solar energy utilization - lecture 10-12 updated
DESCRIPTION
Solar TechnologyTRANSCRIPT
Solar Energy Utilization
ByDr. Khuram PervezAssistant Professor
Mechanical Engineering DepartmentMirpur University of Science and Technology
Equipment in solar energy system
Equipment in solar energy system
Equipment in solar energy system
What is a solar cell?
• Solid state device that converts incident solar energy directly into electrical energy
• Efficiencies from several percent up to 20-30%.
• No moving parts• No noise• Lifetimes of 30-40 years or more
PV Cells• Photovoltaic energy is the conversion of sunlight into
electricity. A photovoltaic cell, commonly called a solar cell or PV, is the technology used to convert solar energy directly into electrical power. A photovoltaic cell is a non mechanical device usually made from silicon alloys.
• Sunlight is composed of photons, or particles of solar energy. These photons contain various amounts of energy corresponding to the different wavelengths of the solar spectrum.
• When photons strike a photovoltaic cell, they may be reflected, pass right through, or be absorbed.
PV Cells
PV Cells
PV Cells
PV Cells
PV Cells
PV Cells
PV Cells
PV Cells
PV Cells
• Only the absorbed photons provide energy to generate electricity. When enough sunlight (energy) is absorbed by the material (a semiconductor), electrons are dislodged from the material's atoms. Special treatment of the material surface during manufacturing makes the front surface of the cell more receptive to free electrons, so the electrons naturally migrate to the surface.
• When the electrons leave their position, holes are formed. When many electrons, each carrying a negative charge, travel toward the front surface of the cell, the resulting imbalance of charge between the cell's front and back surfaces creates a voltage potential like the negative and positive terminals of a battery. When the two surfaces are connected through an external load, electricity flows.
How Solar Cells Work 1. Photons in sunlight hit the
solar panel and are absorbed by semiconducting materials, such as silicon.
2. Electrons (negatively charged) are knocked loose from their atoms, allowing them to flow through the material to produce electricity.
3. An array of solar cells converts solar energy into a usable amount of direct current (DC) electricity.
• The photovoltaic cell is the basic building block of a photovoltaic system. Individual cells can vary in size from about 1 centimeter (1/2 inch) to about 10 centimeter (4 inches) across. However, one cell only produces 1 or 2 watts, which isn't enough power for most applications.
• To increase power output, cells are electrically connected into a packaged weather-tight module. Modules can be further connected to form an array. The term array refers to the entire generating plant, whether it is made up of one or several thousand modules. The number of modules connected together in an array depends on the amount of power output needed.
• Photovoltaic Systems consist of several electronic components which work together to collect solar radiation and convert it into electricity.
– Collectors – Energy Storage System– Inverter – Distribution Center
Available Cell Technologies• Single-crystal or Mono-crystalline Silicon
• Polycrystalline or Multi-crystalline Silicon • Thin film– Ex. Amorphous silicon or Cadmium Telluride
Monocrystalline Silicon Modules • Most efficient
commercially available module (11% - 14%)
• Most expensive to produce
• Circular (square-round) cell creates wasted space on module
Polycrystalline Silicon Modules• Less expensive to make
than single crystalline modules
• Cells slightly less efficient than a single crystalline (10% - 12%)
• Square shape cells fit into module efficiently using the entire space
Amorphous Thin Film Most inexpensive technology
to produce Metal grid replaced with
transparent oxides Efficiency = 6 – 8 % Can be deposited on flexible
substrates Less susceptible to shading
problems Better performance in low
light conditions that with crystalline modules