The Solar Updraft Tower : Das Aufwindkraftwerk

Motivation and Concept - Text

Joerg Schlaich and Rudolf Bergermann

The most significant problems of our time,

poverty in the Third World and the climate change

are interlinked through energy supply

and can be solved, if we only want to!

The industrialized countries pollute the worldwide climate with their fossil-fuelled

power generation.

The poor are poor because they cannot afford sufficient energy supply and the

population keeps growing. (Fig. 1)

If the billions of people who must do without sufficient energy supply would have to

cover their energy needs with coal, oil and gas, the climate could not be saved and

the environment would be destroyed.

Hence, poverty and climate problems can only be solved with global concepts, mutually and

equally beneficial to the poor and to the industrialized countries.

The poor countries on the „southern hemisphere“, especially the African, have one

advantage over the rich countries in the „northern hemisphere“:

Sun + Desert, i.e. intensive solar radiation on agriculturally futile land. (Fig. 2)

If these poor countries had large scale affordable solar power plants, - affordable because

they were built mainly with their own resources and skills -, and which they did not need to

import at exorbitant cost, they would profit twice:

by their inexhaustible, affordable power supply and by innumerable new jobs.

“The Taliban aren’t fighting for religion but for money. If they had jobs, they would stop

fighting!” Sham Sher Khan from TIME, April 20, 2009

As electric energy can be transported over very large distances with surprisingly little loss

they could export their solar electricity to the industrialized countries. (Fig. 3) [3]

The industrialized countries would also profit twofold: the energy supply companies

could develop this new industry in the desert countries and they could transport the

solar electricity for local consumption directly via cable for the stationary or possibly

via hydrogen for the mobile consumption to their own countries. Furthermore they

would benefit from the new prosperity in the poor countries, because these could then

purchase their products.

See references a) On Solar Energy Utilization [1] - [8]

Today there are three novel large scale solar thermal power plants.

Central Receiver Systems which concentrate the solar radiation bi-axially with heliostats on

a tower top. The fluid heated there is conducted to a conventional power block. (Fig. 4)

Parabolic Trough Systems are so far the most successful variant. Solar radiation is

concentrated along one axis onto a receiver tube and the heated fluid is conducted to a

conventional power plant. (Fig. 5)

The parabolic trough and the central receiver systems are technologically suitable especially

for sunny and industrialized countries (USA, Australia…). They need direct radiation and

consume much cooling water. The expected levelised electricity costs are at about 12 to 15

Eurocents/kWh. The author´s team under guidance of Wolfgang Schiel is actively involved in

developing this technology.

The Solar Updraft Tower which “sucks” air heated through solar radiation under a collector

roof into a large vertical concrete tube and thus drives turbines with generators installed at

the base of the tube. (Fig. 6+7) [12] - [27]

A simple water tube storage guarantees a 24-hour continuous operation. (Fig. 8)

Cooling water is not needed for operation.

It is sustainable and inexhaustible because its most important construction materials,

concrete for the tower and glass for the collector roof, can be manufactured from sand and

stone directly on site. (Fig. 9)

Technologically it corresponds to the so far most successful power plant, the hydroelectric

power plant –lake, penstock, turbine – and matches its durability and robustness.

It is ideal for indigenous construction in developing countries.

Depending on the capacity, solar radiation and labor costs, levelised electricity costs of 6 to

10 Eurocents/kWh can be expected. After depreciation it is a “cash cow” like the

hydroelectric power plant.

Contrary to the parabolic troughs, which have been tested in many plants and are built at

present (with the participation of the author’s team) at large scale, the Solar Updraft Tower is

not considered “proven technology” and this unfortunately deters investors, seeking quick

profit.

Large-scale plants are considered to be too expensive for a first-of-its-kind system, the small-

scale plants are uneconomical.

