SOLAR CHIMNEY

1
SOLAR CHIMNEY

• Solar Energy I
• Physics 471
• 2001-02-1
• Instructor Prof. Dr. AHMET ECEVIT
• Presented by Yusuf SIMSEK

2

TABLE OF CONTENT
PAGE

• Introduction
  4
• The Collector
  7
• 2. Structure of the Collector
  8
• 3. Glazed Collector
  9
• 4. The Energy Storage in the Collector
  11
• 5. Chimney
  13
• 6. Solar Chimney Prototype at Manzanares (Spain)
  14
• 7. Turbines
  16
• 8. How Does Collector Work?
  17

3
9. Collector Efficiency
21 11. The Chimney

25 12. The Turbine
32
13. The Appropriate Charesteristic Curve
35 14. Typical Dymensions for
Solar Chimneys 38 15.
Termodynamics
39 16. Operation

41 17. Technical Data Quantities
42 18. Energy
Production Costs
44 19. Conclusion

47
4
1.INTRODUCTION
Solar chimney converts the solar radiation
into electricity. It consists of three simple
parts Glass roof collector
Chimney Turbine Basically, air is
heated by solar radiation under the glass roof
and it starts to move toward to the chimney.
Turbines which are placed at the base of the
chimney converts this mechanical power into
electricity (Fig. 1.).
5
A single solar chimney with a suitable
large glazed roof area and a high chimney can be
designed to generate 100 to 200 MW continously 24
h a day. Thus even a small number of solar
chimneys can replace a large nuclear power
station. Solar chimneys operate simply and have a
number of other advantages The
collector can use all solar radiation, direct and
diffused. Due to the heat storage system
the soalr chimney will operate 24h on pure solar
energy. Solar chimneys are particularly
reliable and not liable to break down, in
comparision with other solar generating plants.
Unlike conventional power stations (and
also other solar thermal power station types),
solar chimneys do not need cooling water.
6
Unlike conventional power stations (and
also other solar thermal power station types),
solar chimneys do not cooling water. The
building materials needed for solar chimney,
mainly concrete and glass, are available
everywhere in sufficient quantities. Even
in poor countries it is possible to build a large
plant without high foreign currency expenditure
by using their own resources and work forces
1.
7
2. The Collector
Collector is the part of the chimney that
produce hot air by the green house effect. It has
a roof made up of plastic film or glass plastic
film. The roof material is stretched horizontally
two or six meter above the ground. The height of
the roof increases adjacent to the chimney base,
so that the air is diverted to the chimney base
with minimum friction loss. This covering admits
the short wave solar radiation component and
retains long-wave radiation from the heated
ground. Thus the ground under the roof heats up
and transfers its heat to the air flowing
radially above it from the outside to the chimney
2.
Chimney
Collector
Fig. 1.Parts of the Solar Chimney
Turbine
8
3. Structure of the Collector The
structure of the collector changes to the
covering material we used. If we use plastic film
we can construct the skeleton by adjusting the
space between the rods as 6 meter. In this type
skeleton attaching plastic film is easy and it is
particularly suitable for very large collector
surface in remote places because of the small
quantites of the materials needed and low
transportation cost. The 45 000 m2 of the
prototype were covered with various plastic film
and glass to establish the optimum and cheapest
material in the long life term 3.
9
4. Glazed Collector A flate glazed roof
must have much more durable skeleton. Besause
glazing increases the mass of the roof. Its rods
are more stronger and they are attached like in
the picture below (Fig. 2.). A collector roof of
this kind has a very long lifespan. With proper
maintanence this can easilly be 60 years or more
4.
Fig. 2. Collector Glass Roof of Solar Chimney
Prototype at Manzanares from Inside
10
A flate glazed collector can convert up
to 70 of irratiated solar energy into heat,
dependent on air throughput, a typical annual
average is 50. Also the ground under the roof
provides natural energy storage
at no cost 5. Clearly, the temperature
increases towards to the tower and energy loss
increases near the chimney. We can increase the
ability of the collector roof by double glazing
about the tower (Fig. 3).
Fig. 3. Aerial View of Solar Chimney Prototype at
Dusk.
11
5. The Energy Storage in the Collector
Water filled black tubes are laid down side by
side on the black sheeted or sprayed soil under
the glass roof collector (Fig. 4). They are
filled with water once and remain closed
thereafter, so that no evaporation can take
place. The volume of water in the tubes is
selected to correspond to a water layer with a
depth of 5 to 20 cm depending on the desired
power output.
Since the heat transfer between black
tubes and water is much larger than that between
the black sheet and the soil, even at low water
flow speed in the tubes, and since the heat
capacity of water (4.2 kJ/kg) is much higher than
that of soil (0.75 - 0.85 kJ/kg) the water inside
the tubes stores a part of the solar heat and
releases it during the night, when the air in the
collector cools down 6.
12
Fig. 4Principle of heat storage underneath the
roof using water-filled black tubes.
13
6. Chimney
The chimney is the plants actual
thermal engine (Fig. 5). Its optimal
surface-volume ratio decreases friction loss and
makes it like a pressure tube. The upthrust of
the air heated in the collector is aproximately
proportional to the air temperature rise ?T in
the collector and the volume of the cchimney. In
a solar chimney the collector raises the
temperature of the air by about ?T 35oC. This
produce an updraught velocity in the chimney of
about V15m/s 7.
Fig. 5. Chimney
14
7. Solar Chimney Prototype at Manzanares (Spain)
(Fig. 6)
