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.
