09 April 2006

Trucks, trains and automobiles

In the last few years, we hear more and more talk about hydrogen and ethanol as fuel for the cars.
Those two fuels are cool, but the problem is, they do not really come from renewable sources.
Sure, the hydrogen can be extracted from the water, but it is inefficient, and it has to be compressed. It requires much more energy to make it usable in a car (that is, extract, compress and distribute it) than the energy used by the car. That energy, unless created by renewable sources, is energy wasted.

The ethanol has to be created from living organisms, which are also non renewable.
For example, the plants extract nutrients from the soil, which means that you can not plant them over and over again on the same spot, not at least without refertilizing the soil. In addition to that, plants do need to be taken care of (plantation, irrigation, harvesting), which makes them not really suitable for powering vehicles.

So long as the oil reserves do not run out, and the gas can be bought for a resonable price, I don't think there will be any major shift in the way we power our vehicles.
However, given the fact that the oil is finite and not really the most renewable thing in the world, I believe it is the time to focus on alternatives.

Electric powered cars are the future. They are quiet, efficient, and non polluting. They seem like the best choice, but for some reason they really not really used.
Why? Because for the time being the batteries have a few problems: They are heavy, expensive,
slow charging, and have a limited life span. The life span is different depending on the chemistry type.

For example, the lithium ion batteries have about 1K cycles (charge/discharge) but they do get damaged in time, even if not used. They are also not really happy about being exposed to heat, which is the major killer. If they are charged at about 40% and stored at 20C, their degradation is about 5%/year. However, under normal circumstances, they are exposed to higher temperatures, which considerably shortens their lives, so in 3 to 5 years their charge is drastically affected, to the point where they need to be changed.
On the plus side, they offer an excellent power density, and they are relatively enviromentally friendly.

The lead acid battery, present in most of the automobiles, is pretty cheap but it has quite a few cons:
It gets damaged if discharged under a certain voltage (about 10V for a 12V battery), which prevents using the full available power.
They are heavy and offer a poor energy density compared to the Lithium Ion type.
They contain lead, which, if not recycled properly, presents a big environmental problem.
High (or low) temperatures will considerably shorten their life span.

Two other chemestries are the NiCd and NiMh, which are, in terms of energy density,
in between the lead acid and lithium ion.
The NiCd has toxic materials, low energy density, and suffers from the memory effect, but it offers more cycles (sometimes more than 1K, if used properly).
The NiMh batteries have a higher energy density than the NiCd, are more environmentally friendly, their memory effect is less obvious than the NiCd type, but they have less cycles (about 300 to 500, depending on how they are used).
For more information about batteries, visit www.batteryuniversity.com, which is the site :)

As I've mentioned before, the reason electric power vehicles are not really used is because the batteries are expensive, they take a lot of time to charge, and the autonomy of the vehicle is relatively small (about 200 Km at most, but usually less than that). While the electricity is very cheap, compared to oil, the fact that you have to change your batteries every few years makes such vehicles inefficient, at least for the time being.

So, what is it to be done?
Some are focusing on fuel cells, which are some devices that can convert hydrogen (and sometimes alcohol) into electricity.
The problem with the fuel cells is that they have (at least for now) a limited life, they are expensive since they need platinum, and they still need hydrogen, which, as explained in the beginning of this post, it is not so efficient to extract, compress and distribute.

One technology is relativelyoverlooked, at least for the time being:
The capacitors (or, to be more precise, the super capacitors).
The super capacitors are a new technology, which allows REALLY high power densities compared to the traditional capacitors, but lower than the batteries.
For now, they are also pretty expensive. Other problems include that fact that they store a low voltage (about 2.5v), which means you have to connect them in series, which requires some additional circuits, in order to prevent them from getting damaged because of inequal charge.
One good thing about them: they can be charged really really fast, in a few minutes, rather than hours (which is typical for the batteries). They can not be overcharged, which is a another good thing, and they have a practically infinite number of cycles (more than 100K charge/discharge cycles).

A car powered by capacitors would have a limited autonomy, maybe 20-30 Km, possibly more as we develop more efficient motors, lighter materials and better capacitors.
This problem can be remedied in a simple way: On road charging stations.
For example, the roads would be equipped with some wires, so when a compatible car is over them, a dialogue is initiated between the card and the charging station. An RfID chip can send
the ID of the car to the charging station, which starts pumping electricity in it, counts how much electricity was pumped, then at the end of the month you get the bill in the mail.
For your convenience, those charging stations could be placed at busy intersections, so while you wait for the green signal, your car is automatically charged, without any intervention. A 30 seconds stop could charge your car for another few kilometers.
So no trips to gas stations, no hassle to distribute the fuel all over the nation, no environmental impact.
Sounds good, no?

As a possible improvement, solar panels can be placed on top of the car. A van type vehicle can accomodate perhaps 5 square meters of solar panels, and at an efficiency of 30% (achieved in the lab) that means about 1.5 kWh of power. Not bad at all.

Tomorrow I will demonstrate the solar powered/capacitor car, with pictures and everything (right now it is charging in my window) :)
It's pretty cheap to build, and you can make one in less than two hours, for 20 USD or less. The parts can be ordered online, and perhaps even found in local stores.


Blogger Donny said...

Sounds interesting, can't wait to see what it looks like and some more details, would be cool to see a car someday use capacitors which makes sense in all reality, and with some sort of battery/solar backup you would be set just in case if you run out of juice. Flip the little backup energy switch and off you go recharging the capacitors and driving.

I also like the idea of never having to goto the gas station that gets to be a pain heh, would make life so much easier just to sit at a light and your car would fill up. Would be really good for the environment too because you wouldn't need to dispose of anything except for the electric company's creating the power.

9/4/06 18:51  
Anonymous Anonymous said...

Trucks and the trains is the leading loading vehicle for the transportation and both are biggest part of the automobile industry.

12/1/09 06:34  

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