CHEG 403: Innovative Low-Carbon Energy Systems
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Questions and Answers

What is the primary function of pumped storage hydropower?

  • To extract energy from tidal movements
  • To generate electricity during peak demand
  • To store electricity generated from solar panels
  • To pump water to a higher elevation during low demand (correct)

    • Which variable is NOT part of the hydropower output formula presented?

  • Temperature of water (correct)
  • Height of water head
  • Volumetric flowrate
  • Density of water

    • In relation to hydropower, what does the term 'total hydraulic head' refer to?

  • The overall height difference between two reservoirs (correct)
  • The energy required to operate hydropower plants
  • The density of the water flowing through the turbine
  • The total amount of water used in hydropower generation

    • What is the role of efficiency in the power output formula for hydropower?

    <p>It accounts for energy losses in the system (D)</p> Signup and view all the answers

    How much storage capacity does the DEWA Hydropower project in Hatta have?

    <p>1,500 MWh (A)</p> Signup and view all the answers

    What happens to the device current when it reaches the open-circuit voltage, VOC?

    <p>It ceases to produce a current (C)</p> Signup and view all the answers

    How is the open-circuit voltage, VOC, defined in the context of current?

    <p>It is the voltage at which the current is zero (B)</p> Signup and view all the answers

    What relationship defines the power output, P, in a solar cell?

    <p>P = I × V (C)</p> Signup and view all the answers

    What do the variables IM and VM represent in the context of solar cell efficiency?

    <p>Maximum current and voltage for maximum power output (C)</p> Signup and view all the answers

    What mathematical operation is applied to the power equation to find maximum power conditions?

    <p>Taking the derivative of P and setting it to zero (D)</p> Signup and view all the answers

    Which of the following variables is NOT included when calculating the open-circuit voltage VOC?

    <p>Voltage V (B)</p> Signup and view all the answers

    What must be true about current and voltage values IM and VM for the operation of the cell?

    <p>They must be less than or equal to VOC (D)</p> Signup and view all the answers

    In the equation for current, I, what is the primary factors affecting it?

    <p>Device parameter I0 and temperature T (D)</p> Signup and view all the answers

    What causes the dark current in a PV cell?

    <p>The potential difference from extra electrons and holes (D)</p> Signup and view all the answers

    What is the functional form of the dark current I?

    <p>I = I0 exp(eV/(mkT)) − 1 (B)</p> Signup and view all the answers

    At what condition is the minimum value of m attained for dark current?

    <p>Under ideal voltage conditions in full sunlight (C)</p> Signup and view all the answers

    How does the dark current affect the net current from the PV cell?

    <p>It opposes the light current (A)</p> Signup and view all the answers

    What is the short-circuit current (ISC) at V = 0?

    <p>ISC = IL (D)</p> Signup and view all the answers

    Which parameter in the dark current equation varies with operating conditions?

    <p>m (D)</p> Signup and view all the answers

    If the voltage of the PV cell is decreased, what happens to the value of m?

    <p>It becomes less than 1 (D)</p> Signup and view all the answers

    What is the effect of temperature on the dark current according to the equation?

    <p>Dark current increases exponentially with temperature (C)</p> Signup and view all the answers

    What is the value of the collection efficiency 𝜂"#$ (E) outside of the energy range of 1.89×10−19 to 5.68×10−19 J?

    <p>0% (A)</p> Signup and view all the answers

    What does the absorption coefficient 𝛼(E,W) account for in the operation of a solar cell?

    <p>Reflection and transmission losses (B)</p> Signup and view all the answers

    Which statistical function approximates the curve for the wavelength of arriving photons?

    <p>Weibull distribution (C)</p> Signup and view all the answers

    How is the light current IL generated in a photovoltaic cell mathematically represented?

    <p>IL = e * 𝜂&quot;#$ * S(E) * W * dE (A)</p> Signup and view all the answers

    What role does the term S(E) play in the calculation of light current IL?

    <p>It defines the frequency of arriving photons. (A)</p> Signup and view all the answers

    What is the value of the unit charge per electron, represented by 'e'?

    <p>1.6022 × 10−19 C (D)</p> Signup and view all the answers

    What happens to the collection efficiency of a solar cell as photon energy values become very high?

    <p>It decreases and approaches zero. (A)</p> Signup and view all the answers

    What is the absorption coefficient 𝛼(E,W) if reflection 𝜌(E) and transmission 𝜏(E,W) losses are both at their maximum?

    <p>0 (C)</p> Signup and view all the answers

    What are the two main routes for harvesting solar energy?

    <p>Solar Photovoltaic and Solar Thermal (D)</p> Signup and view all the answers

    What is the significance of the Mohammed bin Rashid Al Maktoum Solar Park?

