What's a plug-in hybrid-electric car?

Like any hybrid car, a plug-in is a vehicle with a gasoline-powered internal combustion engine and, also, a battery-powered electric motor. Either the engine, or the motor, or both can power the wheels. The balance between the two shifts continuously depending on how much power is in the battery and how hard you're pressing the accelerator. Furthermore, excess energy from the engine -- and the wheels, during braking -- recharges the battery.

What's different about a plug-in is that it's got a larger battery than a regular hybrid -- much larger. In the Prius we drove (converted to plug-in by the lithium-ion battery wizards at A123 Systems of Watertown, Mass.), the battery fills the space under the trunk where the spare tire should be. (Who needs a spare anyway?) Also, as the name suggests, a plug-in has an electric socket, so you can charge the battery by patching the car into the electric grid at home or work. (That's what my son Peter is doing in this photo.) Thanks to these additions, plug-in hybrids are more electric-powered than gas-powered. Think of them as battery vehicles with back-up gasoline engines. As the placards on Rob Lowe's trial model declared, a plug-in can easily go more than 100 miles per gallon. (Of course, that's a one-eyed claim, since plug-ins operate more on kilowatt-hours than gallons.)

How did it drive?

Fine, thanks. Driving a plug-in hybrid is like driving any other car. There's not much to say. You push the accelerator and it goes. What's different? It's really quiet, even quieter than a regular Prius.

In fact, the main differences my kids noticed were the luxury car features, not the battery-electric ones. Unacquainted with Hollywood-sized bank accounts, they've rarely set their car-less feet inside an auto so new and loaded with features. They liked the leather interior and, especially, the computer monitor centered in the dashboard. It displays real-time navigation instructions, maps your location, and utters directions -- with perfect diction, in a woman's voice. (Whose voice is that? I want to know.) When you shift into reverse, the monitor converts to a closed-circuit TV screen and shows what's behind you. My son Peter and his friend took turns standing behind the parked car and watching the screen. Again, none of this has anything to do with the car being a plug-in. It has to do it with being Rob Lowe's. Apparently, you can get such features on most new cars. (Being car-less, I had no idea!)

As for me, I enjoyed the gauges and graphics that indicated what power source I was running and what my fuel economy was. Or, I should say, I enjoyed the gauges and graphics for the first 48 hours. For the remaining 48 hours, the dashboard beeped incessant warnings. "Problem" flashed relentlessly on the computer screen. The only way I could stop the alerts was to turn off the bonus battery kit. Just before our use of the car ended, a technician from A123 returned my call and explained how to reboot the control system to "clear the error." (One problem with a car that's half computer is, well, it's half computer.)

No doubt, plug-in makers will iron out such problems before the vehicles hit the market. Road testing is one purpose of Seattle's pilot project. And no one anticipates mass-market plug-ins for a few years, in any event. The largest consumer pilot test yet was recently announced in northern California, and it will involve only ten cars.

What's remarkable is how unremarkable it was to drive this revolutionary new car design. During our short (pre-beep) time with it, the plug-in provided the same performance as any other new car, with less mess: the same comfort and speed, with fewer economic, environmental, and military repercussions.

That's the good news.

Actually, it's only the beginning of the good news. Since driving the car, I've been studying up on plug-ins, and they've got lots to love.

The good news: Plug-in hybrids ...

Are perfect for normal days. On any given day, about half of American cars, pickups, vans, and SUVs cover 20 miles or fewer, according to the Pacific Northwest National Labs in Richland, Wash. (PDF). So even though plug-in hybrids have a limited all-electric range, a range of just 20 miles per battery charge (roughly what Rob's plug-in has) would be enough to quench the daily energy demand of half the U.S. fleet. That's right, half the fleet would burn no gas on any given day.

Tap unused generating capacity. The same paper demonstrates that the existing U.S. electric power generation, transmission, and distribution systems have ample unused capacity to charge up plug-ins' batteries during off hours, mostly at night. Demand for electricity is intermittent and fluctuates both daily and seasonally. In most parts of North America, the entire electric power infrastructure is fully utilized only about 5 percent of the time. Plug-in vehicles could charge up in the off-peak hours, using onboard timers or more sophisticated "smart grid" mechanisms. (This point is often misunderstood: it's not that plug-ins charge up on electricity that would otherwise go to waste; it's that power plants have unused capacity. That is, they could operate more of the time, and the extra juice they make could fill plug-ins' batteries.)

