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Electrical Demand Charges,

How to prevent them from stopping people using EVs

Demand charges can send the cost of electricity sky high and take the public EV charging cost with it. The last newsletter (sent out around June 6 in case you missed it) had a discussion of how that works. That is a big part of what is behind the high rates being considered for the charging network, particularly for the DC to DC fast chargers.

 

The challenges involved point the way to solutions and the need to consider these concerns more carefully. A few ideas came out of discussions at EVS and more recently that help keep the cost down.

 

These ideas seem to fall into three main categories. One is to find ways to keep the charging going at the most even rate. The other is to spread the charging around so that we do not have high peak demands in any one area. The third is to use solar systems to cut the peak demand.

 

An even rate of demand can help by keeping the average rate of use at any location as close as possible to the peak rate of use. If the Average use is equal to the Peak use on a 24 / 7 basis, that would be close to ideal. It means the peak demand charges can be averaged over all the uses in one location. That spreads the demand charge out as much as possible and it becomes a much smaller factor per kilowatt used.

 

The extreme opposite would occur with a DC to DC fast charging station that is used once a month in the middle of the day. The 50 kW rate the fast charging uses would most likely create the peak demand for the location. That means that the demand cost is attributable to that one half hour use and the EV charging should cover the entire cost. That is how you pay four or five times as much for a charge.

 

One way to smooth out the rate of demand is to install battery storage that will store energy with the charging stations. The batteries would then feed electricity to the chargers to reduce their peak demand. This idea came from one of the panelists at EVS.

 

This is particularly important for the DC to DC fast chargers. None of the DC to DC fast chargers examined at EVS 26 included this feature. This idea raises the question of the cost benefit to such a battery pack. It is probably the most expensive way to reduce costs.

 

Creating an even rate of electricity usage can be accomplished using a number of strategies.

 

One strategy is to install the charging stations in high demand facilities. The charging peak demand will be a smaller percentage of the whole. This came from Ed Kjaer of So Cal Edison. Jim Dewey points out that this is still a considerable incremental cost, but it is true that large industrial accounts will have less costly demand charges than small commercial accounts.

 

Another strategy is to install the chargers at facilities with the ability to manage the power supplied to the charger. The chargers can have their charge rate adjusted by the facility energy management systems during peak times. This idea was brought to light by Enid Joffe at Clean Fuel Connections and by Vickie Pruit at Edison and is demonstrated as possible by the Schneider equipment.

 

Another strategy is to limit the number of charging stations at any one location so that each one is used more frequently. If a station is used 10 hours a day then the peak demand is spread out better than if it is used four hours a day. This was made clear by the model used by Jim Dewey in Santa Barbara. Used once a month at high rates of demand and that is a very expensive charge.

 

This could be used in work place charging effectively. Let’s say there are four EVs at one location. You could put in four level 2 charging stations. All four users would plug in every morning and the demand would be four times the charge rate (over 20 kW if they are all new Leafs). Alternatively you could put in two level 2 charging stations and limit parking to 4 hours. Two vehicles would charge in the morning and two in the afternoon. Now your peak demand from the stations is half what it would be with four stations. Four hours of level 2 gives over 40 miles on most vehicles and that covers most people’s daily travel.

 

Using level one chargers (110 volt systems on standard outlets) whenever possible

 

There is an even lower cost way to handle that same situation. A typical level 2 charging station uses one 240 volt circuit rated at 40 amps. That same circuit can be split into four 110 volt circuits each with 20 amp capacity. That means you can put four level one outlets in place of every level 2 charging station. That would let four vehicles charge when only one could before. Leave your vehicle there for nine hours and you once again get over 40 miles range from your workplace charger. Your demand is more consistent over the ten hour day and your electricity costs are as low as you can keep them.

 

The other good thing about this last option is that the up-front costs are cut drastically. Each plug in location would cost a few hundred instead of over five thousand. You can charge 4 vehicles on level one with the circuit that it takes to charge one at a time on level 2. That means you would not need two of these circuits!

 

The whole charging discussion has tended to ignore the level one option up until recently. There are a whole range of reasons for this. Many of them seem to be more important to people who do not drive EVs. One big reason is that there are a lot of companies that want to make money from high rates of charging systems. The following considerations point to a different set of thoughts than the ones that non EV drivers might have in mind.

 

Plug in Hybrids do not need level 2 charging in almost all home situations. It is nice for opportunity charging when out and about but not essential. They are outselling AEVs three to one in part due to this factor. Level one (110 volt) charging is already available in almost every single family home and in many condos and apartments.

 

AEVs can be charged effectively on level one under numerous conditions including:

* Vehicles normally used for the average daily miles traveled of 32 mile – level one will charge this much in 8 to 10 hours also known as overnight.

* Vehicles with 110 charging at home and 110 at work would have enough charge time for over 100 miles per day

* Vehicles that charge ten hours on 110 for six nights a week and twenty hours for one day have enough charge to drive 320 miles a week or over 16k per year.

 

Yes, there are good reasons to have level 2 and DC fast chargers in the mix of public charging options.

Yes we need to solve the level 2 home charging concern. That whole discussion is important and it is important to keep it from encouraging people from getting EVs they charge on a simple plug.

 

An interesting article showed up after most of this article was written. It was in the July edition of Charged Electric Vehicle Magazine (chargedev.com). I strongly recommend that you read the article as it is written by an Engineer who has been using EVs for some thirty years. The fact that it is in nearly total agreement with my point of view is another good reason. It seems the longer you use an EV the better you understand what they take to be used effectively.

 

The next newsletter will look at more ways to keep public charging costs down. If you have read carefully so far you will know there is a lot more to cover.

 

This article was written by Russell Sydney.

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