IEEE Power & Energy Magazine - May/June 2014 - 31

Synchronous condensers are expected to re-emerge as a tried
and tested approach to maintaining a stiff grid voltage for stable
operation of the grid of the future.

may/june 2014

owner. in addition to the energy production cost savings,
there are savings due to avoided power generation and delivery infrastructure otherwise needed to support increased
peak demand driven by uncontrolled charging.
uncontrolled ev charging can result in a substantial
increase of peak load and a deterioration of system load factor. the peak-load increase could drive a substantial, and
uneconomical, increase in generation, transmission, and
distribution capacity to support this peak. of these, the generation capacity costs to meet increased peak are typically
dominant. if ev charging is appropriately controlled, the
required energy can be supplied without an increase in peak
system demand, and thus the high costs of incremental generation capacity to support ev charging can be avoided or
deferred. controlled ev charging could prove to be a significant beneficial asset for managing light load system operational challenges. however, even with the control of system
peak demand, there may be the impact of ev charging on

Baseline
Smart Charging
Uncontrolled Charging

(MW)

1,500

1,000

500

(%)

continue to need strong incentives and a relatively high cost
of gasoline to be viable. a key driver for these vehicles in the
united states is the desire to reduce u.s. dependence on oil
and reduce tailpipe emissions. today there is strong policy
support with a u.s. tax credit of up to us$7,500 for new evs
and Phevs, which substantially covers the cost of the battery system, estimated today to cost as much as us$10,000
per vehicle, depending on the vehicles' range.
at today's gasoline and electricity prices, it will be some
time before evs are truly a cost-competitive alternative to
conventional gas-fueled vehicles without policy support. if
the cost of batteries is substantially reduced and a new car
buyer, who drives 10,000 mi per year, is faced with a decision to buy a us$35,000 Phev or a us$30,000 gas-fueled
vehicle, the driver should still opt for a gas-fueled vehicle
if economics are the determining criterion for the buyer.
today, a toyota Prius achieves 51 mi/gal. a Phev driving
in all-electric mode is the favored alternative to a Prius only
when gasoline prices exceed us$6/gal, assuming that the
Phev is charged with us$.18 per kWh electricity. even if
the price of electricity were us$.07 per kWh, the price of
gasoline would still need to exceed us$4/gallon for the economic value of the Phev to exceed that of the Prius. this
is shown in Figure 3. at today's fuel prices, lower battery
costs and stronger incentives are needed for these vehicles to
make substantial inroads into the transportation sector. even
if the cost of the battery falls by 50%, incentives will still
be needed to enable widespread growth of evs and Phevs.
it took more than ten years for hybrid vehicles to constitute
2.5% of the u.s. vehicle market. it may take many years for
evs to reach a significant portion of the vehicle fleet.
if evs are able to gain a substantial share of the automotive market, they will drive substantial load growth. a
recent Ge study showed that, for one region, transitioning
10% of the light-duty vehicle fleet to evs would increase
the load energy by ~5%. the implementation of a charging infrastructure for evs and Phevs offers a substantial
new business opportunity. For the system studied, "smart"
vehicle charging costs 19% less than serving uniform load
growth, while completely uncontrolled charging costs 24%
more (see Figure 4). these savings could be used to invest in
the technologies needed to enable smart charging, provide
customer incentives that promote controlled charging, and
provide savings to customers. For the system examined, the
difference in energy production cost between uncontrolled
and smart charging equated to ~us$300/year per Phev

130
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100
90
80
70

Three Typical Days
Marginal Variable Cost (US$/MWh)

Baseline

Uncontrolled
Smart
Charging
Charging

figure 4. Marginal variable cost of serving the EV load for
two EV charging strategies, with respect to the marginal
cost of serving uniform load growth. (Used with permission
from "Integrating Electric Vehicles into the Power System,"
2011 CIGRE Symposium.)
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Table of Contents for the Digital Edition of IEEE Power & Energy Magazine - May/June 2014