Browsing by Author "Mama, Fatumah"

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    Optimal site selection and sizing of micro-turbines for energy recovery in Kapchorwa water network.
    (Busitema University, 2026) Mama, Fatumah
    Water distribution networks (WDNs) in steep highland regions dissipate significant recoverable hydraulic energy through pressure-management devices such as Break-Pressure Tanks (BPTs) and Pressure Reducing Valves (PRVs). This study investigated the optimal siting and sizing of Pumpas-Turbine (PAT) micro-turbines for energy recovery within the Kapchorwa water supply network, serving Kapchorwa Municipality in Eastern Uganda from five gravity-fed sources across three water supply sub-systems: the Teryet WSS (Teryet WTP, 2,658 m ASL), the Upper Tegeres WSS (Upper Tegeres Reservoir, 2,150 m ASL), and the Kapchorwa Town WSS (Kapchorwa Town Reservoir, 2,014 m ASL). A baseline hydraulic analysis was conducted using EPANET 2.2 on the calibrated network model comprising 197 junction nodes, 203 pipes, and 20 BPT valve locations, using the Hazen-Williams formula (C = 140) in Litres Per Second (LPS) units. A systematic four-stage screening process applied to all 20 BPT sites identified the Teryet WSS cascade as the optimal PAT installation program: BPT1 (N02-N03, 3.72 L/s, 92.6 m), BPT2 (N04-N05, 3.72 L/s, 89.8 m), BPT3 (N06-N07, 3.72 L/s, 91.3 m), BPT4 (N08-N09, 3.72 L/s, 91.2 m), and BPT5 (N10-N11, 0.54 L/s, 90.5 m). These five sites occupy the uppermost position in the gravity cascade, immediately downstream of the Teryet Water Treatment Plant, yielding the highest and most uniform available head of any candidate cluster in the network. The five sites were modelled in EPANET 2.2 as General Purpose Valves (GPVs) using PAT performance curves derived from the Perez-Sanchez et al. (2020) H-Q model and the Yang et al. (2012) efficiency model under a 24-hour Extended Period Simulation (EPS). The combined fivesite installation delivers 9.659 kW installed capacity and 71,916 kWh/yr annual energy generation. The EPANET EPS confirmed that all 197 demand nodes maintained the NWSC minimum service pressure of 15 m throughout all diurnal conditions, with the network's most pressure-constrained node (N36, Kapchorwa Town WSS, 17.2 m) unaffected by Teryet PAT operating status. The Todini resilience index improved from 0.71 (baseline) to 0.72 (with PATs). Supply demand satisfaction remained above 99.2% across all six failure scenarios tested, including simultaneous failure of all five PATs. Note that BPT5 generates only 0.336 kW, below the study's 3 kW minimum economic viability screening threshold; it is retained as an explicitly flagged sub-threshold exception for cascade completeness, contributing a small positive standalone NPV. Genetic Algorithm (GA) optimisation with a population of 200 individuals over 150 generations, validated against exhaustive enumeration of all 2^20 = 1,048,576 possible site subsets, confirmed the five-site Teryet cascade as the NPV-maximizing combination within the candidate set evaluated. Financial analysis at a 10% discount rate over a 20-year project life yielded a Net Present Value (NPV) of +UGX 299.9 million, a Benefit-Cost Ratio (BCR) of 2.58 across all sites, a Simple Payback Period (SPP) of 2.99 years, an Internal Rate of Return (IRR) of approximately 33.3%, and a Levelized Cost of Energy (LCOE) of approximately 310 UGX/kWh against the Uganda grid tariff of 800 UGX/kWh. Sensitivity analysis confirmed positive NPV under all tested tariff and discountrate scenarios, with a breakeven tariff of approximately 310 UGX/kWh, representing a 2.6x safety margin below the current prevailing tariff. This study demonstrates that the Teryet WSS cascade of the Kapchorwa water network can be transformed from an energy-dissipating system reliant on hydraulically wasteful BPTs into a renewable energy producer. The findings directly address a gap in international literature concerning high-head gravity systems in developing-country contexts, and contribute to Uganda's Sustainable Development Goal 6 (clean water and sanitation) and SDG 7 (affordable and clean energy) commitments. The study also identifies a higher-flow alternative candidate cluster (BPT7, BPT9, BPT11, BPT12, BPT14) with materially greater combined NPV potential, recommending this comparison for future phased expansion evaluation.