[Zizandi Dickens]

Zizandi Dickens  asked the Naked Scientists:
   
Hi,

I want to know how ecologically friendly hybrid cars actually are. I know that there have been recent tests that show that (at worst) some of the manufacturers have under estimated carbon emissions from these cars by as much as 56%, but my question is not so much about emissions from the cars themselves.  Â 

I want to know whether the fact that they use electricity actually makes them more 'green'?  Â 

Energy usage is the largest sector in terms of emissions (looking at statistics from the UN). Road usage accounts for approximately 9% of total emissions and electricity and heat for about 24% (these figures are probably also contestable, but roughly speaking).

Coal burning power plants are responsible for most of these energy emissions and most countries rely on coal-fired plants for much of their electricity generation. So do hybrid cars emit sufficiently less CO2 to offset this?

Also, in a country like mine (South Africa) - and we are not alone - electricity production is over subscribed and under resourced, but this issue is probably not strictly scientific!
   
Thanks,

Zizandi Dickens

What do you think?

[Karsten]

It depends on where you live. Where I live all electricity is hydro power. There may be some nuclear power mixed in, but I think not. Where I go to work, electricity is made by a mix of hydro power from two locations,  one wood chip power plant, some nuclear, and 1% from an oil power plant in a neighboring state. So, in my case it is almost carbon neutral.

In other places it is not.

There are additional issues with electric cars, such as the batteries and the problems with their production and disposal. Of course it would go a long way if Americans could be content with small cars and short trips. That will be a while. We have been told for decades that bigger is better and that living in the country rules. Once we get over that, we may see more electric cars in more places.

And in some situations, electric cars make sense just to battle smog. The pollution still occurs somewhere else, but at least it is somewhere else. The problem is not gone, just relocated.

Of course one might argue that even hydro, wind, or nuclear power plants are not carbon neutral since they require fossil fuels for construction and maintenance.

[LeeE]

For fossil fuels, in a word, No.  For every additional stage between burning the fossil fuel and using the resultant energy there will be losses, reducing the overall efficiency, which is what it's really all about.

Electric cars still need fuel to be burnt, so the most efficient way of doing it is to burn the fuel in the car (as long as the efficiency of burning the fuel in the car is as good as burning it in a power station) to avoid the transmission losses.

A better alternative to stored-charge electric vehicles are hydrogen fuel-cell systems, where the (hydrogen) fuel is 'burnt' (oxydised) in the vehicle to generate electricity, to drive the car.  The main problem with hydrogen fuel-cell systems is that the pressures required, to store a usable amount of H, are incredibly high, yet the fuel-cell must also be pretty robust to withstand road accidents.

Ultimately, safety is a major issue and believe it or not, petrol (gasoline) is relatively safe when compared with batteries or fuel cells.  If a petrol (gas) tank gets punctured it will leak, and the spilled fuel will readily ignite, but it won't explode unless the fuel is mixed with the air to the correct proportions.  A shorted battery or highly pressurised fuel cell leak is a rather different kettle of fish though.

[Geezer]

Zizandi Dickens  asked the Naked Scientists:
   
Also, in a country like mine (South Africa) - and we are not alone - electricity production is over subscribed and under resourced, but this issue is probably not strictly scientific!
   

That could be a very significant factor. Electricity generation and transmission infrastructure expansion consumes a lot of resources. A major wind farm project was recently cancelled in Texas because the existing transmission infrastructure could not deliver the electricity to the market.

Fuel cells would be great, but I've given up waiting. They were supposed to be "just around the corner" in the early 1960's. A technology that can't be made practical in fifty years is probably not practical. Perhaps there will be a breakthrough, but I'm not holding my breath.

Hybrid cars are quite good because they do recover energy that would otherwise be wasted as heat. Electric cars (like the Volt) are really just another form of hybrid. "All electric" cars (those without an onboard IC generator) might work for a few people, but they won't work for most people because of the current (ha ha) state of battery technology.

IC engines are not going away any time soon. But we can do things to make them more efficient, and we don't have to burn fossil fuel in them either. If the fuel was made without the consumption of fossil fuels, it is not adding to the net CO2 in the atmosphere. That would be a huge improvement. However, we also have to balance that against availability of food. We should focus our efforts on producing synthetic fuels in locations that are not viable for farming.

[teragram]

This site has some interesting information, although many might say that "they would say that anyway". I think that Tesla have overstated their case by quoting the source of electricity as Combined Cycle Gas Turbine plants. I understand that these are by far the most efficient forms of fossil fuel powered generators. Coal fired etc. power sources give a less favourable result. Having said that however, the human race has to move away from using high carbon sources of energy. When we finally achieve this, then the battery or capacitor powered car will be the bee's knees from the pollution point of view.The report seems suggest that hydrogen powered cars (even fuel cell) will not lead to a great improvement efficiency wise. 
http://www.veva.bc.ca/wtw/Tesla_20060719.pdf

[Don_1]

They'd be quite friendly if not for the fact that they have to be manufactured, which can account for 50% of a car's polluting contribution over its lifetime (for petrol powered cars) and if they did not need charging with fossil fuel generated electricity.