Written by AZoCleantechJan 12 2008
Hydrogen can be considered as a clean energy carrier, similar to electricity. Hydrogen can be produced from various domestic resources such as renewable energy and nuclear energy. In the long-term, hydrogen will simultaneously reduce the dependence on foreign oil and the emission of greenhouse gases and other pollutants.
What is Hydrogen?
Hydrogen can be considered as the simplest element in existence. Hydrogen is also one of the most abundant elements in the earth’s crust. However, hydrogen as a gas is not found naturally on Earth and must be manufactured. This is because hydrogen gas is lighter than air and rises into the atmosphere as a result. Natural hydrogen is always associated with other elements in compound form such as water, coal and petroleum.
Hydrogen has the highest energy content of any common fuel by weight. On the other hand, hydrogen has the lowest energy content by volume. It is the lightest element, and it is a gas at normal temperature and pressure.
Hydrogen as an Energy Carrier
Hydrogen is considered as a secondary source of energy, commonly referred to as an energy carrier. Energy carriers are used to move, store and deliver energy in a form that can be easily used. Electricity is the most well-known example of an energy carrier.
Hydrogen as an important energy carrier in the future has a number of advantages. For example, a large volume of hydrogen can be easily stored in a number of different ways, including underground hydrogen storage, compressed hydrogen in tanks, or through chemical compounds that release hydrogen after heating.
Hydrogen is also considered as a high efficiency, low polluting fuel that can be used for transportation, heating, and power generation in places where it is difficult to use electricity. In some instances, it is cheaper to ship hydrogen by pipeline than sending electricity over long distances by wire.
How is Hydrogen Produced?
Since hydrogen does not exist on Earth as a gas, it must be separated from other compounds. Two of the most common methods used for the production of hydrogen are electrolysis or water splitting and steam reforming.
Steam reforming is currently the least expensive method for producing hydrogen, but building the plants for the process is expensive. It is used in industries to separate hydrogen atoms from carbon atoms in methane. Unfortunately, because methane is a fossil fuel, the process of steam reforming results in greenhouse gas emissions, which is linked to global warming.
The other method for the production of hydrogen is electrolysis. Electrolysis involves passing an electric current through water to separate water into its basic elements, hydrogen and oxygen. Hydrogen is then collected at the negatively charged cathode and oxygen at the positive anode. Hydrogen produced by electrolysis is extremely pure, and results in no emissions since electricity from renewable energy sources can be used.
Unfortunately, electrolysis is currently a very expensive process, but costs may fall if the cost of electricity to carry out the procedure also falls.
There are also several experimental methods of producing hydrogen such as photo-electrolysis and biomass gasification. Scientists have also discovered that some algae and bacteria produce hydrogen under certain conditions, using sunlight as their energy source.
Uses of Hydrogen
Currently, hydrogen is mainly used as a fuel in the NASA space program. Liquid hydrogen is used to propel space shuttle and other rockets, while hydrogen fuel cells power the electrical systems of the shuttle. The hydrogen fuel cell is also used to produce pure water for the shuttle crew.
Hydrogen is also used in agriculture to create fertilizers, and to make cyclohexane and methanol, substances used in the production of plastics and pharmaceuticals. Oil-refining processes also make use of hydrogen gas.
Hydrogen Fuel Cell
Fuel cells directly convert the chemical energy in hydrogen to electricity, with pure water and heat as the only by-products. Hydrogen-powered fuel cells are not only pollution-free, but a two- to three-fold increase in the efficiency can be experienced when compared to traditional combustion technologies.
Figure 1. Hydrogen Fuel Cell (Image source U.S. Dept. of Energy)
Fuel cells can power almost any portable devices that normally use batteries. Fuel cells can also power transportation such as vehicles, trucks, buses, and marine vessels, as well as provide auxiliary power to traditional transportation technologies. Hydrogen can play a particularly important role in the future by replacing the imported petroleum we currently use in our cars and trucks.
The Future of Hydrogen
In the future, hydrogen will join electricity as an important energy carrier, since it can be made safely from renewable energy sources and is virtually non-polluting. It will also be used as a fuel for ‘zero-emissions’ vehicles, to heat homes and offices, to produce electricity, and to fuel aircraft.
Hydrogen has great potential as a way to reduce reliance on imported energy sources such as oil. But, before hydrogen can play a bigger energy role and become a widely used alternative to gasoline, many new facilities and systems must be built.
Figure 2. Future hydrogen energy infrastructure. The hydrogen is produced through a wind electrolysis system. The hydrogen is compressed up to pipeline pressure, and then fed into a transmission pipeline. The pipeline transports the hydrogen to a compressed gas terminal where the hydrogen is loaded into compressed gas tube trailers. A truck delivers the tube trailers to a forecourt station where the hydrogen is further compressed, stored, and dispensed to fuel cell vehicles. (Image source U.S. Dept. of Energy)
This article was updated on 10th July, 2019.