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Floating Solar Chimney Technology from Prof. Christos Papageorgiou

Floating Solar Chimney

Solar Chimneys can be made as reinforced concrete structures (Concrete Solar Chimneys, CFCs), or as lighter than air inflated structures (Floating Solar Chimneys FSCs).
The floating solar chimneys are made by successive balloon tubes, filled with a lighter than air gas. This permits to the FSCs to float in the air and thus to have heights 1.5 to 3 Km giving to their SAEPPs higher efficiencies than Concrete Solar Chimney SAEPPs.

A solar chimney power plant has three major components:
(1) A circular solar collector (Greenhouse)
(2) A tall cylinder in the center of the solar collector ( Solar Chimney)
(3) A set of air turbines geared to electric generators around the bottom of the solar chimney The air warms up inside the greenhouse by the solar irradiation and, due to its buoyancy, tends to escape through the Solar Chimney.
illustration of the supple flexible Floating Solar Chimney concept from
illustration of the supple flexible Floating Solar Chimney concept from
This warm stream of air is leaving part of its thermodynamic energy to the air turbines placed in the path of the airflow. The solar chimney power stations were named Solar Aero-Electric Power Plants (SAEPPs) due to their similarity to Hydro Electric Power Plants. The efficiency of the SAEPPs is roughly proportional to the height of their solar chimneys.

Using ground thermal storage, or artificial thermal storage in the form of water in closed plastic tubes, it can be proved that the SAEPPs can operate 24 hours per day 365 days per year with a minimum guaranteed power production. This means that the SAEPPs, although renewable by nature, can have a similar operation to conventional power stations and thus can replace them.

There is a very complete presentation of Floating Solar Chimneys in pdf format available on

In "Floating Solar Chimney versus Concrete Solar Chimney Power Plants" a paper published at the International Conference on Clean Electrical Power, 21-23 May 2007 Page(s): 760 - 765, a comparison for construction cost of SAEPPs with Floating Solar Chimneys and Concrete Solar Chimneys is given. It is shown that FSC Technology Power Plants is 5 to 6 times cheaper than CFC Technology Power Plants.

The Floating Solar Chimney from

- History

Solar chimney technology is an electricity power generating method working with the warm air of a large solar collector up drafting through a tall chimney.
One of the earliest descriptions of a solar chimney power station was written in 1931 by a German author, Hanns Gunther.
More recently Schaich, Bergerman and Partners, under the direction of German engineer Prof. Dr. Ing. Jorg Schlaigh, built a working model of a solar chimney power plant in 1982 in Manzanares (Spain), 150 km south of Madrid, which was funded by the German Government. This power plant operated successfully for approximately 8 years. The chimney had a diameter of 10 m and a height of 195 m, and the maximum power output was about 50 KW. During the final 3 years, optimization data was collected on a second-by-second basis.
Prof. J. Schlaigh in 1996 published a book [1] in order to present this technology.Although J. Schlaigh proposed initial physics to explain the solar chimney technology operation, the theoretical foundation for the operation of solar chimney power plants was done later by Von Backstrom and Cannon [2], [3]. [References appear in Pdf for printing]
Prof. J. Schlaigh proposed Power Plants with tall solar chimneys made by reinforced concrete up to 1000m. Following his ideas the "enviromission" Ltd of Australia with "Solarmission technologies" of USA, were going to build in Australia a Solar Chimney Power Plant of 200 MW, (this decision recently was revised to a 50 MW Power Plant). The initial Power Plant of 200 MW shoud have a huge reinforced concrete solar chimney of 1000 m with internal diameter 130m and a circular solar collector with a diameter 7000 m.
This Power Plant has the brand name "Solar Tower". The construction cost of this "Solar Tower" was estimated to be approximately 700 million USD. The plant will produce annually not less than 600 GWh.
A similar renewable power plant of 200 MW, with wind turbines (50 turbines of 4 MW each for example) will produce almost the same GWh/year but will have a cost 200 - 250 million USD.
Taking into consideration the construction difficulties of huge reinforced concrete Solar Towers and the high construction cost of their respective power plants the energy society has not considered yet the reinforced concrete solar chimney technology as a successful competitive option in renewable technologies.

- The Floating Solar Chimney Technology

Floating Solar Chimney Technology is an innovative cost effective Solar Technology, developed by Prof. Dr Engineer Christos Papageorgiou, using physics, Mathematics and the existing and experimentally tested Solar Chimney Technology.
Floating Solar Chimney Technology can solve the Energy problem, eliminating the global warming effect and assuring world's Sustainable Development.

- Floating Solar Chimney Technology Application

1. The Solar Aero-Electric Power Plant with Floating Solar Chimneys
A Solar Aero-Electric Power Plant (SAEPP) is shown in the first figure.

2.The Solar Aero-Electric Power Plant (SAEPP) main components
A SAEPP is made of three components:
A large circular solar collector with a transparent roof supported a few meters above the ground (the Greenhouse).
A tall, warm air up drafting, Cylinder on the center of this Greenhouse (The Floating Solar Chimney).
A set of Air Turbines geared to appropriate Electric Generators around the base of the Solar Chimney(The Turbo Generators).

3.How SAEPPs operate
The Solar energy warms the air inside the solar collector (greenhouse effect).
The warm air tends to escape through the Solar Chimney to the upper atmosphere.
This up drafting stream of warm air leaves part of its thermodynamic energy to the Air Turbines geared to Electric Generators, converting this energy to Electrical.

4.Is Solar Aero Electric Power Plants (SAEPPs) similar to Wind farms?
Although artificial wind is generated inside the solar collector (from its periphery towards its center) SAEPPs are not similar to wind farms.
The wind Turbines convert the wind kinetic energy to rotational energy.
The SAEPP’s Air Turbines leave the moving warm air kinetic energy unchanged.

5.Solar Aero Electric Power Plants’ similarity to Hydro Electric Power Plants
SAEPPs are similar to Hydro Electric Power Plants (that is why I called them Aero Electric).
Their Air Turbines convert the up drafting air dynamic energy (due to buoyancy) to rotational energy,as Water Turbines convert the water’s dynamic energy (due to gravity) to rotational.
In both Power Plants their Power Output is proportional to H (Floating Solar Chimney air up drafting height or Dam falling water height).

To see paragraphs 6 to 35 and the diagrams, drawings, statistics, tables and schemes in there, please visit the original website of Prof. Papageorgoiu: from till

36. Investments for Floating Solar Chimney technology
The annual primary energy world demand (year 2004) was ~1.2*10^8 GWh, emitting ~26 billion tones of CO2.The figures could be doubled in the next 30 to 40 years.
The annual energy demand for electricity and fuels (Hydrogen generated by electricity) is not more than 20% of this quantity i.e. 24*10^6 GWh.
A reasonable choice could be, for the next 30 years, to build every year SAEPPs with Floating Solar Chimneys with an overall Power of 330 GW producing ~ 10^6 GWh/year.
The annual investment for this choice is 100÷150 billion €/year (that is approximately 25÷35% of the forecasted energy investments ( estimated to 400 billion € /year ).
The necessary land annually, for these SAEPPs installation worldwide
will not exceed 20.000 sq Km .
The 30 years overall land, for the SAEPPs of rating Power of 10000 GW (generating 30*10^6 GWh of electric energy per year), will not exceed worldwide the area of ~600.000 sq Km.

37. Conclusion 1
The presented Floating Solar Chimney Technology is not an illusion is a serious innovative electric energy generating method.
The Technology is a many years research project by many independent institutions supported by experimental results.
Although the Technology’s Power Plant looks like a perpetual machine, is operating using the solar irradiation energy collected by the greenhouse effect .
The Technology’s Power Plants can be constructed using existing material and equipment.

38. Conclusion 2
The Floating Solar Chimney technology supported by the existing renewable technologies can cover the world’s energy demand (in electricity and any future transportation fuels based on Hydrogen).
The technology can eliminate the CO2 emissions below any safe threshold for our planet .
The technology can be the basic “Power vehicle” towards the hydrogen era.
The technology is very competitive to any other fuel consuming energy technology.
The technology is very reliable (as the sunrise !).

