More Electric Car

More Electric Car
Summer 2007

The electric car is coming, now that the advanced lithium ion battery has provided the means of storing a useful amount of energy in a battery. When and how remain to be seen. I would like to add a few thoughts on the how.

First, a bit of review. I think there will be a market for three kinds of cars: all electric, plug in commuter, over the road.

The all electric will be of limited use, but I think useful enough to be there. It is especially attractive for retirement communities. These already sometimes use golf carts, which with their heavy lead acid batteries and open structure, are of very limited use. A small 2 or 3 place enclosed car, capable of a speed of about 30-45 mph, would be much better, and could be used in the quiet part of most any city, and practically all small towns. It could give old folks mobility without the trouble and expense of a regular car, and without the danger to others of some old codger driving a full fledged car with impaired sight and reflexes. A restricted license and restriction to quiet streets would be in order. They could probably reach most anywhere they needed to go, such as a grocery store, church, and the senior center, and they would never have to go to a filling station. Such cars should be simple, cheap, and dependable.

There should also be a market for certain other vehicles, such as an all electric riding lawn mower.

The plug in commuter will be very important because most driving is less than 50 miles and this could reduce our need for fuel to a small fraction of what it otherwise will be. Producing fuel is a bigger problem than putting energy on the grid. Grid energy can come from such renewable and non polluting sources as wind, geothermal, and solar. Whether or not you think there is an environmental problem, keep in mind the politicians act like they think so, so it is well to consider it. Such sources can also be cheaper in the long run and reduce our dependence on foreign oil.
There may be no need for an over the road type, as the plug in commuter can do what it can. However, there will be people not having access to an outlet, who really do not want to pay extra for things they will not use, so would want a car with a smaller battery and no charger.
The earliest electric cars will be ICE (internal combustion engine) hybrids, as the ICE is available and well developed. The serial hybrid is probably the best choice as it lends itself to the plug in design, and is simpler. In effect, you have an ICE - motor generator electric plant on board to keep it going beyond the charge in the battery. The motor part is to start the ICE, otherwise it is just an ICE driving a generator as needed.

The ICE will always be expensive and is limited in efficiency, although there is research into such things as a camless engine with variable valve timing that looks interesting. Nevertheless, expense, complexity (with lowered reliability), and pollution, provides pressure to get rid of the ICE. The obvious choice is a fuel cell, which would replace the ICE and the motor generator. Since they can be stamped out and have essentially no moving parts, they should become cheap. They should be reliable and just about never wear out. With higher efficiency and lower pollution, they are an obvious choice when available.

But what about fuel for the fuel cell? A little review is also in order here.

There are a number of fuel cells available, but the only one for cars is the proton exchange fuel cell. All the others use unpleasant temperatures and/or chemicals, and are best suited for large installations where a trained person is available to run it. The proton exchange fuel cell, by contrast, can be made in a range of sizes down to quite small, and being simple, can easily be operated on its own.

All it takes is a PEM (proton exchange membrane), which is a thin layer of plastic that allows protons (hydrogen ions (or nuclei)) to pass through, but block electrons, making them go around in the external circuit. There is a porous elctrode on each side of the membrane. Hydrogen makes its way through one electrode, giving up its electron to the elctrode, with the proton then passing through the membrane. At the other elecrode, oxygen from air flowing past, picks up electrons from the electrode and combines with the protons (hydrogen ions) coming through the membrane. The oxidation of hydrogen provides the energy, and since the electrons have to go around, they provide the electric current that is the desired end product.

That is about all there is to it, except that a catalyst must be added to get the reaction to go fast enough to get a usable current from a reasonable sized cell. That is a bit of a problem as it is usually platinum, which is rare and expensive, but it can be recycled as it currently is from catalytic converters on present day cars. Note there would be no catalytic converter, so the platinum now used would be available for the fuel cell, so it should be a wash. Also, recently, other catalysts using iron, cobalt, and nickel are showing promise, and they would be much less expensive.

The catch is that this only works with hydrogen. It works very well with hydrogen, but hydrogen is unique and nothing else can be used to replace it for a proton exchange fuel cell. You have to have hydrogen.