The sheet metal was only 1.5mm thick 150m
high 10m diameter The debt of beading was
150mm The sheets were abuted vertically at
intervals of 8.6m and shiftened every 4m by
exterior trussrirelers 8.
Fig. 6. Solar Chimney Prototype at Manzanares
15
chimney 195 m high and 10 m in diameter
surrounded by a collector 240 m in diameter.
Fig. 7. Prototype of the solar chimney at
Manzanares.
16
8.Turbines
The turbines, the air current is
converted into mechanical energy. The turbines
are always placed at a height of 9 meter at the
base of the chimney. According to the size of the
turbine, they placed horizontally (Fig. 8) or
verticaly (Fig. 9) and also the number of the
turbines can vary.
Fig. 9. Vertical
Fig. 8. Horizontal
17
9.How Does A Collector Work?
When solar radiation pass through the
transparent roof it is absorbed by the ground
elements and it converts into heat energy. When
air is heated it starts to rise up and, starts to
move toward the chimney and gains a velocity
(Fig. 10).
Fig. 10. Solar Chimney Power Plants
A solar chimney collector converts
available solar radiation G onto the collector
surface Acoll into heat output. Collector
efficiency ncoll can be expressed as ratio of
the heatoutput of the collector as heated air Q
and the solar radiation G (measured in W/m2)
times Acoll9.
18
Heat Output
Collector Efficiency
Solar Radiation
Collector Area
19
Spesific heat capacity of the air
The temperature differences between the collector
and out flow
Mass flow
20
Air speed at collector outflow/chimney inflow
Chimney cross-section area
Spesific dendsity of air at temperature To ?T
at collector outflow/chimney inflow
21
10. Collector Efficiency
22
Additionaly valid for heat balance collector
Effective absorption coefficient of the collector
Loss correction value (in W/m2K), allowing for
emission and convection loss
Thus collector efficiency can also be expressed
like this
23
In order to find velocity
24
These equations are independent of roof height
because friction loses and ground storage in the
collector area neglected.
Typical Values
0.75-0.8 5-6 W/m2
G1000 W/m2 ?T300C
62
25
11.The Chimney
The efficiency of the chimney (i.e. The
conversion of heat into kinetic energy) is
particularly independent of the rise of air
temperature in the collector it is essentially
determined by the outside temperature To at
ground level (the lower the better). Thus solar
chimneys can make particularly good use of the
low rise in air temperature produced by heat
emitted by the ground during the night and even
the meager solar radiation of a cold day.
Comparing with the collector and turbine, the
chimney efficiency is relativelly low, hence the
importance of size in its efficiency curve. For
example, at a height of 1000 meters, chimney
efficiency is somewhat greater than 3 10.
26
Outher air is cold relative to the air inside the
chimney
Pressure in outher enviroment is different from
the inside the chimney.
HC
T0
P(pressure) under the gravity changes with
respect to
h
Fig. 11 Chimney Height
in differatial form
g acceleration due to gravity HC Chimney
height density
And
27
Air density in outer environment
HC
Air density in the chimney
Fig. 11 Chimney Height
Out of the chimney Inside of the chimney
28
Thus ?Ptot increases with chimney height. ?Ptot
is consist of two components
?Ptot ?PS?Pd
(dynamic and static)
The static pressure difference drops at the
turbine, the dynamic component describes the
kinetic energy of the air flow.
so
?Ptot?Pd
?PS O
Ptot ?ptotVC,max AC
Efficiency of the chimney can be established
volume
Power
29
Actual division of the pressure
difference into a static and a dynamic component
depends on the energy taken up by the turbine. If
the turbine is left out, a maximum flow speed of
VC,max is achieved and the whole pressure
difference is used to accelerate the air.
Toricelli Equation
T0 ambient temperature at ground level ?T
Temperature rises between collector inflow and
collector outflow /chimney inflow
30
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31
This basic simplified explanation one of
the basic charesteristic of the solar
chimney,which is that the chimney efficiency is
fundamentaly dependent only on chimney height.
Flow speed and temperature rise in the collector
do not come into it.
Thus the power contained in the flow
32
12.The Turbine Turbine in a solar chimney
do not work with staged velocity like a
free-running wind energy converter, but as a
closed pressure-staged wind turbogenerator, in
which, similarly to a hydroelectric power
station, static pressure is converted to
rotational energy using a cased turbine- in this
aplication installed in a pipe. The energy yield
of a cased pressure-staged turbine of this kind
is about eight times greater than that of a
speed-stepped open-air turbine of the same
diameter. Air speed before and after the
turbine is about the same. The output achieved is
proportional to the product of volume flow per
unit time and the fall in pressure at the
turbine. With a view to maximum energy yield the
aim of the turbine regulation system is to
maximize this product under all operating
conditions 11.
33
Blade pitch is adjusted during
operation to regulate power output according to
the altering air speed and air flow (Fig. 11). As
soon as the wind speed in the chimney exceed 2.5
m/s the turbine is started automaticaly and cut
into the public grid. The output power of the
turbine is adjusted by limiting the rotation
frequency of the turbine. This can be adjusted
by changing the blade angle automatically (Fig.
12).
Fig. 11. Turbine Propeller
Fig. 12. Blade Angle
34
The pressure drop
Theoretical useful power Powerwt at turbine
Powerwt VC AC ?PS
Electrical Power W V I Volume Flow
And finally we get the equation
35
13. The Appropriate Charesteristic Curve
.
Powerwt takes a minimum between these extreme at

