Tuesday 31 August 2010

Just how environmentally friendly are electric vehicles?

Because they produce no exhaust gases in operation electric vehicles (EVs)
are seen as the eco-friendly alternative to conventional gas-fueled cars.
While zero-local emissions is clearly a big plus, other factors contributing
to the overall environmental impact of EVs are often overlooked - namely the
manufacture, usage and disposal of the batteries used to store the
electrical energy and the sources of power used to charge them. Now, for the
first time, a team of scientists from the Swiss Federal Laboratories for
Materials Testing and Research (or EMPA) have made a detailed life cycle
assessment or ecobalance of the type of lithium-ion batteries most
frequently used in EVs, to see if they really are as environmentally
friendly as their manufacturers would have us believe.


Fuel source is the key


The investigation shows that, if the power used to charge the battery is not
derived from purely hydroelectric sources, then it is primarily the
operation of the EV that has an environmental impact, exactly as is the case
with conventionally fueled vehicles. In other words, the size of the
environmental footprint depends on which sources of power are used to "fuel"
the EV. Contrary to initial expectations that the manufacture of the
batteries could negate the advantages of electric drive vehicles, the Li-ion
battery itself was actually found to have a limited effect.

The team calculated the ecological footprints of electric cars fitted with
Li-ion batteries, taking into account factors such as those associated with
the production of individual parts, the operation of the vehicle during its
lifetime, all the way through to the scrapping of the vehicles and the
disposal of the remains. The electric vehicles evaluated were equivalent in
size and performance to a VW Golf, and the power used to charge the
batteries was assumed to be derived from sources representing an average
European electricity mix - that is, a mixture of atomic, coal-fired and
hydroelectric power stations.

For comparison the team used a new petrol-engined car, meeting the Euro 5
emission regulations. It consumes on average 5.2 liters (1.37 U.S. gallons)
per 100km (62 miles) when put through the new European Driving Cycle (NEDC),
a value significantly lower than the European average. In this respect,
therefore, the conventional vehicle belongs to the best of its class on the
market.


Results


The study shows that the electric car's Li-ion battery drive is in fact only
a moderate environmental burden. At most only 15 per cent of the total
burden can be ascribed to the battery (including its manufacture,
maintenance and disposal). Half of this figure, that is about 7.5 per cent
of the total environmental burden, occurs during the refining and
manufacture of the battery's raw materials, copper and aluminum. The
production of the lithium, in the other hand, is responsible for only 2.3
per cent of the total.

"Lithium-ion rechargeable batteries are not as bad as previously assumed,"
according to Dominic Notter, coauthor of the study which has just been
published in the scientific journal Environmental Science & Technology.

The outlook is not as rosy when one looks at the operation of an electric
vehicle over an expected lifetime of 150,000 kilometers (93,205 miles). The
greatest ecological impact is caused by the regular recharging of the
battery, that is, the "fuel" of the e-car. Topping-up with electricity
sourced from a mixture of atomic, coal-fired and hydroelectric power
stations, as is usual in Europe, results in three times as much pollution as
from the Li-ion battery alone. If the electricity is generated exclusively
by coal-fired power stations, the ecobalance worsens by another 13 per cent.
If, on the other hand, the power is purely hydroelectric, then this figure
improves by no less than 40 per cent.

The EMPA team concluded that a petrol-engined car must consume between three
and four liters per 100km (or about 70mpg) in order to be as environmentally
friendly as the electric car studied, powered with Li-ion batteries and
charged with a typical European electricity mix.

http://www.gizmag.com/empa-study-environmental-impact-electric-car/16181/

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