1

Distribution Capacity Impacts of Plug In Electric Vehicles

Chris Punt, P.E.

MIPSYCON 2014

2

Outline

►EV Benefits

►EV Growth

►Where are we today?

►Where are we going?

►Potential Distribution Capacity Issues

►Feeder

►Sub Transformer

►Service Transformer

►Other Activities

►Conclusion

3

Benefits of Electric Vehicles ►Environmental Impacts

►Can run on renewables

►Higher conversion efficiency

►Emissions - Easier to filter pollutants

►Economics

►Energy cost is 1/3 compared to gas

►Can make up for Utility revenue reductions

►Energy Independence

►North American Electricity

►Eliminate Price Volatility

►Driving Experience

►Smooth

►Low noise

►Instant Torque - Acceleration

4

Most Popular U.S. EVs - 2014

22 EV Models

►Nissan Leaf

►Chevrolet Volt

►Toyota Prius PHV

►Tesla Model S

►Ford Fusion Energi

►Ford C-Max Energi

5

Electric Drive Transportation Association - http://en.wikipedia.org/wiki/File:US_PEV_Sales_2010_2013.png

6

2400 EVs in MN through 2013

7

Xcel Energy Area EV Interest and Gas Prices

3

3.2

3.4

3.6

3.8

4

Jun-

12

Jul-

12

Aug-

12

Sep-

12

Oct-

12

Nov-

12

Dec-

12

Jan-

13

Feb-

13

Mar-

13

Apr-

13

May-

13

Jun-

13

Jul-

13

Aug-

13

Sep-

13

Oct-

13

Nov-

13

Dec-

13

Date

$/g

allo

n

-90

10

110

210

310

410

510

610

710

# o

f E

V In

qu

irie

s

MN Gas Prices XCEL EV Interest

8

Where are we today?

►Minnesota Public Charging

► 165 electric stations

► 360 charging outlets

►ChargePoint

►Tesla

►Dealerships

►Goodwill

►United States

► 8,672 electric stations

►21,525 charging outlets Department of Energy - http://www.afdc.energy.gov/fuels/electricity_locations.html

9

Where are we going?

► Initial Xcel Energy Estimates

►Tesla Charging Stations: 100,000 kWh per year

►Home Charging: 56,000,000 kWh to date

► 2014 Legislation in MN – EV Charging Tariff

►All Public Utilities will file an application to the MNPUC by February 1, 2015

►Must contain TOD or off-peak rate

►Must offer customer opportunity to purchase from renewable sources

►Must be made available to residential class

10

Annual Energy

11

Charging

►Level 1

►120V – 1.1 to 1.8 kW

►11 - 20 hours for full charge

►Level 2

►240V - 3.3 to 7.7 kW, 19.2 kW

►3 - 8 hours for full charge

►Level 3 – DC Fast Charge

►Three phase

►15 to 240 kW

►1/2 - 2 hours

12

Charging – Tesla Supercharger

13

Chevy Volt Charge Profile

►Level 1

►9 hours

►Li-ion Am

ps

14

Distribution Capacity Analysis

►Feeder

►Substation Transformer

►Service Transformer

15

Feeder Analysis

►Two St. Paul Feeders – served from same substation transformer

►Typical, indicative of Xcel Energy’s planning philosophy

►Feeder A

►36% residential load (multi-family)

►77% loaded

►13.8kV

►Feeder B

►80% residential load (single family)

►65% loaded

►13.8kV

16

Feeder Analysis

►Varying Level 2 residential penetration rates

►3.3 kW

►6.6 kW

►Assume all charging occurs at peak.

