Plug-In hybrids to replace hybrids

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WHY THE FUTURE IS HYBRID
Dec 2nd 2004

Automotive technology: Hybrid petrol-electric cars such as the Toyota
Prius are becoming increasingly popular. But are they any more than a
rest-stop on the road to the hydrogen car?

WHY has the Toyota Prius become the car industry's most talked about
product? Since 1997, only about 250,000 have been sold, a paltry number
by the industry's standards. The Prius is hardly big, fast or
beautiful--the attributes that usually appeal to commentators,
aficionados or, for that matter, buyers. And yet it is significant
because it is the world's first mass-produced petrol-electric hybrid
car, powered by both an internal-combustion engine and an electric
motor. The second-generation Prius, launched in 2003, won some of the
industry's most prestigious awards--it has just been named European Car
of the Year 2005--and generated a buzz out of all proportion to the
car's prevalence on the roads.

By choosing to drive a Prius, buyers can demonstrate how green they are
without paying any penalty other than a slightly higher purchase price.
Compared with a new American car of the same size, the Prius consumes
roughly half as much petrol, and so releases half as much
climate-changing carbon dioxide. Moreover, its emissions of
smog-forming pollutants, such as nitrogen oxides and hydrocarbons, are
90% lower. Yet the Prius still manages to deliver the comfort and
performance of a conventional car.

The success of the Prius has taken Toyota by surprise. The average wait
at American dealerships is currently six months, even though the
company increased its sales target for North America from its initial
estimate of 36,000 units to 47,000 for 2004. To meet demand, Toyota
announced another increase in August, saying it would push monthly
global production up next year by 50% to 15,000 cars, and double its
allotment for America to 100,000 units. While that number is still only
one-quarter of last year's sales for America's most popular Toyota
model, the Camry, it shows that consumers are willing to pay a premium
for clean, environmentally friendly cars--as long as there is no need
to compromise on performance.

Other carmakers are scurrying to catch up. CSM Worldwide, an automotive
research firm, reckons that at least 20 new hybrid models will appear
in America by 2007. Besides this year's new Ford Escape and Honda
Accord hybrids, Toyota will add two sport-utility vehicles (SUVs) to
its hybrid line-up early next year. DaimlerChrysler recently announced
that it will introduce a Mercedes hybrid within the next five years,
and Porsche is considering a hybrid version of its Cayenne SUV. Even
General Motors, one of the strongest proponents of hydrogen fuel-cell
cars, has jumped on the hybrid bandwagon with two pick-up trucks, a
sedan and several SUVs to follow. Thanks to the convergence of
geopolitics, technology and fashion, hybrids are picking up speed.

AN OLD NEW IDEA
While the arrival of mass-produced hybrids is new, the idea itself is
not. Indeed, it dates back to early automotive history when cars
powered by electric motors, steam or internal-combustion engines all
accounted for significant shares of the market. Why hybrids failed then
is best illustrated by the example of an American engineer named H.
Piper, who filed a patent for a petrol-electric hybrid vehicle in 1905.
His idea was to use an electric motor to assist an internal-combustion
engine, enabling it to achieve a thrilling 40kph (25mph). Unfortunately
for Mr Piper, petrol-powered internal-combustion engines achieved those
speeds on their own just a few years later, undermining the more
complex and expensive hybrid approach. Petrol engines soon ruled the
roost.

Priorities began to change in the early 1970s, when the oil crisis
increased demand for less fuel-thirsty cars. As a result, the overall
fuel efficiency of cars and trucks improved dramatically (though it
stalled in America in the late 1980s as cheap petrol and a regulatory
loophole encouraged sales of SUVs and light trucks). Moreover, in the
1990s, concern began to grow over the impact of fossil-fuel consumption
on climate change.

During the 1990s, all of the big three American carmakers developed
diesel-electric hybrid concept cars, though none made it into
production. Instead, the focus shifted to pure-electric vehicles, which
are technologically simpler than hybrids. But their high cost and
limited range deterred consumers. Even the most advanced models could
only go about 100 miles before they needed to be plugged in and
recharged for several hours. By 2000, most electric cars had been taken
out of production.

Meanwhile, Toyota released its first Earth Charter in 1992, setting the
goal of minimising its overall environmental impact. In September 1993,
the company began to plan the development of a car for the next
century, dubbed Globe 21st Century, or G21. Originally, the plan was to
produce a car with 50% better fuel economy than existing vehicles. But
over the course of the project this target was raised to 100%, at which
point it became clear that tweaking a petrol engine would not suffice.
Instead, a more radical solution would be needed: a hybrid.

