IIT Bombay
DESE
Solar Thermal Energy Conversion
Lecture #15
Autumn Semester Lecture 15: EN 601: Solar thermal energy conversion Slide 1
IIT Bombay
Concentrator geometry DESE
Aperture (W): The plane at the opening of the concentrator through which
solar radiation enters the concentrator
Concentration ratio (C): This is the ratio of the aperture to the area of the
absorber pate.
Intercept factor: This is the ratio of the incident radiation on the absorbober
plate after concentration to the actual incident radiation crosses the aperture
Acceptance angle: This is the measurement of the deviation in the incident
angle from the normal to the aperture area.
1 1
For line focus Cm , 2 D and point focus Cm , 3 D 2
sin a sin a
Autumn Semester Lecture 15: EN 601: Solar thermal energy conversion Slide 2
IIT Bombay
Central receiving power plant DESE
Central receiver
•Tower height- 80m
• Reflectic area- 71000 sq. m
• 1800 heliostat
• Steam as fluid
• 10MW
Rankine cycle
system
Autumn Semester Lecture 15: EN 601: Solar thermal energy conversion Slide 3
IIT Bombay
DESE
Solar-1, 10 MW plant
Autumn Semester Lecture 15: EN 601: Solar thermal energy conversion Slide 4
IIT Bombay
Pay back period DESE
• Energy pay back period
• Money pay back period
total energy required for the system
Energy pay back period =
annual energy conversion by the system
total investment
Money pay back period =
annual income from fuel saving
Autumn Semester Lecture 15: EN 601: Solar thermal energy conversion Slide 5
IIT Bombay
Pay back period DESE
• Payback period depends on which fuel of cooking you are replacing with solar
cooker, e.g. LPG, electric, coal etc.
• LPG energy content is (12.6kWh/kg*13.5kg/cylinder = 612360 kJ/cylinder)
• Heat energy required for cooking a single person is about 900 kJ
• Box type solar cooker can cook about 40% of food for 4 people, cost of box type
solar cooker is about 2000 Rs.
• Find out the money payback period?
Autumn Semester Lecture 15: EN 601: Solar thermal energy conversion Slide 6
IIT Bombay
DESE
Water heating
Pressure
cooking
Fraying
Ironing
Autumn Semester Lecture 15: EN 601: Solar thermal energy conversion Slide 7
IIT Bombay
Cooking by Scheffler disk DESE
Scheffler disk (parabolic disk) is used, requires tracking, focuses light into kitchen,
secondary reflector are used
Scheffler disc
(south facing)
Kitchen
sun-tracking
arrangement
secondary reflectors
Autumn Semester Lecture 15: EN 601: Solar thermal energy conversion Slide 8
IIT Bombay
Cooking by Scheffler disk DESE
Autumn Semester Lecture 15: EN 601: Solar thermal energy conversion Slide 9
IIT Bombay
Cooking by Scheffler disk DESE
Autumn Semester Lecture 15: EN 601: Solar thermal energy conversion Slide 10
IIT Bombay
DESE
Cocking vessels
Autumn Semester Lecture 15: EN 601: Solar thermal energy conversion Slide 11
IIT Bombay
Cooking by parabolic disk DESE
Solar Steam Cooking System for 15000
people (worlds largest)
Tirumala Tirupati Devasthanams (TTD)
Andhra Pradesh, India
Lecture 15: EN 601: Solar thermal energy conversion Slide 12
IIT Bombay
DESE
Cocker installed in Saidham
Autumn Semester Lecture 15: EN 601: Solar thermal energy conversion Slide 13
IIT Bombay
Concentrated collector: comparison DESE
Name of system Contributing Temp (oC) Efficiency
radiation (%)
Cylindrical parabolic Direct 100 to 400 50 - 60
collector
Parabolic point focus Direct Up to 1000 70-80
Autumn Semester Lecture 15: EN 601: Solar thermal energy conversion Slide 14
IIT Bombay
Performances: Flat plate collector DESE
40 %
30 %
12:00
Autumn Semester Lecture 15: EN 601: Solar thermal energy conversion Slide 15
IIT Bombay
Performances: Flat plate collector DESE
100 %
Relative insolation
0.9
0.8
90 %
0.7
80 %
0
70 %
0 10 20 30 40 50 60
Latitude
Autumn Semester Lecture 15: EN 601: Solar thermal energy conversion Slide 16
IIT Bombay
Performances: Parabolic concentrator DESE
90
I
Incident angle
II
60
III
30
IV
0 V
6:00 8:00 10:00 12:00 14:00 16:00 18:00
Time
Autumn Semester Lecture 15: EN 601: Solar thermal energy conversion Slide 17
IIT Bombay
Closed loop system DESE
Used when large amount of water heating is required Cold water tank
Insulated piping Temp
Water for
Collector array use
Temp Storage
tank
controller
Auxiliary
heater
pump
There can also be a open loop system
Autumn Semester Lecture 15: EN 601: Solar thermal energy conversion Slide 18
IIT Bombay
Closed loop system DESE
Low temperature system, medium temperature, high temperature systems
turbine
Heat
exchanger
Flat plate
collector Condenser
Storage
Storagetank
tank
Working fluid in
pump
Rankine cycle
pump
•Low temperature system, water as working fluid low efficiency, how much low?
•In medium temperature parabolic trough with other working fluid, higher efficiency
•Storage requirement can be avoided using solar pond concept
Autumn Semester Lecture 15: EN 601: Solar thermal energy conversion Slide 19
