| 1. |
- Mulenga, Enock, et al.
(författare)
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Techno-economic analysis of off-grid PV-Diesel power generation system for rural electrification: A case study of Chilubi district in Zambia
- 2023
-
Ingår i: Renewable energy. - : Elsevier. - 0960-1481 .- 1879-0682. ; 203, s. 601-611
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Tidskriftsartikel (refereegranskat)abstract
- The study explores the techno-economic feasibility and viability of a Photovoltaic-Diesel Hybrid system for rural electrification in sub-Sahara Africa with a case study of Chilubi island, a remote district without access to electricity in the Northern Province of Zambia. Using HOMER (Hybrid Optimization of Multiple Electric Renewables) Pro software, the best and most feasible technical solutions through different hybrid system configurations, combinations and the district's rate of access to electricity were considered based on the least Levelized Cost of Energy (LCoE) and life cycle costs of the project. The results show that operating diesel generators as stand-alone is not economically sustainable and has a high LCoE. Influencing factors include variability in diesel pump prices, high fuel transportation costs, high cost of operation and maintenance, among other factors of concern. 100% photovoltaic (PV) with a battery system gave the lowest LCoE. However, the initial capital cost of solar energy projects in Zambia is relatively high compared to the equivalent diesel-based plants, as shown herein. It explains why diesel power plants are favoured for off-grid settlements. On the hand, the low operational cost and LCoE of PV power plants favour rural districts as they offset the high initial capital costs. Additionally, the continued downward trend in the cost of PV installations per kWp has opened discussions among policymakers and energy planners in Zambia to favour rural electrification with renewable energy-based power generation. This study contributes to this discussion.
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| 2. |
- Alhamwi, Mouaz, et al.
(författare)
-
Empirical Analysis of Voltage Variations in Low Voltage Distribution Grids from Photovoltaic
- 2019
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Ingår i: Solar Integration Workshop 2019. - : Energynautics GmbH. - 9783982008042
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The rapid expansion of photovoltaic (PV) systems has raised voltage concerns. This paper investigates voltage variations measured at four hundred on-line PV installations in Sweden. Small (<10 kW inverter size) three phase residential PV systems had the least impact whereas single phase systems had the most impact for the same amount of power injected per phase. PV systems were grouped based on post code location into urban and rural areas. Urban areas were found to be more resilient to PV induced voltage fluctuations with a narrower back-ground voltage band in comparison to rural areas, indicating that PV inverter measurements can be an efficient method to empirically determine grid strength.
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| 3. |
- Bollen, Math, et al.
(författare)
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Hosting Capacity of the Grid for Photovoltaic Installations : a Stochastic Approach Applied to Single-phase Connections
- 2018
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Ingår i: DIGITAL PROCEEDINGS. - : Energynautics GmbH.
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Konferensbidrag (refereegranskat)abstract
- This paper discusses the voltage rise due to PV installations connected to a low-voltage network. The connection of individual installations is studies for both single-phase and three-phase connection. A stochastic method is presented to estimate the hosting capacity. This method is illustrated for random and coordinated connection of single-phase installations. It is shown, in a number of ways, that the installation of large (e.g. 6 kW) single-phase connected units can easily result in unacceptable overvoltages.
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| 4. |
- Chirwa, Damaseck, et al.
