TransEnergy - Road to Rail Energy Exchange (R2REE)

The focus of the research proposed is on electrically powered rail transport systems and electric road vehicles (EVs), and extends to the power supply network which supports them. The convergence over coming years of both road and rail transport on electric power with reduced dependence on fossil fuels offers great potential benefits, but also has risks from dependence on a single fuel type and peak demand stress on its underlying supply network. Although fossil fuels have environmental drawbacks they have the advantage of offering inherent energy storage, thereby desynchronising time of energy use from its supply, and smoothing demands on the supply network. This is not the case for electricity use in which there are currently only limited means to smooth and reduce demand.

The proposed research addresses both the technology to store electric energy in a form suited to transport use, and the modelling to understand how to use the technology to reduce overall energy demand. Transport energy demand reduction can be viewed at two timescales: (i) a twice daily demand caused by rush hour commuting, and (ii) minute by minute variations in demand as required by individual vehicles. Both timescales pose tractable research questions which can be addressed by energy storage. The work will examine the technical issues surrounding the use of both new batteries, and second life (old) EV batteries as line-side storage. This study will be complimented and enhanced with the addition of research on through-life environmental issues, and the consumer acceptance and legislatory constraints surrounding this use. In addition, the novel use of EVs in a road to rail (R2R) energy exchange scenario will provide an opportunity to explore the use of in-car EV batteries as energy storage when parked in rail station car parks, and address the implications of this use on the consumers, together with the consumer acceptability.

The research will be accomplished through eight interrelated work packages:

WP1: Techno-economic supply chain analysis of energy storage technologies for application in UK rail and road transport
WP2: Optimising transport network operation for R2R energy exchange
WP3: Power network simulation
WP4: Versatile line-side storage demonstration
WP5: Demonstrator data analysis and second-life EV battery
WP6: Attractiveness to users and incentives for implementation
WP7: R2R Communications, control and interfacing
WP8: Project Management

The achievement of a step change reduction in transport energy demand is only one aspect of the impact expected, and the project has important and far reaching implications for UK power grid and transport system stability (road and rail), distributed energy storage in the rail sector, road EV battery reuse and recycling, and job creation. The demonstrator facility forms part of a much bigger platform of research and development on the changing face of the electrification of the rail sector, and energy utilization exploiting the 'smart grid' concept, including V2G and road to rail (R2R) power transfer, power electronics and alternative energy technologies. The scenarios in this application solve problems that are very much in the public eye; efficient energy usage in the transport sector, reducing CO2 emissions and saving energy, and the upgrading and modernisation of old infrastructure. The main impacts of the work are outlined below.

Use of rail line-side storage and road to rail (R2R) energy exchange will reduce total electric transport energy use and smooth peak demand, reducing generation stress. Removing rail network power constraints will enable provision of higher frequency train services to passengers. Rail operators and infrastructure managers will benefit from increased rail efficiency with potential for reduced costs for travellers. The use of customers' cars for transient energy storage could be linked to a ticket price incentives for involvement.

Battery energy storage systems (BESS) have a significantly faster response than mechanically based storage systems, meaning the BESS can provide high power requirements for train acceleration, and absorb regenerated energy on deceleration without affecting the supply voltage, hence not requiring the energy to be dissipated as at present on DC lines. The energy recovered can then be utilised in the next acceleration event increasing overall system efficiency and lowering supplier energy demand. Benefits apply to electric passenger services and freight operations using regenerative braking capable locomotives, incentivising regeneration where not currently available. TfL have two major impacts which they aim to achieve with this research: (i) Reduced transport energy use and power supply stability improvement, (ii) better ability to absorb the power from regenerative braking to lower ambient temperatures in the Underground, and hence give a more comfortable customer experience. On the underground network, energy storage is needed to stabilise the power supply by providing a buffer for the high power transient requirements of the frequent train services. Although regenerative braking is in place on modern rolling stock (e.g. Victoria line) the network cannot always absorb the energy, and braking power is dissipated as heat via onboard resistor grids. The research will show how to reduce or remove this heating of the Underground.

The project includes exploration of reusing electric vehicle batteries as rail energy storage in a second life application. This will help the battery manufacturers enhance the attractiveness of their batteries, reduce whole life costs, and reduce environmental burden through extending useful life. Currently, when batteries are removed from EVs, they retain approximately 80% of their new capacity which is lost when the battery is recycled. The exploitation of a second life market will increase the operational lifetime of the batteries, lowering the costs of use to EV owners. The research could also impact on the automotive systems design so that the switch between first and second life is more easily transitioned, while opening up information and communication on life cycle issues and battery management systems in R2R applications. Furthermore, it may also be possible to use such second-life schemes to subsidise the cost of EV batteries, thereby reducing the cost of an EV and as a consequence reducing the cost burden to the purchaser.