Notes on the construction and operation of hydropower plant components – Introduction

VGB TC Hydro and TG Components of Hydro Power Plants

The large-scale use of hydropower for energy generation and storage can look back on more than a century of history. The particular advantages are the inexhaustible availability of the resource, the high flexibility of electricity generation, especially in storage and pumped storage power plants, with a wide range of output and an extraordinarily high conversion efficiency. Hydropower plants, however, are very capital-intensive and achieve their economic viability through a solid, reliable design and a significantly longer operating life compared to other forms of energy generation. Hydropower plants are thus characterised by an extremely high harvest factor and an excellent overall energy balance. Hydropower plants are characterised by their prototype character and long service life. The requirements for long-term operational safety are very high, which results in a corresponding demand for quality in the construction and operation of the plants. This applies in particular to high-performance pumped storage and storage power plants as well as large run-of-river power plants. Nevertheless, in recent years there has been a marked increase in defects and damage, especially to new machinery. The analysis of the causes is necessary in order to effectively counteract this trend with appropriate measures.

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Farewell to coal – Expropriation or common good?

Hans-Peter Schwintowski

The Commission “Growth, Structural Change and Employment” appointed by the German Federal Government on 6 June 2018 submitted its final report on 26 January 2019. The report, the recommendations and the key points adopted by the Federal Cabinet for the implementation of the Coal Commission result in a number of points to be considered: The future decommissioning law for coal-fired power plants raises a variety of ownership issues. The principles according to which an expropriation is to be determined result from the so-called “Nassauskiesungsurteil” and from the judgement to accelerate the nuclear phaseout. The concept of expropriation in Article 14 GG is to be determined from the point of view of Article 17 EU-GrCH and Article 1 1 1.ECHR-ZProt. Apart from this, the law on the preliminary closure of coal-fired power stations must comply with the principles of proportionality, equality, transparency and appropriate burden-sharing between the various CO2-emitting sectors. If and to the extent that this is not guaranteed, the law would have to provide for adequate financial compensation. Since the European Treaty currently does not make compliance with climate protection targets mandatory within the Community, there may be mutual exploitation between Member States which fulfil their obligations under the climate protection agreements and those which do not.

Use of biocides in power plants

Walter Hoffmann and Günter Ritzerfeld

On 19 August 2017, the 42^nd BImSchV, the ordinance on “evaporative cooling systems, cooling towers and wet separators” came into force. The ordinance aims to avoid contamination by microorganisms, in particular Legionella, in the installations within the scope of application and thus to exclude a possible hazard from the emission of cooling tower swaths containing Legionella or exhaust air swaths. The operators of the plants concerned are required to deal intensively with the microbiological condition of their plant and to comply with the test and measure values specified for the parameter “Legionella”. The operator must take appropriate measures to this end. In particular, exceeding the action values can, in extreme cases, lead to the plant being shut down. In addition to a multitude of suitable measures to reduce microbiological activity, the use of biocides is unavoidable in some cases. The technical paper gives a brief overview of the general conditions for the use of biocides in cooling systems and reports on operator experience gained with the use of different biocides.

Leakage assessment in leak-before-break analysis

Klaus Heckmann and Jürgen Sievers

The assessment of a leakage event in an operating nuclear power plan requires a profound knowledge of structural and fluid mechanical phenomena. One relevant situation is the leak-before-break analysis, which analyzes if a leakage can be found while it is small and controllable, which prevents a rupture. The elements of such a detectability analysis require the computation of flow rates through narrow cracks as well the assessment of the stability of flawed pipes. For this purpose, the codes WinLeck and PROST have been developed by GRS. These codes include multiple model approaches, which are useful for the systematic evaluation of laboratory measurements, since modelling effects and other influences can be separated. These codes allow also the processing of a matrix of test cases, which is done in the form of a sensitivity study. Relevant influence quantities for the leak-before-break characteristics turn out to be the pipe size, the friction factor due to the roughness of the leakage path boundaries, the material’s yield stress, the fracture toughness and the detection threshold of the leakage monitoring system.