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Hydrogen is the most abundant element in the universe. Hydrogen is an
energy carrier - it contains the energy that powers the sun which sustains
all life on earth, and hydrogen is found in all living organisms. Hydrogen
is the first element in the periodic table. It is the lightest and simplest
element, and each hydrogen atom contains just one proton and one electron.
Hydrogen has the highest energy content of any common fuel by weight, but
the lowest energy content by volume, and as a result innovative hydrogen
storage technologies are required to store pure hydrogen in comparable
quantities to fossil fuels.
Hydrogen combines readily with other elements and it is not found on
earth in its pure form. When combined with oxygen the result is water, and
when combined with carbon - hydrocarbon fuels - such as ethanol, gasoline,
and coal. When hydrogen is combined with oxygen in a fuel cell, electricity
is produced, and the two elements combine to form water in an exothermic
reaction (i.e. heat is produced). The water is then usually emitted as a
waste product, although in some fuel cell systems the water is recycled
or utilised before being emitted.All fuel cells other than
Molten Carbonate Fuel Cells (MCFC) can run directly on pure hydrogen,
however
PEM fuel cells and
Alkaline Fuel Cells (AFC) can only run on very pure hydrogen. As hydrogen
is only found combined with other elements, it needs to be separated from
them in order to be useful as a fuel for fuel cells. hydrogen production.
- Electrolysis - separating water into hydrogen and oxygen
- Reforming - Separating hydrogen from gaseous and liquid hydrocarbon
fuels
- Gasification & Purification - Gasifying organic and plastics
materials into synthetic hydrogen-rich gases
- Anaerobic Digestion - Biological conversion of hydrocarbons
in the absence of oxygen - usually by bacteria
- Fermentation - Biological conversion of hydrocarbons, usually
by bacteria or yeasts
- Algae - certain algae emit hydrogen as a waste product from
their metabolism
If the electricity used to drive the electrolysis process is derived
from
Renewable / Alternative Energy Sources, the resulting hydrogen can be
called ‘renewable hydrogen’, and therefore carbon-neutral, thus not contributing
to the greenhouse effect and resulting global warming. Renewable hydrogen
can also be produced from gasifying biomass and other materials that do
not contribute to increasing overall carbon levels in the atmosphere.
Useful Hydrogen Information
1 kg = 11.13 N-m3 (at 0 degrees Celsius and 1 atmosphere)
| Thermodynamic Properties |
| Hydrogen Higher Heating Value (ÄH - Enthalpy) | –286 kJ/mol |
| Hydrogen Lower Heating Value ( ÄH - Enthalpy) | –242 kJ/mol |
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Energy content of 1 kg hydrogen
| 141.9 MJ (HHV) = 39.4 kWh |
| 120.1 MJ (LHV) = 33.3 kWh |
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of 1 N-m3 hydrogen
| 12.7 MJ (HHV) |
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of 1 pound of hydrogen
| 64.4 MJ (HHV) = 61.0 kBtu |
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of 1 gallon (3.8 Nm3) gasoline
| 121.3 MJ (LHV); 115,000 Btu (LHV)
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