2-Solar Energy
Page 1: Introduction
Course Title: Advanced Energy Conversion Systems
Book: Solar Engineering of Thermal Processes 4th Edition by John A. Duffie and William A. Beckman, 2013.
Page 2: Sun-Earth Relationship
Travel Time: Solar energy takes 8 minutes and 20 seconds to reach Earth.
Effective Temperature: The sun has an effective black body temperature of approximately 5760 K.
Power Output: Total power output of the sun is 3.8*10^20 MW or 63 MW/m² radiated.
Energy Reception: Earth receives 1.7*10^11 MW.
Energy Equivalent: 84 minutes of solar radiation equals the world's annual energy demand of about 900*10^18 J.
Solar Constant: The solar constant Gsc (solar power per unit area just outside the atmosphere) is approximately 1366.1 W/m².
Angular Significance: The sun cannot be considered a point source, with a small angle 2qs = 0.5328 degrees being significant for collector optics.
Page 3: Solar Beams
Parallel Rays: Rays from the solar disk can be treated as parallel due to negligible angle x (error of order 10^-11).
Acceptance Angle: The sun's acceptance angle qs determines the angle under which radiation is accepted without moving collectors. The solar diameter is approximately 1.39*10^9 m, with a mean distance of 1.496*10^11 m.
Page 4: Solar Angles
Solar Altitude (α): The angle between solar rays and the horizon plane.
Zenith Angle (F): Complementary to the solar altitude.
Solar Azimuth Angle: The angle on the horizon between north and the projection of the sun's rays.
Solar Incidence Angle (θ): The angle between sun rays and normal to a tilted surface. For a horizontal plane, incidence and zenith angles are identical.
Page 5: Celestial Mechanics Elements
Definitions: Include latitude, longitude, horizon, zenith, azimuth angle, meridian, and vertical circles.
Observer Point (Q): Location from which observations are made.
Page 6: Equation of Time (ET)
Day Variation: Average day length is 24 hours, but varies due to earth's orbital eccentricity and axial tilt.
Timing Variability: Fastest orbit from October to March; slowest from April to September.
ET Formula:
ET = 9.87 sin(2B) - 7.53 cos(B) - 1.5 sin(B) (where B = N - 81 and N is the day of the year).
Page 7: Earth's Rotation and Revolution
Formula for Sun-Earth Distance R: [ R = a(1 , \pm , e) ] where a = mean distance (1.496 x 10^11 m), e = eccentricity (0.01673).
Orbital Cycle: Earth revolves around the sun every 365.25 days in an elliptical orbit, defining 1 astronomical unit (1 AU).
Aphelion: Maximum distance from the sun (~1.52 x 10^11 m, around July 3).
Perihelion: Minimum distance (~1.47 x 10^11 m, around January 2).
Equinoxes: Moment when day and night are of equal length - typically 12 hours each.
Page 8: Daily Variation of Solar Flux
Graphs: Illustrate daily solar flux variations at equinox, summer solstice, and winter solstice across 24 hours.
Page 9: Solar Radiation Definition
Source: Electromagnetic energy from the sun due to nuclear fusion.
Measurement Units: Joule (J) or Watt-hour (Wh).
Irradiance (G): Power per unit area (W/m²); Direct Normal Irradiance (DNI).
Irradiation (I): Energy received over time; integral of irradiance.
Page 10: Thermal Radiation Mechanism
Thermal Radiation: Emission dependent on the temperature of the emissive surface, travels at the speed of light.
Interaction with Surfaces: Upon incidence on a surface:
Reflectivity (ρ): portion reflected.
Absorptivity (α): portion absorbed.
Transmissivity (τ): portion transmitted.
Conservation: [ \rho + \alpha + \tau = 1 ] (angular and spectral properties depend on direction and wavelength).
Page 11: Blackbody Definition
Definition: An ideal absorber and emitter (α=1, τ=0, ρ=0).
Emissive Power:
[ E_{λ} = C1 \frac{λ^(-5)}{e^{(C2/λT)} - 1} ] where (E_{λ}) is monochromatic emissive power.
Wien’s Displacement Law: Maximum wavelength ( (λ_{max}T = 2897.8 μmK) ).
