A new approach to model development of water distribution networks with high leakage and burst rates

Modelling real distribution networks can be particularly difficult if they are so leaky that the types of leak and their nature can hardly be determined from scarce field measurements. In this context, a new approach to model development of such WDNs is proposed. The method is based on leakage estimation from MNF and the burst frequency of AZPs. After applying it to a real DMA in Mauritius, the resulting calibrated model from EPANET is found to approach the actual status of the network very closely in terms of overall real losses, coefficients of discharge, nodal flow and pressure

Laboratory Investigation of the Leakage Characteristics of Unburied HDPE Pipes

In this research work, the leakage characteristics of the viscoelastic material HDPE is investigated and compared to other materials like uPVC which is elastic and galvanised steel which is rigid in nature. Under no axial loading, the deformation in HDPE pipe wall causes the leak aperture to close up under increasing pressure head. As a consequence, the leakage exponent decreases from around 1 to 0.5 with increase in both longitudinal and circumferential crack lengths whereas for uPVC and steel, the leakage exponent increases under similar conditions. Consequently, the increase in discharge rate for increasing pressure in HDPE gets smaller

An Overview of Wave Energy Technologies in the Mauritian Context

Small Island developing states like Mauritius are very vulnerable to climate change as well as to fluctuating fossil fuels prices in the international market. Mauritius is targeting 35% mixed renewable energy generation by 2025. This work will focus on different types of wave energy converter (WEC) that can be used to supplement the existing local electrical energy grid. The key dimensions of a WEC are analyzed with respect to their ocean environment, namely, shore, nearshore and offshore and coupled to their working principles. Furthermore, the pros and cons of such devices are considered and much efforts have also been made to summarize the current status and future potentials of wave as an alternative renewable energy option for Mauritius

Quantifying the Pumping Energy Loss Associated with Different Types of Leak in a Piping System

In this paper, the impact of different types of leaks on the excess pumping energy required in a distribution pipe is investigated. It is now well established that leakage is directly proportional to the pressure at the leak point in a pipe such that a pressure drop is inevitable. In order to compensate this drop in pressure, the pumping energy required to supply demand at a constant pressure has to be increased. How much more energy is required depends on the type and extent of the leak. For the 3 types of simulated leaks namely: orifice, circumferential and longitudinal slits with the same area of discharge, it is found that the excess pumping energy required for a circumferential crack in the pipe is the highest, followed by the orifice and then longitudinal slit as a result of the discharge to sustain customer demand and pressure head. The results of this research can be used to design a more robust control system or pump rescheduling strategy in order to save energy and water with regard to design, operation, and rehabilitation of old water distribution system

Efficiency of VFD Coupled Induction Motors Operating in the Scalar Mode with Different Types of Loads

In this paper, we investigate the behaviour of scalar controlled AC Variable Frequency Drives for induction motors when coupled with different types of loads. It is well known that slip is more pronounced at high speeds rather than low speeds in loads such as in pumps and fans operation because the torque load varies as the square or cube of the speed. Slip compensation in Voltage/Frequency controlled Variable Frequency Drives may work only up to a certain limit since the problem can be exacerbated by overcompensation causing low magnetisation flux of the stator and the Variable Frequency Drive becomes uncontrollable. In this research work, we investigate the behaviour of the motor and Variable Frequency Drive assembly with regards to slowly changing loads from low to high speeds. Results show that at reduced speeds for the Variable Frequency Drive and motor assembly, the efficiency is lowest for square and cubic torques loads compared to linear and constant torque loads. Highest efficiency and torque are achieved only in a restricted interval of speed. This problem therefore compels us to avoid using the Variable Frequency Drives in the Voltage/Frequency mode at low speeds for pumps and fans