The Electric Power Research Institute (EPRI) has released a report, Transportation Electrification: A Technology Overview, which provides projections of the commercial rollout of plug-in electric vehicles (PEVs), gives an overveiw of vehicle, plug-in and other infrastructure technologies, and suggest ways that utilities can prepare for the widespread use of PEVs in the US.
Mass Produced Consumer PEVs
The first mass produced consumer vehicles began delivery in December 2010—the Chevrolet Volt and the Nissan Leaf. As of May 31st, 2011, Chevrolet had delivered 2,510 Volts and Nissan 2,186 Leafs. It is projected that mass prduction of plug-in vehicles will happen quickly as most major manufacturers have announced production plans for PEVs.
Charging Equipment
PEVs require at least one readily available electric vehicle suplly equipment (EVSE) at their home parking location. Residential EVSE infrastructure is the highest priority because vehicles spend 66% of their time parked at home. The availability of public infrastructure allows vehicles to travel greater distances.
It is expected that most residential and public charging of PEVs will occur at power levels between 1 kW to as much as 19.2 kW with full charge times of 3 – 8 hours. Control systems on the vehicle will control the charging process. The initial installation of an EVSE can be a significant contribution to the cost of PEV ownership. Current costs for EVSE equipment range from just under $500 to several thousand dollars. Historical installation data suggests that a typical residential EVSE installation costs about $1,500.
PEV Market Projections
EPRI says there is a high degree of uncertainty about how quickly the PEV market will grow. The study considered three PEV adoption scenarios. The projections range from a low of about 1% to 4% total penetration in the US vehicle fleet by 2020.
Electric Power Demand
The really interesting part of the projections is the expected electric power demand. In the medium market scenario demand from PEVs rises to about 4.4 TWh in 2015, 16 TWh in 2020, and just under 80 TWh in 2030. (For comparison in 2008 total electric power consumption in the US was 4,156 TWh.)
Emissions Reduction
A critical metric is the impact of PEVs on carbon emissions. In the medium scenario in 2015 about 380 million gallons of gasoline are saved. The savings increases to 1.4 billion gallons in 2020, and about 7.0 billion gallons per year in 2030.
Emissions reduction in the medium scenario rises from roughly 2.1 to almost 48 million metric tons per year over the period from 2015 to 2030. Overall, the reduction is approximately 2 metric tons per PEV per year between 2010-2015. The emissions analysis takes into account the emissions from the changing mix of electric power generation facilities that produce the electricity used by the PEVs.
Charging Pattern and Impact on the Electric Power Grid
When PEV charging occurs can negatively or positvely impact the electric generation and transmission network. For example, if everyone returns home at the same time and plugs in their vehicle, this could dramatically increase peak load - in addition to air conditioners and other appliances - and would create the need for addtional (expensive) peak generation.
EPRI's analysis of passenger PEV charging at residential locations used the National Personal Transportation Survey (NPTS) as a source of driving patterns for all car users and a mature market, which may or may not correspond to driving patterns for PEV owners. Vehicle home arrival is correlated with peak load, so it is often assumed that vehicle charging would create a large load coincident with the peak. But from the home arrival distribution it can be seen that only about 12% of drivers arrive home during the peak hour of 5-6 PM.
Further analysis of this data by EPRI shows that even with uncontrolled charging the load of vehicle charging is relatively well distributed. EPRI considers three scenarios; uncontrolled charging, set-time charge control (charging starts at 9 PM) and managed off-peak. In 2015 for the medium scenario, the set-time scenario creates case a large peak of nearly a GW at 9 PM, compared to just over 300 MW at 6 PM for the uncontrolled case and about 380 MW at 2 AM for the managed off-peak case.
EPRI carried out sophisticated stochastic analyses in addition to these simple ones, and concluded that stresses on power delivery resulting from mass adoption of PEVs systems can be mitigated through asset management, system design practices, controlled charging of PEV, or some combination of the three.
EPRI recommends a proactive risk mitigation strategy to remove localized risk to the distribution system incluidng controlled charging and tariffs and rates which encourage off-peak charging.
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