🎓 L’energie au XXIe siècle – Jancovici – Part II

Welcome back. These red pills were pretty strong, eh? 😨

Help yourself in Part I if you missed out.

We saw how the industrial revolution, powered by cheap fossil fuels (80% of global energy today) propelled billions of us to comfortable lives in the service sector, with holidays and leisure time, consumerism and all that good stuff. We saw how GDP is incredibly closely correlated to energy consumption.

But it’s time to pay the bill:

  1. We are hitting diminishing returns on extracting these fossil fuels, and their reserves are finite
  2. The exploitation of these fossil fuels causes global warming which threatens our ability to feed the planet and avoid mass population displacements

Let’s dig into the second part of Jancovici’s course which looks at how we can try to soften the landing

(and, rejoice, a part III is coming covering the last lecture which has some industry case studies from Janco’s day job trying to help companies cut their footprint…)

5- Using Less Energy

Kaya’s identity

Global CO2 emissions = Carbon intensity of the energy supply * Energy intensity of GDP * GDP per capita * Global population

If global CO2 emissions MUST go down by 3x eventually (either because global warming compels us to, or because fossil reserves run out) which of the factors that make up CO2 emissions can we pull on?


  • Low-end of predictions say 9B by 2050
  • Difficult topic to influence globally, lots of complex ramification.
  • Main thing we can do is securing women’s right to voluntary, high-quality family planning. From Project Drawdown:
    • “225 million women in lower-income countries say they want the ability to choose whether and when to become pregnant but lack the necessary access to contraception.”
  • N-child policies, or reducing state support after the N-th child.

GDP per capita

  • If we maintain ~2% global growth for 30 years = 1.8x GDP increase = 1.8x energy consumption increase in 30 years
  • This growth is sort of “non-negotiable” for most economists / politicians.
  • System becomes unsustainable without growth, cost of servicing debt goes up etc
  • (🤔 The course was a bit light on this… something to dig into more #TODO)

Energy Intensity of GDP

  • Energy intensity (kWh/$) = how many kWhs of energy do we use per $ of GDP
  • Using less energy to provide the same goods and services e.g:
    • Building isolation / energy efficiency
    • More efficient industrial processes
  • Unfortunately over the 18 years up to 2017 we only reduced energy intensity by ~10% on aggregate. ~30% over 50 years
  • And with any optimisation process there are diminishing returns
  • Another problem: Jevons’ paradox / “rebound effects”
    • The Jevons paradox occurs when technological progress or government policy increases the efficiency with which a resource is used (reducing the amount necessary for any one use), but the rate of consumption of that resource rises due to increasing demand.” (Wikipedia)
    • Cars: for identical weight, we have 1/2 the energy consumption of cars. But over the same time period, we’ve made cars 2x+ heavier! Also consumers travel more when cars more efficient.
    • Housing: we now need 3x less energy to per m2 of housing compared to 1950. But we went from < 25m2 per person in 1973 to ~ 40 m2 par person today (in France)
    • Transistors: 1Mx less energy used per transistor, but 50Mx more transistors per computer 🙂
  • (🤔 Presumably the incentives also aren’t fully there to do these savings, as energy is cheap and the carbon externalities still not priced in. This rate of efficiency improvement will probably change with carbon taxes, ESG etc. remains to see by how much it can)

Carbon intensity of the energy supply

  • Decarbonising the electricity supply. How much CO2 are we producing per KWh of energy on average
    • Batteries have a high footprint
eolien = wind. stockage = storage 😉
  • In terms of heating, fioul (petrol-based fuel) is a huge driver at least in France (950g CO/kWh) but increasingly getting phased out
  • Capture & sequestration. Putting CO2 in porous rocks of gas/oil reserves which are empty. Also gets you remaining reserves out.
    • Can’t retrofit old plants.
    • If implemented reduces yield of the plant by ~30% (because need power to do the capture & push the CO2 down)
    • In the US there is already a network & market for CO2 for this reason
  • Important to remember that today:
    • Nuclear is 5% of global energy. Renewables 14%, 12% of which are hydro and biomass
    • Electricity is only 19% of the final energy consumption
  • So important to remember that decarbonising electricity is currently a small subset of decarbonising energy!
    • Transports in particular is hugely reliable on oil (98%)
    • People get this wrong all the time! e.g The Independent here 😡
  • So we’ll need to (1) electrify more things AND (2) continue to decarbonise electricity AND (3) decarbonise what can’t be electrified

