The Limitations and Potential Barriers to Wide-Scale Vehicle-to-Grid in the UK?

By: Becky Gough

With such diverse potential for electric vehicles (EVs) to provide significant emission and cost savings it is sometimes difficult to see a downside to the potential EVs have to offer. However, with rapidly increasing electricity demand on the UK electricity grid due to supply diversification and an increasing population, EV charging could add to that load increase [1]. It would therefore seem that “managed charging” and discharging through vehicle-to-grid technology (V2G) will provide an ideal solution, providing peak demand support when required. Several setbacks could hinder the uptake of this technology and in this article we look to discuss some of the factors that could affect the timely and effective uptake of V2G in the UK over the coming years.

At present V2G technology is predominantly limited to the Japanese market, with the few systems available developed to provide backup electricity support during power cuts. Presently, one of these is “UK-grid-compatible” with the necessary certifications and Kitemarks. Due to this still being very much an emerging market, prices for the technology are high, with the UK compliant system coming in at over €24,000. Technology at this cost would take over 30 years to break-even assuming adequate payment schemes become available. This is of course an unrealistic return on investment and V2G technology must align with current charging infrastructure and equipment costs in order to provide any real financial benefit to the user, along with providing technology developers with a robust business plan.

One way to prevent such high infrastructure and technology costs could be to move the bi-directional inverter onto the vehicle and as such reduce the technology and hardware costs considerably (as BYD Auto has done in all their EV line-up [2]). However, network issues still remain if a considerable number of vehicles have V2G functionality on-board. Large numbers of EVs connecting to the National Grid will have a significant impact upon the Distribution Network, causing major network overload unless appropriate management systems and network upgrading occurs [3].  The majority of District Network Operators (DNOs) are looking at ways of mitigating the cost and technology requirements an estimated increase in peak electricity demand of 86GW by 2030 will cause [3]. This cost could be as much as several million pounds per local distribution network. Due to the increasing number of EVs in the UK and ageing network, this upgrade is imperative if UK grid infrastructure is to be capable of supporting EV charging and discharging [4].

Whilst physical technological requirements are significant in order to ensure timely uptake, complex development is also necessary with electricity trading and payment schemes. The management of many disparate storage assets presents complex software requirements involving a multitude of algorithms and calculations capable of establishing charging and grid support requirements. This is likely to be through a Virtual Power Plant (VPP), a high level control system that utilises disparate assets under its command to provide peak shaving and ancillary services when required to the National Grid (See Figure).

Effective management requires consideration of a plethora of variables including; EV users, building demand, National Grid requirements, EV battery capacity, time of day, EV availability, distribution network limitations, payment tariffs and other availability assets. Through algorithm utilisation the VPP is able to consider and control all of these variables and as such is able to establish the suitability of each EV in providing services to the National Grid.

One of the key variables mentioned above is the payment tariff. This refers to the payment value offered/ received by the VPP/ EV owner for the use of the electricity within the EV battery. It is likely payment will be managed in a similar way to the Feed-in-Tariff for PV generation. However, as the battery is not generating any excess electricity, variable price structures may be employed (for example a commercial building you are connected to may offer you one tariff, whilst the VPP offers another). Electricity could be sold either to the National Grid (via the VPP), a large commercial property (such as the EV user’s place of work) or a domestic property. It is therefore necessary for a robust management system to reduce the complexity on the user side of the system, calculating where the greatest economic benefit lies (National Grid or building) and as such trade with the VPP or building accordingly. The complexity of this trading scheme is vast and there is potential for a system to be produced that over complicates the process for the user and as such prevents timely uptake of the technology due to users not signing up to the scheme. As such it is imperative automation and effective management is achieved early on in the development process.

In addition to the potential complex trading requirements wide-scale EV with V2G uptake will cause, battery size and impact are other key considerations. Very little research has currently been conducted to explore the impact V2G technology will have on the battery life cycle. Increasing the charging/ discharging cycles on the battery may cause huge degradation issues and therefore require a much increased replacement schedule for the battery, reducing the cost saving experienced through signing up to a VPP/ V2G scheme. Additionally, the battery size of the vehicle may be unsuitable for long term, regular grid or building support services. There could be a real danger of an EV user running out of electricity during a journey, causing huge wide-scale impacts on V2G and VPP markets.

Vehicle-to-grid has the potential to reduce peak grid and building electrical demand requirements through exploitation of excess electricity within the EV battery. Effective management systems must be employed in order for the aggregation of these disparate assets is achieved effectively. This is a relatively novel research area and as such there is huge potential for development. Currently the technology is in its infancy and therefore costs are high. Through timely technological development it is expected costs for V2G will align with current charging infrastructure costs, making a strong economic case for all stakeholders. Nonetheless, it would be prudent to evaluate the battery degradation impacts and size requirements for a variety of users to ensure the majority of use scenarios are suitable for inclusion.

[1] Department of Energy and Climate Change (DECC), “Energy consumption in the United Kingdom : 2012,” 2012.
[2] http://www.byd.com/la/auto/technology.html
[3] National Grid, “Journey of Discovery,” 2014. [Online]. Available: http://www.nationalgridconnecting.com/journey-of-discovery/. [Accessed: 29-May-2014].
[4] National Grid, “Operating the Electricity Transmission Operating Networks the in 2020,” 2011.

 

Becky is a Research Engineer currently working towards a Systems Engineering Doctorate in low carbon technologies with Cenex, The Centre of Excellence for Low Carbon and Fuel Cell Technologies. Her background is in the buildings sector, graduating from Nottingham University in 2012 with a degree in Architecture and Environmental Design. As a building services engineer she began her Engineering Doctorate in 2012, looking at the interoperability of renewable technologies into domestic and commercial properties. From this her work led into the design and optimization of hybrid heat pump and photovoltaic thermal systems in association with her first sponsor company.

Her current research looks to explore the integration of electric vehicles into the built and smart cities environment. How EVs can be used as a reserve energy store for peak shaving services in the UK is of key importance. She is involved in several Innovate UK funded projects looking to explore the role vehicle-to-grid will play in the energy supply network over coming years.