V
.
PV?PS
?Ptot
?Ps
2/3 ?Ptot
O
Fig. 13. Characteristic Curve
36
Thus mechanical power taken up by the turbine is
Powerwt,max (2/3)ncoll nc Acoll G
Powerwt,max (2/3)ncoll(g/CpTo)HoAcollG
37
Chimney Height HC
750m Collector Diameter Dcoll
2200m Solar Irradiation
G 1000W/m2 Mechanical Efficiency
nwt 0.8 Collector Efficiency
ncoll 0.6 Heat Capacity of the
Air CP 1005j/kgK Ambient
Temperature T0 200C Gravity
Acceleration g 9.81m/s2
Pelectric (2/3)(0.8x0.6)9.81/(1005x293)x750x375
1000x1000
Pelectric 30 MW
38
14. Typical Dymensions for Solar Chimneys With
Different Power
Dymensions
With 2300 kWh/m2y global radiation
Power Block Size MW 5 30 100 200
Collector Diameter Dcoll m 1110 2200 3600 4000
Chimney Height HC m 445 750 950 1500
Chimney Diameter DC m 54 84 115 175
Annual Energy Production GWh/y 13.9 87.4 305.2 600
Table. 1 Typical Dymensions for Solar Chimneys
With Different Power
39
15. Thermodynamics
With 2300 kWh/m2y global radiation
Power Block Size MW 5 30 100
Temperature rise in Collector oK 25.6 31.0 35.7
Updraft Velocity in Chimney (ful load) m/s 9.1 12.6 15.8
Total Pressure Difference Pa 388.3 767.1 1100.5
Pressure Loss by Friction (Collector And Chimney) Pa 28.6 62.9 80.6
Pressure Drop at turbine Pa 314.3 629.1 902.4
Table. 2 Thermodynamics Data
40
117.5

