Delta21: Improved Design of the Turbine-Pumping Station

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Abstract

A changing climate means that the combination of storm surge and river flood waves is becoming increasingly likely. The turbinepumping station of the Delta21 concept, is designed just for that. The energy storage lake and the pumps capable of up to 10,000 m3/s mean that even the highest river discharges can be sluiced to the North Sea in the event of closure of the storm surge barrier. When the pumps are not being operated to combat flood waves, the pumpturbines can be used for the purpose of storage of intermittent renewable energies. The required capacity of the pumping station means that the total width of the structure is in the order of kilometers. Past studies into the conceptual design have shown that if the pumping station and flood barrier are integral then this results in a massive structure. AnsorenaRuiz (2020) showed that such a massive structure performs very poorly in a life cycle analysis. For this reason, the goal of the thesis research is to develop an improved design for the turbinepumping station in which the structure can be separated into two parts resulting in a less monolithic form. The design is separated into two main parts: the hydraulic design and the structural design. The hydraulic design ensures that the turbinepumping station can operate at the required functionality. A pump characteristic as well as a turbine characteristic was received from equipment manufacturer Pentair and was adjusted to the requirements of the Delta21 turbinepumping station. A simulation showed that the total efficiency of the turbinepumping system is around 67%. Using timeseries of storm surges and predicted flood waves with various return periods, a simulation was also done of the response of the energy storage lake and pumping station. It showed that for flood waves of very low annual exceedance probability the required capacity of the turbinepumping station should be larger than 10,000 m3/s, but however the storage function of the energy storage lake does contribute to the sluicing of the superfluous discharge. Various alternatives for the hydraulic design were conceived, and it was concluded that the draft tube shape of the intake is the optimal solution. For the structural design the elements of the turbinepumping installation were integrated into a sea dike. The dike acts as a flood defense, keeping the North Sea out of the energy storage lake, while the elements of the pumping station ensure control of the water level inside the lake. This separation of functions allows for a less imposing structure to be achieved, without compromising on the performance. In this study, sea level rise and energy transition go hand in hand. On the one hand, pumping technology is used to protect delta areas from flooding, while on the other hand the technology of hydropumped storage is used to increase the productivity of renewable energies to offset further climate change. On top of this, the gridbalancing capabilities of the system make it financially attractive for potential investors. Hydropumped storage is already an upcoming technology in mountainous areas, but its potential in deltas and coastal regions is even bigger.

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