Hydrogen, the ultimate clean fuel, may not be very suitable as a conduit
of renewable energy because it is wasteful and there are better
alternatives, scientists said on Friday. One reason that hydrogen is
embraced by politicians like US President George W. Bush is that it
promises a source of power for cars and buildings that emits only water.
The drawback is that hydrogen must first be produced, requiring a
primary energy source, and this is where scientists see major obstacles. When environmentally friendly wind electricity is used
to generate
hydrogen, only one quarter of the energy generated by the wind turbine
is eventually used to move a car.
The rest is lost during transport and energy conversion, said Ulf Bossel
of the European Fuel Cell Forum, which held its annual fuel cell
conference in Lucerne, Switzerland this week. "With hydrogen energy you only have 25 percent efficiency to turn wind
power to (car) wheel power," he said. Its much more efficient to
transport that electricity directly into a car battery, via the grid,
and use 90 percent of its power," he told Reuters in a telephone
interview.
Hydrogen is being discussed at the conference because it is one of the
fuels for cells that can generate electricity and heat in an
electrochemical conversion. US President Bush said in April that hydrogen was the fuel of the
future. In meetings with US House and Senate leaders in May, the big
three US motor companies pushed for a scenario involving ethanol and
hydrogen fuel cell cars.
Even oil and gas giant Royal Dutch Shell has started a project in
Rotterdam to fuel city buses with hydrogen. Shell Chief Executive Jeroen
van der Veer said recently such projects are important to raise
awareness of alternative energy. Bossel said most renewable energy will be harvested as electricity
through wind and solar power and should be used directly.
BIODIESEL BETTER
But he accepted that todays economy is based on fuels and that cars
will need some form of liquid fuel for long journeys, rather than have
to recharge batteries every few hundred kilometres. Even when this liquid energy is harvested from biomass, it makes sense
to turn it into a biodiesel rather than hydrogen, said Wim van Swaaij,
professor of thermo-chemical conversion from Twente University in the
Netherlands.
Biofuels are easy to handle, like todays fuels. Hydrogen, in its pure
form, needs to be stored under high pressure which also consumes energy.
Biofuels themselves contain hydrogen but in a much more stable form. "Through steam reforming technology we can turn 40 to
50 percent of the
original fuel content in the biomass into biofuel. The percentage is
even higher for hydrogen, 50 to 60 percent, but we will also have to
store that hydrogen, and biofuels are the easiest and most efficient way
to store hydrogen," Van Swaiij said.
The carbon particles in the biofuel will not make a net contribution to
heating up the earth through the greenhouse effect if the fuel is
harvested from biomass, because the plants consume carbon dioxide as
they grow, Van Swaaij added. Bossel also said that producing hydrogen, either through electrolysis
using nuclear or renewable electricity, or refined from biomass or
fossil fuels, requires massive amounts of water. One kilogramme of
hydrogen requires nine litres of water. "To serve all planes at Frankfurt airport with hydrogen, we need 25
power plants of 1 Gigawatt and all of Frankfurt s current water
consumption," he said.
(Por Lucas van Grinsven,
Planet Ark, 10/07/2006)