Nottingham City Transport: Trent Bridge Depot, Phase 1
In March 2022, Nottingham City Transport (NCT) was awarded £15.2m of Department of Transport ZEBRA funding to transform its historic, partially listed depot at Trent Bridge to a fully electric depot. This is part of NCT’s overall goal for a 100% electric fleet by 2034, which will avoid 3,800 tonnes of CO2e every year once fully delivered.
In this case study we will demonstrate how we work with operators to simplify some of the complex processes around fleet and depot electrification, reduce upfront costs and minimise operating costs.
Introduction
Following a competitive tender, Zenobē was named as Principal Contractor to deliver end-to-end electrification of the operator’s depot, one of the largest projects of its kind to be executed in the UK.
This was also the UK’s largest ever single electric vehicle bus fleet transaction, helping the operator lead the way in the transition to a zero-emission fleet.
Project overview
Through a public procurement exercise, NCT selected Zenobē as its electrification partner. Zenobē completed Phase 1 in May 2024, with on-site infrastructure work completed on time and on budget. Phase 2 has a target go live date of November 2024.Zenobē’s key responsibilities included:
- Completing final designs of the depot, based on site visits and consultations with heritage experts and engagement with the local teams
- Completing a peak power analysis and proposing a charging strategy based on available grid
- Bringing power to site (assessing options, supporting NCT’s decision making process on best approach)
- Installation and commissioning of infrastructure (plinths, transformers, LV panels, chargers, trenching, cabling, containment and ductwork, task lighting)
- Integration of electric vehicles and infrastructure
Challenges
Designing electrical infrastructure for a listed building:
The south section of Nottingham City Transport’s depot is a heritage-listed building. We consulted with a team of planning advisors to ensure that the electrification design is in line with requirements, would be sympathetic to the style and architecture of the building and would be approved by the local council. Examples of the implications to be considered, include:
- Minimising works that would impact the existing listed structure
- Ensuring that no cabling was visible from the outside of the listed building
- Minimising reverse parking which, following a risk assessment, presented a higher risk of damaging the listed part of the building. This reduced options for the parking plan and meant that a space-saving solution was required
Weak existing roof structure in the north garage:
The weak existing roof structure required us to use our supply chain of structural engineers to produce feasibility studies followed by detailed construction designs during delivery. This minimised construction risk and ensured we delivered the project on time and within budget by avoiding unknowns existing prior to delivery.
Working with both space and commercial constraints:
In the north garage, we worked with the existing fabric of the building to make space for charging infrastructure. This included clearing four bricked up arches to create spaces for chargers. However, there were more severe space constraints in the south garage and less flexibility given its listed status.
On reviewing the options and leading a cost benefit analysis of different charger types, we designed a mixed infrastructure solution in the garage that minimised costs (space-saving solutions are up to 50% more expensive per gun than standard) while also maximising the space available.
Potential regret costs for future electrification plans:
After phase 2 is complete, there will still be 30 diesel buses running from the South Garage which will eventually need to be electrified. We consulted with the operator and designed all equipment including private substations and LV panels to be expandable and eventually meet the full depot’s electrification needs.
Complicated and potentially costly grid connections:
There were unique challenges in bringing the required two 1800kVA grid connections to the site. The primary substation was a 1.8km cable route from the site, which needed to pass over a canal bridge and a railway bridge, each with their own specific design requirements – all of this meant additional cost. To reduce costs to the customer, we negotiated and procured the contestable element of the grid connection works, obtained prices from a range of Independent Connection Providers (ICPs) and asset values from a range of independent Distribution Network Operators (iDNOs) to significantly lower costs for NCT.
Construction in a live depot environment:
Similar to our approach with Oxford Bus Company at their Cowley Depot and at National Express’s Coventry depot, we, in consultation with the operator, phased the construction so that all services could continue running throughout the delivery programme. Given the impact of shutting down parts of the depot on day-to-day operations and health and safety risks, we collaborated closely with the local team to mitigate any problems and communicate changes. All onsite works were completed on time.
Working with additional suppliers:
During the build process, Nottingham City Transport requested the addition of specific fire suppression hardware to be retrofitted onto the chargers installed on-site as an extra layer of safety. We worked with NCT on the procurement of this equipment and project managed the retrofitting of these chargers whilst ensuring warranties were not compromised.
Minimising ongoing operational costs:
Charger leads are expensive to replace so we worked with the customer to review several lead protection options to minimise ongoing costs. The final design includes a charger cable ‘basket’ that reduces the risk of trailing leads in the depot, which can easily be run over and damaged.
Our smart charging and load management system has also been installed at the site to optimise vehicle charging windows in the most cost-effective and operationally efficient manner.
Results
Phase one of the electrification of Nottingham City Transport’s Trent Bridge depot is now complete, with phase two in progress. 30 fully electric single deck Yutong buses are now in operation from the depot with more to come in 2025, as phase two comes to completion.
“Nottingham City Transport has been committed to reducing its emissions for several years and has trialled and used a number of alternative fuels since 2007, starting with ethanol buses and more recently our bio-gas double deckers. Electric buses are the next obvious step on our journey, enabling our continued support of the city’s aim to be carbon neutral by 2028.
As a new technology and “fuel” for NCT, we have valued and benefited from the support, knowledge and expertise that our partners in the project, particularly Zenobe, have been able to provide during the planning, installation and introduction of our electric single deck buses. It has been a huge team effort and we thank Zenobe for the important part they have played in achieving our ambitions.”
– Anthony Carver-Smith, Head of Marketing and Projects
In numbers
grid connections
Zerova DC Chargers installed (Phase 1)
Yutong single deck buses supported (Phase 1)
