Blog: Electricity demand during week one of COVID-19 lockdown

31 Mar 2020

As we’ve all now realised, the world is experiencing the most severe pandemic since the 1918 influenza outbreak. The pressures currently being faced by global society are the greatest most of us will ever have experienced, and certainly the greatest outside wartime.

Essential services need to continue. One of those is access to energy. Demand for it in Britain will be significantly shaped by the massive behaviour changes wrought by the lockdown announced by the Prime Minister on the evening of Monday, March 23rd. In this blog, Keith Bell and Graeme Hawker at the University of Strathclyde examine newly accessible data to consider how demand for electricity has changed in recent days and discuss the challenges faced by the electricity sector in ensuring a continuing reliable supply of power.

How has demand changed?

“The grid” in Britain comprises networks that operate at different voltages: the transmission network that covers the whole of the country operates at the highest voltages and carries gigawatts of power on overhead lines that march tens or hundreds of kilometres; and the regional distribution networks that, typically, collect power from the transmission network and distribute it at lower voltages to millions of businesses and homes.

Demand for electricity is heavily influenced by day of the week, time of day and the weather. If we’re going to see what difference the lockdown has made, we ought to compare the past week with the same week last year. However, the weather was comparatively warm this time last year, which will have reduced energy demand, so we would not be comparing like with like. Instead, we compare last week to a reference week selected as that beginning 8th April 2019, which had comparable daily average temperatures, while still being at a similar point in the year (e.g. unaffected by public holidays).

What we find is shown in the charts below, comparing the ‘transmission demand’ – the power taken from the top-level Great Britain electricity grid – from last week with that in the reference week from 2019.

Figure 1 – Transmission Demand by half-hour period for the week beginning 23rd March 2020 and a comparable week in April 2019

More time at home is less at the workplace

While people spending more time at home means there has been an increase in domestic demand, it appears from Figure 1 that this has been more than compensated for by the reduction in commercial and industrial demand from businesses shrinking their activities. Figure 1 shows around a 13% decrease in total electrical energy consumption over the week relative to the reference period.

Compared to the 2019 reference, we see that weekday mornings have been similar to what we might normally expect at weekends, lacking the characteristic surge in demand as people prepare for and begin their working day. This relatively low use of electricity continues throughout the day but, interestingly, the evening peak is similar to normal, suggesting that the pattern of use in the evenings (generally energy-intensive domestic activities such as cooking, space heating, and hot water use) is relatively unchanged. We also note the slightly higher electricity demand on the evening of the 23rd March as the Prime Minister addressed the nation, with a marked change in demand between the Monday and Tuesday as new restrictions were announced.

Figure 2 – Average demand profile for weekdays/weekends for the week beginning 23rd March 2020, against the reference week in April 2019

Weekday use becomes weekend use

Overall, from Figure 2 we can see that this shift in electricity demand patterns means that the average weekday is, now, very similar to what we might expect from weekend electricity use. Saturday lacked the typical morning peak, now looking like a typical Sunday instead. Given that, in normal times, industrial and commercial demand is lower at weekends, this seems to confirm a reduction of activity in those sectors in daytime hours during the week. However, the sizes of the evening peaks for both weekdays and weekends seem much like for the same days in the reference week.

We note two caveats to this comparison:

  • As the data is based on ‘transmission demand’, the transfer of power is affected by the operation of ‘distributed generation’ (DG), i.e. relatively small-scale generation connected within the distribution network. We currently lack the metering in Britain to allow us to distinguish between how much of the half-hourly demand is met by DG and how much by transfers from the transmission system.
  • As the demand presented is net of DG, much of which is wind and solar power, a component of the variance will be due to different wind speeds and solar irradiance between the two periods.

Because of the missing DG component, the above values should be treated as proxies for end electricity demand rather than ‘true’ demand values.

What are the main challenges faced by the electricity network operators?

