Electric Vehicle Charging Stations Demand Factors

[Country]

I am designing a facility that is requiring 26 Level 2 Electric Vehicle Charging Systems (EVCS). Art. 625 states that EVCS shall be considered to be continuous loads.

The issue I'm having is that I can not find a reference in the 2011 NEC that allows or disallows the use of a demand factor. Since not all of the charging stations will probably not be used at the same time, nor for the entire day. Once a vehicle is charged, it stops charging, or goes into a maintenance charging state.

I was wondering if there is a code or rule of thumb to use for the demand code for the EVCS.

Thanks.

 

[T.M.Haja Sahib]

I am designing a facility that is requiring 26 Level 2 Electric Vehicle Charging Systems (EVCS). Art. 625 states that EVCS shall be considered to be continuous loads.

The issue I'm having is that I can not find a reference in the 2011 NEC that allows or disallows the use of a demand factor. Since not all of the charging stations will probably not be used at the same time, nor for the entire day. Once a vehicle is charged, it stops charging, or goes into a maintenance charging state.

I was wondering if there is a code or rule of thumb to use for the demand code for the EVCS.

Thanks.

Welcome.Does the following link is useful to you in this regard?
http://www.cbs.state.or.us/bcd/boards/electelv/board_pack/09/20090924/EE_092409_VIIc.pdf

 

[pete m.]

Welcome.Does the following link is useful to you in this regard?
http://www.cbs.state.or.us/bcd/boards/electelv/board_pack/09/20090924/EE_092409_VIIc.pdf

I'm not sure that would be applicable since the OP is in Florida.

Pete

 

[iwire]

I am designing a facility that is requiring 26 Level 2 Electric Vehicle Charging Systems (EVCS). Art. 625 states that EVCS shall be considered to be continuous loads.

The issue I'm having is that I can not find a reference in the 2011 NEC that allows or disallows the use of a demand factor. Since not all of the charging stations will probably not be used at the same time, nor for the entire day. Once a vehicle is charged, it stops charging, or goes into a maintenance charging state.

I was wondering if there is a code or rule of thumb to use for the demand code for the EVCS.

Thanks.

Absent the NEC giving you a demand factor you must carry each at 125%.

 

[T.M.Haja Sahib]

Absent the NEC giving you a demand factor you must carry each at 125%.

Not clear because a demand factor does not exceed 100%.

 

[iwire]

Not clear because a demand factor does not exceed 100%.

Of course it is not because you do not have any NEC knowledge.

625.14 Rating. Electric vehicle supply equipment shall have
sufficient rating to supply the load served. For the purposes of
this article, electric vehicle charging loads shall be considered
to be continuous loads.

The NEC requires continuous loads to be carried at 125%.

 

[realolman]

I don't know anything about it , but that never stopped me before.

I googled the thing and wikipediaed the following.

Charging

In the 2009 standard, two charging levels are defined.^[7]

AC Level 1	120 V	Single phase	16 A
AC Level 2	240 V	Split phase	32 A (2001) 80 A (2009)

Man, it seems like there will be gigantic, lightly loaded feeders required, because there will probably be varying degees of demand, but no demand factor allowed.

Seems like there is a need for a single "machine" that has a single feeder and is designed to meter the charge out to several vehicles, while limiting it's own full load current.

Now, I guess one of you guys will steal that idea from me.

Do these cars charge directly from AC sources?

And one other thing... how much does it cost a mile to run one of these cars? Last time I checked, electricity wasn't free.

 

[hillbilly1]

I don't know anything about it , but that never stopped me before.

I googled the thing and wikipediaed the following.

Charging

In the 2009 standard, two charging levels are defined.^[7]

AC Level 1	120 V	Single phase	16 A
AC Level 2	240 V	Split phase	32 A (2001) 80 A (2009)

Man, it seems like there will be gigantic, lightly loaded feeders required, because there will probably be varying degees of demand, but no demand factor allowed.

Seems like there is a need for a single "machine" that has a single feeder and is designed to meter the charge out to several vehicles, while limiting it's own full load current.

Now, I guess one of you guys will steal that idea from me.

Do these cars charge directly from AC sources?

And one other thing... how much does it cost a mile to run one of these cars? Last time I checked, electricity wasn't free.

There is also a Level 2 DC charger that requires a 200 amp 208 volt three phase feed! Those are just coming out now, the one I installed was so new they had to come out to the jobsite to do the listing testing.

 

[Besoeker]

Do these cars charge directly from AC sources?

