## 6 Calculations
#### Selection of Hydroelectric Pump  
Part of the components in a PHES is a pump to transport water from a lower storage reservoir to a higher storage reservoir using excess available renewable energy. Using an available catalogue from a chosen manufacturer, a pump was selected to demonstrate the feasibility of the PHES system in an urban setting. The OSC series of Submersible Dewatering Pump by Jujico, Japan, was used and is shown in Figure 20. Some pumps of the OSC series are capable of pumping water above a head of 12 m and have volume capacity above 1655.5 cubic meters, with a steady flow rate of 0.103 cubic meters per second (m\({}^{3}\)/s). The selection process, capabilities, and features of submersible pumps are presented below [43]. With its compatibility tailored to the specified water head, the OSC Submersible Dewatering Pump proves ideal for applications requiring moderate water lifting. Its steady flow rate of 0.103 m\({}^{3}\)/s underscores its efficacy in handling continuous water transfer or dewatering processes seamlessly. Moreover, its submersible design ensures uninterrupted  
Figure 19: Kaplan turbine specifications. Figure 20: OSC Submersible Pump specifications. operation, particularly in scenarios necessitating full submersion in the fluid. This pump emerges as a reliable and effective solution for water management tasks, especially in dewatering operations where consistent water flow and moderate water head are pivotal considerations. The OSC Submersible Dewatering Pump methodology, shown in Figure 21, presents a highly efficient and versatile approach for eliminating excess water from construction sites, mines, and other waterlogged environments. Engineered to function fully submerged, the pump obviates the need for priming and operates efficiently at various depths [44; 45; 46]. Compprising a waterproof motor and impeller, the pump draws in water and expels it through a discharge pipe, ideal for situations requiring rapid and continuous water removal, such as construction excavations or underground mines. This methodology involves meticulous consideration of site-specific requirements, including water table depth and desired flow rate, offering pumps in various sizes and power capacities to meet diverse dewatering needs. Additionally, the submersible design safeguards the pump from external elements, minimizing the risk of damage and ensuring prolonged and dependable operation. Renowned for its ease of installation, low maintenance demands, and applicability across a wide range of industrial and construction contexts [47; 48; 49], the OSC Submersible Dewatering Pump methodology stands out as the preferred choice for efficiently managing water in diverse environments. Figure 21 presents a performance curve for a submersible slurry pump, likely the MASTRA TVA Series. This type of pump is designed to handle wastewater, sewage, and other liquids containing solids. The curve illustrates the relationship between the pump's capacity (flow rate) and total dynamic head (TDH) at different operating speeds. * Capacity (m\({}^{3}\)/h): This represents the volume of liquid the pump can deliver per hour. * Total Dynamic Head (m): This is the total pressure the pump can overcome, including static head (due to elevation) and friction head (due to pipe resistance). * Frequency (Hz): The electrical frequency (60 Hz in this case) affects the pump's operating speed. * Speed (rpm): The rotational speed of the pump, which is 3450 rpm in this case. The curves show that as the capacity increases (moving from left to right on the x-axis), the total dynamic head decreases. This is a typical characteristic of centrifugal pumps. The different curves represent the performance at different operating points, possibly due to variations in impeller size or design. * Efficiency: While not explicitly shown, the pump's efficiency would generally peak at a specific operating point. This is where the pump delivers the most output power relative to the input power.