Hydrogen Economy

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Hydrogen Economy

• By Justin Hibbard

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Hydrogen Economy

• Ways to make hydrogen H2
• Steam Electrolysis - split water with heat,
  pressure and electricity
• Electrolysis - split water with electricity
• Direct Solar Thermal Water Splitting split
  water with heat
• Thermochemical split water using chemicals and
  heat
• Biological splitting water using sunlight
  directly
• Steam Reforming convert methane in natural gas
  using steam
• Direct Thermal Splitting of Natural Gas split
  natural gas using heat
• Gasification breakdown coal or biomass with
  heat and pressure

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Hydrogen Economy

• Steam Electrolysis - split water with heat,
  pressure and electricity
• Could be attached to a nuclear power plant.

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Hydrogen Economy

• Electrolysis - split water with electricity
• 2H2O(l) ? 2H2(g) O2(g) E0 -1.229 V
• Need catalysts to lower energy

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Hydrogen Economy

• Direct Solar Thermal Water Splitting split
  water with heat

Water breaks down at 1700 C. Need ZrO containers
at high temperature. Use multiple reflection
devices and concentrate sunlight. No sunlight,
no energy production.
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Hydrogen Economy

• Thermochemical split water using chemicals and
  heat

• There are more than 200 thermochemical cycles
  which can be used for water splitting, around a
  dozen of these cycles such as the sulfur-iodine
  cycle
• The three reactions that produce hydrogen are as
  follows
• I2 SO2 2H2O ? 2 HI H2SO4 (120C)
• 2 H2SO4 ? 2 SO2 2 H2O O2 (830C)
• 2 HI ? I2 H2 (450C)
• Net reaction 2 H2O ? 2 H2 O2
• Best used with used by fission reactor

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Hydrogen Economy
Biological splitting water using sunlight
directly

• Algae convert
• Normally plants convert
• CO2 2H2O h? ? CH2O O2 H2O
• Algae engineered by Anastasios Melis, University
  of California, Berkeley
• O2 sensitive
• Design for less chlorophyll equals absorb less
  sunlight. That means more light penetrates into
  the deeper algae layers, and eventually, more
  cells use the sunlight to make hydrogen.

                                                                         
Algae power While regular green algae absorb most of the light falling on them (right), algae engineered to have less chlorophyll let some light through (left). When grown in large, open bioreactors in dense cultures, the chlorophyll-deficient algae will let sunlight penetrate to the deeper algae layers and thereby utilize sunlight more efficiently. Credit Anastasios Melis, University of California, Berkeley
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Hydrogen Economy

• Steam Reforming convert methane in natural gas
  using steam

• Steam reforming of natural gas or syngas
  sometimes referred to as steam methane reforming
  (SMR) is the most common method of producing
  commercial bulk hydrogen. At high temperatures
  (700 1100 C) and in the presence of a
  metal-based catalyst (nickel), steam reacts with
  methane to yield carbon monoxide and hydrogen.
  These two reactions are reversible in nature.
• CH4 H2O ? CO 3 H2
• CO H2O ? CO2 H2
• The efficiency of the process is approximately
  65 to 75.
• CO2 must be sequestered.

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Hydrogen Economy

• Direct Thermal Splitting of Natural Gas split
  natural gas using heat

• The Kværner-process or Kvaerner carbon black
  hydrogen process (CBH) is a method for the
  production of hydrogen from hydrocarbons (CnHm),
  such as methane, natural gas and biogas.
• (CnHm) energy ? nC m/2H2

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Hydrogen Economy

• Switching 100 percent of the algae's
  photosynthesis to hydrogen might not be possible.
  "The rule of thumb is, if we bring that up to 50
  percent, it would be economically viable," Melis
  says. With 50 percent capacity, one acre of algae
  could produce 40 kilograms of hydrogen per day.
  That would bring the cost of producing hydrogen
  to 2.80 a kilogram. At this price, hydrogen
  could compete with gasoline, since a kilogram of
  hydrogen is equivalent in energy to a gallon of
  gasoline.
• In 2000, Melis, working with researchers at the
  National Renewable Energy Laboratory (NREL),
  found that depriving the algae of sulfur
  nutrients forced the cells to make more hydrogen.
  The researchers were only able to deprive the
  algae of sulfur for a few days at a time, but
  during that time, about 10 percent of the algae's
  photosynthetic capacity went toward making
  hydrogen.
• Researchers at NREL are making progress in
  increasing hydrogen-production efficiency,
  according to lead researcher Michael Seibert.
  They can now force the algae to generate hydrogen
  for up to three months, as opposed to just a few
  days. Seibert expects that Melis's
  chlorophyll-trimmed algae will be useful when the
  process is transferred to large bioreactors.
  Until the NREL researchers test the mutant algae,
  though, he says that it may be too early to tell.

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Hydrogen Economy

• Gasification breakdown coal or biomass with
  heat and pressure

• Coal H2. During gasification, the coal is mixed
  with oxygen and steam (water vapor) while also
  being heated and pressurized. Also used for
  making fuel.
• (Coal) O2 H2O ? H2 CO
• CO H2O ? CO2 H2
• CO2 is sequestered.

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Hydrogen Economy

• Thanks to Rex A. Ewings book Hydrogen Hot Stuff
  Cool Science 2nd edition.