Despite the higher cost and complexity of a hybrid system, Toyota
decided to press ahead with a massive research and development effort.
Improved technology--such as better batteries and cheaper, more
powerful control electronics to co-ordinate the two propulsion
systems--meant that a mass-produced hybrid was now feasible. In 1997,
the Prius was launched in Japan. It was followed by Honda's Insight
hybrid in 1999.

When the Prius went on sale in America in 2000, it did not cause much
of a stir. Indeed, even last year, Honda and Toyota sold about the same
number of hybrids in America. This year, however, Toyota will sell
about twice as many as Honda. The Prius took off thanks to the
combination of rising petrol prices, celebrity endorsements and a
futuristic redesign. (There is no petrol version of the Prius, so the
car makes a statement in a way that the Honda Civic, which is available
in both petrol and hybrid versions, does not.) It is the first hybrid
to become a hit.

HYBRID ANATOMY
There is more to the Prius than clever marketing, however. To
understand why, it is necessary to look under the bonnet at the way
different kinds of hybrids work--for not all hybrids are the same. The
simplest kind is the "stop-start" or "micro" hybrid, which is not
generally regarded as a true hybrid because it relies solely on an
internal-combustion engine for propulsion. As the "stop-start" name
implies, the engine shuts off when the vehicle comes to a halt. An
integrated starter-generator restarts the engine instantly when the
driver steps on the accelerator. All of this increases fuel efficiency
only slightly, typically by around 10%. But few modifications to a
conventional design are required, so it costs very little. In Europe,
PSA Peugeot Citroen has just introduced a stop-start version of the
Citroen C3, which sells for roughly the same price as a similarly
equipped conventional C3.

Next come so-called "mild" hybrid designs, such as Honda's Integrated
Motor Assist (IMA)--the hybrid configuration found in the Insight, the
Civic and the new Accord. In addition to a stop-start function, an
electric motor gives the engine a boost during acceleration. During
braking, the same motor doubles up as a generator, capturing energy
that would otherwise be lost as heat and using it to recharge the car's
batteries. Since the electric motor is coupled to the engine, it never
drives the wheels by itself. That is why this system is called a mild
hybrid, much to Honda's dismay. The design is less expensive than
Toyota's more elaborate approach, but can provide many of the same
benefits, says Dan Benjamin of ABI Research, a consultancy based in
Oyster Bay, New York. The hybrid version of the Civic achieves 48 miles
per gallon, a 37% improvement over a comparable conventional Civic.

Toyota's Hybrid Synergy Drive, a "full" hybrid system, is much more
complex. (The Ford Escape hybrid uses a similar system; Ford licenses a
number of patents from Toyota.) Using a "power split" device, the
output from the petrol engine is divided and used both to drive the
wheels directly and to turn the generator, which in turn drives the
electric motor and also drives the wheels. The distribution of power is
continuously variable, explains David Hermance of Toyota, allowing the
engine to run efficiently at all times. When its full power is not
needed to drive the wheels, it can spin the generator to recharge the
batteries. The batteries also get replenished when the car is coasting
or braking. During stop-and-go traffic and at low speeds, when the
petrol engine would be most inefficient, it shuts off and the electric
motor, powered by the battery, takes over. That explains why the Prius
has a better fuel economy rating for urban driving (60 miles per
gallon) than for motorway driving (51 miles per gallon)--the opposite
of a conventional vehicle.

The next step may be the "plug-in" hybrid, which is not the backwards
step its name suggests. Unlike the electric cars of the 1990s, none of
today's hybrids needs to be plugged in--but if plugging were an option
it would be a good idea. Andrew Frank and his team at the University of
California Davis' Hybrid Electric Vehicle Centre are working
exclusively on plug-in hybrids, which can operate as pure-electric
vehicles over short distances (up to 60 miles, with a large enough
battery pack) but can switch to a hybrid system when needed. Since the
average American driver travels about 30 miles a day, plug-in hybrids
could be recharged overnight, when electricity is cheaper to produce,
and need never use petrol at all, except on longer trips.

According to studies carried out by the Electric Power Research
Institute (EPRI), a non-profit organisation based in Palo Alto,
California, plug-in hybrids could be one of the cleanest and most
efficient kinds of car. In 2002, the EPRI teamed up with
DaimlerChrysler to build five plug-in hybrid vans, the first of which
was unveiled at a trade show in September. The larger battery packs
make the upfront costs for plug-ins higher than for other hybrids. But
Bob Graham of the EPRI says the added costs could be more than recouped
over the vehicle's life.

