Catalogo Experimenta 06

INDEX SCIENTIFIC STUDIES
128
The combustible cells - that form the Stack, the heart of the
system, where hydrogen and oxygen are joined to generate
electricity – are placed under the loading platform of the
car: 360 cells in series, each of which gives a tension of 1.2
Volts. Between the front wheels an electric induction motor:
it has the shape of a cylinder functions with alternating current.
Under the boot behind there is a storage tank, where
the hydrogen is compressed at 350 atmospheres (contains 68
litres of gas for a weight of 1.6 kilos). Distributed around we
find numerous sub-systems: the separator hydrogen/water, the
exchanger, the starter motor, filters, the injection flute, devices
for safety sand control. In all about 50 auxiliary instruments, a
number which gives the idea of the complexity of it all.
The price? This is one of the most delicate points. Six hundred
thousand Euros, half for the combustible cells and half for
all the rest. We are speaking about a prototype; nearly every
piece has been specially built. So, a Kilowatt of power costs
5,000 Euros, already in small series it decreases to 3,000, with
mass production to 500. A petrol engine costs 50 Euros per
Kilowatt: hydrogen is already 10 times more expensive.
The spaces to improve however are wide. Today hydrogen technology
is at the level of an advanced artisan. We must think
about a lot of time: in 2010 the first fleet of cars and buses, in
2015 we will see a widespread development and will start to
spread the network of distribution of hydrogen, in 2020 hydrogen
in acquire a relevant part in the scenario of transportation.
In order to implement this scenario it is necessary to start
immediately with investments and research. The European
Union has a seven year programme ready with financing of
250 million Euros per year, to which should be added the
same amount from the private sector. This would be the minimum
to compete with the USA (three research programmes)
Japan, France and India (till now in conventional motors one
invests in research a sum 10 to 20 times more). But for now
the Commission has blocked everything. Italy, then, is in still
more difficulty because until now (summer 2006) it does not
have an energy plan nor a transportation plan.
How does a fuel cell function, that is to say a combustible
cell? A little bit like a Volta battery, there are a lot of elementary
cells connected in series. Each cell is composed of
a metal plate, an electrode, a catalyser membrane, another
electrode and another plate. This all has a thickness of half
a centimetre. Greater is the surface of the cell, more is the
power. The cost is high, above all because of the catalysers,
which are of a platinum base, a precious metal today so scarce
that it would not even be possible to start an industrial
production of fuel cells.
HOW TO FILL UP WITH HYDROGEN
The main problem is how to procure hydrogen. Hydrogen can
be obtained from methane with a process called reforming:
but like this we again depend on a non renewable fossil source
and the quantity of carbon dioxide that ends in the air
is only half the in comparison with simple combustion. One
could think of a treatment of bio combustibles such as ethanol
and methanol, but to make a litre of bio combustibles you
need a ton of water to irrigate the cultivation. Among the
biomass sources of hydrogen seaweed appears to be particularly
interesting. One can obtain hydrogen for electrolysis
from water separating in its molecule the atom of oxygen
from two atoms of hydrogen, but using electricity produced
by the present power stations we will have an intolerable waste
of energy and will not resolve the problems of pollution
and exhaustion of the fossil resources.
There remain two ways: make electrolysis out of water with
electricity produced by solar panels (as we have mentioned) or
otherwise splitting the molecules at a very high temperature
(around a thousand C°). The first solution without doubt is absolutely
the best for the environment, it requires a large development
of solar cells, which should become much more econo-