As the world scrambles to counter the threat posed by Vladimir Putin, you might think the last thing we need is more inertia.
But while one definition of that word is “a tendency to do nothing”, it also refers to a process that could play a pivotal role in removing fossil fuels from the UK electricity grid, making the country less reliant on gas supplies, including those from Russia.
The National Grid Electricity System Operator (ESO) is announcing a “trail-blazing” greener way of generating inertia, that if all goes to plan should also reduce carbon emissions, rein in household bills and recoup the £336m investment funding it.
In this context, the word refers to the tendency in physics for objects to continue in a state of rest or motion, unless another force acts on them. A spinning top exhibits inertia, in that it will keep spinning until friction with the ground eventually causes it to stop.
In the electricity system, inertia is crucial in maintaining a stable electrical frequency on the grid, keeping the lights on. In August 2019, more than one million people across the UK were plunged into darkness during one of the worst power blackouts in more than a decade, after the frequency of the grid fell from its usual 50Hz to 48.88Hz.
That unprecedented loss of power generation was caused by a lightning strike, but outages can happen for other reasons too, causing a sudden shortfall that knocks the system’s frequency off kilter.
As things stand, the grid system usually balances itself automatically thanks to the inertia held in massive spinning turbines at coal and gas power stations – much like a spinning top, but 19.5 metres (64ft) long and made of 300 tonnes of steel and aluminium.
They respond instantaneously to a power outage happening elsewhere, spinning ever so slightly slower to offset the disruption and keep the system stable.
However, these giant turbines are not a feature of wind or solar power generation, meaning that as the UK aims to decarbonise the electricity grid by 2025 as part of efforts to hit net zero, inertia needs to come from somewhere else.
The solution, according to National Grid ESO, whose job it is keeps the electricity network in check, is a series of green turbines created to mimic the effect of their cousins at carbon-emitting fossil fuel plants.
With only a small amount of energy fed into them, they can spin at the required rate of 3000RPM, the speed that ensures synchronicity with the 50hz Grid system.
The result, in theory, is a solution to the problem of creating inertia in an increasingly wind- and solar-powered electricity system, allowing for a faster push away from fossil fuels that emit carbon and line the pockets of countries such as Russia.
In a deployment that puts the UK at the forefront of grid decarbonisation, 2022 is the year these green turbines begin to make their impact. Two got up and running at Keith Greener Grid Park, in Moray, Scotland in late December last year, with four more coming on stream this year.
Rassau in south Wales went live last month, a fourth will start spinning at Killingholme in Lincolnshire within weeks, followed by Grain in Kent and Lister Drive in Liverpool this summer.
“Building a green system with enough inertia is an engineering challenge for system operators worldwide and we’re the first to be solving it,” says the head of networks at National Grid ESO, Julian Leslie.
The ESO believes that it has solved the inertia problem in a way that should make electricity generation cheaper, as well as greener.
It has spent £328m on six years of inertia services from the green turbines, set against the £456m it would normally pay, a saving of £21m a year on the portion of electricity bills accounted for by operation of the grid.
In addition, a further £7.5m has been spent on a pioneering “sonar” tool, which the grid refers to as the world’s first “ultracapacitor”, based on Teesside.
It will send out pulses of energy into the electricity system, precisely measuring the effect on inertia of tiny factors like people using washing machines or vacuum cleaners, in order to ensure grid stability.
“It’s a phenomenal thing that nobody has ever done before,” says Leslie.
Looking ahead, the next stage in the evolution of this process could be even smarter, with inertia produced not by spinning turbines but by little black boxes, called grid forming inverters, that replicate the laws of physics.
The use of these, another world first, could be included in contracts due to be announced in the coming months.
