I think this hinges on the details of the calculation behind capacity factor.
Capacity factor is the ratio of total energy output to theoretical max power * time.
If the “time” part of that equation includes night time (aka the null values flanking this data), then that would dramatically depress the ratio for solar, since there are long periods of zero generation.
And that might be your point. I mean, that’s not irrelevant to point out for grid-level infrastructure. Solar doesn’t produce anywhere near its max theoretical power because well over half the time conditions are not ideal.
Yes, that's the standard method through which capacity factor is calculated.
If I wanted to make capacity factor look better for solar, I would calculate it by dividing total energy output by the total theoretical power adjusted for time of day * daylight time.
In other words, this adjusted capacity factor would represent the ratio of how much energy is being captured vs. how much power could theoretically be output during every hour of daylight.
I’m not saying this is the correct way to do it, just posing it as a mental model.
Anyway, my 25% figure was peak efficiency, which is different.
Playing with the calculation of course eliminates the ability to compare it with other sources. Solar is a good summer peaking resource, as, at moderate levels of penetration, its output profile aligns well with peak periods historically filled by gas plants, particularly when paired with moderate levels of storage to cover the ramps. The problem is that winter peaks do not occur during these periods, so, as a winter resource, it does not provide the same value, which, combined with much lower output, creates an energy availability issue.
Efficiency and output are of course very different things. On a clear day during the winter, it's quite easy to hit peak efficiency, but output is going to be considerably lower because of the reduced hours of production, which your graphs below also show. Unfortunately, at least up here, snow cover and a lack of clear skies make those periods reasonably infrequent, which you can see in the graph I provided.
Going back to capacity factor for a moment, CF's for solar in the low-to-mid 20's are also quite common for us here, in the summer months, that's why I specifically brought up the winter period, which presents a very different slate of challenges.
Photosynthesis is only about 1-5% efficient, so the fact modern N-type bifacial panels are reaching into the 25% range is impressive, at least to me.
Here’s Jan-Mar data for a mixed vertical bifacial and south facing angled N-type array on a property I own in the north-central US. It is making roughly a third of what it makes in the summer… so I’m sure the capacity factor is garbage. But still, the net energy it is producing is not nothing, especially considering this is a residential property level install. Even the lowest month, December, produced enough energy for a Mach E to drive 400 miles.
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I was more addressing your point on self-sufficiency and claim that this could be mostly achieved by solar being placed elsewhere on a property, not just a roof. And that the market would ultimately "sort this out" when compared to competing sources. The 114kWh you posted above for the month of December wouldn't even touch my energy consumption for that month:
let alone provide some level of self sustenance.
The push to electrify things exasperates the issue (I have a hybrid HVAC system that uses a heat pump for temps warmer than about -8C) as heating demand is highest during the hours that solar isn't producing.
I'm not anti solar by any stretch, but we have to be realistic about its abilities; about its strengths and weaknesses as a source.