Thus Floating Solar Chimney technology can assure world’s sustainable development.

The Scientific Documentation of Floating Solar Chimney Technology is the set of the main papers written by the Inventor and appropriately revised by him for this site. The papers were (or are going to be) presented to related Power or Solar Energy international conferences.

The papers with their respective specific topics are:
Papageorgiou C. 2004 "Solar Turbine Power Stations with Floating Solar Chimneys". IASTED Proceedings of Power and Energy Systems, EuroPES 2004, Conference, Rhodes Greece July 2004 pp, 151-158.
Topic: Theoretical Performance Analysis of Floating Solar Chimney Power Stations.
Papageorgiou C. 2004, "External Wind Effects on Floating Solar Chimney" IASTED Proceedings of Power and Energy Systems, EuroPES 2004, Conference, Rhodes Greece ,July 2004 2004 pp.159-163.
Topic: External Wind Effects on the Floating Solar Chimneys.
Papageorgiou C. 2004, "Optimum Design for Solar Power Stations with Floating Solar Chimneys'', proceedings of ISES Asia Pacific Solar Energy Conference, Kwangju Korea, October 2004 pp.763-772.
Topic: Design, Calculations and Cost of Floating Solar Chimneys and their respective Power Plants.
Papageorgiou C. 2004, ''Efficiency of solar air turbine power stations with floating solar chimneys'' IASTED Proceedings of Power and Energy Systems Conference Tampa Florida USA, November 2004, pp. 127-134.
Topic: Efficiency and Annual Performance of Floating Solar Chimney Power Stations.
Papageorgiou C. 2005 "Turbines and Generators for Floating Solar Chimney Power Stations". IASTED Proceedings of Power and Energy Systems, EuroPES 2005 conference. Benalmadena Spain June 2005.
Topic: Operation of Floating Solar Chimney Power Stations taking into consideration its Air Turbines and Electric Generators Performances.
Papageorgiou C. 2005 "Hydrogen Production by Solar Aero Electric Power Plants with Floating Solar Chimneys" International Hydrogen Energy Congress Conference 2005,Istanbul Turkey, July 2005.
Topic: Evaluation of Hydrogen Production units composed of Solar Aero Electric Power Plants with Floating Solar Chimneys and appropriate Electrolysis Units.
Papageorgiou C. 2005 "Floating Solar Chimney: The Link towards a Solar Future" ISES 2005 Solar World Congress Conference, Orlando Florida USA, August 2005.
Topic: Cost of Solar Aero Electric Power Plants with Floating Solar Chimneys of variable Height and their comparison to Conventional Power Plants.
Papageorgiou C. 2006 "Floating Solar Chimney Power Stations with Thermal Storage". IASTED proceedings of Power and Energy Systems, EuroPES 2006. Rhodes Greece, July 2006( to be presented).

Topic: Thermal storage of SAEPPs for their 24 hours/day operation.
1. Do the proper materials for the construction of the Floating Solar Chimney (FSC) exist?
The necessary material for the FSC's construction are already in use in various applications as follows:
- The appropriate fabrics for the FSC's lifting tubes are already used in airship or balloon industry.
- The appropriate very strong fabrics, reinforced with composite fibbers, for the FSC's inflated supporting tube-rings are already used in the construction of many inflated structures with higher overpressures, in sailing etc.
- In case of using Aluminium tubes, for the supporting rings, it is well known their broad application in light and enduring structures.
- The attaching or connecting very strong ropes for the FSC's structure, made of aramid yarn is in use for many years in many applications.
Hence the necessary materials for the FSCs are in the market, in reasonable prices, and can be appropriately combined for their construction by experienced manufacturers or contractors in similar works.

