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Zinc–zinc Oxide Cycle
For chemical reactions, the zinc–zinc oxide cycle or Zn–ZnO cycle is a two step thermochemical cycle based on zinc and zinc oxide for hydrogen production with a typical efficiency around 40%. Process description The thermochemical two-step water splitting process uses redox systems: * Dissociation: ZnO → Zn + 1/2 O2 *Hydrolysis: Zn + H2O → ZnO + H2 For the first endothermic step concentrating solar power is used in which zinc oxide is thermally dissociated at into zinc and oxygen. In the second non-solar exothermic step zinc reacts at with water and produces hydrogen and zinc oxide. The temperature level is realized by using a solar power tower and a set of heliostats to collect the solar thermal energy. See also * Cerium(IV) oxide–cerium(III) oxide cycle A ceria based thermochemical cycle is a type of two-step thermochemical cycle that uses as oxygen carrier cerium oxides (CeO_2/Ce_2O_3) for synthetic fuel production such as hydrogen or syngas. These cycles a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Zinc Zinc-oxide Thermochemical Cycle
Zinc is a chemical element; it has symbol Zn and atomic number 30. It is a slightly brittle metal at room temperature and has a shiny-greyish appearance when oxidation is removed. It is the first element in group 12 (IIB) of the periodic table. In some respects, zinc is chemically similar to magnesium: both elements exhibit only one normal oxidation state (+2), and the Zn2+ and Mg2+ ions are of similar size. Zinc is the 24th most abundant element in Earth's crust and has five stable isotopes. The most common zinc ore is sphalerite (zinc blende), a zinc sulfide mineral. The largest workable lodes are in Australia, Asia, and the United States. Zinc is refined by froth flotation of the ore, roasting, and final extraction using electricity (electrowinning). Zinc is an essential trace element for humans, animals, plants and for microorganisms and is necessary for prenatal and postnatal development. It is the second most abundant trace metal in humans after iron, an important cof ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thermal Decomposition
Thermal decomposition, or thermolysis, is a chemical decomposition of a substance caused by heat. The decomposition temperature of a substance is the temperature at which the substance chemically decomposes. The reaction is usually endothermic as heat is required to break chemical bonds in the compound undergoing decomposition. If decomposition is sufficiently exothermic, a positive feedback loop is created producing thermal runaway and possibly an explosion or other chemical reaction. Decomposition temperature definition A simple substance (like water) may exist in equilibrium with its thermal decomposition products, effectively halting the decomposition. The equilibrium fraction of decomposed molecules increases with the temperature. Since thermal decomposition is a kinetic process, the observed temperature of its beginning in most instances will be a function of the experimental conditions and sensitivity of the experimental setup. For a rigorous depiction of the process, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Inorganic Reactions
An inorganic compound is typically a chemical compound that lacks carbon–hydrogen bondsthat is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as '' inorganic chemistry''. Inorganic compounds comprise most of the Earth's crust, although the compositions of the deep mantle remain active areas of investigation. All allotropes (structurally different pure forms of an element) and some simple carbon compounds are often considered inorganic. Examples include the allotropes of carbon (graphite, diamond, buckminsterfullerene, graphene, etc.), carbon monoxide , carbon dioxide , carbides, and salts of inorganic anions such as carbonates, cyanides, cyanates, thiocyanates, isothiocyanates, etc. Many of these are normal parts of mostly organic systems, including organisms; describing a chemical as inorganic does not necessarily mean that it cannot occur within living things. History Friedrich Wöhler's conv ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sulfur–iodine Cycle
The sulfur–iodine cycle (S–I cycle) is a three-step thermochemical cycle used to produce hydrogen. The S–I cycle consists of three chemical reactions whose net reactant is water and whose net products are hydrogen and oxygen. All other chemicals are recycled. The S–I process requires an efficient source of heat. Process description The three reactions combined to produce hydrogen are the following: : I2 + SO2 + 2 H2O 2 HI + H2SO4 () ( Bunsen reaction) : The HI is then separated by distillation or liquid/liquid gravitic separation. : 2 H2SO4 2 SO2 + 2 H2O + O2 () : The water, SO2 and residual H2SO4 must be separated from the oxygen byproduct by condensation. : 2 HI I2 + H2 () : Iodine and any accompanying water or SO2 are separated by condensation, and the hydrogen product remains as a gas. : Net reaction: 2 H2O → 2 H2 + O2 The sulfur and iodine compounds are recovered and reused, hence the consideration of the process as a cycle. This S–I process ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Iron Oxide Cycle
For chemical reactions, the iron oxide cycle (Fe3O4/FeO) is the original two-step thermochemical cycle proposed for use for hydrogen production. It is based on the reduction and subsequent oxidation of iron ions, particularly the reduction and oxidation between Fe3+ and Fe2+. The ferrites, or iron oxide, begins in the form of a spinel and depending on the reaction conditions, dopant metals and support material forms either Wüstites or different spinels. Process description The thermochemical two-step water splitting process uses two redox steps. The steps of solar hydrogen production by iron based two-step cycle are: : \begin \ce &\ce \\ \ce & \ce \end Where M can by any number of metals, often Fe itself, Co, Ni, Mn, Zn or mixtures thereof. The endothermic reduction step (1) is carried out at high temperatures greater than , though the " Hercynite cycle" is capable of temperatures as low as . The oxidative water splitting step (2) occurs at a lower ~ temperature which prod ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hybrid Sulfur Cycle
