A Fifth Is Fine For Scotch, Power Generation Not So Much

Interesting graph and story over at Tallblokes place:


UK Wind & Solar Power Nameplate vs Actual

UK Wind & Solar Power Nameplate vs Actual


This post is concerned with the two main forms of UK Weather Dependent Renewable Energy in the UK, Wind Power, (Onshore and Offshore), and on grid Photovoltaic Solar Power. In the UK these amount to ~75% of all installed Weather Dependent Renewable Energy. The other Renewable energy inputs are traditional Hydro power ~8% and the remainder are other sources such as biomass, waste and landfill gas amounting to ~17%.

The capacity percentage, or load factor, of any power generating installation is calculated as the actual electrical output achieved annually divided by the nominal maximum Nameplate output. This article uses the real measures of capacity reported in up to date time series data of UK Renewable installations. It thus provides reasonably correct comparisons of the efficacy of Weather Dependent Renewables as is reported annually by the Renewable Energy Foundation in the UK.

When announcements are made about Weather Dependent Renewable Energy installations, they are reported as the full Name Plate capacity usually in Megawatts and also often disingenuously as the number of homes that could be supplied at their full level of power output. So such announcements are always over optimistic because the question of Capacity Percentages / Load Factors are not fully explained. So Renewable Energy announcements usually assume erroneously that the wind blows all the time at a productive speed and that the sun shines overhead 24 hours /day.

But because Weather Dependent Renewable Energy output is crucially dependent on the vagaries of the weather, (for wind), and the weather in combination with the season and the time of day, (for solar), the useful electrical output achieved by Weather Dependent Renewables is inevitably substantially less that the maximal Name Plate capacity of the installation. Accordingly in 2017 Weather Dependent Renewable Energy in the UK was operating at about one fifth of nominal name plate capacity overall.

Lots more in the story. Hit the link…

It is interesting how 1/5 keeps showing up. At about 20%, or 1/5, of your grid power coming from “Unreliables”, the grid starts to destabilize in uncontrollable ways. Now this says you get about 1/5 of nameplate power out of the systems. Put those together it says you need to install about 100% of exiting nameplate power as Unreliables to get just 1/5 of your needed power, but at that time you also will have an entirely unstable power distribution grid.

Why become apparent when you think a moment…

On a good day, at high noon with wind blowing: 100% of your power comes from solar and wind as nameplate Unreliables make it all.


At any moment the wind can stop or cloud blow in (or just guaranteed the sun will set) and you can get 0% from Unreliables.

Unfortunately, power plants that are really really good at making cheap baseload power (coal and nuclear) can have start-up times measured in a day or two. Not really suited to rapid “load following” (or in this case “lack of power from Unreliables following”)

So you get rapid swings of production that can’t be made up by the best baseload production capacity. Even gas turbines need a bit of time to warm up and spin up, so even with a 100% replacement of all coal and nuclear with gas turbines (and you WILL need a 100% backup to the Unreliables nameplate capacity because the wind WILL stop at night some times) there will still be grid instability as the wind can stop faster than cold turbines can start.

Subscribe to feed


About E.M.Smith

A technical managerial sort interested in things from Stonehenge to computer science. My present "hot buttons' are the mythology of Climate Change and ancient metrology; but things change...
This entry was posted in Economics - Trading - and Money, Energy and tagged , , , , , , , , . Bookmark the permalink.

10 Responses to A Fifth Is Fine For Scotch, Power Generation Not So Much

  1. philjourdan says:

    To paraphrase Jack Crabb

    “Sometimes the grass don’t grow, the wind don’t blow, and the sky is not blue. “

    Indians knew that 200 years ago.

  2. nzrobin says:

    Some more detailed thoughts about power system stability. http://www.kiwithinker.com/category/power-system-stability/

  3. p.g.sharrow says:

    Every Kilowatt of usable “renewable green” electricity must be matched with a Kilowatt of dependable backup supply. No matter how “free” wind and solar are, they are a sometime thing, there is no free lunch. Someone has to fund that backup. Without government mandates and subsidies there is little or no Return On Investment in them.
    Even Obama knew this when he bragged that he would drive cheap coal from electric generation and the cost of Electrical Power would necessarily skyrocket. Our Californian Governor learned this nearly 40 years ago during his first governorship and still, again he is destroying the grid and cost structure of electric power. This is the face of a true liberal idiot-a-log or is a deliberate destruction of modern civilization…pg

  4. E.M.Smith says:


    Yeah… I find I’m re-starting the behaviours from the Gov. Gray “out” Davis years. Not so much from power fails (though those have increased with one killing my internet router a few days ago) as from price rises.

