I just read that the Segway personal transporters are now available for sale, and their “fuel efficiency” is being touted because they run on batteries. Now obviously the battery power doesn’t come out of the clear blue sky; the batteries have to be charged using electricty from an outlet, and of course the manufacturing process to produce the batteries expends fuel in yet another way. This leads to my question, and I appreciate any attempt to answer it, even in a general way, since I know it is not an easy question to answer: how efficient is a battery powered device such as the Segway compared to a similar, conventional fuel-powered device, such as those gasoline powered skateboards you might have seen? If all the cars in the world were magically converted to rechargeable battery power overnight, what would be the effect of this on our environment? Would the additional electrical energy that would have to be produced through coal-powered plants and the like negate the reduction in pollution currently produced by automobiles? Is this a Great Debate (he humbly asked) ?
Fuel efficienty may be a poor choice of words but even more so it has no context. Let’s replace the word fuel with energy and look at it again. Okay, the Segway is energy efficient. Compared to what? To an electric car? A bicycle? An electric scooter? A 747? Need some criteria to make a valid claim. If you only base efficiency on meters per joule it’s probably pretty darn good. If you factor speed and protection from elements it gets more complex.
I don’t need a cite to be convinced that the Segway is more “energy efficient” than, for example, an SUV, for the tasks for which it is designed – that is, to transfer a single person short distances.
Whether it is more “energy efficient” than, say, a Vespa, is another question – I would guess that it would be similarly efficient, and less polluting to the atmosphere than the typical small internal combustion engine powered vehicle.
The root of the issue here is the fact that the Segway gets its power from an existing power supply. The marginal cost (in fuel and environmental damage) of a large powerplant to generate enough additional power to charge the Segway’s batteries is less than the cost (in terms of transfering the energy within the fuel to the energy that powers the scooter; and also in terms of environmental damage) than a scooter with its own engine.
The general rule in power/energy distribution is that for a given amount of energy delivered. “One big one can be made more efficient than a lot of little ones.”
HOWEVER - in the case cited of switching all the cars over to electricity, we have a change in the method of power generation; from a lot of small gas-powered engines to a few large coal-fired generators. So, what we really need is Someone Who Knows about the relative merits of coal-fired vs gasoline engines. Also, I don’t think the OP addressed it, but pollution should be considered.
A battery does not constitute a “fuel.” A battery is simply an energy storage mechanism.
The actual “fuel” your Segway uses depends on the fuel your power plant uses. If your power plant burns coal, you have a coal-powered Segway. If your power plant burns gas, you have a gas-powered Segway. If your power plant is nuclear, you have a nuclear-powered Segway. And so on. (Suffice to say, it is impossible for any device to be “battery powered.”)
Another thing you can talk about is energy density. Compared to gasoline, batteries have terrible energy density numbers, which makes them impractical for automobile use.
It will be a Great Debate if we can’t keep the anti-SUV and anti-electric car crowds from crashing together.
To rephrase the question: Assuming that your power plant uses a gasoline powered generator, does using a battery powered electric motor use less fuel than putting a comparable gasoline motor on it?
The general rule among motors/generators is that you can make big ones more efficiently. So, I can get more joules/gallon at the plant than I can from the proposed small motor.
But that is not the whole story. Once you calculate how much energy you lose transmitting the electricity from the plant, the benefit is not as great.
Thus:
Electric Segway Joules/gallon = Power Plant Joules/gallon - transmission losses
Is that number bigger or smaller than Gasoline Segway Joules/gallon?
For electric cars, the answer is “slightly bigger”.* I assume that the Gasoline Segway would be less efficient (joules/gallon) than a car engine, and so in this case the answer would be “noticeably bigger”.
You can complicate the issue by asking how much extra gas did it take to get the gallon of gas to your house to pour into the Segway, but that is harder to get good numbers for.
Further complications can be added by looking at pollution factors, noise factors, torque profiles and energy use at idle… but that way lies Great Debates.
FIVE THOUSAND DOLLARS FOR A SCOOTER???
Sorry, someone had to be the first to say it.
**not an expert on electrical power but…
I was at a United States Post Office Distribution Center last week where all the 16 internal parcel service workers were on Segway Scooters. One gentleman said, " I love this thing, we had a short workshop on how to use it and then we were off. I charge it at the end of every shift. And I don’t lose power at all, all day long."
