----- Original Message ----- From: <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Sunday, October 06, 2002 2:53 PM Subject: Re: cars, air L3er
> On Fri, 4 Oct 2002 13:54:47 -0500, Dan Minette wrote: > > >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 > > I am not sure how you could have attempted to reach a conclusive efficiency > number by this method. It is an extremely complex calculation and then only > valid in the particular case that you analyze. > Your efficiency number for internal combustion engines above is based on > extrapolated data taken prior to 1975. It is also an analysis of efficiency > IMPROVEMENT and does not necessarily reflect the efficiency of converting > btu's to usable work. > I will also note that this was a Brazilian web page and that Brazil gets I > think at least 75% of its energy from hydroelectric :) (I only point this out > to note that the situation will be different in every locale). > > Anyhoo, here is one that says the IC engine is 20% efficient. > http://ffden-2.phys.uaf.edu/102spring2002_Web_projects/Z.Yates/Zach's%20 > Web%20Project%20Folder/EICE%20-%20Main.htm > > This one gives 26% thermal efficiency and doesn't give a number for > mechanical efficiency(which would make it even lower) > http://www.auto-ware.com/combust_bytes/eng_sci.htm > > I am not trying to prove you wrong here, I am just trying to show you that > there is not much agreement on precise numbers and you can't write off a > potentially beneficial technology based on a back of the napkin calculation That's fair enough, I guess. I did the back of the envelope calculation far enough to get to less efficiencies with very generous allowances to the new technology. As you pointed out, 40% may be high for an internal combustion engine. However, the project tripped up my BS detector early on, so I was looking mainly for correlation. Let me explain some of the basic reasons the BS detector was tripped. First, I should also give my perspective. My job is, basically, to provide new technology. As I've mentioned, while my innovations have not been earth shattering, the guys down the hall have invented a technique that was half of the technology that cut finding costs for oil by > $5.00/barrel. But, at the same time, I've had to listen to zillions of smoke and mirror presentations on new technology. I've developed a test to seperate the wheat from the chaff that has worked pretty well over time. This report tripped my BS detector. Let me explain why. 1) First and foremost, compressed air is not new at all. The technology is rather old. Air compressors have been around for a century. Compressed air cars have been proposed for years. There is nothing that seems to jump out and say "this new technology gives a factor of two improvement." I've seen that elsewhere. For example, the factor of N improvement in computing now allows for the design of formation evaluation tools that would have been impossible 20 years ago. In my field alone, I can do things that were impossible for me earlier. As a result, the results are much better. An old colleague of mine gave a good rule of thumb on this. "The guys before you weren't idiots. Why didn't they come up with this?" If you can provide a good answer for that, (they didn't have the tools I have, for example) then there is a good chance you are on to something If not, its usually worth rethinking your stuff seriously. If its that obvious, then reasonable people are not likely to overlook it. 2) The numbers are not proven. No one has tested the car. So far, its vaporware, not hardware. http://www.spacedaily.com/news/020928042702.fkqpd20t.html gives a review of this. Now compressed air, even though its old technology, is improving, so the possibility is not zero. But, looking further, one needs a good way to recover the head from the air expanding. The temp is 400C, so there are ways to do that, but recovering waste heat is a problem for all engines. I'm guessing that my figure of 90% efficient for the engine is really way to high, now. 3) The energy density available in compressed air isn't all that much, unless one has _extremely_ strong tanks. The numbers they quote at http://www.bellwetherinteractive.com/mdi/specifications.html is for about 300 atmospheres of compressed air and a total of 3200 cu. ft. Clearly, that's 3200 cu ft. compressed into 10.7 cu. ft, becasue 3200 cu. ft. is far bigger than the entire car. So, the total stored energy available is calculated at 8.78 x 10^6 Joules. Let me give you how I calculated this. 300 atmospheres is 3.1 x 10^6 kg/m^2 pressure, or 3.04 x 10^7 N/m^2 pressure (1 g = 9.8 m/s^2) or 3.04 x 10^7 J/m^3 energy density (multiplying numerator and denominator by a meter). 10.7 cubic feet is about .3 cubic meters. So, the total energy is about 9.2 x 10^6 Joules or about 2.550 kWh. Hmm, the efficiency of the system, after the electric power reaches the station and before the engine wastes energy is low. From the charger taking 4 hours and the power of the charger, we have 22 kwH to charge the car. That is consistant with the $2.00 figure. Feel free to check my figures, but it appears that the energy storage is consistant with about 12% efficiency. Which kinda makes sense, because air compression at high pressures is not terribly efficient. > I am not sure where you are getting 50% transmission loss. It may be valid in > some but not in all cases. I would bet that it represents close to a worst > case. It's common case for a household. That's one reason why the price of electricity for a big company is in the $.03 to $.04 range, while residential is closer to $.08-$.10. Another examples of this is the big difference between electric and oil/natural gas heating costs. > > I can play with numbers here too. If I reduce the transmission loss number to > 30% the air car becomes 30% by your method. Also, the option is now in the > fleet owners hands to have a power plant on site using whatever generation > method appears feasible. Fleet owners can buy power cheaper, that's true. > I was oversimplifying about AC. You probably also know that the photovoltaic > industry is booming in Africa as there is many places where the grid has yet > to reach. But, if their transportation needs are met, and they have a steady > supply of cheap fuel, they may have little need to change. > > >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. > > It is not fair to say that unless we have determined that they are less > efficient than IC (you have not convinced me yet :) or it is an additional > transportation service. Well, the numbers I gave, from their