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.

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.

Hydrogen Accident & Safety

In the previous decades, severe accidents have happened involving hydrogen utilized in industrial and other applications. One of them is Hindenburg accident (1937). The accident occurred at Lakehurst, New Jersey, on May 6, 1937 and was for many years under investigation to identify the reasons that caused the ignition of the hydrogen gas used for buoyancy of the giant airship “Hindenburg”.

In that accident, the ignition of hydrogen proceeded rapidly to fire toward the tail section of the craft. The fire was almost simultaneously succeeded by an explosion that engulfed the 240 t craft causing it to crash onto the ground killing 36 people. The overall results indicated that the outer shell and the paint of the airship were flammable and could be ignited from electrical sparks. Indeed, prevailing atmospheric conditions at the time the accident occurred could generate considerable electrostatic discharge activity on the airship.

Today, the memory of the Hindenburg accident is fading, and as the safety record of hydrogen—based on its safe use in space exploration and in industry—becomes more widely known, it is also becoming accepted as a safe means of storing chemical energy.

This trend has been further encouraged by the lessons learned from accidents, such as the one that occurred in 2008 on Interstate 84 in Connecticut, where a trailer truck carrying hydrogen plunged down the embankment. If the truck had carried gasoline, we know what would have happened—a huge fireball. However, because hydrogen does not form pools on the ground, but rather escapes into the atmosphere, there was no fire and no injuries were caused by the hydrogen. Nevertheless, the wide use of hydrogen as an energy carrier will result in its use by laypersons necessitating different safety regulations and technologies that are now under development.

One of the major issues affecting the acceptance of hydrogen for public use is the safety of hydrogen installations (production and storage units) as well as its applications (i.e., as vehicle fuel or home use). The hazards associated with the use of hydrogen can be characterized as physiological (frostbite and asphyxiation), physical (embrittlement and component failures), and chemical (burning or explosion), the primary hazard being inadvertently producing a flammable or explosive mixture with air

From the safety point of view, the following are the most important properties of hydrogen when compared to other conventional fuels: When released, hydrogen quickly diffuses (3.8 times faster than natural gas) into a non-flammable concentration. It also rises 6 times faster than natural gas at a speed of almost 45 mph (20m/s). When it burns, due to the absence

of carbon and the presence of heat absorbing water vapor, the fire produces much less radiant heat than a hydrocarbon fire. This reduces the risk of secondary fires. If only hydrogen is present, an explosion cannot occur. An oxidizer, such as oxygen, must be present in a concentration of at least 10% pure oxygen or 41% air. Hydrogen can be explosive at concentrations of 18.3% to 59% while gasoline can present a more dangerous potential, because it can explode at much lower concentrations, 1.1% to 3.3%.