 | Hydrogen economy: Encyclopedia II - Hydrogen economy - Rationale
Hydrogen economy - Rationale
Electricity has revolutionized the quality of human life since the late 19th century by enabling easier use of available energy sources. Inventions such as the dynamo and electric lighting sparked its growth on direct current. Later the alternator and alternating current enabled electric power transmission over long distances in a grand scale.
Currently, grid load balancing is done by varying the output of generators. However, electricity is hard to store efficiently for future use. The most cost-efficient and widespread system for large-scale grid energy storage is pumped storage, which consists of pumping water up to a dam reservoir and generating electricity on demand from that via hydropower. However such systems will not scale down to portable applications. Smaller storage alternatives such as capacitors have very low energy density. Batteries have low energy density and are slow to charge and discharge.
Around the time electricity started to come in use, another portable energy source was born. With internal combustion engines burning hydrocarbon fuels automobiles came into use. Internal combustion engines beat the competition at the time, such as compressed air, or electric automobiles powered by batteries, because they provided better range, by virtue of the efficiency of the internal combustion engine and high energy density of the hydrocarbon fuel. The high power-to-weight ratio of internal combustion engines also made it possible to build aircraft that have a higher density than air.
Present concerns regarding the long term availability of hydrocarbon fuels and global warming due to carbon dioxide (CO2) tailpipe emissions have given rise to a search for an alternative to hydrocarbon fossil fuels which does not have these problems.
Some think that fuel cells, using hydrogen as a fuel, are tomorrow's equivalent to the internal combustion engines of old.
Hydrogen is the most abundant element in the universe. It also has an excellent energy density by weight, which leads to it being used for spaceships like the space shuttle. Emissions of a hydrogen-oxygen fuel cell, in theory, consist of pure water. The fuel cell is also more efficient than an internal combustion engine.
Hydrogen economy - Envisioned centralized hydrogen sources
Large rural high efficiency generators combined with a distribution system (like the natural gas distribution system but able to meet hydrogen's additional transport challenges) and fuel cells that run on hydrogen might be able to replace today's electrical distribution and generation systems, and fuel vehicles. Similar systems are currently used with natural gas to produce electricity, such as large urban developents with cogeneration facilities. The energy source could be nuclear, or fossil fuel. Large generators that produced hydrogen from fossil fuel energy sources would generate huge amounts of pollution, but centralize emissions, so emission control systems would be easier to inspect and hence perhaps better maintained than systems on automobiles owned by individuals. However there are several technological "showstoppers" that stand in the way.
Unfortunately, pure hydrogen is not widely available on our planet. Most of it is locked in water or hydrocarbon fuels. It can be produced using other high-energy fuels, i.e. fossil fuels, but such methods require fossil fuels and generate CO2 to a greater extent than conventional engines and thus contribute to global warming more than if those fossil fuels were to be used directly to power automobiles for example. It can also be produced using huge amounts of energy and water. Nuclear power can provide the energy, but has well known disadvantages. Some 'Green' energy sources are capable of generating energy in a cost effective way if the externalities of conventional energy sources are factored in, but the policies of the world's major governments do not factor them in. However, most 'green' sources tend to produce rather low-intensity energy, not the prodigious amounts of energy required for extracting significant amounts of hydrogen using thermochemical electrolysis for example. This is called the production problem.
Hydrogen also has a poor energy density per volume. This means you need a large tank to store it, even when additional energy is used to compress it, and the high pressure compounds safety issues. The large tank reduces the fuel efficiency of the vehicle. Because it is a small energetic molecule, hydrogen tends to diffuse through any liner material intended to contain it, leading to the embrittlement, or weakening of its container. This is called the storage problem.
Other proponents envision local hydrogen sources, however the challenges large, rural high efficiency hydrogen generators face are far more acute when in an urban environment.
Fuel cells are still expensive. Some require expensive platinum group metals. Many have a low service life. They also used to be pretty bulky, but this is improving. Some think improved knowledge of nanotechnology and mass production will eventually solve this problem.
Other related archives'Green', 19th century, 2005, Alcohol fuel, Ammonia, Amory Lovins, As of 2005, Atlantic, Batteries, CH4, CO, California, Canada, Coal, Direct methanol fuel cells, Electrolysis, Fuel cells, Future energy development, General Atomics, Germany, Grid energy storage, H2, H2O, Hydridic Earth theory, Hydrocarbons, Hydrogen, Hydrogen car, Iceland, Japan, Li-on, Li-polymer batteries, Methanol economy, Nanotechnology, North Slope, Norwegian, O, Rocky Mountain Institute, Sabatier process, Solid-oxide fuel cells, Some prototype nuclear reactors, Space Shuttle, US, United States, Utsira, aircraft, alternating current, alternator, ammonia, automobile, automobiles, barbecue, borane, boron, buckyballs, capacitors, carbon, carbon dioxide, carbon monoxide, coal gasification, compressed air, concentrated solar thermal power collectors, cryogenic, dam, degrees Celsius, density, diesel fuel, direct current, dynamo, efficiency, electric lighting, electric power transmission, electric vehicles, electrical distribution, electricity, electrolysis, embrittlement, energy density, energy density per weight, ethanethiol, ethanol, fishing fleet, fossil fuels, free radicals, fuel cell, fuel cells, gasoline, generators, gigawatts, global warming, greenhouse gas, grid energy storage, heat, high-temperature electrolysis, hydrides, hydrocarbon, hydrogen embrittlement, hydrogen reformer, hydropower, internal combustion engines, kg, liquefied natural gas, liquid hydrogen, lithium, lithium aluminium hydride, mass production, methane, methanethiol, methanol, nanotechnology, nanotubes, natural gas, nuclear-powered, oxygen, ozone depletion, photosynthesis, platinum, platinum group, power-to-weight ratio, pressure vessel, propane, pumped storage, renewable resource, reservoir, service life, sodium borohydride, space shuttle, steam reforming, sulfur, sulfur-iodine cycle, syngas, town gas, underground or undersea, uranium, water, water gas shift reaction, water splitting, weight, wind power, wind turbines
 Adapted from the Wikipedia article "Rationale", under the G.N U Free Docmentation License. Please also see http://en.wikipedia.org/wiki |
