My bicycle expends an average of 20 kJ/km
or
0.02 J/m (best for comparison with cars)
or
(Help me here) 20 mJ/m (yes miliJoules)
My battery is a 20 A*h 36 volt battery (LiFeO2).
Pat Naughtin wrote:
On 2009/09/19, at 08:36 , lps wrote:
You can use J/m with electric cars too. I use the figure with my
electric bicycle. I convert w*h/ km to J/km. You can convert that to
J/m if desired.
Dear Linus,
Thanks for your email. I would like to make two points:
1 Could you share with us some of your data in joules per metre for
your electric bicycle so that we can make comparisons with other
vehicles. Where does your electric bicycle fit on this scale?
Car 3 200 J/m
Boeing 747 5 440 J/m
School bus 13 510 J/m
Truck 15 440 J/m
2 I think that it is preferred practice in SI to have the denominator
in a unit without a prefix and to apply any prefix to the numerator.
In this case, kilojoule per metre (kJ/m) would be preferred to joules
per kilometre (J/km). However, that said, I believe that the simplest
SI unit applied with whole numbers is the best possible solution.
Cheers,
Pat Naughtin
Author of the ebook, /Metrication Leaders Guide,/ that you can obtain
from http://metricationmatters.com/MetricationLeadersGuideInfo.html
PO Box 305 Belmont 3216,
Geelong, Australia
Phone: 61 3 5241 2008
Metric system consultant, writer, and speaker, Pat Naughtin, has
helped thousands of people and hundreds of companies upgrade to the
modern metric system smoothly, quickly, and so economically that they
now save thousands each year when buying, processing, or selling for
their businesses. Pat provides services and resources for many
different trades, crafts, and professions for commercial, industrial
and government metrication leaders in Asia, Europe, and in the USA.
Pat's clients include the Australian Government, Google, NASA, NIST,
and the metric associations of Canada, the UK, and the USA.
See http://www.metricationmatters.com
<http://www.metricationmatters.com/>for more metrication information,
contact Pat at [email protected]
<mailto:[email protected]> or to get the free
'/Metrication matters/' newsletter go
to: http://www.metricationmatters.com/newsletter to subscribe.
Pat Naughtin wrote:
Dear All,
I have just read the article at
http://www.metrication.us/content/demise-mpg where I was struck by
the first paragraph.
/Even before the advent of partially- or fully-electric cars, it was
becoming increasingly apparent that the old fuel economy metric of
miles per gallon isn't as useful for measuring energy consumption in
vehicles as when it was first codified in the original Corporate
Average Fuel Economy standard in the 1970s. That is due in part to
the proliferation of new fuels--E85, LPG, LNG, CNG, methanol, and
hydrogen--but also because expressing the relationship between
distance and volume in this way obscured the diminishing returns to
higher levels of fuel economy. As a Wall St. Journal column earlier
this week put it, adding electricity into the mpg mix, "risks giving
consumers inaccurate information about the financial and
environmental costs of driving." But if we need a new metric, what
should it measure?/
I think that the time is rapidly approaching for energy to be
measured in the only SI energy unit – joule – and that old
pre-metric measuring words for fuel efficiency should be converted
to the only SI unit available for energy efficiency for road
transport – joules per metre.
As a starting reference, here are some examples:
*Average car*
32 megajoules per litre (32 MJ/L) for lead free car fuel, and
10 litres per 100 kilometres (10 L/100 km) fuel consumption, then
an average car consumes 3 200 joules of energy for each metre it
travels (3 200 J/m).
*Average truck*
38.6 megajoules per litre (38.6 MJ/L) for diesel fuel, and
40 litres per 100 kilometres (40 L/100 km) fuel consumption, then
an average truck consumes 15 440 joules of energy for each metre it
travels (15 440 J/m).
*Average (school) bus*
38.6 megajoules per litre (38.6 MJ/L) for diesel fuel, and
35 litres per 100 kilometres (35 L/100 km) fuel consumption, then
an average truck consumes 13 510 joules of energy for each metre it
travels (13 510 J/m).
*Average Boeing 747*
34 megajoules per litre (34 MJ/L) for diesel fuel, and
16 litres per 100 kilometres (16 L/100 km) fuel consumption, then
an average truck consumes 5 440 joules of energy for each metre it
travels (5 440 J/m).
*Summary*
Car 3 200 J/m
Boeing 747 5 440 J/m
School bus 13 510 J/m
Truck 15 440 J/m
As usual, I commend to you the simplicity of SI units and the ease
of understanding using whole numbers (see
http://www.metricationmatters.com/docs/WholeNumberRule.pdf ).
Sadly, I could not find comparative figures for electric cars – even
at http://www.optimalenergy.co.za/news/article.php?pk_news_id=112v
Cheers,
Pat Naughtin
Author of the ebook, /Metrication Leaders Guide,/ that you can
obtain from
http://metricationmatters.com/MetricationLeadersGuideInfo.html PO
Box 305 Belmont 3216,
Geelong, Australia
Phone: 61 3 5241 2008
Metric system consultant, writer, and speaker, Pat Naughtin, has
helped thousands of people and hundreds of companies upgrade to the
modern metric system smoothly, quickly, and so economically that
they now save thousands each year when buying, processing, or
selling for their businesses. Pat provides services and resources
for many different trades, crafts, and professions for commercial,
industrial and government metrication leaders in Asia, Europe, and
in the USA. Pat's clients include the Australian Government, Google,
NASA, NIST, and the metric associations of Canada, the UK, and the
USA. See http://www.metricationmatters.com
<http://www.metricationmatters.com/>for more metrication
information, contact Pat at [email protected]
<mailto:[email protected]> or to get the free
'/Metrication matters/' newsletter go to:
http://www.metricationmatters.com/newsletter to subscribe.
