A Methodology to Assess Optimal Operation of a Prototype for Pressure Regulation and Hydropower Generation

While pressure-reducing valves (PRVs) are commonly used to regulate pressure and reduce leakage in water distribution networks (WDNs), research in recent years has increasingly focused on coupling hydropower generation with pressure control, wherein the excess head is used for generating power instead of being dissipated through the PRVs. In this case, a programmable logic controller (PLC)-based control system is required to control valve operation (in case of hydraulic regulation) and impeller speed (in case of electric regulation). Because the optimal operation of the system requires solving an optimization problem with mathematical operations too complex for the PLC to handle, an external optimization module is required and coupled to an OPC server so as to allow communication between the optimization routine and the PLC. However, issues associated with implementing any external device in such a solution diminish system reliability. This paper therefore presents a robust alternative approach for advantageously solving the optimization problem directly within the PLC operating cycle, involving only simple yet effective mathematical and logical operations. The proposed methodology also allows identifying the range of flow discharges for which hydraulic and electric regulation can be used alone, thus not requiring coupled regulation. Besides using dimensionless variables representing the machine characteristic curves, and a flowchart showing the different operations at varying flow discharge and available head values, the capability of the proposed methodology was confirmed through numerical experiments, which in all cases returned the optimal solution to the problem. Moreover comparative analysis including an appropriate case study from the literature also decisively showed the results derived from the methodology to coincide with those obtained using an optimization tool.