Help us get off oil. Without a single new power plant or high-tension wire, the U.S. electricity grid could supply 73 percent of the energy needed by its light duty vehicles. Getting that much transportation energy through the electric grid, rather than through the petroleum distribution system, would trim U.S. oil imports by half! It could also prevent -- and help moderate the economic impacts of -- oil price shocks, while keeping more dollars circulating locally.

Cut fuel bills. Electricity is far less expensive per mile driven than oil: it's like buying gasoline for under a dollar a gallon. And because charging vehicle batteries in off-peak hours would dramatically increase sales of power and allow the amortization of capital costs over more kilowatt hours, the price of electricity would probably decline.

Increase energy flexibility. Electricity is a more versatile energy carrier than gasoline, ethanol, or biodiesel. It's far easier to transport than liquid fuels and increases energy options. For example, plug-in hybrids can put electricity back into the grid, to help balance loads or increase security.

Boost energy efficiency. In technical, engineering terms, electricity is an efficient energy carrier, whether compared to conventional fossil fuels or hydrogen or biofuels. The makers of the all-electric Tesla sports car make this point well in a geek-alicious presentation you can watch here (click "view presentation").

Can store renewable power. Plug-in hybrid vehicles, with their capacity to stockpile electricity, are a much-needed complement to the continued expansion of wind, solar, and other intermittent renewable power sources. On-board batteries could soak up any unused power that flows from wind and solar installations when the winds blow or the sun shines, then use the power whenever it's needed.

Clean the air where people live. Plug-in hybrids would improve urban and suburban air quality, thanks to plug-ins' near-zero-emissions from driving. And while emissions of health-threatening pollutants from electricity plants would increase, those plants are typically far removed from population centers. What's more, power plants' grand scale makes advanced pollution control systems economic. The industry-supported Electric Power Research Institute and the environmental lobby Natural Resources Defense Council joined together to study the air quality implications of a sudden and sweeping shift to plug-in hybrids. They assumed a worst-case scenario in which almost all of the new power came from coal-fired plants and concluded that emissions of most health-threatening pollutants would diminish markedly.

Could slash greenhouse gas emissions. According to the most comprehensive study of the question yet completed, again by EPRI and NRDC, rapid adoption of plug-in hybrids between now and 2050 could -- repeat, could -- slash U.S. greenhouse-gas emissions by billions of tons, cumulatively. (I know, following the numbers of climate protection is confusing: millions, billions, tons, pounds, barrels. Suffice it to say, billions of tons is a lot -- a big deal.)

The bad news:

Emissions today. For starters -- and notwithstanding any future greenhouse-gas benefits -- driving a plug-in hybrid right now in North America probably increases climate-warming emissions, compared with driving a regular hybrid. Why? In a nutshell, because most of a plug-in's electricity comes from coal-fired power plants.

Now, you might think that running a plug-in hybrid on Cascadian electricity would mean running it largely on emission-free hydropower. But that's a mistake. You see, every watt of hydro and wind electricity that we produce is already spoken for, used to satisfy demand somewhere here or elsewhere in the western power grid. So consuming local power (usually, hydropower) to charge plug-ins means that, somewhere else on the grid, another coal-fired plant has to rev up just a bit to replace the power sucked down by the car's batteries. Until renewable power becomes so abundant that we get virtually none of our power from dirty coal plants -- until we have long periods of each day when we have no other use for some of our wind and solar and hydro power -- any marginal demand for baseline power (the night-time power that can recharge plug-in hybrids) will most likely be met by increased generation from coal. (In fact, because of Cascadia's lack of coal plants, PNNL counts us as the North American region least ready for plug-ins. Ouch.)

Trading gasoline for coal-fired power is a bad deal for the climate. This chart adapted from the EPRI/NRDC report illustrates the situation. The chart shows that, if the electricity that charges a plug-in's batteries comes exclusively from coal, the total climate-disrupting emissions per mile from a plug-in exceed the emissions from a regular hybrid. (Sorry, Rob. I know that's got to hurt.)

(I added a note at the bottom explaining more about this chart, for the data hungry.)

Emissions tomorrow. Even though today's power grid doesn't make plug-ins a good deal for the climate, EPRI and NRDC find that replacing gasoline and diesel vehicles with electric ones will eventually be a climate plus -- assuming the electric power system gets cleaner over time. But that's a big assumption. The only guarantee of clean plug-ins (like those shown in the shortest bars of the chart) would be a firm, descending legal limit on greenhouse-gas emissions.

So in essence, the real barrier to reducing vehicle emissions isn't car technology at all. It's the law. Once we've capped greenhouse-gas emissions from all sources and implemented an economy-wide tax or cap-and-trade system (auctioned, please!), we can be sure that plug-ins will deliver on their potential climate benefits. Until then, plug-ins will likely be slightly worse for climate than regular hybrids.

