Skip to content

David Mackay Highlighted Problems With Solar Power In 2013

November 16, 2016

By Paul Homewood


h/t Joe Public




Back in 2013, the late David Mackay, at the time the Chief Scientific Advisor to DECC, wrote a paper called “Solar energy in the context of energy use, energy transportation and energy storage”. He went into a lot of detail evaluating solar potential, and his Abstract found that “in a decarbonized world that is renewable-powered, the land area required to maintain today’s British energy consumption would have to be similar to the area of Britain”.


But there is one particular section which caught my eye:


For solar photovoltaics to supply 6 per cent or more of today’s average electricity demand in the UK would involve some technical challenges. The UK’s National Grid (2012, personal communication) has advised me that, if 22 GW of solar capacity (370 W of capacity per person) were attached to today’s grid, then the system would, at some times on some sunny summer days, be unacceptably challenging to control and unacceptably lacking in robustness to a sudden fall in demand: the control of the grid’s frequency relies on having sufficient inertial generators on the system; in its advice to me, National Grid reckoned that 40 per cent of demand at any time should be served by inertial generators, and it assumed that solar and wind generators would contribute no inertia. This constraint could in due course be relaxed if additional inertial services could be supplied (e.g. by wind generators that incorporate energy stores and can therefore synthesize inertial properties) or if control-commands could when necessary be issued to solar generators to instruct them to reduce their output. (Future generation codes in the UK will require solar generators to have the capability to respond to such signals.)


Last year, in comparison, solar supplied just 2% of the UK’s power.

But then he continues:


Let us assume that these technical constraints can be solved. What if solar photovoltaics supplied 11 per cent or more of today’s average electricity demand in the UK? Figure 11 shows the time variation of the output of a simply-modelled fleet of 40 GW of solar panels in the UK (670 W of capacity per person), whose average output (4.4 GW, if we assume a load factor of 0.11) would equal 11 per cent of current electricity demand. The total output is occasionally close to the total electricity demand; at these levels of solar capacity, peaks of solar output would certainly cause electricity supply to be shed, unless our electricity system is enhanced by the addition of (i) large pieces of flexible demand; (ii) large interconnectors to other countries willing to buy excess electricity; or (iii) large-scale energy storage.



Figure 11

Electricity demand in the UK and modelled solar production, assuming 40 GW of solar capacity. (a–c) The upper curves show Britain’s electricity demand, half-hourly, in 2006. The lower data sequence in (a) is a scaled-up rendering of the electricity production of a roof-mounted south-facing 4.3 kW 25 m2 array in Cambridgeshire, UK, in 2006. Its average output, year-round, was 12 kWh per day (0.5 kW). The data have been scaled up to represent, approximately, the output of 40 GW of solar capacity in the UK. The average output, year round, is 4.6 GW. The area of panels would be about 3.8 m2 per person, assuming a population of roughly 60 million. (For comparison, the land area occupied by buildings is 48 m2 per person.) (b,c) The lower curves show, for a summer week and a winter week, the computed output of a national fleet of 40 GW of solar panels, assuming those panels are unshaded and are pitched in equal quantities in each of the following 10 orientations: south-facing roofs with pitch of (1) 0°, (2) 30°, (3) 45°, (4) 52°, and (5) 60°; (6) south-facing wall; and roofs with a pitch of 45° facing (7) southeast, (8) southwest, (9) east and (10) west. On each day, the theoretical clear-sky output of the panels is scaled by a factor of either 1, 0.547, or 0.1, to illustrate sunny, partially sunny, and overcast days. Note that, on a sunny weekend in summer, the instantaneous output near midday comes close to matching the total electricity demand. Thus, if solar photovoltaics is to contribute on average more than 11% of British electricity demand without generation being frequently constrained off, significant developments will be required in demand-side response, large-scale storage, and interconnection.


This is an issue I have raised previously with regard to wind power. In other words, that a large scale build of wind capacity would lead to a lot of surplus electricity on windy days.

What Mackay’s analysis shows is that, without large scale storage, even relatively low roll out of solar and wind capacity will lead to underutilisation of that capacity. This, in turn, will drastically increase the cost of solar and wind power.



The Mackay paper is here.

  1. November 16, 2016 6:45 pm

    Maximum solar output is on bright summer days. Maximum electricity demand is on dark winter evenings. So on average solar power has an inverse relationship with demand.

    Which part of that do solar power advocates not understand?