Page 12: Stefan-Boltzmann Law
Relation: Total emissive power and monochromatic emissive power defined by the Stefan-Boltzmann constant,[ E_{bl} = \sigma T^4 ].
Page 13: Radiation Intensity of Blackbody
Uniform Emission: Intensity of radiation is constant in all directions; communication model for real surfaces using emissivity (ε).
Kirchoff’s Law: Monochromatic emissivity equals monochromatic absorptivity in thermal equilibrium.
Page 14: Radiation Exchange Analysis
Radiosity (J): Total radiant energy exiting a surface, both original emission and reflection.
Equation: [ J = E_{bl} + ρG ], where G is incident irradiation.
Page 15: View Factor Definition
View Factor (F_{12}): Fraction of radiation from surface A1 that reaches surface A2.
Net Radiation Exchange: [ Q_{12} = E_{bl1}A1F_{12} - E_{bl2}A2F_{21} ].
Page 16: Extraterrestrial Solar Radiation
Spectrum: Emission approximated with black body spectrum at 5760 K.
Variables: Solar radiation spectrum affected by atmospheric conditions.
Page 17: Solar Constant and Variability
Solar Constant (Gsc): Measured as 1366.1 W/m².
Determinants: Variations exist based on earth-sun distance during perihelion and aphelion.
Page 18: Rate Calculation for Horizontal Surfaces
Rate on Extraterrestrial Horizontal Surface: [ G_{OH} = G_{0} \cdot cos(Φ) ].
Daily Total Radiation Calculation: Integrate over time from sunrise to sunset.
Page 19: Atmospheric Attenuation Factors
Attenuation: Solar heat reduced before reaching Earth due to atmospheric effects like scattering and absorption.
Page 20: Direct Normal Spectral Irradiance
Graph Representation: Illustrates the effects of atmospheric absorption on spectral irradiance vs. wavelength.
Page 21: Air Mass Concept
Air Mass (AM): Index for the atmospheric path length for solar rays reaching earth's surface; defined at different angles.
Page 22: Contributions to Radiation
Categories:
Direct Radiation: Straight from the sun.
Diffuse Radiation: Scattered from the sky.
Albedo Radiation: Reflected from surfaces.
Page 23: Influence of Atmospheric Conditions
Clarity Impact: Direct radiation diminishes with increasing humidity and cloudiness.
Page 24: Direct Normal Irradiance and Energy Context
Relevant Metric: Direct Normal Irradiance (H) as the primary metric for concentrated solar energy devices.
Page 25: H and Area Relationships
Density Connection: Variability of H across different latitudes and atmospheric conditions.
Page 26: Favorability of Locations
Best Locations: High DNI in regions like North Africa, Southwestern USA, etc.
Page 27: Energy Resource Mapping
Resource Areas: Maps illustrate potential CSP resource locations relating to solar radiation maps.
Page 28: H Map Analysis
Annual Solar Radiation Summary: H values categorized by energy received.
Page 29: Regional H Analysis in Europe
Regional Analysis: H values over European cities from 2004-2010.
Page 30: Monthly Average of DNI
Monthly Variation: Solar irradiance patterns over the year depicted in a time series plot.
Page 31: Radiation on Tilted Surfaces
Collector Orientation: Calculation of total solar radiation on tilted surfaces includes direct, diffuse and reflected components.
Page 32: PV Systems Overview
Overview: Introduction to PV systems related to solar technology.
Page 33: Photovoltaic Effect Definition
Semiconductors: Interaction of photons and silicon to create charge carriers.
Page 34: Doping in Silicon
Doping Process: Introduction of impurities to enhance semiconductor performance.
Page 35: Charge Carrier Dynamics
Flow of Charges: Mechanics of electron-hole pairs in PV cells.
Page 36: Layering in PV Cells
Cell Structure: Description of the layered structure and components of PV cells.
Page 37: Electrical Contacts in PV Cells
Contact Design: Balancing collection efficiency with light absorption.
Page 38: I-V Curve Basics
Characteristics: Understanding ISC and VOC for PV cells and their significance.
Page 39: Power Analysis in PV Cells
Power Characteristics: Definitions of maximum power point and fill factor in cells.
Page 40: Radiation and Temperature Effects
Temperature Impact: Assessment of the effect of temperature and radiation on current and voltage in PV cells.
