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The Solar Chimney


Day Night ... electricity 24 hour a day from solar energy alone. No ... Williams,J.R.(1977).Technology and applications;Ann Arbor Science Publishers Inc. ... – PowerPoint PPT presentation

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Title: The Solar Chimney

The Solar Chimney
  • Solar Energy-1
  • Physics 471
  • 2004-1
  • Presented ByVolkan CIRDAKLI
  • InstructorProf. Dr. Ahmet ECEVIT

  • Introduction
  • The Solar Chimney
  • Parts of the Solar Chimney
  • Collector
  • Turbines
  • Chimney
  • Working Principles of Solar Chimney
  • Technology
  • The Energy Storage In the Collector
  • Cost
  • The Mildura Solar Chimney

  • Advantages
  • Disadvantages
  • Conclusion
  • References

  • In many parts of the world,there is a growing
    awareness that some alternative energy sources
    could have an important role to play in the
    production of electricity.
  • However,only the solar energy represents totally
    nonpolluting inexhaustible energy resource that
    can be utilized economically to supply Mans
    energy needs for all time 1.

Fig. 1 The Prototype Manzanares Solar Chimney 2.
  • There are lots of methods of using the solar
    energy , and the Solar Chimney is one of them,
    which can be seen below, in figure 1.

2.The Solar Chimney
  • In 1978, it was suggested by Professor Schlaich
    of Stuttgart university that power could be
    produced by a hybrid solar system 3. The solar
    chimney system consists of three parts The
    collector,turbines and the chimney.

2.a. Parts of the Solar Chimney
  • 2.a.i. The Collector
  • Collector is the part,which is used to produce
    hot air by green-house effect. It is usually 5-6
    meters high and covers a very large area about
    thousands of m² as seen in figure 2.

Fig. 2 The Collector 2.

  • Since glazing increases the mass of the roof,
    glazed collectors should have stronger rods and
    should be attached as in figure 3.

Fig. 3 The glazed collector roof of Solar Chimney
  • There is no limitation for the surface area. The
    larger the area, the more energy generated from
    the chimney.
  • There should be slightly increasing height
    towards to the chimney in order to obtain minimum
    friction loss.
  • Covering materials may be different, such as
    glass, plastic film or glazed collector.The most
    efficient one is glazed collector.It can convert
    up to 70 of irratiated solar energy into heat a
    typical annual average is 50. Also, with proper
    maintenance, its life span can easily be 60 years
    or more.

  • 2.a.ii. Turbines
  • Turbines, seen in figure 4, are used to convert
    air current to the mechanical energy.

Fig. 4 Turbine for Solar Chimney Power Station
  • Turbines are placed horizontally in chimney,
    vertically in the collector.In order to obtain
    maximum energy from the warmed air,turbines
    blades should cover all the cross-sectional area
    of the chimney.
  • To do this,one big turbine or a few small
    turbines should be used in chimney, as can be
    seen from the figure 5. and figure 6.

Fig. 5 Turbine with large diameter 5.
Fig. 6 Small turbines 5.
  • 2.a.iii. The chimney
  • The most important part of the plant is the
    chimney,seen in figure 7. It acts as a thermal
    engine. Since the friction loss is minimum in the
    chimney it likes a pressure tube.

Fig. 7 The chimney 2.
  • Longer the chimneys height, the more the energy
    produced from the chimney.
  • The efficiency of the chimney is not depend on
    the amount of the temperature rising, but depends
    on the outside temperature.

Thus, efficiency directly proportional to the
ratio between the height of the chimney and the
outside temperature. 5
Although, the efficiency is proportional to the
height of the chimney, there is a limitation in
  • There are two types of different chimneys using
    for the plant. Free standing chimneys and guyed
    tubes (Figure 8. and figure 9. ) .
  • The life span of a free standing chimney is
    longer than that of the guyed tubes. It lasts
    about a hundred years, while the guyed tubes is
    much shorter.

  • Fig. 8 Free-standing 5.

Fig. 9 Guyed Tubes 5.
2.b. Working principles of Solar Chimney
  • Transparent roof, which is seen in figure 10,
    admits the short wave solar radiation component
    and retains long-wave radiation from the heated
    ground. Thus, when solar radiation pass through
    the transparent roof it is absorbed by the ground
    elements and it converts into heat energy.

Fig. 10 Transparent roof 4.
  • Since air is heated, it starts to rise up and
    move towards to chimney,seen in figure 11. Also,
    it gains velocity.
  • Heated air enters the chimney placed at the
    center of the roof and creates an up draught
  • Inside the chimney, turbines with electric
    generator,produce electricity 6.

Fig. 11 Schematic seen of the solar chimney 6
Collector Efficiency
Heat Output
Collector Area
Solar Radiation
The temperature differences between the collector
and out flow
Mass flow
Chimney cross-section area
Specific heat capacity of the air
Air speed at collector outflow
Specific dendsity of air at temperature To ?T
at collector outflow
  • Comparing with the collector and turbine, the
    chimney efficiency is relativelly low. For
    example, at a height of 1000 meters, chimney
    efficiency is somewhat greater than 3 5.

