Disadvantages of Hydrogen Fuel Cells

Hydrogen fuel cells are the wave of the future. At least that is what many would want you to believe. They have a point because a hydrogen fuel cell is a novel way to power a car. The car would require no gasoline, run on hydrogen and its only waste would be water, a natural and safe emission. However, it is not a perfect science by any means and too many times there is talk about all the great advantages without any discussion of the disadvantages of hydrogen fuel cells.

With anything, there is going to be drawbacks. If it were such a perfect technology, don't you think every car would have one by now? Besides being expensive, the hydrogen fuel cell creates certain problems that haven't been completely tackled yet.

Here are the three main disadvantages of hydrogen fuel cells:

1. It's big and cumbersome. Your gas tank already uses a nice portion of your car, but a hydrogen fuel cell will be three times bigger than a gas tank. But that is not that all. The fuel cell has to be insulated to keep it safe and protected.

2. Safety issues. Liquid hydrogen has the ability to freeze air. There have also been reports of accidents with the fuel cell itself. Sometimes a valve will get plugged up when there is too much pressure in the cell. The only place to go is out, and the cell explodes. There is no way of knowing, yet, if this problem can be fixed, but there are many working on it. In a car accident, the tank might rupture, but the good news is the hydrogen will evaporate quickly. However, it is a more serious condition in a closed area such as a garage.

3. The hydrogen evaporates. Strange, but true. The insulation is not a perfect process and the hydrogen evaporates out of the cell at roughly 1.7 percent a day. This means that eventually cars are going to need a fill up. What? You thought you never had to use a pump again? The other problem with this is gas stations don't sell hydrogen. You will have to find a customized fueling station or work something out with the manufacturer of the car. Cars that are blends with fuel cells and gasoline will never have to worry about being stranded.

General Motors Co., currently has the Chevy Equinox Fuel Cell, one of the first fuel cell vehicles of its kind. If you are thinking about purchasing a vehicle of this type, speak to the manufacturer of the disadvantages of hydrogen fuel cells. By having the technology, they are aware of the pitfalls of hydrogen fuel cells and have begun work on how to make it better.

The good news is that automobile companies are working at ways to make this a safer environment by creating less emissions and the more we learn about alternative methods, the better the Earth will be for it. Just don't go blindly in one direction without asking questions. Learn about the disadvantages of hydrogen fuel cells before you agree to use it.

How Hydrogen Engine Work

As gasoline and diesel prices at the pump continue to soar, automobile manufacturers are working tirelessly to produce vehicles that are capable of utilizing alternative fuel sources for power. One such alternative is hydrogen powered vehicles.

Although very few hydrogen powered vehicles are currently available, many car companies have plans to release them in the very near future. With the prospect of creating higher fuel efficiency and thus realizing consumer savings, it is interesting to understand how hydrogen cars operate and will be a viable option in the future.

Hydrogen engines depend upon a chemical reaction to create power to operate a vehicle. It's actually a very simple process - what happens when two particles of hydrogen combine with one particle of oxygen? H20 equals water! In fact, in a hydrogen engine, hydrogen and air are continuously fed through, combining to produce both the electricity necessary to propel a vehicle as well as the water that will be the vehicle's emission.

So in addition to hydrogen becoming an alternative fuel source, it also helps avoid dependence on fossil fuels, it is also a clean fuel source, where the emission is simply water instead of the far more harmful carbon dioxide produced by gasoline or diesel engines. Hydrogen technology so far is advancing at a much slower rate than ethanol, electric and natural gas engines but still has a very good outlook as a viable power source for the future.

Hydrogen Cars vs Electric Cars

With gas prices being so high, alternative fuel vehicles have become a popular topic. Two of the types of vehicles that tend to get a lot of press are the hydrogen fuel cell powered vehicles and electric powered vehicles. Both are lauded as the way of the future

But which of these two options are really has the better chance of being the car your children drive.

Let’s look at hydrogen fuel cells first. When burned in an engine, the only emissions giving off is water, so a hydrogen powered vehicle is a zero emission vehicle. Hydrogen is also a better fuel than gasoline, it actually has the highest energy content per unit of weight of any known fuel.

Hydrogen is also a very abundant element. While current methods for making hydrogen are done by using fossil fuels, such as natural gas, coal, and oil, American wouldn’t be dependent on foreign oil anymore. Also, hydrogen can be extracted from water, and we all know there’s a lot of water on this planet.

