BLOG #2 - Busting the myth: EV smart charging and secondary peaks

Posted: 11 Sep 2020

Isabelle Bush

Flexibility Analyst

Electrification will play a key role in decarbonising transport, and widespread electric vehicle (EV) uptake is expected to skyrocket over the next few years. By 2030, the UK stock of EVs could reach between 2.7 and 10.6 million —  equivalent to every 1 in 12, or 1 in 3 cars being EVs, according to National Grid ESO.

This increase in electrical demand will place additional stresses on the grid. To hit our net zero targets, while minimising costly investments in grid infrastructure, the future grid will rely on flexible technologies such as EV smart charging and vehicle-to-grid (V2G) to shift charging to times of low demand.

What is smart charging?

Simply put, smart charging is the intelligent optimisation of EV charging. That is, an algorithm that selects the optimal times for an EV to charge, based on a series of constraints. For example, ‘what are the cheapest or greenest times to charge?’, ‘when are electricity networks least constrained?’, and ‘at what time does the driver need their car ready?’. In practice, this usually means shifting charging away from times of high demand, 4-7pm, to times of low demand, between 11pm-7am.

In Kaluza’s digital ecosystem, the flexibility platform dynamically manages each vehicle’s unique charging profile on a minute-by-minute basis. In real time, the platform decides when it is best to charge an EV — for the consumer, the energy supplier, and the local grid.

In a network context, smart charging offers Distribution Network Operators (DNOs) and Transmission System Operators (TSOs) an effective route to procure flexibility — non-intrusively shifting these new domestic loads away from times of high demand.

With more connected loads comes a challenge

As uptake of automated intelligent charging increases, the diversification of these profiles will decrease. If all EVs are optimised against the same constraints – such as wholesale market price signals – their managed charging will synchronise and this will lose some of the natural diversity that is inherent to people plugging in at slightly different times.

A concern of network operators and market regulators is that this could result in the formation of a new, larger peak load during traditionally ‘low demand’ hours. This is the “secondary peak” – Exhibit 1.

Exhibit 1 -Introducing the smart charging “secondary peak”.
Diversified daily charging load per EV (smart charging, and unmanaged EVs). Data captured prior to onset of COVID-19 restrictions,  1st Oct ‘19 - 22nd Mar ‘20.
Source: Kaluza Data.

Exhibit 1 -Introducing the smart charging “secondary peak”.
Diversified daily charging load per EV (smart charging, and unmanaged EVs). Data captured prior to onset of COVID-19 restrictions, 1st Oct ‘19 - 22nd Mar ‘20.

Source: Kaluza Data.

Smart charging deliverS network benefits at low voltage level

Despite being considered by some to be a challenge, smart charging will present more opportunities than challenges to networks as we transition to a future energy system — both at a household, and LV network level.

Let’s first consider a single household with an EV… 

When EV smart charging profiles are analysed alone, secondary peaks are accentuated and could appear as concerning to networks (Exhibit 1). Instead, when considering total household load (across the home and EV), smart charging shifts load away from domestic peak times. The net effect is a smoothing of daily household demand, and a reduction in total peak load compared to unmanaged EVs — Exhibit 2.

Exhibit 2 - EV smart charging reduces peak total household load —  even with a “secondary peak”
Diversified daily EV charging load (smart charging, and unmanaged EVs), with the household Profile Class 1 domestic load profile, for 2019’s  peak winter day. EV data captured prior to onset of COVID-19 restrictions,  1st Oct ‘19 - 22nd Mar ‘20.
Source: Kaluza Data. Elexon PC1 domestic profile data 2019.

Exhibit 2 - EV smart charging reduces peak total household load — even with a “secondary peak”
Diversified daily EV charging load (smart charging, and unmanaged EVs), with the household Profile Class 1 domestic load profile, for 2019’s peak winter day. EV data captured prior to onset of COVID-19 restrictions, 1st Oct ‘19 - 22nd Mar ‘20.

Source: Kaluza Data. Elexon PC1 domestic profile data 2019.

Now, let’s move from a single home to a secondary substation that powers 1,000 homes…

At a substation scale, the benefits of smart charging are clear. Not only do we see the effects of reduced peak load, but the route to potential financial savings for networks is evident too.

Exhibit 3 shows how smart charging could delay the need for network reinforcement, based on Kaluza’s EV data and assumed network data. For an illustrative secondary substation serving 1,000 homes, the impact of total household load (domestic, and EV demand) against substation headroom capacity is depicted for a peak winter day, and against a central estimate of forecasted EV uptake. The headroom capacity is estimated against an assumed 2020 capacity, 15% greater than the 2020 peak domestic demand alone. 

