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A novel approach for sizing and optimization of hybrid solar-PV, biogas-generator, and batteries system for rural electrification: case study
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The objective of this study was to carry out a comparative analysis of the influence of the properties of the construction materials of the biodigester based on three different materials (steel, plastic PVC, and concrete) to predict the rate of biogas production from the anaerobic digestion of slaughterhouse waste. The input parameters were substrate temperature, ambient temperature, biogas temperature, biodigester temperature, specific biogas production rate, and material properties. A thermal model was developed using MATLAB® software to predict biogas production, with readily available input data for an unheated, uninsulated, and partially buried biodigester. The results obtained showed that the temperatures and the average daily biogas productions were higher for the steel biodigester (1.5 ± 0.12 m3/day at 36 ± 2℃) than those produced from the PVC (1.3 ± 0.1 m3/day at 31 ± 1.5℃) and concrete (1.2 ± 0.05 m3/day at 27 ± 2℃) biodigesters. Moreover, the production of electricity for a steel biodigester (14.64 kWh) was found to be greater than that produced from the PVC (12.81 kWh) and concrete (10.98 kWh) biodigesters. The results showed that the properties of the construction materials of the digester had a significant influence on the temperature and production of biogas, and therefore on the production of electricity. On the other hand, among the three materials studied, steel was the material, which yielded the best results. The proposed model gave rRMSE values between 7.4 and 8.3% and R2 between 0.92 and 0.96.
Access to uninterrupted power is not a luxury but a basic need. Rural communities living far from the national grid, particularly those in the southern region of Pakistan’s Khyber Pakhtunkhwa province, have limited access to a reliable power supply. In order to provide sustainable electricity, small-scale off-grid renewable energy systems are increasingly used for rural electrification. These systems are commonly known as stand-alone home systems or community micro-grids. This paper proposes an off-grid solar–biogas micro-grid for rural communities in the Lakki Marwat district of Khyber Pakhtunkhwa, Pakistan. The area is mainly dependent upon income from the agricultural and livestock sectors. HOMER was used to simulate the electric power system, while RET-Screen was used to analyze the economics of the system. The optimized system’s results demonstrate that the most economically and technically possible system, which produces 515 kWh and 338.50 m3 biogas daily, is made up of a 30-kW photovoltaic system coupled with a 37-kW biomass hybrid system, a 64-kWh battery storage capacity, and a 20-kW invertor. The system will meet the cooking and power needs of 900 individuals who reside in 100 homes. In addition to household users, the system will provide fixed-priced electricity to productive buildings, and free electricity to community buildings. The system will generate 1300 kg of organic fertilizer each day, which will be sold to local farmers for 50% less than what it would cost on the open market. The proposed approach is techno-economically viable based on the payback period and internal rate of return.
This study evaluates the hydropower potential in the design of a micro-hydro/solar photovoltaic hybrid system with battery energy storage for increasing the access to electricity in Ikukwa Village in Mbeya Region of Tanzania. Usually, hybridized hydropower schemes are designed from perennial streams for the provision of electricity. This study incorporates the run-of-the river (COE) power scheme, which originates from the untapped potential of nonperennial hydro-energy source and the use of traditional approach of data measurements for Ikata tributary to design hybrid system. The system is optimized by the minimization of the total net present cost (NPC) and cost of energy (COE) using the soft computing method of Hybrid Optimization of Multiple Energy Resources (HOMER) software and artificial intelligent (AI) techniques. AI optimization techniques such as particle swarm optimization (PSO), grey wolf optimization (GWO), and GWO-PSO hybrid (GWO-PSOHD) algorithms have been employed for further optimal results. The data for solar radiation and the tributary have been obtained from the National Aeronautics and Space Administration (NASA) and traditional methods of measurements, respectively. The estimated maximum water flow rate and head are 2.943 m3/s and 13 m, respectively. In the same period, the approximated theoretical power potential of the tributary is found to be 375 kW. Total NPCs obtained from HOMER, PSO, GWO, and GWO-PSOHD methods are $ 141, 397.76, $ 95 167.21, $ 92 472.82, and $ 91,854.10, respectively. Similarly, the optimal results of COE from HOMER, PSO, GWO, and GWO-PSOHD approaches are $ 0.1818/kWh, $ 0.1185/kWh, $ 0.1182/kWh, and $ 0.1181/kWh, respectively. Comparatively, PSO implementation has indicated the greatest energy cost, while the cost acquired by GWO-PSOHD is the lowest for all aforementioned AI optimization techniques. The tributary under study has a high potential of diversification of energy sources for rural electrification in the area of study and other parts of the world with comparable conditions.
