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Can photo voltaic and wind energy Britain? An replace of David MacKay’s numbers

Can photo voltaic and wind energy Britain? An replace of David MacKay’s numbers

2023-11-05 08:33:34

This Substack was impressed by the work of Sir David MacKay. I wrote about this on the weblog’s About page.

Debates round local weather, vitality and sustainability are sometimes charged with emotion. That’s fantastic. However we additionally have to put the numbers on these issues. 

That is what David MacKay did for vitality: in his e-book ‘Sustainable vitality – with out the recent air’ [which is online for free] he used back-of-the-envelope engineering and maths to work out if Britain might energy itself from renewables. His reply in 2008 was, sadly, no. Removed from it. In his closing interview – he sadly handed away from most cancers – he stated the “concept that renewable vitality can energy the UK is an appalling delusion”. It ought to concentrate on nuclear and carbon seize and storage as an alternative.

However the world has modified loads since 2008. Prices have plummeted within the final decade. New wind designs have come on-line. And public assist for local weather motion and clear vitality has shifted.

David’s method continues to be invaluable, however his numbers are out-of-date. This sector is shifting rapidly, and we are able to’t use analyses from 2008 to information coverage selections.

I’ve all the time needed to do an replace, however fortunately another person did the arduous work for me. Final month, Brian O’Callaghan and colleagues from the College of Oxford published a policy paper wanting on the potential for photo voltaic and wind to satisfy Nice Britain’s vitality wants. Right here’s their summary.

Removed from being an “appaling delusion” they assume that its “wind and photo voltaic sources are greater than ample to satisfy all its vitality wants, each virtually and economically”.

On this put up I’m going to work by their numbers, and the way they examine to MacKay’s.

I’ll attempt to clarify clearly the place their numbers come from to be able to choose them aside for your self. I believe it’s vital that we get some strong numbers as a result of it actually does have an effect on coverage selections and public perceptions. I’d have an interest to listen to your strongest criticisms of the paper.

Let’s begin with the headline results from O’Callaghan et al. (2023).

They estimate that it might produce 2,895 TWh of electrical energy annually from photo voltaic and wind. That’s nearly double its estimate for closing vitality demand in 2050. See the chart under.

Each of those numbers are stated to be conservative (the provision quantity is conservatively low, and the demand quantity is excessive).

We will see this after we take a look at different estimates of vitality demand from the literature. The Nationwide Grid FES initiatives that Britain will want simply 900 TWh in 2050. The UK’s Division for Industrial Technique says 1250 TWh.

Whole closing vitality demand immediately is 1599 TWh. We’d anticipate this to fall with the vitality transition as a result of electrification and decarbonisation result in massive effectivity beneficial properties.

O’Callaghan says that their 1500 TWh demand determine – which is principally unchanged from immediately – is conservative. It will depart room for brand new demand for the manufacturing of cultivated meats, direct air seize, or intensive manufacturing. I additionally assume it’s vital to go away room for hydrogen manufacturing for industries that may’t be electrified. Inexperienced hydrogen manufacturing wants low-carbon electrical energy: it’s simply not the ultimate product.

In any case, they assume that Britain might produce greater than sufficient photo voltaic and wind to satisfy this demand.

This wouldn’t come without cost. We’d want land (and a few ocean) to do it. How a lot?

The abstract of those sources is within the desk under.

They assume there’s a massive potential for offshore wind. This may be unfold over 10% of the UK’s unique financial zone. Onshore wind could possibly be used on 5% of British lands, and mixed with farmland. 2% of British land can be used for photo voltaic PV, and is also mixed with farmland utilizing a way known as ‘agrivoltaics’. Rooftop photo voltaic doesn’t add a lot – the output is kind of small, even when 8% of British rooftops are coated. Undoubtedly nonetheless an excellent possibility for people, however perhaps not for the nation as an entire.

You would possibly assume a few of these necessities are too optimistic. That’s fantastic: you possibly can rapidly alter the numbers to one thing extra affordable. For those who assume the general public would solely settle for 1% getting used for photo voltaic, half the 544 TWh to 272 TWh. For those who assume solely 4% of the UK’s unique financial zone can be usable for floating offshore wind, half the output to round 800 TWh.

Above, our provide was double our 2050 demand, so you might technically half each quantity on this desk and photo voltaic and wind would nonetheless be ample.

Later I’ll undergo every of the applied sciences one-by-one to elucidate O’Callaghan et al.’s assumptions, and the way they differ from MacKay’s. However let’s first examine the massive image.

MacKay calculated figures for Britain’s ‘technical’ useful resource. He then calculated its ‘sensible’ useful resource as soon as prices and public acceptability have been taken under consideration. That is really the place the principle supply of distinction comes from.

His stack of sources (which incorporates different renewables, not simply photo voltaic and wind) was near assembly demand (which was too excessive, as I’ll clarify later). That is on the left.

