South Africa's rooftop solar explosion

mpdjhb said:
Although most people are asleep at 4am.
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Fine, call it 6pm then.

Solar is expensive anytime the sun's not shining. It's our storage capacity that's more directly comparable with Eskom's dispatchable peaking capacity of ~5 MW, nevermind baseload. So we need to measure it.

I'm all for cheaper solar but the distortion gets worse as prices drop on solar faster than batteries, because there is an incentive to overload roofs with panels relative to storage, and to just dump the excess for the time being. This makes the midday contribution larger but it also makes the "duck curve" steeper.

It's fast becoming a no-brainer to install solar PV just for water heating, with no battery or inverter component. If Eskom sees this as MW offset from the grid it will be technically correct to some extent but increasingly misleading.
 
Tomtomtom said:
Fine, call it 6pm then.

Solar is expensive anytime the sun's not shining. It's our storage capacity that's more directly comparable with Eskom's dispatchable peaking capacity of ~5 MW, nevermind baseload. So we need to measure it.

I'm all for cheaper solar but the distortion gets worse as prices drop on solar faster than batteries, because there is an incentive to overload roofs with panels relative to storage, and to just dump the excess for the time being. This makes the midday contribution larger but it also makes the "duck curve" steeper.

It's fast becoming a no-brainer to install solar PV just for water heating, with no battery or inverter component. If Eskom sees this as MW offset from the grid it will be technically correct to some extent but increasingly misleading.
Click to expand...
Yeah those that keep saying that solar rooftop installs is helping don't really look at the fact that from 5pm to 5am there is no sun and either people switch back to grid or rely on battery and switch back to grid later.
Also most solar installs don't have big ticket items on solar like water heating and cooking.
Plus residential usage was only 19% of all demand anyway, so residential demand was only ever 5 to 8GW anyway
 
Lupus said:
Yeah those that keep saying that solar rooftop installs is helping don't really look at the fact that from 5pm to 5am there is no sun and either people switch back to grid or rely on battery and switch back to grid later.
Also most solar installs don't have big ticket items on solar like water heating and cooking.
Plus residential usage was only 19% of all demand anyway, so residential demand was only ever 5 to 8GW anyway
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Maybe so, but specifically during the peak demand period from 17:00 - 19:00 they're mostly running off battery. That's because it's the most critical slot during LS, and nobody would have bothered to change their settings in case LS returns at any point.

Also a lot of people have caught onto the fact that water heating should be done during the day, irrespective of whether it's on essentials or not...
 
Lupus said:
Yeah those that keep saying that solar rooftop installs is helping don't really look at the fact that from 5pm to 5am there is no sun and either people switch back to grid or rely on battery and switch back to grid later.
Also most solar installs don't have big ticket items on solar like water heating and cooking.
Plus residential usage was only 19% of all demand anyway, so residential demand was only ever 5 to 8GW anyway
Click to expand...

Yep, it’s all about flattening the duck curve. Here’s the California example which perfectly highlights the issues.

IMG_3649.jpeg
 
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Lupus said:
Yeah those that keep saying that solar rooftop installs is helping don't really look at the fact that from 5pm to 5am there is no sun and either people switch back to grid or rely on battery and switch back to grid later.
Also most solar installs don't have big ticket items on solar like water heating and cooking.
Plus residential usage was only 19% of all demand anyway, so residential demand was only ever 5 to 8GW anyway
Click to expand...

Most of those solar installs come with batteries so @ 6pm people are generally running their batteries that have been charged up. From my personal experience im only really drawing from the grid late at night/early in the morning when general demand is low.
 
KikzAzz said:
Oh, I thought it was the loadshedding and unreliability of Escom
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As much as I'd love to give them the credit, 99.9% of solar installations wouldn't have been possible at 2008 pricing.

Would there have been less solar around without loadshedding: sure. But at current PV pricing, you will save in the long run even without Eskom and loadshedding.
 
G.A.S said:
Big difference between California and here though: Most PV in SA is backed by batteries due to loadshedding.
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Sure, but the visual gives a good idea of the problem for the grid in general. Huge ramp up needed early evening when the sun goes down.
 
Lupus said:
Yeah those that keep saying that solar rooftop installs is helping don't really look at the fact that from 5pm to 5am there is no sun and either people switch back to grid or rely on battery and switch back to grid later.
Also most solar installs don't have big ticket items on solar like water heating and cooking.
Plus residential usage was only 19% of all demand anyway, so residential demand was only ever 5 to 8GW anyway
Click to expand...

Easy to say something - but facts matter. My usage yesterday shows I had almost no grid usage and contributed nothing to the "grid demand" at peak time.
I can do the same for any day over the last 2 years with very similar patterns.

1713442161436.png
 
Unhappy438 said:
Most of those solar installs come with batteries so @ 6pm people are generally running their batteries that have been charged up. From my personal experience im only really drawing from the grid late at night/early in the morning when general demand is low.
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Sure, but it's not 5GW worth :-) that would be 70% of all residential users.
 
G.A.S said:
Big difference between California and here though: Most PV in SA is backed by batteries due to loadshedding.
Click to expand...
They are, but how many of those batteries actually can last the whole night?
 
mpdjhb said:
Easy to say something - but facts matter. My usage yesterday shows I had almost no grid usage and contributed nothing to the "grid demand" at peak time.
I can do the same for any day over the last 2 years with very similar patterns.

View attachment 1693441
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I too have solar and batteries and have designed it so I use very little from the grid, but there have been times where I have pulled from it, plus how many solar installs out there have sufficient batteries to do so? Also do you really thing 70% of all residential electricity has gone solar?
 
Lupus said:
They are, but how many of those batteries actually can last the whole night?
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We're not talking whole night, we're talking peak demand which is what the duck curve speaks to.

Most people have no issue running off grid later in the evening when demand drops. Their batteries are more important during peak periods, not when they're asleep...
 
Mike Hoxbig said:
We're not talking whole night, we're talking peak demand which is what the duck curve speaks to.

Most people have no issue running off grid later in the evening when demand drops. Their batteries are more important during peak periods, not when they're asleep...
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But are they also still running at batteries on the first peak of the day :), plus you're telling me that almost 70% of residential users are using solar?
 
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