Thus it is absolutely necessary to build a prototype which on the one hand is large enough to

exclude all possible doubts regarding function and feasibility, and which on the other hand

achieves economically justifiable electricity costs at moderate investments, i.e. which is

profitable.

Having this prototype, the Solar Updraft Tower – the hydro power plant of the desert – will

become fast selling. The world’s sunny deserts will contribute significantly to overcome Third

World poverty and will provide a sustainable world energy supply.

It is possible, if we only want to do it!

capacity 30 50 200 MW

tower height 750 750 1000 m

tower diameter 70 90 120 m

collector diameter 2950 3750 7000 m

tower cost 56 72 192 Mio. €

imported share: 20% 11 14 38 Mio. €

collector cost A

72 116 388 Mio. €

imported share: 0% 0 0 0 Mio. €

turbine cost incl. housing etc. 37 56 146 Mio. €

imported share: 90% 33 50 131 Mio. €

engineering, tests, misc. 21 32 53 Mio. €

imported share: 90% 19 29 48 Mio. €

total investment cost 186 276 779 Mio. €

total imported share 63 94 218 Mio. €

imported share in % 34% 34% 28% %

grant 0 0 0 Mio. €

total investment cost - grant 186 276 779 Mio. €

annuity on investment B,D

14.5 21.6 60.9 Mio. €

o&m cost 0.9 1.4 3.2 Mio. €

electricity production C

87 153 680 GWh/yr

LEC (levelized electricity cost)D

0.18 € 0.15 € 0.09 € €/kWh

non-energy revenues 3.1 3.1 3.1 Mio.€/yr

LEC incl. non-energy rev. 0.14 € 0.13 € 0.09 € €/kWhA

average labor cost 5 Euro/hB

depreciation time: 25 years, interest rate: 6%C

at 2300 kWh/(m²yr) global solar insolationD

grant included in calculation

Solar Updraft Towers

Schlaich Bergermann SolarHohenzollernstr. 1D-70178 StuttgartGermany

Postscript: Chronology

In the year 1972, the author, Rudolf Bergermann and their team, were invited by the power

industry to develop a large scale cooling tower for dry cooling. This resulted in a cable-net

cooling tower design and a prototype at Schmehausen, Germany. (Fig.10)

There within the team, including at that time, Michael Simon, the question arose, whether the

natural updraft in such chimney tube could not be utilized to generate electricity as against

evaporate it largely.

Simple checks quickly made clear that such approach only makes sense, if there is an

additional “fire” at the base of the chimney tube, such as a large greenhouse roof collecting

solar warm air. This in the year 1979, resulted in what we called the “Solar Chimney” (later

Solar Updraft Tower) Aufwindkraftwerk (Fig. 6+7) [12] - [27]. It was already in the same year,

when the Ministry for Research and Technology granted us an amount of 3,5 Mio. DM (ca.

1,8 Mio. €) for a feasibility study. However we decided, to use the money for a test Solar

Chimney at Manzanares/Spain. (Fig. 11 + 12). This permitted us to confirm our analytical

results (Fig. 13) and with further grants, to expand our knowledge [14] - [17].

Originally the plan was to build the prototype in 1980, take measures in 1981 and 1982 and

dismantle it in 1983, out of safety reasons because the grant did not permit regular corrosion

protection especially for the stay-cables. Years passed away permitting us to take more

measurements and to welcome visitors, though we know that corrosion was on the way.

The site was closed at windspeeds beyond 20m/s and so we were prepared for a scheduled

and controlled failure in 1990, after 10 years as against originally 3 or 4.

Concerning the main structural issue, the tube or tower or chimney, we studied and

compared several solutions (Fig. 14 + 6).

We came to the result that the cylindrical concrete tube stiffened by spoked wheels promises

least costs.

Somewhere at the end of the eighties at the last century we got hold of a paper written in

1931 describing the basic principle of the solar updraft power tower [11], (Fig. 15). So we

frankly agree that we did not invent but “only” develop the solar updraft tower.

