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The main rules for the selection of the regulation mode of a PAT based on the operating conditions are presented, as measured at the point of the network where the power plant will be located. The variability of operating conditions in water supply networks is discussed and the influence of the daily demand variation of the flow rate and available head drop is established, with the main regulation modes introduced. Finally, the concept of power plant effectiveness is described and the Variable Operating Strategy (VOS) is proposed as the best design procedure. The reader will be introduced to the importance of PAT regulation in a small hydropower plant, and to the main schemes of PAT installation. In particular, he/she will be instructed on to how to perform an advanced power plant design based on the local operating conditions in order to maximize the power plant effectiveness.

A number of existing hydropower plants are described, which have a power generation capacity ranging between a few kW and a hundred kW, thus proving the extreme flexibility of PAT technology. Several different designs are shown, with the best solution depending on the power plant data and on the problem constraints. In addition, the layout of some pilot research systems and the main results obtained during testing are described. The reader will be able to discuss the technical solutions with reference to power plants already realized or under construction in water supply systems, comparing the expected and measured power plant efficiency. Suggestions about the best layout solution for the different cases, based on the results obtained in pilot plants, are provided.

A PAT normally has a lower efficiency than a conventional turbine applied at the same site. In the long term, a higher efficiency is important for users in that more energy is produced. A pump’s geometry can be modified to improve its efficiency in turbine mode. Several methods of PAT geometry modification are presented for the improvement of PAT efficiency. Optimization of the internal pump geometry for reverse use is fundamental also for the reduction of the cost of PAT maintenance. Therefore, the industrial aspects of PAT reliability in terms of different design methods, solutions and recommendations are described. Practical technical skills relating to the PAT inlet/outlet parts and impeller geometry modification in order to improve the PAT efficiency are presented. Basic concepts in relation to mechanical reliability are given and the analytical methods to assess the reliability of an industrial PAT are provided.

PATs are a viable and low-cost solution suitable for implementation in water networks. The basic economic parameters, the time value of money, methods of economic evaluation and the effects of the lifetime cycle are presented. The determination of analytical formulas to predict the PAT purchase price is shown. The installation of a PAT as a replacement of or complement to a pressure reducing valve is presented in order to assess the producible energy and minimize the plant economic payback time. The reader will be supplied with the theoretical basis of the economic parameters used to estimate the cost of a PAT, together with methods for economic evaluation and a definition of the best economic solution.

Information about the different components of a PAT and an overall description of civil engineering design are presented. The electromechanical transmission arrangements realized to avoid dissipative effects and to guarantee the best operating conditions are defined and additional aspects associated with installation procedures and operation and maintenance are described. A theoretical and project-based design for the comprehension of a micro-hydropower scheme connected with a PAT installation in water systems is presented. Different design components and the rules to be followed by engineering designers are defined.

The importance of pressure control in water transmission systems with the identification of flow energy dissipation points is presented. The numerical methods used to analyze the behavior of the hydraulic system, the control valve maneuvers, and the over-speed effect associated with the dynamic behavior of the PAT are discussed. The dynamic control of the pressure induced by the water demand which varies during the day in quasi-steady state conditions and the pressure surge control for unsteady regimes that can occur in PAT shutdown/start-up and valve control closure/opening, as well as in a sudden load rejection with the associated over-speed effect, are examined. An understanding of the system behavior in terms of pressure control and in the presence of different dynamic effects is provided, and, in addition, the different analyses that should be made for each PAT type and water system requirement are described.

Users, researchers and engineers require a fundamental knowledge of reverse pump theory. In this chapter first, a complete description of all PAT components is given. Then, the theory of small reverse pumps is described, based on the results of theoretical analyses, experiments and numerical simulations. PAT characteristic and efficiency curves are introduced and, the influence of pump size and rotational speed on such curves is considered. The possibility of using numerical simulations instead of experimental results is discussed. Finally, additional aspects like cavitation and the incidence of pressure surges are presented and different tools, commonly used for PAT sizing and hydropower plant design, are described. The reader will be prepared, by means of the theoretical basis provided, for the comprehension of the hydraulic and mechanical processes connected with a PAT operation.