    • MarkT permalink
      November 20, 2016 3:14 pm

      That is a reasonable conclusion for countries nearer the poles. However for hot countries the max demand is for AC during the day. The close correlation of demand and PV power output means solar makes much more sense in those locations. Such as can be witnessed in Queensland Australia.

  2. Stonyground permalink
    November 16, 2016 7:00 pm

    When it comes to the question of energy storage, I have often wondered if there is any potential in using compressed air. Pneumatic power tools use about 120psi, but I have no idea if there is a practical upper limit for air pressure. The strength of the pressure vessel would be an obvious limiting factor. Presumably the larger the vessel the lower would be the pressure required to store a given amount of energy but the challenges of making the vessel strong enough would be greater. If really high pressures were used there would be a possible danger of explosions if the vessel were to rupture. The vane motors used in pneumatic power tools are very inefficient but piston engines are much better. Steam engine technology from a hundred years ago had reached a surprising level of sophistication when it comes to extracting energy from compressed gas.

    Having said all that, even if you could store it efficiently, I don’t think there is enough wind and sun to power the modern world. It is also possible, or even likely, that deploying wind turbines on every available piece of land and all around every coast line, would have a serious effect on the climate.

    • Graeme No.3 permalink
      November 16, 2016 9:56 pm

      Compressing the air heats it (and making compression harder), while the reverse applies on pressure release. For the necessary efficiency that heat has to be recycled. has one interesting way of overcoming that problem. NOTE that the source is not known for critical analysis of new ideas and the project seems to be below the horizon.

      There are no utility scale plants as of 2015, but a German project ADELE is planning to bring a demonstration plant (360 megawatt hours storage capacity) in to service in 2016. The theoretical efficiency of adiabatic storage approaches 100% with perfect insulation, but in practice round trip efficiency is expected to be 70%. So wind in at 70 cost units becomes 100 out. With wind about 3 times the cost of coal fired I think it would require even higher electricity bills.

  3. Athelstan permalink
    November 16, 2016 7:23 pm

    God gave us solar power storage, it’s called coal.

    I like the idea of desalination through solar PV panels and of course the other ways around luverly sea salt from desiccation – via NATURAL solar power. Otherwise, PV cells arrays are the green loonies taking the piss, boondoggle engineering and massive waste of space particularly: at +50ºN – no ifs nor buts.

  4. Bloke down the pub permalink
    November 16, 2016 7:40 pm

    Interesting that MacKay’s analysis is based on the solar panels being aligned in a range of directions in order to even out the production through the day. Is there any data available to suggest this is the case, or any requirement for large scale installations to vary their alignment. I have solar panels on my house which , for a number of reasons , are split between one system on the front that faces SExE and one on the back facing NWxW. I know of very few other installations that are similarly split and assume that most will face generally to the south, especially those not restricted by the aspect of a roof, such as when built on farmland.The only driving forces are the ease and cost of installation, and maximising the total output. I’m not aware of any requirement to even out the time of day when the energy is produced.

    • November 16, 2016 8:00 pm

      The subsidies are such that it pays to maximise output, by aligning solar panels to face south and at the best angle to the horizontal.

      • Bloke down the pub permalink
        November 17, 2016 2:46 pm

        Which means that the problem with renewable power peaking and excluding conventional generation, and then dropping quickly towards zero, is made even worse.

  5. hotscot permalink
    November 16, 2016 7:55 pm

    Dr. MacKay does a brilliant TED talk on the problems of ‘clean energy’ with nothing more than arithmetic. What a man, a proper humanitarian and environmentalist who recognises the silly practicalities of biofuel, windmills and solar panels.

    Fag packet calculations from a mathematical genius, why can’t all scientists put things like this into terms we can all understand? Or at least me.

  6. November 16, 2016 8:18 pm

    As we know, the Government ignored Prof MacKay’s advice about wind and solar being useless for the UK “then if you ask, what is the optimal amount of wind and solar …… the answer is going to be almost zero”. Governments have instead listened to the idiots from the green blob.

    Here is the latest example of the industry trying to get the Government to go for more wind and solar, contrary to MacKay’s advice about 40GW of solar causing problems. See this lobbying article (paid for by the renewables industry, one of the authors having a masters in Environment and Politics). If the Government follows this advice, we are in deep trouble.

    ‘Plugging the Energy gap’ at

  7. Green Sand permalink
    November 16, 2016 9:16 pm

    There could be other ‘solar’ related issues:-

    “….We find that the average strength of the polar fields near the end of Cycle 24 will be similar to that measured near the end of Cycle 23, indicating that Cycle 25 will be similar in strength to the current cycle…..”

