Risk Assessment

3. Risk of Earthquakes

Due to the September-2005-Kashmir-earthquakes of magnitude 8,1 the question arises, whether a 1 500 m tall chimney flue would not pose too high a risk for a GT in Rajasthan. A seismic map of India from 2003 (not shown here) indicates the different risk zones according to seismic activity in the past. The dark red zone V shows the highest risk of seismic activity where earth-quakes of magnitude 8 or more might occur, which greatly coincide with the southern seam of the Himalaya Range where the tectonic plate of the Indian subcontinent is sliding in below the Eurasian tectonic plate, i.e. the Tibet Plateau by 4 m to

5 m/100 years, of which 2 m/100 years is stored elastically in the Himalaya Range, which energy is released in earthquakes. At present an 8 to 12 m elastic compression’s energy is stored in the southern Himalaya so that alongside its whole border line heavy earthquakes are indeed overdue with the Kashmir earthquake apparently being the first.

Notably New Delhi in the medium red zone IV had between June 1992 and November 1994 eight earthquakes of magnitudes between 2,5 and 3,5 not leading to any recorded damage, which shows that seismic activity and the risk of heavy earthquakes quickly decrease with increasing distance to the southern Himalaya seam. Hence the area for the envisaged 4 GTs near Jaipur, Rajasthan, in the yellow zone I shows for practical purposes no seismic risk at all.

If, however, a slight seismic risk would be sensed in for instance the pink zone III, GTs could easily and cheaply be stabilized by cables from the 7 compression rings of the spoke wheels (for a circular cross section) down to the outer foundation circle of 600-700 m diameter. Hence GTs can be built in nearly the whole of India with small structural changes without any undue risk. Earthquake-resistant structures for high risk areas are available but at higher cost.

In the unlikely event that the seismic risk in a given area has been completely misjudged, the worst case of the 1 500 m chimney flue coming down can never result in heavy loss of life, as only 3 persons are present in the central collector area with a radius of 2 km. The greenhouse workers are automatically protected against broken glass by the shadow nets and the collector structure can be made earthquake-resistant at low cost.

This stands in sharp contrast to the envisaged 150 000MW hydro power from large river dams at the outskirts of the Himalaya valleys, all of which are prone to complete failure through earthquakes above magnitude 8 soon to be expected. Compared to the tenfold increased population density in the Ganges River system since 1934 loss of human life would run into millions, if the envisaged dams would fail. Since the power potential of the rest of the country is only about 10% of the Himalaya-rivers, hydro power can due to this high risk not contribute significantly to the future power mix in India. Small flow of the river power stations would not only diminish the hydro potential by 70% but would make hydro power unaffordable.

The GT sites in Namibia-Botswana, UAE-Oman etc. carry no seismic risk.

4. The Large Collector

Since adversaries and surprisingly also the renowned US research unit Sunlab are pretending that the large-GT-collector/high-yield greenhouse poses a grave threat to the environment requiring an expensive in-depth impact assessment and possible prohibitive actions, we have to address this “risk” here. Have forests, including tropical rain forests and large farming areas suddenly become a “grave threat” to the environment, or was Sunlab jesting?

The thermal up-draft caused by the sun heating the ground is the real cause for all winds and jet streams in the atmosphere, rain, storms and the global wind system with the sea currents. If this up-draft is inhibited by very large, densely packed PV panel or solar thermal mirror fields, the solar radiation does not reach the ground and the up-draft is stopped with negative effects to the atmosphere and the environment. Contrary to that, the GT and Prof. Schlaich’s Updraf Tower (Solar Chimney) do not inhibit the up-draft, but concentrate it at the chimney flue to a height of 1 000 m/ 1 500m, above which it mixes again with the ambient atmosphere undoing the concentration. The GT can thus be applied at any scale without any environmental risk.

A great concern with all solar technologies is the extensive use of land due to the sunlight’s low energy concentration. However, no land is sterilized by the large GT-collector, since the GT-greenhouse will increase production of a highly productive agricultural area from 100% to at least 270%, adding a virtual 170% to the existing land. These calculations are mainly based on Prof. Kröger’s experimental and theoretical findings in 2000, showing that vegetation in the collector increases heat and power production – a breakthrough in GT research! The high greenhouse yields and profits have been established by the Roodeplaat Research Centre, Pretoria, the Zentrale Markt- und Preisberichtstelle, Bonn, and others and have been calculated very conservatively, so that no risks are involved regarding the financial forecasts for the greenhouse’s profits, whilst in India the relation of profit to cost is even better.