site, looks like it is very inefficient. I admit I may have made a math error, so lets try the calculation a different way. Assuming the velocity of the average air molocule is 500 m/s (obtained through Boltzman's constant), we get about 1.3*10^7 Joules of energy for the 111 kg of air that's in the tank. > >The US does this by having pollution control equipment on > >autos. They both decrease the fuel efficiency of the cars and > >significantly reduce pollution. > > I don't follow you here. Burning more fossil fuels, whether they are emitted > either way will not result in cleaner air than burning less fossil fuels. If some of the "wasted" eneregy goes to running pollution control equipment, it does. Pollution control takes energy. > > >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 car doesn't have to be refueled at home. First applications will likely be > fleet operators. They could have diesel or propane powered compressors at > their base, eliminating the electrical link all together. Public filling > stations could also be configured the same way. That's fine. However, it does appear, unless I made a factor of 8 or so error in my math, that the process of getting the compressed air in the tank isn't very good. Further, the tank appears to be a 77 gallon tank. Yet, it contains less energy than 1 gallon of gas. That is not efficient energy storage. It appears that the car must have tremendous mechanical efficiency and be run at very slow speeds to work as advertised. I rather suspect that the real figures are much worse. > >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. > > They want the big cars in the US and Canada because fuel costs are low. > Most of the rest of the world drives smaller cars (or scooters or bicycles) > because fuel is too expensive. To be exact, because the taxes on fuel are much higher. >Actually, everyone WANTS big cars but sometimes they just aren't practicle. Or, the government decides to make them prohibitively expensive. Even in the US, taxes have been a significant part of fuel costs. > Which has limited capacity at many sites ideal for expansion of wind power. > Actually, I was referring to the fuel supply side. The mines, wells, > transportation and processing industries are in place, running efficiently and > cheap. Alternatives require a very large investment up front and do nothing for > local economies that rely on these industries. > > >>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. > > 1.7c/Kwh I believe. However, wind power subsidies will most likely be > removed in the next couple of years as it has been proven to be self > sustainable. Meanwhile they will be building a $58b wine cellar at Yucca > Mountain. Which is paid for out of a special nuclear power plant tax. IIRC, there's >20 billion already collected. But, since a person killed by nuclear power is hundreds of times more dead than a person killed another way, its worth every penny. :-) > > I can't find any numbers for nuclear right now. Alot of the current subsidy > appears to be clouded in insurance and risk assumed by the government. I'll > adjust my statement by saying that large scale wind power is relatively new > and has been far less subsidized than nuclear over its history or at a similar > stage in its development. Its hard to say because the focus of nuclear reactors was weapons reasearch. > >>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. > > I'll assume you meant 0.5% in the US. It is somewhere around there. Nope: http://www.eren.doe.gov/consumerinfo/refbriefs/da8.html > > Agreed. the infrastructure is in place and the bugs have been worked out. Ah, its much more than that. My friends have developed technology that allows 1 platform to cover much more production than was possible 10 years ago. That alone has cut billions off the cost of production. The reality is that the oil and gas sector have been improving their efficiency so well, that the alternative energy sources have not been able to catch up at all. > I have a feeling it will provide more opportunity for de-centralizing power > generation and micro-griding using combinations of small gas turbine plants, > wind and solar. Also a good strategy for a country worried about terrorist > attacks. > > Let me clarify my position here. The only reason I got involved in this > discussion is because I object to people using terms like "PR" and "wishful > thinking" to immediately write off potentially beneficial technologies. I can understand that. But, let me point out, its not immediate. I'm probably a bit older than you. I remember the PR for these technologies being about the same for the last 30 years. So, I look for an indication of real new technology advances. When I don't see them, I tend to conclude that this is just more of the same. >I believe the subject deserves exploration. When I read about things like this I > immediately set to thinking about its benefits and if beneficial, how it could > be made viable. I'm not an engineer but I would like to play one on TV :). I can understand that. When I read about things like that, I do a back of the envelope engineering calculation. If those calculations don't add up, I'm rather skeptical. Further, there is a means that engineers and scientists use to discuss real breakthroughs. They put hard numbers up front. They highlight real advances and explain how they achieved them. I've been around both real advances and PR BS for years now. Occasionally, real advances are sold with BS. However, the engineers can usually get enough of the hard numbers that they have to sell the advance to the other technical people. When the numbers get softer the harder you look, then I'm skeptical. >I don't have the time to get into a war of numbers or brain size here (I will > concede on that one quite early:). You are welcome to prove the futility of > this technology to me. I would consider you doing so a service to me. I'm not quite sure where the idea that a number of us just like to use this as a forum to show off how bright we are. What good is that? I would invest such an effort to impressing customers, not a mailing list. I do have a preference for hard data over soft data. I do have a preference for critical thinking over simply typing one's own preferences. As I stated elsewhere, I like it better when others don't agree with me, and can back up different positions to the point where I need to rethink my own. Or, if they provide insight that is outside of my scope of expertise. Dan M. _______________________________________________ http://www.mccmedia.com/mailman/listinfo/brin-l
