Four Corner stones for a National EV charging plan

Discussion of the location and operation of public EV charging infrastructure in Scotland
Martin Lee
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Four Corner stones for a National EV charging plan

Postby Martin Lee » Mon Nov 19, 2018 10:38 am

In March 2017 Orkney Renewable Energy Forum organised a meeting for EV owners in Orkney to discuss updating the Orkney EV strategy.
The actual supply of EVs is something that Orkney can’t directly influence so the discussion centred on provision of chargers, maintenance and repair, issues with communications failures to the chargers preventing a charge, and the cost of charging.
Maintenance and Repair are ongoing issues in Orkney and still need to be addressed.
Communications failures have to a large extent been eliminated as an issue following the switch to the white list system around December 2017, January 2018 where authorised cards are recorded on the charger and will allow a charge if communications can not be established with the central validation server.
Cost of charging to some extent overlaps with the provision of chargers and the types to be provided. However, it’s been agreed that appropriate charging will be introduced in April 2019. The final prices have not been agreed but there is a logical method behind a suggestion of 18p per kWh for AC chargers up to 22kW and 24p per kWh for Rapid chargers. (There are no fast 22kW DC chargers in Orkney.)
The final issue we had to deal with was the provision of chargers. There are currently broadly 3 types of charger on the market as follows.
a) Relatively cheap home chargers of 16A or 32A single phase. (3.5-7kW)
b) More expensive public chargers usually in the range 16A to 32A either single of three phase. 3.5-22kW
c) Rapid chargers with capacities of 43kW AC and up to 50kW DC in mid-2017
In addition, most EVs are also sold with a 10A portable charger fitted with a 13A plug which for some people provides adequate charging for their needs.
We looked at how these different types of charger were used and identified that there was a need for two different types of charger which were not commercially available at the time.
Slow chargers
The first was a slow charger for use in public spaces, either on streets or in car parks where people park overnight, or for much longer periods such as at airports and ferry terminals. There is no need for these to be fast, most people park their cars for at least 12 hours per day at or near their home. People with home chargers are already catered for, but for people without home chargers there is a big gap. At the moment this is filled either by using rapid chargers, with the user having to wait while the charge takes place, or by using public AC chargers with a longer charging time, with the user having to go elsewhere during the charge and to return later to pick up the car when it is charged. Neither of these options comes close to home charging in terms of convenience. At home a user plugs in and has a full battery every morning. They only need to unplug at the start of their next journey. Based on the principle of charging for AC charging used by people without home charging at around, or just above the average price for home charging and having a higher price for rapid charging, then rapid charging also carries the penalty of a higher price per kWh, and hence per mile travelled.
Analysis shows that a three phase 100A supply could provide a supply to 18 by 16A plugs with no load management but with a sensible load management system and realistic diversity this could be increased to some where between 24 and 48 plugs depending on location and the mileage driven by users. Make the load management system interactive in a very simple way such as asking the driver to request xx kWh and supply a departure time then the system could be used to actively avoid charging at system peak loads.
The development and subsequent deployment of such a slow charging scheme ought to be one of the corner stones of a national charging plan for Scotland. 22kW AC charge posts have a part to play, both as back up to rapid chargers and for those cars which have 22kW on board chargers instead of rapid charging facilities. They are not however a good investment in terms of network capacity for two reasons. First many cars cannot fully utilise 22kW and secondly even for those cars which can utilise 22kW charging in many places it is very inconvenient time wise to use them unless only a very small amount of charge is required. Setting a time limit of say 4 hours would mean a 40kWh Zoe could be fully charged in 2 hours and block the charger for the next two while a 24 kWh Nissan leaf with a 3.3kW charger could have to move on after only taking just over 13kWh and may not be fully charged.
150kW rapid charger
The second type of charger we identified was a faster rapid charger. Drivers have many different options to make long journeys but not many of these options require people to stop for an hour to charge the car every 150 miles. With the current fleet of EVs it can mean stopping to charge for 20 minutes every 50 miles. With longer range cars like the 40kWh leaf and up coming 42kWh BMW i3 it will be possible to stretch to 40-minute breaks every 100 miles.
There are two faster charger types proposed 150kW and 350kW. It will take some time for technology to get to a point where faster than 150kW is required except perhaps for very high end performance cars. However, EVs which are affordable by the section of society who purchase new cars are already on the market with charging speeds of above 50kW. This will be an increasing trend in the next year or two. Moving charging speeds to 100kW halves the time taken to take on board a specific amount of charge and allows faster journeys.
