While the renewable energy community is generally supportive of PHEVs,
they have yet to fully appreciate the new opportunity that this would
create for their industry. As the vehicle fleet moves toward at least
partial electric drive and grid charging, this creates the opportunity for
renewables -- beyond biofuels -- to serve as a source of energy for the
transport sector.
Although solar photovoltaics (PV) is not viewed as cost-effective without
significant subsidy when compared to grid power, it begins to look
interesting when compared to the price of gasoline for transportation.
Furthermore, the opportunity that solar hybrids offer is exciting, whereby
a new generation of solar PV technology is developed specifically for
vehicle integrated (VIPV) applications (see
Solar Today, May/June
2006, Letendre, Perez, and Herig).
Growth in VIPV applications could one day mimic the current explosion in
new product development for building integrated PV applications. While PV
may serve just a small part of a vehicle's overall energy needs, the
modest additional costs from a 500 watt VIPV system may be well worth the
investment. VIPV should be considered as an avenue to enhance a PHEV's
overall efficiency, similar to regenerative breaking.
It is generally understood that PHEVs would charge during the evening and
early morning hours when electricity demand is low and there is
significant excess capacity available on the network. In some areas, wind
resources are strongest at night, thus allowing wind power to serve as an
energy source for vehicles. With smart charging, the rate of charging
could be adjusted to match the power production from a distant wind farm.
I can envision interesting marketing schemes whereby PHEVs are sold in
conjunction with a wind power supply contract further enhancing the
vehicle's "green" attributes.
The potential of grid connected cars is even more exciting when the notion
of vehicle to grid (V2G) is considered. The emerging V2G concept envisions
grid connected cars with bi-directional chargers that both accept power
from the grid and deliver power to serve different ancillary services
markets. Initial economic analyses suggest that V2G capable vehicles could
generate significant revenue for vehicle owners by providing specialty
grid services such as regulation (frequency response) and spinning
reserves. Ratepayers pay over $1 billion for these services each year.
The battery wear and tear from providing these services would be minimal
given that regulation services would include both charging and discharging
energy from the vehicle's battery pack in response to signals from a grid
operator striving to maintain grid frequency at 60 Hz. Spinning reserves
is another ancillary service needed to maintain grid reliability; these
reserves are infrequently called upon, and when they are dispatched, are
only used for a short duration and thus would have minimal impact on the
vehicle battery pack.
While a small number of PHEVs have been built and are being tested, there
are still hurdles to be overcome, the most important of which is the
batteries. The U.S. Department of Energy recently convened experts from
across the country to discuss the potential of PHEVs. While batteries were
identified as a key technical challenge, the general consensus was that
this barrier can be overcome. Additional research and development funding
should be directed toward developing advanced batteries for PHEV
applications. There is general agreement among electro chemical engineers
about the potential that lithium-ion (Li-ion) batteries offer in serving
the hybrid vehicle market. In fact, several battery companies are
currently developing Li-ion battery packs for vehicle applications.
A more distant potential that grid-connected cars may offer is their role
in serving as storage to allow greater penetration of intermittent
resources on to the nation's electric grid. I envision a future with
millions of vehicles connected to the electric grid providing storage to
allow large amounts of wind and solar to become seamlessly integrated in
to the electric grid ushering in a truly sustainable energy future. In
addition, PHEVs would require less liquid fuels making it more likely that
biofuels could meet the challenge of displacing 100% of petroleum as a
transport fuel.
While the renewable energy community must address a number of issues, I
would urge renewable energy industry associations and advocacy
organizations to join the growing chorus directed at the major automobile
manufacturers to commit to bringing PHEVs to the market place.
Grid-connected cars offer many fascinating opportunities to allow
renewables to play a greater role in fueling society's transportation
needs.
About the author...
Steven Letendre serves as the Director of Research at the Prometheus
Institute for Sustainable Development, located in Cambridge, MA. Dr.
Letendre has over ten years of research experience in the field of
renewable energy. He has published widely on the topic of solar energy and
advanced vehicle concepts. Dr. Letendre has served as a consultant on a
range of projects for a variety of organizations including the National
Renewable Energy Laboratory, California Air Resources Board, Union of
Concerned Scientists, Northeast Sustainable Energy Association, and SUNY
Albany's Atmospheric Sciences Research Center. Prior to joining the
Prometheus Institute, Dr. Letendre was an Associate Professor of Business
and Environmental Studies at Green Mountain College in Poultney, VT. In
1997, he received a Ph.D. from the University of Delaware in Urban Affairs
and Public Policy with a concentration in energy policy and economics. In
addition, he holds a masters degree in economics from Binghamton
University, formerly State University of New York at Binghamton. Prior to
pursuing his doctoral studies, Letendre was employed as an energy
economist with the Research Triangle Institute in North Carolina.
The information and views expressed in this article are those of the
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