Power Your Home With Your Car?
By Bill Moore
For the last 50 years, the electricity most Americans have used has been generated by large, central power plants burning coal, fuel oil, natural gas and nuclear power.
As electricity shortages in the American West have recently demonstrated, US demand for electric energy is outpacing the nation's ability to produce it or to build power plants and transmission lines to carry it.
For long-time readers of EV World, it won't come as a surprise to learn that one potential new source of electrical power may someday come from the cars and trucks we drive. (See EVWorld's earlier interview with Steve Letendre).
According to Stephen Gehl, EPRI's director of strategic technology and alliances, the average American automobile produces the equivalent of 50kW or more of electrical power, easily enough energy to power a half dozen homes at peak loads and fifty at non-peak times. While it currently isn't feasible to make use of this power, organizations like EPRI are beginning to study its potential contribution to the nation's future power needs, especially in light of developments in fuel cell and electric drive technology.
Earlier studies have focused on the potential use of a battery electric vehicle as a temporary, standby power storage medium that could be taped by the grid for peak shaving purposes.
Gehl explained that EPRI's new report entitled, "Electricity Technology Roadmap," focuses on the potential role of electric-drive vehicles that generate their own on-board power. Using a variety of carbon-based fuels like gasoline or natural gas, these vehicles -- powered by fuel cells -- will someday generate sufficient electrical power to propel the vehicle the 10% of the time it is on the road. The remaining 90% of the time it spends parked at home or at work it could be generating surplus electrical power for either the home or selling it back to the local grid.
In effect, every car or truck on the road someday may have the potential, should the owner wish it and the infrastructure is set up to accommodate it (a big IF), to be mini-electrical power generators, freeing the homeowner from dependence on the local grid. Gehl even speculates a power company might be interested in buying back some of that power, letting the homeowner even make a little money from the deal. This creates an entirely new set of potential relationships and dynamics between carmakers, vehicle owners, power companies, utility regulators, homebuilders, zoning officials... the list is lengthy.
Gehl points out that there are, "a lot of different versions of this basic concept."
"In fact," he explains, "EPRI's strongest interest right now is something called a plug-in hybrid. That's a car that would have an onboard power plant, a gasoline engine initially and possibly in the future a fuel cell, but would also have some battery storage. So, you could get part of the power requirement for running the auto from the grid, but you would be providing a lot more through the power plant onboard."
Of course, running a gasoline or natural gas-fuel hybrid car -- and currently only the former exists in the form of the Toyota Prius and Honda Insight -- as a mini, home-based power plant raises questions about both exhaust emissions and thermal efficiency. Gehl admits that in the case of a carbon-fueled hybrid, you probably wouldn't want to run the vehicle all the time to power your home. Not only would the engine generate a lot of dangerous emissions but it isn't very thermally efficient compared to a central generating plant. While a gasoline internal combustion engine operates at less than 25% thermal efficiency, modern gas turbine generators operate in the 50% efficiency range. Even taking into account 7-8% transmission line losses, centrally generated power is nearly twice as efficient as a gasoline internal combustion engine, and their emissions are more easily monitored and controlled, as well.
In contrast to the 25% efficiency of an internal combustion engine, an advanced fuel cell "engine" has a theoretical thermal efficiency reaching 40%. This places it in a favorable efficiency range with the best current gas-fired central plant when line losses are included in the calculation. In addition, if it were also possible to make use of the waste heat generated by the fuel cell stack, example heating hot water or similar home uses, a fuel cell vehicle/home power plant could be as efficient and possibly more efficient than today's gas-fired electric generators.
"What we are trying to do from a research point of view is develop vehicles with the highest efficiency under whatever operating conditions and thereby reduce the emissions," Gehl explained. "The whole question of what the emissions from this system or similar systems (are) likely to be is... an excellent question to ask, but it's really going to require an extensive research and development program in order to fully answer those questions. It's promising, but we need to do a lot more work to realize that promise."
What Makes the Most Sense, Mobile or Stationary Fuel Cells?
It isn't a foregone conclusion, by any means, where a fuel cell mini-power plant makes the most sense. Do we run the house off of a fuel cell onboard our fuel cell-powered Buick Regal someday or do we, instead, power our Ford Th!nk City off of our GE 7100 Minigen home fuel cell plant? Gehl's not completely sure of the answer to this question, either.
"The question in my mind, at least, isn't whether we are going to have fuel cells, but what type of fuel cell and where are they going to be located?" He sees several possibilities including fuel cells located in central power plants, small residential fuel cells in homes providing both electricity and hot water, as well as mobile fuel cell "engines" powering our cars, trucks and mini-vans. "There are practical considerations, pros and cons, to each of those models. I think fuel cells are likely to be an important part of the future, but exactly the role they¹ll play is something that will depend on market forces (and) the rate of technology development."
