THE BIG PICTURE:
The free market would never use wind and solar power for electricity, because they are low density energy sources, intermittent, unreliable, inefficient, expensive, and require 100% fossil fuel backup
Fossil fuel pollution has been significantly reduced by technology: Catalytic converters, smokestack scrubbers, advanced engines, etc.. CO2 is the staff of life on our planet, and our plants want much more CO2 in the atmosphere. But the benefits for plant growth -- faster, larger growth with lower fresh water requirements -- are not enough good news to offset real air pollution caused by burning fossil fuels WITHOUT modern pollution controls. Carbon dioxide, however, is not pollution. Declaring that CO2 is a pollutant, does not change reality.
A hydrogen economy producing energy in abundance is the latest 'green' dream. More like a nightmare. Unless you skip any thought about the large quantity of energy needed to produce hydrogen. And skip the enormous cost for hydrogen infrastructure. And skip the hydrogen handling with an unavoidable increase in risk from the extreme flammability and explosion risk of hydrogen.
It's true that hydrogen could be converted into a new hydrocarbon – a synthetic fuel. Doing that would add extra cost to the fuel, but avoid most extra costs for hydrogen infrastructure and the danger of explosions.You could make ammonia, avoiding the extreme flammability and explosion risk of hydrogen, but getting an extremely toxic and corrosive chemical.
Hydrogen's physical properties are incompatible with the requirements of the energy market. Most of hydrogen’s problems can't be solved by additional research and development. Even if oil had never been discovered, the world would use a synthetic hydrocarbon fuel, not
synthetic hydrogen.
Why is hydrogen no good? Because efficiency losses in hydrogen manufacture and transport are very high, and inherent to this element. The energy lost in power transmission, operation of oil refineries, and gasoline transport, is usually small -- less than 10% of the energy.
DETAILS:
Hydrogen has to be compressed or liquefied for storage and transport.
For an equivalent amount of low pressure storage and transport, facilities for handling hydrogen are three times larger than the same energy content of methane gas. Liquid hydrogen must be kept in high technology pressure tanks, or cryogenic vessels -- liquid hydrocarbon fuels are kept at atmospheric pressure, in simple containers.
Hydrogen can be made by electrolysis of water, which is 75% efficient, or by steam reforming of natural gas, with 90% efficiency. More expensive for “clean hydrogen”, where no fossil fuels or nuclear energy is used. Producing 1 kg of hydrogen requires 50–55 kWh of electricity. At best, "clean hydrogen" could be produced for US$8.00/kg, not including the capital costs of the electrolysis infrastructure.
Ten times as much energy is required to compress hydrogen as the same weight of methane gas, needing energy equivalent to 7.2% of hydrogen's heating value. Liquefying hydrogen is highly energy intensive, using at least 28% of the energy contained in the hydrogen. (Liquefying methane gas takes only 6% of the energy contained in the methane). Storing hydrogen as a metal hydride of alkali metals is comparable to hydrogen compression in terms of energy consumption.
Existing natural gas pipelines can't be used for hydrogen, because of diffusion losses, brittleness of the materials and seals, incompatibility of pump lubrication with hydrogen, and other technical issues. Because of the low energy density of hydrogen, the flow velocity must be increased by over three times in a pipeline delivering hydrogen, compared to methane. In a natural gas pipeline, 0.3% of the contained energy of the transported gas is used every 150 km to run the compressors. In a hydrogen pipeline, this rises to 1.4% every 150 km.
Delivering hydrogen by pipeline is energy-intensive. Distributing it by trucks on the road is risky. A 40 ton truck could deliver 25 tons of gasoline, 3.2 tons of methane, but only 320 kg of hydrogen (due to the low energy density of hydrogen, and the weight of the pressure vessels).
A mid-size gasoline filling station on a freeway sells 25 tons of fuel each day. This can be delivered by one 40 ton truck. But it would need 21 hydrogen trucks to deliver the same amount of energy. About one percent of one hundred trucks on the road are gasoline or diesel tankers. You'd need twenty one percent of one hundred trucks on the road for hydrogen only. And trucks do sometimes have accidents!.
How about generating hydrogen at filling stations by electrolysis, and then compressed to 200 bars? Eliasson and Bossel calculated for a station servicing 1,000 vehicles per day, the efficiency of conversion of the electric power required would be about 50%, requiring power generation capacity to be tripled.
EFFICIENCY LOSSES FOR
MAKING & USING HYDROGEN:
A consequence of all
the efficiency losses
combined, is practical
hydrogen applications
end up at only 20% to 30%
chain efficiency.
Hydrogen is a very
immature technology,
so the efficiencies
that follow are
theoretical:
-- Large scale electrolysis
in use today operates at
close to 60-65% efficiency.
Electrolysis is
cheaper at scale,
but only up to about
1000 tons/day,
after which the
cost per kg
stays the same.
-- Steam reforming,
which makes up a
bout 80% of hydrogen
production today,
is done at around
75% efficiency.
Hydrogen losses,
in the chain
from energy input, to
usable energy output,
include the following:
-- Conversion loss
in electrolysis (35%),
or steam reformation
of natural gas (25%).
-- Conversion loss
in compression:
8% (200-300 bar),
10% (700 bar),
15% (liquid)
-- Loss in storage,
transportation and
bunkering / filling: 10%
-- Loss in use:
Fuel cell 50%
Large scale
PEM fuel cells
for heavy transport
applications operate
at under 50% efficiency.
A survey done by the
European Maritime Safety
Agency, looking at the
maritime applications,
estimated efficiency
at 45%.
Any time you hear
that fuel cells operate
at 60% efficiency,
that does not count any
systems needed to keep
the fuel cell running.
TOTALS:
The chain efficiency
from energy input
to useful energy
output is:
For steam reforming:
0.75*0.92*0.90*0.5 =
31% @ 200 bar,
30% @700 bar and
29% @liquid
For electrolysis:
27% @200 bar,
26% @700 bar and
25% @liquid