Energy Question

About how many kcal/km are used when cycling at an easy-to-moderate
pace, say 20 km/hr? I come up with about 10 kcal/km.

Robert

On Aug 15, 3:32*pm, wrote:
About how many kcal/km are used when cycling at an easy-to-moderate
pace, say 20 km/hr? I come up with about 10 kcal/km.

Robert

as you might be aware that has a lot to do with you level of fitness,
normal heart rate etc. but, that said, in my estimation, about 200
kcal per hour sounds reasonable.

wrote in message
...
About how many kcal/km are used when cycling at an easy-to-moderate
pace, say 20 km/hr? I come up with about 10 kcal/km.

Robert

Hi Robert,
This calculator:
http://bikecalculator.com/wattsMetric.html
arrives at 11 kcal/km for 70 Kg rider, 9 Kg bike, no grade, no wind.
Kerry

wrote:

About how many kcal/km are used when cycling at an easy-to-moderate
pace, say 20 km/hr? I come up with about 10 kcal/km.

as you might be aware that has a lot to do with you level of fitness,
normal heart rate etc. but, that said, in my estimation, about 200
kcal per hour sounds reasonable.

That sounds pretty high for 20 km/hr (about 12.5 mph)

Art Harris

On Aug 15, 3:54*pm, Art Harris wrote:
wrote:

About how many kcal/km are used when cycling at an easy-to-moderate
pace, say 20 km/hr? I come up with about 10 kcal/km.

as you might be aware that has a lot to do with you level of fitness,
normal heart rate etc. but, that said, in my estimation, about 200
kcal per hour sounds reasonable.

That sounds pretty high for 20 km/hr (about 12.5 mph)

Art Harris

you think so ? I get about 500-600kcal per hour when I do between
30-35kms; so, to me it sounds perfectly reasonable.

wrote in message
...
On Aug 15, 3:54 pm, Art Harris wrote:
wrote:

About how many kcal/km are used when cycling at an easy-to-moderate
pace, say 20 km/hr? I come up with about 10 kcal/km.

as you might be aware that has a lot to do with you level of fitness,
normal heart rate etc. but, that said, in my estimation, about 200
kcal per hour sounds reasonable.

That sounds pretty high for 20 km/hr (about 12.5 mph)

Art Harris

you think so ? I get about 500-600kcal per hour when I do between
30-35kms; so, to me it sounds perfectly reasonable.



Wiki indicates that a litre of petrol contains 8314 kcal.......so I'm
guessing this means that when on my bike I am getting 831 km/"litre" (which
seems pretty impressive) or about 69 tonne x km/litre ....... which still
isn't THAT bad.


(An interesting side-note is that it seems that I need about 30 times as
much "coolant" as fuel when riding.)
Hugh Fenton

"Hugh Fenton" wrote in message
...

wrote in message
...
On Aug 15, 3:54 pm, Art Harris wrote:
wrote:

About how many kcal/km are used when cycling at an easy-to-moderate
pace, say 20 km/hr? I come up with about 10 kcal/km.

as you might be aware that has a lot to do with you level of fitness,
normal heart rate etc. but, that said, in my estimation, about 200
kcal per hour sounds reasonable.

That sounds pretty high for 20 km/hr (about 12.5 mph)

Art Harris

you think so ? I get about 500-600kcal per hour when I do between
30-35kms; so, to me it sounds perfectly reasonable.



Wiki indicates that a litre of petrol contains 8314 kcal.......so I'm
guessing this means that when on my bike I am getting 831 km/"litre"
(which seems pretty impressive) or about 69 tonne x km/litre ....... which
still isn't THAT bad.


(An interesting side-note is that it seems that I need about 30 times as
much "coolant" as fuel when riding.)
Hugh Fenton

Ooops.....Please change "tonne x km/litre" to km/litre per tonne.......

On 2008-08-16, Hugh Fenton wrote:

wrote in message
...
On Aug 15, 3:54 pm, Art Harris wrote:
wrote:

About how many kcal/km are used when cycling at an easy-to-moderate
pace, say 20 km/hr? I come up with about 10 kcal/km.

as you might be aware that has a lot to do with you level of fitness,
normal heart rate etc. but, that said, in my estimation, about 200
kcal per hour sounds reasonable.

