In this video Dimitri describes how hydrogen from metals allows safe,
compact storage of hydrogen energy, and how it could be particularly
efficient when combined with high temperature power generation from
solid oxide fuel cells or gas turbines.
Background:
My research is concerned with the production of more sustainable
fuels made from energy sources and materials that can be sourced
locally. Sources of energy could include renewable power like wind,
tidal, solar etc., or waste (the energy content of municipal and
commercial waste produced in the UK amounts to a third of that
represented by our requirements for diesel and petrol).
Hydrogen can be produced from these sources of energy and these
materials, for example by using current to split water into hydrogen and
oxygen – a process known as'electrolysis'. From hydrogen, one can also
prepare convenient carbon-based liquid fuels like synthetic petrol or
diesel, provided that a source of carbon is available. Sources of carbon
could include carbon dioxide recovered from power plants, brewery,
cement works etc., and also synthesis gas derived from municipal solid
waste or biomass. The most efficient process from the point of view of
carbon and energy efficiency would combine hydrogen from electrolysis
with a source of carbon.
However, hydrogen is a gas of very low density (one petrol tanker
delivery would be replaced by 22 deliveries of hydrogen compressed at
200 atmospheres) and it is also hard to liquefy. This poses problems not
just if the hydrogen is to be used directly as a fuel. Synthesis of
most carbon-based liquid fuels like synthetic petrol or diesel requires a
steady supply of hydrogen, rather than the variable feed rate that
electrolysis can deliver, and where a suitable geological formation is
not available costly bulk storage of very large volumes of the gas would
be required to buffer the synthesis process.
One solution is to store the energy content of hydrogen rather than
hydrogen itself. We react the hydrogen with metal oxide particles, which
turns the oxides to metals. The resulting metal particles like this one
can be stored for use later. Here the test rig where we have been doing
this. When the energy is needed, reacting the metal sponge with steam
regenerates the hydrogen and the metal oxide particles. This process
allows safe, compact storage of hydrogen energy, for example in your
garage or basement of your house, and it could be particularly efficient
when combined with high temperature power generation processes like
solid oxide fuel cells and gas turbines.
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