Hydrogen as a fuel is bad news. As a gas, even at high pressure, very little energy can be crammed into pressure bottles, giving a vehicle an unacceptably short range. This with the difficulty and downright danger of messing with high pressure when refueling makes gaseous hydrogen very unlikely to be an acceptable fuel. Liquid hydrogen would probably work for big trucks, which refuel only at a few places and use up their fuel so quickly there would be no venting problem, but for cars, it just wouldn't work to fool with a cryogenic liquid when refueling, then have most of it vent off as it evaporates upon warming up in even the best insulated tanks.
Not much point developing an infrastructure for trucks only and another for cars. Whatever cars use, trucks could use. I do not think we will ever see hydrogen distributed as a fuel for vehicles. Not within our lifetimes, if ever.

So what do we do about fuel? Current fuels can go through a "reformer", which is essentially a portable, on board, automatic chemical plant. It breaks down the fuel into hydrogen, which is sent to the fuel cell, and everything else, which goes out the exhaust pipe. The problem is that it is a complicated piece of machinery, just asking for a chance to cause trouble. Some of the reactions require careful control of conditions, such as temperature and pressure. Water is needed and can be a problem on start up on a cold day as ice just won't work. All of this stuff is much better left to a big chemical plant ran by trained people and with the means of closely controlling conditions. Besides, a reformer is likely to be just as polluting, or more so, than an ICE, and probably no more efficient.

Much, much better to prepare a simple fuel at a chemical plant or refinery, then distribute it to be used in vehicles, with as little as possible further chemistry.

I think the hands down choice for fuel will be methanol. Not ethanol, defintely not gasoline.
First consider gasoline. It has served us well and is an energetic fuel. By volumn, ethanol only has about 70% the energy of gasoline, and methanol only about 60%. This energy is readily available by oxidizing, burning it, but not so in a fuel cell. Most of the energy in gasoline is from the carbon, and that is useless in a proton exchange fuel cell. If you run gasoline through a reformer, you do not get much hydrogen, and you waste a lot of energy getting rid of all that carbon. A much better process would be to run it through a refinery where hydrogen could be added and it converted to methanol. Of course you could just convert the crude oil to methanol in the first place.

Ethanol is all the rage now. The president went to Brazil, among other things, to arrange for imports of ethanol to make up the additional we will need to meet the government's mandate to add 10% ethanol to all gasoline. Amazing, we are going to reduce our dependance upon foreign oil by increasing our dependance upon foreign ethanol! And at the same time, will have to put up with soaring food prices. I am amazed at how easy it is to sell snake oil when you have the national media and a bunch of environmentalists behind you.

Ethanol is not a bad fuel. It just needs to be produced from such things as switch grass or old newspapers, not corn. Corn prices have now doubled and are expected to go up another 50% this year. Soybean prices are up, as are cotton futures as land is switched to corn. Ethanol can be used in a number of ways as a fuel, but I think the best thing to do with it is to convert it to methanol. C2H5OH + H20 -> 2 CH3OH. I don't know exactly how to do this, but any competent chemical engineer can probably do it with reasonable ease. Note that it would remove the energy loss distilling the ethanol and the final processing to remove water. You would only have to get it to a certain concentration, then use the water already with it, and produce anhydrous (neat) methanol. No further removal of water needed.

Why go to methanol? Well, ethanol can be used directly in a fuel cell, but with the carbon-carbon bond and a larger molecule, the reaction is a lot trickier and harder to control. If you don't watch out you will get all sorts of things instead of hydrogen, and to get anything, you need a temperature above the boiling point of water. That is tricky when you are using a water solution of alcohol. In short, although it is possible to use ethanol in a fuel cell, I don't think you are going to want all the trouble it will take. Anything heavier than ethanol is out of the question.
Now methanol. Not as simple as hydrogen, but doable. Not only doable, quite practical. You will need a bit higher temperature than pure hydrogen, but only about that of an ICE. In other words, probably too hot to sit on it, but no problem. With methanol, you can use a cell that is little different than the basic proton exchange cell. About all that is needed to be different is to handle a liquid fuel instead of a gas, and probably to recirculate it. You also may need some controlling and measuring devices.

How it works is rather simple. In the presence of the same catalysts, one molecule of methanol and one of water, will react, forming cabon dioxide and hydrogen, right there at the membrane. The hydrogen passes on through as usual, and the carbon dioxide has to be removed. CH3OH + H2O -> CO2 + 3H2. There is no need for a reformer as, in effect, the reforming is done at the membrane. A similar reaction can occure with ethanol, but it takes three times as much water, a much higher temperature, and you are likely to get all sorts of things instead of hydrogen. With methanol, this one desired reaction is about all that can occur, so there is no problem controlling it, and the lower temperature is managable.