Batteries are inconvenient. Inventors are improving batteries in a hurry, as this article from the electrical engineering journal Spectrum details. But they're still a long way from the finish line. Even the best batteries are limited in range, lifetime, and recharge speed. Despite all the high-tech wizardry we can throw at the problem, electricity remains wickedly difficult to store.

Liquid fuels like gasoline and diesel, on the other hand, are terrifically convenient. In less time than it takes your traveling companion to get back from the loo at Exxon, you can pump enough fuel into your tank to drive hundreds of miles. In contrast, recharging your state-of-the-art lithium-ion battery with 20 miles' worth of electricity takes hours, maybe even all night. And unlike fuel tanks, the storage capacity of batteries shrinks over time, and may eventually require costly replacements.

Cost. Charging a plug-in's batteries is cheap, especially compared with $3-a-gallon gas. But the batteries themselves are pricey. (The all-electric Tesla sports car's half-ton battery system alone costs almost as much as a new Prius, according to the same Spectrum article.) Even the most devout evangelists of plug-in hybrids point to the problem of battery cost. For example, MIT's Gerbrand Cedar, one of the inventors of the technology behind A123's battery design, estimates in this presentation that battery costs need to come down by about 60 percent for plug-in technology to compete in the market.

The hype cycle:

Three of the five trips I took in Rob Lowe's former ride were delivering carloads of kids to soccer games. (I had parenting debts to pay.) One thing I'll say: the plug-in brought squads of people around to talk -- far more than have ever noticed us arriving by tandem bicycle or bus. The experience set me thinking about the psychology of vehicle technology.

In 1999, at the height of the fuel-cell craze, I remember listening to car makers and science writers foretelling the imminent arrival of the hydrogen economy. Soon thereafter, hype turned to disillusionment. More recently, biofuels have followed a similar trajectory, in which expectations blossomed far faster than actual market presence and, when unrealistic expectations were not met, the popular sentiment began to switch to rejection. Plug-in hybrids are becoming the new "it" technology in Cascadia, and I worry they'll fall from favor as quickly as their predecessors.

These technologies all hold promise, plug-ins possibly more even than the others. Fixating on car technology, however, is part of the problem. It perpetuates the hype cycle: every new fuel or power train design leads to a whirlwind romance, followed, eventually, by disenchantment. And the drama distracts from less glamorous but ultimately more effective, political and institutional solutions, such as auctioned cap-and-trade systems, carbon taxes, and complete, compact communities, not to mention feebates, decoupling, efficiency improvements, congestion pricing, and pay-as-you-drive auto insurance -- and even ride hopping, high-tech hitch-hiking, better public transit, walkshed mapping, and (my current passion) Bicycle Respect.

When we make these changes collectively, through our democratic institutions, vehicle technology will take care of itself. Investors will finance new product development. Consumers will select those products that meet their needs at a price they're willing to pay. Plug-in hybrids will compete head-to-head, with fuel cells, biofuels, bicycles, conventional technologies, and perhaps alternatives we do not yet imagine. And I'll decide, like everyone else, whether to buy a plug-in hybrid car. For now, though, I'm staying car-less.

Besides, as this photo shows, our car-less trunk is almost as big as Rob Lowe's.

Boring details about the chart, in case you're interested: Extracting, transporting, and especially refining petroleum burns a lot of oil. The resulting greenhouse gases, shown in blue, are called "well to tank" emissions (measured in this chart in grams of CO2 equivalent). The emissions, shown in red, from your exhaust pipe are called "tank to wheels." The emissions that come from the electric power system are shown in yellow. As you can see, total emissions per typical mile are higher for a plug-in running on electricity from an old or new coal-fired power plant than for a regular hybrid.

The plug-in hybrid reduces emissions if it's run on power from a natural-gas-fired power plant, especially from one of the better ones, which are called combined cycle plants. Unfortunately, plug-in hybrids are unlikely to charge up on natural-gas power because of the costs of operating natural gas plants. Utilities tend to operate them mostly in peak periods, because their fuel is expensive. What's more, natural gas prices are rising because North American natural gas production has peaked and hauling the stuff across oceans is expensive. Plug-ins cause much less climate pollution than regular hybrids if they're juiced up on renewables or "advanced coal with sequestration." This last option, technically called "integrated combined cycle gasification with carbon capture and storage," is an experimental technology with promise but also a lot of technical barriers still to cross. Read more about it in this book by Simon Fraser University's energy guru Mark Jaccard.