Hydrogen

        Hydrogen is the most abundant element in the universe, making up 75% of all mass of all visible matter in stars and galaxies. Hydrogen is the simplest of all elements. A hydrogen atom has a dense central nucleus with a single orbiting electron, much like a single planet in orbit around the sun. Hydrogen has the greatest energy to weight quotient of any fuel because hydrogen is the lightest of all the elements. Hydrogen has been used extensively in the space program where weight is crucial. The amount of energy released during the reaction of hydrogen, on a unit mass basis, is about 2.5 times the heat of combustion of common hydrocarbon fuels such as; gasoline, diesel, methane, propane, etc. Therefore, on a comparison basis the amount of hydrogen required is only about a third of the amount of hydrocarbon fuel needed to do the same amount of work. The current drawback of hydrogen as a fuel is storage space volume. On a comparison basis with hydrogen and diesel fuel, the volume of the hydrogen storage tank would have to be 16 times larger for gaseous hydrogen and 4 times larger for liquid hydrogen in comparison to diesel fuel.

        Hydrogen can be stored as a gas, a cryogenic liquid, or a metal hydride. According to Department of Energy guidelines, in a draft released on June 3, 2003 the goal for technical production of hydrogen is to become competitive with gasoline by 2015.

Hydrogen Manufacture

        Hydrogen, despite its abundance, does not occur freely on earth like oil or natural gas. It is bound into molecular compounds and must be extracted first. There are two primary methods for producing hydrogen, reformation and electrolysis. Both methods have advantages and disadvantages. Reformers, because of their fossil fuel stock, are  more efficient due to higher molecular energy.  Simply put, water (H2O), has less hydrogen atoms and is at a lower energy density than say compared to propane (C3H8).  Electrolysis of water uses a premium amount of input energy to extract hydrogen when compared to other extraction methods. The most common method of hydrogen production is the steam reforming process. The main process step of reforming involves the reaction of steam with a hydrocarbon over a catalyst at around 750-800°C. The process also involves the use of a catalyst like platinum, which speeds the reaction. Hydrogen is released in this process as well as carbon by-products.

        The second most common process is electrolysis of water. In electrolysis, electricity is used to decompose water into its elemental parts; hydrogen and oxygen. Electrolysis is often mentioned as the preferred method of hydrogen production, it is the main process that doesn’t rely on fossil fuels.  Electrolysis results in purer products and also works on either small or large scales.  Electrolysis can operate over a varying range of electrical energy capacities.  Electrolysis is made possible by an electrolyzer, which is a series of cells each with positive and negative electrodes.  Alkaline potassium hydroxide (KOH) is dissolved in water making it electrically conductive. The positive electrode is called the anode; it is usually made of nickel and copper, and is coated with metal oxides such as tungsten, manganese, and ruthenium. The anode makes quick pairing of atomic oxygen into oxygen pairs on the electrode surface. The negative electrode is called (cathode) is typically made of nickel, coated with small quantities of platinum as a catalyst. The catalyst allows quick pairing of atomic hydrogen into pairs on the electrode surface increasing the rate of hydrogen production. Hydrogen would build up on the electrode and block current flow without the catalyst. A diaphragm is used as a gas separator and to prevent intermixing of the hydrogen and oxygen, but still allows free passage of ions.

Fuel Cells

        Fuel cells harness the chemical energy of hydrogen to generate electricity without combustion or pollution.  Fuel cells were invented by Sir William Grove in 1839. Research and development continued for 120 years until Francis T. Bacon successfully demonstrated the first fully operational fuel cell in 1959.  Further work served as the foundation for power systems eventually used in the Gemini and Apollo space flights. These early cells were very expensive and used pure hydrogen and oxygen as their reactant fuel. NASA and the energy crisis of 1973 pushed development of fuel cells to the forefront and great advances in technology and efficiency have occurred since.  Fuel cells are much like electrolyzers, only in reverse.  One of the most common types of fuel cell is the PEM fuel cell (Polymer Electrolyte Membrane), it consists of an electrolyte membrane placed between a cathode an anode, the membrane is as thick as a few pages of paper. The membrane is kept moist to function as an electrolyte; it conducts positive ions (protons) but not electrons. The anode is composed partly of platinum where oxidation (loss of electrons) takes place the platinum acts a catalyst. Hydrogen passes through the porous anode, the reaction strips off hydrogen producing available current. Fuel cells when run on pure hydrogen gives off  by-products of pure water and heat. Efficiency of an internal combustion engine is only about 28%, compared to fuel cell where the efficiency is approaching 70%.

Road Map

        The department of energy has proposed a “National Hydrogen Energy Roadmap” where The United States is completely in a hydrogen economy by 2030. Strategic goals include the development of a national hydrogen filling station network, research into advanced hydrogen production from coal gasification, and biomass production from plants and algae. Fuel cells research shows promise as low-cost hydrogen catalysts are developed and cost reductions in fuel cell manufacturing are realized through future research.

President George W. Bush in his 2003 State of the Union Address given on January 28, 2003 stated: "Tonight I am proposing $1.2 billion in research funding so that America can lead the world in developing clean, hydrogen-powered automobiles."..."Join me in this important innovation to make our air significantly cleaner, and our country much less dependent on foreign sources of energy."

        As we advanced as a society, we went from burning wood, to coal, then oil, and in 1999, natural gas became our primary energy carrier.  In each case if we look at the molecular structure we were already burning hydrogen, each elemental group has more and more hydrogen in its basic chemical structure. Now its hydrogen’s turn! It can be produced, stored and used, its clean, reliable and abundant! Hydrogen indeed has become the new currency of the future and the fuel cell will change our lives as much as the computer it powers and the internal combustion engine it replaces.

Examples and Graphs

        In many respects, hydrogen fires are safer than gasoline fires. Hydrogen gas rises quickly due to its high buoyancy and diffusivity. Consequently, hydrogen fires are vertical and highly localized. When a car hydrogen cylinder ruptures and is ignited, the fire burns away from the car and the interior typically does not get very hot.

Rendering of a typical PEM fuel cell and samples of Fuel Cell Stacks

       

Annual Energy Outlook 2004 with Projections to 2025