As a part of well field optimization the pump, as a key component in water extraction systems and its energy saving potentials have to be checked. In addition to the project deliverable D2.1 “Literature review on theoretical pump and motor efficiency of submersible pump systems” the availability of innovative and energy saving submersible pumps on the market has to be verified. Therefore, the market has been scanned and evaluated. The purpose of this document is to present the results of the market analysis for efficient pumps and to assess realistic energy saving potentials that are achievable with today’s technology. This achievement can be reached by either selecting more efficient centrifugal pumps or motors (evaluated in this study), or by considering some boundary conditions such as losses in power supply cables, operating mode or the use of variable speed drives. These accompanying conditions were also discussed at the workshop and are presented as a short summary in the last chapter of this paper.

This report concludes the first phase of the project “OptiWells”, which focuses on the optimization of drinking water well field operation with respect to energy efficiency. The purpose of this document is to provide sound answers to questions that utilities and well field operators are facing. Thus, it is built as a thematically organized sequence of main questions and answers rather than an extensive manuscript-like report. In total, 13 questions are addressed in detail, while 3 main “unanswered” questions and issues are detailed at the end of this report. The focus of this report is identical to the project’s focus: it addresses energy efficiency issues within the well field system. Thus, the main area of focus of the project lies in the interactions between the groundwater, the well, the pump and raw water pipe system. Drinking water treatment, as well as water distribution is not included in this study. This document, in combination with the other project deliverables, shall provide an overview of the potential optimizations for drinking water well fields. It shall yield both answers about saving potentials in general, and give some concrete examples from a French well field. By doing so, it shall assist the identification of solutions for an energyefficient groundwater abstraction, and provide a basis for a sound, practical methodology for well field energy audits and assessments.

This work was carried out within the framework of the project OPTIWELLS at the Kompetenzzentrum Wasser Berlin (KWB), a non-profit network society for water research and science transfer. The project addresses the modelling of a well field in order to minimise its energy demand. The first phase of the project is a feasibility study to identify the optimization possibilities of the energy demand. The first part of the study concerns the design and testing of a hydraulic model. At the beginning it was implemented on MS Excel and after with the help of Epanet, an opensource software. Data from the operator and manufacturers as well as measured data, gained during a site audit, were used to calibrate the model. Goals were to understand how the well field was working and to identify the energy demand drivers. The second part of the study concerned the choice and the implementation of scenarios with different operational conditions for the well field. Scenarios were focused on two aspects: the change of boundary conditions and the study of possible investments. A cost comparative assessment was carried out to estimate the payback times of the investigated scenarios. Results and according recommendations were communicated to the well field manager.

The optimisation of drinking water well field operation may significantly reduce the energy demand and associated costs, but is seldom applied in a systematic methodological approach. In this study, a well field was analysed using a coupled model that takes into account aquifer, wells, pumps and raw water pipes. This coupled approach enabled to identify and quantify the key energy demand drivers. The geometrical elevation was the most important driver, while pipe network losses were in the same order of magnitude as aquifer- and well losses. Using the modelling tool, the most energyefficient well field operation scheme could be derived and energy savings of up to 17% may be achieved by optimising well field operation only whereas further 5% may be saved by investing in new pump equipment. These findings show the potentials for significant energy savings in the field of drinking water abstraction.

There is a significant potential for optimizing pump systems currently in use in groundwater wells. This potential lies in: (i) the improvement in pump technology, which can yield up to ~5% more efficiency, (ii) the improvement in motor technology, which can yield up to ~3% more efficiency, with further improvements if innovations from aboveground motors are adapted, (iii) the improvement in performance adaptability, which can be very efficient in some cases (~10-50%), but also counterproductive if not adapted to current situation (0% or even efficiency loss), and sometimes not very flexible (impeller trimming); (iv) the improvement of the system maintenance and management which may yield up to ~20% more efficiency, and which, in general, has a shorter payback time than performance adaptability options.The improvement of equipments may induce only moderate additional costs if it is done at the time of scheduled new investments, after amortization of the equipment formerly in use. Unfortunately, these expected savings are influenced by uncertainties, which can be of the same order of magnitude as the savings themselves. For instance, the determination of the optimal operation point of a pump bears uncertainties between 1% and 4% and grows with pump rotation speed (Gülich 2010). Other considerable saving potentials lie within cleaning, maintenance and smart wellfield operation with short to moderate payback times (Table 6). These potentials are however very site-specific, and difficult to estimate on a general basis. Best practices for a “smart” pumping shall include choosing equipment that fits the actual requirements of the system, operating the pumps nearest of their Best Efficiency Point, and operating the motors in an energy-efficient load range. The most obvious energy savings are those associated with improvements in the efficiency of the motor and of the pump (Shiels 1998). Such gains are often worth the added capital expenditure – although often having moderate to long payback times. However, as underlined by (Kaya, Yagmur et al. 2008), that pumps have high efficiency alone is not enough for a pump system to work in maximum efficiency. An improvement of pump technology will yield, even optimistically seen, an efficiency improvement of up to 10%, which is the potential “theoretical limit” (EC 2003). For further improvements, it is necessary to consider solutions that go beyond the pump system, since maximizing efficiency depends not only on a good pump design, but also on a good system design. Even the most efficient pump in a system that has been wrongly designed is going to be inefficient. Moreover, an efficient pump in an inefficient well is pointless. Hence, a global approach of the groundwater abstraction system is required. The optimization potentials highly depend on the site characteristics themselves, on the local demand (what distribution of the demand? what load profile?), and on the operation and maintenance history (e.g., what is the cleaning frequency of the pipes, if any?). Finally, one should not forget the primary objective of water abstraction, which is satisfying a given water demand, thus, the safety of drinking water production prevails over energy efficiency.