    ‘Predicting the Amplitude and Hemispheric Asymmetry of Solar Cycle 25 with Surface Flux Transport’

    David H Hathaway, Lisa A Upton

    Accepted manuscript online: 14 November 2016

  8. Francis Bowkett permalink
    November 16, 2016 10:07 pm

    Paul, to your point about excess electricity being supplied by wind turbines on windy days, see the blog at the following link for a very recent example of this, including an analysis of what it is costing the consumers in the province of Ontario.

  9. Tony Price permalink
    November 16, 2016 11:10 pm


    Solar: most power when you least need it
    Wind: least power when you most need it

    BTW – in his book “Sustainable Energy — without the hot air”, Mackay makes a horrendous booboo in the section on solar power. He calculates the realistic average insolation, taking into account latitude and varying angle of insolation through the day; conversion factors for hot-water and photo-voltaic systems to get kW per daylight hour, and then multiplies by 24 to get the daily figures. Oops! This means he over-estimates production by around 100%, and underestimates total area needed by 50%.

    The book is available for download at

    He doesn’t make the same mistake in the linked paper above.

  10. Athelstan permalink
    November 17, 2016 1:05 am

    “photo-voltaic systems to get kW per daylight hour, and then multiplies by 24 to get the daily figures. Oops!”

    Ooops again.

    The problem I have with all of the calculations and in this I do salute Mr. David Mackay, for he seems like a ‘conscientious’ fellow and in today’s world that commodity is as rare as hens teeth.
    Back to my problem, bird mincers, solar panels, load factors, inertia rations, and all dependent on natural factors, we can talk useless statistics until the cows have come home and had a 15 year sabbatical, the basic truth remains does it not?

    That basic truth, the mere fact that if, if you were starting from scratch and there was cold logic ONLY applied. Then, if a country required copious amounts of the cheapest electricity available and notwithstanding the hardships, vicissitudes of sourcing, digging it up, transportation and burning it, to generate steam to turn turbines………….

    Then, any sane man/engineer would choose King Coal and surely is it not a fact that, that’s just the choice we [once] made and today China and India do.

    An aside.

    wanna get twisted? then lets twist baby! and here, the truth, gets a very severe twisting.

    Interesting that, and here we go with generation snowflake, the very people who dance away from the reality of life and stick their fingers in their ears to all sorts ie; making a living in the hard, harsh, big wide world. Yes that libtard lot, have coined a new phrase ‘post truth’.

    “Post truth”!? is, a safe space?

    indeed? it is a mind boggling journey delving into the slop bucket of liberal sophistry, misdirection and feint.

    Welcome to the Legerdemain of the left, where the movers and shakers in this group-think of delusion, deem anyone who is not a coreligionist as ‘the outsiders’ yer know – are the analysts and truth tellers BUT now, telling it like it is, are now referred as, bracketed in a collective phraseology to be called, “post truth”.
    It is, another vast leap of imagination to bring ourselves [shall I call we/us the realists?]… also make some quite crazy assumptions.

    TPTB ordain it.

    To be made to infer thus, that all which went before ie from year zero circa 1964 [civil rights act?]Britain is forced into the EU…..[‘common market’ as it was then sold]….1988 Hansen, thru’ the Clinton terror in the mid Nineties onto blair, brown, camoron to 2016……. All inclusive of; the nebulous duplicity its gossamer weave of Cultural Marxism and its poisonous spiders spinning the dogmas of Multiculturalism, Agenda21, post modern ejukayshun, was somehow credited to be [no less!] the received wisdom of the times and gospel according to the Frankfurt school and Goldman Sachs er… no! not at all…………………

    and now supporters of Brexit and ‘The Donald’ are running away from the received truth ie we voted for anti Socialist policies and against the Internationalist doctrines [how could we?] – makes us ‘post truth-ers’……..

    Can you get your head around this sort of “post truth” its ceaseless historical rewrites and discombobulation of casuistry?

    I wonder what grounded historians will record, with hindsight looking back at those years during the sequential decades of 1950 to 2016; imho in synopsis, it will allude to, ‘when the west collectively lost its fucking marbles”.