    <p>It holds the record for the lowest solar energy cost. (C)</p> Signup and view all the answers

    What occurs at the p-n junction of a silicon-based photovoltaic cell?

    <p>Electrons are freed to create an electric current. (D)</p> Signup and view all the answers

    Which of the following statements about the bandgap energy is true?

    <p>It must be equal to or greater than the energy of the arriving photon. (B)</p> Signup and view all the answers

    What are the doping materials used in the upper and lower layers of a silicon-based PV cell?

    <p>Phosphorus for n-type and boron for p-type (D)</p> Signup and view all the answers

    Which physical constant is part of the equation for calculating the energy of a photon?

    <p>Planck's constant (B)</p> Signup and view all the answers

    What property of silicon layers enhances the production of loose electrons and holes?

    <p>Doping with materials (D)</p> Signup and view all the answers

    Which of the following best describes the effect of photons in a PV cell?

    <p>They excite electrons to break free and create electrical energy. (B)</p> Signup and view all the answers

    What percentage of Uranium 235 is required by the nuclear plant feed?

    <p>3% (A)</p> Signup and view all the answers

    How much Uranium 235 does each APR1400 reactor consume annually?

    <p>150,000 kg (C)</p> Signup and view all the answers

    What is the expected waste percentage by mass from a Uranium enrichment plant?

    <p>0.2% (A)</p> Signup and view all the answers

    Which enrichment process consumes the least amount of electrical energy per SWU?

    <p>Centrifuge (B)</p> Signup and view all the answers

    What is the annual operating cost of running one APR1400 nuclear plant?

    <p>457.50 million AED (A)</p> Signup and view all the answers

    What is the approximate electricity tariff in the UAE?

    <p>0.23 AED per kWh (B)</p> Signup and view all the answers

    How much Uranium 235 is necessary for the four reactors combined annually?

    <p>750,000 kg (A)</p> Signup and view all the answers

    What is the common process for Uranium enrichment that produces the highest electrical consumption per SWU?

    <p>Electromagnetic (A)</p> Signup and view all the answers

    Flashcards

    Solar Photovoltaic (PV) Technologies

    Methods that convert solar energy into electricity using the photoelectric effect.

    Solar Thermal Technologies

    Methods that convert solar energy into heat.

    Silicon-based PV cell

    A solar cell made from silicon.

    p-n junction

    A type of molecular structure in a solar cell where the upper n-type layer is doped with phosphorus, and the lower p-type layer is doped with boron.

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    Photoelectric effect

    The conversion of light energy into electrical energy.

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    Bandgap energy (EG)

    The minimum energy required to break free an electron from the solar cell structure.

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    Energy of a photon

    The energy of a wave calculated as: E = hc/λ, where h = Planck's constant, c = speed of light, and λ = wavelength.

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    Lowest Solar Energy Cost (Record)

    Achieved by the Mohammed bin Rashid Al Maktoum Solar Park in Dubai, at 0.06 AED per kWh.

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    Collection Efficiency (𝜂)

    The percentage of photons absorbed by the solar cell that release electrons, and thus contribute to the current.

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    Light Current (IL)

    The total current generated by a photovoltaic (PV) cell due to incoming photons.

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    Absorption Coefficient (α)

    Factor accounting for reflection and transmission losses in the solar cell, ultimately representing the fraction of light absorbed by the solar cell.

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    Photon Energy

    The energy of an individual photon of light.

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    Weibull Distribution

    A statistical function to describe the distribution of arriving photon energies, with single peak and zero possibility of negative values.

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    Solar Cell Efficiency

    How effectively a solar cell converts incoming light energy into electrical energy. Expressed as a percentage.

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    Absorption losses in PV cells

    Losses occur when photons are not absorbed by the solar cell material, reducing the amount of light current (IL).

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    Photons Arrival Rate (S(E))

    The rate at which photons arrive at the solar cell surface, as a function of photon energy.

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    Dark Current (ID)

    An additional energy loss in a PV cell due to the potential difference created between the n-type and p-type layers, regardless of sunlight.

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    Dark Current Formula

    ID = I0 * exp(eV / mkT), where: I0 = saturation current V = voltage m = a parameter based on device conditions k = Boltzmann constant T = temperature in Kelvin

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    Saturation Current (I0)

    The maximum current a PV cell can produce when the voltage is very high, essentially representing the maximum leakage.

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    Parameter 'm'

    Represents the steepness of the exponential relationship in the dark current formula, indicating how quickly ID changes with voltage.

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    Effect of Voltage on ID

    As voltage increases, the dark current (ID) also increases exponentially, due to the higher potential difference pushing more electrons across the junction.