(författare)
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Floating solar photovoltaic (FSPV) potential in Zambia: Case studies on six hydropower power plant reservoirs
- 2023
-
Ingår i: Renewable Energy Focus. - : Elsevier. - 1755-0084. ; 44, s. 344-356
-
Tidskriftsartikel (refereegranskat)abstract
- This study assesses the technical resource potential for floating solar photovoltaic systems on Zambia's existing hydro-based power plants. The research uses System Advisor Model (SAM) and has made some input changes to adapt the standard photovoltaic performance model to Floating Solar Photovoltaics. The input changes are the tilt angle and the losses. Tilt has been taken as 5o, while the soiling losses have been taken as zero (0). Zambia's theoretical maximum floating solar photovoltaic potential (100% coverage) was found to be 254.083 GWp. The floating solar photovoltaic potential in Zambia at 10% coverage is the best option. It was found to be 25.408 GWp, while the energy generated was 43,448.1212 GWh. Compared to the total installed electricity (3.011) GW, this power is 8 times more than the current installed capacity. Kariba dam shows the highest potential of 24.461 GWp, followed by Itezhi Tezhi (0.506 GWp), Kafue Gorge Upper (0.393 GWp), Mita Hills (0.0314) GWp, Mulungushi Dam (0.0131) GWp, and Kafue Gorge Lower (0.0043 GWp). The country has an average photovoltaics electricity daily output ranging from 4.54 to 4.85 kWh/kWp, which equates to 1658 to 1772 kWh/kWp totals. The findings of this study will increase public awareness of floating solar photovoltaic systems and It will allow the government and investors to consider investing in the technology. This shall ultimately increase power generation in Zambia, helping to alleviate the country's 0.81 GWp power deficit. The National Energy Policy facilitates the development and deployment of renewable and alternative energy sources like hydropower and solar photovoltaic power. Through this policy, an assessment of the resource potential for ground-mounted Solar photovoltaics has been conducted. The policy does not mention the new technology of floating solar photovoltaic systems, which benefits from an increased energy yield due to the cooling effect of water since it is located on the water's surface. Lower shading, decreased civil works, lower grid interconnection costs, reduced water evaporation, enhanced water quality, lowered algae blooming, and valuable land are released for other uses, such as agricultural land or residential developments, when existing water reservoirs are used. Some potential benefits come with the new technology, although it is still nascent.
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| 5. |
- Garskaite, Edita, et al.
(författare)
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Assessing aspects of solution-based chemical synthesis to convert waste Si solar cells into nanostructured aluminosilicate crystals
- 2024
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Ingår i: CrystEngComm. - : Royal Society of Chemistry. - 1466-8033. ; 26:17, s. 2221-2334
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Tidskriftsartikel (refereegranskat)abstract
- The end-of-life recycling of crystalline silicon photovoltaic (PV) modules and the utilisation of waste is of fundamental importance to future circular-economy societies. In the present work, the wet-chemistry synthesis route – a low-temperature dissolution–precipitation process – was explored to produce aluminosilicate minerals from waste c-Si solar cells. Nanostructured crystals were produced in an alkaline medium by increasing the reaction temperature from room temperature to 75 °C. The morphology of the produced crystals varied from nanolayered aggregates to rod-shaped crystals and was found to be dependent on the temperature of the reaction medium. Chemical and phase composition studies revealed that the synthesised compounds consisted of structurally different phases of aluminosilicate minerals. The purity and elemental composition of produced crystals were evaluated by energy dispersive spectroscopy (EDS) and micro X-ray fluorescence (μXRF) analysis, confirming the presence of Al, O, and Si elements. These results give new insights into the processing of aluminosilicate minerals with sustainable attributes and provide a possible route to reducing waste and strengthening the circular economy.
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| 6. |
- Kabanshi, Alan, et al.
(författare)
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Windows of Opportunities : Orientation, Sizing and PV-Shading of the Glazed Area to Reduce Cooling Energy Demand in Sub-Sahara Africa
- 2023
-
Ingår i: Energies. - : MDPI. - 1996-1073. ; 16:9
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Tidskriftsartikel (refereegranskat)abstract
- In hot climates, such as sub-Sahara Africa, window sizing and orientation pose challenges as they add, through solar insolation, to the building cooling energy demand and thus the cause of indoor overheating risk. This risk can be reduced through passive building-design-integrated measures, e.g., optimizing the window size, orientation and solar shading strategies. Through an IDA-ICE building performance simulation tool, the current study explores the impact of window size, optimization and building-integrated PV panels as shading strategies on cooling energy demands in three cities (Niamey, Nairobi and Harare) in sub-Sahara Africa. Results show that thermal comfort and cooling energy demand are sensitive to a window-to-wall ratio (WWR) > 70%, while the need for artificial lighting is negligible for a WWR > 50%, particularly in the north for cities in the Southern hemisphere and the south in the Northern hemisphere. A WWR > 70% in the east and west should be avoided unless shading devices are incorporated. Internal blinds perform better in improving occupant thermal comfort but increase artificial lighting while integrating PV panels, as external shading overhangs reduce cooling energy but also produce energy that can be utilized for building services, such as air conditioning. In this study, the results and implications of the optimization of window size, orientation and building-integrated shading and operation are discussed.
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| 7. |
- Mulenga, Enock, et al.
