Last week I attended an interesting presentation at the California Fuel Cell Partnership located near Sacramento. I have been aware of this organization for a decade or so, but this was my first visit.
The showroom contains some very impressive looking fuel cells on shelves and installed in a cut-away automobile. I worked in the fuel cell industry more than a dozen years ago and was very impressed by the obvious advances in technologies and workmanship in the ensuing years. They have moved from "experimental" devices to high tech, high quality products.
When I refer to fuel cells I am talking about one specific type of device that combines gaseous hydrogen with oxygen to produce electricity and water at temperatures close to room temperature. In the simplest description, these devices consist of two chambers separated by a membrane. One chamber contains gaseous hydrogen, the other contains oxygen (or air in most cases). The membrane is called a PEM (Proton Exchange Membrane) (sometimes called the polymer electrolyte membrane). These are just two names for the same thing. The last time I actually saw some of this membrane it looked like thin Suranwrap. The finish device is sometimes called a PEMFC (PEM Fuel Cell).
The PEM is the heart of the system. It contains molecules (often platinum) that act as a catalyst to break the hydrogen molecule (H2) into two hydrogen ions (+charge) and two electrons (- charge). The hydrogen ions are small enough to migrate through the PEM to the other side containing oxygen molecules (O2). The PEM blocks hydrogen, but allows the flow of hydrogen ions. The hydrogen and oxygen are anxious to join and form water, but they are missing the two electrons. The two electrons get there through a wire, creating the electricity that powers the devices that are in the circuit. Typically, the hydrogen is supplied by a pressurized (10,000 psi) storage tank of hydrogen. The oxygen is often supplied by a stream of fresh air flowing through an open chamber. The existing stream of air carries off the water molecules. Hydrogen is depressurized, then piped to one side while flowing air passes across the other side of the PEM, producing abundant amounts of electricity. All of this happens at relatively low temperatures. The temperatures are maintained close to 100C (212F) so that the water turns to steam and doesn't clog up the system with liquid water.
There are very few moving parts in this device. The hydrogen flows just enough to give up the electrons required to supply the desired amount of electricity. The air needs to be pumped, or blown, through the air side of the chambers. That is about it. It just sits there and works - almost as passive as PV solar panels. Of course there are a lot more things involved in the way of sensors, valves and safety devices - but it still turns out to be quite simple in comparison to something such as an internal engine.
For many years there were giant roadblocks due to patent problems that resulted in stifling the ability to turn the idea into a viable product. Foremost among the barriers were the patents on the PEM material. Instead of being the pennies per square foot that is paid by the oil companies for use in their refineries, it cost hundreds of dollars a square foot for fuel cell applications. Apparently many of these barriers have recently been removed and the quality of the membrane has been significantly improved. The presenter said that many companies have opened their patents so that they can be freely used without royalties or restrictions. They did this because it became clear that the industry would never grow as long as the patents were in place blocking integration of the various parts into a working system.
today there are about two dozen automakers worldwide that are actively pursuing the fuel cell market. Many of these companies have mature, fully tested, vehicles on the roads. Apparently there are currently about 300 of these vehicles in California. An oft-cited observation is that they aren't an important technology because there are so few of them. Of course, when the first shoe sized cell-phones came out the phone companies said they weren't a concern because they had such a tiny share of the market. Obviously this situation of being a tiny slice of the market can change quite rapidly given proper market forces.
One problem with their widespread introduction is the current lack of fueling stations. Studies have determined that 100 strategically placed filling stations in California should be enough to push the technology "over the top" for everyday use in that State. Currently there are 68 of these stations completed or in construction. The plan is to complete the full complement of 100 by the end of the year. At that point, most customers will be within acceptable distances to a filling station. California will then have the hydrogen filling infrastructure to support a fuel cell vehicle fleet, possibly jump-starting other States to follow suit.