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    Net Current in a PV Cell

    The difference between the light current (IL) and the dark current (ID): I = IL - ID

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    Short-Circuit Current (ISC)

    The maximum current a PV cell produces when the voltage is zero, equal to the light current (IL) since ID is negligible.

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    Why does ID matter?

    The dark current reduces the overall efficiency of a PV cell by 'stealing' current from the useful output. Engineers aim to minimize ID.

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    Open Circuit Voltage (VOC)

    The voltage across a solar cell when no current is flowing (open circuit). It represents the maximum voltage the cell can produce.

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    Equation for VOC

    The equation that relates Open Circuit Voltage (VOC) to the saturation current (I0), diode ideality factor (m), Boltzmann constant (k), and temperature (T).

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    Maximum Power Output

    The maximum power a solar cell can deliver, determined by the product of the current and voltage at its peak power point.

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    Maximum Current (IM) and Voltage (VM)

    The current and voltage at the maximum power output point of a solar cell. These values maximize the power output.

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    Derivative of Power Equation

    Setting the derivative of the power equation (P=IV) to zero helps find the maximum current and voltage (IM, VM).

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    Two Equations, Two Unknowns

    The maximum current and voltage values (IM, VM) are found by solving two equations: 1) the power equation derivative set to zero and 2) the current equation with IM, VM, and other constants.

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    Characterizing a Solar Cell

    Understanding the operating range (0 < V < VOC) and calculating current at any voltage using the current equation with given parameters (I0, m, T) allows us to characterize a solar cell's behavior.

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    Diversion Hydropower

    A type of hydropower that extracts energy from flowing water without creating a reservoir. This method involves drawing water through a turbine, generating electricity, and returning the water downstream.

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    Run-of-River Hydropower

    Similar to diversion hydropower, run-of-river hydropower generates electricity from the natural flow of a river with minimal impact on the river's flow. It uses low dams or weirs to channel water through turbines.

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    Pumped Storage Hydropower

    This type of hydropower stores energy by pumping water uphill to a higher reservoir during periods of low electricity demand. When demand increases, water flows downhill through turbines, generating electricity.

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    Hydropower Formula

    The power output of a hydropower system can be calculated using the formula: Power = (total hydraulic head) x (volumetric flowrate) x (efficiency). This formula considers the height of the water head, the amount of water flowing through the turbine, and the efficiency of the system.

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    DEWA Hydropower Project in Hatta

    This pumped storage hydropower project in Dubai, UAE, has a storage capacity of 1,500 MWh. It uses excess electricity to pump water uphill during low demand and releases the water downhill to generate electricity during peak demand.

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    Uranium Enrichment

    The process of increasing the concentration of the fissile isotope uranium-235 (U-235) in uranium ore, making it suitable for use in nuclear reactors.

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    Separative Work Units (SWU)

    A measure of the effort required to enrich uranium. It quantifies the work done to separate uranium isotopes.

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    What factors affect the cost of Uranium enrichment?

    The cost of Uranium enrichment depends on several factors, including the initial concentration of U-235 in the ore, the desired enrichment level, the enrichment technology used, and the cost of electricity.

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    How does electricity consumption impact Uranium enrichment?

    Different enrichment technologies consume varying amounts of electricity. For example, gas centrifuge technology is more energy-efficient than gas diffusion technology.

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    Waste in Uranium enrichment

    During the enrichment process, some uranium is lost or discarded as waste. The amount of waste is usually around 0.2% by mass.

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    Why is Uranium enrichment important?

    Uranium enrichment is essential for nuclear power generation because natural uranium contains only a small percentage of U-235, which is the fissile isotope required for nuclear reactions.

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    What is the total operating cost of one APR1400 nuclear plant per year?

    The total operating cost of one APR1400 nuclear plant per year is 457.50 million AED.

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    What is the electricity tariff in the UAE?

    The electricity tariff in the UAE is approximately 0.23 AED per kWh.

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    Study Notes

    Innovative Low-Carbon Energy Conversion Systems

    • Course: CHEG 403 - Fall 2024
    • Instructor: Faisal Abdulla AlMarzooqi
    • Date: October 18, 2024

    Solar Energy

    • Solar energy can be harvested via photovoltaic (PV) technologies (solar to electricity) or solar thermal technologies (solar to heat).

    Solar Photovoltaic Technologies

    • Mohammed bin Rashid Al Maktoum Solar Park in Dubai holds the world record for the lowest solar energy cost at 0.06 AED per kWh.
    • Solar photovoltaic technologies involve the conversion of solar energy into electricity.

    Best Research-Cell Efficiencies

    • Graph depicts advancements in solar cell efficiency over time.
    • Various technologies (e.g., crystalline silicon, III-V multijunction) are illustrated, showcasing improvements in efficiency through the years.

