Fri 18 Mar 2011
There is a common misconception that electric vehicles are carbon-neutral and that their impact on the environment is as non-offensive as the quiet sound of their humming engines.
But electricity doesn’t come from nowhere. To have a live outlet, tons of dirty coal (or sometimes natural gas or uranium) must be consumed at a power plant, generating electricity which then must be stored and transported to a building or charging station. This process is in and of itself a carbon intensive one. In the United States and China, the vast majority of the nation’s electricity is generated by coal, which, according to the Intergovernmental Panel on Climate Change, has a much higher global warming potential than conventional vehicle fuels like diesel or gasoline.
So when we promote electric cars are we just shifting the emissions from the tail pipe to the power plant?
In the last three months, I have worked with my colleagues in China at the Innovation Center for Energy and Transportation on a report commissioned by the United Nations on the life-cycle carbon impact of electric vehicles.
What we found may surprise many.
We found that pure battery electric vehicles may not always improve environmental impact of transport as much as we would like to expect; in fact, in some regions, electric vehicles are not an environmentally friendlier technology, particularly in terms of GHG emissions, because of the source of electricity which powers them.
Except for one region in China, compared with conventional vehicles, electric vehicles do not significantly reduce emissions – from a lifecycle point of view. After all, electric vehicles are an energy conversion and not a clean energy technology.
In order to generate data that reflects the lifecycle GHG emissions we look at the environmental impacts of a sequence of events in the fuel or battery’s life. For electric vehicles, we look at the emissions associated with the entire life of the battery from the mining of raw materials such as lithium, to the transportation and storage of energy to the disposal of waste material associated with the battery pack. This is what we call “Mine-to-Pack” emissions. For a conventional vehicle, we measure the emissions generated during the fuel’s life cycle, from the oil well to the tank, or “Well-to-Tank” emissions.
This analysis points to a clear implication for policy: Electric grids must be made more efficient or be more reliant on renewable sources of energy such as wind and solar. This means replacing coal plants with renewable energy on a large scale, producing what many call a “smart grid.” If renewables aren’t commercially viable, then we need to install new technology to burn coal more cleanly or capture the emissions that come from coal. In the US and China (the world’s biggest coal-consuming countries) these are existing areas for government-led research and development. But there is still a long way to go before so-called clean coal or renewable energy can be economically feasible in order to remake the electricity grids in either country to something we can call “smart.” Our report for the UN adds evidence to an existing pile that electricity grid reform should be priorities for both Washington and Beijing.