NREL's future vision: vehicle-to-grid/renewable communities
- Plugging In to Renewable Communities
How transportation based on renewable
energy-powered communities may solve our addiction to fossil resources.
By Terry Penney and Jennifer Elling
[See original for excellent graphics]
Terry Penney is the FreedomCAR and Advanced
Vehicle Technology manager at NREL, Golden, Colo.
Prior to joining NREL in 1979 as an aerospace
engineer, he worked on the space shuttle. He has
worked on hybrid vehicle technology since 1992.
Contact Penney at terry_penney@.... Jennifer
Elling is a senior communicator and project lead
for the Renewable Community at NREL. Contact
Elling at jennifer_elling@....
What if you could virtually eliminate your
reliance on petroleum and the associated concerns
about greenhouse gas emissions and national
security without giving up your personal car?
Better yet, what if the infrastructure to power
this fossil fuel-free vehicle was tied to your
neighborhood electric grid, one that distributed
electricity generated from renewable energy to
your home and plug-in hybrid electric car? Your
advanced plug-in vehicle would be designed to
draw electricity from the combined renewable
energy grid or a plug-in renewable energy system.
Plug-in vehicles are like todays hybrid
vehicles, but with bigger, more costly batteries
and a smart control strategy. Now consider that
in this community, not only would renewable
energy (RE) power the homes and businesses, but
buildings would be built for maximum efficiency
and on-site solar heating and electricity
generation to use zero or near-zero energy from
the grid. Most of the pollution, health and
national security concerns of fossil fuels would be a thing of the past.
Researchers are quickly moving toward developing
the technologies to support just this type of
sustainable transportation infrastructure and
RE-based community. Many of these innovations are
here today, and we catch the first glimpse of
what these communities might look like as more
builders construct developments in which most or
all of the homes are solar and use near-zero
energy. The paradigm-shifting difference in the
renewable energy community to come rests in the
single integrated, RE-based energy system for
transportation and residential/commercial buildings.
Driving Vehicle-to-Grid Technology
Because this renewable community will be
connected to a grid that operates in two
directions both distributing and accepting
electricity the next-generation hybrid electric
vehicles will have the ability to store excess
electricity for timely return to the grid. We
call this two-way plug-in a vehicle-to-grid
(V2G) hybrid. Utilities spend a tremendous amount
for capacity to continuously balance supply and
demand across the grid or provide backup
electricity during outages and peak-demand
periods. Because batteries are particularly
effective for this kind of critical service,
utilities might pay V2G owners to borrow
energy-storage capacity (see sidebar, Linking It
All Together). Combined with fuel savings, this
income could pay back the more expensive battery
cost within relatively few years.
As federal regulators and electric utilities work
to revamp the aging North American electricity
transmission and distribution infrastructure,
they have the opportunity to reduce our nations
increasing reliance on imported oil by creating
mechanisms to encourage clean distributed
generation, including V2G. This combined power
grid will enable utilities to tap a source of
competitively priced backup electricity, while
investors will have a means of profiting from the
possible transition to renewable energy.
Batteries, such as those used in a V2G-enabled
car, are one of many new clean and distributed
resources that could contribute to a smart grid
of the future. This smart grid would communicate
continuously with both suppliers and consumers of
electricity to maintain the most secure,
cost-effective system. It will require
cost-effective advanced interconnection equipment
that allows full functionality of a V2G plug-in
hybrid. Consensus-based standards for these vehicles also must be developed.
This effort is just one of the critical areas on
which researchers are focused. At the National
Renewable Energy Laboratory (NREL), experts are
working to advance smart control systems in
vehicles to make V2G technology a reality and to
create a more efficient, reliable distribution
system. Probably the biggest challenge to
commercialization of plug-in hybrids is the cost
and weight of batteries. NREL is researching
thermal-management, modeling and systems
solutions to improve energy-storage technology
(see the sidebar, Overcoming the Battery
Technology Challenge). Even at today's battery
costs, however, plug-ins may be able to repay
their costs within a few years. NREL scientists
and engineers also research improved power
electronics and smart control systems critical to
hybrid efficiency and conduct sophisticated
modeling and analysis to demonstrate the economic
viability of plug-ins and identify key areas for improvement.