Globally, reliable access to electricity improves people’s well-being, provides quality education, and promotes good health. Greenhouse gas emissions associated with fossil fuel combustion have incited an intense interest in low-carbon technologies for power generation. This study analyses the prospect of utilising a solar PV/biogas/battery hybrid energy system to provide electricity for Ghana’s remote communities. The study goal is to utilise locally available renewable energy resources to achieve a cost-effective levelized cost of electricity (LCOE) and mitigate greenhouse gas emissions. Hybrid Optimisation of Multiple Energy Resources (HOMER) software was employed to model and analyse the hybrid energy system’s technical, economic, and environmental aspects. The findings indicate that PV/biogas/battery system perform better than PV/diesel/battery and diesel-only systems in terms of cost and emissions reductions. Also, the LCOE generated from the PV/biogas/battery system is around 0.256 $/kWh. However, this LCOE is only about 64% higher than the LCOE for Ghana’s household residents. The sensitivity test indicates that the PV/biogas/battery system is sensitive to discount rates and capital subsidies, making it attractive for future development. This attests that Ghanaian rural communities without electricity access and with substantial biomass potential are likely to be electrified when given the necessary attention. Moreover, this project could be a viable alternative to rural electrification in Ghana with proper investment support.
The popularity of Electric Vehicles (EVs) is increasing day by day in the modern world. The charging of EVs from the grid-connected charging stations causes a considerable power crisis in the grid. Integrating renewable energy resources (RESs) with conventional energy sources in the power grid is now considered feasible to reduce peak power demand and the inevitable emission effect. Hence, this paper presents an energy solution for EV charging with two RESs namely solar and biogas. HOMER software is utilized to analyze the potency and functionality of solar PV and biogas-based- EV charging stations. The proposed system consists of a solar PV system, two biogas engine generators, and a bidirectional converter with battery storage. The variation of different costs such as net present cost (NPC), initial cost, and cost of energy (COE) for different solar PV systems (3 kW, 4.5 kW, 6 kW, and 9 kW) are analyzed in HOMER software. The 4.5 kW solar PV system is finally selected as the NPC, initial cost, and COE are $93530, $19735, and $.181, respectively, which is efficient. The system's lifetime is 25 years, where initial 12 years is required to overcome system cost, and the rest 13 years will provide financial benefits. The study illustrates the effect of solar irradiance, biomass, and the change in the load in the energy management system. The techno-economic analysis shows that the proposed scheme can be an effective energy solution. The emission of greenhouse gases (GHGs) such as CO2, CO, SO2, and NOX is reduced considerably compared to other existing techniques. The study is expected to be beneficial in renewables-based EV charging systems with techno-economic and environmental feasibility.
There is a need to develop an optimization tool that can be applied in the feasibility study of a hybrid renewable energy system to find the optimal capacity of different renewable energy resources and support the decision makers in their performance investigation. A multi-objective function which minimizes the Levelized Cost of Energy (LCOE) and Loss of Load Probability Index (LLPI) but maximizes the novel Energy Match Ratio (EMR) was formulated. Simulation-based optimization method combined with ε-constraint technique was developed to solve the multi-objective optimization problem. In the study, ten-year hourly electrical load demand, using the end-use model, is estimated for the communities. The performance of the developed algorithm was evaluated and validated using Hybrid Optimization Model for Electric Renewables (HOMER®) optimization software. The developed algorithm minimized the LCOE by 6.27% and LLPI by 167% when compared with the values of LCOE ($0.444/kWh) and LLPI (0.000880) obtained from the HOMER® optimization tool. Also, the LCOE with the proposed approach was calculated at $0.417/kWh, which is lower than the $0.444/kWh obtained from HOMER®. From environmental perspective, it is found that while 141,370.66 kg of CO2 is saved in the base year, 183,206.51 kg of CO2 is saved in the ninth year.The study concluded that the approach is computationally efficient and performed better than HOMER® for this particular problem.The proposed approach could be adopted for carrying out feasibility studies and design of HRES for Off-Grid electrification, especially in the rural areas where access to the grid electricity is limited
The demand for electricity in remote rural areas is a major obstacle to their development. The extension of the
grid network to remote rural areas has been identified as a difficult topography for complex constructions and enormous
investments. The development of off-grid renewable energy generation technologies offers the opportunity for tackling these
challenges. This study provides a techno-economic feasibility analysis of an off-grid hybrid renewable energy system for a
rural village of district Kech, Balochistan, Pakistan. The proposed hybrid system integrates the different combinations of the
wind turbine, solar PV modules, and battery backups to meet the required electric load demand. The hybrid system is modeled
and optimized through a powerful simulation software Hybrid Optimized Model for Electric Renewable (HOMER-Pro). The
optimized configuration of the hybrid system consists of wind turbines (12kW), solar PV (103kW), 224 lead-acid batteries
(72.4Ah each), and 29.1 kW converters. The simulation results show that the proposed system can meet the power
requirements of 197.74kWh/day primary demand load with 27.87kW peak load. This system configuration has the Net Present
Cost (NPC) of $127,345 and Cost of Energy (COE) of 0.137$/kWh with a 100% renewable fraction. Furthermore, the results
of the present study are compared with the literature and have resulted in a cost-effective hybrid renewable energy system with
a low COE.
