Hubs is a novel microgrid solution for railway stations, first of its kind in the world, to interface with both traction power supply system and local distribution grid to maximize the energy efficiency while providing cost-effective solutions for railway decarbonization. The energy hub will integrate local renewable generation, recover regenerative power from trains approaching stations, and coordinate both traction and non-traction power supplies along the railway routes. The ultimate goal is to implement the energy hub solution to as many of the 2500 stations across over 10,000 miles of UK rail as energy and transport nexuses, connecting these hubs and their surrounding cities/communities to support green mobility and a future low carbon power grid that runs almost entirely on renewable sources.
Benefits
This project is a joint effort from Network Rail and SP Energy Networks together with research and innovation partners University of Leeds and Ricardo in the Ofgem SIF discovery phase and additional new partners Costain and Entrust Microgrid to meet the government’s Transport Decarbonization Plan, including the aim to create a net-zero rail network by 2050. The technology developed through this project may lead to the building of multi-energy hubs around as many as possible of 2500 UK rail stations which will drastically reduce the 2.8MtCO2e produced p.a., by improving energy efficiency, integrating renewable sources, recovering regenerative power from trains, coordinating EV charging, and providing power grid services where possible.
The benefits to key stakeholders include:
- gain tailored solutions for faster and more cost-effective decarbonization - zero carbon stations and depots achievable with savings of more than £32M pa; save electrification investment £2.3Bn or more for over 2,400 km routes deemed unsuitable for electrification.
- Energy hubs enabled by machine-learning assisted digital twin and advanced power electronics facilities will provide cost effective improvements of railway power capacity at stressed regions/regions of weak connections, and for railway electrification and the expansion of services.
- Significantly enhanced traction power supply reliability - even in grid failure conditions the hubs can operate in an islanding mode, hence improve customer satisfaction by reducing failure probabilities/disruption of services, particularly in the face of climate changes and landscape change of power grid.
- Networked energy hubs also benefit from offering services to the power grid where possible, such as load levelling, demand side response, voltage and frequency, etc. The discovery phase has revealed that the services provided by the hubs can generate sufficient income to significantly reduce the payback period from 22.6 years to 7.6 years.
- Levelling up in the Northern Powerhouse in terms of services/skills required – educational/upskilling needs met through University of Leeds – contributing to the government’s 250,000 jobs target in the Ten-Point Plan.
- The consortium creates/leads a whole system integration and holistic approach for the rail and power industries, in accelerating and scaling up development in the north.
- Railway customers: high quality services due to improved resilience of power supply, reduced costs for EV charging at stations, and greener and quieter services with 3 Mt CO2e reduction p.a.
The power network users and clients will also benefit from the project due to enhanced performance and flexibility of the distribution network which is achieved by maximizing the utilization of renewable generations and by leveraging huge flexibility potentials from the energy hubs, including huge energy storage facilities in the hubs to coordinate the supply of 440GWh pa railway non-traction power and recover part of the 4TWh pa traction power (one third of which can be recovered in theory), and huge storage capacity of EVs in station car parks. The following benefits for the power network users and clients are addressed in this project:
- Reduce electricity bill;
- Greater robustness within the distribution grid;
- Availability for EVs to be charged and connected across 2500 stations with reduced fees;
- Reduction of CO2 emissions by 3 Mt CO2e p.a.;
- Better health conditions; and
- Reduced dependence on imported fossil fuels and hence reduced exposure and vulnerability to volatile fossil fuel markets.
Quantitative market benefit measures include:
- Capital cost savings for railway energy supply infrastructure;
- Operating cost savings for railway energy supply;
- Premiums for offering services to the grid;
- Reductions in railway GHG and air pollution emissions.
Learnings
Outcomes
The project’s outcomes were delivered through three work packages as detailed below.
WP1: Data gathering and partnership engagement.
Several engagements with key relevant stakeholders were held over project duration, and relevant data and information were collected the for detailed design of the hub:
- Two site visits were carried out with targeted stations to understand the hub construction complexities (electrical, civil, mechanical, safety, licensing, ownership etc.).
- With the Network Rail planning team, the consortium team collected all relevant information, including, but not limited to, infrastructure data, station and parking layout; electricity data, low/high voltage electricity layout; existing metering and SCADA systems; energy/power supply and consumption data at appropriate granularity; space availability for hosting the hub, including energy storage; weather conditions.
- Engagement with key stakeholder where it is necessary to understand the broad context, complexities and impacts of building the hubs in the selected locations.
Milestone – Detailed data and information required for the hub design was obtained and analysed.
Deliverable – A Report containing all technical data (electrical, civil, mechanical, safety, licensing, ownership, etc.), and information required for the hub design was prepared and submitted.
WP2: Energy hub engineering design
- ·Several communications were made with Network Rail design team, and engagement with microgrid specialists, OEMs and suppliers (energy storage, PV installer, PCS supplier, protection system, digital twin, energy management system, etc.) to develop and design the energy hub specifications.
- The energy hubs were designed to demonstrate key features of minimum viable product (MVP):
- The ability to exchange power between AC and DC at different voltage levels.