Provision of 150kW rapid chargers on a core network of long-distance routes ought to be another corner stone of a national charging plan for Scotland. With the introduction of longer range and faster charging cars over the next few years 50kW chargers will get demoted to the mid speed range along with 22kW AC posts. Again, 50kW chargers will have their place where power supplies are limited for example. It should be noted though that an off the shelf RMU and 1000kVA transformer are the bread and butter of the electricity distribution network with thousands of such sub stations installed in GB. A standard design with a capacity of 900 or 950kW which can be metered at LV and does not require specialist high voltage training could be developed for charger hubs. I would envisage a charger hub having 12 by 150kW rapid chargers which with diversity and load management is quite easily manageable on a 900kW supply. Where the hub is located in a residential area I would also look at having a slow charging system in place for people who live nearby to ensure that they can also charge at their nearest charge hub without having to use the rapid chargers and wait for the charge to be completed.
Scotland already has a trunk road network of, designated long distance routes. Building a charge hub approximately every 30 to 35 miles along this network with capacity for 12 rapid chargers and an appropriate number of slow charge points and with a minimum of 4 rapids installed would build on the foundations noted above and provide an attractive front door to people considering moving to an EV.
I think that there are a number of other issues which need to be addressed as well in developing a national charging plan for Scotland as well as the types of chargers required.
Ongoing subsidy requirement
In some places commercial operators might see an opportunity to carry out the required developments and this should be encouraged. Elsewhere commercial operators might be willing to invest in chargers but need support in order to install electricity supplies and carry out site works. These could be done by a local authority and leased to the commercial operator using a flexible lease based on usage of the site. In other places EV charging is not going to make money if sensible rates are charged. This will require subsidy for many years and making appropriate arrangements which allow local authorities to provide charging across their area at an appropriate level of service ought to be another corner stone of a national charging plan for Scotland.
Fair charging
Most buildings have at least 4 corner stones and my choice for a fourth one for a Scottish National charging plan is fair charging. I referred earlier to the principle that charging for people with out access to home chargers ought to be at or just above the average price paid by people with home charging. My assessment earlier in the year was that this ought to be 18p per kWh. Perhaps as time has moved on and electricity prices have risen a higher figure might be required. Rapid chargers used for longer journeys should be charged at a higher rate and I have suggested 24p per kWh in relation to 18p per kWh for AC charging up to 22kW. Again, this figure may need to be higher as electricity costs rise. I don’t have a problem paying 30p per kWh in England and Wales if that is what it takes to get commercial operators interested. I do think however that my suggested 24p per kWh is more likely to encourage people to move over to EVs along with the other measures I have outlined above.
Any charging methodology which charges a connection fee is unfair as it adds to the price per kWh in such a way that those able to take the least amount of energy pay the most per kWh. It would be rather like having income tax at 40% on the first £10,000 of income and then dropping to 30% for the next £30,000 and then 20% for anything over £40,000. There would be a clear majority against such a plan for taxation as I believe there would be against un fair charging systems for EVs

Martin Lee 19th November 2018

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Re: Four Corner stones for a National EV charging plan

Postby Scally » Thu Nov 22, 2018 8:48 pm

All good and well-considered views.
But using such a complex network does require a higher degree of motorist education and awareness.
At the moment, we have a fairly highly motivated, rather bright bunch of EV pioneers, (and a few newby drivers who are dumb as two short planks) but as we are seeing from the tabloids, people these days are buying EVs with no attempt to self-educate, and getting into all sorts of bother.
I'd urge simplicity to be a key consideration.
But the faster the charge, the quicker we can move the metal on: meaning that a single 150 kWh super-rapid can service three times as many cars per day as A 50 KwH rapid, and a car with 64 kWh battery is hardly ever going to need to rapid charge at all, because journeys over 200 miles are pretty exceptional. And in business terms , this is much like a fast food restaurant at a service station: it's better and more profitable to have people eating and leaving in 30 minutes than hanging around for hours sipping their espressos.
General Secretary of the Electric Boat Association, founded in 1984, with members worldwide.

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