----- Original Message ----- From: <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Friday, October 04, 2002 8:37 AM Subject: Re: cars, air
> On Fri, 27 Sep 2002 14:37:40 -0500, Dan Minette wrote: > This is a huge assumption. This vehicle has many inherent efficiencies that > might overcome these losses. Well, it would be very hard to believe. Lets look at some numbers. The general efficiency of an internal combustion engine is given in http://ecen.com/content/eee7/motoref.htm at around 40%. The initial efficiency of a big power plant goes up to about 60% http://www.ecoling.ch/englisch/thermal_power_plant.htm So, the electricity that gets to the pumps that compress the air is about 30%. Then, we have to figure in the efficiency of the compressed air pump and the air engine itself. The compressed air pump has two sources of inefficiency. The electric motor, which we can assign an efficiency of 90%, http://www.industrialcenter.org/Learn/Air_Compressor_Tutorial.htm#Economics %20and%20Operating%20Costs and the compressor. From the same source, leaks in an efficient compressor account for a 10% efficiency, so a generous efficiency is probably 80% for the compressor itself. , we are down under 25% by the time the air is in the car. Assuming 90% in the car, and we are close to 20%. So, for rough numbers, we are talking around 20% efficiency. > You underestimate the intentions of third world countries. One of the steps in > reaching developed country status is cleaning up air quality. Improvements in > transportation is likely to come before, or at least along side, residential > air conditioning. There are several parts to an answer for this. 1) Electrical power will not just be used for air conditioning. I'm not totally unfamiliar with Africa, BTW. I think I remarked here that I have an African "daughter" from Zambia (her church is a mission partner with our church and we're her home in the 'States while she goes to school nearby). Most people are not at the point where the incremental use of electricity will be AC. The per capita use is very low, and they will be able to use up all of their remaining hydro capacity without massive use of AC. 2) Addition commutes. That is to say it doesn't matter what order the consumption comes on line. So, if the additional use for purposes other than transport is greater or equal than the additional capacity available from non fossil fuel sources, then it is fair to say that the use of these cars will result in additional use of fossil fuels, no matter what the temporal sequence is. 3) Air quality is cities is a different question than consumption of fossil fuels. It may very well be reasonable to use more fossil fuels to have cleaner air. The US does this by having pollution control equipment on autos. They both decrease the fuel efficiency of the cars and significantly reduce pollution. > > There will be no overnight switch to electric vehicles. This does not diminish > their potential. I never really argued for a step function. Aren't these vehicles compressed air? My guess is that fuel cells would be a more likely source for electric cars. That may be feasible. Among other things, they don't have the transmission loss problem associated with a car that is "refueled" at home. > > The greatest value in zero emission vehicles is in centralizing harmful > emissions. Moving the exhaust source from the tailpipe to the smokestack > gives the ability to control and position emissions so they don't impact urban > airsheds in the same way. That's perfectly valid. I have no problem with that. I do have a problem with the sales pitch for these vehicles that includes false statements. The reality is that the use of zero emission vehicles will result in lower energy efficiency. You could argue that they are lighter, and will thus be more efficient. However, the power source has, historically, actually been heavier for comparable output. The fact that a small electric vehicle is more efficient than an 8 passenger SUV isn't really relevant. A small gas powered car is still more efficient; but people want the big cars. >Although they may not limit total emissions, > planners now have the ability to apply more efficient pollution controls and > distribute it over a larger area. While this may not affect global warming, it > may make Houston smell better. :) Actually, not. Houston smells the way it does because of the petrochemical industry. It will make _Houston_ smell worse, because there will be greater output at the petrochemical plants. > >As for wind, a good first order approximation is that it is a PR cost for > >major oil companies and politicians. It has to be highly subsidized to > >compete. > > That statement is quite true and I would expect no less from oil companies or > politicians. Wind has no immediate large profit potential, as did, or does, > nuclear, in an economy with an established oil and coal infrastructure. > Huh? Any type of plant can plug into the infrastructure. The infrastructure is the transmission lines. > Wind has been far less subsidized than nuclear and has been growing at a > phenomenal rate over the past 10 or so years. Actually, not. Wind energy now gets a 1c per kwhour subsidy. Nuclear gets nothing like that. >Worldwide wind energy output doubling every 3 years or something like >that. Well, it is politically popular and subsidized. I couldn't get world figures, but at the present time it is 0.05% of the total energy supply. At that level, subsidized wind farm construction can be better seen as cheap political cover more than economically viability. >While i don't buy into many conspiracy theories of oil companies suppressing >innovation in transportation or power generation, I do believe they purvey the image >that it is inefficient, experimental and only of interest to engineering students >and tree-huggers. I have the analytical tools to personally crunch the numbers on this. I >However, for oil companies and politicians, everything is PR, right? :) No. Let me take a moment to point out that the oil industry has cut overhead overwhelmingly over the last 20 years to significantly reduce the price of oil. Even with the war scare raising prices to an artificially high level, oil prices are about half of what they were 20 years ago in inflation adjusted dollars. Indeed, one of the problems for other energy suppliers is that the oil companies are extremely good at providing very cheap energy. > >IMHO, articles such as this one shows the power of wishful thinking. > > What the air car offers is a clean energy storage option. Yes it does. What it does not offer is a clean, efficient storage option. Fuel cells may, in 5-10 years be far enough to offer than. If there is a tremendous demand for fuel cells, then wind power usage may increase 100x in the next 30 years to 5% of energy usage. Large scale use of wind power also suffers from the fact that there are few places with high sustained winds. After those are "harvested," it will be hard to find other good sites. Remember, wind power goes as v^3. > This is the technology needed to make intermittent renewable like solar and wind > viable for transportation. But with 20% efficiency? Now, if fuel cells can be made in an economically feasible manner, then they might provide a good source of stored energy for transportation. Then, we may see wind power climb into the few % of the total energy budget. That would be a step forward. Dan M. _______________________________________________ http://www.mccmedia.com/mailman/listinfo/brin-l