The assessment of the suitability of a wind system depends largely on the prediction of the wind potential. Indeed, the variability and uncertainty inherent in renewable energy sources can have a significant impact on accurate and reliable prediction of the power produced. Wind sources are needed at different time stages and at different altitudes. Thus, putting in place tools for predicting these wind resources is essential for their effective integration in the frame of electricity generation. In this context, the paper of this study is to propose a short-term wind energy prediction method through the formation of historical wind velocity data based on neural networks. This assessment involves modelling wind speed using ANN through the feed-forwad network. So, ANN are at the basis of adaptive identification methods and intelligent command laws. In this sense, first, the process of forecasting wind energy involves the creation of a raw data base, which is then filtered by probabilistic neural network. More concretely, the contribution of the work can be given in the form of technical results. These results start with a proposal of the theoretical models, then it is given the approach method that is used, then it is proposed the design of the system and the whole is closed by a performance evaluation. As far as performance evaluation is concerned, it is presented in the form of the results of analysed simulations of the forecast model. In practical terms, it should be noted that the proposed model also provides a high degree of accuracy for the measured data. In the end, normalized average absolute errors were recorded between 4.7% and 4.9%. As, it was found a regression factor R (measures the correlation between output-Target) between 91% and 96% for the site of the northern Mauritanian coast. This is largely acceptable for similar calculations.
The introduction of a decentralized energy system in remote rural areas with limited or no access to power supply can improve the quality of life of people living in these areas. Renewable energy technology can play a key role in electricity generation, as grid expansion is not a cost-effective option. In this study, we focused on the techno-economic feasibility and optimal design of a hybrid micro-hydro-photovoltaic-diesel-battery-wind power system designed to electrify a typical remote village located in the southern part of Nigeria. We aimed at achieving the electrification at minimal cost while taking into cognizance the constraints of environmental pollutant emission. In this study, the technical details, as well as the economic feasibility of setting up such a power system, were determined using the hybrid optimization of multiple energy resources (HOMER) simulation tool. Different combinations of energy resources including solar, wind, hydro, and diesel were compared and analyzed. The system performance and economics using some determinant factors such as the cost of energy, operation, and maintenance cost, net present cost, excess electricity, capacity shortage, generator fuel consumption rates, and cost, load fulfillment, and CO2 and other pollutant gas emission savings were determined. The experimental results and the comparative analysis revealed that a hybrid hydro/PV/wind/diesel/battery system was the most ideal and preferred option for off-grid rural electrification. The simulation results also indicated that the optimal system had a net present cost (NPC) and cost of energy (COE) of $1.01 m and $0.106/kWh, respectively, with a renewable fraction of 77.4% and environmental pollutant emission of 228,945 kg/year. This system was found to be environmentally friendly as it emitted the least pollutant gas among all the considered configurations. Bearing in mind the recent advocacy towards the actualization of Sustainable Development Goal (SDG) number 7, this work was found to be in alignment with the tenet of “Affordable and Clean Energy”.
The majority of rural communities in developing countries (such as Peru) are not connected to the electrical grid. Hybrid energy production from available renewable resources (e.g., wind and solar) and diesel engines is considered as an economically viable and environmentally friendly alternative for electrification in these areas. Motivated by the lack of a comprehensive investigation dedicated to the techno-economic analysis of hybrid systems (PV–wind–diesel) for off-grid electrification in Peru, the present work is focused on determining the optimal configuration of these systems for remote Peruvian villages. Three small communities without access to the grid (Campo serio, El potrero, and Silicucho), which are located in different climatic zones of Peru, have been accordingly selected as case studies. Seven different configurations including single component systems (solar, wind, and diesel) and hybrid ones are considered. While taking into account the meteorological data and load characteristics of the communities along with the diesel fuel’s price and the cost of components, HOMER software is utilized to determine the optimal sizing of the system [resulting in the lowest net present cost (NPC)] considering different scenarios. The obtained configurations are then compared considering other state-of-the-art economic indices [initial capital cost, total annual operating cost, and the cost of energy (COE)], the generation fractions, and the resulting CO2 emissions. The obtained results have revealed that, for all of the investigated communities, the hybrid solar–wind–diesel system is the most economically viable scenario. Considering the latter scenario, the obtained optimal configuration leads to an NPC of USD 227,335 (COE: 0.478 USD/kWh) for Campo serio, USD 183,851 (COE: 0.460 USD/kWh) for El potrero, and USD 146,583 (COE: 0.504 USD/kWh) for Silicucho. Furthermore, employing the optimal configurations a renewable fraction (with respect to the total generation) of 94% is obtained for Campo serio and Silicucho, while the achieved renewable fraction for El potrero is 97%. Moreover, for the case of Campo serio, the resulting CO2 emission of the obtained optimal system is determined to be 6.1% of that of a diesel-only unit, while the latter ratio is determined to be 2.7% for El potrero and 9.9% for that of Silicucho. The optimal configurations that are obtained and presented in the present paper can be utilized as guideline for designing electrification systems (with a minimized cost) for the considered communities and other villages with similar characteristics (population and climatic conditions).
