Optimise Prime: Electrifying fleets without breaking the grid?


Distribution network operators and fleet companies are working out how to enable the EV transition without simply resorting to grid upgrades. The Optimise Prime trial hopes to enable a smarter approach. The Energyst spoke with Sung Pil Oe, innovation project lead at UK Power Networks, on progress to date.

Optimise Prime is the world’s biggest trial of commercial EVs. The £34.7m project, funded via energy bills under Ofgem’s innovation allowance, aims to understand – and minimise – the impact that the electrification of commercial vehicles will have on distribution networks. 

Led by Hitachi Vantara and UK Power Networks, the four year project will involve up to 3,000 EVs from Royal Mail, British Gas and Uber, supported by Scottish and Southern Electricity Networks, Hitachi Europe and Hitachi Capital Vehicle Solutions.

Big shifts

The project is strategically important, because fleets are starting to drive EV adoption curves says Sung Pil Oe, innovation project lead at UK Power Networks.

“Some of the biggest fleets operate tens of thousands of vehicles, so they could be transitioning significant volumes in one go.”

That is evidenced by Centrica, owner of British Gas, in July placing an order for 1,000 EVs. The partners have agreed to bring forward their investment plans for EV as part of the project with Royal Mail also procuring additional electric delivery vans as part of Optimise Prime.

“There is also a gap in understanding how commercial vehicles will be charged, their charging profiles – because most trials to date have focused on residential users,” says Oe. “So as a result of the trial, we will collect the largest dataset on the network impact posed by commercial vehicles – and it will be made publicly available.”

The trial looks at both return to home fleets and return to depots. The latter is likely to pose the greatest capacity challenges, given the concentration of charging in one place. However, the former aims to determine how distributed EVs could be used to provide flexibility services to meet network needs as well as examine how to automate the process for employees to claim back expenses for charging company EVs at home.


Royal Mail, which has 48,000 vehicles on its fleet, is the return to depot partner. It told The Energyst it is currently waiting for its smart load management system to be deployed by Hitachi. Until that happens, it was unwilling to provide comment on its EV experience to date for this report.

Project delays, relating to vehicle availability and delivery of some of the technical solutions, have been exacerbated by Covid-19 disruption.

While now looking likely to complete up to a year behind schedule, the partners hope it will ultimately deliver planning tools that assist fleet managers in transitioning to EVs.

Base loads

Oe says the Depot Charging workstream should enable fleet managers to better understand aspects such as the number of chargepoints required, their rating and background load demand already on site, and overlay that with operational schedules to optimise charging requirements.

“It will take into account any onsite generation or storage, and flexible assets such as EVs to optimise a site’s energy requirement and produce a profile which can then be used to apply for a profiled connection – which is another product that we are offering as part of the trial,” Oe explains.

A profiled connection is a type of flexible connection – which will allow DNOs to maximise utilisation of the existing network capacity. By matching a site’s profile and charging schedule with network constraints, the aim is to create a smart charging system that benefits both vehicle operator and network operator.

Power trades

The trial also aims to understand the flexibility services fleets such as Royal Mail could provide.

“If a depot takes a profiled connection, and has optimised as a result, is there residual flexibility that can be provided to the DNO on top of that? If so, it could be used to provide additional revenue streams for customers – and that’s something we want to explore as part of the project,” says Oe.

“The ability to understand the value of flex for different types of EV fleets is an important aspect of the trial. If the value is proven then it will increase liquidity in the flexibility service market by allowing commercial EV fleets to participate.”

Tech challenges

The capital hurdle of creating enough capacity to electrify depot-based fleets can be a challenge for operators. But it is not always the wider network that requires reinforcement, says Oe. “It could be the last mile cable feeding their site, which is classified as a sole use asset rather than a shared use one.” So while some fleet operators may think they can avoid associated costs by taking a smart or flexible solution, “that element should not be overlooked,” says Oe. “There may be some unavoidable costs.”

Equally, while smart control systems can be remotely managed, “there are elements where a fleet operator needs to understand their baseload, any flexible assets and the operational requirements of their vehicles to gauge the optimised connection required for that site,” he adds.

Asked to summarise advice to any fleet operators considering a switch to EVs, Oe is succinct: “Distribution network operators are happy to support people, we want to find smart solutions, but early engagement is key.”

Free download: The 2020 EV report

This article is one of a number of in-depth interviews conducted for The Energyst’s new 2020 EV report. It contains expert insight across a range of sectors, plus a survey of more than 300 firms around EV charging infrastructure plans.

Sponsored by Arup, EDF, Good Energy, New Motion and Total Gas & Power, the report also includes views from: Arval, Cenex, DPD, Dreev, Engenie, ev.energyHitachi Capital Vehicle Solutions, Mitie, National Grid, Nottingham City Council, the John Lewis Partnership, TLT, UPS and Western Power Distribution. Download the report here.


  1. Optimise prime is rightly concentrating on small commercial vehicles such as EVs owned by companies like Royal Mail and British gas, but when it comes to heavier vehicles such as busses, HGVs and trains the extra weight of the batteries makes them less attractive to power by battery alone, and this is the point when fuel cell electric vehicles (FCEVs) become more cost effective as they are powered by hydrogen that can be refueled in a similar time as petrol and diesel vehicles. The basic point is that all our power needs to be first generated as zero carbon electricity, which can either be stored directly in an EV battery, or for a greater energy storage needed for larger vehicles, as hydrogen powered FCEV. When a vehicle is used 24/7 then using hydrogen is even more attractive than battery power, which is seen in distribution warehouses that operate 24/7 which can keep their fork-lift trucks working most of the time by avoiding the long time to recharge them. Hydrogen dispensing points can be easily installed in existing filling stations, whereas recharging points need more space for the EVs to park while recharging.

    • Transport for London is buying new hydrogen double decker buses because night buses are in service 23 hrs a day, 1 hr isn’t enough time to charge new electric double decker buses which take 4 hrs to recharge, costs electric £350,000, hydrogen £500,0000 double decker bus, so to replace 0ne diesel night bus with two electric buses is 2x£350,000=£700,000, £200,000 more than one hydrogen bus.

      • Hi Jason. Nice figures, however the bottom line is that when the vehicle is larger than a car or a small basic van, it’s less expensive to have hydrogen power over battery, because you can keep it working for longer. The increasing number of hydrogen powered busses will bring down their cost, and their cost of maintenance is much less than diesel. Ryse Bus (a JCB company) plans to build 3,000 H2 busses a year as well as hydrogen fuelling stations for them. Over the next 10/15 years it will become less expensive to own and run a hydrogen bus than a diesel one.

  2. There is no mention as to whether v2g will be used. Last week Bus2Grid world’s largest vehicle-to-grid trial site was opened at Northumberland Park bus depot, London that connects 28 electric double decker buses to the grid with a 1MW output, In 2021 700 electric buses will be used and if all 9,000 plus London buses become capable of bi-directional charging then 150,000 houses can be powered. Hydrogen buses can be used for v2g but can only send power to the grid not charge from it as the small batteries are only for regenerative braking but TfL new hydrogen double decker buses will operate as night buses in service 23 hrs a day so that is less of a problem,


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