Humans have used hydrogen, the most abundant element in the universe, for hundreds of years. Early applications included blimps and balloons, while more recent hydrogen technologies have become essential to oil refineries and chemical manufacturing. Hydrogen may also have great potential in the energy and transportation industries, where it can be used with existing designs or more advanced technologies still in development. Research efforts are also underway to find environmentally friendly alternatives to the traditional methods of producing hydrogen from natural gas or other fossil fuels.
Listed on the periodic table of elements as "H," hydrogen is the most common chemical element in the universe, and has been used by humans in various ways for hundreds of years. It is also the lightest known element, which led to its use as a lifting gas in balloons and airships beginning in the late 1700s. Its use increased following the industrial revolution, and a variety of new technologies were developed to produce, transport, and store hydrogen to meet increased demand. Oil refineries are particularly heavy users, but hydrogen is also used in medicine, chemical manufacturing, and scientific research. As energy prices and environmental concerns grow, more and more attention is being paid to hydrogen technologies in the energy and transportation industries.
Some hydrogen technologies use existing designs or components that have been modified or optimized to use the element as a fuel source. In its highly flammable liquid and gas forms, hydrogen can be burned to power internal combustion engines or drive electricity-producing turbines. These technologies have already been proven with other fuel sources, so most research and development efforts focus on finding safer and more practical ways to store and transport hydrogen fuel. Existing infrastructure such as fuel tanks, filling stations, and pipelines may need to be modified or retooled. Although using hydrogen in this way can be cleaner than alternatives like gasoline, burning any fuel — including hydrogen — creates air pollution as a byproduct of combustion.
Another category of hydrogen technologies, hydrogen fuel cells, produces electricity through a series of chemical reactions rather than burning fuel. The only byproducts left behind are water and heat, which can often be reused for other purposes including heating a building. Multiple fuel cells are grouped together into a fuel cell stack. The size of the stack can be adjusted based on the amount of electricity needed for a particular application, which means the same technology can be used in both a small portable unit capable of charging small electronics and a full-sized power plant. A fuel cell stack can also be paired with electric motors to create a pollution-free fuel cell vehicle (FCV) or may be used to store electricity produced by wind, solar, or other renewable energy systems.
Although it is touted by many as a form of clean energy, hydrogen is often produced from natural gas and other fossil fuels, a process that can create pollution and greenhouse emissions. In order for hydrogen technologies to be a truly green source of alternative energy, new strategies for producing and transporting the element need to be developed. Since the early 2000s, research has shown that hydrogen can potentially be created or extracted from a variety of more sustainable sources including algae farms, wind, and solar powered electrolysis and even from human urine. Clean energy advocates remain hopeful that several of these technologies could become commercially viable on a large scale.