Interesting Tidbits

  • Oil imports in the EU have started going down since 2015. Trucks active in the region has gone down correspondingly
  • Ways of pricing carbon:
    • Buying an emission quota on a market. Buying it from the government
    • Tax on carbon emissions
    • “Adjustment cost” on new regulation that prohibits emissions above x
    • Increasing cost of the carbon-based sources
  • Tocqueville predictions on Democracy, in 1840!
    • Will make people individualistic, demanding, consumerist
    • Will give the media huge power (Janco experience: journalists taking a 30min interview and choosing which 20s to show to a broad audience)
    • Will favour short term shallow thoughts to long-term thinking
  • “The people control the politicians”
    • e.g carbon tax project was abandoned in 1 week by Macron with gilets jaunes.
    • e.g countries which have agreed to major carbon commitments are ones that don’t have huge reserves!
    • You have to promise everything to all constituents to get elected… pessimistic about being able to make progress


  • We have to do one or more of (1) reduce population, (2) reduce GDP per capita, (3) reduce the energy needs of our economy, or (4) decarbonise our energy (which is a much bigger task than just decarbonising electricity)
  • The first two are structurally very difficult. Reducing energy needs is happening a bit but will likely not bring the gains we need, and in a democracy passing things like a carbon tax is very difficult.
  • Rest of the course looks into decarbonising energy

6- Nuclear


  • Bombard U235 with a neutron.
  • It absorbs it and turns into U236 which is unstable, the nucleus breaks into into Barium and Kr 92, 3 neutrons, and lots of energy
  • These neutrons can then be absorbed into other U235 nuclei, which we call the “chain reaction”
    • “To control or shut down a nuclear chain reaction, control rods are used. These control rods consist of elements (such as silver, iridium, and cadmium) that are capable of absorbing neutrons without undergoing fission. Boron (another element very good at absorbing neutrons without undergoing fission) can also be added to water surrounding a nuclear reactor to moderate or shut down a nuclear reaction.” (source)
  • Commercially, the U235 isotope is enriched to 3 to 5% (from the natural state of 0.7%) and is then further processed to create nuclear fuel.
  • This is the reaction that was used for Bomb A, Hiroshima and Nagasaki…


  • “In a fusion reaction, two light nuclei merge [“fuse”] to form a single heavier nucleus. The process releases energy because the total mass of the resulting single nucleus is less than the mass of the two original nuclei. The leftover mass becomes energy. (source)
  • Focus is on the deuterium-tritium (DT) fusion reaction (more energy produced)
  • “At extreme temperatures, electrons are separated from nuclei and a gas becomes a plasma—an ionized state of matter similar to a gas. Composed of charged particles (positive nuclei and negative electrons), Fusion plasmas provide the environment in which light elements can fuse and yield energy.” (source)
    • We need to reach 150,000,000 °C to create the plasma
  • As we know, heavy R&D, decades away if at all possible
  • ITER started in 2010, expecting to generate first plasma in mid 2020s, generate excess power in late 2030s (PoC scale) (from my BillyG notes)
  • Can be used for Bomb H, never used yet 🙏

Nuclear Power Plant

  • Same process as a coal plant, both thermal plants, except a different way to generate heat.
  • In both cases, you boil water, create water vapour which makes turbines turn and generates electricity
  • The big tower we see is to cool down, it is water vapour
  • 2-7 reactors per plant. Typically 3-4 reactors
  • Chernobyl was Gen I graphite core
  • EPR (European Pressurised Reactor) designed and developed mainly by Framatome (part of Areva between 2001 and 2017) and Électricité de France (EDF) in France, and Siemens in Germany.”

Operations & economics

  • Very easy to power up/down. You can change output of a reactor by 80% in 30mins.
  • Production of power plants takes a lot of time/upfront capital, so when privately funded (eg as it was predominantly in UK) very dependent on interest rates / opportunity cost

Risks & public perception

Nuclear accidents

  • Chernobyl likely caused 1000s of deaths from long-term radiation exposure. However it was a Gen I graphite core reactor with terrible safety standards.
  • UN agency compiling all the scientific literature now estimate there were no deaths from radiation at Fukushima (deaths were from evacuation and the Tsunami)

Nuclear proliferation

  • It’s a risk. Although you can develop nuclear warheads without a nuclear energy program, eg Israel.

Dealing with nuclear waste

  • <1kg of “high-level” waste per person in France per year
  • Known methods of dealing with it
  • Fission is a natural process, in fact we found natural reactors in Gabon which had been operating for 2B years and the waste was contained!
    • “The natural nuclear reactors in Gabon seem to have been largely protected by enveloping carbonaceous substances and clay, which created and maintained reducing (low oxygen) conditions which largely inhibited the movement of uranium and other radioactive products of nuclear fission.”

