PV Energy

Question 1

What is a monocrystalline solar panel made of?

Answer 1

Pure silicon

Most expensive and 20% efficient.

Question 2

What is the efficiency range of Polycrystalline solar panels?

Answer 2

15 - 17% efficiency

Made from fragments of silicon crystals melted together.

Question 3

What is the efficiency of Thin Film solar panels?

Answer 3

11% efficiency

Cheapest panel and lightweight.

Question 4

briefly explain the properties of semiconductors

Answer 4

Material with electrical conductivity between that of a conductor and an insulator

1. energy bands - electrons occupy theses. Valence (holds electrons bound to atoms) Conduction (allows free movement of electrons)
2. band gap - energy difference between valence and conduction band. electrons cross

3.doping - adds impurities to enhance conductivity. n & p type.

Question 5

briefly explain how to two-junction layers of a pv cell work

Answer 5

PN Junction joins p & n semiconductors.

1. at the junction, electrons jump from n to p
2. delpletion region is created
3. sun hits cells
4. photons knock electrons loose
5. electric field pushes electrons to n & p side
6. this creates flow of current

Question 6

what is the building structure of a monocrystalline solar cell

Answer 6

• made from a single continuous crystal of silicon
• uniform black colour with rounded edge

Question 7

what is the building structure of a polycrystalline solar cell

Answer 7

• made from multiple silicon crystals melted together
  -blueish hue with fragmented mosaic like appearance

Question 8

what is the manufacturing process of monocrystalline cell

Answer 8

-crystal seed is slowly pulled from molten silicon to form single crystal
- complex and energy intensive process

Question 9

what is the manufacturing process of polycrystalline cell

Answer 9

-molten silicon poured into mold and allowed to solidify
- simple and cheaper

Question 10

what is the efficiency of a monocrystalline cell`

Answer 10

18 - 22%

Question 11

the band gap energy for pure crystalline silicon is 1 eV.

what wavelength does this correspond to?

Answer 11

E = hc / wavelength
calculate energy for band gap

ans= 1.24x10(-6) m

Question 12

given the band gap energy for amorphouse silicon of 1.8 eV

what wavelength does this correspond to?

Answer 12

calculate energy per band gap.
E=hc / wavelength

ans = 710 x10(-9) m

Question 13

if irradiance (G) on cell is measured to be 800 W/m^2 and ambient temperature is 25C.

calculate the cell operating temperature given the NOCT is 47C

Answer 13

T = Ta + C2*G

C2 = (NOCT-Ta) / G

ans = 47.4C

Question 14

what is Air Mass (AM)

Answer 14

ratio of path length of sunlight through atmosphere to shortest path

Question 15

What AM value results in a higher solar radiation level?`

Answer 15

lower AM value (AM1) results in higher solar radiation as sunlight travels shorter path, reducing scattering and absorption.

Question 16

For light wavelengths of (a) 0.2 μm, (b) 0.5 μm, and (c) 1 μm. Calculate the energy gap needed for an electron to move to a conduction energy band

Answer 16

a) 6.2 eV

b) 2.484 eV

c) 1.24 eV

E = hc / wavelength
E(J) = 1240 / wavelength (in nm)

Question 17

Determine the Air Mass of a solar radiation given the following Sun angle to the zenith: (a) 45. (b) 60. (c) 78. (d) 90.

Answer 17

a) 1.41

b) 2.0

c) 4.8

d) infinite

AM = 1 / cos(angle)