Graphic abstract
The current work compares the feasibility of using a non-renewable system, a standalone renewable system, and a hybrid renewable system to power up a remote community in Malaysian Borneo. The analysis shows that both the photovoltaic (PV) and hydrokinetic systems can be used to generate renewable electricity, either as a standalone or a hybrid system. Specifically, using a non-renewable system (50 kW standalone diesel system) based on a conventionally high diesel price ($ 1.482/L) resulted in a high net present cost (NPC) of $ 1.788 million. In contrast, a standalone renewable system, i.e., a 280 kW standalone PV system, resulted in a lower NPC ($ 1.615 million) than the standalone diesel system, and it can cater for highly fluctuated solar output with 100% renewables generation. Alternatively, the use of a hybrid PV/hydrokinetic system with a 100 kW PV, 60 kW hydrokinetic turbines, and an 85 kW converter was both economically and technically feasible (with $ 1.714 million NPC), with low water speed. Meanwhile, the use of a hybrid PV/diesel system with 60 kW PV, a 50 kW converter, 120 batteries, and a backup diesel generator could effectively reduce the dependence of electricity generation on diesel supply and resulted in the lowest NPC ($ 1.129 million) among all the analyzed system types. Significantly, the current work demonstrates that the use of PV and hydrokinetic renewable sources of energy in Malaysian Borneo is feasible and deserves more attention to electrify remote communities in Malaysian Borneo.
In Nigeria, some economically important facilities are not functioning optimally due to lack of/inadequate electricity from the national grid. To solve this problem, these facilities result to using diesel generators which are mostly uneconomical and environmentally unfriendly. Improving comparative economic advantage means that Renewable Energy Sources (RES) with reduced emission and long term cost of energy is a viable alternative. This work describes the potentials of using solar PV/biogas power system to supply the slaughterhouse located in Ado Ekiti, South West Nigeria through an optimal design and techno-economic analysis. With an annual average daily radiation of 4.93 kWh/m2/d, the facility slaughters an average of 25 cows daily to yield a biomass supply of about 1150 kg/day. Simulation results from HOMER software present an optimal PV/biogas generator/battery/converter system that is able to supply the 164 kWh daily load requirement of the facility. The PV system supplied 38% of the annual total electricity production which stood at 76,384 kWh/yr. Cost analysis also indicates that the system has levelized cost of energy of $ 0.236/kWh and a Net Present Cost (NPC) of $ 92,988. 60% of this cost is shared equally between the PV and battery storage system while the biogas generator and digester and converter cost make up 25% and 15% respectively.
This paper investigates renewable energy resource potential study, feasibility analysis and existing grid comparison of solar photo voltaic, biogas, and biodiesel hybrid electricity supply system for a rural community. HOMER is used as a modeling and analyzing tool. Electrical primary loads for the community were estimated and forecasted for the project lifetime. The resource potential of solar, biogas and biodiesel feedstock are studied and prepared for simulation. The common biogas feedstock considered were animal slurry, human feces and jatropha byproducts where as the biodiesel is considered from jatropha seed. In addition to the cost of equipments, the hybrid system power distribution cost was also considered. Grid comparison against the hybrid system was done to answer which alternative was economical. The optimization result of the simulation demonstrates that the best optimal hybrid system consists of solar photo voltaic, biogas generator, biodiesel generator, converter and battery under load following system control strategy. The best optimal hybrid system has initial capital cost $116,197, net present cost of $273,887, levelized cost of energy of 0.175$/kWh. Based on the data obtained from universal electricity access program of Ethiopia, the total capital cost of grid extension was estimated as $140,892 and its operation and maintenance cost is 235$/km/yr.
