The study was funded by the US Department of Energy's National Renewable Energy Laboratory (NREL), and it reports the substantial fuels savings that could be realized by a fleet of plug-in hybrids with as little as 20-mile battery range.
In the article that follows, other NEVCOR publications on sustainable technologies are referenced in the endnotes. Links to those that are available online are also provided.
Planting solar cells? Driving plug-in hybrid cars?
These are immediate steps that can lead to energy independence.
In the interests of full disclosure, NEVCOR is engaged in renewable energy research, so you'd expect that we'd be in favor of planting corn for ethanol fuel, right?
Wrong. We're in favor of planting solar cells.
Solar cells. Various studies1 suggest that an acre of Iowa's best corn fields could yield about 300 gallons of ethanol annually. That's enough fuel to drive a very fuel-efficient 5-pasenger car roughly 10,000 miles annually.
Suppose, instead of planting corn, you planted solar cells and harvested the electricity? How far could you drive an electric vehicle -- or even better, a plug-in hybrid electric vehicle (PHEV)?
The answer (drum roll): 1 million miles. That's 1,000,00 miles on emissions-free, solar-generated electricity.
How's that possible?
Quite simple. A field of solar (photovoltaic (PV)) cells can convert incoming sunlight to electricity with a conversion efficiency of 10 percent which is much higher than a corn plant can convert sunlight into corn.
And the case for solar cells gets even better. It takes a lot of energy (including fuels) to plant, cultivate, harvest, and process that corn into ethanol and then transport it to your neighborhood service station. Some researchers2claim that it will actually take more petroleum-based fuel to do all that than the ethanol you'd get from the effort; in other words, a losing proposition. And this planting and processing would be repeated, year after year, with each new crop.
On the other hand, plant those solar cells once and you'll be harvesting electricity for the next thirty years. That 30-year number is a guarantee the solar cell manufacturers give you today right out of the box. Emissions-free electricity for 30 years, guaranteed.
How would you get that electricity to where I need it?
Quite simple. With a black box by the corn field and a few wires, the utility can hook the solar cells into their wires running along the road by the corn field. And those wires eventually connect to the electrical outlets you now have in your house...and garage. Plug your car in and, presto, you're charging with electricity from those solar cells.
But my garage isn't anywhere near that corn field. In fact, it's not even in Iowa. By the time that electricity reaches my garage over thousands of miles of wires, will there be any electricity left?
Very good question. Actually, it isn't necessary to plant those solar cells on Iowa farmland...or on any farmland. Plant them on rooftops. Like the barn on that farm, or the farmhouse, or on any available rooftop. Like on your house.
My house? My house isn't very big. That couldn't work.
Yes it could, assuming you don't have trees shading your roof. For example, a 1982 study3 showed that a PV roof on a 3-bedroom single-family home in Fresno, California could meet all of the energy needs of the house with enough electricity left over to charge an electric car for 20-40 thousand miles annually.
That sounds like a lot.
It is a lot. In California, more than 40% of all energy goes into houses and cars. The rest goes into industry, commerce and the rest of transportation (e.g., aviation, trucking, rail, etc.). That Fresno house could be a net-energy producer for the utility. And the daytime electricity it would provide to the grid is considered high-value peak power.
But aren't solar cells expensive?
They used to be, but they are continuing to drop in cost, even as the costs of conventional sources of energy--including petroleum--keep going up. In certain applications, solar-electric generators have become the most cost-effective new source of electricity for the utilities.4 The utilities are now actively promoting the wider use of solar power.
Well, the utilities also promoted the wider use of electric cars, but they remained quite expensive. And the best would only go about a100 miles on a full charge; it was like starting a trip in a conventional car with only a quarter tank of gas...and recharging took hours, assuming you could find a place to plug in. Not a secure feeling.
That's why we mentioned plug-in hybrid cars. They could solve all those problems.
What's a plug-in hybrid car?
Well, there are lots of different designs, but one patented in 19805,6could be plugged in to any available standard (110 V or 220V) wall receptacle for recharging. If you did plug it in, say overnight, then the next day you could drive 20 miles on electricity alone. If that day you drove 20 miles or less, then you wouldn't use any gasoline at all. That night, you could plug in again and repeat the cycle, day after day.
Suppose you had to go further than 20 miles?
The gasoline engine would kick in, and you could go as far as you wanted. Same full-tank feeling of security you got from your conventional car.
Still, 20 miles doesn't seem like that much. Would that really make much of a dent in gasoline use?
Yes, it would. A 1996 study7 of plug-in hybrids, Policy Implications of Hybrid-Electric Vehicles, showed that among all the personal autos on the road in the US on any typical day, half of them would actually travel that day 20 miles or less. That same study showed that if the US fleet of autos were plug-in hybrids with 20-mile battery range and they were plugged in at night, gasoline use would be reduced from 40 billion gallons annually to roughly 23 billion gallons.
Wouldn't the cost of batteries push the price of the car up?
Yes, but not by as much as you might think. The Toyota Prius has proved to be a very marketable hybrid, in spite of the extra cost for its battery and associated hybrid drive components. And as the hybrid technology improves and the market grows, the costs are likely to fall further.
Have any car companies expressed interest in plug-in hybrids?
Yes, DaimlerChrysler has teamed with the Electric Power Research Institute (EPRI) to develop a prototype plug-in hybrid Sprinter van8 with a 20-mile battery range. Think about it—20-mile battery range would be enough for half of all the drivers on the road on any typical day. It would take years before automakers could build enough vehicles just for the buyers who would be satisfied with 20-mile all-electric range. And, of course, that initial market will help to lower prices and improve the technology. As batteries get better and cheaper, PHEVs could have greater and greater all-electric range.
But what about the electricity? It's got to be generated from something. Isn't some of that petroleum?
Very little. The vast majority of all electricity comes from other sources and almost all of that is indigenous to the US. And we just talked about getting more and more of that from solar cells on our rooftops (as well as from wind-powered generators and other renewable sources)
Could you really plug in all those cars overnight without overloading something?
Yes, you could plug in all those cars and not have to add any new generators or powerlines, as long as you plugged them in at night.
I guess that's when you'd want to plug them in, right?
That's right, that's when you'd want to recharge them. But you might want to plug in during the day when the utility might pay you to provide it some juice.
Yes, this story just keeps on getting better. In 1980, the same US patent mentioned above9showed that a plug-in hybrid car could provide heat and electricity to the dwelling (and electricity to the grid itself). Recent studies have suggested that the utility might find it profitable to pay you for the service you rendered.
The utility would pay me?!
The electric utilities are getting more interested in all of these ideas, and you can request a recent report entitled “Sustainable Communities – Business Opportunities for the Electric Utility Industry”10 from the Electric Power Research Institutein Palo Alto, CA. There's also an article published in the 2002 Encyclopedia of Physical Science and Technology entitled “Electric and Hybrid-Electric Vehicles”11that fills in some of the details.
Where does the hydrogen fuel-cell car fit in to all this?
PHEVs will be the best thing that ever happened for fuel-cell cars. Affordable fuel-cell cars are still a very long way off, but PHEVs will help to speed the day they do arrive. Fuel-cells can replace the engine in PHEVs whenever they become available and affordable. Meanwhile, in the near term, PHEVs using gasoline or diesel engines can begin the transition to grid electricity as a transportation fuel, thereby reducing fuel use.
Sounds like a win-win.
You got it.
1 Allen, Mike, “How far can you drive on a bushel of corn?” Popular Mechanics, May 2006.