# High-pressure electrolysis

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ITM Power's HGas electrolyser stacks, each operating at 80bar pressure

High-pressure PEM electrolyser.

**High-pressure electrolysis** (**HPE**) is the [electrolysis of water](/source/Electrolysis_of_water) by decomposition of water (H2O) into oxygen (O2) and [hydrogen](/source/Hydrogen) gas (H2) due to the passing of an electric current through the water.[1] The difference with a standard [proton exchange membrane (PEM) electrolyzer](/source/Proton_exchange_membrane_electrolyzer) is the [compressed hydrogen](/source/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](/source/Hydrogen_compressor) is eliminated, the average energy consumption for internal differential pressure compression is around 3%.[4]

## 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](/source/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](/source/Renewable_energy).[7] This then enables the ability to help with [grid balancing](/source/Grid_balancing) and [energy storage](/source/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](/source/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](/source/Hydrogen_safety) requirements.[9][10]

## Research

This article needs to be updated. Please help update this article to reflect recent events or newly available information. (January 2021)

The [US DOE](/source/United_States_Department_of_Energy) 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](/source/Gasoline_gallon_equivalent) 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](https://en.wikipedia.org/w/index.php?title=High-pressure_hydrogen_energy_generator&action=edit&redlink=1) (HHEG) project.[12]

The Forschungszentrum Jülich, in Jülich Germany is currently researching the cost reduction of components used in high-pressure [PEM electrolysis](/source/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

- [Regenerative fuel cell](/source/Regenerative_fuel_cell)

- [Electrochemical engineering](/source/Electrochemical_engineering)

- [High-temperature electrolysis](/source/High-temperature_electrolysis)

## References

1. **[^](#cite_ref-1)** ["High pressure electrolysis"](https://web.archive.org/web/20090502054121/http://www.risoe.dk/Risoe_dk/Home/Research/sustainable_energy/fuel_cells/projects/SERC/Meetings/~/media/Risoe_dk/Research/SERC/Documents/280808_project1.ashx). Archived from [the original](http://www.risoe.dk/Risoe_dk/Home/Research/sustainable_energy/fuel_cells/projects/SERC/Meetings/~/media/Risoe_dk/Research/SERC/Documents/280808_project1.ashx) on 2009-05-02. Retrieved 2009-01-06.

1. **[^](#cite_ref-2)** [2001-High pressure electrolysis – The key technology for efficient H.2](http://www.fz-juelich.de/scientific-report-2001/docs/patente/26_11600.pdf?web_session=e4af90eba1518be519b2c1b61fa42cfb)[*[permanent dead link](https://en.wikipedia.org/wiki/Wikipedia:Link_rot)*]

1. **[^](#cite_ref-3)** ["Investigations of hydrogen compressor based on proton exchange membrane"](https://web.archive.org/web/20110725225851/http://event08.ise-online.org/site/files/ise080562.pdf) (PDF). Archived from [the original](http://event08.ise-online.org/site/files/ise080562.pdf) (PDF) on 2011-07-25. Retrieved 2009-04-13.

1. **[^](#cite_ref-4)** [2003-PHOEBUS-Pag.9](http://www.fz-juelich.de/ief/ief-3/datapool/page/214/solar%20energy%2075%20469-478.pdf) [Archived](https://web.archive.org/web/20090327074743/http://www.fz-juelich.de/ief/ief-3/datapool/page/214/solar%20energy%2075%20469-478.pdf) 2009-03-27 at the [Wayback Machine](/source/Wayback_Machine)

1. **[^](#cite_ref-5)** [Prediction of production power for high-pressure hydrogen by high-pressure water electrolysis](http://cat.inist.fr/?aModele=afficheN&cpsidt=15701199)

1. **[^](#cite_ref-6)** [Differential pressure](http://www.hydrogen.energy.gov/pdfs/review08/pd_10_hamden.pdf)

1. **[^](#cite_ref-7)** ["Electrolyser Stacks | ITM Power"](https://web.archive.org/web/20130512160613/http://www.itm-power.com/tech/electrolyser-stacks/). Archived from [the original](http://www.itm-power.com/tech/electrolyser-stacks/) on 2013-05-12. Retrieved 2013-05-20.

1. **[^](#cite_ref-DOE2_8-0)** XI.13 High-Efficiency, Ultra-High Pressure Electrolysis with Direct Linkage to Photovoltaic Arrays (Phase II Project) ([Available here](http://www.hydrogen.energy.gov/pdfs/progress05/xi_13_jackson.pdf) [Archived](https://web.archive.org/web/20210421101128/https://www.hydrogen.energy.gov/pdfs/progress05/xi_13_jackson.pdf) 2021-04-21 at the [Wayback Machine](/source/Wayback_Machine) Accessed 2008-08-9.)

