Yes, indeed, Gene. Various conversion charts list dozens of units for power and energy, as you know. Some beef up that number by listing W and kW, or cal and kcal as examples, to be separate units. USMA know better. Thank you for writing, Gene.
On Sun, Apr 10, 2016 at 4:21 PM, mechtly, eugene a <mech...@illinois.edu> wrote: > Good reasons for your preference for power, Stan! > Your reason I like best is that there are many fewer units in circulation > for power > (You select only one, watt) than for energy, (You cite four.) and for time > (You name six.) > and the difficulty of making comparisons is reduced. *Unnecessarily many* > possibilities are avoided. > Fewer comparison errors are likely. > > Gene. > On Apr 9, 2016, at 4:13 PM, Stanislav Jakuba <jakub...@gmail.com> wrote: > > > Here are reasons for the preference: > > Expressing power values in watts, rather than in the units of energy and > time, has the advantage of eliminating the confusion that results from the > existence of multitude of units for energy (J, Wh, cal, Bty, ......) and > for units of time (hour, day, month, week, year, minute, .....). That can > make comparisons difficult, confusing and conversions may introduce errors. > Furthermore, the unit of time is often not expressed *at all *as is > commonly done in, among others, the DOE documents. > > As for the unit watt itself, it was coined to eliminate (for reasons > obvious to most USMA) all the prior power units such as the hp or the ton > (of ice). > > There is no doubt that using only one unit for a physical quantity > improves communication and helps eliminate > accidents/injuries/misunderstandings/errors. > > It is a sad state of our education, on all levels, and text books, that > one meets *engineers* who: > - try to convert kW to kWh (it is impossible) > - consider W a unit of power and kW a unit of energy > - claim to pay in their utility bills for kW (instead of kWh) > - are unable to convert Wh to SI (J/s x 3600 s = 3.6 kJ). > > Metric Today had an article about this a long, long time ago. Perhaps I'll > attach the manuscript. Yah, here it is. > Stan Jakuba > > > > > On Sat, Apr 9, 2016 at 11:16 AM, mechtly, eugene a <mech...@illinois.edu> > wrote: > >> To Howard (Small), >> >> Here is the answer to your question: >> >> Stan prefers discussing Power in watts (W) or in its SI decimal multiples >> (e.g. GW) >> averaged over a specified or implied period of time rather than energy in >> joules (J) or (e.g.GWH), >> processed over that that same period of time. >> >> Either method can be accurate in SI Units of Measurement!, and is >> acceptable as a matter of preference. >> >> Eugene Mechtly. >> >> On Mar 29, 2016, at 5:23 PM, Howard Small <howard.p...@comcast.net> >> wrote: >> >> Why does the graph say GW instead of GWH? >> >> Howard >> >> >> >> On Mar 29, 2016, at 2:17 PM, Stanislav Jakuba <jakub...@gmail.com> wrote: >> >> Friends: >> Attached is the graph showing the output for the requested non-renewable >> energy sources. With it, at the bottom on the same page, is the earlier >> graph for wind & solar. It is drawn on the same scale thus making a >> comparison between those two groups of sources easy. >> >> Both graphs show the history of only one form of energy - electricity. >> What is the chance that W&S, the only grow-able sources, will ever provide >> the ~400 GW shown in the upper chart? Or the ~3200 GW the U.S. is consuming >> overall? >> >> Unlikely, isn't it. That hopelessness can be seen better yet in the Prof. >> Brownridge's charts. Click this link Dennis Brownridge, U.S. Energy >> Sources (charts 1-8) >> <https://urldefense.proofpoint.com/v2/url?u=https-3A__www.dropbox.com_s_9jdbfnvbfzj0xt8_U.S.-2520Energy-2520-2526-2520CO2-2520Emissions-252C-2520Charts-25201-2D8-2520-2528Sources-2529.pdf-3Fdl-3D0&d=BQMFaQ&c=8hUWFZcy2Z-Za5rBPlktOQ&r=BpxbfWo0gcPQHL0R58p0D96tVlzZlsjR_iWGK6ETi80&m=YzY_J_-3Qk_r724SMhYMAjH5-Hsjn442Sb_YHc5bpr4&s=Tqw8sFP44WvJVNfHCdvsknk11AkyoTayxKSU8UmgvAg&e=> >> and >> see plate # 5; it illustrates the above traces in vivid colors. Notice how >> easy comparisons among documents are with SI units in both illustrations. >> >> Recalling the earlier chart that had all the renewable sources shown it >> may amuse you to read that Dep't of Energy values the traces as follows: >> >> *Between 2005 and 2015, electricity generation from solar increased 48 >> fold, from 550 GWh to 26,473 GWh. * >> >> *Biomass increased 18.3% from 54,277 to 64,191 GWh, and geothermal >> increased 14.1% from 14,692 to 16,767 GWh.* >> >> True, but how much is 14 % of very little? And 48 times more of nothing >> may not be all that much either. But it sounds good. The drop in hydro >> better be not mentioned. >> >> Viewing the trends confirms my 40-years old conviction that If mankind >> were to rely mainly on renewable sources for energy, as it did 2-1/2 >> centuries ago, starvation and social unrest would result due to energy >> skyrocketed cost, unreliable delivery and population growth. Being involved >> in the clean renewables since the '70s, I remember that effort sparked by >> proclamations such as these two examples: >> >> *In 1973, Walter Morrow, Associate Director of Lincoln Laboratories at >> MIT predicted that the US would generate between 750 to 1500 GW from direct >> solar by year 2010. * >> *In 1978, Ralph Nader predicted “Everything will be solar in 30 years.” * >> >> Stan Jakuba >> <Graph for Me.pdf> >> >> >> <Graph for Me copy.pdf> >> >> >> > <Energy & power for MT2.doc> > > >
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