Gehl told EV World that EPRI is currently analyzing the various issues surrounding the development of a plug-in, gasoline-electric hybrid vehicle, or what the industry refers to as a "charge depletion hybrid". Such a vehicle would have a short all-electric range using battery power only. This would give it zero emission operation of twenty miles, or so, depending on the size of the vehicle, its battery capacity, etc. Beyond the twenty miles, the gasoline engine would provide motive power, as well as recharge the battery pack.
At home, the vehicle would be plugged into a electric outlet and recharged overnight. At least, theoretically, it could also be plugged in at work to either recharge or send its excess power back into the grid. In a later phase of the research, EPRI plans to look at the impact of a fuel cell EV on this scenario.
Integrating motor vehicles that generate electricity into the power grid of the future raises some interesting issues, Gehl admitted; issues for which there are, currently, no good answers. For example, if the EV owner decides to sell his power back to the local utility, what will be the price of that electricity? Gehl said that in California, where he lives and works, the state is having a hard time trying to figure out the price of electricity right now, let alone thirty years into the future.
Also yet to be resolved are a host of regulatory, liability and safety issues, all of which have slowed the growth of distributed generation in North America, which is, in essence, what this EV-as-power-plant scenario describes.
Gehl points out, by way of example, the problem with relying on solar electric panels is that they only produce power while the sun is shining. He suggests that there might be an excellent symbiotic relationship between photovoltaic panels which create electricity (or hydrogen directly) from sunlight during the day and storing that power in the form of electricity in an EV's battery pack. Or excess hydrogen not used by the home's fuel cell power unit could be stored onboard the vehicle to provide it with fuel for the next day's commute.
"These are going to be fairly complicated pieces of machinery," Gehl pointed out. "There is going to be a complex control system and sensors to insure the high efficiency performance, reliability and safety of the system. So there is a fair amount of development work that needs to be done in that area, as well; and that's part of our overall research effort."
Plug-In Hybrid Time Horizon
Gehl said that EPRI believes we might see plug-in hybrids within the next five to ten years. Fuel cell versions would be further out in a 10 to 20 year time frame.
While up to this point, carmakers have been more interested in charge-sustaining hybrid architectures like that employed in the Insight and Prius, Gehl said EPRI is working with them to explore the potential benefits of plug-in hybrid technology. He added that while many people would find a small, limited range, grid-connected hybrid electric vehicle capable of meeting most of their daily transportation needs, he emphasized that there are still many unanswered sociological questions about what type of vehicle people would be willing to own.
Gehl said he thinks that hybrid-electric vehicles are going to play a much more important role in the future than pure battery electric vehicles. "I think that the most likely role for the battery is going to be as part of the package in the hybrid. I think there will continue to be market for short range (commuter) driving and battery vehicles may be a part of that overall equation. But we think that in terms of the greatest flexibility and the most potential for succeeding in what we all admit is going to be an uncertain market in the future, we think that hybrid designs really have the advantage."
Looking fifty years into the future, Gehl said EPRI can foresee 20% of vehicles on the road then being powered by fuel cells. This presents another unexpected opportunity, he points out. Motor vehicles typically have a lifecycle of roughly ten years. By contrast, a central power plant has an operational life of 30 years or more. This means that as technology evolves in power generation, it can be more rapidly deployed in motor vehicles than it can be in large, central power generation facilities.
"This would provide opportunities for introducing new technologies on a periodic basis as that capital stock turns over," he said.
While he admits, "It's a little bit difficult to parse all these things together," he thinks that by 2050 as much as 20% of all electrical generation could be coming from fuel cell-powered vehicles.
So, ironically the power shortages of the Winter of 2001 on the West Coast -- and possible similar situations later this summer in other parts of the US -- could actually hasten the development and deployment of both plug-in hybrids and fuel cell vehicles. Such vehicles could one day insure their owners have both the electric power they need it and the affordable, efficient transportation they desire.
Finally, Gehl said his "gut instinct" is that automotive fuel cell applications will lead the industry and that "as we gain and develop more experience in operating them, there is likely to be a trend towards stationary applications."
"There is this idea of technology lock-in," he concluded. "Our automotive system has been locked in around the internal combustion engine for 100 years. It will probably take something with dramatic improvement in overall performance and public acceptance for it to get people to move away from something that may be old, but is familiar and perceived as reliable."
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