Solar Energy Sem2
Hydrogen. Never alone naturally, always in combination with other elements.
The simplest and most abundant element on earth, But only occurs naturally in its gaseous state. What element and does it occur alone?
Heat
What is needed in all the reactions in both the steam-reforming and Water-gas shift reactions?
Hydrogen is produced by reacting coal with oxygen and steam under high pressures and temperatures to form synthesis gas, Then Added with steam to produce extra hydrogen and carbon dioxide, Hydrogen is removed in a seperation system, a highly concentrated CO2 stream can be captured and harnessed.
Explain the process of coal-gasification.
A process in which high temperature steam is used to produce hydrogen froma methane source, such as natural gas.
Explain what Steam-methane reforming is.
Biomass is converted into a gaseous mixture by applying heat under pressure with the presence of steam and a controlled amount of oxygen. The biomass is broken apart chemically, Setting in motion chemical reactions that produce synthesis gas, Adsorbers seperate the hydrogen from this gas stream.
Explain the process of biomass gasification.
Recycles. Biomass resources consume carbon dioxide in the atmosphere as part of their natural growth process.
Biomass _______ carbon dioxide. How?
Costs, and near zero greenhouse gas emissions.
Challenges are needed to be overcome in the coal gasification process to target what?
-Intesifying the process, Meaning combining steps. -DOE and USDA support
Describe a way to reduce both capital costs and to lower biomass feedstock costs of the biomass gasification process (Two descriptions)
-The electrolytic process uses electricity to split water into hydrogen and oxygen. -Like fuel cells, electrolyzers consist of an anode and cathode seperated by and electrolyte.
Describe the electrolytic process and how it works.
Hydrogen is produced from water using sunloight and specialized microorganism, such as green algae or cyanobacteria.
Describe the photobiological water splitting process.
Hydrogen is produced from using sunlight and specialized semiconductors called photoelectrochemical materials
Describe the photoelectrochemical water splitting process.
Water. Oxygen. Nuclear power, coal, natural gases, or renewable resources.
Hydrogen is a clean fuel, that when consumed for energy emits only ______ and ______. What is a domestic source that this energy can come from?
-Thermal processes- Steam reforming, gasification, and reforming renewable liquid fuels. -Electrolytic Processes- Seperates water into oxygen and hydrocarbon, Functions like a fuel cell in reverse. -Photolytic Processes- Uses light as the agent for hydrogen production. ( I.E. Green algae or Bacteria )
List and describe the most common methods of production of hydrogen fuel.
-Proton-Exchange membrane fuel cells- Use a fluorocarbon ion exhanged with a polymeric memberane as an electrolyte. -Direct-Methanol fuel cells- similar to PEM, however uses a catalyst on the anode to draw hydrogen from liquid methanol. -Alkaline fuel cells- uses and alkaline electrolyte such as potassium hydroxide. -Phosphoric Acid fuel cells- Anode and cathode finely dispersed platinum on a carbon paper and a silicon carbide matrix that holds the phosphoric acid electolye. -Molten Carbonate fuel cells- Use salt as their electrolyte, have the potential to be fueled with coal-derived fuel gases or natural gas and can be used for electrical utility. -Solid Oxide fuel cells- uses a thin layer of zirconium oxide as a solid ceramic electrolyte and include a lanthanum manganate cathode and nickel-zirconia anode. -Regenerative or reversible fuel cells- Produce electricity from hydrogen and oxygen but can be reversed and powered with electricity to produce hydrogen and oxygen.
List and describe the seven different types of fuel cells.
-Steam Reforming- Uses heat to create pure hydrogen by seperating it from hydrocarbons such as natural gas, coal methanol, or even gasoline -Gasification- technologies use coal or biomass to generate fuel gas that can also be reformed into hydrogen. -Reforming of renewable liquid fuels- similar to natural gas reforming, uses biomass-based liquid fuels as an energy source.
List and describe three thermal processes that are viable for near- and mid-term hydrogen production.
Hydrocarbons
Organic compounds such as gasoline, natural gas, methanol, and propane are called what?
-Alternative fuel technologies advanced for when supplies of limited resources run out. -Greenhouse gas emissions are lower then current fuels
What are two reason this technology is being considered for the hydrogen economy?
-Solar energy, and nuclear energy. -Near-zero greenhouse gas emissions.
What are two renewable resources that can be used for high-temperature water splitting? What does using these two accomplish?
-High-temperature water splitting is a thermalchemical process that uses temperature to split hydrogen and oxygen. -The closed loop is accomplished through reusing the chemicals within each cycle... Consuming water and producing hydrogen and oxygen.
What is High-temperature Water splitting? Explain the closed loop.
Reforming renewable liquid fuels is converting biomass resources into ethanol, bio-oils, or other liquid fuels. Yes, Transportation is cheap.
What is Reforming renewable liquid fuels and is transportation relatively cheap?
-A technology that can provide heat and electricity for buildings and electical power for vehicles. -Like batteries but they do not run down or need recharging.
What is a fuel cell? How do they work?
By converting the starch in corn into sugars and fermenting the sugar to produce ethanol.
What is a way that ethanol can be made using renewable liquid fuel reforming?
Is must be cost-competitive with the available alternatives. (ex. Petro, natural gas, propane)
What must happen in order for hydrogen to be successful in the market place?
95%
What percent of hydrogen produced today in the United States is made via steam-methane reforming?
Due to greenhouse gas emissions and energy-intensive nature of the electricy generation technologies used.
Why is the electrolytic process not ideal for todays electricity grid?
