Solar Energy: Principles of Solar Thermal Technology and Working Principle of Solar Collector

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Principles of Solar Thermal Technology

  • Radiation: Infrared rays of longer wavelength are transmitted through thermal agitation of composing molecules
  • Conduction: Transfer of heat between two surfaces which are in direct contact with each other.
  • Convection: Heat transfer occurring in between two mediums.

Working Principle of Solar Collector

  • The solar energy passes through a glazed glass layer in a solar collector and is absorbed.
  • Reflectors/absorbers: aluminium or glass reflectors are the major types of reflectors used in solar collectors. The reflectivity of these collectors needs to be the highest as much as possible.
  • Receivers: these are used to collect the concentrated energy from the sun.
  • Concentration ratio (c. R.) Gives the strength of system for conversion with higher energy possibilities.

Principle of Energy Generation by Solar Photovoltaic

  • Photovoltaic effect is the principle over which solar photovoltaic works
  • Phenomenon where illumination of light of specific wavelength which produces electromotive force in the non-homogeneous material

Factors affecting electricity generation in solar PV cells

  • Temperature
  • Light (photon) incident upon it

Solar Pond

Two categories of solar ponds are

Non-Convecting Ponds

  • Salt-gradient pond- Body of saline where the concentration increases with depth, from a very low value at the surface to near saturation at the bottom.
  • Membrane pond- Inhibits convection by physically separating the layers with thin transparent membranes.

Convecting Ponds

  • Evaporative losses occur because of presence of cover over the pondีšs surface
  • Shallow solar pond where evaporation is hindered but convection is allowed

Principle of Non-Convective Solar Pond

  • Collection and storage
  • Extraction of thermal energy
Illustration: Principle of Non-Convective Solar Pond

Multiple Choice Questions

1. Transfer of heat between two surfaces which are in direct contact with each other is known as

  1. Radiation
  2. Conduction
  3. Convection
  4. Advection

Answer: b

2. In solar photovoltaics, junction voltage decreases with

  1. Increase of temperature
  2. Decrease of temperature
  3. No change of temperature
  4. None of the above

Answer: a

3. In solar pond, the salinity is higher at

  1. Upper convective zone
  2. Middle convective zone
  3. Lower convective zone
  4. None of the above

Answer: c

4. Which among the following helps in concentrating solar energy in solar collectors?

  1. Reflectors
  2. Absorbers
  3. Receivers
  4. Both a and b

Answer: c

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โœ Mayank