    I’m now making “incidentals” on the camp stove in the kitchen again. Though this time it’s the alcohol stove (so far). Tonight even made dinner on it (and this morning made breakfast). So for today, in fact, I’ve not powered up a single electric burner on the stove… Not from spite, but mostly because its very convenient, more fun, and a little bit cheaper.

    I made a 6 quart pan of water boil nicely with it, and then pasta / sauce for the main course. (Bought packaged ravioli to try… I’ve made them by hand and it’s a pain…). Breakfast was a ham omelette. Then coffee and tea along the way. All up I think it was maybe 2 ounces of fuel?

    So now I’m stocking a bit of fuel for cooking, again. And getting my UPSs back in order, again. And thinking about doing a tune up on my generator to make sure it’s ready to go, again.

    Bit by bit Herr Brown is driving me from the grid… again.

  5. p.g.sharrow says:

    Guess I should tune up my generators as well. Back in the Greyout Davis days we were on the same circuit as the local fire station so immune to the rolling blackouts. Now we are blessed with “smart meters” so I don’t know how we might fare.

    Pumping Water for irrigation is our biggest concern here, but we now have a 1500 gallon service tank for the gardens, but rolling black outs will cause us to peg the meter and incur the maximum service rate for that month.

    Back in the previous Brown crash days we had to install delay clocks on all the refrigeration equipment so they wouldn’t all power up at the same time upon power return.

    I think the power company, PP&E, considered it a billing feature, every month they would turn the power in town off for a half hour. then flip it on to spike the meter demand rate..The farmers outside of town were on REA and did not suffer the outages. They both fed off of the same high tension supply lines. I’m sure PG&E will use the same game if they can…pg

  6. E.M.Smith says:

    Gee, hadn’t considered that… Then again, as I’d hop onto the UPSs and generator, then on power return didn’t have a surge as things were, one at a time, moved back to wall power, nothing would have told me about it…

  7. oldbrew says:

    Another problem is renewables over-supply, leading to power-dumping, negative pricing etc.

  8. Tom says:

    An electrical engineer once dabbled in Magnetic Levitation design applications in the 80’s. One latter project examined kinetic storage of energy in a ribbon of iron following an oval magnetized racetrack; which, through appropriate choices avoided some of the pitfalls and limitations of flywheel storage. He suggested the most practical test would be as a peaking unit, considering the sale of spot electricity would best service construction debt.

    Bidirectional conversion of electrickinetic was about 98% efficient. With a large capacity device designated as an emergency reserve, the parasitic losses were low at stand-by, such that tapping in to the kinetic storage for electricity to maintain ribbon levitation, allowed a majority of the initial energy to remain available after many years elapsed with no input source.

    This concept has not been tested at significant scale AFAIK. The most similar concept of kinetic storage uses rail-car like modules operated on an inclined track, which functionally mimics pumped hydro storage.

  9. Steve C says:

    Interesting to see the (approximate) fifth turning up again – I come across it all the time messing about with radio. If you want a 50 ohm tap onto a tuned circuit, start 1/5 up from the cold end. If you want to couple to a “magloop” antenna (literally, one big, fat turn with a tuning capacitor in it), you need a coupling loop a fifth the diameter. I suspect the ‘one fifth sweet spot’ is the real world’s answer to the pure mathematicians’ pi, e and so on!

    Point very much taken on baseload stations, too. Our local is Ratcliffe-on-Soar, a thoroughly modern, efficient coal plant now sadly being wrecked by green nonsense. The station’s claim to baseload status can be gauged by the fact that, in 2009, its ‘Unit A’ (500MW) became the first such generator in the UK to run continuously for 250,000 hours. And not at 20%!

Comments are closed.