27 October, 2011

Am I saving the planet? - Day 344

Odo 2230

Ok, so I enjoy the Zero DS. There's no doubt about that and I'd ride it even if it was powered by ground up baby seals it's so much fun. But. Am I “saving the planet”? I don't know, even as I begin this post where that question will lead me, so follow me down the rabbit hole and we'll find out together.

So, I only live a short distance from work. I could walk, but it's a longish walk. I could ride a bicycle and in my younger days that's exactly how I got around, averaging 300 km a week on the bike. I had no thought of saving the world, I just enjoyed it. So I sort of know what's involved.

It's 5 km for me to get to work. If I rode a bicycle I'd shower at work. I know I would because that's what I used to do when I rode all the time. I'm slow in the shower, always have been. 10 minute shower is quick for me. That's 100 litres of water and approximately 2 kWh to heat the water. I'd also have a shower when I got home but I do that anyway regardless, so we can ignore that. A bicycle lasts me about 5 years. The embodied energy in a bike is about 1000 kWh. (more for all alloy bikes, slightly less for steel). I work about 200 days a year. So that's 1 kWh for the bike and 2 kWh for the shower every day. 3 kWh/d.  I'm ignoring the energy to make the food that I eat because I have to get that exercise somewhere and if it's not on the bike then I use the rowing machine or something.

The Zero would have an embodied energy of less than 8000 kWh (that's assuming that it's all made of virgin aluminium which it isn't but I'm ignoring the replacement battery at the 5 year mark). How long it will last is a mystery but say 10 years. That's 2000 trips to work. So that's 4 kWh/d in embodied energy. Plus the 1 kWh that it draws. 5 kWh/d for the Zero.

The car weighs near enough to 1.5 tonnes. Most of it is steel but some is aluminium. Say 1300 kg of steel and 200 kg of aluminium. Steel is about 10 kWh/kg and Aluminium is about 65 kWh/kg, so that's 26000 kWh per car. Now this one is a bit harder. Here in Oz a car is worth nothing when it hits 300 000 km or 20 years. In the UK (according to my Pommie used car dealer mate) a 10 year old car is worth nothing but mileage isn't all that important. So in 20 years I'm never going to make it to 300 000 km at 2000 km a year. So the car will time expire so to speak. That works out here in Oz at 6.5 kWh per trip. (at 4000 trips to work). In the UK it would mean 13 kWh per trip. It will also burn about 1 litre of fuel. Bit hard to say how much energy that represents because the oil companies are rather coy about how much electricity it takes to refine oil. Given the revolting stuff that crude oil is and the lovely clear pure liquid that petrol is, it's got to have a fair bit of processing. Paper which is just wood ground up with water and then rolled flat uses 7 kWh/kg. The lowest plastic is twice that. So conservatively 7 kWh/litre (a bit less than a kg so slightly more than paper and much less than plastic). Of course it has energy itself, 10 kWh/litre. So that's 17 kWh used for every round trip plus around 6.5 kWh embodied energy in the car. 23.5 kWh per trip for the car. Over 4 times more than the Zero!

Car 23
Zero 5
Bicycle 3
Walking <1 (but adds 2 hours to my commute...)

So it looks like I might be doing my bit. Would be better if I rode a bicycle or walked, but not a *lot* better.

Oh, and the next time someone tells you “the grid couldn't handle lots of electric cars” remember the electricity used to refine the oil was probably (the oil companies wont say exactly) 7 kWh/litre and that does 10 km. A leaf has a 35 kWh battery and will go at least 100 km on that. So the leaf uses half the *electricity* that a petrol car uses.


  1. Great post! Been missing your reports. I like that you've quantified all the energy here for the various commuting methods. This one is a keeper.

  2. You will love this paper...


  3. I did like that paper. It was quite old and while lithium came out the best by a good margin, it only assumed 500 cycles. Now 8 years later 3000-6000 cycles are common. Lithium would come out as the far far better choice.

    Of course as I said, I need to get the excercise anyway, so I run the stationary bike with the computer perched on the bars instead of riding to work. Mostly that's a safety decision. Few people have ever been run over on a stationary bike. If there were decent bike paths in this town I'd probably bicycle to work but despite this being a new town, with lots of green space, they've copied all the other towns and made it virtually impossible to ride a bike around here. Even new developments (2 years ago) make no provision for bicycle riding. Well not "linked up" provision. There are great marked "bike paths" beside parts of the road, that then suddenly stop and you're left with very narrow roads, high speeds over a crest and around a bend... There's the width of empty council land on each side to put a bike path, but they just haven't done it.