The current range and filling times are impressive. Automobiles get a range of 300-500 miles between fill-ups, and it only takes three minutes to fill the tanks. The volume of hydrogen to achieve this range is about 1/3 of the volume of gasoline to do the same. That is comparable to current gasoline vehicles, and MUCH better than electrical vehicles. It is even better than Tesla's super chargers located along major interstate highways that charge a car in about 20 minutes.
All this sounds promising, but there is still the question of where does the hydrogen come from? This is a similar problem to that faced by the electric car industry. One obvious answer is to make hydrogen using solar produced electricity to break water into hydrogen and oxygen (hydrolysis). I suspect that this will be a long term answer, with the bulk of the hydrogen being produced locally by distributed ("roof top") solar installations on homes, building, parking lots and shade structures. However, that is not likely to be short term solution because it requires additional infrastructure to be in place first. It is a bit of the old chicken and egg problem. You need the one before the second, but the second before first. A second problem with producing hydrogen from water is that it requires about one gallon of water to travel 70 miles (as compared to requiring about 2 gallons of water to produce one gallon of gasoline). While the water use is much less than for other fuels, it is still a lot if the entire fleet were to be powered by hydrogen. Solving the water use problem is needed. I wonder why the water can't be condensed from the exhaust and re-used. It is pure water at that point. I think some simple and effective solutions will be found to solve this issue. (For example: The air from the cell will be saturated, 100C air. Cooling that to 50C or less will cause the vast majority of the water to condense. Since this device will be used in a moving vehicle, a source of relatively cool air will be usually be available to achieve this temperature change - solving most of the water use problem when the less than five gallons of water is discharged at the filling station.)
The obvious interim solution will likely be creating hydrogen from natural gas - a well known and common process. In addition to that source of hydrogen, there is a growing number of facilities that produce hydrogen from agricultural products and waste materials such as waste food.
It appears that we might be on the verge of a hydrogen economy. Currently, the main application for this technology is powering leased vehicles (terms are about $600/month - but include free hydrogen). There are also PEMFC cells used to power portable light stands used in highway construction and to provide lighting for large events because they are quiet, non-toxic and portable. Some of the large package delivery services that use all electric vehicles are adding fuel cells to achieve longer range operations, an electric - fuel cell hybrid.
I found this to be a pretty exciting turn of events. It has always been clear that battery technologies are an interim step to moving toward an all electric fuel economy. They are heavy, expensive, contain hazardous materials, contain huge amounts of stored electrical energy and have a relative short life before needing to be replaced. PECFC's avoid all of these problems (turning off the hydrogen will automatically eliminate electrical power). Not only that, but as far as I have been able to determine after studying them for many years as a system safety engineer, hydrogen fuel cell vehicles are far safer than all-electric, hybrid or pure gasoline or diesel vehicles. A caveat to this statement is that for vehicle use, there will likely always be a hydrogen-battery hybrid configuration that allows for recouping energy through regenerative breaking. This results in a high voltage battery pack that has all of the hazards associated with an all electric, battery powered vehicle.
I find one of the most interesting parts of this move toward a hydrogen fuel cells energy economy is that it opens up to the possibility of using a very wide range of "primary" energy sources to produce the needed hydrogen, and it provides the possibility for long term, portable/transportable storage of fuel that is not achievable with battery storage. One of the prime advantages of liquid fuels (oil, gasoline, etc), is that it can be stored and transported - and that it has an energy density high enough to be used in large moving vehicles such as automobiles and trucks. It is turning out that hydrogen storage for applications such as trucks and automobiles uses less space, and is significantly lighter than that required for a comparable range using gasoline or diesel. One application that is unlikely to be involved with fuel cell technologies is for powering airliners because they get their thrust in a large part by expelling high velocity mass from the burning fuel, they are not just giant fans in the sky.
Once again, when considering whether or not we have the technology to implement vast improvements to the environment through a reduction in pollution and green house gases, the answer to "are we there yet?" is - "look out the window, we are there - are we willing to make use of it?"
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