NULIR
The National University of Lesotho Institutional Repository (NULIR) is a digital archive that collects, preserves, and provides open access to the scholarly and intellectual output of the University.
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Recent Submissions
Advancing Epistemic Diversity and Pluralism for Sustainable Development
(Academic Forum for Development of Lesotho, 2024-10-01) Mokuku and Chere-Masopha
Advancing epistemic diversity and pluralism for sustainable development
(National University of Lesotho, 2024) Mokuku, Tsepo; Chere-Masopha, Julia
Solar water purification system for rural areas
(National University of Lesotho, 2025) Makebe, Rethabile; Jonathan, Enock; Kao, Moruti
This dissertation examines the design, efficacy, and viability of a hybrid solar photovoltaic-thermal (PVT) and ultraviolet (UV) water purification system specifically developed for rural Lesotho, featuring a case study in the Mohale Basin. The system incorporates thermal energy capture by the solar PVT array to preheat feedwater before reverse osmosis (RO) treatment, hence improving membrane efficiency and minimizing fouling hazards. The electricity produced by the PVT array energizes UV disinfection devices and water pumps, while battery storage guarantees continuous operation under low solar irradiance circumstances.
Two optimized setups, that is, 5.2 kWp and 14.4 kWp were simulated by PVsyst, underpinned by mathematical modelling and validated against DuPont WAVE software. The 14.4 kWp configuration exhibits enhanced energy reliability with feedwater preheating to 40 °C, recovery rates of 60%, and specific energy consumption as low as 1.06 kWh/m³. Comparative evaluations solar PV and solar PVT RO demonstrate that the incorporation of PVT preheating with dual-stage RO markedly decreases operating pressures and enhances water quality. Analysis indicated that the smaller 5.2 kWp system, despite its reduced initial expenditure, yields water at a higher Levelized Cost of Water (LCOW) of USD 1.25/m³. The larger 14.4 kWp system on the other hand attained a lower LCOW of USD 0.75/m³, illustrating the benefits of economies of scale in hybrid PVT-RO configurations.
This work demonstrates the viability of scalable solar-driven water purification systems for offgrid rural Lesotho, with implications for sustainable development and climate adaptation, providing a viable approach to furthering Sustainable Development Goals 6 (Clean Water and Sanitation) and 7 (Affordable and Clean Energy) in Lesotho.
Development of time-of-use tariffs
(National University of Lesotho, 2020) Mohasoa, Lebohang Edwin; Mpholo, Moeketsi; Eager, Dan; Thamae, Retselisitsoe
The electricity consumption profile varies during any 24-hour period, but the electricity pricing policy for Lesotho Electricity Company (LEC) does not reflect this fluctuation as it employs flatrate tariffs across all customer categories. This fails to adequately capture the costs exerted on the electricity network by each customer at a certain period. To address this problem, time-of-use (ToU) tariffs are determined in this study, while ensuring revenue neutrality for the utility before any load shifting. Implementation of a comprehensive ToU based pricing model could be an effective mechanism to reflect the costs imposed on the network by customers and therefore encourage customers to engage in load adjustment. The Gaussian mixture model has been utilized to determine ToU time-periods and prices. The time-periods are divided into different periods; offpeak, standard, and peak periods. Different customer categories have different durations of time- periods. This is attributed to the observed load profiles of different customer categories. Furthermore, different customer categories have different prices per period resulting in different price ratios. Possible load-shifting scenarios of 5% and 10% have resulted in a reduction in customer energy bills of 2.6% and 5.2%, respectively. While, the LEC bulk energy savings translated to 13 GWh and 30 GWh for the two load-shifting scenarios, respectively.
Determination of cost-reflective feed-in tariff for grid connected solar PV systems in Lesotho
(National University of Lesotho, 2020) Kokome, Limpho; Hove, Tawanda
Lesotho needs a feed-in tariff policy that can help accelerate integration of renewable energy in its electricity grid. In this study a method to determine the feed-in tariff for grid connected solar Photovoltaic (PV) systems was developed. The necessity to set different tariffs for different locations in terms of the solar PV array yield 𝑌 , and different tariffs for different installed capacities were examined. Location specific tariffs were examined because given a particular solar module, the array yield 𝑌 could vary with location because of different ambient temperature and radiation, while size specific tariffs were examined because solar PV systems have different specific costs for different system sizes. In order to determine the cost reflective feed-in tariff, the Levelized Cost of Electricity (LCOE) was used as the objective function. With this approach the feed-in tariff was set as the price for selling electricity that is reasonably above the unit cost of production. A custom spreadsheet model was used to calculate the solar PV array yield 𝑌 over Lesotho. This array yield was used to divide Lesotho into two regions, low yield regions, and high yield regions. Representative systems were chosen and the feed-in tariff for different solar PV installed capacities in both regions were determined. The study found that the feed-in tariff varies with location and system size as follows;
System Category FiT ($/kWh)
Low Array Yield Region High Array Yield Region
30 kWp Roof Mount 0.1778 0.1616
500 kWp Roof Mount 0.1597 0.1451
30 kWp Ground Mount 0.1740 0.1581
500 kWp Groun Mount 0.1453 0.1321
10 000 kWp Ground Mount 0.1138 0.1034
The study recommends a feed-in tariff that is both location and size specific. The feed-in tariff depends on duration of the tariff with shorter periods resulting in higher feed-in tariff. A 20-year duration of the feed-in tariff is therefore recommended by this study. The method used in this study to determine the feed-in tariff included the impact of inflation in the analysis and therefore a fixed feed-in tariff (that is not indexed to inflation) is recommended. The energy regulator, and the ministry responsible for energy policy setting can make use of this study in setting out feed-in tariff policy.