By Professor Hongjian Sun
On UK roads in 2019, cars and vans were driven 333.7 billion miles[i] by burning petrol and diesel. This distance is equivalent to about 1,800 round-trips between the Earth and the Sun. This generated a massive amount of carbon emissions and air pollution. Banning sales of new petrol and diesel cars by 2030 is an ambitious step by the UK government towards tackling the climate crisis.
In the next couple of decades, these petrol and diesel vehicles will mostly be replaced by electric vehicles (EVs), powered by electricity coming from power systems. Through increasing the levels of low-carbon and renewable energy generation in power systems, the UK could become one of the first countries to achieve the 2050 target. But there are several things we must do to deliver net zero emissions rapidly and securely.
Upgrading power systems
Electrifying transport, together with heat decarbonisation, will likely double current power demand[ii], meaning more low-carbon and renewable energy sources (RESs) have to be connected to power systems. But the intermittency of RESs may compromise power system security.
The blackouts in August 2019 warned us of the increasing likelihood of power disruption caused by inadvertent tripping of RESs.[iii] Moreover, more and larger power demand spikes could appear in the future, e.g., as a result of cold weather requiring more heating or large events requiring more transport.
These changes pose new threat to the power system security. Hence, power networks will need to be sufficiently reinforced whilst monitored with pervasive sensors to avoid catastrophic failures.
Smart charging
EV charging could become one of the main contributors to power demand spikes. For example, when 100 rapid chargers (operating at 43-120kW) are simultaneously used in a local network, at least 4.3 MVA additional demand (about 20% of the power rating for a typical transformer that serves thousands of households) will be added to existing power load. The distribution network or transformer may not be able to handle this EV spike.
Additionally, fluctuations in power generation could make it more difficult to balance demand and supply. Hence, smart charging solutions are needed for delivering precise EV charging and synergising with intermittent RESs so that the use of both EVs and RESs can be scaled up.[iv]
Smart charging can be approached in different ways, for example:
- Peak shaving (flatten peak load) coordinates EV charging to avoid charging at peak demand time, or uses EVs’ batteries to provide additional power supply to the grid to meet peak demand. This approach can reduce operational cost, as power networks and equipment are typically sized according to peak demand.
- Smart tariffs provide different price incentives to EV users for balancing supply and demand. When supply is greater than demand, lower prices can be published to encourage charging, and vice versa.
- Green charge aims to maximise the use of green energy.[v] EV users are encouraged to charge when more renewable energy is being generated (e.g., on a sunny day) or the energy’s carbon intensity is low (e.g., when there is low demand and less gas in the energy generation mix).
- Peer-to-peer (p2p) energy trading enables a household with surplus solar energy and a spare parking space to sell energy to a visiting EV. This approach has the potential to mitigate the imbalance of supply and demand with the least changes to the power network.
- Home energy management makes use of energy storage to store surplus solar energy whilst scheduling EV charging to minimise the consumer’s bill. Household energy demand can be adapted to better respond to the fluctuations of RESs.[vi]
However, smart charging is not yet available in the UK market. Some R&D projects are performing trials and the UK government is interested in developing proper regulations, and recently published a public consultation.
What we do know is that 2025 will be a crucial year for decision making. Currently, a new type of energy actor, ‘charging operator’, is defined in UK law for realising smart charging, but this will also require effort from device-level manufacturers. For p2p trading and home energy management, other actors might need to be defined, such as home energy operator or EV aggregator.
It is also not yet clear whether existing EVs will need to be retrofitted to participate in smart charging. Technically it is possible for smart charging to be managed by the charging points themselves, but this too will depend on regulation.
Discharging EV batteries to support the grid during periods of peak demand may also shorten the life of each battery, so carefully designed regulation and ownership models will be required to incentivise the use of this model.
This collectivised use of EV batteries could help to support the expansion of RESs and EVs within the UK’s fair share of the critical materials required to produce batteries. As such, smart charging is another area (in addition to shared mobility[vii]) in which the UK will need to support regulatory and cultural shifts towards greater sharing, to ensure that transport can be decarbonised everywhere.
[i] Department for Transport, ‘Road Traffic Estimates: Great Britain 2019’ https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/916749/road-traffic-estimates-in-great-britain-2019.pdf
[ii] National Grid ESO, ‘Future Energy Scenarios (FES)’ July 2020. https://www.nationalgrideso.com/document/174541/download
[iii] National Grid ESO, ‘Technical Report on the events of 9 August 2019’. https://www.ofgem.gov.uk/system/files/docs/2019/09/eso_technical_report_-_final.pdf
[iv] John Heron (2020) Towards ‘Smarter’ Systems: Key Cyber-Physical Performance-Cost Tradeoffs in Smart Electric Vehicle Charging with Distributed Generation. Doctoral thesis, Durham University. URL: http://etheses.dur.ac.uk/13788/
[v] Harry Humfrey, Hongjian Sun, and Jing Jiang (2019) ‘Dynamic charging of electric vehicles integrating renewable energy: a multi-objective optimisation problem’, IET smart grid, 2 (2). pp. 250-259. https://ieeexplore.ieee.org/document/8752577
[vi] Daniel Gosselin, Jing Jiang, and Hongjian Sun (2017) ‘Household level distributed energy management system integrating renewable energy sources and electric vehicles.’, in Proceeding of IEEE 85th Vehicular Technology Conference (VTC2017-Spring): 4–7 June 2017, Sydney, Australia, pp. 1-5. https://dro.dur.ac.uk/21342/
[vii] Marsden, G., Anable, J., Bray, J., Seagriff, E. and Spurling, N. (2019) ‘Shared mobility: where now? where next? The second report of the Commission on Travel Demand’. Centre for Research into Energy Demand Solutions. Oxford. ISBN: 978-1-913299-01-9 https://www.creds.ac.uk/publications/where-now-where-next/