Guardian Weekly, Pierre Le Hir, Tuesday 28 February 2012
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| Island idyll ... stored energy from renewable sources would decrease Corisca's reliance on oil-fuelled power. Photograph: Murdo MacLeod |
As night
falls on the Gulf of Ajaccio, Corsica, the Iles Sanguinaires turn red in the
dying light of the sun. But it never really sets on the solar plant on the hillside
overlooking the Mediterranean.
Thanks to
the use of hydrogen, the electricity generated during the hours of sunlight can
be stored and injected into the power grid at any time of the day or night.
Though the Renewable Hydrogen for Grid Integration (Myrte) facility is still
experimental, it is already the largest of its kind in the world.
"The
problem of renewable-energy intermittence is particularly acute on
islands," said Philippe Poggi, a lecturer at Corsica University and one of
the driving forces behind the project, which also involves France's Atomic and
Alternative Energies Commission (CEA) and Helion, a subsidiary of Areva, the
nuclear power conglomerate, which specialises in hydrogen processes.
In Corsica
the 600 megawatts of installed power capacity are largely dependent on oil-fuelled
power stations, backed up by a hydroelectric plant and a power line running
across the seabed to Sardinia.
Solar and
wind power play a marginal part, but the island is keen to develop alternative
energy sources. However, as is the case for French overseas territories, a
ministerial decree caps the share of intermittent renewables in the overall
electricity supply at 30%. This precaution is designed to avoid the risk of an
outage caused by cloudy skies or a lull in the wind.
"The
only way round this limitation is to store solar energy," said Poggi. This
makes it possible to even out fluctuations in output and cope with sudden
spikes in demand.
The farm,
set in a hollow and partly grassed over, looks very much like a conventional
solar power facility, with a 3,700sqm array of photovoltaic panels. The novel
feature is an unobtrusive hydrogen plant, which contains all the smart bits.
Powered by
the current generated by the solar panels, an electrolyser splits water into
oxygen and hydrogen, which is stored in tanks at a pressure of 35 bar. When
required a fuel cell reunites the two elements in a reaction, generating
electricity that can be fed into the grid.
No single
step in this process is revolutionary. The difficult part is optimising the
whole process. For example, operation of the electrolyser must be adapted to an
intermittent power source. Similarly the fuel cell has to cope with the grid's
fluctuating demand. "The challenge is to find a mix that optimises all the
components," according to Poggi.
Corsica
sees itself as "a laboratory", setting an example of how the mainland
could follow once the system is fully operational.
Work on
Myrte started in 2006, with a €21m ($27m) budget funded by the regional
council, central government and the European Union. It has been up and running
for a few months and is still only at the stage of a small-scale test plant. If
it lives up to expectations, an industrial-scale unit will come online in
2014-15.
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