►Penetration = EV/Residential Customer

►Assumption: 1 EV per customer

Penetrations

0%

1%

2%

5%

10%

15%

25%

35%

50%

75%

17

Feeder Analysis – Feeder A

Feeder "A" Capacity vs 6.6 kW Penetration

70.0%

90.0%

110.0%

130.0%

150.0%

170.0%

0% 10% 20% 30% 40% 50% 60% 70% 80%

Feeder "A" Capacity vs 3.3 kW Penetration

70.0%

80.0%

90.0%

100.0%

110.0%

120.0%

0% 10% 20% 30% 40% 50% 60% 70% 80%

18

Feeder Analysis – Feeder B

Feeder "B" Capacity vs 6.6 kW Penetration

60.0%

80.0%

100.0%

120.0%

140.0%

160.0%

0% 10% 20% 30% 40% 50% 60% 70% 80%

Feeder "B" Capacity vs 3.3 kW Penetration

60.0%

70.0%

80.0%

90.0%

100.0%

110.0%

120.0%

0% 10% 20% 30% 40% 50% 60% 70% 80%

19

Feeder Analysis – Takeaways

►For every 1% penetration we see 0.5% - 1% demand growth on both feeders.

►Capacity significance starts around the 4% penetration mark.

►i.e. 2% - 4% demand growth

20

Feeder Analysis Takeaways

kW per

customer

3.3 kW

slope

Load Normalized 3.3

kW slope

Feeder A 2.1 0.51 1.2

Feeder B 3.5 0.56 0.56

►Feeder makeup matters

►% residential

►Type of residential

►Areas with lower kW/customer will see more impact from same penetration levels.

21

Sub Transformer Analysis – Present Case

Penetration 3.3 kW 6.6 kW

0% 46.6% 46.6%

1% 46.9% 47.2%

2% 47.2% 47.9%

5% 48.2% 49.8%

10% 49.9% 53.2%

15% 51.6% 56.5%

25% 55.0% 63.2%

35% 58.4% 69.9%

50% 63.5% 79.9%

75% 72.2% 96.6%

Diversity Factor of 81%

22

Transformer Analysis – Worst Case

Penetration 3.3 kW 6.6 kW

0% 57.5% 57.5%

1% 57.9% 58.3%

2% 58.3% 59.1%

5% 59.5% 61.5%

10% 61.6% 65.7%

15% 63.7% 69.8%

25% 67.9% 78.0%

35% 72.1% 86.3%

50% 78.4% 98.6%

75% 89.1% 119.3%

Diversity Factor of 100%

23

Transformer Analysis – Takeaways

►For every 1% penetration we see 0.3% - 0.8% demand growth.

►Less raw impact compared to feeders due to diversity

►Capacity Impact starts at over 5% penetration

►In most cases feeder limits will be reached before transformer limits (if designed/planned properly)

24

Service Transformer Analysis Load Profile for XFMR "237412633" date: 7/14/10

0

20

40

60

80

0:00 2:00 4:00 6:00 8:00 10:00 12:00 14:00 16:00 18:00 20:00

Time

kv

a

New Peak with Chargers

25

Service Transformer Analysis – Known Additions

►Took 46 known EV owner locations and their service transformers

►Analyzed for addition of Level 2 Charging

Peak Load Addition % of Population Overloaded

1 – 3.3 kW charger 4%

1 – 6.6 kW charger 9%

26

Service Transformer Analysis – All NSPM

►4%-5% penetration leads to $2.3M - $4.6M in upgrades

►Does not account for multiple installations per transformer

Additional Peak

Load

% of Population

Overloaded

Cost to

Replace (M) Penetration

1 – 3.3 kW charger 3% $4.7 8.8%

1 – 6.6 kW charger 5% $9.3 8.8%

27

28

Projection

►2.5% EV share leads to 5% penetration (2024 on low adoption from previous slide)

►4% of transformer population overloaded

►$7M - $10.7M to upgrade (proactive – reactive)

►Revenue far exceeds costs over ten years

►No significant feeder or sub transformer impact for 10+ years

29

PSCo EV Pilot Project

►Deliverables (early 2015)

►Determine residential charging characteristics

►Identify alignment with system peak

►Distinguish a potential strategy for minimizing distribution impact through control

30

EV Project

►Funded by ECOtality and Department of Energy

► 13,000 Level 2 Chargers

►Feeder and EV Peaks don’t align

►Typically EV connected to EVSE 40% - 45% of time but draws power only 8% - 9% of time

31

Conclusion

►EVs are here and growing

►Impact generally starts occurring at around 5% penetration when peak aligned

►Service transformers are of biggest concern, especially with multiple EVs

►Locating Level 2 charging and above necessary

►Charging at night desired with possibility to control later on

32