The CO2 is rather harmless, as long as the concentration does not get high, and can be vented without bothering with an exhaust pipe, and the rest you could breath, it just being slightly humid air, a bit short on oxygen like at a bit higher altitude.

There is a catch. Water is needed. Equal amounts (by mole, meaning same number of molecules). If only the carbon dioxide is allowed to leave, then you must have exactly the right amount of each, or eventually, the one present in the greater amount will accumulate in the cell and block the flow of fuel, requiring the excess to be bled off to get the cell going again. What would probably work better would be to recirculate a bit of fuel. As it comes out of the cell, the CO2 could be allowed to bubble out, then the concentration could be measured and adjusted before it goes back in. The exact proportion would not be important. This would also allow neat fuel (no water) in the tank, with fuel and water being added to the recirculating portion as needed to keep its concentration approximately what it needs to be.

Water in the fuel would be no problem, it would just take up space in the tank and you would not want to pay methanol price for water. Methanol does absorb water (as does ethanol) and the fuel system has to be able to handle water without corroding. In addition, methanol is death on aluminum as it reacts with the oxide that normally protects aluminum.

So where do you get the water! A separate tank for it would add weight, expense, and bother, and bear in mind it needs to be pure water, not tap water with calcium carbonate, chlorine, and who knows what else. It would probably be better to recover it from the air side of the cell. Bear in mind that the oxidation of hydrogen produces water, three times as much as needed with the methanol. One third of this could be recovered and added as needed to the recirculating portion. Note that there would not be a freezing problem in cold weather as the recirculating portion would be enough to get it up and running and the temperature up before more water needed to be recovered, and it would not freeze because of the methanol. Remember methanol was used as antifreeze for cars before ethylene glycol.

I am not sure what it would take to recover this water. Obviously, a chilled surface could do it. You can see water dripping out of tail pipes in cold weather before it gets warmed up. A thermocouple cooler should work fine and could even be reversed for cold weather start up to prevent frosting before the temperature gets up. Ample electricty for it would be available, and the total energy needed by it should not be too great. They are cheap and reliable with no moving parts. Perhaps simply bubling the exhaust through the recirculating solution would add water fast enough. This would be something for the engineers to tend to.

Methanol is currently produced in rather large amounts. The environmentalists do not like it because it is mainly produced from petroleum (the methane in natural gas) and therefore is nonrenewable and adds to CO2 in the atmosphere. However, it can be produced in large and even larger quantities and without disrupting our food supply. Since it can be produced from biomass, production could be switched over as it becomes available, but in the meantime, we could get what we need. If the methane hydrates ever are tapped, it would be a natural to convert that gas to a liquid fuel for distribution.

Methanol can also be produced from coal, by the familiar reaction of coke and water to form synthesis gas, which with some more hydrogen can react to form methanol. We have lots of coal, and modern plants can use it with little pollution. The sulfur now is usually utilized to form fertilizer, rather than being released to the atmosphere. Currently, it can be produced for about a half dollar a gallon.

This clearly beats gasoline, which ethanol cannot do without the subsidy paid out of our taxes. Note that with the lower energy content and allowing for taxes and a bit for retailing, it is probably close to $2 a gallon equivalent, but that still beats gasoline on the average. Electricity from the grid can be used to produce hydrogen from water and that can then be reacted with CO2 to form methanol, which not only produces a usuable fuel, it gets rid of some of the CO2 that some people worry so much about.

Lots of it is used to make other chemicals, but a good deal is used as fuel already, being burned. It is the main ingredient in the fuel for glow plug engines for model airplanes and is often used as a racing fuel, as is also ethanol, though ethanol is being reduced. It has the desired property of being a single compound so every tank is the same, while gasoline, being a blend, can and does vary quite a bit. It also burns without smoke, unlike gasoline, which often produces a lot a smoke. In case of a fire on the race track, there is not nearly so much smoke obscuring the view of drivers. Water does not mix with gasoline, and if applied to a fire will just push the flaming gasoline around. Water disolves readily in methanol and will put out the fire as the energy to boil the water cools it below the igniton temperature. These advantages would also be appreciated on the public roads.

I conclude: I think the electric cars will start out with an ICE - motor generator, then switch to a direct methanol fuel cell. Methanol will replace gasoline as transportation fuel.