Safety criteria for the trafficability of inundated roads in urban floodings

The probability of unexpected urban flood hazards is steadily increasing due to global warming and climate change. Consequently, there is a growing need for safety criteria determining the trafficability of inundated roads to ensure a fast and safe evacuation of people in case of such events. In order to determine those criteria, experimental investigations on the stability of two scaled watertight vehicle models and of one prototype passenger car are conducted in a laboratory flume and a steel tank.The conducted flume experiments clearly show a dependency of vehicle stability on the flow angle, whereas the prototype experiments indicate that floating water depths are higher in prototype than in model scale, which is due to the use of a watertight vehicle model. Based on both experiments, a constant total head is proposed as decisive parameter for determining trafficability. This parameter approximates the measured stability curves and can be easily adopted in practice. Furthermore, it is in accordance with fording depths evaluated from relevant literature or by means of manufacturer inquiry. The recommended safety criteria for passenger cars and emergency vehicles are total heads of h(E) =0.3 m =const. and h(E)=0.6 m=const., respectively. (C) 2016 Elsevier Ltd. All rights reserved

Penetration depth of plunging liquid jets – A data driven modelling approach

© 2016 Elsevier Inc. In the case of impinging water jets or droplets, air entrainment processes are crucial to the casing design of hydraulic impulse turbines in the micro-hydro sector. To initiate first steps towards a precise prediction of the complex, multi-phase casing flow of impulse turbines, single aspects such as the penetration depth of impinging liquid jets have to be separated and fully understood. Existing investigations determining penetration depths are related to a very small range of flow rates and therefore show an underestimation of the penetration depth being applied to the casing flow of impulse turbines, which are generally operated at higher flow rates. For a more general description of the air entrainment process, investigations of plunging water jets within an extended flow rate range are conducted and the penetration depth is modelled using a data driven artificial neural network (ANN) approach and a non-linear regression model.At low flow rates, experiments results are in accordance with existing studies, whereas penetration depths up to 170 cm are measured at higher flow rates. For the mathematical models to achieve a wide range applicability, a large data base is used, including published and measured data. The modelled penetration depths can be precisely verified by the performed measurements and show correct physical behaviour, even in areas without underlying data. Calculation rules, weight matrices and biases of the trained ANN are published to achieve high transparency and scientific improvement in neural modelling of penetration depths of impinging liquid jets

Grid-scale pumped hydro energy storage for the low countries

Penetration of intermittent renewable energy sources into the power grid requires large-scale energy storage to ensure grid stability. Pumped Hydro Energy Storage (PHES) is among the most mature, environmentally friendly, and economical energy storage technologies, but has traditionally only been feasible at sites with large natural topographic gradients. ALPHEUS addresses this by developing reversible pump-turbines efficient at low heads, that operate between an enclosed inner basin (that functions as the upper or lower reservoir) and a shallow sea or lake

Minimising the air demand of micro-hydro impulse turbines in counter pressure operation

Following new and innovative concepts of energy recovery which use micro-hydro impulse turbines in drinking water systems, more sophisticated turbine designs become essential to improve energy recovery efficiency. In the case of implementing a hydraulic impulse turbine with tailwater depression in such systems, one major challenge to optimising overall efficiency is the reduction of the turbine's air demand. Firstly, a lower air demand would reduce the required dimensions of the ventilation system and therefore increase energy efficiency. Secondly, a minimised air demand would considerably reduce negative effects downstream of the turbine casing, such as a reduced transport capacity and corrosion. To achieve a minimised air demand, detailed experimental investigations are conducted, during which different casing inserts are tested in a micro-hydro Pelton machine. A specially constructed turbine test-bed, featuring two separately installed measuring units, allows for the partitioning and measurement of dissolved and undissolved air. In the case of the used Pelton machine, the results clearly identify different air detrainment processes. The undissolved air demand strongly depends on the particular casing insert and can be reduced by 90% through optimal flow condition using flow straighteners as insert. In contrast, the amount of dissolved air demand cannot be controlled by additional casing inserts. This can be explained due its different entrainment processes. The analysis of the dependency of the measurement results on scale shows that a direct transfer to a prototype application will underestimate the air demand. Nevertheless, the presented research findings show an effective way, also relevant to turbine manufacturers, to reduce air demand and improve overall efficiency of impulse turbines in counter pressure operation

