Theses and Dissertations

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Open Access
A chemical process design for green hydrogen production through water electrolysis in Lesotho
(National University of Lesotho, 2024) Ramaisa, Tsepiso Angelina; Thamae, Timothy
This research addresses the pressing need for process design models that are specifically adapted to Lesotho's distinct resource profile, particularly its vast hydroelectric capacity. At present, there is a noticeable gap in process models designed for green hydrogen production that take into account the unique energy conditions of Lesotho. To address this shortcoming, the study presents a detailed chemical process design for hydrogen production through water electrolysis, utilizing Lesotho’s renewable energy. The process model developed includes detailed mass balances to ensure precise quantification of material flows. Critical process parameters, including molar and mass fractions as well as stream molar flow rates, are defined to accurately describe the system, providing a solution that is specifically optimized for Lesotho's energy resources. The key unit operations, including separators, mixers and an electrolyser, are carefully modelled. Separators are used for phase separation and component purification, while mixers are designed to efficiently combine process streams. The electrolyser, central to the process, is modelled according to the electrochemical reactions which take place and mass transfer considerations. To ensure accurate phase equilibrium calculations, the Rachford-Rice equations are applied. Additional equations are formulated to characterise equipment performance and to address system constraints, such as product purity requirements. The developed model serves as a tool for enhancing hydrogen production and assessing overall process efficiency. It offers a framework for examining how different operating conditions and design parameters affect system performance. Future research should focus on incorporating renewable energy sources like wind and solar to diversify and enhance the sustainability of hydrogen production in Lesotho. Performing comprehensive energy balances will offer deeper insights into the system's efficiency and potential for optimization. Moreover, including economic and environmental assessments will provide a more thorough evaluation of the commercial feasibility of green hydrogen production in the country. These suggestions not only address current gaps but also lay the groundwork for developing a more integrated and scalable model for green hydrogen production, which could be applied to other regions with similar renewable energy resources, supporting both regional and global efforts towards sustainable energy transitions.
Open Access
Adaptive, robust, and fault-tolerant control strategies for grid-connected renewable energy systems
(National University of Lesotho, 2024) Nkhabu, Tsitso; Makhele, Molefe; Mokeke, Sebota
Lesotho is currently facing a power generation-demand imbalance. The 2023/24 annual report by the Lesotho Electricity and Water Authority highlights a peak demand of 222.12 MW, which is nearly three times the country’s installed generation capacity of 74.7 MW. Consequently, the nation relies on costly power imports from Mozambique and South Africa to cover the shortfall. To address this issue, Lesotho plans to integrate renewable energy sources, specifically wind and solar, into its national grid. However, integrating these low-inertia and intermittent renewable power sources introduces grid stability challenges, as they are vulnerable to disturbances like load changes or grid faults. This research focused on designing control strategies capable of not only adjusting system voltage to accommodate uncertainties from power system dynamics, internal changes, and external disturbances but also stabilizing the system under small disturbances. The analysis was conducted on a grid-connected 38 MW wind power plant, using five control strategies: Constant Voltage (Const. V), Constant Reactive Power (Const. Q), Constant Power Factor (Const. cosɸ), Voltage Droop based on Reactive Power (voltage Q-droop), and voltage droop based on reactive power in the q-axis (voltage Iq-droop). These strategies were evaluated for their adaptability, robustness, and fault tolerance under two operational scenarios: variations in wind speed and fluctuations in the Point of Connection (POC) bus voltage. With a three-phase short circuit created and cleared on the high voltage (HV) bus bar, all control strategies are within a 5 % voltage deviation upon service restoration and fault clearance within a period of 0.015 seconds. A Supervisory Control and Data Acquisition (SCADA) system was designed for the monitoring and control of the wind power plant. Determined from the closeness of the HV bus voltage to the POC voltage, the most adaptive control strategy is used for each operation scenario, taking into account the wind speed as well as the POC voltage. It was observed that the evaluation by the SCADA system is consistent with the result obtained from the DIgSILENT PowerFactory software. For further exploration, research is recommended for the implementation of Artificial Neural Networks (ANNs) in machine learning to accommodate any wind speed and POC voltage levels for the control strategies under investigation.