Envisioning the RE-Powered Community
Lets examine what the sustainable communities
that underpin the V2G paradigm will look like.
Imagine living in an RE-based community in a few
years that emphasizes low utility bills and
reduced petroleum use. It is designed using
sustainable practices and materials to minimize
the environmental damage of site development and
conventional energy and water use and to promote quality of life.
Your zero- or near-zero-energy home is
constructed for maximum comfort and energy
efficiency, with appliances and heating and
cooling systems that dramatically reduce the
electricity demand. Rooftop photovoltaic (PV)
power-generating systems supply most of the
little energy the house does need. Excess PV
generation is used to charge your V2G hybrid or
is sold back to your electric utility company.
The V2G in the garage operates mostly on
$0.03-per-mile electricity rather than
$0.10-per-mile gasoline. The hybrid vehicles
batteries store extra electricity for the home as
a backup to the PV system. In this way, the
vehicle actually may serve as a mobile utility.
The local utility generates energy from wind,
solar and other renewable sources the small
amount of grid electricity your home may need.
What little fuel the V2G needs may also be
generated from renewable sources, such as ethanol
or biodiesel in the near term, or hydrogen for
the vehicles fuel cell in the long-term.
Nearby workplaces and commuter stations could
also have two-way electrical outlet docks to
enable battery charging or, when the V2G car is
not in operation for long periods, to provide
electricity back to the grid. Many high-tech
companies already have auxiliary generators
because they need more consistent power than the
grid provides, and such companies might be
delighted to rely on employee car batteries
instead. As for the town, our streets will be
clean and quiet because V2Gs would run on their
electric motors much more than regular hybrids.
Operating in electric-motor mode would also mean
greatly reduced emissions from the vehicles themselves.
Creating the V2G Reality
Sound like a pipe dream? It isnt.
Energy-efficient homes, PV systems, geothermal
heat pumps and other effective renewable energy
technologies are offered by many homebuilders or
suppliers. Commercially available plug-in hybrids
are just years away. Integrating multiple energy
systems is the key, and the technology to do so
is available today. Yet cost, risk, consumer
demand, and other issues cause business to pause
at the opportunity. With the team of experts at
NREL, weve begun to respond to these issues by
analyzing a number of renewable community
scenarios that link transportation, homes and the
electric grid, as well as enabling the delivery
of large quantities of renewable energy to the
grid. Analyses show that the homeowner would gain
a net cost advantage by integrating a
near-zero-energy home with a plug-in or V2G
hybrid. Although a number of variables affect
this calculation, the economics of the integrated
system are substantially better than an analysis of each piece would suggest.
For example, typically a near-zero-energy home
with PV panels and energy-efficient measures can
be expensive, raising the initial cost of this
home. When included in original construction cost
in the home mortgage however, energy use can
be reduced as much as 50 percent with no increase
in total monthly bills. For instance, a U.S.
Department of Energy handbook
(www.buildingamerica.gov) for hot and humid
climates posed an example of spending an
additional $1,500 for an ENERGY STAR home
(including various energy-efficiency features,
but not PV or a geothermal heat pump). For an
additional mortgage cost of only $9 per month,
energy bills were reduced $40 per month for net
savings of $31 per month. As another example, for
a 2,600- square-foot, two-story home in
Sacramento, Calif., efficiency measures can be
added cost-effectively to achieve 60 to 65
percent energy savings. At an incremental cost of
about $20,000 and assuming a $600,000 asking
price in the California market, this investment
represents an upfront cost increase of only 3
percent. In addition to immediate savings in
utility bills, added PV electricity-generation
and other energy-savings features will also be
paid back in home resale value.
Establishing the renewable community with V2Gs,
of course, requires much more interaction among
disparate disciplines. It requires a fresh look
at state and local zoning laws. This transition
may seem like a difficult undertaking, but when
we consider escalating housing and utility costs,
we find that the effort and investment have the
potential to pay off by many measures.
