### design and thermodynamical analysis of a solar updraft

```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