2. Is the project endangered by earthquakes or strong winds?
- Seismic activity has no effect on the FSC that by nature is a lighter than air standing in upright position structure, due to its buoyancy, with the ability to float in the air following the external winds.
- External very strong winds can not harm the structure because of its ability to deflect locally and to incline remaining attached to its special base, receiving the appropriate angle of equilibrium on the wind's direction.
- The structure made of a plurality of successive and dynamically independent parts, attached separately on its inclining base, can accommodate also the wind's variation with altitude.

3. Is the project easily maintained?
- The FSC's necessary periodic maintenance (lifting gas escapes replacement, tearing or worn fabric sewing or sticking etc) can be executed by skilled personnel with the FSC standing in its upright position.
- Heavy repair maintenance (replacement of tubes for example) can be executed locally by the skilled personnel, lowering the structure by partial deflation. In this case the lifting gas should be stored temporarily in appropriate existing storage vessels, in order to be used for the re inflation of the structure.
- Thus the maintenance or repair of the FSCs it is possible but the appropriate maintenance procedures and specifications should be defined during their engineering study.
- The maintenance of the transparent roof of the solar collector and of the rest equipment of the FSC's Power Station, is simple due to their proximity to the ground.

4. Can one or more projects replace the conventional fuel consuming factories for electrical energy production?
- The optimum range of Power rating for the FSC Power Stations, due to the high dimensions of their FSCs, is 50 MW-200MW.
- For the appropriate places of installation these FSC Power Stations can produce annually electrical energy respectively 150GWh-600GWh i.e. at least ~3000 KWh per their rated KW.
- Without any artificial thermal storage, the FSC Power Station's operating hours per year are ~3500 hours. If thermal storage is used, spread in water filled plastic bags or closed plastic tubes inside the solar collector area, the FSC Power Station can work 24 h/per day 365days/per year with their Power production, following the period's average solar irradiation. In this case their annual energy production will be almost equal to their annual production without thermal storage, but the periodic change of thermal storage can be used in order their production constantly to be above a limit and to follow, as close as possible, the demand of the electric Power grid.
- By this description it is evident that FSC Power Stations are big Electrical production units, producers of a guaranteed Electric Power profile year round, thus are compatible to conventional Power Plants (that are using coal, oil, gas or nuclear fuels) and thus can replace them.
- The rest Renewable Power Plants (wind, Solar concentrator, solar PVs, et al) are only Electrical energy production units of non-guaranteed power output, and cannot replace the conventional Power Plants.
- The only renewable Power Plant, having similar behaviour to FSC Power Plant, is the Hydro Electric Power Plant. Their similarity is far deeper that is why FSC Power Stations was named Solar Aero Electric Power Plants (SAEPPs).

5. What is the production cost per KWh from the FSC's Power Stations?
- An average Power Station with a Power rating of 100 MW should have, according to rough estimations, a construction cost of 30millions € up to 60 millions €, depending on the solar collector roof's transparent material. Their operating and maintenance annual cost will be in the range of 1.5 millions € to 2 millions € and will produce not less than 300 GWh/year.
- Estimating the FSC Power Station's depreciation period to 30 years and for reasonable financial assumptions (land lease, interest rate etc.) its production cost of KWh it will be less than 0.02 €.
- The calculations are not including any grants on the investment, or any other form of income arising by the greenhouse agriculture inside the solar collector etc.

6. In how much time will the capital investment be returned?
- Using the example of a FSC Power Station of 100 MW of a construction cost between 30 millions € to 60 millions € and of an annual production to 300 GWh and furthermore estimating the average selling price of its renewable KWh to 0.07 € and its production cost to less than 0.02 €, the repayment period for the investment will be between 2 years to 4 years. This Floating Solar Chimney Power plant can operate easily, following the appropriate maintenance, for 30 years.
- Due to the renewable character the FSC Power Station, the investment can achieve, in many countries, grants or tax benefits that can make it much more attractive.

7. Where are the appropriate locations to perform the Floating Solar Chimney Power Stations efficiently?
The appropriate locations for FSC's Technology Power Stations installation should have the following characteristics:
- High annual solar irradiation on horizontal surface (>1700 KWh/m2)
- High insolation (>3000 hours/year)
- Low average annual winds (
Meteorological Reactors