1. Renewable Energy Part 1 Professor Mohamed A. El-Sharkawi

2. Renewable Energy Solar Wind Fuel Cell Small Hydro Geothermal Tidal
Biomass

3. Solar Energy

4. Solar Power Density : solar power density on earth in kW/m2
o: extraterrestrial power density (1.353 kW/m2)
: zenith angle (angle from the outward normal on the earth surface to the center of the sun)
dt: direct transmittance of gases except for water (the fraction of radiant energy that is not absorbed by gases)
p: is the transmittance of aerosol
wa: water vapor absorptions of radiation.

5. Zenith Angle

6. Solar Energy (Whr/m2/day)

7. Daily Solar Power Density0%
20%
40%
60%
80%
100% 2 4 6 8 10 12 14 16 18 20 22 24
Time
Density ratio 2 s
t:hour of the day using the 24 hr clock
max: the maximum solar power density
to: time at max (noontime in the equator)
 : standard deviation

8. Solar Efficiency ()

9. Example An area located near the equator has the following parameters:
Assume that the standard deviation of the solar distribution
function is 3.5hr. Compute the solar power density and
solar efficiency at 3:00 PM.

10. Solution
At noon
At 3:00PM

11. Types of Solar Systems Passive Solar System
Active Solar System (Photovoltaic or PV)

12. New supply of cold water
Passive Solar System
New supply of cold water
Warm water to the house
Warm water
Lens
Tank
Sun rays
Collector
Cold water back
to solar collector

13. Passive Solar

14. Integrated Solar Combined Cycle System (ISCCS)
Receiver
Collector mirror

15. Integrated Solar Combined Cycle System (ISCCS)

16. Stirling System

17. Trough System

18. Solar Chimney

19. Active Solar Cell (Photovoltaic PV)

20. Silicon Silicon Atom Silicon Crystal Empty space for extra electron
Nucleus
Electrons
Empty space for extra electron
Silicon Atom
Silicon Crystal

21. Silicon Silicon is a good insulator
To make the silicon more conductive electrically, additives (impurities) are added (doping)
Phosphorus (P), which has 5 electrons in its outer shell
Boron (B), which has 3 electrons in its outer shell

22. P-N Material p-type n-type P B Electron without bondingSI P
Extra space for electron B
n-type
p-type

23. Lens I -
Load
N-Type -
P-Type
Base

24. Active Solar Cell (PV)
PV cell is built like a diode out of semiconductor material.
Sunlight is composed of photons, or particles of solar energy. Photons are the energy byproducts of the nuclear reaction in the sun.
When photons strike a PV cell, some of the photons energy is absorbed by the semiconductor material of the PV cell.

25. Active Solar Cell (PV)
With this extra energy, the electrons in the semiconductor material become excited and break lose, and eventually begin an electric current.
Because PV cells are built like diodes, free electrons are forced to flow in only one direction
the current is DC.

26. Main Parts of PV Glass cover or lens Antireflective coating
Contacts grid
n-type material
p-type material
Base

27. Structure of Solar System
PV cell: 4X4 inches. The cell can produce about 1 watt which is enough to run a calculator.

28. Structure of Solar System
Panel or Module: To increase its energy rating, the PV cells are connect together in parallel and series.
Parallel cells increase the current rating
Series cells increase the voltage rating.

29. Structure of Solar System
Array: PV panels connect together in parallel and series to form a high power system.

34. Example
Estimate the maximum power, current, and voltage ratings of the panel and array in the figure. Assume that each PV cell produce a maximum power of 2.5 W at the best solar conditions

35. Solution
The panel has 9 series cells. Assume that the voltage of each cell is 0.5 V, the total voltage of the panel is V
The panel has a total of 36 cells, the power of the panel is W

36. Total current of panel A
The array consists of 2 columns of 4 series modules.
The total voltage of the array is V
Total power of the array is W A

37. Computation of PV Energy
Solar power density

38. Computation of PV Energy
Linear relationship
Panel power
Solar power density
Panel Energy

39. Example
Compute the daily energy produced by a PV panel.
Solution Wh

40. Example
A 2 m2 panel of solar cells is installed in the Nevada’s area. The efficiency of the solar panel is 10%.
Compute the electrical power of the panel at 2:00PM when the solar power density is W/m2
Assume the panel is installed on a geosynchronous satellite. Compute its electrical power output.

