Solar–hydrogen energy cycle is an energy cycle where a
solar
Solar may refer to:
Astronomy
* Of or relating to the Sun
** Solar telescope, a special purpose telescope used to observe the Sun
** A device that utilizes solar energy (e.g. "solar panels")
** Solar calendar, a calendar whose dates indicate t ...
powered
electrolyzer
In chemistry and manufacturing, electrolysis is a technique that uses direct electric current (DC) to drive an otherwise non-spontaneous chemical reaction. Electrolysis is commercially important as a stage in the separation of elements from n ...
is used to convert water to
hydrogen
Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic, an ...
and
oxygen
Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as wel ...
. Hydrogen and oxygen produced thus are stored to be used by a
fuel cell
A fuel cell is an electrochemical cell that converts the chemical energy of a fuel (often hydrogen) and an oxidizing agent (often oxygen) into electricity through a pair of redox reactions. Fuel cells are different from most batteries in requ ...
to produce electricity when no sunlight is available.
Working
Photovoltaic panels convert sunlight to electricity. In this cycle, the excess electricity produced after consumption by devices connected to the system, is used to power an
electrolyzer
In chemistry and manufacturing, electrolysis is a technique that uses direct electric current (DC) to drive an otherwise non-spontaneous chemical reaction. Electrolysis is commercially important as a stage in the separation of elements from n ...
. The electrolyzer converts water into hydrogen and oxygen, which is stored. This hydrogen is used up by a
fuel cell
A fuel cell is an electrochemical cell that converts the chemical energy of a fuel (often hydrogen) and an oxidizing agent (often oxygen) into electricity through a pair of redox reactions. Fuel cells are different from most batteries in requ ...
to produce electricity, which can power the devices when sunlight is unavailable.
[
]
Features
The Solar–Hydrogen energy cycle can be incorporated using organic thin film solar cells and microcrystalline silicon
Nanocrystalline silicon (nc-Si), sometimes also known as microcrystalline silicon (μc-Si), is a form of porous silicon. It is an allotropic form of silicon with paracrystalline structure—is similar to amorphous silicon (a-Si), in that it has ...
thin film solar cells This cycle can also be incorporated using photoelectrochemical solar cells. These solar have been incorporated since 1972[
]
Use of hydrogen iodide
An aqueous solution
An aqueous solution is a solution in which the solvent is water. It is mostly shown in chemical equations by appending (aq) to the relevant chemical formula. For example, a solution of table salt, or sodium chloride (NaCl), in water would be re ...
of hydrogen iodide
Hydrogen iodide () is a diatomic molecule and hydrogen halide. Aqueous solutions of HI are known as hydroiodic acid or hydriodic acid, a strong acid. Hydrogen iodide and hydroiodic acid are, however, different in that the former is a gas under sta ...
has been proposed as an alternative to water as a fuel that can be used in this cycle. Splitting of hydrogen iodide is easier than splitting water as its Gibbs energy change for decomposition is lesser. Hence silicon photoelectrodes can decompose hydrogen iodide into hydrogen and iodine without any external bias.[
]
Advantages
* This cycle is pollution free as the only effluent from this cycle is pure water.[
]
See also
*Energy storage
Energy storage is the capture of energy produced at one time for use at a later time to reduce imbalances between energy demand and energy production.
A device that stores energy is generally called an accumulator or battery.
Energy comes in ...
* Photoelectrolysis of water
* Photocatalytic water splitting
* Power to gas
References
{{DEFAULTSORT:Solar-hydrogen energy cycle
Thermodynamic cycles
Hydrogen production