[quote]mistersniffles wrote:
compared to the internal combustion engine which is only around 10%.[/quote]
Is that still accurate? I remember hearing that 10% figure when I was a kid and when 5 liters V8s produced 225hp and got around 12mpg. Now, we have 3.5 liters V6s that can produce more HPs and get at least 25mpg Surely, the efficiency of the combustion engine has increased somewhere along the line?
[quote]Kailash wrote:
Don’t forget that solar is already fusion![/quote]
And by the way:
Super-long term: matter-antimatter annihilation. As close to 100% efficiency as we’re gonna get, given our current knowledge of physics.
I don’t believe we have any example of that in nature; we’ve done it (“it” being create anti-matter) in our various particle accelerators and colliders. Not in an energy efficient way either.
[quote]pookie wrote:
mistersniffles wrote:
compared to the internal combustion engine which is only around 10%.
Is that still accurate? I remember hearing that 10% figure when I was a kid and when 5 liters V8s produced 225hp and got around 12mpg. Now, we have 3.5 liters V6s that can produce more HPs and get at least 25mpg Surely, the efficiency of the combustion engine has increased somewhere along the line?
[/quote]
I think most conventional cars are around 20-30% nowdays.
Methanol, ethanol, and biodiesel can all be produced from cellulose, which is contained in every part of every plant (that’s what the cell wall is made of). The cellulose is broken down to carbon monoxide and hydrogen in a reformer at high temperature.
The CO and H is called synthesis gas, or syngas. This syngas is then sent to a gas cleaning section which removes any tar, olefins, ash, heavy organics, and other impurities which could dilute the next reaction or spoil the catalyst.
The clean syngas is then compressed to the range of 1000-1700 psi and fed to a catalytic reactor (Fischer-Tropsch). That’s where the magic happens, and your final product is formed, be it C1, C2, or biodiesel. The remaining steps in the process are simple distillations to purify the product.
A link for biodiesel, since I don’t know too much about that process:
http://www.choren.com/en/biomass_to_energy/carbo-v_technology/
My company is working on purchasing a plant in Mississippi which will be converted to produce ethanol from waste wood feedstock. It’s pretty interesting stuff.
The above link has a cool animation sequence that pretty much gives you the basic idea of what’s going on. The methanol and ethanol Fischer-Tropsch reactions differ only in catalyst type, CO:H2 mole ratio, and T/P.
They have also cultured yeasts that are capable of breaking down and fermenting cellulose. I don’t know what is keeping them from using these strains though.
[quote]Steel Nation wrote:
Methanol, ethanol, and biodiesel can all be produced from cellulose, which is contained in every part of every plant (that’s what the cell wall is made of). The cellulose is broken down to carbon monoxide and hydrogen in a reformer at high temperature.
The CO and H is called synthesis gas, or syngas. This syngas is then sent to a gas cleaning section which removes any tar, olefins, ash, heavy organics, and other impurities which could dilute the next reaction or spoil the catalyst.
The clean syngas is then compressed to the range of 1000-1700 psi and fed to a catalytic reactor (Fischer-Tropsch). That’s where the magic happens, and your final product is formed, be it C1, C2, or biodiesel. The remaining steps in the process are simple distillations to purify the product.
A link for biodiesel, since I don’t know too much about that process:
http://www.choren.com/en/biomass_to_energy/carbo-v_technology/
My company is working on purchasing a plant in Mississippi which will be converted to produce ethanol from waste wood feedstock. It’s pretty interesting stuff.
The above link has a cool animation sequence that pretty much gives you the basic idea of what’s going on. The methanol and ethanol Fischer-Tropsch reactions differ only in catalyst type, CO:H2 mole ratio, and T/P.[/quote]
[quote]pookie wrote:
mistersniffles wrote:
compared to the internal combustion engine which is only around 10%.
Is that still accurate? I remember hearing that 10% figure when I was a kid and when 5 liters V8s produced 225hp and got around 12mpg. Now, we have 3.5 liters V6s that can produce more HPs and get at least 25mpg Surely, the efficiency of the combustion engine has increased somewhere along the line?
[/quote]
The internal combustion engine is used for more than automobiles.
Seriously coconut oil. Its better than petrol and you don’t even need to change the cars.
[quote]mistersniffles wrote:
The internal combustion engine is used for more than automobiles. [/quote]
My question was mainly about the oft stated 10% efficiency, regardless of where the combustion engine is used. I’m pretty sure cars are the most prevalent use of them. I’ve heard 10% all my life, but, as my example mentioned, it can’t be 10% for 1970s muscle car engines and still be 10% in a 2007 VW Jetta TDI.
[quote]big balls wrote:
Seriously coconut oil. Its better than petrol and you don’t even need to change the cars.[/quote]
Where do you get enough coconut oil to replace 80 million barrels of oil per day?
It’s like those guys who convert their diesel VW to run on McDonald’s used french fry oil. It only works when there’s one or two of those guys in a town. If everyone did that, Mickey D couldn’t make enough fries in a year to meet demand for a single rush hour.
Alternative energy ideas are great, but they have to be scalable.
[quote]pookie wrote:
mistersniffles wrote:
The internal combustion engine is used for more than automobiles.
My question was mainly about the oft stated 10% efficiency, regardless of where the combustion engine is used. I’m pretty sure cars are the most prevalent use of them. I’ve heard 10% all my life, but, as my example mentioned, it can’t be 10% for 1970s muscle car engines and still be 10% in a 2007 VW Jetta TDI.
[/quote]
The 10% figure seems awfully low for any engine but it is possible if you take all the wasted energy in the rest of the vehicle into account, such as braking, etc.
Hydrogen :-). We get power from solar panels, then we use that to split water into oxygen and hydrogen, and then combust it; products include energy and water. Turns out the making of bonds is much more powerful(in terms of energy wise) as breaking bonds.(Why a hydrogen bomb is stronger then plutonium).
If we are not using the energy, we can store the hydrogen. Leaving us with no C02, C0 or anything that can become public enemy number one.
[quote]SeanT wrote:
Hydrogen :-). We get power from solar panels, then we use that to split water into oxygen and hydrogen, and then combust it; products include energy and water. Turns out the making of bonds is much more powerful(in terms of energy wise) as breaking bonds.(Why a hydrogen bomb is stronger then plutonium).
If we are not using the energy, we can store the hydrogen. Leaving us with no C02, C0 or anything that can become public enemy number one. [/quote]
But that is not a very energy effecient way to do it. If you can make enough electricity from solar to make that much H then you may as well use an electric car (cut out the middle-man). Add the fact that H powered cars are a long way off, it doesn’t look like a good option.
[quote]Zap Branigan wrote:
The 10% figure seems awfully low for any engine but it is possible if you take all the wasted energy in the rest of the vehicle into account, such as braking, etc.[/quote]
Good point. 10% of what exactly? The complete energy that can be extracted from burning gasoline chemically? It’s certainly not 10% of E=mc^2 with the weight of the gasoline as m, that’s for sure.
[quote]Zap Branigan wrote:
I have been hearing about a breakthrough in solar technology for years but it seems unlikely that we can manufacture enough cells to generate electricity on a massive scale.[/quote]
There is also the issue of the highly toxic chemicals used in solar cell production.
A different tangent to the solar cell is the use of high temperature resistant mirrors (called Heliostats) to reflect sunlight to heat water and drive a turbine . We are building a couple here in Aus and I believe Spain has a few already and is building more.
[quote]SeanT wrote:
Hydrogen :-). We get power from solar panels, then we use that to split water into oxygen and hydrogen, and then combust it; products include energy and water. Turns out the making of bonds is much more powerful(in terms of energy wise) as breaking bonds.(Why a hydrogen bomb is stronger then plutonium). [/quote]
“Combusting it” will not give you fusion, only combustion. What you’re describing are run-of-the mills chemical reactions (electrolysis to separate water in H and O2, and combustion when burning either one), that’s not in any way fission or fusion. No atom nuclei are split, none are fused together.
[quote]SeanT wrote:
Hydrogen :-). We get power from solar panels, then we use that to split water into oxygen and hydrogen, and then combust it; products include energy and water. Turns out the making of bonds is much more powerful(in terms of energy wise) as breaking bonds.(Why a hydrogen bomb is stronger then plutonium).
If we are not using the energy, we can store the hydrogen. Leaving us with no C02, C0 or anything that can become public enemy number one. [/quote]
No! Bad Sean! Down!
[quote]pookie wrote:
Zap Branigan wrote:
The 10% figure seems awfully low for any engine but it is possible if you take all the wasted energy in the rest of the vehicle into account, such as braking, etc.
Good point. 10% of what exactly? The complete energy that can be extracted from burning gasoline chemically? It’s certainly not 10% of E=mc^2 with the weight of the gasoline as m, that’s for sure.
[/quote]
The word “efficiency” usually refers to 1st Law of Thermodynamics Efficiency, which is [Work Out / Energy In].
‘Work out’, in this case, refers to work done from propelling your car; ‘energy in’ refers to the energy produced by burning gasoline. Around 70% of the energy produced by burning gasoline is not spent propelling the car, so a car operates at around 30% 1st Law efficiency. Some of the energy “wasted” is used to power the car’s peripherals, so it is not a total loss from a design perspective.
This is the “efficiency” number most often referenced, but it is a little simplistic.
A heat engine, which is what an ICE is, is driven by a temperature differential. Just like a hydroelectric plant will not do work if the water level behind the dam is the same as the water level in front of the dam, a heat engine can not do work if the ambient temperature is the same as the temperature the engine operates at.
You can calculate the theoretical maximum efficiency a heat engine can achieve by using the Carnot efficiency. [(Engine Temp - Ambient Temp)/ Engine Temp]. Temperatures measured in Kelvin.
Unless a heat engine is operated in an ambient temperature of absolute zero, it cannot achieve 100% Carnot efficiency.
You can calculate the “real” efficiency of an engine by calculating [(Work Out)/(Energy In)]/(Carnot Efficiency).
If the theoretical maximum efficiency a heat engine can achieve at a given ambient temperature is, say 65%, then getting a (Work Out/Energy In) efficiency of 35% isn’t bad at all. In fact, it is more accurate to say that the engine is operating at 54% “real” efficiency (.35/.65).
When you hear that a car is “operating at 30% efficiency”, that is most likely referring to (Work Out/Energy In). However, unless you’re driving around at absolute zero, it is theoretically impossible to achieve 100% efficiency. So simply saying “30% efficiency” is inaccurate. If the max efficiency possible in a given environment is only 65% (which is pretty typical in real-world situations), then 30% (Work Out/Energy In) isn’t too shabby.
The take home lesson here is to take every number you hear in the media with a grain of salt. Especially when it comes from media that doesn’t know the difference between energy and power.
[quote]gotaknife wrote:
…
A different tangent to the solar cell is the use of high temperature resistant mirrors (called Heliostats) to reflect sunlight to heat water and drive a turbine . We are building a couple here in Aus and I believe Spain has a few already and is building more. [/quote]
I have wondered if this was feasible.
[quote]tGunslinger wrote:
The word “efficiency” usually refers to 1st Law of Thermodynamics Efficiency, which is [Work Out / Energy In].
…
[/quote]
Great. Thanks.
Uncannily, that advice also applies to Jeffro’s every post.