In the course of the current energy transition and the move away from fossil fuels, research into new systems for energy conversion is very important. In this context, the generation of energy from solar radiation is of particular interest. For several years, the working group has been scientifically engaged in the development of so-called solar updraft power plants, which can be used especially in sunny regions of the earth. The power plant basically consists of a very large reinforced concrete chimney of up to 1500m height, which is surrounded by a glass roof of several square kilometers. The air under the glass roof heats up due to solar radiation and flows to the chimney, in the foot area of which there are turbines that then convert the kinetic energy of the air flow. Despite advanced planning and calculations on a theoretical basis, many construction and operational aspects of such a power plant are still unexplored. Within the framework of a German-Egyptian project, a research power plant has now been planned and built on a smaller scale in Egypt, near the city of Aswan, since 2013, under the leadership of the Bergische Universität Wuppertal, Chair of Statics and Dynamics of Structures, Prof. Dr.-Ing. R. Harte, and in cooperation with the University of Aswan, Egypt. The power plant site can be seen in Figure 1 and is one of the sunniest and warmest regions in the world, with about 4000 hours of sunshine per year and an average temperature of 40°C for more than half the year.
The chimney of the research power plant is 20.1 m high and made of steel. This is connected to an octagonal, 80cm thick concrete foundation via a spatially braced steel frame structure, as shown in Fig. 2. Surrounding the tower base is a square glass collector, each with an edge length of 20m and a height above ground of 1.25m. The entire research power plant shown in Fig. 3.
The task of the project partner WiSt at the Ruhr University Bochum is the estimation of the structure lifetime as well as a structural safety-based life cycle monitoring. For this purpose, the ensemble of selected mechanical reactions as well as detectable damage to the structure are recorded by measuring stresses and accelerations with strain gauges and acceleration sensors (see Fig. 4) on the chimney at different heights. The resulting early prediction of damage development or increase influences the repair costs and also the service life of the structure. The main effects are wind and temperature loads as well as loads from turbine operation. In principle, seismic effects can also be recorded.
Another research focus, which lies with the project partner WiSt at the Ruhr University Bochum, is the consideration of dust and sand deposition on the collector roof. In the very arid area, particles of various sizes are transported by the wind and deposit on the collector, especially in zones of lower wind speeds. This deposition of material on the collector can greatly affect the efficiency of the power plant by reducing the translucency as a result of the outer surface fouling to shading, and can also cause damage to the collector surface. Cleaning of the glass roof is a cost factor that depends on the severity of the deposit. Velocity measurements of the wind flow in the immediate vicinity of the structure and dust measurements with the help of collecting tanks according to VDI 4320-2 are carried out. Additional photos of the collector from above will document the formation and development of deposits on the glass roof. This will be accompanied by numerical calculations using the finite volume method (CFD) and measurements of velocity fields near the structure in the Bochum boundary layer wind tunnel. The data obtained in the large-scale test at the research power plant in Aswan can thus also be used to validate the calculations as well as the experiments in the boundary layer wind tunnel.
This text appeared in Newsletter 2016-1. The entire newsletter can be downloaded from the homepage of the Faculty of Civil and Environmental Engineering.
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Last update: Apr 05, 2023
