Environmental Engineering Reference
In-Depth Information
1.8 Grid connected hybrids
Grid connected hybrids are considered here because some of the 'fuel' used for
propulsion is derived from burning low grade fossil fuels or non-fossil fuels and the
transmission of that energy to the hybrid vehicle's storage system via the nation's
electricity grid. Connected hybrids have been proposed for many years, but only
recently has there been renewed interest due to emissions in urban areas and
attempts to legislate ZEVs or ZEV equivalent electric-only range hybrid vehicles.
However, an overloaded national grid (because of no new investments during the
past decade in NA) is now looming as an impediment to grid connected vehicles.
1.8.1 The connected car, V2G
The case for a connected car rests on the fact that most electricity produced in NA
comes from non-petroleum sources and the fact that interconnection of many such
grid accessible vehicles has benefits beyond just transportation. Reducing our
reliance on liquid fossil fuels takes two forms: (1) conservation of existing fuels
and (2) substitution of alternative fuels. Conservation measures are already in effect
through various legislated means to regulate transportation use fuel economy, non-
transportation efficiency improvements such as building lighting (e.g. initiatives
such as dark-skies building and electrical codes) and industrial motor efficiency
programmes (US Energy Conservation Act). Substitution of alternative fuels
means a transition away from liquid fossil fuels to natural gas, hydrogen or non-
conventional energy generation such as solar and wind power. According to Tom
Gage of AC Propulsion [19], any vehicle that plugs into the electric power grid and
draws some or all of its energy from the grid will achieve both conservation and
substitution.
The basic premise of the connected car is that a large portion of its commute
range can be on energy stored on board that was delivered by the electric grid. This
offsetting of petroleum consumption could be significant, according to Mr Gage.
For example, a 40 mpg hybrid with 30 mi of electric-only range could use grid
electricity for two-thirds of its operation, yielding a petroleum fuel economy
equivalent of 120 mpg. The second benefit of connected cars is that these parked
vehicles represent a highly distributed source of generation, or vehicle to grid
(V2G) infrastructure. This concept of using on-board power assets for off-board
consumption is not new. Other companies have developed hybrids that use either
the engine driven M/G as a power source for off-board portable power such as
power tools (the GM contractor special) or fuel cell powered vehicles as an elec-
tricity source for home power.
These V2G vehicles offering off-board benefit would be classified under SAE
J1772 as level 1 through level 3 (Table 1.15):
Level 1: 110 V
ac
at 1.5 kW
●
Level 2: 240 V
ac
at 7.6 kW
●
Level 3: 240 V
ac
and >7 kW
●
