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FAQ: Frequently Asked Questions


Why must the chimney of a Solar Updraft Tower be so high?

The driving force in Solar Chimneys is the weight difference between the hot light air inside the chimney flue and the corresponding heavy cold outside air.
size of some buildings compared to the Solar Chimneys projects in Spain, Australia, Namibia
size of some buildings compared to the Solar Chimneys projects in Spain, Australia, Namibia
Illustration from KRÄTZIG & PARTNER Bochum Group on Solar Power Technologies

Has this Solar Chimney already been tested?

Yes. A pilot plant in Manzanares with a chimney height of 195m, a collector diameter of 248m and a nominal power of 50kW has been tested in Spain from 1985 to 1989 (construction started in 1981). Predicted and measured values of power production for one year coincided within half a percent. The pilot plant in Manzanares hit a world record in reliability by running several years without a single second downtime on faults, operating for 32 months in fully automatic mode. The Solar Chimney represents thus the most reliable technology.

How well do the solar towers and other meteorological reactors compare with conventional factories for electrical energy production?

• By their description it is evident that Power Stations with Meteorological Reactors (Solar Chimneys and Energy Towers) will be very big electrical production units, which will produce a guaranteed Electric Power profile year round. Thus they are compatible to conventional Power Plants (that use coal, oil, gas or nuclear fuels) and thus can replace them. But as they are located in deserts or semi-desert areas, far away from consumption locations (big cities or industrial plants), they need very good interconnection of electricity grids and this is already being done progressively for all the other renewable energies: wind, sun, OTEC… (Have a look for instance to the Desertec concept on Solar thermal power plants have been in use commercially at Kramer Junction in California since 1985. New solar thermal power plants with a total capacity of more than 2000 MW are at the planning stage, under construction, or already in operation.

• Other Renewable Power Plants (wind, solar concentrator, solar PVs, et al) only produce when weather and meteorological conditions are optimum (enough wind but not too strong, for PVs: sunshiny days with few clouds but no production during the night) and thus are only electrical energy production units of non-guaranteed power output, and cannot replace the conventional Power Plants. Solar chimneys can!

• Due to thermal storage Solar updraft Chimney Power Stations can operate 24 h/ per day 365days/per year, with their daily energy production following the day’s average solar irradiation. The daily power production profile is very close to the usual demand profile and an aperture (or closure) mechanism allows to produce more (or less) at on-peak (or off-peak) consumption hours.

• Electric power cannot be stored up and saved. During the hours at night and on the weekends when demand for electric power decreases, regular fuel consuming power companies actually lose money because they cannot just slow down or stop the generators during these times. It is not feasible because powering down the turbines and then getting them back up to speed during the peak hours, even if could be done within eight hours, would be more costly than letting them run. On the contrary, heat can be stored up and saved on special water containing reservoirs or tanks under the greenhouse of the solar chimney power plants, and electrical output can be adapted to peak power demand.

• The only other renewable Power Plant, having a similar behaviour to a Meteorological Reactor Power Plant, is the Hydro Electric Power Plant. Their similarity is far deeper as water can be stored upstream and used for on-peak demand. Water can also be stored in a second reservoir downstram, and pumped back upstream when electricity from nuclear plants is much cheaper (off-peak demand). Conversion yield is good.

• The optimum range of Power rating for the Solar Chimney Power Stations, due to the high dimensions, is 50 MW (Ciudad Real project in Spain), 200MW (Buronga, New South Wales project in Australia), and 400 MW (GreenTower South African project in the Namib desert, Namibia). This range of Power (50 – 400 MW) seems to be also optimum for Floating Solar Chimneys and Energy Towers.

• For the appropriate places of installation these Meteorological Reactor Power Stations can annually produce electrical energy respectively from 150GWh to 600GWh.

Where are the appropriate locations to perform the Solar Chimney Power Stations efficiently?

The appropriate locations for Solar Chimney Technology installation should have the following characteristics:
• High annual solar irradiation on horizontal surface (>1700_KWh/m2) (in deserts it can be >2500_KWh/m2)
• High insolation (>3000_hours/year)
• Low average annual winds (i.e 3m/sec)
• Limited strong winds (i.e. 25m/sec)
• No snows, hail or sand storms.
Between the geographical latitudes 40°N & 40°S (in north and south hemispheres) plenty of appropriate places for a broad Solar Chimney Technology application can be found.
For the USA, excellent places for Solar Chimney Technology application can be found in the following States: Arizona, New Mexico, California, Nevada, Texas et al.

Where are the appropriate locations to perform the Energy Tower Power Stations efficiently?

The appropriate locations for Energy Tower Technology installation should have the same characteristics than for Solar Chimneys, but should also
• have very low humidity: i.e. between the geographical latitudes 15 to 30°N & 15 to 30°S
• not too far away from the sea (but neither too close because of humidity) i.e. 30 to 100km

What are the major advantages of these technologies (solar chimneys and energy towers) in comparison to the major existing electricity generating Power Plants?

The major advantages of these technologies in comparison to conventional fuel consuming electricity Power Plants (coal, conventional oil, natural gas, biomass, nuclear) are:
• zero fuel cost
• zero CO2 emissions during electricity production (limited CO2 emissions during construction)
• no methane emissions (Hydro Electric Power Plants do emit methane and CO2 due to organic material decomposition (wood, leaves…), coal and gas power plants also!
• no SOx and NOx emissions
• lower maintenance costs
• lower operational costs (the turbines of solar chimneys work at almost a constant speed and temperature all the time)
• only sea water consumption for Energy Towers
• no water demand for Solar Chimneys (with Wind they are the only Power Plants that do not consume water for operational purposes: even concentrating solar needs huge amounts of water, as the “Carnot cycle’ needs a cold source and a warm source!). Water (very few) is only needed for cleaning purposes and to remove dust from the glass of the greenhouse
• although their construction costs are higher or similar per nominal MW, their yearly production cost per KWh is lower or much lower due to its zero fuel costs and to a 24 h/day operation (similar cost of produced KWh than nuclear plants; lower cost of produced KWh than coal, oil or gas plants; much lower production costs than wind, solar concentrating and solar PVs plants, or other renewable energy plants)
• the life expectancy of a power plant is more or less of 20 – 30 years for wind and solar, 30 – 40 years for oil and coal, 40-50 years for nuclear and gas, 50-60 years for Energy Towers and it is estimated to be 100 – 120 years for Solar Chimneys!

The major advantages of Meteorological Reactors technology in comparison to other solar electricity Power Plants (Photo-Voltaic, Solar Concentrating) and to wind Turbine electricity Power Plants are:
• 24 h/day operation with an almost guaranteed power production profile year round
• almost all the appropriate raw materials and technologies to build the chimneys, towers or greenhouses can be found locally or very close in the surroundings of the site where the power plant will be built. Except for the turbines, almost no importations and no technology transfer are needed by any country to build the meteorological reactor plants.

Can the high chimney collapse under its own weight?

The walls are larger at the bottom and thiner at the top. But even if chimney walls are build at minimum cost, the foremost world experts made calculations in order to make the solar chimney one of the safest structures ever built.

Is it true that a chimney fell down?

The chimney of the Mazanares pilot plant in Spain was designed with a life of only three years. It was design for experimental purposes and was only a project pilot. After nine years of successful service, it was stopped because no more funding. As a matter of fact the price of the electricity produced with fossil energy was lower at the end of the 80’s than the one produced by the solar chimney whose high was only 195m (to be competitiveit needs to be at least 600m high). Because of the lack of maintenance (and the chimney was cable-stayed), the chimney fell during the cyclone of 1989 that put down so many trees in Europe (similar to the ones of december 1999 and january 2009). That was 6 years latter than life expectancy: not bad for a pilot projet with no maintenance!

Does this high chimney pose a threat during a catastrophy?
Are solar chimneys or energy towers endangered by earthquakes or strong winds?

Solar Chimneys are designed to withstand all natural disasters like storms, earthquakes etc. at the specific site, failure due to natural disasters is completely unlikely.
Again: the foremost world experts made calculations in order to make the solar chimney one of the safest structures ever built.
Like any structure it can be destroyed by sabotage. Nuclear power stations pose a threat to the entire region, hydro power stations a threat to the whole downstream valley. Coal-fired power stations pose a threat to the people working inside the power block (40 per shift) and nearby villages if the fuel stockpile of coal dust is sabotaged, which has one third of the blasting power of dynamite. Also oil- and gas-fired power stations pose serious threats to the neighbourhood. Oil spillage causes serious threats of fire and environmental pollution during storage and transport. Even if a very tall chimney falls down, it can only hit the inner part of the greenhouse.


Source = Australian Government:

Who is EnviroMission?
Melbourne based EnviroMission is a newly formed green energy public company that listed on the ASX on August 6, 2001.

The company claims ownership to an exclusive licence to innovative Solar Tower technology. We aim to establish our first 200MW solar thermal power station using this technology in Australia by September 2005.

What is the Solar Mission Project?
The Solar Mission Project is EnviroMission’s program to establish solar thermal energy generation as a commercial alternative in the Australian energy market.

The Solar Mission will adapt the unique German designed Solar Tower technology to Australian conditions.

