Issue link: https://read.utilityweek.co.uk/i/665572
T he number of grid-rechargeable electric and plug-in hybrid electric vehicles (EVs) sold in the UK has doubled between 2015 and 2016. Globally, the statistics on EV adoption display the early signs of an exponential curve. Management scientists call this the S-pattern of new technology adoption – smart phones, hybrid vehicles, and the internet have all followed similar trajectories. If EV growth continues at this rate, by 2018 we could see more than 100,000 new plug-in vehicles being sold in the UK every year. From the perspective of the energy system, a rapid shiˆ to electric cars is unlikely to significantly threaten security of supply. Studies in Norway, the US and Japan have all resulted in the same conclusion: if all cars on the road were plug-in electric, national electricity demand would only increase 5 to 10%. National Grid's capacity planners and UK energy policy advisers have ample time to prepare for the long-term increase in demand. The concerns for DNOs are quite different, however, and uncertain. Consider, for example, a Tesla supercharging station. A full station with five charging bays operating at 120kW for enough time to refill five Tesla 60kWh batteries would cause a surge in demand of 600kW for half an hour. To put that in perspective, at peak time the average UK household electric power consumption is about 800W (according to 2015 data from the Department of Energy and Climate Change). This is equivalent about 750 extra homes plugging into the distribution network. To accommodate this demand, Tesla equips its stations with dedicated transformers, however the risk posed by this scenario really depends on the probability of it actually happening. Using a statistic from the National Travel Survey in 2014, the average car in the UK travels 3,235 miles a year. An individual EV with a 200-mile range might therefore only have to recharge as little as once a fortnight. Second, the ongoing debate in the EV community suggests that the most convenient recharging location is still the home garage, despite the free or nearly free access to public chargers that many charging networks and OEMs are offering to attract buyers. The Electric Power Research Institute has analysed a dataset of observed driving behaviour in the US, and found that 70 per cent of charging would occur at home, 25 per cent at the office and 5 per cent in public areas. Home charging at 3.3kW on the residential grid is likely to be more manageable for DNOs. If an EV-friendly neighbourhood cluster were to become problematic, simple timer delays could NETWORK / 34 / APRIL 2016 suffice to reschedule some charging to night- time off-peak periods. Finally, only Tesla cars can currently withstand the high power levels associated with superchargers, so the risk is limited to the portion of the market that owns a Tesla. Superchargers are intended for use on long- distance trips of more than 300 miles: the type of trip that a typical UK driver would make once or twice a year. The rest of the cars in the market would use 22 to 50kW for their emergency charging needs, which is available on ChadeMO or Mennekes rapid chargers on the Source London, Ecotricity, PodPoint and POLAR networks, in combination with regular 3.3kW residential power for everyday use. Many EV owners or operators of charging stations are also using their own solar panels to supply the energy for the car, and have no impact on the grid at all. So how much sleep should DNOs lose over the rise of EVs? While it is important to study the risks, a growing body of academic research is instead assessing the beneficial impacts that EVs might have on distribution networks. EV batteries, unlike many household electrical products, are not only passive loads, but also devices that can be used to store and supply power, if the necessary technologies for control and communications are in place. Valley-filling, or the practice of recharging EVs at off- peak periods, can improve the economic efficiency of the grid by increasing the utilisation rate of assets and minimising system costs. EV batteries will also be valuable for demand response because they can be so quickly ramped up and down and represent a potentially large source of non- essential, interruptible demand. To achieve these benefits, a number of technologies will have to be deployed. The key driver to activate this deployment will be scale – reaching a sufficient number of EVs on the market so a standardised communications architecture and soˆware – connecting vehicles, charging point, and grid operator – becomes economically justifiable. Scaling up the number of EVs will also unlock further investments in charging stations that are necessary to redistribute EV loads and avoid clusters. So, scaling up the number of EVs on the roads is a double-edged sword for DNOs. Scale-up may be more helpful for the grid than it is detrimental. It means new applications of cars as batteries and flexible, aggregable power sources, could become economically viable. Dr Claire Weiller, Institute for Manufacturing, University of Cambridge Don't fear the EV Power-hungry electric vehicles may not be the threat to the energy system many think they are – they may even be a benefit. ELECTRIC VEHICLES