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NREL's future vision: vehicle-to-grid/renewable communities
May 4, 2006 (From the CalCars-News archive)
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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
http://www.solartoday.org/­2006/­may_june06/­plugging_in.htmhttp://www.solartoday.org/­2006/­may_june06/­plugging_in.htm

[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 today's 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 nation's 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 Let's 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 vehicle's 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 vehicle's 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 isn't.

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, we've 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 nation's 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. It's not a question of "if," but of "when, who and where" this vision will become a reality.

3 Sidebars: 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 vehicle's 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.


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