In recent years, the concept of hybrid energy systems (HESs) is drawing more attention for electrification of isolated or energy-deficient areas. When optimally designed, HESs prove to be more reliable and economical than single energy source systems. This study examines the feasibility of a combined dispatch (CD) control strategy for a photovoltaic (PV)/diesel/battery HES by combining the load following (LF) strategy and cycle charging (CC) strategy. HOMER software is used as a tool for optimization analysis by investigating the techno-economic and environmental performance of the proposed system under the LF strategy, CC strategy, and combined dispatch CD strategy. The simulation results reveal that the CD strategy has a net present cost (NPC) and cost of energy (COE) values of $110,191 and $0.21/kWh, which are 20.6% and 4.8% lower than those of systems utilizing the LF and CC strategies, respectively. From an environmental point of view, the CD strategy also offers the best performance, with CO2 emissions of 27,678 kg/year. Moreover, the results show that variations in critical parameters, such as battery minimum state of charge, time step, solar radiation, diesel price, and load growth, exert considerable effects on the performance of the proposed system.
One of the universal targets of the United Nations Sustainable Development Goals is affordable and clean energy. It is on this premise that this study presents the integration of PV-wind distributed generation system into an existing diesel generator powered water treatment plant in a suburban town of Wudil, Nigeria. Inadequate and epileptic supply from the grid caused the dependence of the plant on the generator. The optimal design was determined using the Hybrid Optimization of Multiple Energy Resources (HOMER) software developed by the National Renewable Energy Laboratory. Simulation results produce an optimal hybrid system which includes photovoltaic (PV) panels, wind turbines, converter, batteries and a generator with a cost of energy of $0.26 at a renewable fraction of 95%. An analysis also demonstrates that implementing this design will result in low and fairly constant fuel price in the lifecycle of the project. This will, in turn, support sustainable economic development of communities served by the water treatment plant.
The economic growth and demographic progression in Saudi Arabia increased spending on the development of conventional power plants to meet the national energy demand. The conventional generation and continued use of fossil fuels as the main source of electricity will raise the operational environmental impact of electricity generation. Therefore, using different renewable energy sources might be a solution to this issue. In this study, a grid-connected solar PV-wind hybrid energy system has been designed considering an average community load demand of 15,000 kWh/day and a peak load of 2395 kW. HOMER software is used to assess the potential of renewable energy resources and perform the technical and economic analyses of the grid-connected hybrid system. The meteorological data was collected from the Renewable Resources Atlas developed by the King Abdullah City of Atomic and Renewable Energy (KACARE). Four different cities in the Kingdom of Saudi Arabia, namely, the cities of Riyadh, Hafar Albatin, Sharurah, and Yanbu were selected to do the analyses. The simulation results show that the proposed system is economically and environmentally feasible at Yanbu city. The system at this city has the lowest net present cost (NPC) and levelized the cost of energy (LCOE), highest total energy that can be sold to the grid, as well as the lowest CO2 emissions due to a highly renewable energy penetration. This grid-connected hybrid system with the proposed configuration is applicable for similar meteorological and environmental conditions in the region, and around the world. Reduction of some greenhouse gasses as well as the reduction of energy costs are main contributors of this research.
In Nigeria, access to reliable and stable supply of electricity is a major challenge for both the urban and rural dwellers. In this study, comprehensive review of accessibility to clean and modern energy in Nigeria has been carried out. Also, this paper examines the potential of renewable energy (RE) resources in Nigeria that can be harnessed for continuous energy supply and the government’s efforts to ensure RE‘s sustainability. Nigeria is endowed with abundant energy resources but the existing electric energy infrastructures are unable to meet the energy demands of teeming population. There is imbalance in energy supply and demand in the country. Over the period from 2000 to 2014, there was an average of about 2.35 billion kWh of energy gap between energy production and energy consumption. The highest electricity consumption per capita recorded so far was 156 kWh in 2012. This makes Nigeria one of the country with the lowest electricity consumption on per capita basis in the world. In order to improve access to clean energy supply and achieve sustainable development, this paper pin points the significance of decentralized renewable energy systems and needs for the government to review the policies on renewable energy development in the country.
Abstract: Lack of access to energy is considered as a serious bottleneck for the socio-economic development of Bangladesh. Despite earning recognition for promoting solar home systems, most of the rural areas and remote islands of the country still remain non-electrified due to very high unit cost and low quality of electricity from solar home systems (SHS) coupled with only few hours of restricted usages in the evening. Considering the resource potential and demand characteristics at the local level, the present study investigates the hybrid renewable mini-grid approach as a possible solution for universal electricity access in the country. Using Hybrid Optimisation of Multiple Energy Resources (HOMER) simulation model, the study, covering the whole coastal region of Bangladesh, shows that it is possible to offer a much better quality electricity for 12 h to 18 h a day for as low as USD 0.29–USD 0.31/kWh. Hybrid models suggested in this study can be replicated along the coastal belt and remote islands to obtain maximum diffusion of this technology and hence universal electrification.
