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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Construction of a long-term hourly electricity demand curve and peak load using MAED-EL for Lesotho
(National Manpower Development Secretariat, 2020) Kente
At the time that this study was undertaken, Lesotho Electrical Company (LEC) had no longterm hourly load curve forecast for electricity consumption. This makes it difficult for the utility to plan for future power plants and cost effective bilateral agreements as well as policy maker to make informed decision and for Independent Power Producers (IPPs) to be developed by investor. Therefore, this study aimed to construct a long-term hourly load curve for future electricity consumption in Lesotho starting with 2018 as the base year, followed by five-year long intervals from 2020 to 2040. The Model for Analysis of Energy Demand (MAED-EL) was used to calculate future hourly load curves for electricity and it uses the end-use approach when calculating the energy projections. Three scenarios were considered in this study to model possible trajectories of future electricity consumption, namely: Business-as-Usual (BAU), Low Economy Scenario (LE) and High Economy Scenario (HE). The annual growth rates of electricity consumption were estimated to be 4.3% for BAU, 2.4% for LE and 6.3% for HE. The projected peak demand for each scenario occurs during winter season (June to July). It was anticipated that the peak load will grow by 224% 123% and 54% for HE, BAU and LE scenarios from 2020 to 2040 while the energy consumption will increase by 223%, 122% and 53% for HE, BAU and LE from 2020 to 2040. The base load was predicted to grow from 58.77 MW,56.79 MW and 54.74 MW for HE,BAU and LE to 190.05 MW, 126.29 and 84.29 in for HE,BAU and LE respectevely in 2040 . Due to growth of electrical energy load the power deficit which was already high in 2018 at 94.44 MW would increase to 539.92 MW, 330.1 MW and 196.44 MW for HE, BAU and LE respectively in 2040. The Peak Load of the system was equal or above 75% of system peak load for 20% of the available time of the year.
Cascading wind and solar pumping systems to recirculate water for pumped hydropower storage system at Letsa-La-Letsie dam
(National University of Lesotho, 2024) Monyau, Marasi; Khaba, L; Makhele, M
This dissertation investigates the use of cascading wind and solar power pumping systems for recirculating water for pumped hydropower generation at Lets'a-la-Letsie in the Quthing district, Lesotho. The study's main goals are to identify optimal wind and solar resources for positioning wind turbines and solar panels; to design a solar/wind pumping system for recirculating water for pumped hydropower storage; and to design a hybrid system that considers the LCOE (least cost of energy) and system performance.
The digital elevation, solar energy and wind energy potential maps, in conjunction with QGIS, were used to analyse the heads of the study regions, and TURBNPRO was used to estimate the power outputs and specifications of the selected Pelton turbine. The net head for Lets'a-la-Letsie was 157 metres. The design flow rate for Lets'a-la-Letsie was 0.06 m3/s. To provide water to the top reservoir, 19 similar pumps are required. Each pump has a power control of 37 kW (kilowatts). The top reservoir volume was calculated to be 2700 m3.
This study uses the HOMER Pro simulation software to illustrate the performance of the Lets'a-LaLetsie hybrid renewable energy system. The system's total load includes the school load, clinic load, residential load, pumping load, and commercial load. The proposed hybrid system design consists of a 5379 kW solar PV array, a 1500 kW wind turbine, a 1985 kW converter, and a battery model for a pumped storage with a maximum capacity of 4331 Ampere hours (Ah). The optimal system has an LCOE of $0.417/kWh (Maluti 7.61/kWh) . The average solar irradiation and wind speed are determined to be 5.26 kWh/m2/day and 4.77 m/s, respectively. The project would require an initial capital commitment of about $27.9 million (509 million Maluti), with a total NPC (Net present Value) of $39.6 million (720 million Maluti).
The findings show that Lets'a-La-Letsie has enough sun resources as well as the topography for the construction of pumped hydropower storage facilities. However, the country lacks a legislative and commercial framework to support the development of pumped-storage power facilities.
