Rational Energy Policy – SEWTHA Revisited
What Sustainable Energy Without Hot Air said and what has happened since
I’m concerned about cutting UK emissions of twaddle – twaddle about sustainable energy. Everyone says getting off fossil fuels is important, and we’re all encouraged to “make a difference,” but many of the things that allegedly make a difference don’t add up.
David J. C. MacKay
A few weeks ago, I pledged to write about what a rational energy policy would look like to deliver cheap, abundant and safe energy with a small environmental footprint. My initial thought was that it would be a single article. However, my research has revealed a lot of interesting information and also sent me down a few rabbit holes. I now know this is going to be a much bigger piece of work that needs to be broken into more manageable chunks. This will help me as a writer to keep a regular delivery schedule and also you, the reader, to receive digestible chunks of information. So, this is the first instalment of a short series on what I am terming Rational Energy Policy. The series will include:
Analysis of Sustainable Energy Without Hot Air and what has changed since it was written in 2008.
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Evaluation of the National Grid ESO Future Energy Scenarios.
Examination of the Government’s latest Powering Up Britain publication.
Assessment of the different potential energy sources across different dimensions
My ideas for a new way forward for UK energy policy.
Perhaps a summary article drawing it all together.
Sustainable Energy Without Hot Air
Professor Sir David MacKay was a particularly important figure for a number of reasons. First, he was made a professor of Natural Philosophy at Cambridge in 2003 then later promoted to Regius Professor of Engineering in 2013, so it is clear he was a heavyweight thinker. He carried out important work in many fields of research. However, for the purposes of this article his most important work is his book Sustainable Energy Without Hot Air (SEWTHA) published in 2008. From 2009-2014 MacKay was Chief Scientific Advisor to the Department of Energy and Climate Change (DECC), the predecessor to the current Department of Energy Security and Net Zero (DESNZ). Sadly, he died in 2016.
MacKay took great pains to ensure that energy policy was based on numbers, not adjectives. Everything he proposed had to add up, even if the process of making the sums work, some unpalatable truths had to be confronted. Sadly, emissions of the twaddle he complained about in the opening quote above have not abated and several plans the Government are following do not seem to add up. Let us walk through the scenarios MacKay proposed and what has happened since his seminal work was published.
SEWTHA – Energy Demand
Throughout his book, David MacKay used an unconventional measure of energy, namely kWh per person per day. He did this to personalise energy consumption on a level most people can understand. He proposed that UK energy inputs of 125kWh per person per day in 2008 would fall to 68-70kWh/p/d by 2050 (see Figure 1). The losses from thermal sources of electricity in 2050 are ignored, so there is a bit of a sleight of hand in the overall percentage reduction. MacKay assumed 48-50kWh/p/d of our energy coming from electricity in 2050.
The 20kWh/p/d balance of energy consumption would come from heat pumps, wood (biomass) and solar hot-water heating. In addition, 2kW/p/d of biofuel is used to power vehicles that are difficult to electrify.
The suggested 50kWh/p/d that comes from electricity equates to an average generation of 153GW assuming 73.3m people (as per ONS) in 2050. Our electricity generation currently peaks around 45GW in winter today. So, under his plan, we would have to increase generation capacity many-fold to achieve an average of 153GW.
MacKay suggested that improvements in efficiency would bridge most of the gap between 2008’s energy consumption and that in 2050. Energy for heating would fall by roughly 25% from better insulation and using heat pumps instead of gas-fired boilers. Transport energy would be halved by switching from ICE vehicles to electric vehicles. Thermal losses from electricity generation would also fall dramatically, although how much depends upon the generation mix. Overall, the fall from 125 to 70kWh/p/d represents a reduction of 44% in energy use.
SEWTHA’s Five Plans to Meet Energy Demand
MacKay proposed five alternative plans for how energy would be produced in 2050 as shown in Figure 2.
Overall, he plays with different mixes of generation capacity to deliver the 50kW/h/p/d. The big chunks are “clean coal,” nuclear, solar from deserts and wind. All of his plans also include relatively minor contributions from tide, wave, hydro, domestic solar PV and waste incineration. Interestingly, none of MacKay’s models include natural gas as an energy source, even though gas produces less CO2 and fewer noxious emissions like particulates, SOx and NOx than burning coal.