References (Very small selection in chronological order):

a.) On Solar Energy Utilization (the author´s early papers)

[1] Schlaich, Joerg: Neue und Erneuerbare Energiequellen

Beton-und Stahlbetonbau, April, 1982 und

Festschrift `75 Jahre Deutscher Ausschuss für Stahlbeton´

[2] Schlaich, Joerg: Contribution to the Utilization of Solar Energy

IABSE 12th Congress, Vancouver, Canada, September 1984

[3] Schlaich, Joerg: Wieviel Wüste braucht ein Auto?

Eigenverlag (Broschüre: siehe Bild 3, 2. Festschrift Bulling August, 1989

[3´] Schlaich, Joerg: How much desert does a car need?

IABSE Proceedings P-144/90. May 1990

[4] Schlaich, Sibylle; Schlaich, Jörg: Erneuerbare Energien nutzen

Werner Verlag Düsseldorf, April 1991

[5] Schlaich, Joerg: World energy demand, population explosion and pollution:

Could solar energy utilization become a solution

The Structural Engineer, London, Vol. 69/19, May 1991

[6] Schlaich, Joerg: Solar Energy Utilization – A Call for Action

IASS Bulletin Vol. 32, August, 1991

[7] Schlaich, Joerg: Thesen zur Notwendigkeit, Solarkraftwerke für die Dritte Welt zu entwickeln

VBI, Bonn, November 1991

[8] Schlaich, Joerg: Sonnenenergie Brockhaus Enziklopädie, Bd. 20, Dezember 1993

b.) Cable-net Cooling Towers

[9] Schlaich, Joerg: Membrane-skin and cable-net cooling towers

International Conference on Tension Structures, London April 1974

[10] Mayr, Weber, Jasch, Schlaich: Der Seilnetzkühlturm Schmehausen,

Bauingenieur 11/1976

c.) The Solar Updraft Tower – Das Aufwindkraftwerk

[11] Guenther, H.: In Hundert Jahren“ Die künftige Energieversorgung der Welt.

Kosmos, Gesellschaft der Naturfreunde, Frank´sche Verlagshandlung, Stuttgart 1931

[12] Haaf, W., Mayr, G.., Schlaich J.: Atmosphärenthermische Aufwindkraftwerke,

Bundesministerium für Forschung und Technologie , Bonn Forschungsbericht T 81-113,

August 1981

[13] Mayr, G., Friedrich, K., Schlaich, J.: Solar Chimneys-The Concept, The Pototype in Spain,

Prospects for the Future

IASS-Bulletin No. 78 April 1982

[14] Mayr, G., Friedrich, K., Schlaich, J.: Atmosphärenthermische Aufwindkraftwerke – Bau der

Demonstrationsanlage Manzanares und Ergebnisse

Statusreport Windenergie des BMFT, Oktober 1982

[15] Haaf, W., Lautenschlager, O., Bergermann, R., Schlaich, J.: Ergebnisse vom Aufwindkraftwerk

Manzanares, Vorbericht, September 1984

[16] Schiel, W., Friedrich, K., Schlaich, J.: Aufwindkraftwerke-Technische Auslegung,

Betriebserfahrung und Entwicklungspotential

Zeitschrift des VDI und VDI-Bericht, November 1988

[17] Schiel, W., Schlaich, J. et al: Aufwindkraftwerke-Abschlussbericht, Übertragbarkeit der

Ergebnisse von Monzanares auf größere Anlagen. Abschlussbericht, BMFT-

Förderkennzeichen 0324249D, November 1990

[18] Schlaich, Joerg: Das Aufwindkraftwerk / The Solar Chimney

Edition Axel Menges, Stuttgart, Germany, 1995 English Edition

[19] Kreetz, H.: Theoretische Untersuchungen und Auslegung eines Wasserspeiches für das

