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.
Recent Submissions
Wind measurements using SODAR: Hirundo wind farms case study
(National University of Lesotho, 2024) Rakuoane, Molibeli; Mpholo, Moeketsi
This study compares the wind data of the European Centre for Medium-Range Weather
Forecasts Reanalysis Version 5 (ERA 5) to that obtained from the sound detection and ranging
(SODAR) at the Rothe Plateau. It utilizes industry-standard software, Wind Atlas Analysis and Application Program (WAsP), to undertake the analysis. WAsP was employed to generate wind resource maps, to model the wind flow over complex topography and to forecast the yearly wind conditions. The availability of SODAR data, obtained from 23 January 2024, to 31 July 2024, after eliminating inaccurate and suspicious data, was 57.36%. It is commonly perceived as being of inferior quality due to its failure to meet the 90% threshold. The precision of wind resource validation is determined by the degree of accuracy and availability of the relevant data.
The findings of this study show that the forecast errors of ERA 5 represent about 12.2% of the range of SODAR wind speed data, indicating a moderate level of accuracy. The normalized root mean square error (NRMSE) for wind speed and direction were found to be 0.122 and 0.359, respectively. The ERA 5 provided inaccurate wind direction. Furthermore, the mean bias error (MBE) of -1.51 m/s and -7.840, respectively, for wind speed and direction were discovered, indicating an under prediction by the ERA 5 model. The correlation coefficient (R) between the two datasets was determined to be 0.725 (72.5%). Demonstrating a robust and reliable connection between SODAR and ERA 5. However, the wind direction correlation indicated a relatively poor connection of 27.7%. With a determination coefficient (R2) of 0.525, ERA 5 is not able to capture and represent the complexity and dynamics influencing fluctuations in wind speed variations.
The chosen turbine generator for the Hirundo Energy wind farm is the Vestas V162-6.0 MW, with a maximum rated power of 6.0 MW. The wind farm contributes significantly to the generation of renewable energy, with an anticipated net annual production of 75.5 GWh, about
8.9% compared to the country’s consumption of 848 GWh per annum in 2022. This proves that wind energy technology can be effectively harnessed in Lesotho and highlights the significance of data validation and farm planning for optimizing energy output and efficiency. However, due to the lack of continuous onsite measurements, the capacity factor was found to be 17.95%, compared to a global average of 30% for grid-connected wind farms.
Tracking SDG 7 progress for Lesotho using energy indicators for sustainable development
(National University of Lesotho, 2021) Kolobe, Mamontsi; Thamae, Leboli Zak
Energy is regarded as a global variable in achieving sustainable development goals (SDGs). In Lesotho however, there are no traces of how far Lesotho’s progress is regarding affordable and clean energy access status towards achieving the set SDG7 targets. There has never been any initiatives engaged for tracking the progress ever since the SDG7 targets were set globally. It is essential to know the country’s current energy status, economic stability, what needs to be improved and at what pace should the improvement be done. This study therefore traces progress of Lesotho energy sector on the four targets of SDG7: energy access (electricity and technologies for clean cooking), renewable energy and energy efficiency. The study further monitors the overall progress of the energy system towards sustainable development and indicates progress with the latest available data up to 2019 against a baseline year of 2014. The five-year data from 2014 to 2019 is going to be projected from 2020 until 2030 to examine the possible progress that would be achieved through two scenarios; Business as Usual (BAU) and Sustainable Development (SD) scenario. It is with SD scenario that certain policies will be informed which will help accelerate the progress. The results from this study suggest that only 68.4% of population will have electricity access by 2030 under BAU scenario. This verifies the SDG gap of 31.6% to meet 100% access target. Moreover only 50% of population will have clean cooking access by 2030 leaving a gap of another 50% to have 100% access. On the other hand, by 2030 renewable energy share will only be 45.5% and still lacking 18.5% to double the renewable energy share of 2014 to 64%. Results further show that in 2030, the energy efficiency improvement will only be 14.3 MJ and still lacking 5.3 MJ to double the improvement to 19.6 MJ. In essence, all four SDG7 targets are not going to be achieved by 2030; hence more powerful policies are needed to make these targets a success.
Tracing energy democracy in decentralized mini-grid projects in Lesotho
(National University of Lesotho, 2024) Tsotleho, Paki; Tsoeu-Ntokoane, Seroala
As the Lesotho electricity generation landscape transitions from centralized modes of systems towards decentralized generation and distribution systems, there exists a potential challenge of elite capture in governance structures and frameworks that may overlook the social dimensions that guarantee the sustainability of such systems. This study interrogates the Lesotho decentralized mini-grid energy systems landscape for traces of the energy democracy agenda as a globally sought-after discourse due to its nature to either be a deterrent or a stepping stone for sustainable energy development using an abductive research method. This discourse is especially important for knowledge production that can potentially inform national policy associated with the transition from productive use of energy to sustainable use of energy.
