Lockdown measures taken to combat Covid-19 in March led to a much greener and cheaper electricity system in Britain in the weeks that followed, but at the same time the increased reliance on renewables made managing the grid far more challenging, offering a glimpse of the UK's future power requirements as the economy transitions towards net zero emissions.

That is the conclusion of independent research released today by Imperial College London and energy firm Drax, which saw experts assess the tumultuous impact of the coronavirus crisis on Britain's electricity system from April to June 2020, a period characterised by near historically low levels of demand for power.

As offices and factories shut up shop and millions of people were furloughed or working from home across the country during the second quarter of the year, electricity demand plummeted and renewable electricity took up its highest ever share of the energy mix, leading to record low CO2 emissions from the grid.

The situation reduced the need for fossil fuel power such as coal and gas, and also led to curbed demand for nuclear power, as cheaper forms of renewable power such as wind and solar shouldered the lion's share of Britain's electricity needs. At one point, renewable electricity sources provided almost 70 per cent of Britain's electricity, according to the research.

As a result, the carbon intensity of the grid averaged just 153g of CO2 per kilowatt hour (g/kWh) over the three month period, the lowest level on record, the experts said. At the same time wholesale electricity prices also fell dramatically by 42 per cent as a result of plummeting power demand and the low marginal cost of renewable power.

However, the report also highlighted how record low demand for power combined with high levels of intermittent renewable energy sources posed new challenges for Britain's grid operators, resulting in costs of around £100m a month as operators were forced to incentivise generators to take to power plants offline to help stabilise the system.

While grid balancing costs have typically made up around five per cent of wholesale power prices on average over the past decade, the new analysis estimates that balancing costs rose to around 20 per cent of power prices during the lockdown period, as National Grid ESO moved quickly to ensure appropriate supply and demand at all times in order to keep the lights on.

As such blackout fears proved unfounded, but the costs of managing the grid skyrocketed to a record high of £718m in the five months after lockdown measures kicked in, Ofgem revealed earlier this month, prompting the regulator to announced a review of grid management firm National Grid ESO's actions over the period.

Lead author of the analysis, Imperial College London's Dr Iain Staffell, said the impacts of Covid-19 underlined the need for far more flexibility on Britain's grid in order to more efficiently balance supply and demand, such as through battery storage and AI-based grid management systems.

"The past few months have given the country a glimpse into the future for our power system, with higher levels of renewable energy and lower demand make for a difficult balancing act," he explained. "To help the country decarbonise further it is vital that flexible technologies which provide power and system stability play an increasing role in our grid."

Nevertheless, the disruption of Covid-19 led to a number of green grid records over the period, demonstrating the increasing importance of wind and solar in the UK, which the government last week confirmed are now the cheapest forms of new power generation available.

Today's research shows electricity output from wind, solar, and biomass were each up more than 10 per cent during the second quarter of 2020 compared to the same period last year, while Britain also achieve an unprecedented 67 days without coal power on the grid between April and June - a run that was only broken thanks to the need to operators to undertake technical checks at one of the UK's coal plants

The government's long-awaited Energy White Paper is expected to offer more clarity for the energy sector over its plans for grid flexibility technologies, as well as its vision for how the electricity system will interact with green heating and transport technologies such as electric vehicles. Prime Minister Boris Johnson recently signalled that the Energy White Paper will have a key role to play in supporting the government's plans to deliver a "whole systems approach" to the net zero transition, but a publication date for the long-awaited document is still yet to be announced.

Meanwhile, efforts to build further renewable power capacity in pursuit of the UK's 2050 net zero target are continuing, particularly in the UK's burgeoning offshore wind sector, which saw a flurry of project announcements last week.  

Observers are also hoping that the Energy White Paper will provide further clarity on the government's plans for the nuclear sector, alongside its vision for renewables and smart grids.

A raft of new nuclear projects have been shelved over the past year with developers arguing they need a clearer route to market. The uncertainty dogging the sector was further highlighted late last week by the news that EDF Energy's Hunterston B facility in Scotland is set to close in 2021, a year ahead of schedule, following reactor problems.

The move has sparked fresh calls from the nuclear industry and some unions for the government to provide clarity on how new reactors can be delivered, warning that without new nuclear power plants to replace retiring reactors new renewables capacity will simply replace old nuclear capacity while gas generation will continue well into the 2030s and beyond.

Gary Smith, Scottish secretary of the GMB union, told the BBC that the closure of Hunterson B was "a defining moment in terms of energy policy". "The political aspiration is for a low carbon future but politicians have no credible way of delivering it," he said. "This announcement ensures that we will be more dependent than ever on fossil fuels, largely imported gas."

But Dr Jonathan Marshall, head of analysis at the Energy and Climate Intelligence Unit (ECIU) think tank, argued that as older nuclear power plants come offline, their capacity should be replaced with "quick to build" and increasingly cheap renewable energy sources.

"Setting ambitious targets for onshore wind and solar, as seen for offshore wind, would ensure that there is more than enough clean energy to power our lives," he said. "While a decision on nuclear power funding is expected in the upcoming Energy White Paper, for now the clear answer is to crack on with the solutions that can be delivered reliably, rapidly and at rock-bottom costs."

The coronavirus crisis provided a snap shot of how the grid can operate reliably with a significant and increasing reliance on renewables, delivering major emissions savings in the process. But it also confirmed how grid balancing costs and the role of nuclear power will become ever more pressing issues as the grid continues to decarbonise. The issues highlighted by the lockdown are not insurmountable, but they do need fresh policy interventions and clear leadership if they are to be addressed. The general consensus from every corner of the UK energy industry is that the long-promised Energy White Paper cannot come soon enough.