So, Why use a pipe or air channel to enclose the
turbines? Why not have a large "wind farm," with
turbines mounted on towers in the open air?   ,
  • Answer First, the wind turbines enclosed in a
    pipe can produce 8 times as much power for a
    given wind speed than a turbine in the open air.
    Second, the wind farm concept would require a
    much larger number of turbines. Also, the wind
    speed in the open air around the collector is
    significantly less than the air velocity through
    the air channel 7.

2.c. Technology
  • Solar chimneys are large-scale power plants with
    an output of 5 to 200 MW each 4.
  • A 100 MW plant will produce about 750 GWh/year at
    2.300 kWh/m² global horizontal radiation 4.
  • For that the glass roof has to be several
    kilometers in diameter and the tube has to be as
    high as possible to achieve a large annual output

  • The turbines are basically more closely
    related to the pressure-staged
    hydroelectric turbines than to the speed-stepped
    wind turbines. Therefore they have been developed
    and designed in collaboration with hydroelectric
    power plant manufacturers 4.
  • The turbines life span is based on its
    resistance to rapid pressure and speed changes of
    the air 5.

3.The Energy Storage In the Collector
  • Since collectors produce hot air by green house
    effect, to produce electric during the night,
    tight water-filled tubes are placed under the
    roof, as seen in figure 12. 6.

Fig. 12 Principle of heat storage underneath the
roof using water-filled black tubes 6.
  • The water heats up during the daytime and emits
    its heat at night.
  • These tubes are filled only once, no further
    water is needed, because the tubes remain closed
    after filling process.
  • 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 5.

  • 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 the utility "Energie
    Baden Württemberg" to determine the energy
    production costs compared to coal- and combined
    cycle power plants based on equal and common
    methods 8. (Table. 1).

Table 1. Comparison between the energy production
costs of two x 200 MW solar chimneys and 400 MW
coal and combined cycle power plants according to
the present business managerial calculations 8.
Fig. 13 Energy production costs from solar
chimneys, coal and combined cycle power plants
depending on the interest rate 8.
5.The Mildura Solar Chimney
  • The 1000m Solar Chimney in Mildura, Australia,
    will be the highest man-made structure on Earth,
    and can produce 200MW of electricity, providing
    power to 200,000 homes.Schematic seen of a
    construction of a chimney is in figure 14.

Fig. 14 Construction of a chimney 2.
  • The cost to build the tower is estimated at 395
    million. (About 14 percent more than an
    equivalent coal-fired power station, and about 70
    percent more per installed megawatt than a
    comparable wind farm).
  • The Australian government target of producing 2
    of energy from renewable sources by 2010 (9500
    GigaWatt hours) could be met easily2.

  • Details of the solar chimney are as
    followsLocation Mildura, AustraliaType
    Solar Tower power plant with steel-reinforced
    concrete tower and steel/glass solar air
    collector (alternatively with polymer
    glazing)Features The base of the tower will be
    between 170 to 200 metres. The chimney is
    basically a very simple tube with wall thickness
    of 25cm, diameter of 150m and a height of 1000m.
    The collector roof will be 5000m in
    diameter.Power Up to 500 Gigawatt hours per
    yearCompany Enviromission LtdConstruction
    time About 18-24 monthsExpected completion
    date 2005 2.

  • Solar chimney power stations are particularly
    suitable for generating electricity in deserts
    and sun-rich wasteland.
  • It provides electricity 24 hour a day from solar
    energy alone.
  • No fuel is needed. It needs no cooling water and
    is suitable in extreme drying regions.

  • It is particularly reliable and a little
    trouble-prone compared with other power plants.
  • The materials concrete, glass and steel necessary
    for the building of solar chimney power stations
    are everywhere in sufficient quantities.
  • No ecological harm and no consumption of

  • Some estimates say that the cost of generating
    electricity from a solar chimney is 5x more than
    from a gas turbine. Although fuel is not
    required, solar chimneys have a very high capital
    cost 2.
  • The structure itself is massive and requires a
    lot of engineering expertise and materials to
    construct 2.

  • Solar chimney power stations could make important
    contributions to the energy supplies in Africa,
    Asia and Australia, because there is plenty of
    space and sunlight available there 2.
  • It is very important for the future, because our
    resources are limited, except our sun.

  • Williams,J.R.(1977).Technology and
    applicationsAnn Arbor Science Publishers Inc.
  • A brief history of solar chimney.Retrieved
    10.11.2004 from http//
  • Taylor,R.H.(1983).Alternative energy SourcesAdam
    Hilger Ltd,p.292.
  • Solar Chimney-Technology.Retrieved 10.11.2004
  • http//

  • Schlaich,J.(1995).The Solar ChimneyEdition Axel
  • Solar Chimney-Principle.Retrieved 10.11.2004
  • http//
  • 7. Solar Chimney Power Plant versus Wind from
    the Sun Power Plant.Retrieved 10.11.2004 from
  • http//
  • 8. Solar Chimney-Energy cost.Retrieved
    10.11.2004 from
  • http//