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ME 417 Q3
| Question | Answer |
|---|---|
| hydroelectric power is known as what? | black start |
| What percentage of global energy demand currently comes from hydropower? | About 3%. |
| List advantages of hydropower. | Clean / non-polluting Renewable Abundant resource Can provide power to remote locations. Black start capability fast ramping for grid demand |
| Why isn’t hydropower used more widely? | High capital cost Environmental disruption Relocation of communities Aesthetic concerns Intermittent water supply Remote locations require transmission lines. Difficult maintenance |
| hydropower concerts _________ to _________ | motion to work |
| What does the basic turbine power equation in hydropower systems account for? | head minus friction and loss terms. |
| What is the definition of head in hydropower systems? | height difference between reservoir and exit. h=z(i)−z(e) |
| What is turbine head after losses? | The usable head after pipe and system losses. |
| What is turbine efficiency defined as? | The ratio of actual turbine output to ideal turbine output. ηT=isentropic turbine efficiency |
| How is real turbine head calculated? | Actual head multiplied by turbine efficiency. h(T,r)=h(T)η(T) |
| How is real turbine power calculated? | Real power equals real head × mass flow rate × gravity. W˙(T,r)=h(T,r)m˙g |
| What is “black start” capability? | The ability of a power plant to start generating electricity without external power. |
| What is the general turbine power equation used in the hydropower activity? | Turbine power equals gravitational potential energy of the flow minus system losses. W˙(T)=m˙gh−m˙(LOSSES) |
| What does the variable 𝑚˙ represent in hydropower equations? | Mass flow rate of the water. |
| What does ℎ represent in hydropower systems? | The head height, or elevation difference between reservoir and outlet. |
| What does the term “losses” represent in the turbine power equation? | Energy lost due to friction, pipe losses, and other hydraulic losses. |
| What does 𝑓(𝑗) represent in the head-loss equation? | The Darcy friction factor for pipe flow. |
| What does 𝐿(𝑗)/𝐷(𝑗) represent in the loss equation? | The pipe length-to-diameter ratio, used in friction calculations. |
| What do 𝐾(𝑗) values represent in fluid systems? | Minor loss coefficients for fittings, bends, valves, etc. |
| What does 𝜂(𝑇) represent in hydropower equations? | Isentropic turbine efficiency. |
| What equation describes the potential energy change from vertical water displacement? | Work equals mass flow × gravity × vertical displacement. W=ΔPE=m˙gΔz |
| What is the energy source for OTEC systems? | The temperature difference between warm surface water and cold deep ocean water. |
| Where are OTEC systems most suitable geographically? | Tropical ocean regions. large temperature differences between surface and deep ocean water. |
| what are characteristics about hydrogen? | smallest atom, in water, flammable --> highly combustible, storage is an issue, make bombs with it, most abundant element, diatomic, H2 splitting |
| Why is hydrogen called an energy carrier rather than an energy source? | Because energy must be used to produce hydrogen before it can store or deliver energy. |
| What types of resources can produce hydrogen? | Natural gas Renewable energy Nuclear energy Coal. |
| What industries commonly use hydrogen according to the diagram? | Petroleum refining Methanol production Electronics Ammonia production Metal fabrication Food processing Cosmetics. |
| What percentage of the universe is hydrogen according to the element abundance chart? | About 73.9%. |
| What is the physical state of hydrogen at room temperature? | Gas. |
| What particles make up a hydrogen atom? | One proton One electron. |
| What is “green hydrogen”? | Hydrogen produced by electrolysis using renewable electricity. |
| What is “grey hydrogen”? | Hydrogen produced from natural gas without carbon capture. |
| What is “blue hydrogen”? | Hydrogen produced from natural gas with carbon capture and storage. |
| What is “black hydrogen”? | Hydrogen produced from coal gasification. |
| What is “pink hydrogen”? | Hydrogen produced using nuclear-powered electrolysis. |
| What is “turquoise hydrogen”? | Hydrogen produced through methane pyrolysis. |
| What is “white hydrogen”? | Naturally occurring hydrogen found underground. |
| What does the map of the U.S. show regarding hydrogen resources? | Areas with potential natural hydrogen deposits (white hydrogen). |
| What is electrolysis? | Splitting water into hydrogen and oxygen using electricity. |
| What is the overall chemical reaction for electrolysis of water? | Water splits into hydrogen and oxygen gas. 2H(2)O→2H(2)+O(2) |
| What two electrodes are used in electrolysis? | Anode Cathode. |
| What is the most common hydrogen production method today? | Steam methane reforming (SMR). |
| What is the SMR chemical reaction? | Methane reacts with steam to produce hydrogen and carbon monoxide. CH4+H2O→CO+3H2 |
| What reaction releases energy when hydrogen is burned? | Hydrogen combustion producing water and heat. 2H2+O2→2H2O+energy |
| What makes fuel cells different from combustion engines? | They produce electricity without combustion. |
