Re hydrogen fuel cell energy supply for home and personal transportation
Don't bet against the Japanese when it comes to energy efficiency and mobility..they are already in the third generation of accomplishing this ....they could not afford to allow a 'Regan'(or a Bush) to risk their survival (nor the 'head of an Automobile manufacturing company that didn't know anything about cars..GM?)
..there are many ways to get hydrogen
and the key is the way to store it in the car as power plant for the home as well..'the proof will be in the pudding'
Main article: Hydrogen production
energy). Wikipedia
[edit] Kværner-process
The Kværner-process or Kvaerner carbon black & hydrogen process (CB&H)[23] is a method, developed in the 1980s by a Norwegian company of the same name, for the production of hydrogen from hydrocarbons (CnHm), such as methane, natural gas and biogas.
Of the available energy of the feed, approximately 48% is contained in the Hydrogen, 40% is contained in activated carbon and 10% in superheated steam.[24]
[edit] Fermentative hydrogen production
Fermentative hydrogen production is the fermentative conversion of organic substrate to biohydrogen manifested by a diverse group bacteria using multi enzyme systems involving three steps similar to anaerobic conversion. Dark fermentation reactions do not require light energy, so they are capable of constantly producing hydrogen from organic compounds throughout the day and night. Photofermentation differs from dark fermentation because it only proceeds in the presence of light. For example photo-fermentation with Rhodobacter sphaeroides SH2C can be employed to convert small molecular fatty acids into hydrogen[25]. Electrohydrogenesis is used in microbial fuel cells where hydrogen is produced from organic matter while 0.2 - 0.8 V is applied.
[edit] Biological production
Main article: Biological hydrogen production (Algae)
Biological hydrogen can be produced in an algae bioreactor. In the late 1990s it was discovered that if the algae is deprived of sulfur it will switch from the production of oxygen, i.e. normal photosynthesis, to the production of hydrogen.
It seems that the production is now economically feasible by surpassing the 7–10 percent energy efficiency (the conversion of sunlight into hydrogen) barrier.
Biological hydrogen can and is produced in bioreactors that utilize feedstocks other than algae, the most common feedstock being waste streams. The process involves bacteria feeding on hydrocarbons and exhaling hydrogen and CO2. The CO2 can be sequestered successfully by several methods, leaving hydrogen gas. A prototype hydrogen bioreactor using waste as a feedstock is in operation at Welch's grape juice factory in North East, Pennsylvania.
[edit] Electrolysis of water
Electrolysis of water ship Hydrogen Challenger
The predominant methods of hydrogen production rely on exothermic chemical reactions of fossil fuels to provide the energy needed to chemically convert feedstock into hydrogen. But when the energy supply is mechanical (hydropower or wind turbines), hydrogen can be made via high pressure electrolysis or low pressure electrolysis of water. In current market conditions, the 50 kWh of electricity consumed to manufacture one kilogram of compressed hydrogen is roughly as valuable as the hydrogen produced, assuming 8 cents/kWh. The price equivalence, despite the inefficiencies of electrical production and electrolysis, are due to the fact that most hydrogen is made from fossil fuels which couple more efficiently to producing the chemical directly, than they do to producing electricity. However, this is of no help to a hydrogen economy, which must derive hydrogen from sources other than the fossil fuels it is intended to replace.[26]
[edit] Photoelectrochemical water splitting
Using electricity produced by photovoltaic systems offers the cleanest way to produce hydrogen. Water is broken into hydrogen and oxygen by electrolysis--a photoelectrochemical cell (PEC) process which is also named artificial photosynthesis. Research aimed toward developing higher-efficiency multijunction cell technology is underway by the photovoltaic industry.
[edit] High-pressure electrolysis
High pressure electrolysis is the electrolysis of water by decomposition of water (H2O) into oxygen (O2) and hydrogen gas (H2) due to an electric current being passed through the water. The difference with a standard electrolyzer is the compressed hydrogen output around 120-200 Bar (1740-2900 psi)[27]. By pressurising the hydrogen in the electrolyser the need for an external hydrogen compressor is eliminated, the average energy consumption for internal compression is around 3%[28].