Without smart charging, a ~5% uptake of EVs (for 1 in 20 homes) could result in breaching LV capacity limits — in this model, expected between 2020-2025. With smart charging, the same network infrastructure could allow, up to 1 in 4 homes, a network-connected EV before today’s LV capacity is breached. Here, this is expected between 2030-2035.

Exhibit 3 - How can smart charging delay network reinforcement? An illustration.
(i) Forecast UK uptake of EVs, incl. a lower, central, and upper estimate.
(ii) Percent additional capacity vs. 2020, for  an illustrative LV substation with 1k households (15% capacity headroom in 2020 vs. winter peak load). Central estimate EV forecast used.
(iii) Total household load for an illustrative secondary substation serving 1k households on a peak winter day. Total household load incl. domestic and diversified EV charging load. Domestic load based on Profile Class 1 domestic load profile, for 2019’s  peak winter day. EV profiles based on Kaluza data captured prior to onset of COVID-19 restrictions,  1st Oct ‘19 - 22nd Mar ‘20. Profiles presented for a 5% and 24% uptake of EVs amongst the 1k households. 
Sources: (i) The CCC 2020, NGESO FES 2019, Accenture 2019; (ii, iii) Kaluza Data. Elexon PC1 domestic profile data 2019

Exhibit 3 - How can smart charging delay network reinforcement? An illustration.
(i) Forecast UK uptake of EVs, incl. a lower, central, and upper estimate.

(ii) Percent additional capacity vs. 2020, for an illustrative LV substation with 1k households (15% capacity headroom in 2020 vs. winter peak load). Central estimate EV forecast used.

(iii) Total household load for an illustrative secondary substation serving 1k households on a peak winter day. Total household load incl. domestic and diversified EV charging load. Domestic load based on Profile Class 1 domestic load profile, for 2019’s peak winter day. EV profiles based on Kaluza data captured prior to onset of COVID-19 restrictions, 1st Oct ‘19 - 22nd Mar ‘20. Profiles presented for a 5% and 24% uptake of EVs amongst the 1k households.

Sources: (i) The CCC 2020, NGESO FES 2019, Accenture 2019; (ii, iii) Kaluza Data. Elexon PC1 domestic profile data 2019

Ultimately, smart charging can delay or in some cases even remove the need for investment in network reinforcement. In turn, these reduced investments lead to reduced network use of system charges and eventually, energy bill savings for end-customers.

Benefits from smart EVs could be further enhanced through V2G technology, as demonstrated by Kaluza in its world-leading domestic V2G trial. V2G technology could reduce domestic load at peak times through a V2G exporting and powering the home. 

Although, here, not considered in the context of electric heat, smart charging is a highly versatile technology. If and when smart charging secondary peaks pose a challenge, the necessary changes to optimisation constraints could be activated through the market signals which smart charging can optimise against. For example, through network charges, flexibility markets, or market prices with locational components reflective of local network needs.

Networks should not be afraid, nor shy away from smart charging and its secondary peaks. Instead, networks should embrace this novel technology. Smart charging will offer an unprecedented level of control over demand embedded in the low voltage networks. This will create opportunities to shift load from the domestic peaks of today, and the new peaks of tomorrow. So what? This will open the door, enabling DNOs to build a smart, flexible and dynamic energy system of the future.

Smart charging and secondary peaks: opportunity or challenge?

Secondary peaks will not present issues to networks for years to come. Crucially, smart charging will instead delay the need for significant network reinforcement — contributing to an estimated total ~£7 BN in whole system cost savings from residential flexibility.

In addition to cost savings, smart charging will unlock numerous opportunities for networks on the LV level: from increasing customer engagement in their energy use, to offering new ways to manage network loads, and even giving increased visibility at the LV network level. 

For Auto OEMs, the ability to offer integrated smart charging solutions will be essential in a rapidly evolving and competitive market for EVs. Consumer benefits of smart charging (financial and environmental), coupled with the expected greater ease of installing a grid connection for a smart charger, will form a major draw for prospective EV customers.

And what about today? Networks must engage with flexibility today, not tomorrow. Critically, networks should work to eliminate the policy and regulatory barriers within  our energy markets. Namely:  highlighting to Ofgem the need for incentives that reward more efficient use of existing infrastructure; strong network charges that incentivise domestic flexibility; and the development of DSO flexibility markets for domestic assets. 

About the Author

Isabelle Bush

Flexibility Analyst

Isabelle is a Flexibility Analyst at Kaluza, working closely with energy suppliers and network operators to understand and resolve the challenges currently facing domestic flexibility. Prior to joining Kaluza, Isabelle worked as a Consultant at strategy consultancy Oliver Wyman, where she primarily worked for financial services clients and on merger & acquisition due diligence. Isabelle has a BA, MEng and PhD in Chemical Engineering from the University of Cambridge.

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