41. Solution 1. 2.

42. Stand Alone PV System Converter House Solar array dc current
ac current
Charger
Discharger
Battery
Local load

43. PV System without battery
Solar array
House
ac current
Meter
To utility
dc current
Converter
Local load

44. Solar System With Battery
Battery: To store the energy when the PV power is not fully utilized by the load.
The battery power is later used when the PV power is less than the demand.
These batteries are deep cycle types
Charger: To charge the battery by the PV

45. Solar System With Battery
Inverter: To invert the dc power of the battery to the 60Hz power used in homes.
Synchronizer: Used to connect the PV system to the power grid.
DC/AC converter.

46. Ideal PV Model: P-N Junction
Anode (A)
Cathode (K) I Vd

47. Ideal PV Model: P-N JunctionR Vd Vs + - Vl Vd I
Forward biased region
Reverse biased region Io
Reverse saturation current

48. Ideal PV Model: P-N JunctionVd I
Forward biased region
Reverse biased region Io
Reverse saturation current
Io: reverse saturation current
VT: thermal voltage
q: elementary charge constant, i.e. charge of one electron ( Coulomb)
k: Boltzmann’s constant (1.380 x J/K)
T: absolute temperature in Kelvin (K).

49. PV Model I
Load V + -
The current I makes the upper terminal of the load positive with respect to the lower terminal
So the diode has a positive voltage on its anode wrt cathode.
This is a forward biased voltage which causes a forward current to flow back into the diode.
Now we have two currents in the circuit at the same time
current coming out of the diode due to the acquired energy by the PV Is
current going into the diode due to the positive polarity across the load Id

50. PV Model
P-Type
Base
N-Type
Lens - I
Load Id Is Id I
Load
V=Vd

51. PV Model Load V=Vd I Is Id Solar Cell
Is: the solar current (is a nonlinear variable that changes with light density (irradiance)
Id: the forward current through the diode.

52. Vd Is Id Io I QI
QII
QIII
QIV
PV Characteristics

53. PV Power CharacteristicsId I
Load
V=Vd
Solar Cell

54. PV Power Characteristics
Voc P
Pmax Vd I
Isc
Imp
Vmp

55. PV Power Characteristics
Main variables
Short Circuit Current (Isc)
Open Circuit Voltage (Voc)
Operating Point at Maximum Power (Pmax, Vmp, Imp)

56. Short Circuit PV Is
Id=0
Isc=Is

57. Open Circuit PV Is
Id=Is
Voc

58. Example
An ideal PV cell with reverse saturation current of 1nA is operating at 30oC. The solar current at 30oC is 1A. Compute the output voltage and output power of the PV cell when the load draws 0.5A.

59. Solution

60. Example
An ideal solar cell with reverse saturation current of 1nA is operating at 20oC. The solar current at 20oC is 0.8A. Compute the voltage and current of the solar cell at the maximum power point.

61. Solution
At maximum Power

62. Solution

63. Solution

64. Operating Point of PV
The operating point of the solar cell depends on the magnitude of the load resistance R
The load resistance is the output voltage V divided by the load current I.
The intersection of the PV cell characteristic with the load line is the operating point of the PV cell. Is Id I
Load
V=Vd
Solar Cell

65. Operating Point of PV
Voc V I R1 R2 R3
R1<R2<R3 1 2 3
Load lines

66. Example
For the solar cell in the previous example, compute the load resistance at the maximum output power.
Solution
From the previous example

67. Example
An ideal PV cell with a reverse saturation current of 1nA is operating at 30oC. The solar current at 30oC is 1A. The cell is connected to a 10 resistive load. Compute the output power of the cell
Solution