(författare)
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A review of hosting capacity quantification methods for photovoltaics in low-voltage distribution grids
- 2020
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Ingår i: International Journal of Electrical Power & Energy Systems. - : Elsevier. - 0142-0615 .- 1879-3517. ; 115
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Tidskriftsartikel (refereegranskat)abstract
- A literature review is presented in this paper of the methods for quantifying the solar PV hosting capacity of low-voltage distribution grids. Three fundamentally different methods are considered: i) deterministic ii) stochastic iii) time series. The methods’ outline of applications, merits and shortfalls are summarized. The methods differ in the input data, accuracy, accuracy, computation time, consideration of uncertainties, consideration of the time-related influence and the models used. Two types of uncertainties need to be considered: certain (aleatory) uncertainties and uncertain (epistemic) uncertainties. The latter ones are only included in some of the stochastic methods.In most of the reviewed publications, the voltage magnitude rise and increased loading with increased risk of overvoltage and overloading (for lines, cables and transformers) were the main phenomena considered in the hosting capacity study.This review offers guidelines for distribution system planners on which hosting-capacity method to be used and to researchers on research gaps.
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| 8. |
- Mulenga, Enock, et al.
(författare)
-
Adapted Stochastic PV Hosting Capacity Approach for Electric Vehicle Charging Considering Undervoltage
- 2021
-
Ingår i: Electricity. - : MDPI. - 2673-4826. ; 2:3, s. 387-402
-
Tidskriftsartikel (refereegranskat)abstract
- This paper presents a stochastic approach to single-phase and three-phase EV charge hosting capacity for distribution networks. The method includes the two types of uncertainties, aleatory and epistemic, and is developed from an equivalent method that was applied to solar PV hosting capacity estimation. The method is applied to two existing low-voltage networks in Northern Sweden, with six and 83 customers. The lowest background voltage and highest consumption per customer are obtained from measurements. It is shown that both have a big impact on the hosting capacity. The hosting capacity also depends strongly on the charging size, within the range of charging size expected in the near future. The large range in hosting capacity found from this study—between 0% and 100% of customers can simultaneously charge their EV car—means that such hosting capacity studies are needed for each individual distribution network. The highest hosting capacity for the illustrative distribution networks was obtained for the 3.7 kW single-phase and 11 kW three-phase EV charging power.
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| 9. |
- Mulenga, Enock, et al.
(författare)
-
Distribution networks measured background voltage variations, probability distributions characterization and Solar PV hosting capacity estimations
- 2021
-
Ingår i: Electric power systems research. - : Elsevier. - 0378-7796 .- 1873-2046. ; 192
-
Tidskriftsartikel (refereegranskat)abstract
- Solar photovoltaics in electricity distribution networks is often limited by the rise in voltage magnitude. The pre-connection voltage magnitude is an important factor that determines the hosting capacity.This paper studies to which extent details of the pre-connection voltage magnitude impact the hosting capacity. Extensive measurements of voltage magnitude and solar power production were obtained for a number of distribution networks with 10-minute resolution. The measured background voltage during the sunny-hours from the two-year measurements was used to obtain representative probability distribution functions. A guide for selecting the time-of-day (ToD) used is presented.The obtained probability distribution functions are applied to estimate the stochastic hosting capacity for a low-voltage distribution network with 83 customers. The impact of various details on the hosting capacity are studied.The results show that general knowledge about the range of the pre-connection voltage are essential for the hosting capacity estimation. Measurements over one year were shown to be sufficient to estimate the hosting capacity. The hosting capacity considering the entire day was underestimated by 11 % when compared to the 10 am – 2 pm sunny-hours. The proposed method is general and can be applied to other aleatory uncertainties and other types of hosting capacity studies.