Baselining Lesotho's disaggregated energy factors, ratios and intensities for household energy demand forecasting
(National University of Lesotho, 2024) Sekatle, Mosa Patricia; Thamae, Leboli Zak
Abstract
The approach that is traditionally employed for household energy demand forecasting in many countries, including Lesotho, has primarily focused on two levels of aggregation which are to disaggregate data into rural and urban settlements. This study introduces an approach which is tailored specifically for Lesotho’s unique context. It adopts a methodology that utilizes Lesotho’s four agro-ecological zones, providing four levels of disaggregation which are the Lowlands, Foothills, Mountains and the Senqu River Valley. Additionally, it incorporates Lesotho’s ten administrative districts which are Botha-Bothe, Leribe, Berea, Maseru, Mafeteng, Mohale’s Hoek, Quthing, Qacha’s Nek, Mokhotlong and Thaba-Tseka. They offer 10 levels of disaggregation in household energy demand consumption patterns.
The adopted approach allows a more comprehensive understanding of how the households energy consumption behavior varies across different zones and districts of the country. The approach provides valuable insights into zone or district specific energy needs and challenges; thus, it will enhance the accuracy of energy demand forecasting thereby informing more effective and targeted energy policies and interventions in Lesotho. The method used to baseline the disaggregated data is the exploratory data analysis (EDA) based on the Household Energy Consumption Survey (HECS) which was conducted in 2017. It uses both graphical and non-graphical techniques to uncover the data behavior, to spot anomalies and to check the trends through the visual and statistical summaries.
The findings of the study, using absolute values, indicate that during summer months, energy intensities per household in zones demonstrate high average intensity on fuel wood (168.4 kg/HH) and animal waste (148.7 kg/HH), and the low average intensity on LPG (6.8 kg/HH), paraffin (21.4 Ltr/HH), and electricity (69.8 kWh/HH). However, during winter months, fuel wood (165.5 kg/HH) and animal waste (147.0 kg/HH) have high intensities, while paraffin (30.8 Ltr/HH), aloe (39.2 kg/HH) and crop waste (62.9 kg/HH) have the lowest intensities. In the districts during summer months, animal waste (155.6 kg/HH) and fuel wood (144.1kg/HH) have the highest average intensities, while LPG (15.5 kg/HH) and paraffin (38.6 Ltr/HH) have the lowest. In winter months, animal waste (157.2 kg/HH) and fuel wood (152.1 Ltr/HH) show high intensities, while aloe (31.1 kg/HH) and LPG (44.1 kg/HH) take the lower energy intensities. Per capita energy consumption in zones during summer months shows shrubs (75.2 kg/cap) and fuel wood (50.2 kg/cap) with high intensities, while LPG (11.1 kg/cap) and paraffin (10.2 Ltr/cap) have the lowest. In winter months, animal waste and fuel wood have the most intensities of 45.6 kg/cap and 50.2 kg/cap respectively. In the districts, animal waste and fuel wood have high intensities of 44.8 kg/cap and 41.9 kg/cap, with the lowest in LPG (4.6 kg/cap) and paraffin (11.9 Ltr/cap) in summer, while in winter, fuel wood (46.9 kg/cap) has the highest and aloe (10.5 kg/cap) has the lowest intensity on average.
Lesotho’s energy consumption patterns in agro-ecological zones and administrative districts are mostly influenced by socio-economic and infrastructure gaps, which are apparent in the variation of energy consumption among districts and the reliance on traditional fuels is less urbanized areas. The Lowland zone and the Maseru district dominate most of the energy consumption statistics due to their large populations, better topography, proximity to infrastructure and stronger economic activities. The data delineates that while there is a growing shift towards modern energy sources, significant portion of the population still remain dependent on traditional fuels, particularly in remote areas.
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This approach provides critical information for policymakers, enabling them to develop more accurate energy demand forecasts and design targeted interventions. The study’s results can guide strategic energy planning to address Lesotho’s specific energy needs, promoting energy access and efficiency while transitioning towards cleaner energy sources. The insights gained from this research lay the foundation for future studies to build more sophisticated, localized energy models that better reflect the dynamics of Lesotho.
An optimization approach for the economic dispatch incorporating renewable energy resources into the LEC power sources portfolio
(National University of Lesotho, 2022) Rateele, Thato Nchakha; Thamae, Leboli Zak
Electricity demand in Lesotho has been constantly rising over the past years and has greatly surpassed the main domestic generation of 72 MW hydropower station in ‘Muela, which only supports a monthly average of 58% of the load and the deficit is imported from South Africa and Mozambique through fixed bilateral contracts. Although these contracts are regarded as uninterruptable as transmission paths are secured in advance, they come with heavy reliability premium costs endured by electricity utility, Lesotho Electricity Company (LEC). With the abundant renewable energy sources in Lesotho, Independent Power Producers (IPPs) could be invited to erect wind farms and solar photovoltaics (PV) plants to increase local energy security and diversify LEC power sources.
Because electrical power networks must be secure, reliable, and cost-effective, the study developed a power dispatching approach that includes solar PV and wind generators to aid 'Muela meet demand and be backed by imports. According to the analysis, main grid imports are minimized by 22.3% with the introduction of 50 MW Ha-Ramarothole solar PV and by 40.2% with wind farms (24 MW Masitise and 34 MW Lets'eng) working with 'Muela. A 59.7% minimization is obtained by combining solar PV at 50 MW, wind farms at 58 MW, and 'Muela at 72 MW. Furthermore, the study used the Monte Carlo approach to simulate generation adequacy analysis in order to establish the monthly average expected demand not supplied (EDNS) and loss of load probability (LOLP). The EDNS never drops below 0 MW, while the LOLP only reaches a minimum of 52% for all scenarios evaluated, according to generation adequacy analysis of all local generators.
Finally, the study assessed the influence of renewable energy absorption on LEC in terms of costs in procuring power locally and from imports using the South African Power Pool (SAPP) Markets: Day Ahead Market (DAM), Forward Physical Market (FPM) weekly and monthly. Since DAM yearly cost of energy is approximately half that of FPM weekly and monthly, it has been shown to be the most cost-effective market to procure under for renewables penetrations. Additionally, the cost of electricity anticipated to be incurred while purchasing from solar at 50 MW, ‘Muela, and DAM is around LSL 45 million less expensive than the fixed bilateral contracts. As a result, minimization of imports and their cost can be effectively accomplished with DAM because the total cost of energy (local prices plus DAM pricing) significantly reduces the potential expenses.
Analysis of the categories of the sustainability dimensions to achieve sustainable mini-grids
(National University of Lesotho, 2023) Maema, Tanki Alfred; Mpholo, M
Taking into consideration the rise of mini-grids globally, their important contribution in reaching the universal access to energy goal, and the uneconomic costs of national grid extension to certain areas, it is only befitting that mini-grids are studied extensively. This study intends to find the variables of a sustainable mini-grid and what makes a mini-grid sustainable, analysed and identifies the sustainability of the different models of mini-grids and finally finds which mini-grid business model is sustainable and is better suited Lesotho in order to raise the countries electricity access and better the populations livelihoods. The study assesses the categories of four (the community-owned, private, Public-Private Partnership (PPP), and utility business models) sustainability dimensions of mini-grids across selected countries with similar conditions to Lesotho. It shows that for a mini-grid to survive throughout its lifetime it has to adequately satisfy the economic, environmental, institutional, social, and technical sustainability dimensions.
The developer-consumer and the multi-tier frameworks developed by James Knuckle (2016) and the World Bank (2015) respectively were used in the assessment of the categories of sustainability dimensions for all four mini-grid business models. With the help of the frameworks, the study findings show that the PPP and private mini-grids proved to be the closest models to sustainability in all the assessed categories and dimensions failing in the cash recovery and affordability categories respectively. They are followed by community mini-grids which fall back on some categories ( cash recovery,tariff coverage of the operations and maintenance and tariff setting) for this reason are not sustainable. The PPP model has similar operations to utility mini-grids, as suggested by the frameworks, but has proven to be slightly better in a few categories. Utility minigrids are the furthest from sustainability of the studied mini-grids. They failed in the cash recovery category, failed to have tariffs covering their O&M cost, have low tariff settings and have limited power supplied to their customers.
From the already existing research on mini-grid models in Lesotho, suggestions are provided for Lesotho and its upcoming mini-grids. The study shows that a combination of private and community mini-grids is found to be the best uptake provided there are subsidies to help people afford the cost-reflective tariffs.