John M. Steele
Tue, 10 Aug 2010 06:58:49 -0700
We are not ALWAYS talking about power. Pollution for light vehicles is regulated in grams per kilometer (or mile). For heavy truck, industrial engines, etc it is rated per unit of energy output. However, the units are commonly grams per kilowatt-hour. The kilowatt-hour is clearly a unit of energy, in fact, 3.6 MJ. I suppose one could instead express pollutant mass flow per unit of power, grams per second per kilowatt or megawatt. There is no doubt that statistics like annual energy use can also be expressed as average watts over the period. The discussion of average vs peak is so important, and so likely to be forgotten if those average watts are used, that I am not sure I agree it is "better." I agree with your technical assertion, but "better" involves whether all the necessary discussion takes place. I don't trust the renewables folks much either, but I feel letting them have their lack of understanding and probing separate for annual energy production and peak power (capacity) is "safer." But that's just me. I see either as a legitimate approach. Which is "better" is very subjective. ________________________________ From: Stanislav Jakuba <jakub...@gmail.com> To: jmsteele9...@sbcglobal.net Cc: U.S. Metric Association <usma@colostate.edu> Sent: Tue, August 10, 2010 9:38:07 AM Subject: Re: [USMA:48347] RE: Air-conditioning Concerning the joule and watt, in all these discussions, there is one recognition missing. As you perhaps noticed, my writing uses only W. Why? Because that is what we are talking about - power. It does not matter if we get it from joules, kWh, oil equivalent, cords of wood, TNT, .... you name it, because in all those discussions we are referring to the units of energy PER (some) TIME, be it year, day, fortnight, millisecond. Then the watt eliminates the need for ANY energy unit and ANY time unit by first converting all the energy units to joule and all the time units to second and (without telling anyone about the process) state the number in the united, accepted, agreed on watt. Why is it that everybody insist on using energy and time units when referring to power is beyond me (except when cheating about the usefulness of renewable energy devices). James must be turning in his grave. An interesting analogy where this failed: There were proposals for making a name for "distance per time", such as the benz. Unlike the analogous watt, the benz never materialized. The joule is useful for energy densities (J/kg, J/m³) and similar. But for energy per time, we all agreed the watt is better and made it the only unit a 1/2 a century ago. Isn't it time that at least USMA recognizes that? Stan Jakuba On Tue, Aug 10, 2010 at 7:21 AM, John M. Steele <jmsteele9...@sbcglobal.net> wrote: I agree, but the kilowatt hour looks hard to displace as the public is used to it in electricity. > >I don't agree that scientists avoid the use of the joule; it has to be used in >calculations to preserve the coherence of the SI. However, I think there is >avoidance of it in communicating to the public. That avoidance makes some >sense >in two areas: >*The kilowatt hour is well-established by more than a century of electricity >billing, the public has a reasonable grasp of it. >*In mechanical power (engines), machines are rated in kilowatts, and seconds >are >too short to keep track of. Many engines have hour meters to schedule >maintainance, and measurement of run time in hours relates more to how people >think about it. Presto, the kilowatt-hour is back. > >However, I get upset when I see the chemical energy of a fuel expressed in >kilowatt-hours. The Brits do this for natural gas. > >It fits nicely with all the other mongrel units: liter, metric ton, bar, >hectare, hour, minute, degrees, minutes and seconds of arc, nautical mile, all >of which must be avoided or converted in some calculations, but OK in others. >Only the first four have a "power of ten" relationship to "proper SI." (I >have >omitted a few I never use like Angstrom and barn.) > > > > ________________________________ From: Pat Naughtin <pat.naugh...@metricationmatters.com> > >To: U.S. Metric Association <usma@colostate.edu> >Sent: Tue, August 10, 2010 3:26:24 AM >Subject: [USMA:48346] RE: Air-conditioning > > >Dear Martin, John, Carleton, and Stan, > > >It seems to me that measuring, recording, and reporting energy in joules and >power in watts is the simplest way to go when we are discussing anything to do >with energy and/or power. > > >Of course you might use an appropriate prefix to provide most of the amounts >you >discuss are in whole numbers. You might choose kilojoules for food energy, >megajoules for small engines, and gigajoules, petajoules etc for larger >amounts. > > >I find it difficult to understand why many engineers and scientists seem to >avoid the word joule altogether preferring to use mongrel measures such as >kilowatt-hours instead of the SI unit, joule. > > >This is a worry as scientists try to communicate their ideas on such things as >climate change to journalists and politicians who often have no idea that >energy >and power are two totally different physical concepts/ > > >Cheers, > >Pat Naughtin >Author of the ebook, Metrication Leaders Guide, see >http://metricationmatters.com/MetricationLeadersGuideInfo.html >Hear Pat speak at: http://www.youtube.com/watch?v=_lshRAPvPZY >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. > > >On 2010/08/10, at 15:34 , Martin Vlietstra wrote: > >We are drifting into the “Green” argument here which is outside the remit of >this board. However noting that the best way to quantify “Green” arguments by >using a single, consistent unit of energy is well within the remit of this >board. >> >> ________________________________ >>From: owner-u...@colostate.edu [mailto:owner-u...@colostate.edu] on Behalf >>Of Carleton MacDonald >>Sent: 09 August 2010 23:10 >>To: U.S. Metric Association >>Subject: [USMA:48344] RE: Air-conditioning >> >>True. But nonetheless if all of that stuff in the house raises the internal >>temperature one degree Celsius, that’s one fewer degree the furnace has to >>work >>to get the house up to the setting on the thermostat (which in our house in >>the >>winter is 20 degrees Celsius). >> >>Carleton >> >>From: John M. Steele [mailto:jmsteele9...