It can be seen from the charts above that demand hasn’t increased. As we head into the Spring and Summer, we would generally expect it to fall, and it was already at a lower level before the lockdown than it was over the Winter. Normally, that means that there should be plenty of power available and that transfers over the distribution network are within manageable bounds. However, one factor that might make a difference is that, with so many people at home for almost all of the time, there is likely to be less ‘diversity’ in demand. That is, especially around the early evening peak of demand, it’s possible that more people will be using power for similar things at the same time than is normally the case.

The ESO is now doing things they usually don’t want to

Low levels of ‘transmission demand’ over the last few years have already been causing the national Electricity System Operator (ESO) to do things that they would prefer not to: to reduce imports over particular interconnectors or to curtail output from wind farms. These actions are necessary to limit the impact of a fault outage of an interconnector, to create space on the system for other types of generating plant that can help with operating the system or to stay within the capability of the network to export power from one region to another. With the apparent reduction in industrial and commercial demand for electricity, we may see these types of action more often.

Staffing pressures will be a big challenge

All the network companies have, for many years, been key parts of national emergency planning. Probably the greatest challenge to the network companies and their contractors in the coming weeks will be pressures on staffing as individuals, perhaps a great many of them, start to experience symptoms of COVID-19 illness and self-isolate or become seriously unwell. Many of the companies had already implemented home working before the lockdown but access to cyber-secure key IT systems still requires certain staff to be on site. Work out at substations, on overhead lines, underground cables and generators also needs to continue and can only be done on site, out ‘in the field’. Staff are well trained in safe working and will already be adopting safe distancing practices as much as possible.

Planned outages to be prioritised

The lower demand that we see in the late Spring, Summer, and early Autumn means that these months are the ‘outage season’ when generation and network equipment is taken out of service for maintenance. Some outages are also necessary for new construction work to be done safely. All these outages are carefully planned, often many months in advance, so that, in spite of taking individual items of plant out of service, electricity can still be supplied as reliably as in the rest of the year. The companies will almost certainly have been prioritising only the most essential outages to ensure the safe and reliable operation of critical components. Other outages will be postponed for the future, and it may take 2-3 years for them all to be accommodated.

In general, failure to do maintenance eventually leads to an increased likelihood of equipment failure. The possibility of an unplanned outage due to an equipment fault or bad weather is faced all the time, but outages are rare enough that, on average, there is only 1 interruption to electricity supply per customer per year. On the transmission system and the higher voltage sections of the distribution system, there is equipment redundancy meaning that one outage would not impact supply. However, faults at any voltage level need to be repaired as quickly and safely as possible, and this depends on people being available at the right time with the necessary skills.

More senior staff on standby

In the distribution companies, especially, many individuals not working ‘in the field’ still refresh their ‘senior authorised person’ qualifications every year. They are used to being on standby when severe storms are forecast to hit but, as staffing levels become depleted, they may need to be on standby or active in engineering services roles more of the time. The companies will need to have a clear picture of where critical services and the most vulnerable customers are so that, if necessary, restoration of supplies to them can be prioritised. Staff who recently carried out control room or operational planning functions are also being made ready to step back into those roles if called on.

Well placed to ‘ride-through’ energy demand changes

The above means that in operational terms, we should be well-placed to ‘ride through’ the changes in energy demand we are currently experiencing, and there is no evidence that the import of fuels on which our system depends (predominantly natural gas) is facing any constraints. However, our electricity system is undergoing many long-term changes both in transitioning to a low-carbon system and in replacing ageing assets. The priority in the short to medium term is to comply with health advice, safeguard wellbeing and support those who will suffer the loss of loved ones or livelihoods. When we start to emerge from the crisis, the energy system transition will need to resume. It might be helped by some of the different ways of working that many of us are now learning.

 


 

Futher reading:

Read Keith’s blog about the August 9th blackout here

Read Keith’s blog about the outcome of investigations into the August 9th blackout here