High-pressure electrolysis

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ITM Power's HGas electrolyser stacks, each operating at 80bar pressure High-pressure PEM electrolyser stacks.jpg
ITM Power's HGas electrolyser stacks, each operating at 80bar pressure
High-pressure PEM electrolyser. PEM electrolyzer.jpg
High-pressure PEM electrolyser.
PEM high pressure electrolyser.jpg

High-pressure electrolysis (HPE) is the electrolysis of water by decomposition of water (H2O) into oxygen (O2) and hydrogen gas (H2) due to the passing of an electric current through the water. [1] The difference with a standard proton exchange membrane electrolyzer is the compressed hydrogen output around 12–20 megapascals (120–200 bar) [2] at 70 °C. [3] By pressurising the hydrogen in the electrolyser the need for an external hydrogen compressor is eliminated, the average energy consumption for internal differential pressure compression is around 3%. [4]

Contents

Approaches

As the required compression power for water is less than that for hydrogen-gas the water is pumped up to a high-pressure, [5] in the other approach differential pressure is used. [6] There is also an importance for the electrolyser stacks to be able to accept a fluctuating electrical input, such as that found with renewable energy. [7] This then enables the ability to help with grid balancing and energy storage.

Ultrahigh-pressure electrolysis

Ultrahigh-pressure electrolysis is high-pressure electrolysis operating at 340–690 bars (5,000–10,000 psi). [8] At ultra-high pressures the water solubility and cross-permeation across the membrane of H2 and O2 is affecting hydrogen purity, modified PEMs are used to reduce cross-permeation in combination with catalytic H2/O2 recombiners to maintain H2 levels in O2 and O2 levels in H2 at values compatible with hydrogen safety requirements. [9] [10]

Research

The US DOE believes that high-pressure electrolysis, supported by ongoing research and development, will contribute to the enabling and acceptance of technologies where hydrogen is the energy carrier between renewable energy resources and clean energy consumers. [11]

High-pressure electrolysis is being investigated by the DOE for efficient production of hydrogen from water. The target total in 2005 is $4.75 per gge H2 at an efficiency of 64%. [10] The total goal for the DOE in 2010 is $2.85 per gge H2 at an efficiency of 75%. [11] As of 2005 the DOE provided a total of $1,563,882 worth of funding for research. [10]

Mitsubishi is pursuing such technology with its High-pressure hydrogen energy generator (HHEG) project. [12]

The Forschungszentrum Jülich, in Jülich Germany is currently researching the cost reduction of components used in high-pressure PEM electrolysis in the EKOLYSER [13] project. The primary goal of this research is to improve performance and gas purity, reduce cost and volume of expensive materials and reach the alternative energy targets set forth by the German government for 2050 in the Energy Concept published in 2010. [14] [15]

ThalesNano Energy released a lab-scale high pressure (100 bar) hydrogen generator as a replacement for hydrogen cylinders in chemistry laboratories. [16]

Commercial Products

Honda installed its Smart Hydrogen Station (SHS) in Los Angeles for use by fuel cell automobiles. [17]

See also

Related Research Articles

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A fuel cell is an electrochemical cell that converts the chemical energy of a fuel and an oxidizing agent into electricity through a pair of redox reactions. Fuel cells are different from most batteries in requiring a continuous source of fuel and oxygen to sustain the chemical reaction, whereas in a battery the chemical energy usually comes from substances that are already present in the battery. Fuel cells can produce electricity continuously for as long as fuel and oxygen are supplied.

Electrolysis Technique in chemistry and manufacturing

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 naturally occurring sources such as ores using an electrolytic cell. The voltage that is needed for electrolysis to occur is called the decomposition potential. The word "lysis" means to separate or break, so in terms, electrolysis would mean "breakdown via electricity".

A regenerative fuel cell or reverse fuel cell (RFC) is a fuel cell run in reverse mode, which consumes electricity and chemical B to produce chemical A. By definition, the process of any fuel cell could be reversed. However, a given device is usually optimized for operating in one mode and may not be built in such a way that it can be operated backwards. Standard fuel cells operated backwards generally do not make very efficient systems unless they are purpose-built to do so as with high-pressure electrolysers, regenerative fuel cells, solid-oxide electrolyser cells and unitized regenerative fuel cells.