1. **[^](#cite_ref-9)** [Hydrogen safety aspects related to high pressure PEM water electrolysis](http://vgr.ing.unipi.it/ichs/fileadmin/user_upload/CD/PAPERS/12SEPT/2.1.73.pdf)[*[permanent dead link](https://en.wikipedia.org/wiki/Wikipedia:Link_rot)*]

1. ^ [***a***](#cite_ref-DOE_10-0) [***b***](#cite_ref-DOE_10-1) [***c***](#cite_ref-DOE_10-2) 2005 DOE H2 Program Review Alkaline, High Pressure Electrolysis. ([Available here](http://www.hydrogen.energy.gov/pdfs/review05/pd26_ibrahim.pdf) Accessed 2008-08-9.)

1. ^ [***a***](#cite_ref-DOE3_11-0) [***b***](#cite_ref-DOE3_11-1) Alkaline, High Pressure Electrolysis ([Available here](http://www.hydrogen.energy.gov/pdfs/progress06/ii_h_5_ibrahim.pdf) Accessed 2008-08-9.)

1. **[^](#cite_ref-Mitsubishi_12-0)** Mitsubishi Monitor August and September 2004 ([available here](http://www.mitsubishi.com/mpac/e/monitor/back/0408/news.html) Accessed 2008-08-9.)

1. **[^](#cite_ref-EKOLYSER_13-0)** ["Forschungszentrum Jülich EKOLYSER Project"](http://www.fz-juelich.de/iek/iek-3/EN/UeberUns/Kooperationen/EKOLYSER.html). Retrieved 27 May 2013.

1. **[^](#cite_ref-energiekonzept2010_14-0)** ["Das Energiekonzept der Bundesregierung 2010 und die Energiewende 2011"](https://web.archive.org/web/20130226222555/http://www.bmu.de/fileadmin/bmu-import/files/pdfs/allgemein/application/pdf/energiekonzept_bundesregierung.pdf) (PDF). Archived from [the original](http://www.bmu.de/fileadmin/bmu-import/files/pdfs/allgemein/application/pdf/energiekonzept_bundesregierung.pdf) (PDF) on 2013-02-26.

1. **[^](#cite_ref-carmo2013a_15-0)** Carmo, M; Fritz D; Mergel J; Stolten D (2013). "A comprehensive review on PEM water electrolysis". *Journal of Hydrogen Energy*. **38** (12): 4901. [Bibcode](/source/Bibcode_(identifier)):[2013IJHE...38.4901C](https://ui.adsabs.harvard.edu/abs/2013IJHE...38.4901C). [doi](/source/Doi_(identifier)):[10.1016/j.ijhydene.2013.01.151](https://doi.org/10.1016%2Fj.ijhydene.2013.01.151).

1. **[^](#cite_ref-16)** ["Hydrogen Generator & CO2 Cell Technology"](https://web.archive.org/web/20220115142303/https://global.honda/innovation/FuelCell/smart-hydrogen-station-engineer-talk.html). Archived from [the original](https://global.honda/innovation/FuelCell/smart-hydrogen-station-engineer-talk.html/) on 2022-01-15. Retrieved 2022-01-15.

1. **[^](#cite_ref-17)** ["Smart Hydrogen Station"](https://global.honda/innovation/FuelCell/smart-hydrogen-station-engineer-talk.html).

## External links

- [High pressure electrolyzer](http://ec.europa.eu/research/energy/pdf/efchp_hydrogen1.pdf)

- [EC-supported STREP program on high pressure PEM water electrolysis](http://www.cder.dz/A2H2/Medias/Download/Proc%20PDF/PARALLEL%20SESSIONS/%5BS05%5D%20Production%20-%20Water%20Electrolysis/14-06-06/393.pdf)

v t e Articles related to electrolysis / Standard electrode potential Electrolytic processes Betts electrolytic process Castner process Castner–Kellner process Chloralkali process Downs cell Electrolysis of carbon dioxide Electrolysis of water Electrowinning Hall–Héroult process Hofmann voltameter Kolbe electrolysis Hoopes process Dow process Bromine Magnesium Electrochemical fluorination Wohlwill process Materials produced by electrolysis Aluminium (extraction) Calcium metal Chlorine Copper Electrolysed water Fluorine Hydrogen evolution reaction Lithium metal Magnesium metal Potassium metal Sodium metal Sodium hydroxide Zinc See also Electrochemistry Gas cracker Standard electrode potential (data page) Electrology

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Adapted from the Wikipedia article [High-pressure electrolysis](https://en.wikipedia.org/wiki/High-pressure_electrolysis) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/High-pressure_electrolysis?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.