However he concluded that the majority of it was virtually unfeasible. Photo voltaic PV was eliminated for being too costly. Nobody would settle for a wind farm close to them. Britain couldn’t have offshore wind as a consequence of considerations about birds. I believe these have been affordable presumptions on the time (though the way in which he determined to chop them was a bit “hand wavy”). Photo voltaic PV was costly in 2008. And there was not the general public assist for renewables that there’s immediately.

Ultimately, he concluded that Britain might deploy simply one-seventh of its technical sources.

Right here’s the comparability to the current replace. MacKay’s technical useful resource is similar to what O’Callaghan thinks is sensible.

And right here’s the comparability of various sources. O’Callaghan et al. (2023) assume that floating offshore wind is now possible, in order that’s a lot larger. However MacKay’s technical sources for each different supply are greater.

What has modified, then, since MacKay’s e-book in 2008?

  1. Power demand might be a lot decrease. MacKay primarily used major vitality demand – which incorporates all the inefficiencies that might disappear with electrification and thermal inefficiencies from burning fossil fuels.

    By my calculations, his ‘demand’ stack totalled as much as 2700 TWh for the UK (round 2600 TWh for Nice Britain). That’s 2 to 2.5-times the anticipated demand for 2050. Power demand within the UK has already fallen by round one-quarter since 2008, and that’s earlier than mass electrification.

    Later within the e-book he does take a look at consumption situations in 2050: these add as much as round 1700 TWh of vitality demand.

  2. Photo voltaic and wind prices have plummeted. Within the final decade the price of solar energy has fallen by round 90%, and wind by 70%. They’ve gone from being very costly to being low cost.

    These applied sciences usually are not simply cheaper, they’re higher. Photo voltaic panels are extra environment friendly, and larger and simpler generators have been developed.

  3. Assist for renewables is larger. Within the latest survey by the UK Authorities, 85% of the general public supported wind and photo voltaic initiatives. Just one% have been against renewables. Three-quarters assume renewables are good for the financial system.

    Simply 12% stated they might be sad about having an onshore wind farm of their space, and simply 7% for a photo voltaic farm.

  4. Renewables are being paired with farmland. Prior to now, there was usually the idea that renewables must be positioned on new, further land. We’d must ‘quit’ farms or different land makes use of to create space for them. However, wind energy is now being mixed with farmland, and photo voltaic on farmland (agrivoltaics) has rising assist.

If MacKay had written his e-book in 2023, he wouldn’t have waved away as a lot photo voltaic PV for being ‘too costly’ or wind energy for NIMBYism (“not-in-my-backyard”).

At this level, I’m going to undergo every of those applied sciences one-by-one. A few of you may not have an interest within the particular particulars. In that case, be at liberty to drop off right here.

The conclusion it’s best to take away from this replace is that the prospects for renewable vitality in Britain usually are not as bleak as they have been in 2008. Photo voltaic and wind energy might outstrip our demand – and we wouldn’t have to cowl the nation with generators and panels.

That is true, even in the event you assume the up to date numbers are too optimistic. You could possibly assume that there was no floating offshore wind, and provide would nonetheless match demand.

To be clear: this doesn’t imply that that is the ‘optimum’ electrical energy combine in 2050. Not least as a result of vitality storage prices can be very excessive. We’d in all probability need to diversify a bit, not least to assist with grid balancing. Earlier than all the nuclear followers get mad: I believe there’s room for nuclear in there too.

However the level nonetheless stands: it appears we have now lots of untapped photo voltaic and wind sources they usually might make up a big chunk of our grid, even when they’re not 100% of it.

Current updates counsel that our potential for offshore wind is way larger than David MacKay estimated. That is due to the event of floating offshore wind.

A significant limitation to fastened offshore wind is water depth: they’ll’t be put in in very deep waters as a result of they should be fastened to the seabed. As an alternative, floating offshore wind is constructed on a platform, which is then anchored to the seabed. Right here’s an thought of what they look like. This implies we are able to have wind farms additional offshore, the place there may be much more wind potential.

The variations in estimates are proven within the chart under.

First, let’s begin with MacKay’s numbers. He assumed that 120,000 km2 of water was obtainable for offshore wind. He eliminated two-thirds of this space as a result of it conflicted with transport corridors and different attainable makes use of. Which means 40,000 km2 as his technical estimate.

He then diminished this to five,000 km2 as his sensible estimate because of value and poor public assist. Why he divided by 8 to get this closing determine will not be clear.

O’Callaghan et al. (2023) estimate that there’s between 2,500 to 12,000 km2 obtainable for fastened offshore wind, and 62,000 km2 for floating offshore. For his or her fastened offshore estimates, they eliminated any farms inside 25 miles of the shore because of the visible influence.

That equates to 2% of the UK’s unique financial zones for fastened offshore wind, and eight% for floating offshore.

