Reinhard Harte

New natural draft cooling tower of 200 m of height

In the years 1999 to 2001 a new natural draft cooling tower has been built at the RWE power station at Niederaussem, with 200 m elevation the highest cooling tower world-wide. For many reasons, such structures can not be designed merely as enlargement of smaller ones, on the contrary, it is full of innovative new design elements. The present paper starts with an overview over the tower and a description of its geometry, followed by an elucidation of the conceptual shape optimization. The structural consequences of the flue gas inlets through the shell at a height of 49 m are explained as well as the needs for an advanced high performance concrete for the wall and the fill construction. Further, the design and structural analysis of the tower is described with respect to the German codified safety concept for these structures. Finally, the necessity of extended durability of this tower is commented, the durability design concept is explained in detail and illustrated by virtue of a series of figures.

On adaptive remeshing techniques for crack simulation problems

The simulation of fracture processes for discrete crack propagation is well established for linear‐elastic cracking problems. Applying finite element techniques for the numerical formulation, at every incremental macro‐crack step the element mesh has to be adapted such that the crack path remains independent of the initial mesh. The accuracy of the obtained results has to be controlled by suitable error estimators and error indicators. Considering the dependence of the predicted crack path on the precision of the displacement and stress computation, quality measures for the computed results are recommended. In this research the use of the Babuska/Rheinboldt error indicator in combination with linear‐elastic crack propagation problems is demonstrated. Based on this error measure an adaptive mesh refinement technique is developed. In comparison with classical discrete crack propagation simulations the advantages of the new concept can be clearly observed.

Large-scale cooling towers as part of an efficient and cleaner energy generating technology

Abstract The present paper will outline the main aspects of the design and construction of cooling towers in Germany in the last decade. As part of electricity generating power plants, cooling towers play a significant role for the availability of reliable energy supplies, in a manner compatible with environmental requirements. They definitely belong to the largest and thinnest concrete structures at present. Because of the combined action of wind, thermal and moisture effects, special care has to be taken with regard to fatigue, cracking and corrosion to ensure an adequate level of safety and durability. Such a design strategy has been employed for the world’s tallest cooling tower at the Niederaussem power plant in Germany, with an overall height of 200 m and thickness values of 22–24 cm. Special considerations included the realistic non-axisymmetric distribution of soil characteristics, wind action due to interference effects (as determined by wind-tunnel tests), optimisation of the shell shape to improve structural and dynamic behaviour, injection of the cleaned flue-gas into the cooling tower, and the use of high-performance concrete (85 MPa) to improve shell resistance against acid attack by the cleaned flue-gas. The paper will present some results of an actual research project on this problem, which was conducted at the University of Wuppertal, to explore the use of high-performance concrete on design, stability and durability of cooling tower shells.

Tensor-orientierte Formulierung nichtlinearer, finiter Schalenelemente

ÜbersichtIn unmittelbarer Anlehnung an die Tensorformulierung geometrisch nichtlinearer Flächentrag-werkstheorien werden besonders genaue, finite Weggrößenmodelle hergeleitet. Sie sind für beliebige Schalen-formen einsetzbar und dienen insbesondere zur Simulation kritischer und überkritischer Systemantworten. Der vorliegende Aufsatz beschreibt die Herleitung der Elemente und überprüft deren Konvergenzverhalten und Leistungsfähigkeit.SummaryIn accordance with the tensor formulation of geometrically nonlinear shell theories high precision finite displacement models will be developed. They can be applied to arbitrarily curved shell shapes and are especially able to simulate critical and supercritical mechanical responses. The paper describes the derivation of the elements and investigates their convergence behavior and efficiency.

From Cooling Towers to Chimneys of Solar Upwind Power Plants

Natural draft cooling towers and chimneys of solar updraft power plants have many structural properties in common: They are dominated by thin ring-stiffened shell structures made of reinforced concrete, they transport by their internal updraft warm air into the atmosphere, and because of their height, gale actions play the most important role in the design.

Simulation of static and kinetic buckling of unstiffened and stiffened cooling tower shells

Abstract Natural draught cooling tower shells are loaded mainly by their dead weight and by the wind, which may both cause buckling failure. The present paper compares various numerical procedures to investigate the stability behaviour of cooling tower shells. These are a complete nonlinear analysis, a linear eigenvalue analysis for a stationary non-axisymmetric wind load, and a linear eigenvalue analysis for a wind load, approximated to be axisymmetric. The aim is to evaluate whether a geometrically nonlinear analysis can be replaced by a time-saving classical buckling analysis, probably even for an axisymmetric state of stress. The third procedure, as the most conservative, but a very effective one, will be applied to investigate the mechanical influence of ring stiffners on the buckling behaviour of cooling tower shells. Kinetic instability phenomena will also be examined. The structural improvement resulting from ring stiffeners will be quantified and summarized in design recommendations.

