Pat, You are probably right that energy is the better word. However, the fact is that you had better look at both. The power, both in charge and discharge is critical to the efficiency with which charge is stored and recovered. It is also key to the waste heat in the battery itself, and critical to whether it works or catches fire. Energy is simply the time integral of power as far as totals, but the power is actually the key to efficiency (slow charge/discharge wastes much less energy as heat). Actually, a similar situation exists in gasoline-fueled cars, at least on the usage side (you can refuel as fast as you would like). If you fill your tank, you put in a certain amount of energy. How far you get depends on whether you drive like a hot-rodder or conservatively, as well as on the mass and frontal area of the vehicle. The power levels demanded affect the efficiency of energy usage. They can't be separated as neatly as you would like; however, I could have made my remarks clearer.
--- On Tue, 3/31/09, Pat Naughtin <[email protected]> wrote: From: Pat Naughtin <[email protected]> Subject: [USMA:44256] RE: Nail in the coffin for hydrogen (at least for now)? To: "U.S. Metric Association" <[email protected]> Date: Tuesday, March 31, 2009, 3:08 PM Dear John, I have interspersed some remarks in red. On 2009/03/31, at 10:34 PM, John M. Steele wrote: Yes, it is waste. Unfortunately storing electrical power in a battery, then withdrawing it also involves waste. Which is more wasteful is debatable, although the edge probably goes to the battery, at least when measured as power from the wall. You write 'storing electrical power in a battery' and I ask, how is this possible? Since power is, by definition, 'the rate at which you use energy' how can that rate be stored? Isn't that statement the equivalent to saying, as you fill you car, 'I am putting some 100 km/h in my tank to store for later? You can store energy but you can't store power. When the total efficiency from fossil fuel to kWh delivered from a battery is considered vs steam reformation of fossil fuel to hydrogen to fuel cell output in kWh, the advantage may go to hydrogen but at MUCH higher expense. I suppose that you have used the expression from fossil fuel to kWh to mean the energy contained in fossil fuel to the energy that can be extracted from the total energy stored in a battery. For comparison between these different types of energy, might I suggest that you use the single international unit for energy (joule) from the International System of Units (SI)? As you probably know, the joule has been agreed and supported by various international agreements since 1889. I think that in this paragraph that you are confusing words to differentiate the different names for different forms of energy with energy measuring words; using joules for all forms of energy removes the second half of this problem and you can then concentrate on the words for the different energy forms. For both, the weight and volume of tankage (and fuel) to contain the "fuel" puts both at a huge disadvantage compared to gasoline or diesel, hence hybrids. Tankage? There is no "good" answer, but perhaps a "less bad." I agree. --- On Tue, 3/31/09, David <[email protected]> wrote: From: David <[email protected]> Subject: [USMA:44247] RE: Nail in the coffin for hydrogen (at least for now)? To: "U.S. Metric Association" <[email protected]> Date: Tuesday, March 31, 2009, 4:39 AM As for hydrogen, isn't it wasted energy to use electricity to get hydrogen instead of just using the electricity to power the car direct Cheers, Pat Naughtin 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 for more metrication information, contact Pat at [email protected] or to get the free 'Metrication matters' newsletter go to: http://www.metricationmatters.com/newsletter to subscribe.