Finite reserves

  • Uranium is a fossil fuel too and is finite. Estimated to end around end of century.
  • Gen 4 reactors could run on waste too (something BillyG’s Terrapower is working on, the French program was stopped)

Why the divide?

  • Survey after survey shows the majority of population in France thinks it’s much more dangerous than it actually is, and worse for the environment than it is
  • Interesting Janco hypotheses:
    • Scare-factor of the bombs, and of what we don’t understand
    • Media (particularly state-backed) wants to show they’re “free” / can be against the state, and the state runs nuclear (France electricity is 70% nuclear) so they go against nuclear
    • In France we have a complex w.r.t Germany who do everything better, and they are getting out of nuclear so we should too


  • Nuclear is 5% of global primary energy
  • France: 75% of electricity production. Political commitments to bring it down to 50% to appease Green parties.
  • Italy stopped completely, referendum after Chernobyl
  • Japan stopped after Fukishima but are restarting
  • Germany was already on way out with Shroeder plan since 2000. Merkel was against but had to agree too after Fukushima.
  • Ukraine have doubled production since Chernobyl
  • China, South Korea, going big on it. China is 1/2 of the new reactors in development in the world, including some new EPRs.
  • UK wants to have nuclear but relied on private sector too much, ROI / funding wasn’t there
Total production by country

Share of nuclear in each country’s electrical production


  • Nuclear is 5% of global primary energy generated today, 75% of electricity generation in France
  • It has downsides: nuclear accident risk (although Fukushima is very misrepresented it’s not 0 risk), association with nuclear proliferation, need to deal with the waste, Uranium will run out in ~100 years, needs upfront capital
  • It has clear upsides: runs all the time and can stabilise network (can fully change reactor power by 80% in 30mins), very low carbon footprint, very little land-use required
  • China & South Korea are going big

7- Renewable Energy

  • Primary energy = energy form found in nature that is “expoitable”
  • Renewables are 14% of primary energy worldwide today
    • 10% biomass
    • 2% hydro
    • 2% other (wind, geothermal, solar)

We are producing more and more:

but it’s actually less and less per capita

Energy generation per capita from renewables is actually down over 150 years. Our consumption went up faster than renewables adoption


(Clouds are why you don’t have the same sunlight at given latitude)
  • Top use of course is heating… you don’t need to turn on heating in winter. Can be optimised with verandas, heat pumps
  • Other use: heating water. Note, you can’t really produce 60C water so use normal-sized radiators, have to use floor heating (more surface, lower temp)
    • Particularly prevalent in Dom-Toms where there aren’t prevalent gas networks

Electricity generation via photovoltaics

  • Very surface-hungry. 1km2 generates ~100MW
    • 400x more area needed per unit of electricity produced when compared to nuclear
    • 1m2 well placed enough to produce 1% of 1 French person’s energy use
  • In general when you install PVs in France, you have to sell your production to the network, and then buy back from network. Two separate contracts.
  • Residential is very small. It’s mostly business installations:

CO2 emissions:

  • Footprint of the panel & battery depends on where it was produced because requires electricity eg to melt silicium
  • 10 biggest manufacturers of PVs worldwide are in China
  • If factor in installation, maintenance etc. one analysis says that ROI is 3-5 – for every 1 of energy to put in to exploit solar you need to get 3-5 out (petrol is 1 – 60)

Concentrated Solar Power

Crescent Dunes Solar Energy Project near Vegas. By Amble – Own work, CC BY-SA 4.0, link
  • Concentrate solar energy on a hot source, heat a reservoir. Advantage is can store during the night
  • Ideas to generate from hottest places and create long electricity lines
  • Promising, one big limiting factor will be composing materials
  • #TODO look into this more


  • Basically a water windmill. Move water down and through a turbine
  • Can mostly exploit mountains

Who’s doing it?

  • Biggest potential for new dams is in Asia
  • Remember that most dams in the world are for irrigation not for electricity production
  • Dams can be dangerous
    • Vajont (Italy) accident 2000+deaths
    • Frejus more than 400
    • 1975 Banqiao Dam failure. The collapse of 62 dams, including the Banqiao Dam, in Henan, China in August 1975 under the influence of Typhoon Nina. Death tool estimated from 26,000 to 240,000. The most deadly installation per KWh ever


  • Major categories of use-cases: biofuels, heat, electricity
  • Biofuels
  • For unleaded. Distillation process to make ethanol needs a lot of energy so overall yields are bad
    • US uses 40% of its corn to make ethanol. They are by far biggest corn producer worldwide
  • For diesel. Less costly distillation but the source plants yields are much worse
  • We would need half of the world’s food supply today to replace kerosene used by flights today
  • Environmental impact is difficult to calculate – do you attribute the deforestation to it etc
    • Interesting points from Bill Gates on using agricultural waste to power this
  • Other big problem is we need the forests to maintain ecosystems + sequester


