Solar Energy Flashcards
(25 cards)
What are the key energy transformations that occur in a solar power cell?
Photon energy, thermal energy, electrical energy
List three energy sources with a lower median power density (per unit area) than solar power.
Hydro, wind, geothermal
List four energy sources with a higher median power density (per unit area) than solar power.
Coal, oil, nuclear, natural gas
The first commercial solar plant was set up in Albuquerque, New Mexico. What was the power output of this plant?
5 MW
If the entire world’s surface was coated in solar panels, how long would it take for the sun to satisfy our annual energy demand?
1:24 h
Solar collectors are installed at an angle to maximize solar radiation ____ and minimize ____.
Maximize: intercepted/received. Minimize: reflection.
What are the main energy changes in (1) a thermal solar energy system, and (2) a photo-voltaic energy system?
(1) photon energy to heat
(2) photon energy to electrical energy
List three environmental factors that impact on the power output of a solar power plant.
Time of day, season, tilt of the earth
True/False: Silicon (Si) is an electrical insulator.
False: it is a semi-conductor.
List three reasons why silicon (Si) is used in solar cells instead of other semi-conductors.
Any 3 of: abundant, cheap, environmentally friendly, safe, easy to dope.
Here are three different equations for the energy of a photon. Which one of these equations is false?
(1) E = hv
(2) E = hλ/c
(3) E = hc/λ
Number (2). E = hλ/c is false.
Outline the physical mechanism that occurs in the photo-voltaic effect.
An incident photon impacts a surface electron and transfers its energy to that electron.
Which current type do solar cells generate?
DC (direct current)
How is a silicon solar cell doped?
Tiny concentrations of phosphorus and boron are added (1 part per thousand Si atoms).
Define: n-type and p-type silicon.
n-type silicon is doped with phosphorus and has an excess of electrons. p-type silicon is doped with boron and has electron holes.
What is a depletion zone in a solar cell?
Close to the p-n junction, where the electrons and holes combine. This area is neutrally charged.
How does the incidence of a photon create a current in a solar panel?
The photon’s energy separates electron-holes pairs in the depletion zone, creating a potential difference between the p-side and n-side, driving a current.
Which side of a solar panel should face the sun?
The n-type Si side (with excess electrons).
List three pros of solar power generation.
Any 3 of: renewable, easily connected to the grid, scalable, Si is abundant.
List three cons of solar power generation.
Any 3 of: inconsistency in cloudy weather, high installation costs, low efficiency (about 20%), panels may be damaged by extreme weather.
What is the standard efficiency range for a new solar photo-voltaic cell?
Between 21% and 23% (for new models)
Why are solar cells so inefficient?
Because silicon can only absorb a small piece of the spectrum of solar radiation
How can technology meet the increasing demand for solar power?
Larger cells, greater efficiency, less expensive devices
List 2 cons of floating solar farms.
Degradation of plastic bottoms, unknown effect on wildlife
