Opinion A topflight science brainbox at Cambridge University has weighed into the ever-louder and more unruly climate/energy debate with several things that so far have been mostly lacking: hard numbers, willingness to upset all sides, and an attempt to see whether the various agendas put forward would actually stack up.

Professor David J C MacKay of the Cambridge University Department of Physics holds a PhD in computation from Cal Tech and a starred first in Physics, so we can take it that he knows his numbers. And, as he points out, numbers are typically lacking in current discussion around carbon emissions and energy use.

MacKay tells The Reg that he was first drawn into this field by the constant suggestion — from the Beeb, parts of the government etc — that we can seriously impact our personal energy consumption by doing such things as turning our TVs off standby or unplugging our mobile-phone chargers.

Anyone with even a slight grasp of energy units should know that this is madness. Skipping one bath saves a much energy as leaving your TV off standby for over six months. People who wash regularly, wear clean clothes, consume hot food or drink, use powered transport of any kind and live in warm houses have no need to worry about the energy they use to power their electronics; it’s insignificant compared to the other things.

Most of us don’t see basic hygiene, decent food and warm houses as sinful luxuries, but as things we can reasonably expect to have. This means that society as a whole needs a lot of energy, which led MacKay to consider how this might realistically be supplied in a low-carbon fashion. He’s coming at the issues from a green/ecological viewpoint, but climate-change sceptics who are nonetheless concerned about Blighty becoming dependent on Russian gas and Saudi oil — as the North Sea starts to play out — will also find his analysis interesting. Eliminating carbon largely equates to eliminating gas and oil use.

“I don’t really mind too much what your plan is,” MacKay told The Reg this week. “But it’s got to add up.”

He says he’s largely letting his machine-learning lab at Cambridge run itself these days, and is personally spending most of his time on trying out different energy scenarios.

MacKay sets out his calculations in a book, Sustainable Energy — Without the hot air. You can download it here. As he says:

The one thing I am sure of is that the answers to our sustainable energy questions will involve numbers; any sane discussion of sustainable energy requires numbers. This book’s got ’em, and it shows how to handle them.

He emphasises that the book isn’t quite finished yet, and says he’s always glad to hear from someone who has something to add or has spotted a mistake.

In Without the hot air, MacKay examines our total energy usage in the UK, and then tries to provide a similar amount of energy but without using any oil and gas. He’s willing to consider windpower on a thoroughly heroic scale, as it is probably the renewable technology best suited to the UK climate. As a benchmark for wind, he writes:

Our conclusion: if we covered the windiest 10 per cent of the country with windmills, we might be able to generate half of the energy used by driving a car 50 km per day each. Britain’s onshore wind energy resource may be “huge,” but it’s not as huge as our huge consumption. I should emphasize how audacious an assumption I’m making. … The windmills required … are fifty times the entire wind hardware of Denmark; seven times all the windfarms of Germany; and double the entire fleet of all wind turbines in the world. This conclusion – that the greatest that onshore wind could add up to, albeit ‘huge’, is much less than our consumption – is important …

MacKay doesn’t neglect offshore wind either, but is distressed by its cost and the relatively limited amount of sea which would really be suitable for it. But again, he’s more than ready to factor in vast amounts of offshore wind into future plans — just to see if it really can keep the lights on.

MacKay also gets into solar, both the thermal and electric kinds. Thermal has some potential for home energy, it seems, and is a good idea. (Funnily enough, almost all home microgeneration kit in the UK right now is solar-thermal water heating, so he might just be right here.) But solar photovoltaic (PV) electricity is viciously expensive in the cloudy UK, and just sticking panels on roofs won’t do much — it seldom yields any large proportion of the energy used in the building it’s on top of. You need to cover a big portion of the country in cells.

All in all, according to MacKay, if you like solar it probably makes more sense to put the panels in North Africa and bring the power to the UK over efficient high-voltage DC lines.

As an engineering matter the desert-solar idea is quite feasible — not very different in scale from piping in gas across continents and beneath seas, as people already do. Those fretful about buying power from Russia or the more unsavoury Gulf oil producers might be equally unhappy to buy it from Libya or Algeria, however.

Then, of course, there’s biofuel. MacKay ignores the matter of food prices to begin with, but still finds that biofuel crops demand vast amounts of land to produce quite limited energy yield. he notes that once upon a time the human race generated nearly all its energy from biomass fuel, but that only worked with a Middle Ages living-standard and population.

