There are discrete amounts of energy, *independent of time*. i.e. independent of power. Examples:
1. Work required to lift a mass m, a height h, in a gravitational field g, where g can be g(h) W = m g h (symbols in italics) 2. Energy of a photon; E = h f (f = nu) 3. Kinetic energy of a moving object at constant speed; KE = 1/2 m v^2 etc. etc. ---- Original message ---- >Date: Mon, 7 Jun 2010 03:35:43 -0700 (PDT) >From: "John M. Steele" <[email protected]> >Subject: [USMA:47532] Re: One unit only >To: "U.S. Metric Association" <[email protected]> > > Well, they are different, but "distinct and > separate" might be an overstatement. Formally, > energy is the integral of power with respect to > time, power is the derivative of energy with respect > to time, mathematically. It is not possible to talk > about the energy used by a nation because it keeps > using more, you can only talk about the energy used > over some period of time such as a year. > Energy/time is power, whether you express it as > watts or joules per year. Joules per year suffers > from the same issue as the kilowatt-hour. By > introducing a non-SI unit of time, the coherence of > the SI is lost. Also the term year lacks precision, > common, leap, Julian, Gregorian, etc.? Of course, > these energy per annum figures are estimates > compiled by summing numerous sources and making > estimates for any missing data. They probably do > not have the precision for the issue of "which year" > to matter. Do we see a curious spike every 4 years? > > As an engineer, the only misgiving that I have using > watts in this sense is that it is only a measure of > the annual average power. The times and magnitudes > of peak power, and also the base power requirements > (the valleys) are important. Using watts in this > average sense is technically correct, but it may > create a false expectation that only this amount > needs to be available on an instantaneous basis; > that expectation is wrong. If the use of exajoules > per annum helps legislators avoid that > misunderstanding, I, as an engineer, am quite > capable of dividing by 31.5 Ms. > > ------------------------------------------------ > > From: Pat Naughtin > <[email protected]> > To: U.S. Metric Association <[email protected]> > Cc: U.S. Metric Association <[email protected]>; > gmail aaj <[email protected]> > Sent: Mon, June 7, 2010 12:36:46 AM > Subject: [USMA:47525] Re: One unit only > Dear Stan, > It seems really odd to me that engineers, who > probably know much better, are using a power unit > when they are referring to energy. > As far as I know power and energy were clearly > distinguished as two quite separate and distinct > physical realities late in the 1700s or early in the > 1800s (I would like to have an exact date but this > is the best I can do at present). > As you know the unit for energy in the International > System of Units (SI) is the joule (symbol J) and the > unit for power in SI is the watt (symbol W). It > makes no sense at all to me to pretend you are > talking about energy when you are trying to describe > it with the SI unit for power. > You will recall that I am really concerned about > this issue because until journalists and politicians > are able to comprehend the nature of energy and how > to measure it, we have no chance that they might > begin to comprehend issues such as 'global warming', > 'climate change', or 'the end of oil' as these are, > in essence energy issues, and not power issues. > My approach is to use the SI unit, joule, only, and > to use it with an appropriate prefix to give whole > number amounts. See the short article at > http://www.metricationmatters.com/docs/AWordAboutGlobalWarming.pdf > for an example of how I use the energy unit, joule. > Cheers, > > Pat Naughtin > On 2010/06/07, at 10:17 , Stanislav Jakuba wrote: > > I am attaching an energy article that is > distinguished for using only one unit, the watt > (W), throughout. That units was selected as it is > both familiar everywhere, incl. in the US, and > shorter than others that one could select to > express the average energy usage. The watt (as > GW) is the only unit need for these kinds of > global statistics, and using it exclusively > enables immediate comparisons. > > > > I do not mean to start a debate about the opinions > expressed in the treatise, although I will > certainly read all. Instead, I do hope to > "persuade" everybody in the energy business to > settle on this unit for any kind of energy usage, > i.e.power, anywhere in the world instead of > the plethora of units common in energy related > statistics. On the scale of countries, only one > prefix also, the G, suffices. > > > > Stan Jakuba > > > > <Pacific Gas & E.3USMA.doc> > > > 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/ to > subscribe.
