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    Intermittency and the Appeal of Nuclear Energy

    Stockholm (NordSIP) – To boil water, nuclear power plants (NPPs) use fission to split atoms, which releases the energy binding neutrons and protons together inside an atom. The steam generated from the reaction is used to power turbines that generate electricity.

    According to the International Energy Agency (IEA), nuclear power is the second-largest source of low-carbon electricity. It provided 10% of the global electricity supply in 2018, including 30% of total low-carbon electricity. Over the last 50 years, nuclear power has provided half of all low-carbon electricity in advanced economies, according to the same source.

    Unlike other renewable energy sources, such as wind and solar, nuclear energy supply is not intermittent, meaning that it is not dependent on the wind blowing or the sun shining. Instead, NPPs can generate energy at a constant rate. As a result, nuclear power is a more reliable source of electricity than other renewables.

    NPPs also require much less physical space than other renewable power plants, while producing small amounts of CO2 during operations. A 2 GW capacity NPP only occupies about 200 hectares of land (including support functions) and have a significantly better base-load capacity. Meanwhile, a solar farm close to the equator requires 100 hectares to produce 100 MW and only supports roughly 25% of the load factor compared to a nuclear plant, according to the IEA. Finally, Project Drawdown estimates that between 2020 and 2050 nuclear could reduce CO2 emissions by 2.65 – 3.23 gigatons.

    The Intermittency and Flexibility Problem

    The intermittent nature of renewable energy such as solar and wind undermines their appeal as replacements for fossil fuels. Solar and wind farms vary in their output throughout the day, because they rely on the sun to shine and the wind to blow. This creates capacity issues, which must be managed to allow supply to match demand in a timely manner.

    According to a report from the International Atomic Energy Agency (IAEA), as shares of intermittent energy production increase in the electricity grid, the residual demand will become more volatile (i.e. suffer from extreme load variations and unpredictability). The more intermittent issues a renewable energy source creates, the greater the costs and difficulties in reaching supply-and-demand equilibrium. If left unaddressed, the issue of intermittency can undermine the electricity system, putting hospitals, offices, residential areas, at risk of blackouts.

    Unfortunately, at the moment, fossil fuels are making up for the majority of intermittency energy gaps. However, NPPs have already demonstrated their ability to compensate for renewables’ intermittency. The IAEA explains that “in France, for example, NPPs are routinely ramped up and down between 100% and 20% of nominal power twice per day. The total nominal flexible capacity of nuclear units in France is reported to be 15 000 MW, which is sufficient to balance VRE [Variable Renewable Energy] intermittency until 2030.”

    In other words, NPPs can increase electricity outputs when renewable sources are insufficient or decrease outputs when renewables are producing enough electricity on their own. Therefore, addressing the less flexible nature of intermittent energy. Yet, if NPPs are to smooth out the output volatility created by the increase deployment of renewables, more investments are needed. Germany’s nuclear phase-out by 2022, for example, is likely to drastically increase the costs of managing renewable intermittency, according to the IAEA.

    This article belongs to a five-part series on nuclear considerations relevant for climate change. Click here to read the other contributions to this series.

    Image courtesy of distelAPPArath

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