And one other thing... how much does it cost a mile to run one of these cars? Last time I checked, electricity wasn't free.

AC sources are generally used for the chargers.
Cost per mile for the electricity is often claimed to be around 2p (a little over 3 cents) per mile in UK for the Nissan Leaf and similar cars.
The 2p per mile would thus cost ?1.20 for 60 miles.
My current car routinely returns 60mpg or better but a gallon of fuel costs in excess of ?6.00 here. About $10 US.
So I'm at about 10p per mile for fuel.
No contest it would seem.
But the huge cost premium over the IC powered equivalent, the costly need to replace batteries within what would normally be considered the reasonable operating life of the vehicle entirely changes the economics of such vehicle ownership.

Maybe these limitations can be resolved. There is another more fundamental issue.
If we switch to EVs in significant numbers, we will need a substantial increase in the electrical infrastructure.
More generation, more transmission capacity, more distribution capacity.....
Typically for UK, electrical energy consumption per house hold would double.

What bothers me about this is that those promoting EVs, including our government, seem to have paid little attention to this constraint.

 

[realolman]

Can you apply a demand factor to forklift chargers?

How long does a facility need to be in place before you can record the actual load and use that instead of nameplates and calculations? ... you can do that can't you?:?

Wasn't Charlie B involved in doing that in a recent thread?

Could you put in a few of these things and record the actual demand, and then install more of them based on that or do you have to use the nameplates for one and all? The thing hillbilly was talking about sounds like it would cook a battery. I can't remember , but it seems to me that most of the forklifts I've seen are 36- 48 v and charge at about 50 A max. ... and there is a big stink of flammable gas involved.

What voltage battery do they use in an electric car? how fast and at what current can you charge them?

 

[iwire]

Can you apply a demand factor to forklift chargers?

I don't believe so

How long does a facility need to be in place before you can record the actual load and use that instead of nameplates and calculations? ... you can do that can't you?:?

Not really sure that is what they had in mind but I think you might be on to something. Just not sure how you set it up temp for recording.

220.87 Determining Existing Loads. The calculation of a
feeder or service load for existing installations shall be
permitted to use actual maximum demand to determine the
existing load under all of the following conditions:

(1) The maximum demand data is available for a 1-year
period.

Exception: If the maximum demand data for a 1-year period
is not available, the calculated load shall be permitted
to be based on the maximum demand (measure of average
power demand over a 15-minute period) continuously recorded
over a minimum 30-day period using a recording
ammeter or power meter connected to the highest loaded
phase of the feeder or service, based on the initial loading
at the start of the recording. The recording shall reflect the
maximum demand of the feeder or service by being taken
when the building or space is occupied and shall include by
measurement or calculation the larger of the heating or
cooling equipment load, and other loads that may be periodic
in nature due to seasonal or similar conditions.

(2) The maximum demand at 125 percent plus the new
load does not exceed the ampacity of the feeder or
rating of the service.

(3) The feeder has overcurrent protection in accordance
with 240.4, and the service has overload protection in
accordance with 230.90.

Could you put in a few of these things and record the actual demand, and then install more of them based on that or do you have to use the nameplates for one and all?

I don't see anything that would allow that.

If you had a group of these chargers at an office building for employees I think it is reasonable to expect 100% peak loading at the beginning of a shift. On the other hand a group of chargers along a city street might have very random loading.

 

[hillbilly1]

...........................................................................................

What bothers me about this is that those promoting EVs, including our government, seem to have paid little attention to this constraint.

They know, it's just............... Here in the states can you say Solyndra?

 

[gar]

111120-2039 EDT

At the present time there is unlikely a problem anywhere, or likely to be soon.

I know of one person in town with a Volt, and he is the son of a former president of GM, and he is not an employee of GM, but he is a significant person in the analysis of engineering, and other trends in the automotive industry.

http://www.insideline.com/nissan/leaf/nissan-leaf-beats-chevy-volt-again-in-monthly-sales-race.html

In my neighborhood there are a lot of "tree huggers", but I believe only two Prius vehicles. We have probably 50% four wheel drive vehicles.