Not everyone is bothered by high fuel consumption, however, as the
current enthusiasm for enormous SUVs demonstrates. So hybrids seem
likely to remain a niche: ABI Research predicts that by 2010, less than
5% of all cars sold in America will be hybrids, assuming current petrol
prices persist. But if Alan Lloyd has his way, hybrids and other
low-emission vehicles will become far more commonplace. Dr Lloyd is
head of the California Air Resources Board (CARB), a state agency that
enforces arguably the most stringent air quality rules in the world.
California recently passed landmark legislation to curb the emissions
of greenhouse gases by 30% beginning in 2009. Since carbon-dioxide
emissions are directly linked to a car's fuel consumption, critics
charge that the new rules are in effect a way to legislate fuel
economy, which is supposed to be regulated by the federal government,
not the states. As a result, carmakers are expected to challenge the
new rules in court.

Sales of hybrids in Europe are a fraction of those in America. Instead,
diesel cars have become Europe's answer to reduce fuel consumption,
curb greenhouse emissions and save money at the pump. Because diesel
fuel contains more energy per unit, the fuel economy of diesel cars is
roughly 30% better than that of petrol-powered cars. Moreover, diesel
cars are not as loud or dirty as they once were, thanks to technologies
such as electronically controlled "common rail" fuel-injection systems.
Diesels now make up about 45% of all newly registered cars in Europe.

Even so, they still lag behind petrol engines in terms of cleanliness.
In the process of combustion, diesels create a lot of pollution,
including nitrogen oxides which cause smog, and particulate matter that
can cause respiratory problems. That said, some carmakers have begun to
equip their cars with particulate filters, notably PSA Peugeot Citroen.
Together with two British firms, Ricardo and QinetiQ, the company is
building a diesel-hybrid based on the family-sized Citroen Berlingo.
The aim is to achieve a combined fuel economy of 70 miles per gallon
with carbon-dioxide emissions of only 90 grams per kilometre. (In
comparison, the Prius delivers 55 miles per gallon with carbon-dioxide
emissions of 104 grams per kilometre.)

While it is uncertain whether the car will be mass produced, it is
clear that a diesel-electric hybrid would make for an extremely frugal
vehicle. A study by the Laboratory for Energy and the Environment at
the Massachusetts Institute of Technology, which looked at energy use
over the course of a vehicle's life, predicts that by 2020, diesel
hybrids could achieve the same energy-efficiency and greenhouse-gas
emissions as fuel-cell cars powered by hydrogen made from natural gas.
The difference is that diesel-hybrid technology is available today.

So why are diesel hybrids taking so long to appear on the roads? Hybrid
diesels impose a double price premium, explains Lindsay Brooke, an
analyst at CSM Worldwide. Combining a diesel engine, (which costs
around $2,000 more than a petrol engine) with a hybrid powertrain
(which adds another $3,000 or so) would make for an expensive
proposition. Systems to treat the exhaust would impose further costs.
The prospects for diesels and diesel hybrids are particularly dim in
America, where regulations in California (and, from 2007, nationwide)
require diesels to be as clean as petrol-driven cars. Some progress has
been made: particulate filters can now eliminate more than 90% of
diesel soot. But traps for nitrogen oxides remain a challenge.

THE CAR OF THE FUTURE, TODAY
Hydrogen fuel-cell vehicles promise to be the cleanest mode of
transportation, eliminating harmful tailpipe emissions altogether. But
despite much publicity, and the fact that most carmakers are working on
the technology, fuel-cell cars will not appear in significant
quantities any time soon. America's National Academy of Sciences, which
advises the government on new technologies, recently estimated that the
transition to a "hydrogen economy" will probably take decades, since
many challenges remain--in particular, how to produce, store and
distribute hydrogen in sufficient quantities.

Hybrid cars, however, offer many of the benefits of fuel-cell vehicles,
with the huge advantage that they are available now. Moreover, as the
success of the Prius shows, people will actually buy them. The beauty
of petrol-electric hybrids is that they do not require any changes in
driver behaviour or the fuel-delivery infrastructure.

Rather than being mere stepping-stones on the way to the hydrogen cars
of the future, petrol-electric hybrids are likely to be around for
years, if not decades, to come. When and if fuel-cell cars become
available down the road, they may not replace hybrids, but instead are
likely to be descended from them, since they require many of the same
components, from control systems to motors. As Joseph Romm, director of
the Centre for Energy & Climate Solutions, a non-profit organisation
based in Arlington, Virginia, puts it, "hybrids are almost certainly
the platform from which all future clean vehicles will evolve."