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| 10. |
- Mulenga, Enock
(författare)
-
Fuel Cell Technology: An Optional Back-Up Power Supply System for Zambia
- 2018
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Ingår i: Proceedings of the Engineering Institution Of Zambia 2018 Symposium. - Livingstone, Zambia : Engineering Institution Of Zambia. ; , s. 12-22
-
Konferensbidrag (refereegranskat)abstract
- Fuel cell technology is slowly growing in other countries and is being used for power production. In Zambia, the technology is yet to penetrate. The increase in power demand at a time of poor rainfall patterns entail diversification to other power sources. This paper presents knowledge on fuel cell technology, types, applications, sample simulation and its adaptation to Zambia as back-up power supply from literature, applied systems and simulation set-up in matlab-simulink. Massive investment in solar technology, rise in fuel prices for diesel generators and possibility of combining fuel cell with photovoltaics or as storage to store away variability has necessitated the review of this technology as an optional back-up power supply for Zambia. The sample simulation of a 6 kW fuel cell system in Matlab showed results of dc power. The same power type from PV array before power conditioning. Fuel cell technology exist in different types due electrolyte used. These are proton exchange membrane, phosphoric acid fuel cell, alkaline fuel cell, direct methanol fuel cell, solid oxide fuel cell and molten carbonate fuel cell. Systems of sizes up to 59 MW have been installed. The by-products of industrial, mining and metallurgical processes (oxygen and hydrogen) could make implementation much feasible. Large investments in photovoltaics, which could share power conditioning equipment with fuel cell technology, could aids this technology in Zambia. Fuel cell technology system is possible as an optional power source for Zambia. It can be used as a stand-by unit, part of a hybrid system, an independent power plant and storage for photovoltaic (PV) systems.
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| 11. |
- Mulenga, Enock, et al.
(författare)
-
Impact of Service and Feeder Cable Upgrade on Hosting Capacity for Single Phase Connected Photovoltaics
- 2018
-
Ingår i: Proceedings of International Conference on Harmonics and Quality of Power, ICHQP. - : Institute of Electrical and Electronics Engineers (IEEE). - 9781538605172
-
Konferensbidrag (refereegranskat)abstract
- The addition of photovoltaics (PV) to a grid impacts the performance of that grid in a number of ways. These impacts limit how much PV can be connected, termed ‘hosting capacity (HC)’. The impacts include overvoltage and overloading. Mitigation of impacts can be achieved in different ways: in this paper, upgrade of service cable and feeder cable has been considered, one of the classical solutions. Cable size upgrades to 16, 25 and 35 mm2 from 10 mm2 have been studied to mitigate overvoltages in a 28-customer Swedish suburban grid. A stochastic planning-based approach has been used to obtain a performance parameter that can be used to compare the mitigation methods. The results showed an improvement in overvoltage and hosting capacity with cable upgrade. The hosting capacity is also shown to be sensitive to the risk chosen and to the PV size.
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| 12. |
- Mulenga, Enock, et al.
(författare)
-
Likelihood of Overload due to connected Solar PV
- 2021
-
Ingår i: CIRED 2021 - The 26th International Conference and Exhibition on Electricity Distribution. - : Institution of Engineering and Technology. ; , s. 2376-2380
-
Konferensbidrag (refereegranskat)abstract
- This paper applies a deterministic and stochastic approach to estimate the hosting capacity and likelihood of an overload at the cable cabinet or transformer due customers with solar PV. Distribution networks at 10 kV, suppling feeders with 1300 MV/LV transformers, have been studied. The paper also quantifies whether overvoltage or overload limits the hosting capacity first. Voltage and current measurements from a Northern Sweden distribution network have been applied in the paper. Illustrations are used to show the concept and important results are obtained. It is shown in the paper the hosting capacity is determined more often by overload than by overvoltage. In this paper, only the hosting capacity with reference to the overload limit is considered. The results obtained for the data used show that the overload limit is exceeded more often for transformers than for cable cabinets. The stochastic approach applied to the cable cabinets yields a small probability to exceed the hosting capacity.
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| 13. |
- Mulenga, Enock, et al.
(författare)
-
Limits set by component loadability on solar power integration in distribution networks
- 2022
-
Ingår i: Electric power systems research. - : Elsevier. - 0378-7796 .- 1873-2046. ; 209
-
Tidskriftsartikel (refereegranskat)abstract
- This paper proposes a deterministic and stochastic approach to quantify the hosting capacity that is often limited by the loadability limit of the cable cabinet or transformers due to customers with solar photovoltaics (PV) units. Distribution networks from two areas in Sweden supplying 309 MV/LV distribution transformers with 12,000 customers downstream have been studied. Using a deterministic model, a method is proposed and applied to assess the cable overvoltage against the loadability while considering the voltage rise margin. In addition, measurements have been applied to the methods and the loadability limits assessed. Illustrations for the concepts and important results for the guide to DSOs decision-making guide has been obtained. It is shown in the paper the hosting capacity anticipated at the end of a distribution network cable with a particular size is determined more often by the loadability at larger voltage rise margin and by overvoltage at smaller voltage rise margins. The results obtained for the data used show that the overload limit is exceeded more often for transformers than for cable supplying the cable cabinets at smaller solar PV sizes. For larger solar PV sizes, the feeder cable loadability limit is likely to be exceeded first before that of the transformers. The stochastic approach applied to the yields a small probability to exceed the hosting capacity and depend on the two epistemic uncertainties.