The report starts by scrutinizing the available written work on mini-grids as a whole, legal or otherwise, establishing the broad national perspective of the development of the mini-grids in Lesotho. This is then complemented by assessing existing case studies of Ha Makebe and Motete in rural Lesotho to primarily focus on the role that decentralization plays in elements of energy democracy in mini-grids developments. The research takes on a life-cycle approach as the main analytical framework, under which institutional processes and practices are matched across the four identified phases of the project life-cycle. This is further supported by evaluating the host communities on their status as energy citizens under the energy democracy agenda. The results of this research study demonstrate the status of the policy and legal framework to imply the energy democracy agenda rather than it is inferred. This observed state of policy and legal framework further spills into the formulation approaches on standard governance practices that focus on infrastructure optimization as opposed to project sustainability which speaks to the effectiveness of the institution to govern such developments. Lastly, the results of this study present the host beneficiaries as eager and willing citizens to exercise their collective role as energy citizens to institutionally hold other stakeholders accountable under the energy democracy agenda concerning the development of decentralized mini-grids in Lesotho as to achieve a just and equitable energy transition.
The potential impact of climate change on wind spped and solar radiation in Lesotho
(National University of Lesotho, 2024) Tsolele, Taelo; Mpholo, Moeketsi
In this study, a Jupyter Notebook software was utilized to study the potential impact of climate change on wind speed and solar radiation in Lesotho using a CORDEX-Africa regional climate model to simulate the past, present, and future climate conditions under different scenarios at 10 m above ground level. Historical climate data from 1950 to 2005 showed a consistent average wind speed of 1.50 - 3.0 m/s and solar radiation of 200 - 225 W/m2, except in the north-east of the country where the Butha-Buthe and Mokhotlong districts are located, solar radiation of 175 - 200 W/m2 was averaged. The RCP4.5 scenario projected a stable average wind speed ranging from 1.50 - 2.75 m/s except for the peak of 3.00 m/s in 2030. The projected solar radiation had a minimum average solar radiation of 150 W/m2 and a maximum average solar radiation of 275 W/m2, reaching up to 340 W/m2 by 2045. The RCP8.5 scenario projected a similar wind speed trend, exceeding 3.00 m/s from 2042 to 2045, and a peak solar radiation of 370 W/m² in 2043. These projections imply that Lesotho's solar and wind energy generation will not be negatively impacted, thus offering significant opportunities for sustainable energy development. The findings support investments in wind and solar infrastructure throughout the country, extending to places such as Butha Buthe, Quthing, and Mokhotlong with the newly acquired renewable energy resources due to climate change.
The impact of intermittent renewable energy generators on Lesotho National Electricity Grid
(National University of Lesotho, 2020) Mokeke, Sebota; Thamae, R
Lesotho is confronted with huge challenge of low electricity access, with 63.9 % of the population lacking access to electricity. Lack of electricity impedes both economic and social development. However, Lesotho has abundant renewable energy resources that can be exploited through large integration of renewable energy sources. The inherent variability and uncertainty of renewable energy sources (solar-PV and wind) creates both operational and planning challenges for the power system. This results in the reluctance of the power system operators integrating largescale renewables to the national grid due to the power system stability problems. The characteristics of the intermittent renewable energy generators mandates that careful grid impact studies be performed in ensuring that the power grid is operated stably.
The thesis focuses on the impact of the Intermittent Renewable Energy Generators (IREGs) on the power stability of Lesotho electrical grid considering both solar photovoltaic (PV) and wind generation at Ha-Ramarothole and Letseng respectively. The integration of IREGs involves both steady state and dynamic analysis of the electrical network. To this aim, the thesis assesses the impact of the IREGs on the stability of Lesotho electrical network at transmission level. In addition, maximum allowable penetration levels were determined at the point of interconnection.
Load flow simulations were performed to assess the steady state performance of the electrical network. Furthermore, the transient analysis was performed by applying the 3-phase short circuit at the critical points of the network and observing how voltage, frequency and rotor angle stability were affected and evaluated against grid code of Lesotho. The simulations were performed using DigSILENT PowerFactory software, which was used to model the electrical network of Lesotho. The maximum allowable penetrations for solar was about 19 % at substation at Ramarothole while for the wind it was found to be 27 % at Letseng substation. The simulations revealed that increased penetration of the IREGs led to grid instability. For all the simulations, frequency stability was observed except for the penetration of 36 MW for solar farm. The voltage violations at the Tlokoeng substation of 1.051 p.u. resulted from penetration limit of 52 MW capacity of the wind farm at Letseng. The solar penetration limit resulted from the rotor angle instability as increased penetration resulted in large rotor angle oscillations.