That sounds pretty high for 20 km/hr (about 12.5 mph)

Art Harris

you think so ? I get about 500-600kcal per hour when I do between
30-35kms; so, to me it sounds perfectly reasonable.


Wiki indicates that a litre of petrol contains 8314 kcal.......so I'm
guessing this means that when on my bike I am getting 831 km/"litre" (which
seems pretty impressive) or about 69 tonne x km/litre ....... which still
isn't THAT bad.

But only because you have such a low power output. A modern IC engine is
somewhat more efficient than the human body. It's just a car operates at
about 50kW or so, compared to about 0.15kW for a person on a bike.

The main reason for the difference is that cars are very heavy and,
relatively speaking, very fast.

On Aug 16, 1:51 am, Ben C wrote:
On 2008-08-16, Hugh Fenton wrote:





wrote in message
...
On Aug 15, 3:54 pm, Art Harris wrote:
wrote:

About how many kcal/km are used when cycling at an easy-to-moderate
pace, say 20 km/hr? I come up with about 10 kcal/km.

as you might be aware that has a lot to do with you level of fitness,
normal heart rate etc. but, that said, in my estimation, about 200
kcal per hour sounds reasonable.

That sounds pretty high for 20 km/hr (about 12.5 mph)

Art Harris

you think so ? I get about 500-600kcal per hour when I do between
30-35kms; so, to me it sounds perfectly reasonable.

Wiki indicates that a litre of petrol contains 8314 kcal.......so I'm
guessing this means that when on my bike I am getting 831 km/"litre" (which
seems pretty impressive) or about 69 tonne x km/litre ....... which still
isn't THAT bad.

But only because you have such a low power output. A modern IC engine is
somewhat more efficient than the human body. It's just a car operates at
about 50kW or so, compared to about 0.15kW for a person on a bike.

The main reason for the difference is that cars are very heavy and,
relatively speaking, very fast.

Interesting. I appreciate the responses.

By 'efficient' here you mean percentage of energy input transferred to
work?

When it comes to moving a human the bicycle can't be beat though, it
seems, in terms of energy used per unit distance. Even if you pack a
car with people it still uses vastly more kcal per person per mile,
right?

On 2008-08-16, wrote:
On Aug 16, 1:51 am, Ben C wrote:
On 2008-08-16, Hugh Fenton wrote:
[...]
Wiki indicates that a litre of petrol contains 8314 kcal.......so I'm
guessing this means that when on my bike I am getting 831 km/"litre" (which
seems pretty impressive) or about 69 tonne x km/litre ....... which still
isn't THAT bad.

But only because you have such a low power output. A modern IC engine is
somewhat more efficient than the human body. It's just a car operates at
about 50kW or so, compared to about 0.15kW for a person on a bike.

The main reason for the difference is that cars are very heavy and,
relatively speaking, very fast.

Interesting. I appreciate the responses.

By 'efficient' here you mean percentage of energy input transferred to
work?

Yes.

When it comes to moving a human the bicycle can't be beat though, it
seems, in terms of energy used per unit distance. Even if you pack a
car with people it still uses vastly more kcal per person per mile,
right?

Yes. But a bicycle with a 150W electric motor would probably use less
kcal per person per mile than if you rode the bike.

An electric motor is not quite a fair comparison though, because its
energy store (the battery) contains ordered energy.

The battery was (typically) charged up by a heat engine converting
unordered energy (e.g. coal or oil) into ordered energy at about 40%
efficiency. But even if you include that, an electric bike may still be
a bit more efficient than the human rider.

If you could power a bicycle with an IC engine at only 150W you might
expect better kcal per person per mile than a human rider. But it's
difficult to make efficient IC engines that small. I think the main
problem is the most efficient size of cylinder is about half a litre or
so. A 500cc single cylinder engine will give you much more than 150W. To
make a low power ICE you need some kind of a "pulse and glide" system.

Still you could perfectly well make small one or two seater commuter
cars weighing about 30kg that got at least a few hundred miles to the
gallon going at about 20mph. It's just not the way history went since
fuel is fairly cheap.