage heaters. And if you have a day warning the Al smelters can clear the lines too. This is done all the time in systems dominated by thermal generation to meet demand spikes. Claiming these loads need backup instead of being backup is a lie.

You're trying to pretend turning a fossil fuel generator for the non-dispatchable loads on ever eliminates any gains from the whole system just because it has the same power as the un-shiftable peak demand. This is also a lie.

You're trying to pretend that fixed loads are constant, so a power-limited thermal generator would need no storage or overprovision. This is also a lie.

You're trying to pretend weather events where there is zero wind or sun across a large region for over a day are common. This has never happened. This is a lie.

You're trying to pretend thermal generators never go offline in a correlated way so that any correlated downtime is exclusively VRE. This is a lie.

You're trying to pretend building a system that can eliminate 85-95% of emissions in a year or two for a tenth of the price and then startig on the boondoggle which eliminates 90% of emissions and exports the rest to Niger isn't the obvious and objectively correct answer even if your above lies were accurate.

[robomartin]

Wow, you have a consistent need to diminish and insult others. Remarkable.

You continue to resort to insulting me over many threads across many months. Any time there's a thread on a related subject you seem intent in demonstrating your ability to insult me.

I read the article. Of course I did. I read it a couple of years ago, or whenever it was published.

It actually supports my point!

    Solar requires the availability reliable power 
    for up to 100% backup.

That can be batteries, another solar installation a thousand kilometers away, wind, fossil, nuclear, a bunch of people pedaling power-generating bikes. Anything, really.

I am not saying solar or solar + wind are a bad idea, pointless or that we should not use them. Heck, I have made a non-trivial investment in solar myself. And one of the companies I own actually develops related technologies.

Once again, the very article you posted clearly states that the COMBINATION of solar and power in the US is, at best, ~ 88% reliable. Solar alone? Less so.

I can support my claims with actual data from my own solar array. I just visited a six million dollar installation in Singapore. The results are even worse.

Here in So. Cal, we are about to get hit with yet another large storm. All solar power will be reduced to nothing during this time.

I have no clue what your problem is. You are consistent in the use of insults in place of conversation, math and science. Lots of hand-waving. No substance at all. It's exhausting, really, but I am not going to allow you to bully me into discussing this perspective in the context of facts-based discussions.

If I am wrong, I am more than willing to be shown where, why and how. Always. My life and career has been about learning, constantly. That happens with respect and facts, not insults.

   EDIT:

Further to the article you seem to be leaning on. From figure 2, and using Photoshop to identify and match the color scale:

"Shading in each panel represents the 39-year average estimated reliability (% of total annual electricity demand met)"

https://i.imgur.com/9OMK9eZ.png

This shows that 100% solar (without mixing-in wind) in the US only has a reliability (% of demand met) of about 53%.

    Solar requires 100% reliable backup.

If we add 12 hours of storage (also in figure 2 of the article YOU provided):

https://i.imgur.com/ut52ZbI.png

Solar + 12 hours of storage gets up to only 82% reliability (% of demand met). In other words, cities go dark 18% of the time.

    Solar requires 100% reliable backup.

Even with the most optimal configuration (close to 50/50 wind and solar with 12 hours of storage), reliability comes up to about 86%.

    Solar requires 100% reliable backup.

If we overbuild both solar and wind, add 12 hours of storage and shift the mix to about 40% solar and 60% wind, we can get to about 95% of demand met. Solar alone, in this overbuilt scenario, would only be about 88%. So, we overbuild by 50% and only get about 6% better performance.

    Solar requires 100% reliable backup.

And, once again, these are numbers that are presented in terms of averages, which have almost nothing whatsoever to do with local realities. You cannot apply an average figure calculated from multiple averages to an entire country and conclude that those numbers represent local realities.

The fact that you have to use wind and storage to achieve performance above the 53% of demand achievable by solar alone fully supports the point I have been making:

    Solar requires 100% reliable backup.

I am eager to see what new insults you are going to use to divert from the inconvenience of having the article you provided actually support my point at every level. The suspense is truly riveting.