The most efficient plants … deliver an average power of 0.5W/m². Let’s cover 75 per cent of the country with quality green stuff. That’s 3000m² per person devoted to bio-energy. This is the same as the British land area currently devoted to agriculture. So the maximum energy available, ignoring all the additional costs of growing, harvesting, and processing the greenery, is … 36 kWh/d per person.

Wow. That’s not very much, considering the outrageously generous assumptions we just made, to try to get a big number.

MacKay also considers tidal power and hydropower, and assumes that they will be used to the fullest. Being interested in using erratic wind power on a big scale he sees that massive wind needs massive backup. He makes estimates on the two most eco-friendly backup systems: battery storage in millions of electric vehicles plugged into the grid, and pumping huge quantities of water uphill, so as to release it via hydropower turbines when needed during windless days or demand spikes.

He also floats another nice idea, intelligent appliances which can sense the grid’s pain during times of high demand and ease off on their power demand automatically. However, having assumed these are widespread, he still sees a huge need for pumped-water storage in any wind-heavy future grid.

Fridges can be modified to nudge their internal thermostats up and down just a little in response to the mains frequency, in such a way that, without ever jeopardising the temperature of your butter, they tend to take power at times that help the grid.

Popular soap operas such as Coronation Street and EastEnders typically generate TV pick-ups of 600–800MW … automatically switching off every fridge would nearly cover these daily blips of concerted kettle boiling.

Fluctuations in wind power will be a different matter.

MacKay also takes a look at the somewhat less right-on options. The biggies here are “clean” coal, in which coal power stations are modified so that the carbon they emit is captured and stuffed away somewhere, perhaps in old gas fields. For a man of his leanings — MacKay is a fairly hardcore pacifist, and more than a bit of a tree-hugger — he’s refreshingly open-minded.

We must not let ourselves be swept off our feet in horror at the danger of nuclear power. Nuclear power is not infinitely dangerous. It’s just dangerous, much as coal mines, petrol repositories, fossil-fuel burning and wind turbines are dangerous.

MacKay concludes that nuclear scales up easily, and does so without dominating the country the way wind, solar, tidal and biomass do. The scale of engineering required, in terms of megatons of steel and concrete or areas of land and sea taken up, is enormously down on that needed by useful amounts of renewables.

Concerns over fuel price and security of supply aren’t nearly as much of an issue as they are with fossil fuels, because it’s comparatively easy to store energy-dense nuclear fuels like uranium and thorium — you could have several years’ supply stockpiled in the UK. If the price of the fuels rose, even if it multiplied seriously, it wouldn’t affect the price of energy much. Almost all the cost of nuclear energy comes from building, running and decommissioning the plant, and handling the wastes after.

Even so, present day nuclear fission technology is at best “a stopgap”, according to MacKay. His numbers suggest that the present method of using uranium would allow the entire human race to live like power-hog Americans in terms of power use for about a third of a year — assuming that only the uranium reserves now confirmed exist. Here MacKay perhaps reveals his natural anti-nuclear leanings somewhat, as he has put nuclear power to a much stiffer sustainability and fairness test than coal. But, showing commendable intellectual honesty, he goes on.

At present, there being no scarcity of uranium, it is typically dug from the ground and run through simple power stations just once before being classed as waste. Nobody explores for more uranium, and nobody has done so since the 1980s, because supplies are ample to meet current demand. There’s probably a lot more to be found, especially if the price of ore rose a lot. (Which wouldn’t affect the price of the energy significantly, remember.)

Furthermore, the use of fast-breeder reactors would get sixty times as much juice from a given amount of uranium, according to MacKay. Then, most get-at-able uranium is actually in the oceans, not in the ground — and the scale of the effort needed to mine the oceans for uranium, while noticeable in the same way as the nuclear stations themselves, is much less than mining the sea for wind and tide power.

Then, too, there’s thorium — probably a lot more abundant than uranium, and likewise full of juice.

Even MacKay admits that fast breeders and oceanic uranium together would power the entire human race at hoggish American levels for well over a thousand years, or at current European consumption for several millenia. He also says that known thorium reserves, used with current tech, would run the whole race at rich-westerner levels for several decades.

There’s also a thing called a thorium energy amplifier reactor which would be a lot more efficient. If it works as its Nobel prize-winning designers predict, known thorium reserves would run six billion people at American luxury for sixty thousand years.