The Hybrid renewable energy system (HRES) has the potential to better match the demand load profile with power by using the complementary nature of the variable renewables. The sizing of the HRES should be done carefully to better match with demand load without oversizing and under-sizing. This study presents the use of the Generalized Reduced Gradient Method to optimize the size of components of HRES. The case study is performed to demonstrate the HRES for a remote rural region. Cases of both the standalone and grid-connected modes are explored. The standalone system with reliability from 100% up to 70% is investigated. A grid-connected system is studied with and without payment of power supplied to the grid to explore the feasibility of HRES for different price regimes. The methodology used is validated using HOMER software by comparing its results with HOMER results for the cases considered. Higher renewable share in the standalone systems leads to more need for employments at every stage of the lifecycle of components. In addition to that, the negative environmental impact of the HRES system in comparison to the conventional system is significantly less. It can be concluded that the standalone system proves to be better in terms of job creation and carbon emission. In contrast, grid-connected comes out to be better in terms of reliability and economics.
A novel optimized sizing and management strategy of a grid-connected hybrid photovoltaic (PV)-solar-battery- group system were proposed for the electrification of residential consumers in Northwest Africa (a case of Mauritania), and the influence of the state of the sky (clear, moderately overcast, and overcast) was analyzed according to the load flowing (LF) and the cycle charging (CC) strategies. In order to mitigate the pressure on the national grid, consolidate the consumer autonomy, minimize the cost of medium- and long-term consumption bills, and CO2-related emissions, a cartographic approach was conducted as the first attempt to map the elec-tricity consumption potential for buildings in the city of Nouakchott (Mauritania) using a geo-referenced data-base. ArcGIS®, HOMER Pro®, and MATLAB® softwares were used for the establishment of the load profile, optimized sizing of the PV-batteries-group-grid system, and calculation of the lightness index, respectively. The LF strategy provided the best monitoring of the load throughout the day by minimizing the generator uptime. The techno-economic analysis revealed the values of cost of energy (COE) and net present cost (NPC) as follows: COE =$0.0549/kWh and NPC =$24,796 for the LF PV-batteries-grid strategy, COE =0.0646 $/kWh and NPC =$23,380 for the CC PV-batteries-grid strategy, and COE =$0.17/kWh and NPC =$23,262 for the case of the grid on its own.
This study presents a hybrid Solar PV/Diesel/Biogas backup solution for unreliable grid electricity using the central abattoir at Ado Ekiti in South-West Nigeria as a case study. The availability of solar resource and potential of biogas production from anaerobic digestion of slaughtered cattle paunch manure is proposed. This is to complement an existing backup diesel generator system. Using HOMER® software, the optimal hybrid combination of these three-arrangement generated two viable solutions comprising of a Grid/PV/Biogas and Grid/PV/Diesel system. Techno-economic analysis of the former case showed that a 10kW PV and 20kW Biogas generator can provide backup for the unreliable grid at a COE of $0.164/kWh, NPC of $67,616 and initial capital of $42,705. Furthermore, the latter case which included a 40kW PV and 30kW diesel generator accrued an initial capital cost of $75,994, NPC of $115,355 and COE of $0.280/kWh. This shows that the existing backup diesel generator within the abattoir will not reduce the associated cost implications. In addition, comparative analysis reveals the Grid/PV/Biogas system reduced emissions by 61% when compared with Grid/PV/Diesel system. The proposed backup solution for unreliable grid can be useful in planning similar infrastructures around the world especially for developing countries.
This paper presents a methodology for optimal design of diesel/PV/wind/battery hybrid renewable energy system (HRES) for the electrification of residential buildings in rural areas. Contrary to previous work, in this study, the effects of climate diversity and building energy efficiency on the size optimization of HRES are investigated. First, a multi-criteria spatial analysis trough a common geographical information system tool (ArcGIS 10.2) is undertaken to develop the renewable energy potential map for Algeria. Then, particle swarm optimization algorithm and ε-constraint method were used to solve the multi-objective problem, which was formulated to minimize the cost of energy (COE) as the primary objective, while maximizing system reliability and a renewable fraction (RF). According to the resulting renewable potential map, seven zones are identified, and then seven locations have been selected (one from each zone) to execute the optimization of the proposed HRES. By considering low efficient buildings, photovoltaic/wind/diesel/battery is found the best configuration for Adrar and Tindouf, while photovoltaic/diesel/battery is obtained the best for the other locations. However, in the case of high-performance buildings, another optimal HRES configurations are obtained. The better one is acquired in Biskra and Tamenrast, which includes PV-Battery (100 % renewable energy) and fulfilling COE of 0.21 $/kWh.
