design and thermodynamical analysis of a solar updraft

Report
Bachelors’ Thesis
By
BABALEYE A. O.
© FH SCHMALKALDEN, DEPARTMENT OF MECHANICAL ENGINEERING
CONTENTS
 Introduction
 Seguence Of Operation
 Alternate Practical Applications
 Thermodynamics of the Robust Design
 Turbine Unit Design
 Humidity and Humidification Effects
 Results
 Recommendation
© FH SCHMALKALDEN, DEPARTMENT OF MECHANICAL ENGINEERING
2
Introduction
 Solar collector traps sun radiation to warm air in a greenhouse-like
membrane.
 The energy inherent in atmospheric air is harnessed to drive a turbine.
 The solar tower serve as an adiabatic duct and works according to the
”chimney effect”.
Source: MEF
© FH SCHMALKALDEN, DEPARTMENT OF MECHANICAL ENGINEERING
3
Sequence Of Operation


© FH SCHMALKALDEN, DEPARTMENT OF MECHANICAL ENGINEERING
4
Alternate Practical Applications
 Agricultural sustainability.
o Social benefit
 Enironmental safety
improvement.
 Co-generation purpose.
o Economic feasibility
© FH SCHMALKALDEN, DEPARTMENT OF MECHANICAL ENGINEERING
5
Thermodynamics of the Robust Design
 Energy Balance; Chimney effect: - = [ ℎ − ℎ
+
gH]
 Optimum Air Mass Flow:  = 1
2
2
−

2
+
2
2
3
− ( + )
 Desired Reversible Performance:  = 1
 Desired Irreversible Performance:  =

0

2
3
− ( + )
1

2 ( +)
−
3
(1+)
3 2
3 2
2

2
 Chimney Head Loss: ∆ =  −   =
 Humid Air Performance:  =  72   − 
1
2
+ (1 ℎ1 − 2 ℎ2 ) + 2 +
© FH SCHMALKALDEN, DEPARTMENT OF MECHANICAL ENGINEERING
6
Turbine Unit Design
 By the principle of flow
continuum;
 1 = 2
  1 1 =  2 2
 Unpertubed state;  = 
 1 = 32 ; tip-speed ratio
 1 . 32 = 2 2
 2 = √3. 1
Source: RRE note
© FH SCHMALKALDEN, DEPARTMENT OF MECHANICAL ENGINEERING
7
Humidity and Humidification Effects
 Humid air is lighter than dry air
 Humidified air tends to accelerate more than dry air.
 The updraft and turbulence is higher
 Humidification lowers the temperature of airstream and energy is lost.
 At elevated temperatures, humidity will improve the performance.
© FH SCHMALKALDEN, DEPARTMENT OF MECHANICAL ENGINEERING
8
Results
1120
900
1100
800
1080
700
Relative Power (KW)
(W/m^2)
1060
1040
1020
1000
600
500
Ideal Power
400
Actual Power
300
200
980
100
960
0
940
0
2000
4000
6000
8000
10000 12000
Air Mass Flow (Kg/s)
920
295
300
305
310
Tu (K)
315
320
325
© FH SCHMALKALDEN, DEPARTMENT OF MECHANICAL ENGINEERING
9
600
Po,ideal (KW)
500
400
300
200
100
0
295
300
305
310
315
320
325
Tu (K)
90000.00
80000.00
70000.00
m ̇ (kg/s)
60000.00
50000.00
40000.00
30000.00
20000.00
10000.00
0.00
295
300
305
310
315
320
325
Tu (K)
© FH SCHMALKALDEN, DEPARTMENT OF MECHANICAL ENGINEERING
10
1.800
1.600
1.400
50.00
1.200
ηII (%)
60.00
η (%)
40.00
1.000
0.800
0.600
30.00
0.400
20.00
0.200
10.00
0.000
0.00
0.00
0.00
20.00
40.00
60.00
m ̇ (kg/s)
20.00
40.00
60.00
m ̇ (kg/s)
80.00
100.00
Thousand
80.00
100.00
Thousand
1400
1200
9000
1000
Power (KW)
8000
(KW)
7000
6000
5000
4000
800
Humidity Power
600
Ideal Power
400
3000
2000
200
1000
0
273
0
0
5
10
15
20
25
30
293
313
333
Tu (K)
ω (%)
© FH SCHMALKALDEN, DEPARTMENT OF MECHANICAL ENGINEERING
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Recommendation
 Optimization should be directed towards increasing the enthalpy by ensuring ∆ is as
large as possible.
 The top of the tower can be coned such that external wind flow could aid hot air drag
from the tower.
 Perhaps, a second wind turbine could be coupled at the top of the tower to produce
additional updraft.
 The physical and chemical properties of the heat transfer fluid (such as density, specific
enthalpy, moisture content, velocity and mass flow) should be adequately exploited.
 The solar collector should be of superior quality with high concentration efficiency.
Since, it has been validated that, the heat exchanger would transmit heat of higher
intensity if its optical properties are advantageous.
© FH SCHMALKALDEN, DEPARTMENT OF MECHANICAL ENGINEERING
12
Thank you for listening!
© FH SCHMALKALDEN, DEPARTMENT OF MECHANICAL ENGINEERING
13

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