IEEE Electrification - September 2019 - 48

main benefits of battery swapping include the easing of
range anxiety, no need for fixed parking spaces, and an
improved residual value of EVs. A recent survey shows
that battery swapping can increase the driving mileage
and income of electric taxis (see Figure 6).

The Need for Battery Swapping
Early adopters of EVs in European countries and the
United States have favorable conditions for charging, as
most households have plenty of space to park EVs
along with sufficient energy supply from the utility distribution grid to charge EVs. In Norway, for example,
95% of EV owners have access to on-site charging facilities at their own homes. However, in some highly populated developing countries, it would be impractical to
perform the widespread deployment of charging outlets, primarily due to insufficient parking space and
weak distribution grids.

Shortage of Parking Space
Rapid urbanization forces residents in some developing
countries to live in crowded residential complexes made
up of multifamily high-rise buildings (see Figure 7). It is
thus a tough task to find fixed parking spaces to charge
EVs. Figure 7 illustrates the gaps between supply and
demand in parking spaces in 20 cities in China; these
gaps will grow more significant with mass motorization.
For instance, a residential complex in Harbin comprises 22
high-rise buildings but provides only 400 parking spots,
which were seemingly sufficient in the year of construction, 2002. However, in 2018, there were roughly 1,900 vehicles owned by local residents. In this case, a large number
of drivers will have no access to reserved parking spaces
for charging EVs. Fortunately, a BSS opens a new door for
them to purchase EVs.

and aging infrastructure, presenting another barrier
for deploying home-based charging piles. In fact, most
distribution lines and transformers were constructed
decades ago, so they are already on the verge of overloading due to continuous growth in the urban population. Worse still, a significant part of this aging
infrastructure has already surpassed its life expectancy (see Figure 8). Hence, deploying high-power EV chargers extensively in a frangible distribution grid will
pose great challenges to electricity security, resilience,
and economics.
Overloading is a major bottleneck for local utilities
seeking to address the massive charging needs of EV
owners, especially when a large number of EVs is
charged simultaneously during peak load hours. Peaks
in base electricity demand usually follow peaks in onroad traffic; therefore, charging EVs immediately after a
traffic peak will cause a sharp increase in the peak load.
The State Grid Harbin Utility Company has concluded
that 5% EV penetration could lead to overloading of
more than 7% of transformers in Harbin residential
areas, and the case could get even worse in some legacy
distribution grids.
Moreover, EV charging will distort the quality of the
low-voltage power supply in some unbalanced distribution grids with long feeder lines. EV chargers are
high-power, nonlinear devices based on power electronic converters [see Figure 8(c)-(e)]; this will induce a
significant amount of current and voltage harmonics
in the adjoining distribution grid. Table 1 lists some
power quality standards for EV chargers and charging
stations in China. These standards, however, are not
silver bullets to eliminate the impact of EV charging on
power quality.

Environmental Issues
Weak Distribution Grid
In some developing countries, power distribution networks are vulnerable in terms of insufficient capacity

219 km
159 km

Driving Mileage Comparison
Battery Swapping Group

Pollution is, surprisingly, another major issue related to
the widespread adoption of EVs. If the electricity that
powers EVs is produced by coal-fired generators, EVs

¥356

Income Comparison
¥272

Charging Group

26
Average Mileage
per Day

% of Taxis With Monthly
Mileage More Than 6,000 km
(a)

Battery Swapping Group

Average Income
per Day

% of Taxis With Monthly Income
More Than ¥10,000
(b)

Figure 6. Graphs comparing essential statistics for electric taxis using charging stations and BSSs: (a) Daily and monthly driving mileage and
(b) daily and monthly income.

I E E E E l e c t r i f i cati o n M agaz ine / SEPTEMBER 2019

IEEE Electrification - September 2019

Table of Contents for the Digital Edition of IEEE Electrification - September 2019