First published in the New Scientist, 7 July 2011.

Chancellor Angela Merkel’s government claimed to be “ushering in the age of renewables” as German MPs passed legislation this week to phase out nuclear power by 2022 – but the basic arithmetic of the energy-switch policy suggests the country will struggle to fill the hole left by nuclear power – and emissions may rise in the interim.

The vote means that by early next decade Germany will lose 20 gigawatts of nuclear power, which supplied the country with 23 per cent of its electricity last year. Renewables supplied Germany with 17 per cent of its electricity in 2010, so the country generated 40 per cent of its electricity from zero-carbon sources.

Under existing targets, which pre-date the nuclear U-turn, the government plans to double renewable electricity to 35 per cent by 2020. In fact, in its Renewable Energy Action Plan submitted to the European Commission last year, Germany projected that renewables could deliver almost 39 per cent by that date. That was on the basis that gains in energy efficiency would cut demand by almost 9 per cent, which may not be achievable in a growing economy.

Either way, it seems unlikely that electricity from renewables alone can completely replace the 40 per cent of electricity now generated from a combination of nuclear and renewables before the last nuclear station closes. That’s because renewables require far more generating capacity than the technology it replaces as wind and solar are intermittent.

Germany will plug the gap by building coal and gas-fired power plants with a combined capacity of 20 gigawatts for cloudy or windless days. Opposition to carbon capture and storage in Germany – where the technology is seen as an excuse to justify continued reliance on coal – means the carbon emissions from these plants may not be collected.

So it looks as if the country will at best have about the same level of zero-carbon generation in 2020 as today – 40 per cent – and that emissions will rise in the interim.

Had Germany been prepared to retain its nuclear capacity and achieved its renewables target, the zero-carbon share could have risen to 58 per cent.


  • Amazed to see you describing nuclear energy as zero-carbon. You should be aware that there have been numerous assessments of the emissions associated with nuclear power generation, since the actual fission is about the only stage in the nuclear power lifecycle that doesn’t produce emissions.

    Estimates that I have seen range from around twice the emissions associated with wind/wave/solar to over ten times. They’re not hard to find.

    • Shaun, this point is often claimed but seems to be completely wrong. See a paper entitled ‘Life cycle energy and greenhouse gas emissions of nuclear energy: A review’, by Manfred Lenzen, a physicist at the University of Sydney, published by Energy Conversion & Management, 2007.

      From the abstract:

      ‘The most popular reactor types, LWR and HWR, need between 0.1 and 0.3 kWhth, and on average about 0.2 kWhth for every kWh of electricity generated. These energy intensities translate into greenhouse gas intensities for LWR and HWR of between 10 and 130 g CO2-e/kWhel, with an average of 65 g CO2-e/kWhel.
      ‘While these greenhouse gases are expectedly lower than those of fossil technologies (typically 600–1200 g CO2-e/kWhel), they are higher than reported figures for wind turbines and hydroelectricity (around 15–25 g CO2-e/kWhel) and in the order of, or slightly lower than, solar photovoltaic or solar thermal power (around 90 g CO2-e/kWhel).’

      So, you’re right nuclear is not strictly zero carbon, but by the same token neither are wind, hydro or solar. If you consider solar to be low carbon, according to this paper – a review of the literature – nuclear is lower.

      This reference wasn’t hard to find either.

  • Shaun / David

    Do these studies assess the full lifecycle of power generation capability in terms of the amount of carbon emissions of the construction activities, maintenance and de-commissioning?

    For instance, I often find it quite infuriating to read about zero emmission electric cars / hydrogen buses as if this fully neutralises any environmental complaints. In fact a considerable amount of fossil fuel energy has been consumed in constructing the vehicles, ferrying the workers to the manufacturing plant, powering their lavish lifestyles, and consequently causing unwanted emmissions.

  • Hi David,

    Thanks for the new (to me) reference – as you say, not hard to find at all 🙂

    But it appears to be a perfect example of the kind of research I was referring to. In the section you quote above, Lenzen states that average lifecycle greenhouse gas intensities for nuclear are 65 g CO2-e/kWhel, while wind and hydro come in at around 15–25 g CO2-e/kWhel.

    As I said, “estimates that I have seen range from around twice the emissions associated with wind/wave/solar to over ten times”. This report doesn’t seem to justify calling that “completely wrong”.

    Good to see these figures on solar though – that was news to me, and when I have a chance I will read more of his methodology. My initial suspicion would be though that the carbon-intensity of renewables is quite likely to drop as the technologies mature, while nuclear’s may well rise with exploitation of lower-grade ores, especially if there were a ‘nuclear renaissance’.

    I certainly wouldn’t consider that report any kind of justification for terming nuclear ‘zero-carbon energy’, which you appear to agree with, so why use the term in your articles? ‘Low carbon’ ok, but zero carbon energy? That seems a bit of a misnomer all round, unless we’re talking negawatts 😉

    And I do often make the same point to over-zealous renewables advocates!

    Russell, the study is available here:

  • Richard Smith

    If there is a nuclear renaissance we would start converting spent fuel into new fuel using breeder reactors, so we would not need to mine low grade ores for hundreds of years. Also thorium reactors would make use of so far unexploited high grade ores.

    When we talk about coal power plants, people look at the vast amounts of carbon they produce and tend to ignore as insignificant the carbon used to build the plant. They also ignore the radioactivity that the coal plant produce. (Currently twice to three times a nuclear power plant and this will only rise as the coal plants burn poorer quality coal with more radioactive impurities.)

    Anyway, rounding off to to the first (and second?) order of magnitude measurements, compared to a coal plant, nuclear is zero carbon. So really, how much is is lost with this simplification?

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