52.65
3.10
80.10
1.31
Pressure Loss at Chimney Top Pa 40.4 75.1
Average Annual Efficiency Average Annual Efficiency Average Annual Efficiency Average Annual Efficiency
Collector 56.24 54.72
Chimney 1.45 2.33
Turbines 77.00 78.30
Whole System 0.63 1.00
Table. 2 Thermodynamics Data
41
16. Operation
Power Block Size MW 5 30 100
Annual Energy Production Annual Energy Production Annual Energy Production Annual Energy Production Annual Energy Production
Total GWh/y 13.9 87.4 305.2
Per m2 kWh/m2y 14.4 23.0 30.0
Annual Operating Hours h/y 8423 8506 8723
Full Load Hours h/y 2780 2913 3052
Capacity Factor 31.7 33.3 34.8
Night Energy Production GWh/y 1.5 8.7 32.0
Table. 3 Operation Data
42
17. Technical Data Quantities
Power Block Size MW 5 30 100
Collector Diameter m 1110 2200 3600
Glass Collector Roof-interior Diameter m 162 252 346
Total Covered Area m 76 118 159
Glass Roof Area Total m2 967700 3801000 10180000
Double Glazed 2x4mm m2 328880 1318000 3570000
Single Glazed 1x4mm m2 61900 2433000 6510000
Table. 4 Collector Data Quantities
43
Glass Roof Area m2 947700 3801000 10080000
Chimney Area m2 4500 11000 20000
Glass Roof Height (external) m 2.0 4.5 6.5
Glass Roof Height (internal ) m 10.0 15.5 20.5
Total Quantity 4mm Raw Glass km2 1.3 5.1 13.7
Table. 4 Collector Data Quantities
44
18. Energy Production Costs With the
support of construction companies, the glass
industry and turbine manufacturers a rather exact
cost estimate for a 200 MW solar chimney could be
compiled. We asked a big utility "Energie in
Baden-Württemberg" to determine the energy
production costs compared to coal- and combined
cycle power plants based on equal and common
methods (Table. 5) 12.
45
Table. 5 Comparison between the energy
production costs of a 2 x 200 MW solar chimneys
and 400 MW coal and combined cycle power plants
according to the present business managerial
calculations.
46
Fig. 14. Energy production costs from solar
chimneys, coal and combined cycle power plants
depending on the interest rate.
47
CONCLUSION No ecological harm and no
consumption of resources, not even for the
construction. Solar chimneys predominantly
consist of concrete and glass which are made from
sand and stone plus self-generated energy.
Consequently in desert areas - with inexhaustible
sand and stone solar chimneys can reproduce
themselves. A truly sustainable source of energy!
13.
48

• REFERENCES
• The Solar Chimney. The use of three old
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• Schlaich, J. (1995). Solar Chimney Electricity
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• Schlaich, J. (1995). Solar Chimney Electricity
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  p.28.
• Schlaich, J. (1995). Solar Chimney Electricity
  from the Sun. Stuttgart Edition Axel Menges,
  p.17.