    Solar Photovoltaic Technologies - Fundamentals

    • Photons incident on a PV cell are converted to electrons through the photoelectric effect.
    • To facilitate this, silicon-based PV cells consist of two layers.
    • One layer (n-type) is doped with phosphorus (5 valence electrons).
    • The other layer (p-type) is doped with boron (3 valence electrons).
    • This structure is known as a p-n junction.

    Losses in PV Cells and Gross Current Generated by Incoming Light

    • Quantum losses occur when photon energy is less than the bandgap energy, preventing photoelectric effect.
    • Reflection losses represent the fraction of incident photons reflected from the surface of a PV cell.
    • Transmission losses occur when photons pass through the cell without interacting with atoms.
    • Collection losses occur when released electrons are reabsorbed within the cell structure.

    Losses in PV Cells (continued)

    • Collection efficiency (ηcol(E)) often falls to nearly zero at high photon energies owing to reabsorption.

    Calculation of Maximum Power Output

    • The maximum power output of a PV cell is calculated by taking the derivative of the power equation (P = IV) and setting it to zero.
    • Equations involve the current (Im), voltage (VM), saturation current (Io), light current (IL), and parameters relating to operating conditions.

    Solar Energy (Example 1)

    • The constant collection efficiency (ηcol(E)) is 95% and the absorption coefficient (α(E,W)) is 80%.
    • The photon arrival distribution S(E) follows a Weibull distribution (a = 3, β = 3).

    The Dark Current, ID

    • Dark current (ID) results from potential differences across layers (n-type and p-type).
    • ID = Io[exp(eV/(mkT))-1] where Io = saturation current, V = voltage, m is a value dependent on conditions operation, k = Boltzmann constant, T = temperature.
    • To simplify, m = 1 at ideal operating conditions, near maximum possible voltage.

    Wind Energy

    • Wind energy conversion involves transforming wind's kinetic energy into mechanical energy for electricity generation.
    • Wind speeds are classified into categories (e.g., Marginal, Fair, Good) based on values in m/s or mph. (Conversion table provided).
    • Wind energy is calculated using P=0.5pU^3 where p is air density and U is wind speed.
    • Rayleigh's probability distributions are to compute probability of wind speeds being at or below a given value.

    Hydropower

    • Hydropower utilizes energy stored in water flowing from a higher elevation to a lower elevation due to gravity.
    • Three types: Impoundment (dam-based), Diversion/Run-of-River, and Pumped Storage.
    • Hydropower output can be calculated using Power =(total hydraulic head) * (volumetric flowrate) * (efficiency).

    Nuclear Energy

    • Nuclear radiation involves Alpha, Beta, and Gamma rays and neutrons.
    • Nuclear energy involves fission (splitting of atoms) or fusion (combining atoms), releasing energy.
    • A fuel cycle is given for Uranium and examples of separating factors and required energies are given

    Nuclear Energy (The Nuclear Reactor)

    • Illustration of a simplified nuclear reactor layout, highlighting primary and secondary loops, steam generator, control rods, etc.

    Fundamental Sources of Energy Used by Different Energy Technologies

    • The fundamental principles of nuclear energy, including different categories such as fission and fusion, and their underlying reactions.
    • Categorization of different energy sources (solar, fossil, geothermal, etc.).

    Nuclear Science Revision

    • Defining atomic number (Z), atomic mass (A).
    • Explanation of isotopes and their significance
    • Mass defect (difference in mass between separate protons/neutrons and the assembled nucleus).
    • Calculation of nuclear masses using Einstein mass-energy equivalence (E = mc²).

    Reactions Associated with Nuclear Energy

    • Description of the nuclear fission process using U-235 as an example, including the release of neutrons and energy production.

    Uranium 235 enrichment

    • Methods of Uranium 235 enrichment including distillation, chemical exchange, gaseous diffusion, Gas centrifuge and aerodynamic enrichment.

    Separative Work Units (SWU)

    • A parameter used to evaluate capacity of an enrichment plant
    • V(x) = (1 − 2x) ln [ 1−x ] / x, where x is the composition.
    • Cost per year of SWU given (Example 5)

    Example 5 (U-235 Enrichment)

    • The cost estimation for U-235 enrichment and operation
    • The total operating cost of running one APR1400 nuclear plant.

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    Innovative Low-Carbon Energy Conversion Systems PDF

    Description

    This quiz covers innovative low-carbon energy conversion systems with a focus on solar energy technologies. You will explore photovoltaic systems, their efficiencies, and key advancements in the field. Join to test your understanding of solar energy fundamentals as discussed in CHEG 403.

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