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TRL electric vehicle trial highlights need for managed charging

Volkswagen e-Golf

The benefits of managed charging – whether by users being incentivised to charge at set times or suppliers controlling charge times – have been demonstrated in a TRL trial.

More than 200 consumers took part in the eight-week trial using either a battery electric  vehicle (BEV), the Volkswagen eGolf, or a plug-in hybrid electric vehicle (PHEV), the Golf GTE.

They were split into three groups:

  1. User-managed charging (UMC) in which participants were incentivised, through a structured tariff, to charge at times of day when the supply-demand balance is favourable.
  2. Supplier-managed charging (SMC) in which participants specified the charge they required and the time they required it by, and allowed the supplier to control the timing of charging to maximise cost savings
  3. A control group who did not experience a MC scheme and were not incentivised to charge at any particular time or in any particular way.

Their charging behaviour at home was recorded from their charging unit while telematics data from the vehicles recorded vehicle usage and away from home charging.

It was anticipated that charging behaviours might differ at weekends because of potentially greater behavioural flexibility, so these measures were recorded separately for weekdays and weekend days.

Key findings

  • In unmanaged charging conditions, participants usually charged at home in the late afternoon/early evening (3-8pm). At home, weekday charge start times in the control group peaked between 5-6pm for PHEV participants, and between 6-7pm for BEV participants. At weekends the peak in charge start events is less pronounced, with a greater share of charge start events starting earlier in the day.
  • Compared with unmanaged charging, the proportion of home charge events starting between 4-7pm was more than halved in the UMC and SMC groups. The greatest reduction was observed in the SMC group. The majority of charging was shifted to later in the evening (UMC) or overnight (SMC). This effect was observed for both weekday and weekend charging.
  • In general, after receiving information about both MC schemes at the end of the trial, participants indicated that UMC schemes have higher appeal than SMC. However, pure electric vehicles drivers who have had direct experience of SMC were more likely to prefer an SMC scheme. While dependent on the wider context of the consumer offering, this suggests that experience with SMC may be important for adoption of that type of Managed Charging scheme.
  • Participants in both MC conditions initiated the majority of charges using the Default settings suggesting that engagement with MC can be encouraged by making it as easy as possible for consumers. Setting new parameters following plug-in was more common in the SMC group than the UMC group; it is possible that users engage more with an SMC scheme than UMC because of the nature of the system (e.g. setting Desired SOC and Departure Time versus simply setting a charge start time).
  • The key attributes which contribute to an attractive MC scheme for consumers include high annual cost savings, low peak electricity costs, and nearby public charging.Features which make SMC in particular more attractive include an override function where users can change settings for a charge event after they have been input (even if in doing so they lose all financial benefit for that event), and availability of a public charge point within five minutes drive of the users’ homes (to act as a back-up in case their car is needed earlier than expected). This was particularly true for BEV drivers who, unlike PHEVs, do not have the back-up option to drive under fuel if their batteries are not charged.
  • Most charge events away from home started in the morning; peaking between 7-8am for PHEV drivers and 8-10am for BEV drivers. This contrasts with the control group home charges (which were also in unmanaged conditions), where peaks were observed between 5-6pm for PHEVs and between 6-7pm for BEVs. Self-report questionnaire data suggests that a large proportion of these morning charges away from home were at participants’ places of work or education. Weekday charge events away from home were more likely to start overnight or in the early morning, compared with weekend charge events.
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Comments

  • Shirley - 19/12/2019 10:23

    Its not clear from the above whether the consumers are already EV users or new users who were given the vehicles to test. As an EV owner, I would suggest that this will make a fundamental difference to the results of this trial. As owners we recognise the significant cost to charging at home on a regular basis and have reviewed and switched to EV tariffs and charging over night etc once been using the vehicle for a while. The only day charging done by is when out and about for long journeys.

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  • Dan - 02/01/2020 11:41

    As a PHEV owner the main issue for me is that my car has a very poor interface to manage charge and to do anything more advance than turn charging on or off by plugging the car in. there is a mobile app that has a fix week charge planner but it is no a serious attempt at a proper interface. what was not clear from the article was how many times the UMS, SMC and MC affected the use of the car because the SOC was wrong. What was attempted was optimization against a parameter, but other parameters were not described as to trade offs. for example there is a Swedish survey that has show the impact on battery life if you further limit the SOC "swing" So do we want smoothest energy usage for DNO? lowest cost for user? lowest wear and tear for battery? best dependability as to range?

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