I have some questions about fuel efficiency and units!

[uppi]

What kinds of things have energy that we can't digest that other things can? For example I imagine that if I ate some jellied gasoline then I wouldn't get any energy from it, but an airplane might be able to. What about the stuff that cows digest that we can't digest? Is there a lot of this stuff in food? Does lettuce actually have a lot of energy but we can't digest it to get at it? I mean bunnies would starve if it didn't, right?

Cellulose is the main thing that we cannot digest that other animals can. The cell wall of plants is made of cellulose and about 50% of a plant can be cellulose. So lettuce contains indeed much energy that is wasted when we eat it, while cows and bunnies can digest and use it.

 

[Mise]

If we can calculate efficiency in a percentage at all, as a measured output divided by some sort of input, which apparently we can, I don't see why it should be something like an engine on its own when such a figure is meaningless without also knowing the build quality of drive shafts, tyres and so on which also transfer the energy into movements.
Furthermore, for a car we have a lot of 'wasted' energy that transports the extra mass of the car

So how do you calculate the output? What equations of motion do you need to use?

I would use W=F*d, but I don't know what the force is in this case. You'd need to know the amount of friction that produces motion vs the friction that produces heat, wears the tyres, scatters pebbles, damages the tarmac, etc etc.

 

[lovett]

To travel 2 miles, you'd need half a cheeseburger, whereas your car, apparently, requires 40 cheeseburgers (according to Zelig). That means that you need one eightieth of your car's fuel allowance.

To add, this doesn't necessarily mean your more efficient then your car. Taking the energy costs of the entire system into account, driving might well be better then walking. Mainly because cheeseburgers take relatively huge inputs of energy to make, as opposed to petrol. From an enviromental perspective, certainly it would be better to drive rather then walk on cheeseburger derived energy. Assuming these cheesburgers also have beef in, they're pretty inefficient. Producing a Kg of beef produces the equivalent CO2 emmissions of driving an average car 250KM (36.4Kg)and burns enough energy to light a 100-watt bulb for nearly 20 days (169MJ). So if your an enviromentally conscious beef eater, it might be better to drive rather then walk. Funny, huh?

 

[Brighteye]

But how much carbon do we emit in moving the petrol to the station and carting it around in the car before it gets used?

 

[History_Buff]

But how much carbon do we emit in moving the petrol to the station and carting it around in the car before it gets used?

An enourmous amount. Most of it is distributed by truck at the local level. Even when you're using pipelines, a large amount of energy is spent heating and pumping it.

That's why electric cars, even if we kept burning oil to fuel the power stations, would save a lot of CO2 emissions.

 

[ainwood]

An enourmous amount. Most of it is distributed by truck at the local level. Even when you're using pipelines, a large amount of energy is spent heating and pumping it.

Define "enormous"?

Trucking a fuel uses no more energy that trucking anything else of the same mass.

 

[History_Buff]

Of course not, but it's still fuel spent moving other fuel around.

Contrast it with a society that used primarily electric vehicles. Losses for transmitting power over long distances will obviously be much less than the energy we expend now delivering gasoline.

Unfortunately, I don't really know where I would go about getting information about the fuel distribution networks in NA, so it would be rather difficult to come up with a general figure.

 

[ainwood]

Contrast it with a society that used primarily electric vehicles. Losses for transmitting power over long distances will obviously be much less than the energy we expend now delivering gasoline.

Would they? Is it that obvious?

There are significant energy losses in electricity distribution, and they are proportional to transmission - ie: a move to a fully electric fleet would increase demand & hence line losses.

 

[History_Buff]

Would they? Is it that obvious?

There are significant energy losses in electricity distribution, and they are proportional to transmission - ie: a move to a fully electric fleet would increase demand & hence line losses.

I definitely think it is. I'll try and dig up some actual numbers as to transmission efficiency in the morning.

If increased demand arises for power transmission as it surely would, you can just lay down more, wider wire on the same poles and reduce losses, for a one time cost and power outlay.

Not to mention that we're much closer to superconducting transmissions lines than we are to scrubbers on consumer vehicles.

 

[El_Machinae]

It would also continue to encourage local electricity development. Solar (e.g.,) would become more viable with increased electricity demand.

Though with e-cars, they've been saying "you can plug them in at night, when electricity is cheapest!", but moving more to solar (since it scale nicely) and e-cars means that nighttime electricity might become the more expensive type.

 

[Narz]

Just wanted to throw out there that bicycling is something like 10x more efficient calorie-wise than walking. Also, it's important to remember (if you're thinking ecologically and not just economically) that the production & transportation of food itself has widely varying efficiency. For example, 200 Calories strawberries grow in Massachusetts would be more energy efficient (since you're in New England already = less shipping) the California strawberries (let alone New Zealand apples) and vastly more efficient than 200 Calories of beef raised in former rainforests in South America, shipped to a factory farm in Iowa to be fattened up (and fed tons of grains & soybeans grow in Illinois, Indiana & Brazil).

 

[Narz]

Though with e-cars, they've been saying "you can plug them in at night, when electricity is cheapest!", but moving more to solar (since it scale nicely) and e-cars means that nighttime electricity might become the more expensive type.

Slow down there George Jetson. We're not going to have to "worry" about nighttime electricity might becoming the more expensive type for a long, long time. Probably forever. Likely "e-cars" will be too little too late also.

 

[El_Machinae]

Shouldn't I be able to purchase an e-car next year?

 

[Narz]

If you're rich enough you could purchase one right now. If you're clever & resourceful enough you can make you own. But most of your 300 million fellow citizens (assuming you're American, I forgot if you are ) are neither rich nor clever enough & the inevitable severe recession from a debt based contacting economy won't help matters (well hopefully it will help in the cleverness factor a bit).

 

[ainwood]

Also, it's important to remember (if you're thinking ecologically and not just economically) that the production & transportation of food itself has widely varying efficiency. For example, 200 Calories strawberries grow in Massachusetts would be more energy efficient (since you're in New England already = less shipping) the California strawberries (let alone New Zealand apples) and vastly more efficient than 200 Calories of beef raised in former rainforests in South America, shipped to a factory farm in Iowa to be fattened up (and fed tons of grains & soybeans grow in Illinois, Indiana & Brazil).

Yes, but you also need to consider the environmental impact of actually growing the fruit & meat.

Beef raised in New Zealand spends 365 days a year outdoors. They are fed grass, or maybe hay. Very rarely are they fed grain.

Beef raised in parts of the US often spends winters inside, and is usually fed grain over the winter months. Take into account that costs of heating & grain to feed them, and this easily outweighs any transport costs.

Ditto for strawberries - New Zealand strawberries are not grown in hothouses.

 

[Narz]

Thanks ain. It's good to know NZ has more sustainable agricultural practices than the United States. Bodes well for their future.

BTW, your PM box is full.

 

[ainwood]

Thanks ain. It's good to know NZ has more sustainable agricultural practices than the United States. Bodes well for their future.

Yeah - the EU (protectionist as it is) was hyping "food miles" to get people to buy local and save the environment. Research was done to check, and it was shown that the environmental impact of growing meat in NZ and shipping it (refrigerated) half-way around the world to a UK supermarket was less than growing it in the UK, when you took into account the agricultural practices.

BTW, your PM box is full.

Yeah - cleared some space now!

 

[El_Machinae]

Well, avoiding meat really is a big key to most of the world's crises. It's hard to compare 'meat to meat' since the meat is so bad in general.