Now some technical considerations. One gallon of gasoline is worth about 33.7 kWh of energy. At $4 per gallon this is about $0.12 per kWh. Assume 25% efficiency overall from gas to wheel, then usable energy is $0.48 per kWh of output. If you don't drive a hybrid then there is additional waste. Also remember there is considerable taxation in the gallon of gas. In near zero wind conditions I can average about 20 MPG at 70 MPH in my F150 4x4 with no box cover with an automatic and a 5 liter V8 engine. I can stay very warm in 0 F weather. My input energy use is about 1.68 kWh per mile. Vehicle capital equipment cost is less than a Volt at about $0.42 per mile under lease. Gas cost is about $0.20 per mile at $4 per gallon. But presently it is closer to $0.15 per mile. I can do much more with the truck than I could with a Volt.

I recently acquired a new pole transformer for my one neighbor and myself. Reason the old one leaked oil. It was 45 years old. My daily load is about 40 kWh, with midnight to 7 am being about 7 kWh. My night load is higher than would be for someone that also used natural gas for heat and hot water.

A Volt currently should only have about 10 kWh removed from its battery before recharging. Assume recharging is done over a period of 8 hours at night and that an input of 15 kWh is required to get 10 kWh into the battery. Then the charging load is about 2 kW. This makes my grid load at night about 3 kW vs the daytime of 2 kW.

How many of these vehicles are going to be on the grid very soon? Not many, but they might be clustered in some neighborhoods. So a few transformers have to be replaced, and a few primary lines. Not many for a lot of years. There may be more of a problem with the increase in demand for actual input energy, coal.

Quite possibly a much better direction would be the use of compressed natural gas, in combination with a hybrid function only to eliminate red light idling, initial acceleration from a stopped condition, and dynamic braking. In otherwords a minimum battery requirement. Possibly just a super-capacitor.

.

 

[T.M.Haja Sahib]

Of course it is not because you do not have any NEC knowledge.

The NEC requires continuous loads to be carried at 125%.

Funny.The OP is asking not about individual loads,but about groups of loads.It is not the maximum demand he is talking about,it is demand factor he is talking about.

 

[hillbilly1]

Funny guy.The OP is asking not about individual loads,but about groups of loads.

That is the problem, because the code does not address demand factors for groups of chargers, we have to assume that the 125% must be used for this specific application. The code making members are probably not sure how this is going to work out until enough chargers are in use to make a decision on whether or not to allow a demand factor and by how much. Costco is removing their chargers due to lack of demand.

 

[iwire]

Funny.The OP is asking not about individual loads,but about groups of loads.It is not the maximum demand he is talking about,it is demand factor he is talking about.

Funny is you telling me about the NEC. :lol:

As the poster above has stated.

There is no demand factor at all for this installation so that tells us we must carry it at 100% regardless of how many units there are.

But that is not the only issue, the code also requires we carry each unit at 125%.

Therefore the OP must carry each of the units at 125%.

 

[realolman]

.......Costco is removing their chargers due to lack of demand.

Chargers they are trying to sell, or chargers available for use by their customers in their parking lots.

How come you'd remove chargers that operate from AC, and probably don't cost anything to NOT use?

 

[hillbilly1]

Chargers they are trying to sell, or chargers available for use by their customers in their parking lots.

How come you'd remove chargers that operate from AC, and probably don't cost anything to NOT use?

Valuable parking spaces usually at the front of the store, a lot of localities prohibit with threat of fines if you park in a space designated as "EV" only.

Also there is maintance that still has to be done, even if they are not used, circuit board go bad from surges, etc.

 

[T.M.Haja Sahib]

That is the problem, because the code does not address demand factors for groups of chargers, we have to assume that the 125% must be used for this specific application. The code making members are probably not sure how this is going to work out until enough chargers are in use to make a decision on whether or not to allow a demand factor and by how much. Costco is removing their chargers due to lack of demand.

Surely, 125% should be used for maximum demand for individual load or groups of loads per NEC.NEC states that if a load is on three hours,it can be treated as continuous load.Loads on for 3 hours only and loads on for 24 hours are both continuous.But a mixture of both will not have the same maximum demand as that had by loads for 24 hours i.e.,their demand factors are different .
The OP is requesting for a thumb rule for demand factors also.So why can not the link suggested in post#2 be used for that purpose?

 

[T.M.Haja Sahib]

Funny is you telling me about the NEC. :lol:

As the poster above has stated.

There is no demand factor at all for this installation so that tells us we must carry it at 100% regardless of how many units there are.

But that is not the only issue, the code also requires we carry each unit at 125%.

Therefore the OP must carry each of the units at 125%.

You are literally too full to learn any thing more (perhaps reduction in intake of burgers,french fries,pork meat etc.,may make room for more learning.).See post #19.