Solar–hydrogen energy cycle
Encyclopedia
Solar–Hydrogen energy cycle is an energy cycle where a solar powered electrolyzer is used to convert water to hydrogen
and oxygen
. Hydrogen and oxygen produced thus are stored to be used by a fuel cell
to produce electricity when no sunlight is available.
to produce electricity, which can power the devices when sunlight is unavailable.
s This cycle can also be incorporated using photoelectrochemical solar cells
. These solar have been incorporated since 1972 for hydrogen production and is capable of directly converting sunlight into chemical energy.
of hydrogen iodide
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.
Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...
and oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
. Hydrogen and oxygen produced thus are stored to be used by a fuel cell
Fuel cell
A fuel cell is a device that converts the chemical energy from a fuel into electricity through a chemical reaction with oxygen or another oxidizing agent. Hydrogen is the most common fuel, but hydrocarbons such as natural gas and alcohols like methanol are sometimes used...
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. The electrolyzer converts water into hydrogen and oxygen, which is stored. This hydrogen is used up by a fuel cellFuel cell
A fuel cell is a device that converts the chemical energy from a fuel into electricity through a chemical reaction with oxygen or another oxidizing agent. Hydrogen is the most common fuel, but hydrocarbons such as natural gas and alcohols like methanol are sometimes used...
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 thin film solar cellThin film solar cell
A thin-film solar cell , also called a thin-film photovoltaic cell , is a solar cell that is made by depositing one or more thin layers of photovoltaic material on a substrate...
s This cycle can also be incorporated using photoelectrochemical solar cells
Photoelectrochemical cell
Photoelectrochemical cells or PECs are solar cells which generate electrical energy from light, including visible light. Some photoelectrochemical cells simply produce electrical energy, while others produce hydrogen in a process similar to the electrolysis of water.-Photogeneration cell:In this...
. These solar have been incorporated since 1972 for hydrogen production and is capable of directly converting sunlight into chemical energy.
Use of hydrogen iodide
An aqueous solutionAqueous solution
An aqueous solution is a solution in which the solvent is water. It is usually shown in chemical equations by appending aq to the relevant formula, such as NaCl. The word aqueous means pertaining to, related to, similar to, or dissolved in water...
of hydrogen iodide
Hydrogen iodide
Hydrogen iodide is a diatomic molecule. Aqueous solutions of HI are known as iohydroic acid or hydroiodic acid, a strong acid. Gas and aqueous solution are interconvertible...
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.
- Since a hydrogen powered energy economy is more stable than conventional energy economies, this cycle can be incorporated in politically unstable countries.