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| 14. |
- Mulenga, Enock, et al.
(författare)
-
Multiple distribution networks hosting capacity assessment using a stochastic approach
- 2023
-
Ingår i: Sustainable Energy, Grids and Networks. - : Elsevier Ltd. - 2352-4677. ; 36
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Tidskriftsartikel (refereegranskat)abstract
- About 15 000-customers are connected to the individual secondary distribution networks supplied through 48-medium voltage 10 kV radial feeders. The hosting capacity assessment uses the end-customer voltage magnitude rise and transformer thermal overload. The hosting capacity is estimated by applying the “stochastic mixed aleatory-epistemic method” to determine the voltage magnitude rise and load flow with solar PV. The minimum power consumption is compared with the solar PV power infeed through the individual transformers. The hosting capacity estimation is done for three-phase connected solar PV sizes from 3 to 18 kW. At moderate PV penetration (25%–50%), the results showed that overvoltage would limit the hosting capacity more often than overload, but it becomes an issue only for LV networks studied with more than 8-customers. Considering all LV networks, most of the customers could install 6 kWp. Even when installing PV systems of 18 kWp (about twice the average size today and about the maximum area of a typical residential roof), two-thirds of houses would not need an upgrade to withstand SS-EN 50160 voltage limits. The latter customers can connect solar PV units with 18 kWp size without overvoltage or overload issues.
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| 15. |
- Mulenga, Enock
(författare)
-
On the hosting capacity of distribution networks for solar power
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The future will bring changes in energy production and consumption that will affect the performance of electricity distribution networks. Electric vehicle charging will increase consumption; the installation of solar photovoltaic (PV) units will increase production. Both will change the energy flow and affect the power quality. The installation of solar PV units or electric vehicle (EV) charging has a limit above, which they unacceptably deteriorate the distribution networks' performance. This limit is referred to as the hosting capacity of the distribution network. This work is about developing, applying and studying methods for estimating the hosting capacity, especially solar PV. Three fundamentally different methods to estimate solar PV hosting capacity for single-phase and three-phase units have been identified by a detailed review of the literature: deterministic, stochastic and time-series. The methods were shown to differ in the required input data, accuracy, computation time, consideration of uncertainties, and time-correlation between different phenomena. The methods have also been compared in relation to their application for the assessment of connection requests (screening) or detailed analysis. Solar power production, energy consumption and distribution networks’ all have uncertainties associated with them. It is helpful to distinguish between two types of uncertainties when estimating the hosting capacity: aleatory (“certain”) and epistemic (“uncertain”) uncertainties. A stochastic approach, ‘mixed aleatory-epistemic’, was applied to about 1500 low-voltage distribution networks. A similar stochastic approach and models were applied to estimate low-voltage networks' hosting capacity for electric vehicle charging. A deterministic method was applied to determine the hosting capacity considering the thermal overload phenomenon for both PV and EV charging. A planning risk has been introduced to quantify the risk of the distribution network not being able to cope with a future penetration of solar PV or EV charging. The planning level entails that a distribution network operator accepts a certain risk of exceeding the overvoltage limit. The concept has been applied as part of the stochastic approach. The hosting capacity for a distribution network is quantified considering a performance index and a limit to what is an acceptable deterioration of that index. The 90th percentile of the annual peak demand (overvoltage or overload) has been used as a performance index in most of the hosting capacity studies in this work. The time-of-day (ToD) and time-of-year (ToY) concepts were introduced to model the aleatory uncertainties. The time-of-day exemplifies the relevant part of the day, and the time-of-year shows the parts of the year applicable for hosting capacity studies when high solar power production can be expected. The time-of-day of 10 am to 2 pm has been applied. The period from 21st March to 21st September was the applied time-of-year. The latter two, ToD and ToY, need to be defined for the application of the concept to other areas than those covered in this work. It was shown that the hosting capacity would be underestimated by about 10% if an incorrect ToD were used. Voltage magnitude and solar power production measurements, over one year with a 10-minute resolution, were obtained for thirty-three 10/0.4 kV distribution transformers in Northern Sweden. A method of obtaining the ‘background voltage’ from the measurements was formulated. The background voltage (including its uncertainties) was one of the factors with the greatest influence on the hosting capacity. Stochastic models for distribution networks were built, and the hosting capacity for low voltage distribution networks has been studied. The outcome shows that three-phase solar PV