Plan D stands for “domestic diversity” and uses a lot of every possible domestic source of electricity. Solar from deserts is ruled out. Clean coal and nuclear do the heavy lifting of most of the required electricity generation. By “clean coal” he means burning coal and capturing and storing the resulting CO2 emissions. His 16kW/p/d, using 2050 population projections and 90% capacity factor for both nuclear and coal amounts to around 54GW of installed capacity for each of coal and nuclear. The 8kWh/p/d of average wind generation translates to 24GW, equating to an installed capacity of around 74GW of onshore and offshore capacity with an average load factor of 33%. He also indicates that the installed wind capacity would require 400GWh of storage which he assumes would be mostly pumped hydro. We will look at storage in more detail later.
He calls Plan N the Nimby plan for people who do not like industrialising the countryside with wind turbines and are not keen on nuclear power stations either. Consequently, under this plan a substantial chunk of our energy comes from solar PV in deserts. Personally, I am not keen on sourcing a critical amount of energy from countries in North Africa with high political risks. Plus, there is the risk of sabotage to the umbilical cable transferring all that energy, like what happened to the Nord Stream pipeline last year. He keeps clean coal under this plan and some nuclear with much reduced wind capacity compared to Plan D.
Plan L is the “Liberal Democrat” plan for people who would like no nuclear power at all, rather like Germany today. Under this scenario, the nuclear in Plan D is replaced by desert solar with the same geopolitical concerns as above.
MacKay labels Plan G the Green plan for people who do not like either nuclear or coal power. To replace the coal and nuclear, Plan G adds much more wind and a bit more wave power. The 32kWh/p/d equates to around 300GW of installed wind capacity at an average 33% average load factor, or more than 10 times today’s installed capacity. He acknowledges that this scenario would create difficulties for balancing supply and demand and suggests that pumped storage facilities equivalent to >400 Dinorwigs (4,000GWh) would need to be built, although even this could only cope with a wind lull lasting 2 days. Any longer and the lights go out. A more credible assessment might require storage to cope with a 7-to-10-day wind lull which would require even more storage. This plan also relies on getting 14% of electricity from other countries. I would say Plan G is not feasible.
Under Plan E, the E stands for Economics which is his best guess of what would happen in a liberated market with a strong carbon price. This plan gets most of its electricity from nuclear power. 44kWh/p/d with 73.3m people and a 90% load factor equates to an installed capacity of around 150GW. After recent closures, our current operable capacity is around 5GW. So, to achieve this would require a 30-fold increase in nuclear power or roughly 6 times more than the 24GW being planned in the Government’s Energy Strategy. This plan also includes around 37GW of installed wind capacity plus associated storage.
Other Observations in SEWTHA
Reading Sustainable Energy Without Hot Air, several other significant points stood out to me:
MacKay was not keen on hydrogen as a source for many of the same reasons I highlighted here.
Even in plans D and L, the expected contribution from tide, wave and hydro is a relatively small proportion of our overall energy needs.
The book poured cold water on direct carbon capture from the air. He thought it would be too much of an energy sink. It still is.
He also urged policymakers to focus on the important things and get them right. Too much focus on trivial things takes up too much bandwidth and achieves little.
The Storage Elephant in the Room
Although SEWTHA does a reasonable job of discussing daily and weekly variations in energy demand, the book only makes a superficial analysis of the inter-seasonal storage requirements with a renewable-heavy generation mix.
On the daily and weekly scale, David MacKay makes the point that if we have a 5-day wind lull from an expected 10GW average production from 33GW installed wind capacity we would need to store 1,200GWh (10 x 5 x 24) of energy. He compares this to the pumped-hydro capacity we had at the time of around 30GWh. We are short by a factor of 40. We might have the geography (maybe not the political will) to get to 100-400GWh if we dammed all of the most suitable places in Scotland and Snowdonia.
However, plans D, L and G imply 74-296GW of installed wind capacity, delivering an average of 24-98GW of power. These plans need 2.5 to 10 times more storage for a 5-day lull in the wind. This amounts to 2,900-11,800GWh. Pumped-hydro will never get anywhere near this requirement.
To help bridge the storage gap, MacKay also looks to what is now called “Vehicle-to-Grid” technology. This means using the energy stored in electric vehicles to help balance the grid when demand ramps up at the same time as the wind drops. A typical average electric car might hold 60kWh when full (for example the VW iD3). If we were to drain on average 5% from each battery (3kWh) in a day, then 33m passenger cars would be able to deliver nearly 100GWh. If you could do this for five consecutive days, taking a quarter of the entire EV storage capacity if they were all full when you started, then you might get 500GWh. Adding this to the maximum potential pumped-hydro would not even cover a 5-day lull with 33GW installed capacity and would be virtually useless for plans D, L and G. Even then, where would the power come from to recharge the cars and how do people get around during the lull period?