Page 41: Series and Parallel Connections
Connection Types: How connections impact voltage and current capacities of solar panels.
Page 42: Efficiency Factors for Silicon Cells
Comparison of Cells: Measurements under standard conditions defining peak power and efficiency.
Page 43: Best Research-Cell Efficiencies
Research Insights: Overview of the current state of efficiencies across solar cell technologies.
Page 44: PV Module Composition
Construction: Multi-layered structure of traditional PV modules explained.
Page 45: Types of PV Technologies
Categorization: Overview of monocrystalline and polycrystalline technologies.
Page 46: Amorphous Silicon Discussion
Technology Profile: Comparison of efficiency and application of a-Si cells versus crystalline varieties.
Page 47: Sun Tracking Systems
Performance Enhancement: How tracking aligns with solar position to increase energy harnessing.
Page 48: Comparative Analysis
Device Comparisons: Side-by-side specifications of real-life PV devices.
Page 49: Efficiency Testing Overview
Testing Methodologies: Efficiency and fill factor tests illustrated through graphs.
Page 50: Concentrating PV Systems
CPV Principle: Explanation of energy concentration methods and cooling demands.
Page 51: Grid-Connected Systems
Key Components: Illustration of the key devices in grid-connected PV plants.
Page 52: Linking Cells to Modules
Connections: Explanation of how cells form modules and arrays.
Page 53: Inverter Functions and Specifications
Definitions: The role of inverters in grid systems with efficiency metrics.
Page 54: Grid Connection Systems
Connection Details: Overview of meters, connections, and safety features in grid setups.
Page 55: Sizing Considerations for PV Plants
Projection Basis: Guidelines for determining appropriate sizing based on demand.
Page 56: Sizing and Solar Radiation
Regional Input: Calculation guides for expected outputs based on environmental factors.
Page 57: Area Calculation for PV Arrays
Plant Area Estimations: Formula implementations for sizing and energy projections.
Page 58: Inverter Configuration
Sizing Specifications: Final adjustments for solar array connections to inverters based on specs.
Page 59: Iterative Process in Sizing
Design Iteration: Importance of recalculating plant outputs in sizing.
Page 60: Stand-Alone PV Plant Overview
Balance and Considerations: Main devices and considerations for off-grid systems.
Page 61: Battery Storage Systems
Storage Specifications: Overview of battery applications, advantages, and limitations in PV contexts.
Page 62: Battery Lifespan Considerations
Utilization Strategies: Notes on optimizing battery use for peak performance.
Page 63: Lithium Battery Developments
Technological Advances: Overview of increasing popularity and performance characteristics of lithium batteries.
Page 64: Lithium Battery Specifications
Market Options: Comparison of various lithium battery specifications and suppliers.
Page 65: Charge Controller Functions
Controller Role: Overview of charge controller functionalities and protection mechanisms.
Page 66: PV Array Capacity Sizing
Definitions: Guidelines for calculating optimal array size based on load requirements.
Page 67: Power Conditions in Sizing
Voltage and Power Derivations: Calculating daily power requirements based on current and efficiency variables.
Page 68: Storage Capacity Calculations
Capacity Requirement Estimations: Addressing desired energy output based on atmospheric conditions and operational data.
Page 69: Energy Availability Considerations
Calculation Frameworks: Specific considerations for energy availability and storage design based on weather.
Page 70: Temperature Impact on Storage Needs
Temperature Considerations: Analyzing how temperature affects capacity needs across seasons.
Page 71: Discharge Rate Analysis
Metrics: Understanding the dynamics of discharge rates and power management.
Page 72: Rate Factor Utilization
Calculations: Application of rate factors for improved storage system efficiency.
Page 73: Maximum Capacity Adjustments
Capacitying Adjustments: Addressing factors affecting maximum storage installations and recalibrating output.
Page 74: Array Configuration Considerations
Array Positioning: Steps for determining optimal array configuration based on climate and solar conditions.
Page 75: Peak Current Assessments
Calculations: Estimating peak output demands based on monthly solar radiation metrics.
Page 76: Voltage Requirements
Voltage Parameters: Ensuring efficient voltage management across various environmental conditions.
Page 77: Concluding Remarks on PV Sizing
Comprehensive Summary: Final considerations for PV array configuration with a focus on peak current and temperature impacts.