units have a higher hosting capacity than single-phase units. The model and method developed can be used as a planning tool by distribution network operators (DSOs). The inclusion of the uncertainties and correct handling of planning risks is paramount for decision making by DSOs. The results show that background voltage variations should be considered from measurements, and appropriate ToD/ToY should be used. The quantification of the hosting capacity requires both consumption and voltage measurements in the distribution networks. The work has also shown that the time of the day and year (ToD and ToY) need to be considered for the many hosting capacity methods. The impact is expected to be highest in the ToD and ToY. Also, the two types of uncertainties have been clarified in this work. They need to be considered as the decisions DSOs make will depend on them. This work has generally found that hosting capacity estimation methods are many and different. They are all applicable and useful tools for identifying the factors in distribution networks that can hold up solar PV and EV charging penetration. It has also been found that there is a strong link between distribution network planning and hosting capacity estimation methods. The hosting capacity methods in this work can undertake the risks connected to solar PV and EV charging.
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| 16. |
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| 17. |
- Mulenga, Enock, et al.
(författare)
-
Overvoltage due to single-phase and three-phase connected PV and what to do about it
- 2019
-
Ingår i: CIRED 2019 Proceedings. - : AIM.
-
Konferensbidrag (refereegranskat)abstract
- This paper presents the overvoltage caused by single and three-phase connected PV to a low-voltage distribution grid. Statistics are obtained based on source-impedance data for 40 000 customers. A stochastic approach is applied to a 28-customer low-voltage network and the probability of overvoltage is assessed. It is shown that the voltage rise due to single-phase connected PV is six times the rise for three-phase connected PV.To mitigate the overvoltage, grid-reinforcement, reactive power compensation, curtailment and coordinated connection of PV can be used. It is shown that reactive compensation is not effective in LV grids due to high R/X ratio. Coordinated connection helps in reducing the overvoltages caused by single-phase PV.Policy suggestions towards three-phase PV installations and coordinated single-phase PV connections are included in the paper.
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| 18. |
- Mulenga, Enock, et al.
(författare)
-
Regional Distribution Network Hosting Capacity Assessment Using a Stochastic Approach
-
Annan publikation (populärvet., debatt m.m.)abstract
- The stochastic approach is applied to 1264-LV distribution stations’ networks to estimate the hosting capacity. About 15,000 customers are connected to the individual secondary distribution networks. The secondary distribution networks are supplied through 48-medium voltage radial feeders. The voltage magnitude rise and thermal overload are used for the hosting capacity assessment. The hosting capacity is estimated by applying the ‘‘stochastic mixed aleatory-epistemic method’’ to determine the voltage magnitude rise and load flow due to solar PV. The minimum power consumption is compared with the solar PV power infeed through the individual DS transformers. The hosting capacity estimation is done for solar PV sizes of 3, 6, 9, 12, 15 and 18 kW three-phase connected. . The results showed that overvoltage becomes an issue for DS with more than 8-customers and will limit the hosting capacity than the overload. About 31% of the customers can be allowed to connect solar PV units with 18 kWp size considering the overvoltage limit when 25% and 50% penetration is considered for the DS with 1-8 customers and more than 8-customers.
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| 19. |
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| 20. |
- Mulenga, Enock, et al.
(författare)
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Solar PV hosting capacity methods and industrial application gaps
- 2021
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Ingår i: CIRED 2021 - The 26th International Conference and Exhibition on Electricity Distribution. - : Institution of Engineering and Technology. ; , s. 1757-1761
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Konferensbidrag (refereegranskat)abstract
- With falling prices both the size and number of installations of single-phase and three-phase solar photovoltaics (PV) units is expected to continue to increase in distribution networks. The increase in solar PV units will have an impact on the power quality of the distribution network. There is a need to propose transparent methods that can be used to quantify the acceptable limit of solar PV penetration objectively, called the hosting capacity (HC). The fundamental methods for the quantification of hosting capacity include; deterministic, stochastic and time-series. Which of the latter method is the most appropriate for determining the hosting capacity? A comparison of the three methods based on the input data need, accuracy, uncertainties considered, time-related and models are done. Many academic and industrial studies have been published applying the hosting capacity method. Differences between the scientific and industrial application of the hosting capacity methods are presented in this paper. There is a need to expose the industrial application of solar PV hosting capacity methods.