The storage required to support such a large wind generation capacity is totally unfeasible. The only way it could work is if there’s flexible backup generation available. We use gas-fired power stations for this purpose now. We might be able to use waste incinerators in a comparable way in the future, if we could store the waste without other problems arising.
However, this daily storage problem pales into insignificance compared to the inter-seasonal storage requirements. The Government produces monthly data for the consumption of gas and electricity in their Energy Trends reports. As can be seen in Figure 3, electricity usage fluctuates significantly throughout the year from about 22TWh in the summer months to around 28TWh in December and January.
Using DUKES data (Table 1.1.1) that analyses annual consumption by type, I have tried to strip out gas used in electricity generation from the monthly gas consumption data. Combining this adjusted seasonal gas consumption data with the seasonal electricity data shows a much more pronounced variation (see Figure 4). Total energy consumption averages of around 73GW in the summer months and 124-130GW in winter.
Of course, the energy required for heat will fall if we all switch to heat pumps, but there will still be a large swing in demand between summer and winter. This leads to a need for a very large inter-seasonal storage requirement. Indeed, in the National Grid FES report, they call for 11-56,000GWh of hydrogen storage in their various scenarios. I will share more on this and other ideas on how to mitigate the problem in a subsequent article.
Other Weaknesses in SEWTHA
Fifteen years have passed since David MacKay wrote Sustainable Energy Without Hot Air and we can now look back and see that he got a lot right in his assessments. However, there are two more items he overlooked or glossed over.
Planning for Discomfort
The first issue I have is that a great deal of the plan is centred around reducing heating in the home, with all of us being urged to put on a woolly jumper and turn the thermostat down to 15 or 17 degrees. Fundamentally, this is planning for discomfort and I do not think it will go down well with the public. We should be planning for abundance and comfort, not taking a retrograde step.
Little Focus on EROEI
Second, there is no explicit mention of Energy Return on Energy Invested (EROEI) for any of the technologies. MacKay does talk about energy yield ratio, but he produces numbers that are far removed from the later paper by Weissbach. He also discusses the massive mineral requirements of offshore wind for instance but does not explicitly relate it back to EROEI. I previously discussed EROEI and the need for our energy sources to be over a threshold of 5-7 if we are to continue to enjoy the fruits of an advanced economy. Wind plus storage does not meet that threshold, neither does solar PV at our latitudes.
What has happened to UK Energy Consumption since SEWTHA was written in 2008?
Having looked at the plans that MacKay set out, it is helpful to look at what has happened to UK energy consumption since he wrote the book in 2008. He called for a 44% reduction in total energy use by 2050, with most of the reduction coming from increased efficiency of electric vehicles and domestic heating. Using DUKES Table 1.1 data total energy use per person has already fallen 36% or 41kWh/p/d to 81kWh/p/d between 2008 and 2020. Only 11 more kWh/p/d to meet the target of 70 he set out back in 2008, see Figure 5. The plans from groups like National Grid ESO go far further than MacKay ever did in terms of overall energy reduction. I will present a more detailed comparison in a later article.
Moreover, according to Our World in Data, UK CO2 emissions have fallen by 35-40% since 2008. So, the next time you see a pink-haired Extinction Rebellion activist (oil-based hair dye, natch) screaming that the UK has not done anything to combat the alleged climate crisis, use these statistics to rebut their argument.
My conclusions from re-reading SEWTHA are as follows:
It is important to focus on the big picture and not get bogged down in trivial details that will never move the dial.
There are practical limits to the amount of energy we can expect to draw from intermittent renewables like wind because of the huge storage requirements that are simply too large to ever be feasible. This effectively rules out Plan G.
Imported solar power from North African deserts is unlikely to be a secure enough solution for us to rely on. This rules out plans N and L.
If we say we want to rule out fossil fuels from our energy mix, even with CCUS, then plan D is also ruled out.
That leaves plan E as the only viable solution capable of reliably delivering our energy needs. We need much, much more nuclear power.
We can utilise other technologies such as tidal, wave, pumped hydro and waste, but they are unlikely to ever form a large part of our energy mix.
I will explore the consequences of these conclusions in subsequent articles.
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