Open Access
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.
Open Access
Analysis of Quthing River and Letseng-laLetsie for Hydropower Potential
(National University of Lesotho, 2020) Lekhanya, Liteboho; Dr Khaba, L.; Dr Makhele, M.
This dissertation presents the analysis of Quthing River and Letseng-la-Letsie for hydropower potential in Quthing district in Lesotho. Electrical power deficit in the country is more prominent in rural areas like Quthing District. This calls for assessment of electrical sources in the vicinity of rural area load centers to inform policies for electrical production so as to curb power deficit problem. Mountain Rivers like Quthing River with steep slopes or gradients naturally provide good head which needs to be assessed along with its flow rates. Furthermore elevated dams like Letseng-la-Letsie can also provide a natural good head which needs to be assessed alongside with its discharge rates. The assessment was carried out by employing catchment area method to asses flow rates since the abstraction points of the study areas were ungaged and lacks data. The maps in association with QGIS were used to evaluate heads of the study areas and lastly TURBNPRO was used to determine power outputs from the study areas. The resultant net head for Quthing River was found to be 164.15 m while the net head for Letsengla-Letsie was 159.23 m. The design flow rate of Quthing River was found to be 0.58 m3/s while that of Letseng-la-Letsie was 0.1 16 m3/s. The results from TURBNPRO showed that the power output for Quthing River turbine was 815 kW while the power output for Letseng-la-Letsie turbine was 221 kW. Using typical hydro-electric generators efficiency of 99% and typical capacity factor for Africa of 0.49, the capacity from Quthing River was found to be 807 kW with annual energy of 3.46 MWh. The capacity for Letseng-la-Letsie was found to be 0.22 MW with annual energy of 0.95 MWh.
Open Access
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.
Open Access
Analysis of the viability of using solar thermal energy for Maluti Mountain Brewery
(National University of Lesotho, 2021) Lillane, Malillane; Hove, Tawanda; Mpholo, M
It has been established by literature that there is worldly movement towards renewable energy usage because of global warming. Solar energy among many is one form of renewable energy that can be used to reduce conventional energy usage. This study realized an opportunity to reduce the conventional energy (coal) use at Maluti Mountain Brewery (MMB); a brewery in Lesotho by preheating the boiler make up water. The boiler at MMB is serviced by condensate (70°C) and the cold water from the tap. The cold makeup water mixes with the condensate prior to the being carried into the boiler and thus reducing the efficiency of the boiler. This is because the boiler in turn demands a lot of coal to heat up the boiler feed water. A retrofitted solar thermal system into the existing system at MMB was done. This system was aimed at preheating the cold make up water before it mixes with the hot condensate in order to avoid the makeup water from reducing the condensate temperature. An Excel based model was made in order to design a solar thermal system that is cost effective and technically viable. The designed system is an active solar thermal system composed of evacuated tube collector with the EPD of 18 kWh/$), collector area of 80 m2 which was decided upon by the required maximum storage tank temperature of 100 °C. The storage tank size of the system was found to be 2110 Liters. A tank of such size could not be found on the market; therefore, a 2500 Liters storage tank would be ideal for the purpose. The actual collector area decided upon according to the collector aperture area of 2.998 was found to be 81 m2. The system was found to be able to preheat 54% of the makeup water (12 % of the boiler feed water is the makeup water). The amount of coal used by MMB would be reduced by 11% and therefore saving the company as the NPVSS is positive, amounting to $25044 for over 20 years.