However, hydrogen is not without its share of drawbacks. Probably the biggest problem right now is that it would require an entire new infrastructure. While gas stations could be outfitted with hydrogen fueling stations that would take years. Also, the technology to store hydrogen efficiently is still not ready for prime time.

Then there’s the electric car. Electric cars can also be considered zero emission vehicles since they give off no emission when running. However, electric cars do require power from the electric grid, which does give off emissions. As the electric grid gets cleaner, though, so do electric cars, and electric powered cars are substantially less polluting than gasoline powered cars due to the fact that power plants are far cleaner and more efficient than an internal combustion engine in a vehicle.

The technology for mainstream electric cars is also not quite ready for all the major manufacturers to stop making gasoline powered cars, but it’s much closer than hydrogen currently is. The challenge with electric cars right now is the batteries. The batteries are both expensive and current models, like the Tesla Roadster, have a range of only 250 miles – great for commuting, but not so good for road trips. The other problem is the length of time these vehicles take to charge. It’s not simply a matter stopping at your local power station and plugging in for five minutes and leaving. A typical charging cycle for current prototypes is 4-5 hours – again, fine if you’re commuting, but impossible for a road trip. While technology is being developed to make charging your vehicle as quick as quick as filling up with gas, it has a ways to go before it’s ready, just like hydrogen fuel cells.

Fleets of electric cars will certainly be hitting the roads sooner hydrogen fuel cell cars, but which one ultimately ends up being the vehicle of choice for drivers remains to be seen as both have plenty of challenges to overcome before people will readily give up their cheap gas powered cars in favor of these alternatives.

Hydrogen Effects on ICE Components

Internal combustion engines (ICEs) offer an efficient, clean, cost-effective option for converting the chemical energy of hydrogen into mechanical energy. The basics of this technology exist today and could greatly accelerate the utilization of hydrogen for transportation.

It is conceivable that ICE could be used in the long term as well as a transition to fuel cells. However, little is known about the durability of an ICE burning hydrogen. The primary components that will be exposed to hydrogen and that could be affected by this exposure in an ICE are (1) fuel injectors, (2) valves and valve seats, (3) pistons, (4) rings, and (5) cylinder walls. A primary combustion product will be water vapor, and that could be an issue for aluminum pistons, but is not expected to be an issue for the exhaust system except for corrosion.

There is clear evidence that the components of an engine burning hydrogen could experience durability issues because of their exposure to hydrogen or its primary combustion product, water vapor. High-efficiency conversion of hydrogen to mechanical energy will require the use of direct injection of hydrogen. This requires the injectors to be exposed to hydrogen gas, where the tool steel or carbon steel components could experience hydrogen-induced cracking or embrittlement. This is especially a concern for the injector needle and seat, which will also experience impact and cyclic loading.

Piezoelectric actuators are one method for providing the fuel injector needle its lift, and there is some evidence that hydrogen could affect the performance of these components. Hydrogen could affect the dielectric properties of the piezoelectric material, the epoxy in which it is encased, or the electrical contacts. Testing is in progress on these components that should provide the data needed on their performance and methods for improving their durability should that be necessary.

Valves and valve seats will be exposed to hydrogen at elevated temperatures and could experience decarburization; however, it is difficult to predict their behavior based on current information. The operating temperatures of exhaust valves and valve seats for gasoline ICEs are at or below that at which decarburization occurs in carbon steels, but they are generally made from alloy steels that have higher decarburization temperatures.

Also, the operating temperature of a hydrogen ICE may differ from a gasoline ICE. Gasoline ICEs utilize aluminum pistons, and it is known that aluminum and aluminum alloys experience hydrogen embrittlement when exposed to water vapor at 70°C and above. This operating temperature is certainly within the range of engine operation, so that it is important that this issue be evaluated.

Definition of Photoelectrolysis

Electrolysis is a process of detaching or dissociating bonded elements and compounds by passing through them an electric current. Water electrolysis decomposes H2O into hydrogen and oxygen gas. Care must be taken in choosing the correct electrolytes, nominally substances that contain free ions and hence behave as an electrically conductive medium.

Electrolytes dissolve and dissociate into cations (positive ions, +) and anions (negative ions, −) that carry the current. Such processes can occur in an electrolysis cell, or electrolyzer, which consists of two electrodes, cathode and anode, where reduction and oxidation reactions simultaneously take place forming H2 (at the cathode) and O2 (at the anode). The fundamental problem in hydrogen production by water electrolysis is that today the electricity used to drive the process is primarily generated by the burning of fossil fuels.