Developing Transportation-Wise Suburbs Today
Your home and car probably represent your biggest
personal impact on our nations increasing energy
demand, and therefore on national security, trade
deficits, global warming and air quality. The
renewable communities concept presented in this
article marries energy-responsible homes and cars
for a sustainable lifestyle. By leveraging new
technologies and sustainable building practices,
RE-based communities can demonstrate that it is
possible to minimize the detrimental effects of
fossil energy, while addressing the greatest
energy challenges of the American suburban lifestyle.
Our team at NREL views renewable communities
using V2G technology as an ideal way to
demonstrate the effectiveness of the wide range
of energy-efficiency and renewable energy
technologies the laboratory is helping to
develop. Rooftop photovoltaic and utility-scale
solar thermal systems are a prime option.
Depending on location, the community can also
rely on wind, solar thermal or biomass energy.
Our analysts can model the near-zero-energy
buildings to identify the most cost-effective
efficiency measures, model the V2G vehicles to
identify optimal battery and other component
sizes and matches, and design systems to most
effectively use the communities' mix of
distributed and central electrical generation.
Ethanol from cellulosic biomass can supply what
liquid fuel the vehicles must use. We see
renewable communities as a path to minimizing
energy import, fossil-fuel use and greenhouse gas
emissions, while providing the highest-quality lifestyle.
What will it take to start building these
renewable communities? Any new venture involves
risk, but we believe Americans are eager to live
in communities that minimize their contribution
to greenhouse gases and reduce national
dependence on imported oil. Several organizations
and business entities have contacted us about
this vision, and we see elements of it around the
world. It is only a matter of time before we see
integration of all the pieces of advanced
technology, putting us on a path to
sustainability based on renewable energy. Its
not a question of if, but of when, who and
where this vision will become a reality.
A Glimpse of the V2G Future Today?
How soon could we have vehicle-to-grid (V2G)
plug-in hybrid communities? None exist yet, but
Global Electric Motorcars (GEM) gives us a
glimpse of what they might look like. The leading
maker of neighborhood electric vehicles, or NEVs,
and a DaimlerChrysler company since 2000, GEM has
sold its vehicles to entire communities that
feature NEVs as part of their basic
infrastructure. In Bay Harbor, Mich.;
Celebration, Fla.; and Playa Vista and Otay
Ranch, Calif., entire neighborhoods use NEVs for nearly all local travel.
Linking It All Together
What makes the renewable energy-based community
of the future unique is the integration of the
electric utility system with a system to power our personal vehicles.
[GREAT GRAPHIC] Source: Dean Armstrong, NREL
The interconnected energy system can flow two
ways, as shown by the arrows in this graphic. A
two-way plug-in hybrid vehicle (also known as a
vehicle-to-grid, or V2G, vehicle) is plugged into
an electric outlet in the garage of the home or
workplace, allowing electricity to flow from the
energy-management system (traditionally the grid)
to the vehicle and vice versa. An
energy-management operator can broadcast a
control signal to any number of V2Gs (including
fleets) to give or request electricity. Each
vehicles smart control system monitors its
ability to give and receive electricity and
communicates this information with the operator.
Overcoming the Battery Technology Challenge
If battery technology is the key to realizing the
benefits of plug-in hybrid vehicles, then the
thermal management of these batteries is
essential for their longevity and performance.
During the past 10 years, the National Renewable
Energy Laboratory (NREL) has developed a
world-class laboratory for energy-storage thermal
management. The lab uses the latest modeling
software, hardware and thermal-imaging techniques
to improve the performance and design of advanced
batteries such as nickel-metal hydride (NiMH),
lithium-ion and lithium polymer batteries.
2001 Panasonic NiMH module
Redesigned 2004 Panasonic NiMH module
These infrared images taken at NREL show how
Panasonic improved the thermal performance of its
NiMH module. The 2004 module has a lower maximum
temperature and is much more uniform. The U.S.
Department of Energysponsored work at national
labs and industry is aimed at overcoming the
barriers to implementing advanced batteries in
vehicles such as cost, calendar life, abuse
tolerance and low-temperature performance. Access www.nrel.gov.