Metal hydride fuel cell
Encyclopedia
Metal hydride fuel cells are a subclass of alkaline fuel cell
s that are currently in the research and development phase. A notable feature is their ability to chemically bond
and store hydrogen
within the cell. This feature is shared with direct borohydride fuel cell
s, although the two differ in that MHFCs are refueled with pure hydrogen. Though the absorption characteristics of metal hydrides (around 2%) is far lower than sodium-borohydrides and other "light" metal hydrides (around 10,8%)http://www.findarticles.com/p/articles/mi_m3012/is_10_183/ai_109505535, prototypes have been claimed to demonstrate a number of interesting characteristics:
Metal hydride fuel cells are currently being researched by ECD Ovonics, as well as by the Japanese National Institute of Advanced Industrial Science and Technology
(AIST). Though similar, the two MHFC concepts use different catalysts.http://ovonic.com/PDFs/fuel_cell/fuel-cell-report_ovonic-fuel-cell_mar05_reprint.pdfhttp://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V3F-44PKMJ2-1&_coverDate=09%2F30%2F2002&_alid=426776402&_rdoc=1&_fmt=&_orig=search&_qd=1&_cdi=5729&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=970b74a00a609e7e2a5cdd1d5b3aa6a7
Thus far, neither research project has produced a demonstratable model outside of a laboratory - only publications and patents - and significant efficiency hurdles have yet to be overcome. The Ovonics and AIST metal hydride fuel cells claim current densities of only 250mA/cm2 and 20mA/cm2, respectively, versus typical PEMFC performance at 1A/cm2.
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...
s that are currently in the research and development phase. A notable feature is their ability to chemically bond
Chemical bond
A chemical bond is an attraction between atoms that allows the formation of chemical substances that contain two or more atoms. The bond is caused by the electromagnetic force attraction between opposite charges, either between electrons and nuclei, or as the result of a dipole attraction...
and store hydrogen
Hydrogen storage
Hydrogen storage describes the methods for storing H2 for subsequent use. The methods span many approaches, including high pressures, cryogenics, and chemical compounds that reversibly release H2 upon heating...
within the cell. This feature is shared with direct borohydride fuel cell
Direct borohydride fuel cell
Direct borohydride fuel cells are a subcategory of alkaline fuel cells which are directly fed by sodium borohydride or potassium borohydride as a fuel and either air/oxygen or hydrogen peroxide as the oxidant...
s, although the two differ in that MHFCs are refueled with pure hydrogen. Though the absorption characteristics of metal hydrides (around 2%) is far lower than sodium-borohydrides and other "light" metal hydrides (around 10,8%)http://www.findarticles.com/p/articles/mi_m3012/is_10_183/ai_109505535, prototypes have been claimed to demonstrate a number of interesting characteristics:
- Ability to be recharged with electrical energy (similar to NiMH batteriesNickel metal hydride batteryA nickel–metal hydride cell, abbreviated NiMH, is a type of rechargeable battery similar to the nickel–cadmium cell. The NiMH battery uses a hydrogen-absorbing alloy for the negative electrode instead of cadmium. As in NiCd cells, the positive electrode is nickel oxyhydroxide...
); - Low operating temperatures (down to -20°C);
- Fast kinetics;
- Extended shelf life;
- Fast "cold start" properties;
- Ability to operate for limited periods of time with no external hydrogen source, enabling "hot swapping" of fuel canisters.
Metal hydride fuel cells are currently being researched by ECD Ovonics, as well as by the Japanese National Institute of Advanced Industrial Science and Technology
National Institute of Advanced Industrial Science and Technology
The , or AIST, is a Japanese research facility headquartered in Tokyo, and most of the workforce is located in Tsukuba Science City, Ibaraki, and in several cities throughout Japan. The institute is managed to integrate scientific and engineering knowledge to address socio-economic needs...
(AIST). Though similar, the two MHFC concepts use different catalysts.http://ovonic.com/PDFs/fuel_cell/fuel-cell-report_ovonic-fuel-cell_mar05_reprint.pdfhttp://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V3F-44PKMJ2-1&_coverDate=09%2F30%2F2002&_alid=426776402&_rdoc=1&_fmt=&_orig=search&_qd=1&_cdi=5729&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=970b74a00a609e7e2a5cdd1d5b3aa6a7
Thus far, neither research project has produced a demonstratable model outside of a laboratory - only publications and patents - and significant efficiency hurdles have yet to be overcome. The Ovonics and AIST metal hydride fuel cells claim current densities of only 250mA/cm2 and 20mA/cm2, respectively, versus typical PEMFC performance at 1A/cm2.
See also
- Glossary of fuel cell termsGlossary of fuel cell termsThe Glossary of fuel cell terms lists the definitions of many terms used within the fuel cell industry. The terms in this fuel cell glossary may be used by fuel cell industry associations, in education material and fuel cell codes and standards to name but a few. –...
- Hydrogen technologiesHydrogen technologiesHydrogen technologies are technologies that relate to the production and use of hydrogen. Hydrogen technologies are applicable for many uses....