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The changing power mix means nuclear can no longer rely on the old concept of baseload power


The outdated baseload concept It was the case that the price of nuclear-generated power was fairly predictable – if not always the cheapest option. It presents a different risk profile compared with thermal plants, which are relatively cheap to build but whose actual ‘cost to generate’ depends heavily on the fuel price. The link with fuel costs has dramatically altered the use of thermal plant in both long and short term. For example, the discovery of gas resources in the 1980s and 1990s meant it became a fuel of choice and we are still living with the switch to gas turbines that resulted – and the consequences of the dramatic changes in gas supply that followed Russia’s invasion of Ukraine. That recent experience is helping make the risk profile of high capital cost, low fuel cost, plant like nuclear more attractive. But it makes renewable energy sources even more attractive, because they also offer low running costs but their build profile is one of relatively small units installed quickly, so that even multi-gigawatt scale wind farms can be built in phases that allow generation of power – and revenue – within a few months. The changing power mix means nuclear can no longer


rely on the old concept of baseload power. In fact 2025 will mark a decade since Steve Holliday, then the chief executive of GB’s system operator National Grid, dismissed the idea of baseload in an interview for the World Energy Council. Back in 2015 he said “this is an industry that was based on meeting demand. An extraordinary amount of capital was tied up for an unusual set of circumstances: to ensure supply at any moment.” Holliday was speaking at an earlier stage of the rollout of


renewables. Since then the renewable rollout has increased by orders of magnitude. Offshore wind turbines have stepped up in size from 3 MW to 16 MW and are still growing, and offshore wind arrays are typically planned in the single or multi gigawatt scale. But Holliday also pointed out the potential at small


and local scales: “The idea of baseload power is already outdated. I think you should look at this the other way around. From a consumer’s point of view, baseload is what I am producing myself. The solar on my rooftop, my heat pump – that’s the baseload. Those are the electrons that are free at the margin.” Holliday’s prediction has come to pass, as the cost of solar PV has continued to tumble (see box) and deploying it has become familiar for both domestic and business customers. Some scenarios see ‘PV everywhere’ in future. That will alter long-established profiles for business and domestic use as ‘behind the meter’ PV meets some or


all of the user’s needs, but it will also add to the volatility to be managed as generation rises and falls with daylight hours and with local weather.


Ancillary services and nuclear Nuclear has to prepare to lose its ‘baseload’ customers and consider how it can satisfy different customer needs in a very different power industry. Who will be nuclear’s future customers and how can it meet their needs? Clearly flexibility will be at a premium. But Holliday also


said, “I believe there will be different answers for different places, rural and cities, and for different customers.” That tends to suggest that the industry’s move towards


small modular reactors (SMRs) is the right one, and that is only partly because of the need for flexibility in power level. SMRs also allow for geographical flexibility. System operators need flexibility – upwards as well as


downwards. The electricity network is built around the characteristics of thermal power plant, and without such plant on the system it is harder to maintain system stability. Thermal plants’ heavy rotating generators are useful in provide physical ‘inertia’, which tends to pull the supply back towards its defined operating frequency. They can help manage voltage levels, by either absorbing ‘reactive power’ or producing it. Sometimes, in a system that has high levels of renewables, on a day with sun and wind renewables can supply most of the energy required by users. As a result the system operator may ask users to increase their power demand, so it can bring thermal plant into action to provide those services – alternatively it has to constrain off renewables, often the cheapest plant on the system, to bring the necessary thermal plant online. In the case of voltage support, the requirement is


location-specific so it requires distributed generating sources (or other types of flexibility) and because it is determined partly by the types of local demand and whether they supply or absorb reactive power, it may change over time. All these specific requirements should tend to benefit


SMRs, because they have more flexibility over siting and a shorter lifetime. Nuclear has to be willing and able to provide these


services, as well as flexibility for the system operator or to meet large customers’ needs around their self generation. That flexibility has proved problematic in the past, not so much because of technical incapacity but because the economic balance has not been in its favour. Currently, a flexibility payment has to be substantial and


www.neimagazine.com | April 2024 | 17


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