The hybrid sulfur cycle (HyS) is a two-step water-splitting process intended to be used for hydrogen production. Based on sulfur oxidation and reduction, it is classified as a hybrid thermochemical cycle because it uses an electrochemical (instead of a thermochemical) reaction for one of the two steps. The remaining thermochemical step is shared with the sulfur-iodine cycle. The Hybrid sulphur cycle (HyS)was initially proposed and developed by Westinghouse Electric Corp. in the 1970s, so it is also known as the "Westinghouse" cycle. Current development efforts in the United States are being led by the Savannah River National Laboratory. Process description The two reactions in the HyS cycle are as follows: # H2SO4 → H2O + SO2 + ½ O2 (thermochemical, ''T'' > 800 °C) # SO2 + 2 H2O → H2SO4 + H2 (electrochemical, ''T'' = 80-120 °C) : : Net reaction: H2O → H2 + ½ O2 Sulfur dioxide acts to depolarize the anode of the electrolyzer. This resu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Copper–chlorine Cycle
The copper–chlorine cycle (Cu–Cl cycle) is a four-step thermochemical cycle for the production of hydrogen. The Cu–Cl cycle is a hybrid process that employs both thermochemical and electrolysis steps. It has a maximum temperature requirement of about 530 degrees Celsius. The Cu–Cl cycle involves four chemical reactions for water splitting, whose net reaction decomposes water into hydrogen and oxygen. All other chemicals are recycled. The Cu–Cl process can be linked with nuclear plants or other heat sources such as solar and industrial waste heat to potentially achieve higher efficiencies, lower environmental impact and lower costs of hydrogen production than any other conventional technology. The Cu–Cl cycle is one of the prominent thermochemical cycles under development within the Generation IV International Forum (GIF). Through GIF, over a dozen countries around the world are developing the next generation of nuclear reactors for highly efficient production of bo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cerium(IV) Oxide–cerium(III) Oxide Cycle
A ceria based thermochemical cycle is a type of two-step thermochemical cycle that uses as oxygen carrier cerium oxides (CeO_2/Ce_2O_3) for synthetic fuel production such as hydrogen or syngas. These cycles are able to obtain either hydrogen (H_2) from the splitting of water molecules (H_2O), or also syngas, which is a mixture of hydrogen (H_2) and carbon monoxide (CO), by also splitting carbon dioxide (CO_2) molecules alongside water molecules. These types of thermochemical cycles are mainly studied for concentrated solar applications. Types of cycles These cycles are based on the two step redox thermochemical cycle. In the first step, a metal oxide, such as ceria, is reduced by providing heat to the material, liberating oxygen. In the second step, a stream of steam oxidises the previously obtained molecule back to its starting state, therefore closing the cycle. Depending on the stoichiometry of the reactions, which is the relation of the reactants and products of the chemical ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Solar Thermal Energy
Solar thermal energy (STE) is a form of energy and a technology for harnessing solar energy to generate thermal energy for use in Industrial sector, industry, and in the residential and commercial sectors. Solar thermal collectors are classified by the United States Energy Information Administration as low-, medium-, or high-temperature collectors. Low-temperature collectors are generally unglazed and used to heat swimming pools or to heat ventilation air. Medium-temperature collectors are also usually flat plates but are used for heating water or air for residential and commercial use. High-temperature collectors concentrate sunlight using mirrors or Lens (optics), lenses and are generally used for fulfilling heat requirements up to () / 20 Bar (unit), bar (300 psi) pressure in industries, and for electric power production. Two categories include Concentrated Solar Thermal (CST) for fulfilling heat requirements in industries, and concentrated solar power (CSP) when th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Heliostat
A heliostat () is a device that reflects sunlight toward a target, turning to compensate for the Sun's apparent motion. The reflector is usually a plane mirror. The target may be a physical object, distant from the heliostat, or a direction in space. To do this, the reflective surface of the mirror is kept perpendicular to the bisector of the angle between the directions of the Sun and the target as seen from the mirror. In almost every case, the target is stationary relative to the heliostat, so the light is reflected in a fixed direction. According to contemporary sources the heliostata, as it was called at first, was invented by Willem 's Gravesande (1688–1742). Other contenders are Giovanni Alfonso Borelli (1608–1679) and Daniel Gabriel Fahrenheit (1686–1736). A heliostat designed by George Johnstone Storey is in the Science Museum Group collection. Currently, most heliostats are used for daylighting or for the production of concentrated solar power, us ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Solar Power Tower
A solar power tower, also known as 'central tower' power plant or 'heliostat' power plant, is a type of solar furnace using a tower to receive focused sunlight. It uses an array of flat, movable mirrors (called heliostats) to focus the sun's rays upon a collector tower (the target). Concentrating Solar Power (CSP) systems are seen as one viable solution for renewable, pollution-free energy. Early designs used these focused rays to heat water and used the resulting steam to power a turbine. Newer designs using liquid sodium have been demonstrated, and systems using molten salts (40% potassium nitrate, 60% sodium nitrate) as the working fluids are now in operation. These working fluids have high heat capacity, which can be used to store the energy before using it to boil water to drive turbines. Storing the heat energy for later recovery allows power to be generated continuously, while the sun is shining, and for several hours after the sun has set (or been clouded over). Cost ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
