Modelling embedded technologies in energy service networks - Modelling Distributed Energy Resources in Energy Service Networks - page 75

Table 4.4 Well-to-wheel energy efficiency of several eco-friendly vehicle models

Technology Model Energy source η W 2 V η V 2 W W 2 W

ICE Toyota Camry Crude oil 0.82 1.23 1.09

Honda Civic Crude oil 0.82 2.27 1.86

HEV Toyota Prius Crude oil 0.82 2.47 2.03

PHEV Chevy Volt Coal 0.32 4.00 1.28

Chevy Volt Natural gas 0.42 4.00 1.68

BEV Tesla Roadster Coal 0.32 6.10 1.95

Tesla Roadster Natural gas 0.42 6.10 2.56

Nissan Leaf Coal 0.32 6.66 2.13

Nissan Leaf Natural gas 0.42 6.66 2.80

BMW Mini E Coal 0.32 7.14 2.28

BMW Mini E Natural gas 0.42 7.14 3.00

vehicle models by using the well-to-wheel energy equation ( W2W ) that measures
the travel distance obtained per unit of energy used (km/kWh) [207]. The W2W equa-
tion is popular within the literature and follows the energy content of the fuel from its
original source up to its point of consumption by a particular type of vehicle model;
this can be described as:

W 2 W = η W 2 V · η V 2 W (4.41)

where η W 2 V is the well-to-vehicle performance measured as percentage
η V 2 W is the vehicle-to-wheel performance measured in km/kWh

As Table 4.4 shows, depending on the fuel source used to charge their batteries
and focusing strictly on an energy efficiency perspective ( i.e. discarding costs and
emissions), both PHEV and BEV models have a similar or enhanced performance
than that of ICE and HEV units. This fact is easily seen for the circumstances in
which the models outperform even the best HEV model; these vehicles (depicted in
the table with bold) posses a η V 2 W value greater than 6 and obtain their electricity
from a gas fuelled combined cycle power plant. Still, whenever coal is the fuel source
considered, the W2W value of the vehicles suffers a setback. Evidently, the W2W value
of each PHEV unit will depend on its battery efficiency and the fuel mix employed
to supply them with electricity [208]. Thus, it is indispensable for energy generation
to become less carbon intensive, otherwise the energy efficiency benefits PHEVs
provide will be forsaken.
The W2W energy performance of both PHEV and BEV technologies should
benefit as more renewable sources of generation ( e.g. wind power) position them-
selves as an important contributor to the fuel mix of a region or country. Further-
more, similar to the W2W equation, it is possible to compute the W2W emissions of
the vehicles as seen in Table 4.5. In this manner the environmental impact of replacing