Hydrogen Economy

1. Hydrogen Economy By Justin Hibbard

2. 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

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

4. Electrolysis - split water with electricity 2H2O(l) → 2H2(g) + O2(g) E0 = -1.229 V Need catalysts to lower energy Hydrogen Economy

5. Direct Solar Thermal Water Splitting – split water with heat Hydrogen Economy Water breaks down at 1700 C. Need ZrO containers at high temperature. Use multiple reflection devices and concentrate sunlight. No sunlight, no energy production.

6. 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 (120°C) • 2 H2SO4 → 2 SO2 + 2 H2O + O2 (830°C) • 2 HI → I2 + H2 (450°C) • Net reaction: 2 H2O → 2 H2 + O2 • Best used with used by fission reactor

7. Hydrogen Economy Biological – splitting water using sunlight directly • Algae convert • Normally plants convert • CO2 + 2H2O + hν → {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.

8. 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.

9. Hydrogen Economy • Direct Thermal Splitting of Natural Gas – split natural gas using heat • The Kværner-process or Kvaerner carbon black & hydrogen process (CB&H) is a method for the production of hydrogen from hydrocarbons (CnHm), such as methane, natural gas and biogas. • (CnHm) + energy → nC + m/2H2

10. 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.

11. 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.

12. Hydrogen Economy • Thanks to Rex A. Ewing’s book “Hydrogen Hot Stuff Cool Science 2nd edition”.