Optimization of Solar Updraft Chimneys by Nonlinear Response Analysis

Solar updraft chimneys (SUCs) form as engines of solar updraft power plants tower-like shell structures of extreme height with rather thin shell walls, similar to high chimneys comprising multiple flue gas ducts. The height of pre-designed SUCs presently reaches up to 1000 m. Thus they are exposed chiefly to extreme wind-loads and thermal actions from the internal flow of warm air. As first design attempt, the structural analysis of solar chimneys generally is carried out by linear elastic models. For optimization, the typical shell-like wind stresses have to be constraint towards a more beam-like response behavior, approaching as far as possible linear stresses over the entire chimney circumference. This requires rather strong ring stiffeners, either as spoke-wheels in the designs of sbp (Schlaich Bergermann and Partners) or as external stiffeners in the designs of K&P (Krätzig and Partners). Both alternatives require considerable construction efforts leading to high investment costs. There exists an interesting simplification of this stiffening, namely applying to the SUC shell relatively soft external rings, and admitting large-widths cracking in the limit state of failure. This cracking constraints and equalizes the meridional stresses over the chimney’s cross-section, saving large amounts of reinforcement steel in the SUC. The design requires materially nonlinear analyses to verify the internal forces under crack-formations. The manuscript will derive this concept and demonstrate the crack analysis by example of a 750 m high solar chimney.

Lifetime-Oriented Analysis and Design of Large-Scale Cooling Towers

Publisher Summary This chapter discusses the main aspects of the design and construction of cooling towers in Germany in the past decade. These towers definitely belong to the largest and thinnest concrete buildings worldwide at present. Because of the combined action of wind, thermal, and hygric effects, special care has to be taken on fatigue, cracking, and corrosion to insure an adequate level of safety and durability. Such a design strategy has been employed for the highest cooling tower worldwide at the power plant at Niederaussem/Germany, with an overall height of 200 m and thicknesses of 22 to 24 cm, under special consideration of the realistic non-axisymmetric distribution of soil characteristics and wind action due to interference effects, as they have been examined by wind-tunnel tests; the optimization of the shell shape to improve the structural and dynamic behavior; the injection of the cleaned flue-gas into the cooling tower; the use of high-performance concrete to improve the shell against acid attack by the cleaned flue-gas. The chapter reveals some results of an actual research project on this problem.

World’s Tallest Natural Draft Cooling Tower, near Cologne, Germany

RWE Energie AG, the second largest German electricity producer, operates since 1961 a lignite power plant at the small village of Niederaussem, 20 km west of Cologne. Construction began on a new Niederaussem power station in 1998 with an intended electricity capacity of 965 MW, which, after completion in 2002, will become the largest lignite power block in the world. The cooling component of this new electricity station is a natural draft cooling tower 200 m high, the tallest cooling tower and the largest shell structure in the world. The reason for increasing height and cooling capacity to such an extent is merely the desire to enhance the total net efficiency of the electricity generating process at this plant, as one of several innovative steps.

DESIGN AND CONSTRUCTION OF A PROTOTYPE SOLAR UPDRAFT CHIMNEY IN ASWAN/EGYPT

This work is part of a joint project funded by the Science and Technology Development Fund (STDF) of the Arab republic of Egypt and the Federal Ministry of Education and Research (BMBF) of the Federal Republic of Germany. Continuation of the use of fossil fuels in electricity production systems causes many problems such as: global warming, other environmental concerns, the depletion of fossil fuels reserves and continuing rise in the price of fuels. One of the most promising paths to solve the energy crisis is utilizing the renewable energy resources. In Egypt, high insolation and more than 90 percent available desert lands are two main factors that encourage the full development of solar power plants for thermal and electrical energy production. With an average temperature of about 40 °C for more than half of the year and average annual sunshine of about 3200 hours, which is close to the theoretical maximum annual sunshine hours, Aswan is one of the hottest and sunniest cities in the world. This climatic condition makes the city an ideal place for implementing solar energy harvesting projects from solar updraft tower. Therefore, a Solar Chimney Power Plant (SCPP) is being installed at Aswan City. The chimney height is 20.0 m, its diameter is 1.0m and the collector is a four-sided pyramid, which has a side length of 28.5 m. A mathematical model is used to predict its performance. The model shows that the plant can produce a maximum theoretical power of 2 kW. Moreover, a CFD code is used to analyse the temperature and velocity distribution inside the collector, turbine and chimney at different operating conditions. Static calculations, including dead weight and wind forces on the solar updraft chimney and its solar collector, have been performed for the prototype. Mechanical loading and ambient impact on highly used industrial structures such as chimneys and masts cause lifetime-related deteriorations. Structural degradations occur not only from rare extreme loading events, but often as a result of the ensemble of load effects during the life-time of the structure. A Structural Health Monitoring (SHM), framework for continuous monitoring, is implemented on the solar tower. For the ongoing case study, the types of impacts, the development of the strategic sensor positioning concept, examples of the initially obtained results and further prospects are discussed. Additional wind tunnel tests have been performed to investigate the flow situation underneath the solar collector and inside the transition section. The flow situation in and around the SCPP has been simulated by a combination of the wind tunnel flow and a second flow inside the solar tower. Different wind tunnel velocities and volume flow rates have been measured respectively. Particle Image Velocimetry (PIV) measurements give some indication of the flow situation on the in- and outside of the solar tower and underneath the collector roof. Numerical simulations have been performed with the ANSYS Fluent to validate the experimental tests.