A large population of India is living in villages, some of them are living in remote areas isolated from the grid. It is not feasible or economical to extend the grid connection to provide electricity for those villages, but an autonomous integrated hybrid renewable energy system can be a viable option. This study focused on emerging a grid-independent integrated hybrid renewable energy system (IHRES) to provide electricity and freshwater availability for a cluster of un-electrified villages located at Odisha state in India. In order to provide a continuous power supply, the study focused on three different types of battery technologies, such as Lead-Acid (LA), Lithium-Ion (Li-Ion) and Nickel-Iron (Ni-Fe). To obtain an optimal IHRES configuration, twelve different IHRES configurations are modelled using nine metaheuristic algorithms in the MATLAB© environment. From the results, it is found that the Ni-Fe battery-based IHRES results in a minimum Annual Levelized Cost (ALC) as $66,650 and Levelized Cost of Energy (LCOE) as 0.21779 $/kWh when compared to other battery-based IHRESs. The proposed Salp Swarm Algorithm (SSA) has proven its robustness and convergence efficiency by providing the optimal ALC and LCOEs with fast convergence to the global best optimal solutions. Further, the proposed system has been examined at a different maximum allowable loss of power supply probability (LPSP*) values. Finally, the sensitivity analysis has been conducted with the variable input parameters, such as interest rate, biomass collection rate and cost of biomass. It is found that the variation in interest rate affects the system performance significantly.
The present work analyses the techno-economic feasibility of an autonomous hybrid renewable energy system for providing electricity for an academic township in the East District of Sikkim, India. The resources considered for the system were solar energy, wind energy, biogas, syngas and hydrokinetic energy with batteries as back-up. HOMER Pro Microgrid Tool, developed by the National Renewable Energy Laboratory, United States of America has been used as the simulation and assessment tool for modeling performed with hourly data input. Various constraints were implemented to limit the maximum installation capacities of the components considered. All the technical and financial specifications of the components were availed from the local Indian markets. A total of 31 possible combinations of the different resources were analyzed for net present cost, Levelized cost of energy, battery storage, emissions, area requirements and employment potential. The best combination was identified by applying a very widespread multi-criteria decision-making technique named Analytical Hierarchy Process. The Photovoltaic-Wind-Biogas-Syngas-Hydrokinetic-Battery based Hybrid Renewable Energy System was found to be the best combination with a Levelized Cost of Energy of 0.095 $/kWh. Finally, sensitivity analysis was carried out for various parameters to comprehend the behavior of the system for a broader application in the region.
Despite the remarkable potential for biogas production from livestock and organic wastes, the number of constructed biogas digesters for the continent is in the order of thousands and in case of Mauritania is lower than the number of the provinces. While majority of the existing digesters left far behind the expected efficiency, lack of a comprehensive economic assessment along with an efficient design questions their practical application. The present study introduced the first assessment to evaluate the biogas potential from livestock manures and waste from slaughterhouses in Northwest Africa (a case of Mauritania). Using ArcGIS® software, a database was conducted to build maps that show the amount of waste products, the potential of biogas, and equivalent amounts of energy. These were used to assess the potential of biogas and the corresponding potential energy for each geographical department in Mauritania. The results indicated that the southern provinces had the highest biogas potential with the maximum and the average values of 520 and 258.7 (± 125.8) × 106 m3/year. On the other hand, the lowest biogas production potential (27.7 × 106 m3/year) was recorded for northern provinces with the maximum and the average values of 135 and 76.4 (± 39.7) × 106 m3/year. The results showed that 63,579 × 106 kg of waste associated with livestock (cattle) and slaughterhouse applications were annually produced in the country. It was determined that this quantity could generate 2451 × 106 m3 of biogas per year, corresponding to an energy potential of 52,704 × 106 MJ/year. Considering the rapid depletion of conventional energy sources and the significance of biogas as a renewable fuel, a detailed feasibility analysis (for the biogas production in each province of Mauritania by means of community type fixed-dome digesters) was also performed in the scope of this study. The results of the comprehensive cost breakdown analysis revealed that the revenues obtained from sale of biogas-generated electricity and digested slurry (as fertilizer) could able to pay the initial investment within approximately 6.5 years without subsidy. The findings of this study, as the first of its own, could be used to comprehend how utilization of information such as slaughterhouse and livestock population, nutrition habitats, land-usage maps and geographic information system (GIS) can be employed to germinate a model for more comprehensive assessment of biogas production potential from livestock manure and slaughterhouse wastes, specifically in case of northern African countries. Moreover, in case of biogas plant, this model could be employed as a decision-making tool to identify the highly qualified location for construction of the biogas plant.
