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NETWORK / 33 / JULY/AUGUST 2016 D o u b l e - e D g e D S w o r D The Power Networks Demonstration Centre weighs up the pros and cons of EVs for electricity networks Pros: u Electrification of transport into electricity networks provides a possibility to develop an integrated approach towards the achievement of climate targets. u The networks are increasingly expected to be operated in a flexible way to defer reinforcement and accommodate renewable energy sources. Electric vehicles can help the operation by providing a buffer during grid balancing through the exchange of stored energy. u The power-electronic converter interface of the charger can provide additional services to the grid such as harmonics mitigation and voltage support. u DC distribution grids are gathering some momentum and battery technology used in EVs is inherently DC. This future- proofs the use of EVs in new grid concepts. CoNs: u The requirement for higher charging current to reduce charging time can overload circuits, especially if ownership of EVs forms clusters. u The probability for peak lopping generation would increase if EV charging coincides with existing load peaks such as those observed at early evenings for residential load profiles. u Unless the response of the converter interface of the charger is characterised, this can have negative impact for the stability of the network, particularly in abnormal grid scenarios such as faults. The Power Networks Demonstration Centre (PNDC) is an innovative development and demonstration facility founded by the University of Strathclyde and brings together academics, engineers and technologists to define and execute research, development and demonstration projects that will help to shape the electricity industry of the future. Its purpose is to undertake a range of innovative projects that will accelerate the proving and adoption of new 'smart' technologies, from advanced power grids incorporating renewable generation and storage to electric vehicles and household appliances. The centre has recently been involved in EV trials seeking to develop a hybrid bus that can be charged on route using inductive charging. On-route charging allows the bus to extend the range it can operate in electric mode, thereby requiring a smaller battery pack. The goal is to have the bus run in full electric mode within urban or pollution-sensitive areas, while in other areas the hybrid mode is used. The PNDC has supported the project by installing and operating an inductive charger at its facility, supplying a data-logger with sensors, recording the energy use on the bus and carrying out grid integration assessments for the charger. network today, they would generate the equivalent output of a 180MW power plant. That figure has the potential to increase to 370GW if all vehicles on UK roads are electric. One concern with vehicle-to-grid storage is the amount of degradation it might cause to an EV battery. Battery life has been a key issue in the uptake of EVs. Early models were only guar- anteed for two to three years. This has now been extended to 10-15 years, but tests have shown that providing a 7kW charge to the grid puts the equivalent strain on an EV bat- tery of driving at 20mph. This has knock-on concerns not only for vehicle lifespan but also for end of life battery applications, the scope for which is attracting rising inter- est as the market for static energy storage begins to boom. The challenge of EVs for DNOs are com- plex, manifold and immi- nent. There now seems little doubt that a radical increase in EV numbers will occur within the current price control. Do networks have the flexibility to respond at pace? Dutch electricity transmission operator TenneT and charging infrastructure developer The New Motion earlier this year embarked on a world-first trial. They are harnessing the power of thousands of EVs to help balance renewable generation on the electricity system. Market stats: l Renewable energy accounted for 11% of the total electricity consumption in 2015 l 10% of vehicles in 2015 were plug-in l Dutch parliament banned the sale of new petrol and diesel cars from 2025 – the first country to do so, although the coalition government is split on the rulings feasibility l The size of the country means cars are driven on average for only an hour a day l Smart tariffs due to be introduced in 2017 l High proportion of lease cars are stationary in office car parks CasE sTUDy: BalaNCiNg ThE NEThErlaNDs