Proton-exchange membrane fuel cell

Proton-exchange membrane fuel cells (PEMFC), also known as polymer electrolyte membrane (PEM) fuel cells, are a type of fuel cell being developed mainly for transport applications, as well as for stationary fuel-cell applications and portable fuel-cell applications. Their distinguishing features include lower temperature/pressure ranges and a special proton-conducting polymer electrolyte membrane. PEMFCs generate electricity and operate on the opposite principle to PEM electrolysis, which consumes electricity. They are a leading candidate to replace the aging alkaline fuel-cell technology, which was used in the Space Shuttle.

Hydrogen fuel is a zero-carbon fuel burned with oxygen; provided that it is created in a process that does not involve carbon. It can be used in fuel cells or internal combustion engines. Regarding hydrogen vehicles, hydrogen has begun to be used in commercial fuel cell vehicles such as passenger cars, and has been used in fuel cell buses for many years. It is also used as a fuel for spacecraft propulsion.

High-temperature electrolysis Technique for producing hydrogen from water

High-temperature electrolysis is a technology for producing hydrogen from water at high temperatures.

A proton-exchange membrane, or polymer-electrolyte membrane (PEM), is a semipermeable membrane generally made from ionomers and designed to conduct protons while acting as an electronic insulator and reactant barrier, e.g. to oxygen and hydrogen gas. This is their essential function when incorporated into a membrane electrode assembly (MEA) of a proton-exchange membrane fuel cell or of a proton-exchange membrane electrolyser: separation of reactants and transport of protons while blocking a direct electronic pathway through the membrane.

Electrolysis of water Electricity-induced chemical reaction

Electrolysis of water, also known as electrochemical water splitting, is the process of using electricity to decompose water into oxygen and hydrogen gas by a process called electrolysis. Hydrogen gas released in this way can be used as hydrogen fuel, or remixed with the oxygen to create oxyhydrogen gas, which is used in welding and other applications.

Ammonia is one of the most highly produced inorganic chemicals. There are numerous large-scale ammonia plants worldwide, producing a grand total of 144 million tonnes of nitrogen in 2016. This has increased to 235 million tonnes of ammonia in 2021. China produced 31.9% of the worldwide production, followed by Russia with 8.7%, India with 7.5%, and the United States with 7.1%. 80% or more of the ammonia produced is used for fertilizing agricultural crops. Ammonia is also used for the production of plastics, fibres, explosives, nitric acid, and intermediates for dyes and pharmaceuticals.

Hydrogen production is the family of industrial methods for generating hydrogen gas. As of 2020, the majority of hydrogen (∼95%) is produced from fossil fuels by steam reforming of natural gas and other light hydrocarbons, partial oxidation of heavier hydrocarbons, and coal gasification. Other methods of hydrogen production include biomass gasification, zero-CO2-emission methane pyrolysis, and electrolysis of water. The latter processes, methane pyrolysis as well as water electrolysis can be done directly with any source of electricity, such as solar power.

A hydrogen compressor is a device that increases the pressure of hydrogen by reducing its volume resulting in compressed hydrogen or liquid hydrogen.

Membrane electrode assembly

A membrane electrode assembly (MEA) is an assembled stack of proton-exchange membranes (PEM) or alkali anion exchange membrane (AAEM), catalyst and flat plate electrode used in fuel cells and electrolyzers.

Solid oxide electrolyzer cell Type of fuel cell

A solid oxide electrolyzer cell (SOEC) is a solid oxide fuel cell that runs in regenerative mode to achieve the electrolysis of water by using a solid oxide, or ceramic, electrolyte to produce hydrogen gas and oxygen. The production of pure hydrogen is compelling because it is a clean fuel that can be stored, making it a potential alternative to batteries, methane, and other energy sources. Electrolysis is currently the most promising method of hydrogen production from water due to high efficiency of conversion and relatively low required energy input when compared to thermochemical and photocatalytic methods.

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Power-to-gas is a technology that uses electric power to produce a gaseous fuel. When using surplus power from wind generation, the concept is sometimes called windgas.

Polymer electrolyte membrane electrolysis

Polymer electrolyte membrane(PEM) electrolysis is the electrolysis of water in a cell equipped with a solid polymer electrolyte (SPE) that is responsible for the conduction of protons, separation of product gases, and electrical insulation of the electrodes. The PEM electrolyzer was introduced to overcome the issues of partial load, low current density, and low pressure operation currently plaguing the alkaline electrolyzer. It involves a proton-exchange membrane.

