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?

It accounts for energy losses in the system Signup and view all the answers

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

1,500 MWh Signup and view all the answers

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

It ceases to produce a current Signup and view all the answers

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

It is the voltage at which the current is zero Signup and view all the answers

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

P = I × V Signup and view all the answers

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

Maximum current and voltage for maximum power output Signup and view all the answers

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

Taking the derivative of P and setting it to zero Signup and view all the answers

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

Voltage V Signup and view all the answers

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

They must be less than or equal to VOC Signup and view all the answers

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

Device parameter I0 and temperature T Signup and view all the answers

What causes the dark current in a PV cell?

The potential difference from extra electrons and holes Signup and view all the answers

What is the functional form of the dark current I?

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

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

Under ideal voltage conditions in full sunlight Signup and view all the answers

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

It opposes the light current Signup and view all the answers

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

ISC = IL Signup and view all the answers

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

m Signup and view all the answers

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

It becomes less than 1 Signup and view all the answers

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

Dark current increases exponentially with temperature 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?

0% Signup and view all the answers

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

Reflection and transmission losses Signup and view all the answers

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

Weibull distribution Signup and view all the answers

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

IL = e * 𝜂"#$ * S(E) * W * dE Signup and view all the answers

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

It defines the frequency of arriving photons. Signup and view all the answers

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

1.6022 × 10−19 C Signup and view all the answers

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

It decreases and approaches zero. 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?

0 Signup and view all the answers

What are the two main routes for harvesting solar energy?

Solar Photovoltaic and Solar Thermal Signup and view all the answers

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

It holds the record for the lowest solar energy cost. Signup and view all the answers

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

Electrons are freed to create an electric current. Signup and view all the answers

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

It must be equal to or greater than the energy of the arriving photon. Signup and view all the answers

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

Phosphorus for n-type and boron for p-type Signup and view all the answers

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

Planck's constant Signup and view all the answers

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

Doping with materials Signup and view all the answers

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

They excite electrons to break free and create electrical energy. Signup and view all the answers

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

3% Signup and view all the answers

How much Uranium 235 does each APR1400 reactor consume annually?

150,000 kg Signup and view all the answers

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

0.2% Signup and view all the answers

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

Centrifuge Signup and view all the answers

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

457.50 million AED Signup and view all the answers

What is the approximate electricity tariff in the UAE?

0.23 AED per kWh Signup and view all the answers

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

750,000 kg Signup and view all the answers

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

Electromagnetic Signup and view all the answers

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, I_D

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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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.