Energy diagnosis of pressurized water systems with the ENERGOS tool

Abstract

Although the transport of fluids by pipeline is the most efficient, it requires high energy consumption, due to the volume transferred and the pressure required. This is the consequence of transporting large volumes of water (sometimes over considerable distances) and having to deliver it at the required pressure. In the current context of climate change, with both resources becoming increasingly scarce, the only way to minimize their impact and control energy consumption is to improve efficiency, a process whose most relevant stages are the diagnosis, which identifies the starting point and the existing margin for savings, and the audit, which locates and quantifies inefficiencies. This paper presents a simple tool, ENERGOS, which allows to perform the first stage, the energy diagnosis of a pressurized water system. The objective of this diagnosis is to know the current state of the system, and more importantly, the possible margin for improvement, if any, from the introduction of very few data. This is the first step to improve the efficiency of the system. The tool, and the energy indicators presented in it, have been designed under the premise that only the minimum information, which any manager should know about his system, is required. That is, global volumes billed and injected, the most representative system levels and energy consumed by the pumps (available in the electricity bills). ENERGOS classifies the systems into three large groups, and performs the diagnosis according to the group. These are, firstly, the simple systems, defined as a pipeline, with one entry, generally, one pump, and one exit. Multi-scenario systems are systems with several inputs and outputs, and constant changes in their mode of operation, where each of these scenarios corresponds to a different layout. Finally, networks with one or more inputs and numerous outputs can operate differently, but without changing the layout. In all cases, the tool has a schematic, simple and intuitive data entry part, and from the data entered, it calculates the diagnosis, consisting of the comparison of the current energy intensity indicator (kWh/m3) with the ideal energy intensity, the one that would imply the total absence of losses, both operational (friction, water losses, inefficiencies in the pumping stations) and structural (losses due to topography). Since it is impossible to reach the ideal energy intensity value, an intermediate indicator, the target intensity, is defined. The calculation of this intensity requires the establishment of targets for losses, reasonable reference values to be achieved with the current technology for the system under analysis. For example, the current efficiency of the pumping station is estimated, and a minimum acceptable level is calculated for it (establishing values for the efficiency of the motor, the variator and the pump itself). The same is established for friction, water losses and excess pressure.