@sbcglobal.net] >>Sent: Monday, August 09, 2010 07:07 >>To: carlet...@comcast.net ; U.S. Metric Association >>Subject: Re: [USMA:48340] RE: Air-conditioning >> >>I agree with Martin's response, but the more immediate effect to you is that >>you >>are heating at electricity rates, which are normally much higher than natural >>gas or other heating fuel rates. >> >>Use the electricity you need to, but the waste heat is a cost-ineffective >>offset >>to heating fuel use in winter and pure waste in the summer. >> >> ________________________________ >>From: Carleton MacDonald <carlet...@comcast.net > >>To: U.S. Metric Association <usma@colostate.edu> >>Sent: Sun, August 8, 2010 9:23:19 PM >>Subject: [USMA:48340] RE: Air-conditioning >>On the other hand, in winter, wouldn’t all that heat mean the furnace has to >>run >>less often? >> >>Carleton >> >>From: owner-u...@colostate.edu [mailto:owner-u...@colostate.edu] on Behalf >>Of Stanislav Jakuba >>Sent: Sunday, August 08, 2010 15:34 >>To: U.S. Metric Association >>Subject: [USMA:48339] Air-conditioning >> >>Undoubtedly, the USA members on this forum noticed the flood of >>air-conditioning energy-consumption news. I responded to one of these. That >>Letter to Editor is below, and I am adding a paragraph beneath it for USMA >>that >>addresses SI units. >> >>Letter to Editor: >>The "How Air Conditioning Is Sapping Our Society" omitted one reason for the >>skyrocketing air-conditioning electricity consumption. It is not just the >>growing number of air-conditioned homes that contributes to the steep rise, >>it >>is also the higher electricity consumption in homes. And in commercial >>buildings >>for that matter. >> >>As everyone was taught in school, all electricity at home changes into heat. >>Thus the electricity consumed by each lightbulb, TV, stove, computer, >>freezer, >>down to the cell-phone charger, heats the building interior thereby raising >>the >>temperature if the walls are not "cooling" such as in hot weather. More then >>in >>the past, these electricity consuming devices are left on longer such as >>lights >>burning during daylight for decorative purposes, computers and TVs always on >>(and when off they still consume electricity unless unplugged), icemakers >>running at full tilt, dishwashers providing electrical drying, etc. In >>commercial buildings, there are more lights, more computers and devices on >>24/7. >>In supermarkets there are heat blasting bakeries, cooled food counters, >>drinking >>water and soda-fountains, freezers, etc. whose coolers are not vented >>outside. >>The heat the compressors in these devices generate must also be removed by >>the >>main air-conditioners in addition to their basic load of cooling people, >>walls and ceiling. It all adds. >> >>Air-conditioners use close to the same amount of electricity for the removal >>of >>heat as is consumed by the individual appliances. To illustrate, it takes >>between 50 W to 100 W by the air-conditioning compressor motor, fan and >>controls to remove the heat flow a 100 W lightbulb produces. Total power: up >>to >>200 W. Conversely, a simple turning off (better yet, unplugging) appliances >>in >>the hot, humid weather saves up to twice the amount of electricity they would >>consume. >> >>And it is not just air-conditioners that gobble electricity for cooling. Ice >>makers are another culprit. About 1 kg of ice is melted/made for every person >>in >>the US daily. If melted inside the home, some of the energy helps cooling >>the >>interior but most of the ice goes "down the drain" cooling the underground >>and >>picnic grounds. I calculated that 2.5 GW is utilized for ice making in the >>US . >>That is more than the capacity of the nuclear power plants in >>Connecticut combined. Or, to involve renewables, the power of some 12 500 >>typical wind mills. >> >>Lastly, the misuse of fans. Leaving a 500 W fan on in a closed room when >>nobody >>is there, as is often done in homes, schools, and businesses, is not cooling >>it. >>To the contrary, it is adding 500 W to the room thereby heating it. It is the >>evaporation from skin and convection that cools us; the wind only intensifies >>it. When there is an air-conditioner on concurrently with the fan and nothing >>to >>evaporate, another 500 W load is added to the compressor, a total of up to 1 >>kW >>more is spinning the meter. >> >>USMA members will appreciate this addition: >>Many writers of the air-conditioning, energy-consumption analyses illustrate >>the >>numbers on the example of the 100 W lightbulb as above. Then they take the >>Btu >>rating of an air-conditioner and thru convoluted conversions among various >>energy and power units provide a number in yet another unit. In the analyses, >>they often refer to Btus and omit specifying whether it is Btu per something >>such as per hour or minute. Contrasting, the “tons of refrigeration” is >>treated >>as an energy unit. And sometimes units are invented as if these I-P-units >>numbers were not hard enough to compare even if the terminology were unified. >> >>Why, oh why, don't writers recognize that since all (or most) electricity >>coming >>to a house changes to heat, and that both electricity and heat can and should >>be >>measured in the same unit? If they did, one would learn that to remove 100 W >>heat flow coming from that lightbulb requires up to 100 W electricity >>flow into >>the air-conditioning unit to power its fans, compressors, and controls. That >>would reduce the usual gibberish to the simple "a 100 W lighbulb, if lit, >>requires up to 100 W of electrical power to remove its heat in hot >>weather." To >>be a bit more informative, a writer could add that if the electricity comes >>from >>thermal power plants, it takes 300 W of fuel energy flow to power the 100 W >>lightbulb and consequently 300 W to power the air-conditioner, or 600 W >>altogether. And perhaps also hint that a person contributes about 100 W >>sitting >>idle. Not much can be done about the latter load short of going outside, >>which, >>come to think of it, may be healthy as well as frugal. The impact of >>metabolism >>is obscured by the usage of the DV measured in Calories (or calories) in the >>U.S. so that nobody can correlate that heat production to cooling without >>converting. >>Stan Jakuba >> >