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Mitigation of Vehicle Fast Charge 

Grid Impacts with Renewables and 

Energy Storage 

Mike Simpson

National Renewable Energy Laboratory

8 May 2012

NREL/PR-5400-55080
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Electric Vehicle Grid Integration

2 

Cross Cutting Enablers

Grid / Renewables

Communities

Vehicles 

SMART GRID 

& COMMUNICATION

RENEWABLE 

GENERATION 

INTERMITTENCY

POWER 

ELECTRONICS 

EFFICIENCY

INFRASTRUCTURE 

CODES & 

STANDARDS

BUILDING 

ENERGY 

MANAGEMENT

GRID 

OPERATION & 

RELIABILITY

ENERGY 

STORAGE 

LIFE & COST

STRATEGIC 

ENERGY 

ANALYSIS 

VEHICLE 

SYSTEMS 

ANALYSIS 

& TESTING

DEPLOYMENT & 

PARTNERSHIPS

Tx

Tx Tx
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Vehicle Test Facilities at NREL

Photo by Dennis Schroeder, NREL/PIX 19699 Photo by Dennis Schroeder, NREL/PIX 20040

Photo by Dennis Schroeder, NREL/PIX 19757

Photo by Dennis Schroeder, NREL/PIX 20045
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How Will Fast Chargers 

Impact the Grid?

• How will drivers use fast chargers?

• What does the time-dependent demand 

look like?

• How does the aggregate fast charge 

demand correlate with grid peaks? 

• How can photovoltaics (PV) and energy 

storage reduce the impact and thus the 

cost of fast charging?
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Fast Charge Grid Impact 

Mitigation

• Identify system benefits

- Add efficient, electric transportation miles cost effectively

- Enable competitive performance from all-electric vehicles

• long-distance travel fueled with renewables

• Address fast charging concerns / barriers

- Minimize power spikes on the local grid

- Avoid exacerbating peak demand

- Reduce system costs

- Quantify battery utilization
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Approach/Strategy

Real World 

Driving Profiles

• Multiple fast charges of both 

CHAdeMO compliant 

vehicles

• Real-world traffic patterns 

[Puget Sound Regional 

Council Traffic Choices 

Study] and solar data 

incorporated 

• Simulation assesses impacts 

of multiple vehicle adoption 

rates and station 

configurations

• PV and storage sizing 

conducted to mitigate impact
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VTIF: Fast Charge Data Acquisition

Leaf Fast Charge Profile

i-MiEV Fast Charge Profile

NREL PIX #20144
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Model Assumptions

Assumption Value Units/Notes

Vehicle State-of-Charge Window 80% Min: 10%, Max: 90% 

Vehicle Energy Consumption Rate 300 Wh/mi 

Forgetfulness Factor 10% User forgets to plug-in roughly 1 

in every 10 days of driving 

Home Charge Power 3.3 kW

Fast Charger Efficiency 85% Source-to-Battery 

Fast Charger Power (max) 50 kW

Fast Charger Max SOC 80% Charger cuts off at 80% SOC

Stationary Battery SOC Window 75% Min: 15%, Max: 90%

• Home charging begins at midnight if the car is stationary and the driver 

doesn’t forget

• Fast charges occur only secondary to home charging when, in the middle of 

a trip, the battery approaches minimum SOC
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Simulations Indicate High Potential 

Utilization

Fast charges occur most 

frequently in the evening, 

often coinciding with grid 

peak demand 

relative frequency
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One Week’s System Operation

Assuming 4 ports, 200 vehicles, 24 kWh per 

vehicle, 100-kW PV, 100-kW stationary battery 
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Single Day System Operation

200 PEVs,100-kW PV, 100-kWh Battery

Assuming 4 ports, 200 vehicles, 24 kWh per 

vehicle, 100-kW PV, 100-kW stationary battery 
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Avoiding expensive energy and 

demand charges on your bill...

Assuming 4 ports, 200 vehicles, 24 kWh per 

vehicle, 100-kW PV, 100-kW stationary battery 
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Reduced Wait Times with 

More Installed Ports
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Conclusions

• Fast charge utilization simulation 

developed

• Grid impact options identified

• Next steps:

– Include economics in design of experiments
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Special Thanks to:

Lee Slezak and David Anderson, 

Vehicle Technologies Program, 

U.S. Department of Energy

Questions?

Mike.Simpson@NREL.gov