Moving on to fusion power, MacKay says:

Fusion power is speculative and experimental. I think it is reckless to assume that the fusion problem will be cracked, but I’m happy to estimate how much power fusion could deliver, if the problems are cracked.

At [US levels of consumption] and 6 billion people, [deuterium] fusion would last 1 billion years.

MacKay is keen to stress that oceanic uranium extraction, the thorium energy amplifier and especially fusion are all unproven — though fast breeders are established kit. This is why he sees nuclear as a “stopgap”. He freely admits, however, that building new nuclear power stations is the most economic way of generating low-carbon power — and he confirmed to The Reg that in his view there would certainly be ample supplies of uranium to last the lifetime of any likely number of new UK plants.

MacKay sees nuclear as a “stopgap” and perhaps a “gamble”, but he fears that he may still have painted it in so positive a light that people will brand him as “pro-nuclear”. He emphasised to The Reg that he absolutely isn’t, and we believe him.

You can see why he’s worried about getting that label, though. Worst case, assuming that only the known technologies work and only the known reserves exist, MacKay tells us that the entire human race could power itself — transport, domestic, industry, the lot — at hugely profligate American levels using nothing but fission for around a century. Since it’s unlikely that everyone will suddenly ditch fossil and ramp up to that level of use overnight, realistically you’re talking about at least a couple of centuries; longer if people only fancied being Europeans rather than Americans. It wouldn’t even cost much, compared to renewables.

A pretty useful stopgap, then. And if any of the gambles pay off — oceanic uranium, new thorium tech or fusion — the human race can pretty much relax. We’re sorted for at least a millennium, by which point we’ll hopefully be mining other planets.

Having lined up his numbers, MacKay tries them out for size on various different agendas. He takes the low-hanging fruit in every plan, as he cuts off the oil and gas.

Firstly most transport is electrified, allowing millions of vehicle batteries to be used as power reservoirs to deal with grid fluctuations — though MacKay admits that people might be upset if the wind inconveniently dropped at the wrong time, perhaps leaving their cars flatlined when they needed to be charged up. He also allows some big land areas for growing biofuel to handle things which can’t be electric — some aviation would still be feasible, for instance.

Also, MacKay assumes big savings from more energy efficient buildings, universal home solar thermal and the use of heat pumps — helped out with “the promotion of sweater-wearing by sexy personalities”. Biomass heating is also used to the limit in every case, as is generation of energy from domestic waste.

All this leaves electricity consumption roughly tripled, and daily demand swings get worse. The difference in the various plans is how you deal with this.

The baseline plan is D, the “domestic diversity” plan, where the UK emits no carbon and lives off its own resources as much as possible. This means:

A 30-fold increase in wind power over the 2007 installed power. Britain would have nearly three times as much wind hardware as Germany has now … wave power requires 7500 Pelamis deep-sea wave devices occupying 500 km of Atlantic coastline … tide power comes from 5GW of tidal stream installations, a 2GW Severn barrage, and 2.5GW of tidal lagoons, which can serve as pumped storage systems too …

Nuclear power (40GW) is a roughly four-fold increase of the 2007 nuclear fleet … clean coal (40GW) corresponds to taking the current fleet of coal stations, which deliver about 30GW, retrofitting carbon capture systems to them, which would reduce their output to 22GW, then building another 18GW of new clean coal stations. This level of coal power requires an energy input of about 53 kWh/d/p of coal, which is a little bigger than our current rate of burning of fossil fuels, and well above the level we estimated as being ‘sustainable’.

This rate of consumption of coal is roughly three times the current rate of coal imports … the UK would not be self-sufficient for coal [even if all our own mines re-opened].

Next, MacKay offers Plan N, “the ‘NIMBY’ plan,” for people who object to a land filled with windmills and who won’t have nuclear plants either. This means massive imports of energy.

First, we turn down all the renewable knobs … (Don’t misunderstand! Wind is still hugely increased over its 2007 levels – by a factor of 7.5, to be precise) …

25GW of nuclear power could, I think, be squeezed onto the existing nuclear sites. I left the clean coal contribution unchanged.

This plan requires the creation of five blobs each the size of London (44 km in diameter) in the [North African] desert, filled with solar power stations. It also requires power transmission systems to get the power up to the UK, and storage systems to store energy from the fluctuating sun. Once we’ve decided to import solar power from other countries, there’s little point having solar PV on our roofs at home – the same panels could always generate more in a sunnier country.

