Dear Pat:
It saddens me that you had not disagreed with my "long standing recommendation"
when I reasoned about it. Both me and James Watt (it he were alive) are
unhappy. Perhaps if you re-read that reasoning again, it might help you see why
James coined the power for comparisons. In case you deleted that e-mail
already, I re-coup: All energy-generation-stations and most
energy-using-devices (appliances) are rated in power units. Someone
recalculates it to energy consuMED in a day or year or so. Have you ever bought
a lightbulb rated in energy consuMED by a household, or per minute, or hour,
day, year, or its useful life? I have not. Well, all this was written about
before.
I cannot be wrong with the statement "Energy consumption is power" as it is not
my sentence. The author of that statement consistently uses it to mean power
and I only explained "how come." I also said that I wished he would have used a
more explicit phrase. But from the context of his writing, and the unit kWh per
day, it is, nevertheless, clearly power.
Cheers,
Stan Jakuba
----- Original Message -----
From: Pat Naughtin
To: U.S. Metric Association
Sent: 09 May 28, Thursday 03:12
Subject: [USMA:45115] Re: Power or Energy?
Dear Stan,
As I disagree with your fundamental point when you say: 'my long-standing
recommendation for using power for the energy related comparisons' I will
outline the reasons for my disagreement by interspersing some remarks in red.
On 2009/05/28, at 9:36 AM, Stan Jakuba wrote:
Thanks for writing Pat. I appreciate your sharing the impression of
MacKay's book and agree, with you except where I think MacKay has a point in
claiming that:
Energy consumption is power.
Energy production is power.
No, you are wrong here unless you add in some time factor such as 'per
second'.
To use another analogy, where you would you say:
Car distance is speed
I would say car distance is car distance as no time unit has been mentioned
or implied.
That is correct. This is why:
Energy, as the AMOUNT of it, is energy producED and it is indeed in J.
Agreed.
But energy producTION is power because it implies a continuous process that
involves time. In other words, energy produCED in 2007 is in joules but the
energy producTION in 2007 is in watts.
Let's use solar energy as an example. The solar energy collector collects as
much sunlight as it can and converts a fraction of this energy into electrical
energy. It does this whether it is cloudy or bright. At the end of the day, we
can assess how much energy has been converted from light energy to electrical
energy but, at no time did the solar panel need to be described as having a
nominal power rating. As the conditions vary continuously so does the power
rating second by second. That said, however, it is in the interests of the
solar energy panel supply company to specify their product according to the
maximum amount of energy that the panel can produce under ideal conditions
(very probably in an enclosed laboratory using artificial light).
Similarly, others who are selling coal fired or nuclear energy converters
tend to apply these idealised power ratings to their products yet fail to
mention that there is down time for cleaning and maintenance, variations in
fuel qualities, etc.
In short when it comes to power ratings on energy conversion plants, what you
see is not what you get. A better more truthful way would be to specify the
likely amount of energy you will be able to deliver for sale to the real world.
The specification of the design capacity of an energy converter is quite
irrelevant when it comes to selling the energy. It is always sold in energy
units (sadly not usually the joule) and not power units.
You cannot but a watt of power anywhere in the world — the concept of
producing power or selling power is just not possible.
In yet another words, 100 EJ and 3200 GW both represent energy usage in
the U.S. The 100 EJ is the energy consumed in the U.S. in 2007, the 3200 GW is
the (average) energy consumption in the U.S.in 2007. The wording of the leading
sentence determines if J or W is appropriate.
Surely it is much easier to decide if you are talking about energy or power
and then use the appropriate SI unit — joule for energy and watt for power. Any
other approach leads to a muddle. And this is not an academic debate type
muddle. This is a muddle that prevents our politicians understanding a single
word about climate change — for example.
Now there are two points here:
It is better to write: The (average) power consumption thru 2007 was 3200
GW. I would word it that way, but the esteemed Prof. is not wrong saying it his
way. Obviously, his way may cause confusion. And his kWh per day is silly as a
base for comparison and the reasoning for it is medieval.
To understand your sentence, The (average) power consumption thru 2007 was
3200 GW. is quite complex. I have to know what you might mean by (average)
before I can even begin to think about how much energy might have been used. To
find the energy used, and paid for, do I simply multiply 3200 by the number of
days in a year and then by the number of seconds in a day?
The second point brings forth what I wrote earlier: Most of the climate and
energy debates are about POWER because they deal with the amount of some kind
of energy PER year, per day, per hour, etc. For conversions between the two
common ways to express power consider that
1 GJ/y = 31.7 MW and 1 W = 31.5 MJ/y. His silly 1 kWh per day = 42 W
Most of the climate and energy discussions revert to power discussions
because the word, power, is itself totally corrupted by sales people (as
mentioned earlier) and by linguists. Consider these common words and phrases:
Power station
This does not exist as power cannot be produced. Energy can be converted at a
particular rate but power is not produced for sale.
Power outage
Not possible. The supply of electrical energy might cease for some reason but
no power was supplied in the first place.
Power bill
Ridiculous, how do you charge for something that cannot be supplied.
I will not list all the many other misuses of the word, power, there are too
many.
In summary, the Prof. adheres to my long-standing recommendation for using
power for the energy related comparisons but he should have worded his
sentences better and stick with W. The joule per time times time is ..... (I
don't want to repeat myself).
The best approach in my view is to compare amounts of energy in joules with
other amounts of energy in joules. All else is completely unnecessary
obfuscation.
Look again at how I compared the energy consumpTION of the years 1997 and
2007 in the U.S. in the tables on the last page of the attachment
Ar-Energy-full.doc sent a few weeks ago.
Stan Jakuba
Your tables worked only because you had gone to the trouble of comparing
average production for a year in the same unit, gigawatt (GW) but your heading
for these tables, U.S. Energy Consumption, is quite inaccurate as from the
title we could reasonably expect the data to be presented in energy units. To
my mind, these tables should have told us how much energy was used in these two
years and not some construction about average power ratings that I have to
deconstruct to find your meaning.
I think the rule is called 'Occam's Razor' where given two choices between
ways to analyse or to present scientific findings, it is always best to choose
the simplest of the two.
Cheers,
Pat Naughtin
Author of the forthcoming book, Metrication Leaders Guide.
PO Box 305 Belmont 3216,
Geelong, Australia
Phone: 61 3 5241 2008
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