Tuesday, August 31, 2010

Li-ion batteries in electric cars greener than believed

For the first time, researchers at Empa have made a detailed life cycle assessment (LCA) or ecobalance of lithium-ion (Li-ion) batteries, in particular the chemically improved (i.e. additional environmentally friendly) version from the ones most frequently utilized in electric vehicles.

The investigation shows that if the energy used to charge the battery is not derived from purely hydroelectric sources, then it is primarily the operation with the electric automobile, which has an environmental impact, precisely as is the case with conventionally fuelled automobiles.

The size with the environmental footprint depends on which sources of energy are applied to "fuel" the e-mobile.

About the other hand, the Li-ion battery itself has a limited impact about the LCA on the electrical automobile.

This is contrary to initial expectations that the manufacture of the batteries could negate the advantages of the electrical drive.

Battery powered electric powered cars are usually promoted as the ideal solution towards challenges of future mobility, since they produce no exhaust gases in operation.

Li-ion batteries have established themselves over competing lead-acid and nickel metal-hydride (NiMH) kinds due to the fact they're lighter and can store a lot more energy.

Li-ion batteries are also basically maintenance-free, display no memory effect (loss of capacity when repeatedly charged after partial discharge), have a low self-discharge rate and are regarded as safe and long-lived.

Researchers at Empa's "Technology and Society Laboratory" decided to discover out if they are also environmentally friendly for sure.

They calculated the ecological footprints of electrical cars fitted with Li-ion batteries, taking into account all possible relevant factors, from those associated with the production of individual parts all the way through to the scrapping of the car as well as the disposal in the remains, including the operation in the car through its lifetime.

The analyze 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 might be ascribed on the battery (including its manufacture, maintenance and disposal). Half of this figure, that is about 7.5 per cent in the total environmental burden, occurs in the course of the refining and manufacture of the battery's raw materials, copper and aluminium.

The production from the lithium, in the other hand, is responsible for only 2.3 per cent with the total.

"Lithium-ion rechargeable batteries aren't as poor as previously assumed," said Dominic Notter, coauthor of the study.

The Empa team concluded that a petrol-engined automobile should consume between three and four litres per 100 kilometers (or about 70 mpg) in order to be as environmentally friendly as the e-car studied, powered with Li-ion batteries and charged with a typical European electricity mix.

The study has just been published in the scientific journal "Environmental Science and Technology".

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