[edit] High-temperature electrolysis
Hydrogen can be generated from energy supplied in the form of heat (e.g., that of concentrating solar thermal or nuclear) and electricity through high-temperature electrolysis (HTE). In contrast with low-temperature electrolysis, HTE of water converts more of the initial heat energy into chemical energy (hydrogen), potentially doubling efficiency, to about 50%. Because some of the energy in HTE is supplied in the form of heat, less of the energy must be converted twice (from heat to electricity, and then to chemical form), and so potentially far less energy is required per kilogram of hydrogen produced.
[edit] Nuclear
One side benefit of a nuclear reactor that produces both electricity and hydrogen is that it can shift production between the two. For instance, the plant might produce electricity during the day and hydrogen at night, matching its electrical generation profile to the daily variation in demand, and offloading the extra output at night into a storable medium for energy. It is possible that research into HTE and high-temperature nuclear reactors may eventually lead to a hydrogen supply that is cost-competitive with natural gas steam reforming. For example, some prototype Generation IV reactors have coolant exit temperatures of 850 to 1000 degrees Celsius, considerably hotter than existing commercial nuclear power plants. High temperature (950–1000 °C) gas cooled nuclear reactors have the potential to split hydrogen from water by thermochemical means using nuclear heat. General Atomics predicts that hydrogen produced in a High Temperature Gas Cooled Reactor (HTGR) would cost $1.53/kg. In 2003, steam reforming of natural gas yielded hydrogen at $1.40/kg. At 2005 natural gas prices, hydrogen costs $2.70/kg. HTE has been demonstrated in a laboratory, at 108 megajoules (thermal) per kilogram of hydrogen produced,[29] but not at a commercial scale.[30]The first commercial generation IV reactors are expected around 2030.
[edit] Concentrating solar thermal
The high temperatures necessary to split water can be achieved through the use of concentrating solar power. Hydrosol-2 is a 100-kilowatt pilot plant at the Plataforma Solar de Almería in Spain which uses sunlight to obtain the required 800 to 1,200 °C to split water. Hydrosol II has been in operation since 2008. The design of this 100-kilowatt pilot plant is based on a modular concept. As a result, it may be possible that this technology could be readily scaled up to the megawatt range by multiplying the available reactor units and by connecting the plant to heliostat fields (fields of sun-tracking mirrors) of a suitable size.[31]
[edit] Biocatalysed electrolysis
Besides regular electrolysis, electrolysis using microbes is another possibility. Using Microbial fuel cells, wastewater or plants such as can be used to generate power. Biocatalysed electrolysis should not be confused with biological hydrogen production, as the latter only uses algae and with the latter, the algae itself generates the hydrogen instantly, where with biocatalysed electrolysis, this happens after running through the microbial fuel cell and a variety of aquatic plants can be used. These include reed sweetgrass, cordgrass, rice, tomatoes, lupines, algae [32]
[edit] Thermochemical production
There are more than 352[33] thermochemical cycles which can be used for water splitting[34], around a dozen of these cycles such as the iron oxide cycle, cerium(IV) oxide-cerium(III) oxide cycle, zinc zinc-oxide cycle, sulfur-iodine cycle, copper-chlorine cycle and hybrid sulfur cycle are under research and in testing phase to produce hydrogen and oxygen from water and heat without using electricity[35]. These processes can be more efficient than high-temperature electrolysis, typical in the range from 35 % - 49 % LHV efficiency. Thermochemical production of hydrogen using chemical energy from coal or natural gas is generally not considered, because the direct chemical path is more efficient.
None of the thermochemical hydrogen production processes have been demonstrated at production levels, although several have been demonstrated in laboratories.
[edit] Reactive production
Hydrogen is the product of a number of chemical reactions with metals. Sodium is a classic example, with water and sodium metal reacting to form sodium hydroxide and hydrogen. Another example which has gained some recent interest is aluminium or an aluminium/gallium alloy reacting with water to produce aluminium hydroxide and hydrogen.[36] [37] In all cases the metal is consumed. The reaction product(s) (other than the hydrogen) would then be recovered for regeneration in an energy-consuming process or directly in some application. |
