Types of Alternative Fuel – Hydrogen

One of the most interesting and promising, alternative transportation fuels is hydrogen. While mostly only experimental vehicles are operating on this fuel now, the potential for this unique energy source is excellent.

Anyone who has taken a chemistry class knows that hydrogen is number one on the periodic chart of elements and the lightest of all elements. It is easy to produce through electrolysis, simply splitting water (H20) into oxygen and hydrogen by using electricity. However, these days, nearly all hydrogen is made from natural gas.

Because hydrogen burns nearly pollution-free, it has been looked at as the ultimate clean fuel. When burned, it turns into heat and water vapor. When burned in an internal combustion engine (the kind of engine in gasoline cars today), the combustion also produces small amounts of other gases.

These other gases are mostly oxides of nitrogen because the hydrogen is being burned with air, which is about two-thirds nitrogen. Being a non-carbon fuel, the exhaust is free of carbon dioxide. Carbon dioxide, emitted from our burning of fossil fuels, is causing the world’s climate to change.

Hydrogen is normally a gas and can be compressed and stored in cylinders. The main problem with hydrogen is bulk of the cylinders or fuel tanks. Compressed hydrogen contains less energy per volume compared to liquid fuels like gasoline or ethanol. Hydrogen can also be cooled to produce liquid hydrogen, but it is costly.

Hydrogen’s clean burning characteristics may, one day, make it a popular transportation fuel. For now, the problem of how to store enough hydrogen on a vehicle for a reasonable range, and its high cost, compared to gasoline, are critical barriers to widespread commercial use. Nearly all hydrogen currently is made from natural gas. For that reason, hydrogen usually costs more than natural gas.

There have only been a small number of prototype hydrogen vehicles made. Most of these have been experimental vehicles made by car manufacturers. Nearly all of these prototype cars were equipped with internal combustion engines, similar to ones that run on gasoline.

Hydrogen is also used in fuel cells which are used to power fuel cell vehicles. Fuel cell vehicles are the most promising vehicles in saving the environment as they are considered zero-emission vehicles. Fuel cells have been used on spacecraft for many years to power electric equipment. These are fueled with liquid hydrogen from the spacecraft’s rocket fuel tanks.

Fuel cell vehicles turn hydrogen fuel and oxygen into electricity. The electricity then powers an electric motor, just like electricity from batteries powers the motor of an electric vehicle. Fuel cells combine oxygen from the air with hydrogen from the vehicle’s fuel tank to produce electricity. When oxygen and hydrogen are combined they give off energy and water (H2O). In fuel cells this is done without any burning (combustion).

When we think of vehicles that are fueled with hydrogen, we may think of rocket-powered spacecraft, like the space shuttle. The space shuttle is fueled with liquid oxygen and liquid hydrogen. To fly, the oxygen and hydrogen are mixed together and ignited to make a very hot fire.

The expanding gases from that fire are what propel the spacecraft. The exhaust from spacecraft rocket motors (and hydrogen-fueled fuel cells) is mostly water. That is why hydrogen-fueled fuel cell vehicles. Very little is in the exhaust except water. Fuel cells do get hot though, so the water comes out of the fuel cells as water vapor, or steam.

There are a number of ways that hydrogen can be provided to the fuel cell. One way is simply to put hydrogen gas into the fuel cell, along with air. Hydrogen gas can come from gaseous or liquid hydrogen stored on the vehicle.

To carry gaseous hydrogen on a vehicle, it must be compressed. When compressed (usually to a pressure of about 3000 pounds per square inch), it must be stored in special high-pressure containers. This is similar to the way compressed natural gas is stored on natural gas-fueled vehicles.

The other way to provide hydrogen gas to the fuel cell is to store it on the vehicle in liquid form. To make hydrogen liquid, it is chilled and compressed. Liquid hydrogen is very, very cold–more than 423.2 degrees Fahrenheit below zero!

This super-cold liquid hydrogen is the kind used in space rockets. The containers are able to hold pressure, but they are also insulated to keep the liquid hydrogen from warming up. Warming the liquid, or lowering the pressure, releases gas (like boiling water), and the gas can go to the fuel cell.

Another way to get hydrogen to the fuel cell is to use a “reformer”. A reformer is a device that removes the hydrogen from hydrocarbon fuels, like methanol or gasoline. When a fuel other than hydrogen is used, the fuel cell is no longer zero-emission, but it still may be very low emitting.

There is also a type of fuel cell that can be fueled with methanol directly. This is called a direct-methanol fuel cell. This type of fuel cell does not need a reformer to separate the hydrogen from the methanol. The fuel cell removes the hydrogen from the liquid methanol inside the fuel cell.

Many people in the vehicle manufacturing business think that fuel cell vehicles may be the technology of the future. However, a lot of work will have to be done to make fuel cell vehicles perform well enough to replace the internal combustion engine in the vehicles we use today. They also will need to be made much less expensive.

At present, fuel cell vehicles have only been developed to what might be called the pre-prototype stage. That means there are very few fuel cell vehicles in existence, and all of them are actually used for testing.

Most car manufacturers have or are working on demonstration models, some of which can reach a speed of 90 mph and can travel up to about 280 miles before they need refueling. Some manufacturers claim they will have fuel cell cars available for the public in the next ten years.