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Old 12-08-2010, 05:10 AM   #191 (permalink)
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Originally Posted by NeilBlanchard View Post
...
This may make the engine a little more efficient, but at the thermal efficiency level -- why isn't an internal combustion engine as efficient (or even close to the same efficiency) of an electric motor? I'm talking quantum leaps here. Streamlining cranks ain't going to be enough.

It has to be the connecting rod / crankshaft that are causing the greatest loss within the engine, or the long 3 strokes of coasting, or something basic, that is keeping ICE's from being 50-60-70-80-90% efficient, right? ...
you cannot compare electricity to gasoline like that.
That is what this 16 page thread Started by Ernie Rogers is about (which took me a while to get, having gone into it with electrical bias too):
http://ecomodder.com/forum/showthrea...-evs-8099.html
And is also what is wrong with mpge.
The electricity has undergone the major heat losses at the powerplant, when they burned the coal or whatever to make the electricity. You are using a refined form of power. It would be like using compressed air to run an engine, and not counting the energy used to compress the air in the first place.

It isn't the crankshaft, it is thermodynamics.

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Old 12-08-2010, 10:13 AM   #192 (permalink)
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So, when you burn gasoline at near atmospheric pressure, about what temperature is generated? If you pressurize / compress it, the potential temperature gets higher?

I think I've read that natural gas electrical generation plants are about 60% efficient -- this is the electricity coming out; not just the turbines. How do they get such good efficiency?

Is external combustion capable of higher efficiency? The downside of external combustion (like steam) is that you have to preheat to get up to operating temperature, before you can do anything; I would expect?

How much efficiency is gained in say the Honda engines that have offset crankshafts? Someone mentioned that they thought some Honda engines were 47% efficient -- is this correct? Why can all engines get above say, 45%?

I understand that electric is in a different realm -- that is why I think EV's will be the answer to many / most transportation needs. The exercise in this thread is to try and push ICE's as high as they can go. I appreciate your patience on this process.
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Old 12-08-2010, 10:57 AM   #193 (permalink)
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some basics first, pV=nRT
Ideal gas law - Wikipedia, the free encyclopedia

its how a compression fire starter, and a diesel, work
homemade fire piston

so volume/temperature/pressure are all inter-related.

Also, please provide sources to efficiency links, it is hard to comment on "I think I read" with any degree of accuracy.
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Old 12-08-2010, 05:12 PM   #194 (permalink)
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Look at the "Gas turbine plants" section:

Fossil fuel power station - Wikipedia, the free encyclopedia

In looking into this again, I am finding that natural gas is "35-44% for today's simple-cycle gas turbine plants" but it could go up to 55%:

Natural Gas
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Old 12-08-2010, 05:59 PM   #195 (permalink)
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ah, well the more efficient numbers are because they are recycling much of the "waste" heat, a good plan generally speaking. They basically have a supply of water hooked up to the exhaust to make steam, and drive another turbine with that, fairly trivial to do with a land based plant.



Of course if you have some cold buildings nearby it is more efficient to use the "waste" heat to warm them directly than to burn more fuel to warm them and/or spin a steam turbine to make electricity to warm them.
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Old 12-08-2010, 06:45 PM   #196 (permalink)
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Going back a few comments to the video of which would be considered a pulse detonation engine. GE seems to hold quite a number of patents related.

Limiting parasitic loss is a large step towards efficiency from the mechanical side. Getting into recapturing thermal losses and making the conversion to a productive mechanical gain and or supplementing expending energy gains to the system is another issue of concern. Utilizing a higher percentage of the internal energy of the current available fuels is the goal of many labs here and abroad.

You all have talked about the many variables and means in which to do this. MIT and from the Sloan school of automotive engineering have many papers available related to the variables and ideas discussed here. The SAE site has many of the same and other white papers related as well. They will charge for some of these but much can be deciphered through the Abstract provided. Here's a fairly complete listing of all Sloan School papers published.

There's always more to learn even when you think you have a good handle on the methodology and information. However nothing beats empirical and practical testing of your ideas by building them.

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Old 12-08-2010, 07:36 PM   #197 (permalink)
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There was some discussion about the Crower 6 stroke a while ago, though Big Dave was convinced it has hit a dead end. Crower six stroke - Wikipedia, the free encyclopedia , sounds like it needs electric valve control instead of a cam to get through warmup.
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Old 12-09-2010, 08:17 AM   #198 (permalink)
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So, the reason the natural gas electricity plants can be so much more efficient is cogeneration -- you could have the gas turbines, then use the heat to power steam turbines, and then use the heat for nearby buildings. Copenhagen (apparently) has their efficiency up around 80% by doing this sort of thing.

Sounds great to me! And it makes electric cars look even better.
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Old 12-09-2010, 09:13 AM   #199 (permalink)
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Quote:
Originally Posted by NeilBlanchard View Post
So, the reason the natural gas electricity plants can be so much more efficient is cogeneration -- you could have the gas turbines, then use the heat to power steam turbines, and then use the heat for nearby buildings. Copenhagen (apparently) has their efficiency up around 80% by doing this sort of thing.
Well, copenhagen is on the cold side, average high temp in august is 68 degrees, so they can make use of the heat from the power plants directly for much of the year.

Other municipalities might be better off making electricity out of it and sending it where it is needed.


Quote:
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Sounds great to me! And it makes electric cars look even better.
I'm not so sure anymore, there are some serious issues using electricity in cars. Power to weight, Range, Cost, Efficiency, size, refueling time. I'm starting to think Algae or other biofuel is the best solution for vehicles (with some Rankine added downstream of the ICE, or??).

Here is a site which suggests that roughly 1/5 as much land is needed to power a car with Algae vs Solar panels: Fat Knowledge: Algae Biodiesel vs. Solar Panels

and if you look at the picture below, even the best batteries are weak in the energy density department (which means lots of dead weight and limited range and/or performance/efficiency):
http://upload.wikimedia.org/wikipedi...gy_density.svg
lithium ion battery is in the very lower left corner

The edison crew also posted on FB about it recently
Welcome to Facebook
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Old 12-09-2010, 10:45 AM   #200 (permalink)
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Sorry dcb,

"Here is a site which suggests that roughly 1/5 as much land is needed to power a car with Algae vs Solar panels: Fat Knowledge: Algae Biodiesel vs. Solar Panels"

I got excited when I saw this because I am a big proponent for bio/diesel aero transportation. It takes 5x the land to power the econo biodiesel versus the sports car EV.

I still think biodiesel is one of the best ways to go. Batteries are heavy, have little range, and are not environmentally friendly (disposal).

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