Open Access
Analysis of the viability of using thermal energy for Maluti Mountain Brewery
(National University of Lesotho, 2021-04) Lillane, Malillane; Mr. Hove, Tawanda; Dr. Mpholo, Moeketsi
It has been established by literature that there is worldly movement towards renewable energy usage because of global warming. Solar energy among many is one form of renewable energy that can be used to reduce conventional energy usage. This study realized an opportunity to reduce the conventional energy (coal) use at Maluti Mountain Brewery (MMB); a brewery in Lesotho by preheating the boiler make up water. The boiler at MMB is serviced by condensate (70°C) and the cold water from the tap. The cold makeup water mixes with the condensate prior to the being carried into the boiler and thus reducing the efficiency of the boiler. This is because the boiler in turn demands a lot of coal to heat up the boiler feed water. A retrofitted solar thermal system into the existing system at MMB was done. This system was aimed at preheating the cold make up water before it mixes with the hot condensate in order to avoid the makeup water from reducing the condensate temperature. An Excel based model was made in order to design a solar thermal system that is cost effective and technically viable. The designed system is an active solar thermal system composed of evacuated tube collector with the EPD of 18 kWh/$), collector area of 80 m2 which was decided upon by the required maximum storage tank temperature of 100 °C. The storage tank size of the system was found to be 2110 Liters. A tank of such size could not be found on the market; therefore, a 2500 Liters storage tank would be ideal for the purpose. The actual collector area decided upon according to the collector aperture area of 2.998 was found to be 81 m2. The system was found to be able to preheat 54% of the makeup water (12 % of the boiler feed water is the makeup water). The amount of coal used by MMB would be reduced by 11% and therefore saving the company as the NPVSS is positive, amounting to $25044 for over 20 years.
Open Access
Analytical solutions to the arithmetic asian options pricing model using lie symmetry methods
(National University of Lesotho, 2025-07) Kubeletsane, Monts’uoe Edward; Nchejane, Ngaka John
This dissertation explores the use of Lie symmetry methods to find analytical solutions for arithmetic Asian options; path-dependent financial derivatives widely used for risk management in commodity markets. The pricing problem is formulated as a partial differential equation (PDE) involving the asset price, time, and the running average of the asset price. Lie symmetry analysis is applied to the PDE to compute its infinitesimal generators, determine an optimal system of one-dimensional sub-algebras, and perform symmetry reductions. Each reduced PDE obtained through this process also admits further symmetries, allowing for successive reductions and the construction of exact invariant solutions. Techniques such as Riccati reductions and the Frobenius method are employed to solve the resulting ordinary differential equations (ODEs). The study further examines the influence of key financial parameters (volatility, interest rate, and time to maturity) on the structure and behavior of the pricing solutions. The findings contribute to the theoretical understanding of Asian option pricing and provide analytical benchmarks for validating numerical approaches.
Open Access
Application of lie symmetrics to solving fractional black-scholes option pricing model in financial mathematics
(National University of Lesotho, 2022-10-21) Ramoeletsi, Realeboha; Kaibe, Bosiu, Ngaka Nchejane
We perform Lie symmetry analysis to the fractional Black-Scholes option pricing model whose price evolution is described in terms of a partial di erential equation (PDE). As a result, new complete Lie symmetry group and in nitesimal generators of the one-dimensional fractional Black-Scholes pricing model are derived. Furthermore, we compute a family of exact invariant solutions that constitute the pricing models for the Black-Scholes model using the associated in nitesimal generators and the corresponding similarity reduction equations. Using known solutions, more solutions are generated via group point transformations
Open Access
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. 1 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.
Open Access
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.