The conversion of the greenhouse’s large amounts of biomass to humus to be buried in the soil resulting in high CO2 sequestration makes the GT, in addition to the lack of any environmental risk, the purifier of the atmosphere, reversing the greenhouse effect, if applied at large scale. The GT-tendency to become the nucleus of an ever increasing oasis makes it the natural driving force to cultivate the globe’s huge desert areas, leading to a general improvement of the earth’s climate. Experimental research proved a root growth of one meter in three days by optimal use of humus, as in the GT, so that sane organic agriculture will be combined with the highest possible yields. Seeing all these environmental advantages we conclude that Sunlab was jesting indeed by labeling the large GT-collector a special threat to the environment. Contrary to Sunlab’s surprising lack of insight we note that also the GT-greenhouse is very well researched, minimizing any potential risk in production or profit.

5. Agriculture in the Greenhouse

As the GT-collector becomes progressively hotter toward the centre, many questions arise about the risks of soil-based agriculture in this huge, air-cooled greenhouse:

v Question: Will the strong winds in the greenhouse affect the plants negatively?

Answer: No, since the horizontal shadow nets will effectively separate the air space above and below. Strong winds will only occur above these nets.

v Question: Can the plants stand the high temperatures of a hot summer day + additional heating?

Answer: The continuously adaptable shadow nets will limit the visible radiation below in a controlled manner during the day, so that incoming radiation, causing heat, will be restricted. Water evaporation associated with CO2 assimilation during the day causes strong cooling, so that these combined effects always keep the plants below the stress temperature.

v Question: Will the shadow from the nets reduce plant production in the greenhouse?

Answer: On the contrary: With a 50% translucency of the shadow nets the visible radiation below is nearly 100% diffuse, reaching all parts of the plant and not only the top leaves. Assimilation and plant growth is thus much higher as also a sound cooling by evaporation.

v Question: Will the daily 22 hour airtight separation of corresponding greenhouse compartments for re-condensation of water cause CO2 deficiencies?

Answer: No, since additional CO2 will be supplied from other GT sources at no cost.

v Question: Will the puddles of re-condensed water on the floor cause root diseases?

Answer: No, since the soil will absorb the condensed water like a sponge due to its high humus content and distribute it evenly in the soil through the fine humus capillaries.

v Question: Will certain (pseudomonas) bacteria in the soil, which are normally removed by frost, not cause serious root diseases?

Answer: In the GT greenhouse frost does not occur, but the killing of these germs can also be done by heat. With open shadow nets at mid-day 90°C at the soil surface will kill them.

v Question: How do you remove seeds from preceding crops from the greenhouse soil?

Answer: Even with meticulous working one cannot remove all seeds before planting a new crop. One thus prepares the soil well and let the seeds germinate. A temperature of 90°C (shadow nets open) and no water will kill the unwanted shoots. As the wanted crop is planted thereafter, the old seed cannot interfere anymore.

v Question: Will the soil-based big-greenhouse agriculture not sustain all sorts of plagues?

Answer: This would be true with a standard soil but is not true with the GT-humus soil, containing high concentrations of natural antibiotics, which will check all plagues. The very fast root and plant growth in the GT often causes the plant to outgrow the plague/disease.

v Question: Will the intensive GT-agriculture not exhaust the soil very fast?

Answer: The assumption underlying this question is that all nutrients for a given crop have to be added to the soil before planting. In general, however, the nutrients are already in the soil. It needs the right organisms to break these mineralized nutrients down and to make them root accessible. As the special GT-humus will enhance soil life by the factor 1 000, all the necessary organisms will be present and will find the best possible environment to abundantly supply plant nutrients. The more humus is present in the soil and the better the quality, the more new high quality humus will be formed from old root material, as artificial resting periods for the soil can be managed in the GT-greenhouses.

v Question: Will the high greenhouse production not starve through nitrogen deficiency?

Answer: As nitrogen-fixating bacteria, free-living in the soil, can supply enough nitrogen to the plants, if the humus content in the soil exceeds 10%, 12% humus and the corresponding bacteria will be added to the soil (33cm deep) at the beginning. Thereafter no further nitrogen fertilization is required, as the bacteria multiply according to root growth.

v Question: Is this humus agriculture not very expensive and thus financially risky?

