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Hydrogen production from electrolysis of water is the decomposition of
water (H2O) into oxygen (O2) and hydrogen gas (H2) by using an electric
current. This hydrogen produced from the electrolytic process is used in
industrial applications today.
H2O + Electricity H2 + O2
An electrical power source is connected to two electrodes, or two plates,
(typically made from some inert metal such as platinum or stainless steel)
which are placed in the water. Hydrogen is produced at the cathode (the
negatively charged electrode, where electrons are pumped into the water),
and oxygen is produced at the anode (the positively charged electrode).
The generated amount of hydrogen is twice the amount of oxygen, and both
are proportional to the total electrical charge being sent through the water.
Electrolysis cells are characterized by their electrolyte type. There are
two types of low temperature electrolysis: alkaline and proton exchange
membrane (PEM). Alkaline electrolysis utilizes a liquid electrolyte consisting
of highly concentrated potassium hydroxide (KOH). PEM electrolysis is based
on the use of a solid conducting polymer that conducts ions when hydrated
with water.
Proton Exchange Membrane electrolyzers are sold worldwide and are used
in a variety of industrial and laboratory applications, including heat treating,
printed circuit board manufacturing, cooling of power plant turbine generator
windings, weather balloon filling, and gas chromatography. These electrolyzers
have demonstrated high reliability in a wide range of environments and duty
cycles.
In addition to industrial hydrogen applications, several emerging hydrogen
energy markets serve as opportunities for PEM based electrolysis. The common
element of these market opportunities is the need or desire for onsite,
electrolysis-based hydrogen generation. The markets are backup power for
wireless telecommunication sites, emergency facilities, and residential
backup power applications and hydrogen fueling for vehicles, fleets, forklifts,
and scooters that incorporate a hydrogen fuel cell. Several fuel cell companies
have already begun offering backup power packages for these markets and
others are developing or offering fuel cells for mobile applications.
The typical hydrogen solution has involved delivered hydrogen. This is
not a practical solution for many backup power applications. High pressure
PEM electrolysis is a solution that can meet the recharge requirements defined
by power system developers. The integration of an electrolyzer into the
fuel cell system creates a rechargeable energy storage system known as a
regenerative fuel cell (RFC).
For fueling, the ability to produce the hydrogen at the point of use
eliminates the need for transporting fuels, provides for control of hydrogen
needs, and increases the safety of operation at the fueling site. Furthermore,
integration with a renewable source of electricity such as wind or solar
enables the production of a truly green fuel, completely void of any green
house gas emissions.
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