The variations in space estimates are given within the desk under.

The authors give three causes for his or her discrepancy with MacKay’s estimates.

  1. Improved fastened turbine applied sciences. MacKay described all waters deeper than 30 metres as “not economically possible”. However fastened generators might quickly be commercially possible to round 80 metres of depth.

  2. Floating offshore generators. The appearance of floating generators implies that these can lengthen into a lot deeper waters. Observe that O’Callaghan et al. (2023) already account for a lot of different competing makes use of comparable to fishing areas, army zones, transport routes, and low-wind areas.

  3. Improved social and political assist. O’Callaghan et al. (2023) assume there may be much less public resistance to offshore wind, which appears acceptable.

Lastly, a couple of particulars on how O’Callaghan et al. (2023) calculate their wind output. They assume a mean capability issue of fifty%, a turbine measurement of 15 MW, and a spacing of seven occasions the turbine diameter between them.

David MacKay estimated that round 10% of British land might technically energy wind generators. That may produce round 449 TWh per yr. Primarily based on considerations about public assist, he diminished this to 1.5% for his ‘sensible’ estimate. That offers 67 TWh. See the chart under.

Varied research have prompt that rather more of Britain has ample wind potential: starting from 18% to 44% of land.

Of their replace, O’Callaghan et al. (2023) take a conservative estimate of 5% of British lands having wind farms – all of this is able to be on shared agricultural land. That may imply one-thirteenth of the nation’s farmlands can be shared with wind initiatives.

To get this 5% determine, they did the next. Took the typical of earlier research wanting on the space of land with excessive wind potential: that gave 23% of land. They then minimize this determine by three-quarters to account for the truth that many landowners can be proof against the set up of wind, and a few native communities would oppose it too.

Many of the ‘land’ used for farming is definitely open area: it’s the unused spacing between the generators. The quantity bodily impacted by the set up of the generators, roads, and infrastructure would solely be 0.05% of British land. For context, round 0.9% of land in English is used for quarrying.

Lastly, a couple of particulars on how O’Callaghan et al. (2023) calculate their wind output. They assume a mean capability issue of 38%, a turbine measurement of seven MW, and a spacing of 6 occasions the turbine diameter between them.

Photo voltaic PV has developed quickly since 2008. Cells have grow to be extra environment friendly and costs have plummeted.

For his technical estimate, MacKay assumed that 10% of British land was used for panels with a ten% effectivity. Irradiance within the UK was assumed to be 110 W/m2. For rooftop photo voltaic, he assumed 10% environment friendly cells on south-facing roofs.

As you possibly can see within the chart, his ‘sensible’ estimate was diminished to nearly zero. He thought photo voltaic was far too costly (which was true in 2008, however not immediately).

O’Callaghan et al. (2023) assume that 2% of British lands could possibly be used for photo voltaic. This may be mixed with agricultural lands – ‘agrivoltaics’. The typical photo voltaic irradiance within the UK is 101 W/m2. This accounts for night-time and cloud cowl. The authors minimize this 101 by 55% to account for the spacing of the panels and added 15% to regulate for optimum tilt. That gave them 52 W/m2. They assumed a panel effectivity of 25%, masking 2% of British land, which is 4,740 km2.

Multiply these numbers collectively, and the variety of hours in a yr (8,760) and we get 544 TWh. For rooftop photo voltaic, they estimate simply 25 TWh.

What are the main variations to MacKay?

  1. Decrease value: the value of photo voltaic PV has fallen by 90% within the final decade. MacKay’s predominant concern was it was too costly: this isn’t the case immediately.

  2. Improved cell effectivity: MacKay used a cell effectivity of 10%, and thought an effectivity of 30% can be “fairly outstanding”. Final yr, Fraunhofer ISE achieved 47.6%. Efficiencies better than 30% have additionally been achieved utilizing perovskite photo voltaic cells. O’Callaghan makes use of a cell effectivity of 25%. See the footnote for a chart displaying the variations in effectivity over time.

  3. Mixed use with agriculture: MacKay assumed an inherent trade-off between agricultural land and photo voltaic. He thought the Brits would by no means quit farmland for photo voltaic panels. However this trade-off doesn’t all the time exist: there are now a range of projects the place photo voltaic and agriculture work in tandem (‘agrivoltaics’).

No matter how a lot potential photo voltaic and wind have, we’re nonetheless very distant from a low-carbon vitality combine.

Within the chart under I’ve in contrast the UK’s electrical energy era from low-carbon vitality sources (which is broader than photo voltaic and wind – it has respectable quantities of nuclear and bioenergy) in 2022, to the assorted estimates of ultimate vitality demand in 2050. Provide information comes from Ember Climate.

We have to produce 5 to 7 occasions as a lot low-carbon vitality as we do immediately. Higher get constructing rapidly.

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