Answer: As eight million ton of “mature compost” have been offered to the author f.o.b. port North Sea to be transported by huge ore carriers, returning empty to South Africa, compost can be brought to the whole African west coast at cheap back freight rates. Initial surveys show that biomass for composting can be obtained in Rajasthan at ± the same or lower cost. Hence the GT-humus-agriculture is financially more rewarding than its current power production, which in turn is the most rewarding of all present power technologies.

Hence there is no financial or environmental risk involved in the GT greenhouse high-intensity agriculture.

6. The Turbine

Firstly we note that Prof. von Backström of Stellenbosch University achieved a great breakthrough by increasing the low air/angular speed turbine’s (fan’s) design efficiency from previously 70% to more than 90%, which is demonstrated by several models there.

After the original Schlaich (Voith) turbine design shrank to 130m for problems with conventional generators, it became too small for the efficiency/cost-wise advantageous GT-1 500m-chimney.

Linear generators (used in Transrapid trains) at the circumference and maintenance-free permanent magnet bearings are now used for the 32 integrated GT-generator-turbines of 30m Æ. Since rotor blades are also suspended at the circumference, stresses in the central hub are minimal, prolonging life expectancy significantly. These wear- and friction-free bearings are self-centering, excluding damage through imbalances, which in 2003/4 destroyed four 700MW steam turbines in South Africa. The new design minimizes technical/financial risks and saves cost.

7. What makes the GT Technology so Reliable?

The seven year faultless, nearly continuous operation of Prof. Schlaich´s Updraft Tower (Solar Chimney) (SC) pilot plant in Spain, the best result of any power generating technology hitherto, was no accident, as it is by its very nature the most simple and reliable (heat) “engine”:

A. Heat Generation

¨ GT collector: Heat is generated stress-free solely by the visible solar radiation, being absorbed in the soil and raising air temperature in the collector by 76°C; no moving parts;

¨ Fossil fuels: Tedious mining/drilling/pumping operations; complicated transport to the combustion chamber of an internal or external heat engine; high heat (1 100 to 1 300°C) and mechanical stress in the internal and external combustion chamber; complicated mechanical fuel injection and ash removal under high temperatures; heat transfer from combustion chamber to boiler of steam engines through fume pipes under high boiler pressure in an aggressive medium.

B. Pressure Difference – Mass Flow Generation

¨ GT collector + chimney flue: Pressure difference inside the GT is less than one bar and causes a gentle sucking action in the chimney through the weight difference between the hot, light air inside the chimney and the cooler outside air, using a low temperature difference and a non-aggressive medium (air); no gusts; no stresses; no moving parts;

¨ Fossil fuel technologies: High pressure (90 bar plus) and temperature (550°C plus) in ex-ternal boilers and shock waves (several 100 bar in internal combustion engines, aggressive working media (hot steam, combustion fumes) and high wear on piston rings, turbines;

¨ Hydro power: Medium pressure (10 to 30 bar), aggressive medium water; wear on turbines;

¨ Wind generators: Very high stresses in central hub/bearings and in centrally supported long rotor blades; uncontrollable gusts and heavy load differences in time and over cross section.

C. Power Control

¨ GT: Pitch control of slowly rotating turbine blades with low-stress doubly supported turbine blade bearings + central control of heat transfer from quick-response hot water energy stores; the extremely unlikely failure of control in one turbine or one water pond will affect less than 3% of total power delivery Þ constant availability of 97% plus can be guaranteed;

¨ Fossil Fuels: Complicated fuel injection at high temperatures + mass flow control through valves at high temperatures and pressures; failure of one valve stops whole power train; routine checks and/or repairs will stop the whole power train.

¨ Hydro power and wind turbines: Whole power train stops with repair/maintenance;

The GT working mechanism itself ensures the lowest possible heat/mechanical stress on all components and the absolute minimum of moving parts making it the most reliable technology.

8. Power Generation

People often feel uncomfortable with the big leap from the 50kW pilot plant to a 200/400MW power station and propose an approach in steps. Since power generation is directly proportional to chimney height and a 1 000m chimney would be out of proportion with a 1MW or 10MW power plant, small plants show a poor performance and are too expensive for demonstration. This problem was solved by contracting the leading world expert on thermodynamics and flow dynamics of cooling towers, Prof. Kröger of Stellenbosch University, to calculate the GT power production and to guarantee his calculation, whereupon an insurance policy for a guaranteed power delivery will be issued at the end of the feasibility study.