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| 21. |
- Mulenga, Enock
(författare)
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Solar PV Stochastic Hosting Capacity Assessment Considering Epistemic (E) Probability Distribution Function (PDF)
- 2022
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Ingår i: Electricity. - : MDPI. - 2673-4826. ; 3:4, s. 586-599
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a stochastic approach to assessing the hosting capacity for solar PV. The method is part of the optimal techniques for the integration of renewables. There are two types of uncertainties, namely aleatory and epistemic uncertainties. The epistemic and aleatory uncertainties influence distribution networks’ hosting capacity differently. The combination of the two uncertainties influences the planning of distribution networks. The study introduces and considers the epistemic probability distribution function (PDF). DSO does take levels of risk for a parameter violation when planning. Epistemic PDF is a range of values of the planning risk margin for quantifying the hosting capacity. The planning risk acknowledges that overvoltages may occur at weaker conceivable locations in a distribution network. In the paper, it has been shown that the number of customers who will be able to connect solar PV in future is influenced by the DSO’s planning risk margin. The DSO can be stricter or less strict in planning risk margin. It has been concluded that fewer customers can connect solar PV to a distribution network when a DSO takes a stricter planning risk. Alternatively, more customers can connect solar PV units for a less strict planning risk. How stricter or less strict the DSO is with the planning risk margin determines the investment needed for mitigation measures. The mitigation measures in the future will lead to not exceeding the overvoltage limit when solar PV is connected to the weaker conceivable points of the distribution network.
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| 22. |
- Mulenga, Enock, et al.
(författare)
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Solar PV stochastic hosting capacity in distribution networks considering aleatory and epistemic uncertainties
- 2021
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Ingår i: International Journal of Electrical Power & Energy Systems. - : Elsevier. - 0142-0615 .- 1879-3517. ; 130
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Tidskriftsartikel (refereegranskat)abstract
- This paper proposes a stochastic method, ''mixed aleatory-epistemic“, for estimating solar PV hosting capacity (HC) of low-voltage (LV) distribution networks. The approach treats the aleatory and epistemic uncertainties in a different way. The HC is estimated by applying the transfer impedance matrix, 'which is only calculated once', and the superposition principle to determine the voltage magnitude rise due to solar PV. By distinguishing between aleatory and epistemic uncertainties, the calculations are limited to the relevant hours (time-of-day or time-of-year) during which high solar PV production is expected. In this way, the random aleatory uncertainties (background voltage, solar PV production, local consumption) are modelled by their probability distributions during the selected time period. The distributions for the epistemic uncertainties (installed capacity per customer, number of customers with solar PV, phase to which single-phase units are connected) are created with simple models involving the interval value and possible occurrence. The stochastic approach proposed is applied to three LV distribution networks to illustrate the method. The results show that both types of uncertainties affect the HC. The need for distribution network planners to identify and distinguish between the types of uncertainties is emphasised.
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| 23. |
- Mulenga, Enock, et al.
(författare)
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The Importance of Power Quality Monitoring for Modern Network Operators and Industries in Zambia
- 2018
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Ingår i: Proceedings of the Engineering Institution Of Zambia 2018 Symposium. - Livingstone, Zambia : Engineering Institution Of Zambia. ; , s. 23-39
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Konferensbidrag (refereegranskat)abstract
- Modern electricity networks contain a mixture of different types of loads all of which affect the voltage one way or the other. They can either improve or deteriorate the so-called “voltage quality”, also known as “power quality” or “quality of power” that is being supplied by network operators and received by their customers. Increased use of power electronic devices for the control of rotating electrical machines and the presence of sensitive electronic equipment has further affected the power quality. The impact of new equipment is rarely an improvement, although it is often less than feared at first. The shortage of rainfall has resulted in a lot of investment in solar photovoltaics power, which has the potential to further worsening the power quality in the Zambian power network. To quantify the impact of these and other changes on the power quality requires monitoring of voltage and current with high accuracy and time resolution. The results of such a power-quality monitoring program will form a base to identify and, when needed, mitigate any problems. The use of class A power monitoring instruments is an important part in such a program. The requirements to which such instrument should comply are in the Zambia grid code, ZS 387 standard and in international standards (EN 50160, IEC 61000-4-30 and IEC 61000-4-7). The investment and use of class A power quality instruments has reported saving gains at Copperbelt Energy Corporation plc in Zambia and by companies around the world. The use of such instruments has resulted in power quality issues being identified, bench-marked, broad exchange of knowledge and remedial actions implementations. This is an indication of the importance of power quality monitoring for network operators and industrial customers in Zambia using class A instruments.
