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4.1 Solar

Photovoltaics :

Solar Photovoltaic (PV) is a technology that converts sunlight (solar radiation) into direct current electricity by using semiconductors. When the sun hits the semiconductor within the PV cell, electrons are freed and form an electric current.

Solar PV technology is generally employed on a panel (hence solar panels). PV cells are typically found connected to each other and mounted on a frame called a module. Multiple modules can be wired together to form an array, which can be scaled up or down to produce the amount of power needed.
(Source : https://www.studentenergy.org/topics/solar-pv Links to an external site.)

The Earth intercepts a lot of solar power: 173,000 terawatts. That’s 10,000 times more power than the planet’s population uses. So is it possible that one day the world could be completely reliant on solar energy? Richard Komp examines how solar panels convert solar energy to electrical energy.

(Source : http://ed.ted.com/lessons/how-do-solar-panels-work-richard-komp)

Quiz : How much did you learn from this video?   

 

When sunlight hits a solar cell :

  • In each solar cell, there are two distinct layers of silicon. The p-type layer is doped with extra positive charge (holes), and the n-type layer is doped with extra negative charge (electrons).
  • Along with the extra electrons in the n-type layer and the extra holes in the p-type layer, both layers also contain electron-hole pairs close to the junction of the two layers.

  • When a photon hits the solar cell and strikes an electron-hole pair, the electron is knocked loose from its hole.

  • Because of the electrical field created by the materials, the electron tends to move back into the n-type layer with the other extra electrons, and the hole tends to stay in the p-type layer with the other extra holes.

  • As more photons knock apart the electron-hole pairs, a voltage is created between the two layers.
  • A wire connecting the layers allows electrons and holes to move back together and recombine, ready for the process to start again.

  • Meanwhile, that wire is attached to an external load. The movement of the electrons is harnessed as energy and directed elsewhere, ready to be put to use.
    (Source : http://www.nova.org.au/technology-future/solar-pv Links to an external site.)

For more basic theories of photostatic please also check Chapter 3.2 Semiconductor physics

 

The current solar cell inefficiencies released in 2016:

 (Source : http://www.nrel.gov/ncpv/ Links to an external site.)

The table that summarises the best reported measurements for cells and submodules under 1 sun (non-concentrator) please check Solar cell efficiency tables (version 47) Links to an external site.  
Solar Thermal :
Solar thermal technologies capture the heat energy from the sun and use it for heating and/or the production of electricity. This is different from photovoltaic solar panels, which directly convert the sun’s radiation to electricity.


There are two main types of solar thermal systems for energy production – active and passive. Active systems require moving parts like fans or pumps to circulate heat-carrying fluids. Passive systems have no mechanical components and rely on design features only to capture heat (e.g. greenhouses).
(Source : https://www.studentenergy.org/topics/solar-thermal Links to an external site.)

For the basic theories of solar thermal please also check Chapter 3.1 Thermodynamics

 

Recommended courses :

  • edX - Solar Energy
    "Discover the power of solar energy and learn how to design a complete photovoltaic system." 
    • Duration : 8 weeks, 8 hours per week
    • Free
    • The course must be followed during a given period, but self-pased.
    • Introductory level

 

  • MIT OpenCourseWare - Fundamentals of Photovoltaics
    "Fundamentals of photoelectric conversion: charge excitation, conduction, separation, and collection. Lectures cover commercial and emerging photovoltaic technologies and cross-cutting themes, including conversion efficiencies, loss mechanisms, characterization, manufacturing, systems, reliability, life-cycle analysis, risk analysis, and technology evolution in the context of markets, policies, society, and environment."
    • Course material, video lectures, tutorial videos, lecture notes and assignments.
    • Undergraduate/graduate level

 

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