Open Access
Determinants of choice of household energy use in Lesotho
(National University of Lesotho, 2020) Mothala, Matsoso; Mpholo, Moeketsi; Thamae, Retselisitsoe
With the need to achieve Sustainable Development Goals, modern clean household energy choice forms the basis for heeding this call. In developing countries, most of the population lives in rural areas and is characterized by high dependence on polluting biomass for cooking and heating while they rely predominantly on paraffin and candles for lighting. Women and children in developing countries spend an appreciable amount of time collecting the biomass, hence unable to carry out other development activities. The use of modern technologies such as solar home systems for lighting could help pupils study at night with adequate light and with no adverse effects on their health. Nevertheless, the determinants of household energy choice have not been studied in many developing countries including Lesotho, despite the potential benefits of such a study. This study uses the data collected by Lesotho’s Bureau of Statistics through a national household energy consumption survey of 2017, to develop a multinomial logistic regression to identify and analyze the determinants of the choice of household energy use. The results indicate that income, as predicted by the energy ladder model is statistically significant for the choice of clean energy fuels. But other socio-economic factors such as gender, education, household size, and settlement type also play an important role in the choice of clean energy choice. The role of gender in the choice of fuels used within a household is generally statistically insignificant. There is not a clear distinction of preference, on the choice of fuel, between male-headed households versus female-headed households. An increase in the education level of the household head is statistically significant in choosing cleaner fuels. This suggests that public policies should have a strong focus on improving formal and informal education to increase awareness of clean energy fuels and their benefits. Household size is negative and statistically significant for the choice of clean fuels over traditional fuels. Large households have enough labour that is required for the collection of traditional fuels. In rural settlements, electricity is hardly used for either cooking or water heating, it is used only for lighting. This suggests that policies, for economic reasons, should not focus on extending the grid to the rural areas but to promote domestic systems and micro-grids that provide enough electricity for lighting and household entertainment.
Open Access
Determination of Cost-Reflective Feed-in Tariff for Grid Connected Solar PV Systems in Lesotho
(National University of Lesotho, 2020-05) Kokome, Limpho
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 theministry responsible for energy policy setting can make use of this study in setting out feed-in tariff policy.
Open Access
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.
Open Access
Determining cost-effective integrated renewable energy resource plan for Lesotho (2022-2040)
(National University of Lesotho, 2022) Nzemane, Tsoarelo Nelson; Taele, BM; Thamae, Leboli Z; Butare, Albert
The renewable energy potential for Lesotho has been sufficiently studied with only a limitation of which specific places could such energy be derived. The country does not have an integrated renewable energy plan (IRP) to help direct its efforts to address the problem of energy insecurity, low energy supply and over 50 percent dependence on electricity imports from South Africa and Mozambique. Most of the resources have been spent haphazardly and unprofitably in a bid to address access to energy problem. The objective of this study is to create an IRP that responds to cost effectiveness in Lesotho for 2022 to 2040 and to identify suitable places for renewable energy generation using Geographic Information System (QGIS) capabilities in order to increase the baseload capacity for Lesotho. These objectives were achieved by evaluating the existing renewable energy resources, especially solar and wind by determining suitable places for power generation to meet the ever-growing demand. This was achieved by first establishing the aggregated forecast electricity demand using the existing studies and this forecast formed the basis for envisaged future power demand for Lesotho. For example, the electricity demand is projected to reach 350MW in 2040. Secondly, proximity analysis results of the resource base to the grid, primary road infrastructure and substations at 3.5km and 15km buffer zones were done to determine suitable areas for renewable energy generation. The identified places were examined and the amount of energy that could be generated from them was estimated and evaluated. The findings showed that a total of 310MW added into the main grid cumulatively from both wind and solar resources from 2022 to 2040 would result in electricity supply independence for the country. The cheapest option in a generation was given first priority in terms of when to enter into the generation stream to meet the existing demand during scheduling in the determination of the optimum IRP. The study recommends a progressive reduction of imports since they can serve as safety buffers of the electricity network in the event hydropower is not sufficiently developed. The energy policy, renewable energy policy and other energy supply and demand instruments will be profited by this study.