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| 24. |
- Mulenga, Enock, et al.
(författare)
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The Role of Aleatory and Epistemic Uncertainties in a Stochastic Hosting Capacity Approach for Solar PV
- 2019
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Ingår i: Proceedings of 2019 IEEE PES Innovative Smart Grid Technologies Europe (ISGT-Europe). - : IEEE.
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Konferensbidrag (refereegranskat)abstract
- This paper introduces the terms aleatory and epistemic uncertainties for use in a stochastic hosting capacity method. The role these uncertainties play in the hosting capacity determination is illustrated. It is shown that distinction between aleatory (statistical) and epistemic (systematic) uncertainties is helpful to characterize the probability distributions correctly. For epistemic uncertainties, it is often challenging to obtain information on the probability distribution function. For aleatory uncertainties, a method for characterizing the probability distribution is presented. Aleatory uncertainties’ data measurements are used to obtain a distribution best-fit. The background voltage measurement for a customer in a low-voltage distribution network is used to illustrate the method. Values were obtained for the distribution functions of the three-phase voltages. The used distribution functions are found to influence the resulting hosting capacity. This entails that there is need for measurements and data collection. A research challenge remaining concerns the stochastic model of epistemic uncertainty.
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| 25. |
- Mupeta, Henry, et al.
(författare)
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Techno-economic analysis of PV-Diesel hybrid system as an option for rural electrification in Zambia
- 2021
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Ingår i: 13<sup>th</sup> Internationational conference on Sustainable Energy and Environmental Protection: Solar Energy, Vienna, Austria, September 13-16, 2021. - 9783900932879
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Konferensbidrag (refereegranskat)abstract
- The study explores the viability of the PV-Diesel Hybrid system for rural electrification in Sub-Sahara Africa with a study case of a remote district without access to electricity in the Northern Province of Zambia. Using HOMER (Hybrid Optimization of Multiple Electric Renewables) software, the study investigates the best and most feasible technical solution through different hybrid system configurations and combinations, taking into account the least Levelized Cost of Electricity of the project. The results show that operating diesel generators as stand-alone is not economically sustainable and gives a high LCoE due to variability in diesel pump prices, and a high cost of operation and maintenance. Furthermore, the study shows that the initial capital cost of solar energy projects in Zambia is relatively high compared to the equivalent diesel-based plants. However, the authors project that this will likely change because of the continued downward trend in capital costs of PV per kWp. Additionally, the high initial capital costs are offset by the low operational costs and the clean/environmentally friendly energy from PV systems.
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| 26. |
- Sudha Letha, Shimi, et al.
(författare)
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Power Quality Issues of Electro-Mobility on Distribution Network—An Overview
- 2023
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Ingår i: Energies. - : MDPI. - 1996-1073. ; 16:13
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Forskningsöversikt (refereegranskat)abstract
- The journey towards sustainable transportation has significantly increased the grid penetration of electric vehicles (EV) around the world. The connection of EVs to the power grid poses a series of new challenges for network operators, such as network loading, voltage profile perturbation, voltage unbalance, and other power quality issues. This paper presents a coalescence of knowledge on the impact that electro-mobility can impose on the grid, and identifies gaps for further research. Further, the study investigates the impact of electric vehicle charging on the medium-voltage network and low-voltage distribution network, keeping in mind the role of network operators, utilities, and customers. From this, the impacts, challenges, and recommendations are summarized. This paper will be a valuable resource to research entities, industry professionals, and network operators, as a ready reference of all possible power quality challenges posed by electro-mobility on the distribution network.
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