The insurance policy will cover the cost of the collector’s enlargement to compensate the shortfall of power generation. Assuming an unlikely shortfall of 10% the collector area will be augmented by 11% at the periphery with an increase of 16% of the greenhouse area. This will restore the 100% design profit from power sales, but at the same time create additional greenhouse profits of 330% of the first 10% financial shortfall (profits from greenhouse more than twice those from power). Hence the insurance company will only supply the building loan with a low short-term guarantee-interest replacing the premium.

Prof. Kröger will by agreement publish the worst case power figures. He will close the gap between best and worst case to 10% or less. This will not be easy, since the driving force, i.e. the buoyancy difference between the air column inside and outside the chimney is very small compared to the buoyancy of the two columns themselves, augmenting every error in measurement 10 to 20-fold. For this reason Prof. Kröger has already developed a refined model of the ambient atmosphere, which will become exact with real time measured parameters of the microclimate on site. Incidentally, his first calculations on the Updfraf Tower (Solar Chimney) confirmed Prof. Schlaich’s figure of 200MW for the Updraft Tower (Solar Chimney) as average between best and worst case. The 400MW-GT improvements were not contained in Prof. Kröger’s first calculations. They will be part of the present pre-feasibility and feasibility study.

Measurements at the low lying Sishen mine in the eastern Kalahari in South Africa showed an inversion layer of 300 m thickness and 17°C temperature difference at ground level during winter nights, reducing power generation during winter by 9%. To avoid these “cold air lakes”, which are part of Prof. Kröger´s calculations above, the GTs, envisaged to be built in India, Namibia, UAE etc. will be erected on escarpments standing out of these lakes. Cold air flowing down mountain slopes will be barred from entering the collector and led to pass by. Much power can be gained by an exact determination of the microclimate based on past GT research.

Past research showed that the IR-radiation losses to the sky caused high energy losses. With the world’s leading research unit on solar glass, the Fraunhofer Institute in Freiburg, it was established that the IR-reflecting-sunlight-translucent layer of the company Interpane in combination with double-layer insulating glass will raise collector efficiency from 45% to 90% at modest cost and will double power output. Iron-free glass and the SA Atomic Energy Corporation’s anti-reflection layer will additionally increase power output by 12%.

Re-condensation of greenhouse-evaporated water will cut evaporation losses by ± 95%. The gains, shown above, will finally be proved during the feasibility study in two 500m glass tunnels with wind fans mounted at the small ends, resembling part of the collector. This will also prove Prof. Kröger’s flow dynamic calculations experimentally and thus remove even the slightest risk from his power production forecast.

9. The Thermal Energy/Water Store

Since solar/wind power generation does normally not coincide with demand, low-cost energy stores are imperative for these technologies to be competitive. Only the Updraft Tower (Solar Chimney) / GT low temperature plant has such very cheap energy stores in the form of closed water ponds at the collector’s floor in the central non-greenhouse part. When the 1996 energy store was not performing well, it was re-designed in South Africa in 1999 and successfully tested.

Prof. Kröger´s experimental research at Stellenbosch University proved that the new heat transfer control is of special importance. It performs extremely well and allows extension of the central quick-control energy store to six days full production and a reaction time of only four minutes from 10% to 100% power production. Though only being tested on a small scale, exact forecasts on the full energy store’s performance are conclusive and without any risk, since the heat transfer coefficients are well known, whilst the single pond contributions just add up.

The cheap seasonal store (six months) was tested in Germany and is state of the art there. Hence the proven GT energy stores do not present any financial or functional risk.

10. Conclusion

The GT technology does not pose any threat or risk to the environment or any significant structural or financial risk, as it uses only state of the art technology, though in new combination. It is dearly needed to replace the dwindling fossil energy reserves, to reverse global warming and to improve the climate through cultivation of deserts. Only a fraction of the high quality research done could be shown here. The GT is hitherto the most thoroughly researched emerging power technology, and where components were tested, the function of the whole system was also taken into account. The leading world experts working on this exciting project achieved a state of maturity which is unprecedented for an evolving technology. Without being sure of success they would not have thrown in finance and their professional weight.

In a similar unprecedented manner all problems and risks were addressed so successfully that today about 34 patents are in preparation. The diminution of financial risks by insurance policies also gives a good indication that the actual risk of structural failure or shortfall of power is negligible. Hence the risk of investment as also functional and financial failure of the GT is virtually zero.