| What efficiency advantage do fuel cell vehicles have over internal combustion engines? | Internal combustion: 20–30% efficiency Fuel cells: ~60% efficiency. |
| Why are hydrogen vehicles considered clean? | They produce zero tailpipe emissions (water vapor only). |
| What practical advantages do hydrogen vehicles have? | Fast refueling Quiet operation Clean emissions. |
| What major facility uses large fuel cells for power generation? | Apple Campus 2 (4 MW of biogas fuel cells). |
| What does a fuel cell produce as outputs? | Electricity Water vapor Heat. |
| What enters the fuel cell? | Hydrogen gas (H₂) anode side, oxygen from air on cathode side |
| What type of current do fuel cells generate? | Direct current (DC). |
| What key components are shown in the PEM fuel cell diagram? | Anode Electrolytic membrane Cathode. |
| what are the two separate reactions in fuel cells? | oxidation & reduction |
| what is oxidation | half reaction (anode) |
| what is reduction | half reaction (cathode) |
| What moves through the external circuit in the PEM fuel cell diagram? | Electrons, producing direct current (DC) electricity. |
| What energy conversions occur in a fossil-fuel power plant according to the energy flow diagram? | Chemical energy → thermal energy → kinetic energy → electrical energy. |
| Why do fossil power plants have multiple losses? | Energy is lost during combustion, steam generation, and turbine operation |
| How does a fuel cell energy flow diagram differ from a fossil-fuel plant? | Fuel cells directly convert chemical energy to electricity without combustion or turbines. |
| What outputs are produced by fuel cells according to the diagram? | Electrical energy Thermal energy. |
| When hydrogen reacts with oxygen, what two forms of energy are produced? | Electricity Heat. |
| What reaction converts carbon monoxide to carbon dioxide while producing hydrogen? | The water-gas shift reaction. CO+H2O→CO2+H2 |
| Why is carbon capture often paired with hydrogen production from fossil fuels? | To reduce CO₂ emissions produced during hydrogen generation. |
| What technology is commonly used to capture CO₂ from flue gas? | Amine-based carbon capture (amine scrubbing). |
| What is the first step in the carbon capture diagram? | Flue gas from the plant is captured and directed into ducts. |
| What is the role of the absorber in carbon capture? | CO₂ binds to amine chemicals in the solution. |
| What happens in the regenerator (stripper)? | Heat separates CO₂ from the amine solution, creating a pure CO₂ stream. |
| What happens to captured CO₂ after separation? | It can be compressed and stored underground or transported for use. |
| What is electrolysis used for in hydrogen production? | Splitting water into hydrogen and oxygen using electricity. |
| What component converts fuel into hydrogen-rich gas before entering the fuel cell stack? | Fuel processor. |
| What component converts DC electricity from the fuel cell into AC power? | Power conditioner (inverter). |
| What is a fuel cell stack? | A series of individual fuel cells connected together to produce higher voltage and power. |
| What components are shown in the exploded fuel cell stack diagram? | Separator Flow plate Cathode Catalyst Electrolyte membrane Anode Cooling cell. |
| What electrolyte is used in molten carbonate fuel cells? | Molten carbonate salts. |
| What ion moves through the electrolyte in MCFC systems? | Carbonate ions (CO₃²⁻). |
| What does the term modular mean for fuel cells? | Fuel cells can be stacked or combined to scale power output. |
| What thermodynamic equation is shown on the slide related to hydrogen fuel cells? | The Gibbs free energy equation. ΔG=ΔH−TΔS |
| What does ΔG represent in the context of fuel cells? | The maximum useful electrical work obtainable from a chemical reaction. |
| Why is the Gibbs free energy equation important for hydrogen fuel cells? | It determines the maximum theoretical efficiency of converting chemical energy into electricity. |
| It determines the maximum theoretical efficiency of converting chemical energy into electricity. | Total enthalpy change (heat energy of the reaction). |
| What does the TΔS term represent? | Energy lost due to entropy (unusable energy). |
| Energy lost due to entropy (unusable energy). | Steam methane reforming (SMR) Electrolysis of water. |
| Why are hydrogen fuel cells considered efficient energy systems? | They convert chemical energy directly into electricity without combustion losses. |
| Why can hydrogen fuel cells be considered flexible energy systems? | they can be used in transportation, stationary power, and distributed energy systems. |
| According to the technology comparison table, how does green hydrogen perform in terms of physics efficiency? | Not very well compared to other technologies. |
| How does green hydrogen perform economically in the comparison table? | Not strongly competitive except for electrolyzers. |
| What geopolitical advantage does green hydrogen have? | It can enhance energy independence if produced domestically. |
| Why do hydrogen fuel cells require catalysts such as platinum? | To accelerate the electrochemical reactions at the electrodes. |
Created by:
mccurdyo