What is Solar Tower Technology?
Solar Tower technology is not simply solar energy.

Solar Tower technology is created when the sun’s radiation is used to heat a large body of air, which is then forced by the laws of physics (hot air rises) to move as a hot wind through large turbines to generate electricity.

A solar thermal power station using Solar Tower technology will create the conditions to cause hot wind to flow continuously through its turbines to generate enough electricity to power about 200,000 homes.

What will a Solar Tower power station look like?
The power station will be based on German designed Solar Tower technology.

It will look like an enormous greenhouse canopy with a very tall hollow ventilation Tower located at its centre (see artist’s’ impression elsewhere).

The sun’s radiation will be collected and trapped under the transparent canopy, creating a massive force of air heated to around 35°C greater than the ambient temperature.

The laws of physics will make this air move at 15 metres per second towards the cold air at the top of the Tower located in centre of the canopy.

The powerful updraft will force the rising air to pass through large turbines positioned at the base of the Tower.

The movement of the hot wind through the turbines will generate up to 200MW of clean, emission free electricity – enough electricity for 200,000 typical Australian homes.

What materials will be used?
The solar thermal power station will be composed of three major components: the solar collector, Solar Tower and turbines.

The large solar collector canopy will be constructed from a transparent material (maybe glass, but more likely to be a type of plastic to save weight) with heat enhancing properties.

The Tower will be constructed from reinforced high strength concrete.

The large-scale turbines will be purpose designed and constructed from lightweight alloy materials like those used in aircraft manufacture.

How many hours in a day will it generate electricity?
EnviroMission’s solar thermal power station will generate electricity 24-hours a day.

The power station will be at its most efficient on hot days when energy is most needed and peak prices are paid for electricity.

Innovative design will enable the power station to store heat and continue to generate energy during the night.

This special feature enhances the commercial viability of the power station and gives the project a consistent competitive advantage over other forms of renewable energy generation.

What factors determined the Tapio Station site?
EnviroMission’s commercial optimisation study took several issues into consideration before it chose Tapio Station as the preferred site for the first power station. These factors include:

Solar radiation levels
Weather patterns
Geological stability
Access to the electricity grid
Geographic features
Current land use
Environmental factors
Federal Government support
State Government support
Local Government/regional support

Aerial view of Tapio Station Site (Australia)

Can it be built?
A technical review report prepared by Sinclair Knight Merz, one of Australia’s leading engineering specialists, independently agree the proposed solar thermal power station’s design concepts and construction methods are well proven and it can be built in Australia.

A 50kW prototype Solar Tower plant was constructed and successfully operated in Manzanares, Spain, with involvement of the designer Professor Jörg Schlaich, and the Spanish Government in 1982.

The prototype operated for seven years and conclusively proved the technology works. The data obtained from this prototype has provided the basis for a scaled up 200MW generation plant.

Why wasn’t it built earlier?
For more than 100 years it has always been cheap and simple to dig up and burn coal to produce electricity.

However, enormous shifts in community values across the world and growing concern about the environment, global warming and pollution over the last 20 years has led to a demand for methods to generate renewable, clean green energy.

In Australia, increased community concern about our over reliance on coal based ‘black’ energy and its negative impact on our environment is driving political change.

There is now a legislated market for clean, green renewable energy. This development has opened the way for investment in new approaches to green energy generation.

New materials and construction methods have been developed to the point where Solar Tower technology can now be applied in an economically viable way.

Is Solar Tower Power Competitive?
The selling price of Solar Tower renewable energy is based on the average peak pool electricity price paid to generators plus an additional renewable energy credit incentive paid by retailers.

This makes it as competitive as ‘black’ energy and competitive with other renewable generators.

What is the Green Energy Market?
Over the past 10 years, control of greenhouse gas emissions has become an issue of major international concern because escalating levels of CO2 are now proven to be a direct cause of global warming.

Worldwide environmental performance of energy industries, particularly the electricity sector, has been subject to close examination as they are major contributors to the production of CO2 greenhouse gases.

In 1997, the Federal Government mandated through legislation that 9500GWh of Australia’s electricity supply must come from clean, green renewable sources by 2010.

The government’s commitment to green energy generation is part of a national strategy to meet 1996 Kyoto obligations to reduce CO2 emissions.

Most of Australia’s electricity needs are met today by black and brown coal fired power stations, which account for more than 35% of our nation’s greenhouse gas emissions.

Less than 10% of all electricity generated in Australia is generated from alternative, renewable, clean energy sources.

Each EnviroMission 200MW solar thermal power station will abate over 900,000 tonnes of carbon dioxide from entering the environment annually.

Source = Australian Government:

Meteorological Reactors