Optimized design of impulse turbines in the micro-hydro sector concerning air detrainment processes

Impulse turbines with tailwater depression are an efficient choice for energy recovery in drinking water systems. To reduce negative effects of detrained air downstream of the turbine casing, such as corrosion and reduced transport capacity, main processes and possible reduction of air detrainment have been investigated in detailed experimental studies on a micro-hydro Pelton machine with tailwater depression. The experimental setup has been designed to distinguish between dissolved and undissolved air detrainment. In case of dissolved air detrainment there is a clear relation between the amount of dissolved air and the counter pressure as well as the flow rate parameter. Experimental results for the amount of undissolved air detrainment show dependencies on geometrical dimensions, velocity coefficient, casing water level and the flow rate of the turbine. To avoid undissolved air detrainment, design equations are deducted for dimensioning the casing height and the casing diameter. Therefore the presented investigations show how air detrainment can be controlled or rather minimized by optimised casing-design of impulse turbines

Grid-scale pumped hydro energy storage for the low countries

Penetration of intermittent renewable energy sources into the power grid requires large-scale energy storage to ensure grid stability. Pumped Hydro Energy Storage (PHES) is among the most mature, environmentally friendly, and economical energy storage technologies, but has traditionally only been feasible at sites with large natural topographic gradients. ALPHEUS addresses this by developing reversible pump-turbines efficient at low heads, that operate between an enclosed inner basin (that functions as the upper or lower reservoir) and a shallow sea or lake

The contribution of low‐head pumped hydro storage to grid stability in future power systems

The pan-European power grid is experiencing an increasing penetration of Variable Renewable Energy (VRE). The fluctuating and non-dispatchable nature of VRE hinders them in providing the Ancillary Service (AS) needed for the reliability and stability of the grid. Therefore, Energy Storage Systems (ESS) are needed along the VRE. Among the different ESS, a particularly viable and reliable option is Pumped Hydro Storage (PHS), given its cost-effective implementation and considerable lifespan, in comparison to other technologies. Traditional PHS plants with Francis turbines operate at a high head difference. However, not all regions have the necessary topology to make these plants cost-effective and efficient. Therefore, the ALPHEUS project will introduce low-head PHS for regions with a relatively flat topography. In this paper, a grid-forming controlled converter coupled with low-head PHS that can contribute to the grid stability is introduced, emphasising its ability to provide different AS, especially frequency control, through the provision of fast Frequency Containment Reserve (fFCR) as well as synthetic system inertia. This paper is an extended version of the paper “The Contribution of Low-head Pumped Hydro Storage to a successful Energy Transition”, which was presented at the 19th Wind Integration Workshop 2020

The contribution of low-head pumped hydro storage to grid stability in future power systems

The pan-European power grid is experiencing an increasing penetration of Variable Renewable Energy (VRE). The fluctuating and non-dispatchable nature of VRE hinders them in providing the Ancillary Service (AS) needed for the reliability and stability of the grid. Therefore, Energy Storage Systems (ESS) are needed along the VRE. Among the different ESS, a particularly viable and reliable option is Pumped Hydro Storage (PHS), given its cost-effective implementation and considerable lifespan, in comparison to other technologies. Traditional PHS plants with Francis turbines operate at a high head difference. However, not all regions have the necessary topology to make these plants cost-effective and efficient. Therefore, the ALPHEUS project will introduce low-head PHS for regions with a relatively flat topography. In this paper, a grid-forming controlled converter coupled with low-head PHS that can contribute to the grid stability is introduced, emphasising its ability to provide different AS, especially frequency control, through the provision of fast Frequency Containment Reserve (fFCR) as well as synthetic system inertia. This paper is an extended version of the paper “The Contribution of Low-head Pumped Hydro Storage to a successful Energy Transition”, which was presented at the 19th Wind Integration Workshop 2020.Offshore and Dredging EngineeringHydraulic Structures and Flood Ris