Photoelectrolysis describes electrolysis by the direct use of light; that is to say, the conversion of light into electrical current and then the transformation of a chemical entity (H2O, H2S, etc.) into useful chemical energy (such as H2) using that current. A photoelectrochemical cell is used to carry out the various photoelectrolytic reactions, being comprised of a semiconductor device that absorbs solar energy and generates the necessary voltage to split water molecules.

Photoelectrolysis integrates solar energy collection and water electrolysis into a single photoelectrode, and is considered the most efficient renewable method of hydrogen production. Our interest in hydrogen stems from it being an energy source that, like fossil fuels, are energy dense and can be readily transported and stored, but unlike fossil fuels is not of finite supply and its combustion does not result in pollution nor the release of climate altering gases.

Fiber Optic Hydrogen Sensor (FOHS)

The ability to detect hydrogen gas leaks economically and with inherent safety is an important technology that could facilitate commercial acceptance of hydrogen fuel in various applications. In particular, hydrogen fueled passenger vehicles will require leak detectors to signal the action of various safety devices. Such detectors will be required in various locations within a vehicle, wherever a leak could pose a safety hazard. It is therefore important that the detectors be very economical. For purposes of early detection a fast response time (<–1 second) is also desired. An optical fiber coated with a thin film of a chemochromic (color change induced by a chemical reaction) material offers the possibility of meeting these objectives.

Chemochromic materials such as tungsten oxide and certain lanthanide hydrides can react reversibly with hydrogen in air while showing significant changes in their optical properties. Thin films of these materials applied to the end of an optical fiber have been used as sensors to detect low concentrations of hydrogen in air. The coatings include a thin layer of gold in which a surface plasmon is generated, a thin film of the chemochromic material and a catalytic layer of palladiumthat facilitates the reaction with hydrogen. The gold thickness is chosen to produce a guided surface plasmon wave between the gold and the chemochromic material.

A dichroic beam splitter separates the reflected spectrum into a portion near the resonance and a portion away from the resonance and directs the portions to two separate photodiodes. The electronic ratio of these two signals cancels most of the fiber transmission noise and provides a stable hydrogen signal.

A fiber optic sensor based on the palladium catalyzed reaction of amorphous tungsten oxide and hydrogen was first proposed by Ito (1984). This simple sensor design was found to be adequate in terms of sensitivity but too slow in response time for the intended use. A different design using a surface plasmon resonance (SPR) configuration was therefore investigated. The SPR shifts in response to subtle changes in the refractive index of the coating. This shift can be monitored to give a faster response.

Technology for Hydrogen Sensors

Hydrogen may be emerging as the fuel of choice for an energy carrier. It can be stored, handled, reacted or combusted to deliver large quantities of energy to an end use safely, conveniently, and efficiently with very little environmental impact. However, it is a combustible gas, and the public has been sensitized to dangers associated with its use.

Safe practices and codes for handling hydrogen will require convenient and reliable methods of detecting hydrogen leaks in spaces where combustible or explosive concentrations may be reached. The U. S. Department of Energy has undertaken many of the long-range tasks associated with bringing a new energy carrier into widespread use and has initiated study of new sensor technology that will meet the requirements imposed by new technology.

Expanded use of hydrogen in the public domain brings new requirements for safety monitoring, which have not been considered until recently. For instance, the use of hydrogen for a transportation fuel will necessitate the outfitting of each vehicle and each fueling area with multiple sensors to detect low concentrations of hydrogen and to initiate a set of hierarchical actions such as setting off alarms, activating fans, etc. prior to the onset of the explosive limit.

The sensors must be rugged, reliable, and inexpensive enough to incorporate several into each vehicle. Additionally, the sensors need to be lightweight and have minimal energy requirements themselves. In order to meet such challenges, solid-state hydrogen sensors was designed. The technologies are based upon either chemochromic or resistance changes in the properties of thin films in the presence of hydrogen.

The Fiber Optic (chemochromic) sensor requires no electrical power at the sensing point and is ideal for high electromagnetic environments. Furthermore, a modification of the fiber optic sensor has shown promise as an analytical tool for measurement of diffusible hydrogen in welded steel. The thick film (resistive) sensor is versatile and can operate from a small battery. Data from combinations of multiple sensors can be fed into a central processing unit via fiber optics or telemetry to provide hydrogen situational awareness for small and large areas.