Alkaline water electrolysis has a long history in the chemical industry. It is a type of electrolyzer that is characterized by having two electrodes operating in a liquid alkaline electrolyte solution of potassium hydroxide (KOH) or sodium hydroxide (NaOH). These electrodes are separated by a diaphragm, separating the product gases and transporting the hydroxide ions (OH) from one electrode to the other. A recent comparison showed that state-of-the-art nickel based water electrolyzers with alkaline electrolytes lead to competitive or even better efficiencies than acidic polymer electrolyte membrane water electrolysis with platinum group metal based electrocatalysts.

Hydrogenics is a developer and manufacturer of hydrogen generation and fuel cell products based on water electrolysis and proton exchange membrane (PEM) technology. Hydrogenics is divided into two business units: OnSite Generation and Power Systems. Onsite Generation is headquartered in Oevel, Belgium and had 73 full-time employees as of December 2013. Power Systems is based in Mississauga, Ontario, Canada, with a satellite facility in Gladbeck, Germany. It had 62 full-time employees as of December 2013. Hydrogenics maintains operations in Belgium, Canada and Germany with satellite offices in the United States, Indonesia, Malaysia and Russia.

Dioxide Materials was founded in 2009 in Champaign, Illinois, and is now headquartered in Boca Raton, Florida. Its main business is to develop technology to lower the world's carbon footprint. Dioxide Materials is developing technology to convert carbon dioxide, water and renewable energy into carbon-neutral gasoline (petrol) or jet fuel. Applications include CO2 recycling, sustainable fuels production and reducing curtailment of renewable energy(i.e. renewable energy that could not be used by the grid).

Pulse electrolysis Pulse Electrolysis

Pulse electrolysis is an alternate electrolysis method that utilises a pulsed direct current to initiate non-spontaneous chemical reactions. Also known as pulsed direct current (PDC) electrolysis, the increased number of variables that it introduces to the electrolysis method can change the application of the current to the electrodes and the resulting outcome. This varies from direct current (DC) electrolysis, which only allows the variation of one value, the voltage applied. By utilising conventional pulse width modulation (PMW), multiple dependent variables can be altered, including the type of waveform, typically a rectangular pulse wave, the duty cycle, and the frequency. Currently, there has been a focus on theoretical and experimental research into PDC electrolysis in terms of the electrolysis of water to produce hydrogen. Past research has demonstrated that there is a possibility it can result in a higher electrical efficiency in comparison to DC electrolysis. This would allow electrolysis procedures to produce greater volumes of hydrogen with a reduced electrical energy consumption. Although theoretical research has made large promise for the efficiencies and benefits of utilising pulse electrolysis, it has many contradictions including a common issue that it is difficult to replicate the successes of patents experimentally and produces its own negative effects on the electrolyser.

References

  1. "High pressure electrolysis". Archived from the original on 2009-05-02. Retrieved 2009-01-06.
  2. 2001-High pressure electrolysis – The key technology for efficient H.2 [ permanent dead link ]
  3. "Investigations of hydrogen compressor based on proton exchange membrane" (PDF). Archived from the original (PDF) on 2011-07-25. Retrieved 2009-04-13.
  4. 2003-PHOEBUS-Pag.9 Archived 2009-03-27 at the Wayback Machine
  5. Prediction of production power for high-pressure hydrogen by high-pressure water electrolysis
  6. Differential pressure
  7. "Electrolyser Stacks | ITM Power". Archived from the original on 2013-05-12. Retrieved 2013-05-20.
  8. XI.13 High-Efficiency, Ultra-High Pressure Electrolysis with Direct Linkage to Photovoltaic Arrays (Phase II Project) (Available here Accessed 2008-08-9.)
  9. Hydrogen safety aspects related to high pressure PEM water electrolysis [ permanent dead link ]
  10. 1 2 3 2005 DOE H2 Program Review Alkaline, High Pressure Electrolysis. (Available here Accessed 2008-08-9.)
  11. 1 2 Alkaline, High Pressure Electrolysis (Available here Accessed 2008-08-9.)
  12. Mitsubishi Monitor August and September 2004 (available here Accessed 2008-08-9.)
  13. "Forschungszentrum Jülich EKOLYSER Project" . Retrieved 27 May 2013.
  14. "Das Energiekonzept der Bundesregierung 2010 und die Energiewende 2011" (PDF). Archived from the original (PDF) on 2013-02-26.
  15. Carmo, M; Fritz D; Mergel J; Stolten D (2013). "A comprehensive review on PEM water electrolysis". Journal of Hydrogen Energy. 38 (12): 4901. doi:10.1016/j.ijhydene.2013.01.151.
  16. "Hydrogen Generator & CO2 Cell Technology".
  17. "Smart Hydrogen Station".