This plan gets … 72 per cent of the UK’s electricity [thus, most of its power] from other countries.

You could say you’ve exchanged a pipeline to Russia — or tankers out of the Gulf — for HVDC lines to Libya in this scenario. MacKay nonetheless thinks that the relationship with Colonel Gadaffi would be much more positive than our current dealings with the Saudis, Iraqis, Moscow et al.

Next, there’s a plan for those who just hate nuclear:

We can create a nuclear-free plan by taking plan D, keeping the renewables, and doing a straight swap of nuclear for desert solar power.

This plan imports 64% of UK electricity from other countries. I call this ‘plan L’ because I think it aligns fairly well with the current policies of the Liberal Democrats.

Then, there’s the hard-green option for those who won’t have nukes or coal at all — plan G. “Greenpeace, I know, love wind,” says Mackay, “so plan G is dedicated to them, because it has lots of wind.”

Nudging up the wave contribution … and bumping up wind power by a whopping 24 to 32 kWh per day per person … wind delivers 64 per cent of all the electricity.

Under this plan, world wind power in 2007 is multiplied by four, with all of the increase being placed on or around the British Isles. Roughly one hundred of Britain’s major lakes and lochs would be required for the associated pumped storage systems.

This plan gets 14% of its electricity from other countries.

The immense dependence of plan G on renewables, especially wind, creates difficulties for our main method of balancing supply and demand, namely adjusting the charging rate of millions of rechargeable batteries for transport. So in plan G we have to include substantial additional pumped storage facilities, capable of balancing out the fluctuations in wind on a timescale of days … Most major lochs in Scotland would be part of pumped storage systems.

It’s worth noting that in earlier analysis, MacKay suggested that pumped storage on this scale would be very hard to achieve using existing lakes and lochs. In actuality, vast amounts of seawater would probably get pumped up and down mountains and cliffs routinely to bridge the huge demand swings of a mostly-electric Britain and the massive variations in a mostly-wind powered grid.

MacKay made no effort to cost plan G, but he offers maps and figures indicating the staggering scale of the engineering. Britain would be literally covered with — and girdled by — massive wind farms, tidal barriers and wave barrages, and every sizeable body of water in the land would rise and fall to the strange new tides of the national grid. We would have literally rebuilt the British Isles as a single mighty renewable generator, pouring concrete and erecting steel on a scale so far matched only by human habitation — industrialising the land and sea in a way that would make intensive agribusiness look like a wildlife refuge. And still we’d be importing power.

That’s the reality of the Greenpeace plan for the UK, in hard numbers. You can see why MacKay is worried about their response.

Finally, having done is-it-feasible plans driven by greater or lesser amounts of different agendas, MacKay considers what would happen if you simply dispense with oil and gas, insist that coal must be carbon free, and let the market work within that framework.

E stands for ‘economics’. On a level economic playing field with a strong price signal preventing the emission of CO₂, we don’t get a diverse solution, we get an economically optimal solution that delivers the required power at the lowest cost. And when ‘clean coal’ and nuclear go head to head on price, it’s nuclear that wins. (The capital cost of regular dirty coal power stations is £1 billion per GW, about the same as nuclear; but the capital cost of clean coal power, including carbon capture and storage, is roughly £2 billion per GW.) Offshore wind also loses to nuclear, but I’ve assumed that onshore wind costs about the same. My final plan is a rough guess for what would happen in a liberated energy market with a strong carbon price.

This plan has a ten-fold increase in our nuclear power over 2007 levels. 110GW is roughly double France’s nuclear fleet. I included a little tide because I believe a well-designed tidal lagoon facility can compete with nuclear power. In this plan, Britain has no energy imports except for the uranium…

The nice thing about MacKay’s numbers is that you can try out your pet theories with them, and have some confidence in the results. The prof confirmed to The Reg that he’s thinking of an online tool which might let people try out their favourite policies.

In the meantime, you can read his book — even help him finish it, maybe.

No matter what your feelings about MacKay’s results and his politics — just for instance, he’s quite sympathetic to the idea of not paying that part of your taxes which goes to the military (a few per cent, in the UK) — you disregard his maths and physics at your peril. His work is a serious contribution to the energy debate. ®