  • How it works:
  • Where we can do it:
  • Same principle for residential: heat pumps. Either storing energy in air on in water
  • Course is light on potential promise #TODO


  • Where it’s at in Europe
  • Power generation proportional to wind_speed3 so super variable
  • Installed power in Europe 170GW. But never really goes above 90GW. And can only guarantee 10GW across Europe
  • Germany built a lot of wind but the share of domestic consumption from wind is flat… they export the delta
    • Actually has not enabled a reduction in other sources (again because of variability)
  • Share of wind generation per country:

Tidal turbines:

  • Advantage is we know exactly when the tides are going to be & their power. Shoutout
  • Disadvantage is conflict of interest with fishermen. Requires lots of upfront material.
  • Wave turbines, bit of a gimmick, don’t get much energy from it

Cost comparison

  • Today, 10-20x lifetime cost of wind vs nuclear. Similar with solar vs nuclear. Also higher carbon footprint
  • Facteur de charge = utilisation rate
  • Duree de vie = lifespan
  • Reseau = network. Need to make network stronger to adapt to wind surplus
  • Stockage intersaisonnier = inter-season storage. Can be “upstream” such as hydro pumping stations. Could also be in residential eg Tesla Powerwall. But in any case requires $
  • Cout au kW installé = upfront installation cost per kW. Can be a 10x difference in nuclear projects based on who’s doing it (some notoriously overbudget projects)

Interesting Tidbits

  • Total electricity production is ~100GW in France. But total electricity needs if everything is on is 4-5x. But that’s why we have networks – to mutualise
  • Photosynthesis takes in 120 billion tons of CO2 per year
    • Energy transformation from sunlight to glucose is 0.5%
    • Some algae do better
  • Materials needed for different electricity generation sources. Important to remember that when you go from “concentrated” sources to “diffuse” (variable) sources like wind & SV you get 10-100x increase in materials needed to get the same energy output. And these materials are created with heavy use of fossil fuels as we saw previously. Something to keep in mind for whole CO2 footprint of a source
  • The two big renewable energy sources are hydroelectricity and biomass. The reason is that they can store energy (in a reservoir and in wood respectively) which wind & solar don’t have.
  • For those you need forests and mountains.
  • If you are in a flat and densely populated country very difficult to do much renewables. Explains this:


  • Renewables excl nuclear are 14% of primary energy worldwide today
    • 10% biomass
    • 2% hydro
    • 2% other
  • It’s going to be very difficult to scale renewables 10x which is roughly what we need to have a fully decarbonised energy system by 2050
  • For all of them (hydro, biomass, solar, wind, agrofuels) we will fast run into resource contention on land (and on mountainous areas & lakes in the case of hydro) which is being used for agriculture, subject to the NIMBY problem etc. These sources are all very land-hungry
  • Solar and wind have the added downside of being very expensive to install factoring in the storage & network scaling costs due to their variability
  • There are also significant material costs to their installation, and we have to remember that for the time being these materials have a high carbon footprint

Summary of Part II

  • If global CO2 emissions MUST go down by 3x eventually (either because global warming compels us to, or because fossil reserves run out) one or more of these terms must go down
    1. Carbon intensity of the energy supply
    2. Energy intensity of GDP
    3. GDP per capita
    4. Global population
  • For (1) Despite lots of activism, CO2 per KWh of primary energy is flat over the last 18 years
    • Nuclear is the most decarbonised energy source, it runs anytime we want, and doesn’t need much land. Political / public opinion hurdles. China & South Korea going big.
    • Other renewables are 14% of primary energy worldwide and will be difficult to scale significantly. Will hit land contention & cost limits.
    • Also remember electricity generation is only 19% of total energy use (which is why we also need to electrify transport and heating as much as possible)
  • For (2) reducing energy intensity is happening but unlikely to bring the scale of change we need (for democracy / political leadership reasons & and because when things are more efficient demand change, eg cars getting 2x bigger as they got 2x more efficient!)
  • Big modifications in (3) and (4) are mostly taboo for good reasons

… and, rejoice, there will actually be a Part III. Janco has a last lecture on how to do carbon accounting, and some industry case studies from his work as a consultant… coming soon!


All the below in French:

  1. Youtube playlist (20 hours) – audio only
  2. Slides
  3. Resumé du cours (30 pages, en Francais)


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