68. Iteratively, solve for V

69. Effect of Irradiance 
Voc V I
1<2<3 3 2 1 3 2 1
Load line

70. Effect of Irradiance  1 P V 2 3
1<2<3

71. Effect of Temperature T
Voc V I
T1>T2>T3 T3 T2 T1
Load line 1 2 3

72. Effect of Temperature TV T2 T3
T1>T2>T3

73. PV Module (Series Connection)
Is1
Id1 V1
Is2
Id2 V2
Load
Is=Is1=Is2
Load
V=Vd1+Vd2

74. PV Module (Parallel Connection)
Is1
Id1 V1
Is2
Id2 V2
Load
Is=Is1+Is2
Load
V=Vd1=Vd2

75. Example
An ideal PV module is composed of 50 solar cells connected in series. At 20oC, the solar current of each cell is 1A and the reverse saturation current is 10nA. Draw the I-V and I-P characteristics of the module.

76. Solution

77. Losses of PV Cell
Irradiance Losses
Electrical Losses

78. Irradiance Losses
Due to the reflection of the solar radiation at the top of the PV cell.
The light has photons with wide range of energy levels
Some don’t have enough energy to excite the electrons.
Others have too much energy that is hard to capture by the electrons.
These two scenarios account for the loss of about 70 percent of the solar energy

79. Losses of PV Cell (Electrical Losses)
The resistances of the collector traces at the top of the cell.
The resistance of the wires connecting cell to load.
The resistance of the semiconductor crystal

80. Real PV Model Rs : Resistance of wires and traces
To account for the electrical losses only Is Id I
Load V
Solar Cell Vd Rs Rp Ip
Rs : Resistance of wires and traces
Rp : internal resistance of the cell

81. Efficiency of PV Cell

82. Example
A 100 cm2 solar cell is operating at 30oC where the output current is 1A, the load voltage is 0.4V and the saturation current of the diode is 1nA. The series resistance of the cell is 10 m and the parallel resistance is 1k. At a given time, the solar power density is 200W/m2. Compute the irradiance efficiency and the overall efficiency.

83. Solution Is Id I
Load V
Solar Cell Vd Rs Rp Ip

84. Solution Is Id I
Load V
Solar Cell Vd Rs Rp Ip

85. Solution Conclusion: Most of the losses are irradiance Rs Load Ip V RpIs Id I
Load V
Solar Cell Vd Rs Rp Ip
Conclusion: Most of the losses are irradiance

86. Assessment of PV Systems

87. Solar Power and the Environment
6kW from a photovoltaic system instead of a thermal power plant can reduce annual pollution by
3 lbs. of NOx (Nitrogen Oxides),
10 lbs. of SO2 (Sulfur Dioxide), and
10530 lbs. of CO2 (Carbon Dioxide).

88. Assessment of PV Systems
Consumer products (calculators, watches, battery chargers, light controls, and flashlights) are the most common applications
Larger PV systems are extensively used in space applications (such as satellites)
In higher power applications, three factors determine the applicability of the PV systems
the cost and the payback period of the system
the accessibility to a power grid
the individual inclination to invest in environmentally friendly technologies.

89. Assessment of PV Systems
In remote areas without access to power grids, the PV system is often the first choice among the available alternatives.

90. Assessment of PV Systems
By the end of the 20th century, the PV systems worldwide had the capacity of more than 900 GWh annually
this PV energy is enough for about 70,000 homes in the USA, or about 4 million homes in developing countries.
The largest PV plant in the world is 60MW in Spain
75 MW PV plant is being built in Cle Elum, Washington

92. Assessment of PV Systems
To manufacture the solar cells, arsenic and silicon compounds are used
Arsenic is odorless and flavorless semi-metallic chemical that is highly toxic
Silicon, by itself, is not toxic. However, when additives are added to make the PV semiconductor material, the compound can be extremely toxic.
Since water is used in the manufacturing process, the runoff could cause these material to reach local streams
Should a PV array catch fire, these chemicals can be released into the environment.

93. Assessment of PV Systems
Solar power density can be intermittent due to weather conditions
PVs are limited exclusively to daytime use
For high power PV systems, the arrays spread over a large area.
The PV systems are considered by some to be visually intrusive
The efficiency of the solar panel is still low, making the system expensive and large
Solar systems require continuous cleaning of their surfaces