Talk:Hybrid car

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Regarding plug-in hybrids, the Carbon emissions are similar to those of the normal hybrid assuming coal plants (eff=~35%) due to the poor charging/discharging efficiency of NiMH batteries. Lithium batteries would likely swing the efficiency in favor of the plug-in, by about 30-40%, due to having very good charging/discharging efficiency. Also, I think pursuing plug-ins along with other variable sources like wind would work wonderfully with an intelligent grid. Speaking of which, we should probably include an article on implementing demand side initiatives in order to facilitate the use of sporadic renewables.

Something interesting regarding the stop/start windows of the Prius. This is purely speculative, but I think someone at the EPA noticed the behavior of some of the extremely fuel efficient drivers and realized that they were probably cycling the catalytic converter a lot due to having the engine off and the vehicle moving for much longer than normal time periods during colder times of the year, which would naturally lead to more HC emissions per mile since the vast majority are during warm up when the converter is lit. As a result, on their newer hybrids, the engine off intervals are much shorter by design , I'm guessing in order to minimize the amount of time the catalytic converter can be cooled, and consequently, making it harder for the driver to "pulse and glide". This post was unsigned by 91.121.120.18

Obviously, if you can guarantee that the PHEV power source is renewable and non-emitting, then this puts a better complexion on the technology. However, I disagree that the holistic efficiency from coal plants is similar. If we take the Prius as our base, the efficiency of the Atkinson cycle engine is higher than that of an Otto cycle and I've seen figures of 35-40% from fuel to wheels (presumably on test beds). Your figure of 35% for coal-fired power is slightly optimistic, as it is top end of the range (28-35% is often cited, with ~32% as average), but this does not take into account the energy losses due to the mining, processinf and transport of the coal (up to 50% for deep mines), pulverisation, internal power use (generally ~8% of the electricity generated is used within the power plant!), transmission losses between the alternator and the power socket the car is plugged into (typically 10%), the efficiency of the charger (~90%) and the efficiency of the Li-ion (~90% when new, dropping to 50% after 2 years - whether used or not!!!!). Also Li-ion does not like high short-term discharge cycles (acceleration) which reduces the life and should be coupled with supercapacitors to cater for this. Then there is the cost. A 50 Ah 240 V Li-ion battery with supercapacitor is nearly the same price as the Prius itself, according to one article I read. This would give the Prius, with a new battery, a range of ~50 km under urban conditions at speeds under 50 km/h (above which the engine kicks in). Sorry!

I'm pretty sure that the guys who achieve phenomenally low consumption (or high mileage) must do all sorts of acrobatics, often illegal. I'm thinking of actually cutting the ignition when possible, sitting right behind heavy vehicles to be drawn along by the slipstream etc. Also, those who convert a Prius (wouldn't work with a Civic) into an EV can hardly count, either. I notice the most extreme figures on both my reference sites have now disappeared. Then there are always liars!!!!--Eewadmin 04:30, 21 March 2008 (EDT)

On reflection, this discussion may be bordering more on Forum, rather than Wiki material. My own contribution contains too much speculative and unsubstantiated material, see the talk page guidelines linked in the introduction to the edit section! Mea culpa! --Eewadmin 05:58, 24 March 2008 (EDT)

Regarding the efficiency of plug-in hybrids, an example of this IMO is Toyota's plug-in Prius, that only uses about 120Wh/km over the Japanese 10-15 driving cycle assuming conservatively that the pack is discharged to 40%, but when considering the charging efficiency of NiMH batteries, this jumps to about 180Wh/km, and after factoring in electricity generation/distribution at ~30-50% (conventional coal to combined cycle natural gas) it jumps to ~360-600Wh/km well to wheels. Compared to the conventional Prius that manages roughly 2.8l/100km, or 270Wh/km over the same cycle, or assuming the common figure of 80% efficiency extracting, refining, and distributing efficiency for gasoline from oil, ~340Wh/km, which is likely equal to, or less than, the energy consumption of a plug-in Prius. Anyway, just some hard numbers for that section if more info is needed. --Roflwaffle 05:19, 16 April 2008 (EDT)

Thanks for this info: I've incorporated it into the article with small editing modifs. I took the opportunity to add some other small modifs, including tidying up the references. Nothing very substantial. --Eewadmin 06:44, 16 April 2008 (EDT)

I found something even better and added it after your portion. I think brevity is better in this case. --Roflwaffle 00:53, 20 April 2008 (EDT)

OK by me! Can you please sign your contributions on Talk pages? The easiest way is just to click on the sig icon (2nd last one) on the Editing Talk pages. Alternatively, you can type --~~~~ at the end. This is not necessary for the articles, unless you particularly wish to. The purpose is to let others follow a discussion; you can imagine that if several guys were having a heated discussion on a point, it could be quite confusing unless a reader could identify the protagonists: you risk nothing by doing this. Thanks!--Eewadmin 10:31, 20 April 2008 (EDT)