Apparently there are uses for these infernal electrical beasts…
keeper0: I think this is what you’re asking: “Is it more efficient to generate electricity at a power plant, distribute the power to your house, and then charge a battery in an electric vehicle, or is it more efficient to simply use an internal combustion engine?”
Answer: I don’t know. I’ve never bothered to do the math.
But here’s what I do know: When it comes to the “electric vs. gas vehicle” debate, I do not believe the critical issue is “overall conversion efficiency.” Instead I think on-board energy density is much more important.
Let’s assume for the sake of argument that an electric vehicle is more efficient, joule-per-joule, than a comparable vehicle w/ internal combustion engine. So what? An electric car is still lousy because you can only travel a couple hundred miles between chargings. And you really suck the battery dry if you dare turn the heat on. This is because the energy density of batteries doesn’t come anywhere close to the energy density of gasoline. That’s the real problem, not conversion efficiency.
Invent an clean energy storage mechanism that has decent on-board energy density, and you’ll be a winner.
You sir have hit the nail on the head.
The other problem with any type of EV is that when you run out of juice you can’t call the auto club to bring you out a bucket of electrons 
Right, but the fuel for the scooter is electricity. A battery is more like the gas tank, it stores the fuel.
CrafterMan, your entire argument is flawed. A scooter runs on electricity, not the gas consumed by the power plant. Using that logic, your gas car is really fueled by crude oil underground, and not to mention the refinery workers meals.
Don’t bogart it, dude!
Listen, electricity is NOT a fuel. Which school taught you that? My Og.
b.
Sorry but you’re incorrect. Do you even know what a fuel is?
For the record, electricity is not a fuel. It is an energy transfer/storage medium. Other things that are not fuels include electrochemical batteries, alcohol, solar panels, and “fuel” cells.
Quiz time: Let’s say I have a solar-powered car. What’s the fuel source? Hint: It ain’t the sun.
There are a few reasons why electric vehicles tend to be more efficient:
- Electric motors develop maximum torque at 0 RPM. Gas engines have to be revved up to develop torque. In stop and go traffic, having that engine running at relatively high rpm is wasteful.
2)Regenerative braking. A gasoline powered car uses fuel to get you up to speed, but sheds it as heat through the brakes to stop you. Electric vehicles turn their motors into generators and absorb the energy of braking back into the batteries.
3)No requirement to idle. Cars sitting at a light burn gas. A Segway sitting at a light doesn’t use up battery power.
If you want to see a direct comparison of efficiency, have a look at the difference between the Ford Escape and the Escape Hybrid. They have very similar performance, and both have gas engines. But the hybrid uses electric power and regenerative braking. The hybrid gets about 40mpg, vs something like 27 for the regular Escape.
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- Segways are horribly overpriced; there’s simply nothing technically expensive involved in making them. They are an electric scooter, nothing more. If you don’t want an electric scooter now, you probably won’t want a Segway for the same reasons.
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- Personally, I think they'll be declared kids' toys eventually. Where I live kids can't rollerskate, skateboard or ride bicycles on city sidewalks because of people getting run over and complaining like heck. How long will it take Dean Karmen to get sued for liability?
- If you're going to be lazy, no sense in overpaying for it, I say: get an electric wheelchair instead, it'll have a sling for your butt and even less effort involved in them, and in the US every public form of transportation and public building *is already required by law* to accommodate you.
~They have a whole heck of a lot of expensive computer hardware and gyroscopes in them to keep themselves ballanced. Plus they were engineered to medical equipment saftey and reliability standards. Add in a big lithium battery and the price ramps up pretty quickly. Hopefully, mass production (if they ever catch on) along with Moore’s law will bring the price down to more reasonable levels in the next few years.
Don’t go overboard, Crafter_Man. No one is suggesting that solar panels are an energy source or a fuel. Stop setting up straw men and then acting all smart arse by knocking them down.
Strictly speaking a fuel is a substance for burning, according to the OED. So alcohol is certainly a fuel, as is petroleum. Why on earth you would think alchohol is not a fuel I do not know.
The answer to the OP is contained in keeper0’s cite.
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- Slashdot had a story a while back about a guy who built a miniature version of a two-wheeled balancing vehicle out of Lego Mindstorms parts.
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- Slashdot had a story a while back about a guy who built a miniature version of a two-wheeled balancing vehicle out of Lego Mindstorms parts.
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Was it robust enough and reliable enough that it could be sold as a consumer product? There’s an enormous difference between a technology demonstration and a viable product.