    • November 17, 2016 4:34 am

      Yes – I find it totally amazing. The Scottish government claims, quite simply, that they can achieve “100% renewables by 2050”. Impossible without massive backup generation, yet no-one in the opposition parties or the press points out to them that it IS impossible, and why, they just argue about the details. The “Renewables” lobby witter on about battery backup, when the entire annual world production of lithium cells would be required for just a few minutes of UK peak load. They talk about “pumped hydro” to store excess peak power, which needs two large lakes one above the other. There are only a few possible sites in the UK, and existing PH is only capable of ironing out peaks in demand. “Greenies” would be quite happy to see all our pristine uplands covered in white whirling bird and bat choppers, yet fight tooth and nail against high-voltage power lines for conventional power. Power lines that would be essential to transfer power from remote wind and/or wave generation sites that they promote. It’s a form of collective madness. The “Emperor’s new clothes” writ large.

      • Bloke down the pub permalink
        November 17, 2016 2:52 pm

        Sturgeon aims to achieve 100% renewables by the expedient of shutting down the whole of the Scottish economy, simples.

      • saxonboy permalink
        November 20, 2016 6:41 pm

        Bloke is right, Windmills fit the Green narrative of ‘Saving’ the planet ( but not us incidentally ), this is Degrowth by stealth, the Cultural Marxists Utopian Orwellian economic nightmare may not be that far away. The Anticapitalist mob have the EU at their command. Trump and Brexit are hurdles that they will do anything to remove..interesting indeed. The biggest mistake successive UK govt’s have made is to completely underestimate the Green maniacs and their ilk. Turbines vs Trident here..

  11. November 17, 2016 8:27 am

    Solar panels have a finite life. What are the costs, financial and environmental, of removal and disposal? What are the costs of returning the site to its origonal state?

    • November 17, 2016 11:42 am

      If you time it right then the lifespan of a solar panel or a wind turbine is until about 24 hours after you go into liquidation. So you don’t really care about about any “decommissioning” costs. And it’s not the local council’s land so it’s not (initially at least) their problem.

      Where I used to live, the sites of two former paper mills lay derelict (and contaminated) for the best part of two decades before developers decided to build houses on them. Nobody is going to (a) be interested, or (b) be given consent for housing development on the site of the nearest wind farm (I can’t comment on solar ‘farms’ but I assume the issues will be similar) without considerable investment in infrastructure, and probably not even then at an altitude of about 300 metres and five miles from the nearest habitation!

      Still less is anyone going to build on or have any interest in doing anything with the majority of renewable energy installations simply because they are even more remote.

      Over the next 25 years renewable energy installations will reach the end of their natural lives and fall gently into decay and dereliction because no-one will be interested in replacing them. They will be left as monuments to the outstanding episode of collective idiocy that marked the latter years of the 20th century and the first two decades of the 21st.

      • Russ Wood permalink
        November 18, 2016 4:36 pm

        There are rusting pylons in Palm Springs and Hawaii to testify to that!

      • November 18, 2016 5:44 pm

        There are indeed many older, low-power turbines rusting away around the world. Here’s a wind-geek who says he’ll demonstrate the “myth” of many abandoned, rusting turbines. In a nutshell, and paraphrasing what he actually writes, he says that claimed numbers are effectively “pulled out of thin air”. Then he goes on to pull his “myth-busting” figure out of thin air too! He claims, and without any evidence or justification, that 1% of the total of 240,000 is more realistic. He says “According to the Global Wind Energy Council (GWEC), there are just under 240,000 working wind turbines as of Q1 2013.” yeah – WORKING TURBINES. That figure, by definition, doesn’t include any abandoned, rusting turbines!

        Read it and weep, or LOL as I did.

    • Gerry, England permalink
      November 17, 2016 1:54 pm

      Anecdotal evidence says that the Little Ice Age will be instances of huge hailstones – in fact there have been a number of megahail storms in the last year or two devastating crops. I did email one of the solar panel peddlers what impact tests have been carried out. No reply of course. I can’t see how hailstones that smash car windscreens and dent bodywork is not going to make a mess of solar panels. We could see hailstones the size of small rocks.

      • November 17, 2016 2:40 pm

        I recall going to Munich about 1985 and seeing car roofs dented with lots of pockmarks about 1cm deep. Also many houses with tarpaulians over them due to cracked tiles – hail is a real risk

  12. tom0mason permalink
    November 18, 2016 5:44 am

    I notice that David Mackay says nothing about the huge environmental damage these structure exact during their manufacture and over their relatively short life. Miners with silicosis, toxic chemicals used etc.
    Who foots the bill for clearing-up these useless blots on the landscape when the time comes?

    Green problems of solar cell.
    Umm Cadmium what’s to like about it? …

Comments are closed.

%d bloggers like this: