Electric Cars and Solar Power Kills babies.

[jmc]

I still don't understand how they could get away with actually closing down weather stations. You would have thought honest climate scientists would have picked up on it and kicked up a fuss.

[MSimon]

I still don't understand how they could get away with actually closing down weather stations. You would have thought honest climate scientists would have picked up on it and kicked up a fuss.

I think you have answered your own question.

[ravingdave]

1) But you don't want to buy another car for the other 10%. Example: shortly after graduating I had to drive most of the way across IL (about 700 miles in all, I think) to take the CPA exam. I could not have done that in an electric car.

2)Of course, many people who live in the city don't own cars at all. Electrics have to fit into a fairly specialized niche where you don't need power or distance, but it's too far to bike or walk.

1) It depends on three things, the price of petrol, the price of electricity and the capital cost of the vehicle. With the way the capital costs of vehicles are going with the tata ($1000) and the like, it may not be long before a vehicle will have a similar cost to 1 or 2 year's worth of fuel consumption. If that happens then you may well prefer to have two vehicles, one for short range commutes that runs on cheap electricity and one for the occassional long range commute which runs on more expensive oil. In terms of efficiency this makes more sense that a plug-in hybrid since the electric vehicle isn't lugging around the unecessary load of a petrol engine and the petrol vehicle doesn't lug around the unnecessary load of the battery.

2) Not just distances that are too far to bike or walk but also loads. I'm prepared to bike 10 miles, but not while carrying my weekly shopping!

I guess i'll butt my way into this conversation. I have long had an idea that strikes me as being the most sensible and well balanced thing regarding transportation vehicles. MSimon has already heard the idea and shot it down on the basis of cost. (or some such. I'm not sure I understood his criticism)

The idea is simple. You put a small, (5 hp @ 3700 watts ) motor generator optimized for one speed efficiency. (no pumping loses. H@ll, make it a diesel!) and a large enough battery to get you 10-20 miles.

The Motor/generator can start when you begin driving, and can run continuously while you are driving, (easily keeping up with the load in urban traffic, but falling behind in highway traffic) and continue running after you have arrived at your destination until it builds up your battery capacity to 100%.

By using a larger motor (say in the 20 hp range) this method ought to result in a vehicle with virtually unlimited range, even on the highway.

Of course everything would have to be managed by a controller with an evolved program to optimize it, but I see no major reason why the idea won't work.


Getting rid of an Engine, Transmission, axles, differential, radiator, and heavy duty suspension components ought to account for a sufficient weight savings to allow for a really decent range and performance.

I've actually been thinking for some time about building one of these contraptions, but I haven't been terribly happy with the choices of motors I find out there. My preference would be some sort of high torque wheel motor(with regen capacity), and I hear they are coming, but I know of no current supplier.

In any case, that's MY take on the issue.


David

[chrismb]

The idea is simple. You put a small, (5 hp @ 3700 watts ) motor generator optimized for one speed efficiency. (no pumping loses. H@ll, make it a diesel!) and a large enough battery to get you 10-20 miles.

Already been done. One application I've seen uses a sub 2 litre 90hp diesel motor to run a full-sized bus. It runs steady while the bus stops and starts, with energy recovery as well. The question of this setup was how to analyse the maximum 'duty cycle' [acel-decel-stop-repeat] that the bus could go through that the 90hp motor could do the job and how to maximise efficiency whilst minimising engine load and wear-out issues that you get with running smaller motors flat out.

You can also run non-otto cycles in the setup you're describing. The Atkinson cycle runs an over-stroked power phase. This is good for efficiency but bad for engine flexibility. But you don't need that flexibility if you're using it to generate power rather than pull away. The Prius uses an Atkinson cycle rather than Otto, I'm lead to believe, for much the same reason.

There does seem to be less-and-less that is new under the Sun. So long as we don't fall into the same trap as the Victorians (might as well close the patent office, all is now known) and keep fiddling with the ever diminuishing details then maybe there are a few doors still to discover.

[MSimon]

Changes in material technology change possible technology.

Cheap aluminum made the Wright Bros. possible.

Cheap carbon fibers will be the next big push. Batteries are good enough. What is needed is drastically lower vehicle weight. Wheel motors would help.

[ravingdave]

The idea is simple. You put a small, (5 hp @ 3700 watts ) motor generator optimized for one speed efficiency. (no pumping loses. H@ll, make it a diesel!) and a large enough battery to get you 10-20 miles.

Already been done. One application I've seen uses a sub 2 litre 90hp diesel motor to run a full-sized bus. It runs steady while the bus stops and starts, with energy recovery as well. The question of this setup was how to analyse the maximum 'duty cycle' [acel-decel-stop-repeat] that the bus could go through that the 90hp motor could do the job and how to maximise efficiency whilst minimising engine load and wear-out issues that you get with running smaller motors flat out.

I never thought the idea was original to me. I just wondered why something so obvious wasn't more commonly tried. As for the motor wearing out, if it's a small motor, the rebuild costs are much cheaper than a full sized engine. Especially if it is simplified to just drive a generator.

You can also run non-otto cycles in the setup you're describing. The Atkinson cycle runs an over-stroked power phase. This is good for efficiency but bad for engine flexibility. But you don't need that flexibility if you're using it to generate power rather than pull away. The Prius uses an Atkinson cycle rather than Otto, I'm lead to believe, for much the same reason.

I love the Atkinson cycle,(or the easier to implement Miller cycle) and I have long wondered why other car companies haven't pursued it. It is another of those "no brainer" ideas that ought to be obvious, but for some reason isn't. So you lose a little power. Big deal ! Increase engine size to accommodate the power discrepancy and continue on. Heat engine design is one of my hobbies, and I've got one idea that I think will beat the Atkinson cycle, but for the quickest improvement in current engine design, the Miller cycle is the fastest and easiest modification to any engine to improve efficiency. (just change the cam shaft.)

A lot of people are unaware that when the exhaust valve opens on an engine, the pressure in the chamber is a substantial amount of pressure, and every exhaust from the cylinder throws away this unutilized energy!







The Atkinson or Miller cycle improves this situation by making the expansion volume greater than the compression volume, thereby extracting more energy from a given quantity of air/fuel.

A diesel version would be better still, though i've never heard of anyone doing this.

There does seem to be less-and-less that is new under the Sun. So long as we don't fall into the same trap as the Victorians (might as well close the patent office, all is now known) and keep fiddling with the ever diminuishing details then maybe there are a few doors still to discover.

Amen!


David

[TDPerk]

when the exhaust valve opens on an engine, the pressure in the chamber is a substantial amount of pressure, and every exhaust from the cylinder throws away this unutilized energy!

While I hope not to be pointlessly snarky, there's this thing, it's called a turbocharger.

To take that to an unworkable/uneconomic extreme, regard the Napier Nomad.

Yours, TDP, ml, msl, & pfpp

[chrismb]

A diesel version would be better still, though i've never heard of anyone doing this.

The issue with Atkinson is that if you try and drive it, it bogs down as the engine speed tries to pick up, as that extra energy being sucked out of the stroke can no longer go into driving the transient increase in BMEP in the induction stroke. It becomes somewhat "undriveable" - like trying to drive an engine that's running too rich/lean, you have to ease in the throttle real careful.

An otto diesel can already be built to do much the same as the Atkinson, because it already has such a high expansion ratio there's little left to be sucked out. As mentioned, using a variable geometry turocharger also sucks out the last few joules, to the benefit of improved volumetric efficiency at induction. There's no big benefit, given the driveability disadvantages.

My VAG 1896cc variable turbo was so efficient that you could drive it at 55mph, about 1750rpm, right on the BMEP max, and after driving for however-long, the rear exhaust pipe was still cool to the touch, virtually ambient. Carnot tells you that there's not much more to be got out of the process with that level of efficiency.

Current european diesels are up against the last few opportunities for efficiency saving in internal metal friction and oil viscosity. They're right up at close to 60% thermal efficiency these days. VAG had some difficulty pushing into the 150bhp range for these engines as the combustion temperatures were getting so hot that they were melting the piston crowns, this is how maxed-out the technology has got over here. the only practical ways to do this are to make smaller engines with fewer cylinders, and so some form of pull-off augmentation is going to be required - 'mild'-hybrid diesels with miniscule 3 cylinder engines will be able to drive full sized cars to 100mpg.

You're in for a fuel-economy shock over in the US once Federal standards give the right consumer environment for these things to become possible/more popular purchases, and as DPF kit gets perfected to satisfy the EPA. Even the latest big jaguar diesels can do over 55mpg.

[MSimon]

The reason the exhaust valve opens early is specific power. You throw away energy to get more cycles per second.

Of course you know that.

If the engine is designed for constant speed it can be optimized to throw away less energy. The other problem that ties into that is fixed valve timing. The difficulty with electrical valves is their power. Even that is getting technical solutions.

[MSimon]

The problem with greater fuel efficiency is that people drive more - actual total consumption stays constant or rises.

Jevons paradox.

[MSimon]

The difficulty for diesel fuel in America is that our current refineries are optimized for a certain mix of gasoline in the output.

If we go to an all diesel fleet you eventually lower the price of gasoline to sell it and you are back at the beginning.

And greenies are not allowing new refineries to be built.

[Roger]

And greenies are not allowing new refineries to be built.

Thats a Green Herring, , refinery capacity has kept pace just fine. Seriously, thats NIMBY.

[MSimon]

And greenies are not allowing new refineries to be built.

Thats a Green Herring, :-), refinery capacity has kept pace just fine. Seriously, thats NIMBY.

Well yes. As long as WTI and similar light crude is available in abundance we are fine.

However, it would help to get a new refinery or two built that could handle the heavier crudes or that were more oriented to diesel. Despite several oil companies that would like to build new capacity (good in case of storms or accidents) none has been authorized.

I believe we have only one refinery capable of processing (economically) heavy crude. I haven't kept up but last I heard it was owned by CITGO which is owned by Venezuela.

It is unwise to have so many eggs in so few baskets.

It is also unwise to have to run refineries at above 90% of capacity to keep up (the last demand peak). It reduces the margin for error. Murphy says there is always error. Right now with demand down we are running at 85% of capacity. Good for oil co. profits. Bad for system stability.

[ravingdave]

when the exhaust valve opens on an engine, the pressure in the chamber is a substantial amount of pressure, and every exhaust from the cylinder throws away this unutilized energy!

While I hope not to be pointlessly snarky, there's this thing, it's called a turbocharger.

To take that to an unworkable/uneconomic extreme, regard the Napier Nomad.

Yours, TDP, ml, msl, & pfpp

I think a turbo charger improves volumetric efficiency, but not thermal efficiency. To be honest, I never bothered to research it specifically. I do know that a turbo charger is often used to make a small engine produce the power of a much bigger engine, but If it's improving efficiency, it's only by allowing cars to use a smaller engine in the first place.

That being said, it appears to me that a turbo charger only works at all by taking advantage of that exhaust pressure that still has a lot of latent energy in it. From what i've read, the exhaust gas stream contains about 1/3rd of all of the energy released from burning the fuel in the first place. The Cooling system of the engine accounts for 1/3rd, and then the engine actually converts the remaining 1/3rd into mechanical energy WHEN it is operating at is maximum efficiency. Most engines are only converting 20% of the heat energy into mechanical energy most of the time.


David

[ravingdave]

A diesel version would be better still, though i've never heard of anyone doing this.

The issue with Atkinson is that if you try and drive it, it bogs down as the engine speed tries to pick up, as that extra energy being sucked out of the stroke can no longer go into driving the transient increase in BMEP in the induction stroke. It becomes somewhat "undriveable" - like trying to drive an engine that's running too rich/lean, you have to ease in the throttle real careful.

An otto diesel can already be built to do much the same as the Atkinson, because it already has such a high expansion ratio there's little left to be sucked out. As mentioned, using a variable geometry turocharger also sucks out the last few joules, to the benefit of improved volumetric efficiency at induction. There's no big benefit, given the driveability disadvantages.

My VAG 1896cc variable turbo was so efficient that you could drive it at 55mph, about 1750rpm, right on the BMEP max, and after driving for however-long, the rear exhaust pipe was still cool to the touch, virtually ambient. Carnot tells you that there's not much more to be got out of the process with that level of efficiency.

Current european diesels are up against the last few opportunities for efficiency saving in internal metal friction and oil viscosity. They're right up at close to 60% thermal efficiency these days. VAG had some difficulty pushing into the 150bhp range for these engines as the combustion temperatures were getting so hot that they were melting the piston crowns, this is how maxed-out the technology has got over here. the only practical ways to do this are to make smaller engines with fewer cylinders, and so some form of pull-off augmentation is going to be required - 'mild'-hybrid diesels with miniscule 3 cylinder engines will be able to drive full sized cars to 100mpg.

You're in for a fuel-economy shock over in the US once Federal standards give the right consumer environment for these things to become possible/more popular purchases, and as DPF kit gets perfected to satisfy the EPA. Even the latest big jaguar diesels can do over 55mpg.

I have no personal experience with an Atkinson (or Miller) cycle engine, and what I know of them is entirely theoretical. However if what you say is true, the problem still goes away when you simply drive a generator with it. Constant rpm, constant load, there won't be any issues of revving and derevving an engine