Open Access
The development of highly selective modified glassy carbon electrode on acted carbon-iron oxide/graphene foam for electrocatalytic oxidation of uric acid and dopamine
(National University of Lesotho, 2023) Mpakanyane, Teboho
This research study explores the application of nanomaterial-modified glassy carbon electrodes (GCE) for the voltammetric determination of dopamine and uric acid. The GCE was fabricated with iron oxide, activated carbon, and graphene foam. Energy Dispersive X-ray Spectroscopy (EDS), Fourier Transform Infrared spectroscopy (FT-IR), X-ray diffraction Spectroscopy (XRD), and Scanning Electron Microscopy (SEM) were used to examine the microporous activated carbon, iron oxide spherical structure (Fe3O4) particles that were attached to the graphene foam sheets. A drop-dry method was used for electrode modification. AC-Fe3O4/GF/GCE was electrochemically interrogated in the ferrocyanide redox probe using cyclic voltammetry. The current intensity and the reversibility of the redox probe were enhanced in the presence of the electrochemical sensor. Differential pulse voltammetry technique (DPV) was employed for individual determination of uric acid under the optimized experimental conditions; pH 6, scan rate 50 mV s -1 , pulse width 0.05 s, pulse amplitude 0.05 V, and supporting electrolyte 0.1 M phosphate buffer solution. A detection limit of 2.55 µM was obtained with an analytical linear range of 5 - 1630 µM. All selected foreign species showed no significant interference with the electrochemical determination of uric acid. Furthermore, dopamine analysis was carried out on AC-Fe3O4/GF/GCE using DPV. The electrochemical sensing was also optimized at various analytical conditions and a detection limit of 1.47 µM was obtained in the linear dynamic range of 2.5 to 450 µM. Glucose, glutamic acid, l lysine, and ascorbic acid are a few of the interfering species that exhibited almost no impact on dopamine detection. In addition, the simultaneous determination of uric acid and dopamine was conducted successfully. They have been determined by differential pulse voltammetry, and the modified electrode exhibited a linearity relationship over a wide range of uric acid concentrations from 2.5 to 450 μM, with a detection limit of 1.75 μM, (s/n = 3). A linear trend for the current response for dopamine concentrations ranging from 5 to 400 μM, with a detection limit of 2.7 μM, has also been obtained. The results, therefore, demonstrated the sensor’s superior electrocatalytic activity and its high selectivity for dopamine and uric acid even when some foreign species were present. The average V recoveries from the real sample analyses of the urine samples showed that the proposed sensor could be put to use in the real sample analysis. The developed electrode was generally found to be highly selective and sensitive toward uric acid and dopamine. It has achieved better sensing performances with a very low detection limit, wider linear ranges, and short analysis times as compared to most previously reported modified electrodes for the same analytes. Furthermore, the developed electrode was validated successfully for real sample analysis in biological fluids. The proposed methods have many attractive features, such as low cost, simplistic electrode preparation procedure, easy renewability, long-term usability, and rapid analysis. The developed electrode also displayed good repeatability and selectivity towards interfering substances. It is a promising modified electrode for the electrochemical detection of other electroactive important compounds in biological systems.
Open Access
The development of highly selective modifies glassy carbon electrode on activated carbon-iron oxide/graphene foam for electrocatalytic oxidation of uric acid and dopamine
(National University of Lesotho, 2023) Mpakanyane, Liteboho
This research study explores the application of nanomaterial-modified glassy carbon electrodes (GCE) for the voltammetric determination of dopamine and uric acid. The GCE was fabricated with iron oxide, activated carbon, and graphene foam. Energy Dispersive X-ray Spectroscopy (EDS), Fourier Transform Infrared spectroscopy (FT-IR), X-ray diffraction Spectroscopy (XRD), and Scanning Electron Microscopy (SEM) were used to examine the microporous activated carbon, iron oxide spherical structure (Fe3O4) particles that were attached to the graphene foam sheets. A drop-dry method was used for electrode modification. AC-Fe3O4/GF/GCE was electrochemically interrogated in the ferrocyanide redox probe using cyclic voltammetry. The current intensity and the reversibility of the redox probe were enhanced in the presence of the electrochemical sensor. Differential pulse voltammetry technique (DPV) was employed for individual determination of uric acid under the optimized experimental conditions; pH 6, scan rate 50 mV s-1, pulse width 0.05 s, pulse amplitude 0.05 V, and supporting electrolyte 0.1 M phosphate buffer solution. A detection limit of 2.55 µM was obtained with an analytical linear range of 5 - 1630 µM. All selected foreign species showed no significant interference with the electrochemical determination of uric acid. Furthermore, dopamine analysis was carried out on AC-Fe3O4/GF/GCE using DPV. The electrochemical sensing was also optimized at various analytical conditions and a detection limit of 1.47 µM was obtained in the linear dynamic range of 2.5 to 450 µM. Glucose, glutamic acid, l-lysine, and ascorbic acid are a few of the interfering species that exhibited almost no impact on dopamine detection. In addition, the simultaneous determination of uric acid and dopamine was conducted successfully. They have been determined by differential pulse voltammetry, and the modified electrode exhibited a linearity relationship over a wide range of uric acid concentrations from 2.5 to 450 μM, with a detection limit of 1.75 μM, (s/n = 3). A linear trend for the current response for dopamine concentrations ranging from 5 to 400 μM, with a detection limit of 2.7 μM, has also been obtained. The results, therefore, demonstrated the sensor’s superior electrocatalytic activity and its high selectivity for dopamine and uric acid even when some foreign species were present. The average recoveries from the real sample analyses of the urine samples showed that the proposed sensor could be put to use in the real sample analysis. The developed electrode was generally found to be highly selective and sensitive toward uric acid and dopamine. It has achieved better sensing performances with a very low detection limit, wider linear ranges, and short analysis times as compared to most previously reported modified electrodes for the same analytes. Furthermore, the developed electrode was validated successfully for real sample analysis in biological fluids. The proposed methods have many attractive features, such as low cost, simplistic electrode preparation procedure, easy renewability, long-term usability, and rapid analysis. The developed electrode also displayed good repeatability and selectivity towards interfering substances. It is a promising modified electrode for the electrochemical detection of other electroactive important compounds in biological systems.
Open Access
Development of solar radiation database and its integration into solar process applications in Lesotho
(National University of Lesotho, 2020) Bulane, Lebohang; Hove, Tawanda
Solar energy is a viable alternative source of energy for socio-development of a developing country like Lesotho. Investment in solar process applications, requires a accurate solar radiation data for the successful implementation of solar process projects. However, in Lesotho measured solar radiation datasets are not sufficient both temporally and spatially as there are only seven solar radiation measuring sites, two of which are not reliably operational. This study solves the problem of the scarcity of solar radiation data in Lesotho, by developing a solar radiation database for the country. It has a primary objective of developing an accurate solar radiation database for Lesotho. This is achieved by merging ground measured solar radiation data with satellite – derived solar radiation data. The merged data is complimented by solar radiation data derived from sunshine duration data. Merging solar radiation datasets is important because ground measured data are sparsely distributed and cannot be interpolated accurately to represent solar radiation at any location. Although satellite – derived datasets are spatially continuous, they are not accurate as they are inferred from extra- terrestrial solar radiation modified with atmospheric models. As a result, each of the databases cannot be relied up unilaterally. Measured ground data is from five stations and sunshine duration derived solar radiation is form twelve stations. The improved database is validated using a leave one out cross validation technique. Its reliability in estimating ground solar radiation is tested by relative bias error (rBE), relative mean bias error (rMBE) and normalized root mean square error (NRMSE). Results show that the database is credible as it has a maximum error of 2.67 % which is comparable to other studies of similar nature in Africa. An interpolation tool, increases the accuracy and reliability of interpolated solar radiation as compared to manual reading of data from solar radiation maps. It has an accuracy of 99.54%. The improved database and interpolation tool can confidently be used in any solar application process design and sizing in the country.
Open Access
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.
Open Access
Development of time-of-use-tariffs
(National University of Lesotho, 2020-07) Mohasoa, Lebohang Edwin; Mpholo, Moeketsi, Dan, Retselisitsoe Eager, Thamae
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 flat-rate 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; off-peak, 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. Key words: