Solar Power - a Growing Problem

What to do about too much ‘free’ energy

Summary

The huge surge of Solar power injected into the GB grid every 24 hours in summer makes curtailment more likely and hence increases costs to consumers.

Therefore any new Solar facility should be designed as a system required to produce steady power output throughout each 24 hours. Unless it produces consistent smoothed power it should not receive consent / funding.

As battery technology is improved, battery capacity should be added to existing Solar facilities to smooth their outputs.

Same Basis as Previously

As I explained in my 23 December post, I am now applying adjustment factors¹ to the wind and solar PV power data as recorded by Gridwatch. I continue to use the same units: mega-watts (MW) for power flows and mega-watt hours (MWh) for quantities of energy. Supply must balance demand² every minute of every day (i.e. 60/24/365)

20 April 2023 – a ‘good’ solar day in Great Britain

The latest Digest of United Kingdom Energy Statistics (DUKES) published mid-2022 stated that the total installed *capacity*³ of Solar PV is 13,965 MW. From that fleet (plus recent additions), the power generated - as estimated by Sheffield University and reported by Gridwatch - on 20 April 2023 is plotted below.

GB Solar adjustment factor 1.1689 applied

It was a lovely sunny day across the GB fleet of solar panels, giving rise to a peak power generation rate (MWp) of 10,716 MW. That’s a surge of 10.7 GW that rose then fell back to zero in about 13 hours. Which the GB grid infrastructure, dispatchable power generators, interconnectors, etc. just had to suck up and cope.

Peak solar power occurred at 13:00 on 20/04/23. At that time, Demand was 22,170 MW. In other words, solar briefly satisfied nearly half of GB demand.

Depending on how hard the wind was blowing, that may have resulted in curtailment of excess wind. (Is that how it works, does Solar power get first refusal? DKDC.)

You don’t have to extrapolate this situation too far before you are curtailing more and more of this ‘free’ power. Which currently costs us a lot.

Drax Global’s assessment of the curtailment costs to GB bill-payers, 2020 & 2021

What was the total quantity of Solar electricity accumulated on 20th April? Add them all up and you get 79,151 MWh. Averaged over 24 hours, on that sunny day GB Solar PV was 3,298 MW. (Instantaneous load factor 3,298 MW / 13,965 MW = 23.6%)

Now what *could* the situation have been had our ‘leaders’ had the foresight to insist on performance criteria for Solar PV facilities. Not just “You’ll get what you get in the daytime and zero at night and the rest of the grid will just have to cope somehow”. Instead, “It must produce steady power output throughout each 24 hours and not overload either local or wide-area grid.”

Then GB would already have enormous energy storage to damp down the massive power spikes from Solar:

When solar is high enough it supplies the 24-hour-average power direct to consumers and charges storage with surplus; then when the sun goes down the storage discharges to maintain the same 24-hour-average power to consumers.

Cumulatively for the whole of GB this looks like this:

Whole of GB with buffer storage to maintain continuous Solar-derived power to consumers.

Scaling the above whole-of-GB numbers to a new 100 MWp Solar facility:

The power supplied to consumers is kept constant over each 24-hour period.
The grid loads and variability are greatly reduced.
Overall curtailment would be reduced.
Improvements in battery technology⁴ would be stimulated.

Of course, this doesn’t address Wind’s variability or intermittency. But Wind is far more variable over much longer timescales. Solar power is inherently up and down every 24 hours, hence is ‘easier’ to smooth.

Conclusions

Better performance criteria are required for Solar PV facilities. Any new Solar facility should be designed as a system required to produce steady power output throughout each 24 hours. Unless it produces consistent smoothed power it should not receive consent / funding.

As battery technology is improved, battery capacity should be added to existing Solar facilities to smooth their outputs.

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Disclaimer: Opinions expressed are solely my own.

This material is not peer-reviewed. This is why I’ve stopped believing it would do any good anyway.

I am against #GroupThink.

Your feedback via polite factual comments / reasoned arguments welcome.

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1. I called them ‘correction factors’ in my 23 Dec ‘22 post, but considering that Gridwatch data is not fully reconciled - nor claims to be - I think ‘adjustment factors’ is a fairer description.

Gridwatch records a set of GB power flows every 5 minutes. Hence to a close-enough approximation GB energy quantity (MWh) is obtained by multiplying each power flow (MW) by 5/60 (h). Add all the MWhs together and you get energy per day, per month, per year, etc.

2. With any power grid, supply must equal demand every minute of every day (i.e. 60/24/365) otherwise the power grid operator will have to take action to keep the grid balanced. That action can take the form of disconnecting demand in the area of a supply shortage (for example the GB power system disruption on 9 August 2019) or of curtailing generation in the area of over-supply. Either is expensive. Taken to an extreme, systemic shortfall generation results in the regime known as loadshedding in South Africa - routine even in the capital Johannesburg.

3. I put *capacity* of renewable sources within asterisks to remind readers that the measured actual ‘load factors’ of GB’s entire fleets of wind and solar PV through the last five years are small to moderate percentages of the nominal numbers, per DUKES 6.3

4. Maybe these guys are on to something: “Why Rust Is the Future of Very Cheap Batteries”