- The ability to coordinate the flow of electricity from sources to loads under a variety of operating conditions.
- Ability to provide ancillary services to the grid, when necessary, to meet voltage and power factor regulations, harmonic elimination.
- To provide a modular design approach that ensures robustness and reliability regardless of potential faults and disturbances caused by load and grid fluctuations.
- To provide reliable power supply to critical loads, both grid-connected and islanded conditions.
- The hub design was validated technically within a software defined and hardware-in-the-loop environment.
Milestone 2 – The Stranraer and Newton-on-Ayr energy hubs were detailly designed. Using SIMULINK and PSCAD software and Typhoon hardware-in-the-loop, these designs were accurately validated.
Deliverable – A report containing specifications for the hub design, electrical schematics, and geometric layout of each hub. The various subsystem sizes and ratings were provided in sufficient detail to facilitate the production of accurate simulations and hardware-in-loop validation results. Results from simulations as well as hardware-in-the-loop validation are presented.
WP3: Energy hub implementation plan and business models, assess the transferability of the designed energy hub solutions to other rural and urban stations.
Developed an implementation plan and business model:
- Engaged with key stakeholders to develop the hub implementation plans including both civil and electrical installation for the targeted stations, including hub construction time scales, planning applications with different authorities.
- Evaluated off-the-shelf solutions for various subsystems/components, and assessed system costs, installation and construction costs, as well as project management costs during the installation phase.
- Engaged with system operators to discuss the different services that energy hubs may be able to participate in, as well as assessing their benefits.
- Assess the transferability of energy hub solutions to other rural and urban stations in the UK and globally. Stations along the Glasgow and Southwestern route and the Stranraer - Kilmarnock – Dumfries route are immediate options for transferability.
- Developed suitable business models with various stakeholders of the energy hub (station, train operators, Network Rail, car park owners, and customers) so as to maximize the benefits and impacts of the hubs and make them business as usual.
Milestone 3 – Produced a Hub construction plan and business model.
Deliverable – A report detailing hub construction plan including time scales, potential suppliers of subsystem/components with a list of OEMs and technical suppliers, estimations of costs. Adequate schemes/methods addressing potential complexities with hub construction and installation have been presented.
Lessons Learnt
Project changed from expectation at the start of the project.
Availability of Land for PV installation: It is necessary to have sufficient land area for the installation of PV arrays in order to meet the extra traction power demand needed to expand capacity at Ayr/Newton-on-Ayr and charge battery trains at Stranraer. In spite of this, the amount of power that can be harnessed from solar panels to meet traction power demand rather than relying on the distribution network can be limited depending on the land available, which can result in increased operating costs for the energy hub if the local generation capacity is limited, hence having to rely on importing lower from local distribution or distribution network.
Electricity complexity: With the limitations imposed by the standards around the requirements of new connections and their export/import limitations, there is a restriction on the export and import from the utility grid, which is the licensed distribution network operator (DNO) where these hubs are to be installed. The EREC G100 establishes the criteria for the operation of the hub’s limitation schemes and the allowable size of generation (PV arrays and battery energy storage systems) that can be installed. With the connection of the 11kV network at the two sites, customers have the opportunity to export or import limit up to 1MW through Customer Export Limitation Schemes (CLS). For Stranraer, this power capacity is within limits, but Newton-on-Ayr's power capacity exceeds 1MW, so G100 export limitation schemes have significant impacts on the design of the PV and BESS size, limiting the whole capacity of the energy hub to adequately meet the design requirements. To circumvent this barrier, the energy hub can either be connected directly to the transmission network or connected to the transmission network via the nearby railway traction power feeder station.
Energy hub schematics: Currently, the energy hubs have been designed and investigated as DC microgrids. However, the electrical bus voltage design, the capacity for the BESS, power electronic converters for interfacing with 25kV overhead line are subject to the cost and availability of the products in the market.
Effectiveness of the innovation development
A microgrid solution that is cost effective for railway decarbonisation while providing maximum benefits to the power grid has been developed in this project. As well as integrating local renewable energy generation and energy storage, railway routes can recover regenerative energy from trains approaching stations. They can also coordinate traction and non-traction power supplies. The following results were obtained from this research.
- Advance control strategies that will effectively coordinate charging of battery powered trains particularly in rural areas lacking sufficient distribution grid capacity for electrification. This represents a major CapEx saving for Network Rail compared to installing the overhead lines.
- In contrast to the installation of a new feeder station, Network Rail can save significant capital expenditures by using the energy hub to supplement overhead traction power lines, particularly those equipped with electrified systems. Additionally, the energy hub provides dynamic voltage regulation services to the traction power supply whenever the voltage falls below the statutory minimum level, which are currently not available on the overhead traction line. As a result, a stream of revenue will be generated, and power losses will be reduced.
- By participating in services such as frequency stabilisation, demand flexibility, and wind curtailment mitigation, the energy hub will provide cost benefits to customers.
- A range of novel optimization techniques have been developed to adapt the hub concept to diverse environments, and these techniques are used to determine the optimal size, cost, and payback period for the hub concept.