49

1. Schlaich, J. (1995). Solar Chimney Electricity
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4. Internet sayfasini bul
5. Schlaich, J. (1995). Solar Chimney Electricity
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50
10. Schlaich, J. (1995). Solar Chimney
Electricity from the Sun. Stuttgart Edition Axel
Menges, p.18. 11. Schlaich, J. (1995). Solar
Chimney Electricity from the Sun. Stuttgart
Edition Axel Menges, p.20. 12. The Solar Chimney.
Energy Production Costs. Retrieved 1 December
2001 from http//wire0.ises.org/wire/Publications
/Research.nsf/defaultview/0DED34BF3EB9A985C1256984
0055F09E/File/SolarChimney_short_version.pdf 13.
The Solar Chimney. Energy Production Costs.
Retrieved 1 December 2001 from
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sf/defaultview/0DED34BF3EB9A985C12569840055F09E/F
ile/SolarChimney_short_version.pdf
51
Fig. 2. Collector glass roof of solar chimney
prototype at Manzanares from inside.
Retrieved 30 November 2001 from
http//wire0.ises.org/wire/independents/imagelibra
ry.nsf/25bcb7328e30a3e 2c12567530049c67f/A89238512
8ECAD96C12569840050A66F/File/glass_roof_from_insi
de.jpg Fig. 3. Aerial View of Solar Chimney
Prototype at Dusk. Retrieved 30 November
2001 from http//wire0.ises.org/wire/independents
/ImageLibrary.nsf/H/O?Open840A07E8A8A6A557C125698
4004EEDF8 Fig. 4. The energy storage Principle
of heat storage underneath the roof
using water-filled black tubes. Retrieved 1
December 2001 from http//wire0.ises.o
rg/wire/Publications/Research.nsf/defaultview/0DED
34BF3EB9A985C12569840055F09E /File/SolarChimney_s
hort_version.pdf
52
Fig. 5. Solar Chimney prototype during
construction. Retrieved 30 November 2001 from
http//wire0.ises.org/wire/independents/imagelibra
ry.nsf/396e92819880db7dc125680f00443688/1982AF4545
393096C1256984004F7395/File/SolarChimneyManzanare
sChimneyConstruction.jpg Fig. 6. Solar Chimney
Prototype at Manzanares. Retrieved 30 November
2001 from http//wire0.ises.org/wire/independe
nts/imagelibrary.nsf/396e92819880db7dc125680f00443
688/1162284EE820787FC1256984004CF03F/File/manzana
res_air.jpg Fig. 10. Solar Chimney Power Plants.
Retrieved 30 November 2001 from
http//www.argonet.co.uk/users/bobsier/sola6.html
Fig. 14. The Solar Chimney. Energy Production
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sf/defaultview/0DED34BF3EB9A985C12569840055F09E/F
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53
Table. 1 Schlaich, J. (1995). Solar Chimney
Electricity from the Sun.
Stuttgart Edition Axel Menges, p.36. Table.
2 Schlaich, J. (1995). Solar Chimney
Electricity from, the Sun.
Stuttgart Edition Axel Menges, p.37. Table. 3
Schlaich, J. (1995). Solar Chimney Electricity
from the Sun. Stuttgart Edition
Axel Menges, p.37. Table. 4 Schlaich, J. (1995).
Solar Chimney Electricity from
the Sun. Stuttgart Edition Axel Menges,
p.38. Table. 5 The Solar Chimney. Energy
Production Costs. Retrieved 1
December 2001 from http//wire0.ises.org/wire/P
ublications/Research.nsf/defaultview/0DED34BF3EB9A
985C12569840055F09E/File/SolarChimney_short_versi
on.pdf
54
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