Aufwindkraftwerk. Diploma thesis

Technical University Berlin, 1997

[20] Weinrebe, Gerhard:

Solar Chimney Simulation, Proceedings of the IEA SolarPACES Task III Simulation of Solar

Thermal Systems Workshop, 28-29 September, 2000 Cologne

[21] Gannon, A.J., Backstroem, T.W. v.: Solar Chimney Cycle Turbine Characteristics

Sol. Energy Eng., 122 (3), pp.133-137, 2000

[22] Schlaich, Joerg; Schiel, Wolfgang: Solar Chimneys

Encyclopedia of Physical Science and Technology, 3rd

ed., Academic Press,

London 2001

[23] v. Backstroem, T.W.; Gannon, A. J.: Solar Chimney Turbine Characteriastics, Sol. Energy, 76

(1-3), 2003

[24] Ruprecht, A. et al.: Strömungstechnische Gestaltung eines Aufwindkraftwerks (Fluid Dynamic

Design of Solar Updraft Tower Plant), Proceedings oft he Internationales Symposium über

Anwendungen der Informatik und Mathematik in Architektur und Bauwesen, June 10-12,

Bauhaus-University, Weimar, Germany

[25] Dos Santos Bernardes, M.A., Voß, A., and Weinrebe, G.: Thermal and Technical Analyes of

Solar Chimneys

Sol. Energy, 75, pp. 511-524. 2003

[26] Goldack, Arndt: Tragverhalten und Aussteifung hoher Stahlbetonrohren für Aufwindkraftwerke,

Universität Stuttgart, Diss., 2004.

[27] Schlaich, J., Bergermann, R., Schiel, W., Weinrebe, G.: Design of Commercial Solar Updraft

Tower Systems Utilization of Solar Induced Convective Plants for Power Generation. Journal

of Solar Energy Engineering, February 2005

The Solar Updraft Tower : Das Aufwindkraftwerk

Motivation and Concept - Figures

Joerg Schlaich and Rudolf Bergermann

Figure 1 Energy consumption and population growth in relation to standard-of-living (per capita gross national product)

Figure 2 Areas needed to cover the world energy demand by solar power

Figure 3 Solar electricity from deserts for transmission to northern countries - a concept today called DESERTEC Jörg Schlaich: Wie viel Wüste braucht ein Auto? August 1989; How much desert does a car need? [5]

Figure 4 Central Receiver System with heliostats, Sevilla/Spain

Figure 5 Parabolic Trough System

Figure 6 Solar Updraft Tower, 1980

Figure 7 Solar Updraft Tower – Principle

Figure 8 Solar Updraft Tower – 24-hour-operation with tube storage (1996)

Figure 9 The solar updraft power feeding a glass and a cement factory: Glass and cement = sand/stone + energy + labor

Figure 10 The Cable net cooling tower at Schmehausen (1973) 10 a) Cable net before cladding

10 b) The completed tower

Figure 11 Solar Updraft Tower – Test plant in Manzares, Spain (1979 – 1990) Diameter of collector roof ~200m; Height of tube ~190m BMFT, Union Electrica Fenosa/Spain, Schlaich Bergermann und Partner

Figure 12 The collector roof, at Manzanares, indigenous construction

Figure 13 Measurements Manzanares Global radiation (W/m2) versus electrical output (KW) and upwind speed (m/s)

Figure 14 Development of the tube or tower or chimney during the years 1979-1980 14 a) Cable stayed prestressed membrane, our first Solar Chimney

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8. Juni 1987

14 b) The steel tube of Manzanares Prototype

14 c) Free standing conical concrete tubes

14 d) Free standing cylindrical concrete tubes, stiffened by spoked-wheels (also Fig. 6)

14 e) A spoked wheel

14 f) Our vision in the year 2010

Figure 15 The vision of “H. Günther“ in the year 1931: Windkraftwerke in der Sahara an den Steilabstürzen der Atlasketten“ [11]