Amid all renewable energies, solar PV is of particular interest, mainly in Africa. Mauritania is an example of African countries which, gives great concern to produce electricity via PV installations. This study is carried out on the performance evaluation of a 954,809 kWp photovoltaic array made up of micro-amorphous silicon situated in Nouakchott (capital of Mauritania) at Sheikh Zayed solar power plant. The measures of one year of operation from September 2014 to August 2015 were evaluated according to the IEC 61724. The results obtained demonstrate that the photovoltaic array performances depend on both insolation and environmental conditions. The array capture loss ranges vary from a minimum value of 1.63 h/day to a maximum value of 2.46 h/day. So, the system loss is relatively stable, with an average value of 0.12 h per day. The monthly performance ratio varies from 0.61% in August to 0.71% in November, with a monthly average value of 0.66%. The monthly average capacity factor achieves its maximum and minimum in October (20.54%) and January (11.66%), respectively. The energy generated by the PV array (Edc) and the energy fed to the utility grid (Eac) during November moth, are affected by the insolation and the module temperature. However, wind speed variation does not influence those energies. Two linear models, depending on insolation and module temperature, are proposed for the evaluation of Edc and Eac during this month. These laters present a coefficient of determination (R²) of 0.96.
This paper validates the optimal design and techno-economic feasibility of hybrid renewable energy system (HRES) for rural area electrifying applications. Plan to a design of improved performance electrification system through village owned renewable resources, such as solar irradiations, wind speed and bio mass etc. The selected HRE system has to meet out electrical needs in optimum performance manner. Hear conducted a case study on remote village Korkadu is located in Union Territory of Pondicherry, India. The expected village demand of 179.32 Kwh/day and peak of 19.56 Kw was met with proposed HRE structure, which is consists of solar PV array, wind turbine, Bio mass power generator and Battery backup system in effectively. Load growth of the village was predicted through artificial neural network (ANN-BP) feed-back propagation and Levenberg-Marguardt (LM) data training optimum technique. Encounter the optimum performance of different HRE configuration was evaluated over by HOMER software. System’s economic dispatch was analysed through various dispatch strategy and come across the proposing companied dispatch strategy has more economical and performance benefits as total NPC of system as INR 1.21 million, one unit energy generation cost as INR 13.71 and annual battery throughput as 36.648 KWh/yr. This study also expresses the comparison analysis between proposed HRES structure performance with basic utility grid extension. The consequence of the proposed work shows the HRES in remote location can be a cost effective solution for sustainable development of rural regions.
Providing power to rural communities, which are far from the grid and suffer from lack of energy access in Africa, especially in Benin, in a sustainable manner requires the adoption of appropriate technology. This paper aims at analysing the techno-economic feasibility of hybrid renewable energy system (HRES) for sustainable rural electrification in Benin, using a case study of Fouay village. HOMER software is used to perform optimization, simulation and sensitivity analysis. The analysis showed that hybrid solar photovoltaics (PV)/diesel generator (DG)/battery (of 150 kW/62.5 kVA/637 kWh) is the least cost optimal system. This system ensures a reliable power supply, reduces battery requirements by 70% compared to PV/battery system and achieves 97% CO2 emissions reduction compared to a conventional DG. Moreover, the study demonstrated that the most economical HRES depends strongly on the potential energy sources available at a location and power plant's remoteness from the beneficiary. In summary, as solar radiation is an abundant resource across the country, this hybrid PV/DG/battery system can be a suitable model to power remote areas in Benin, and we recommend it for future electrification projects in the country in place of the current widely deployed PV/battery system.
In this paper, a hybrid genetic algorithm with particle swarm optimization (GA-PSO) is applied for the optimal sizing of an off-grid house with photovoltaic panels, wind turbines, and battery. The GA-PSO is one of the most powerful single-objective optimization algorithms. In the other hand, the multi-objective PSO (MOPSO) can solve the optimization problems considering all objectives without transforming them. Minimizing the total present cost including initial cost, operation and maintenance cost, and replacement cost with satisfying the load demand is the main goal of this study. In this optimization problem, the considered reliability factor is a loss of power supply probability, which specifies the subtraction of the load power and generated power. The wind velocity, solar irradiance, and load demand are simulated in 12 months of a year by the HOMER software for a suburbs of Tehran. Then, the optimal size of PV and WT are obtained with both GA-PSO and MOPSO methods, and compared with the HOMER results. At last, the strengths and weaknesses of each method are explained. The results show that the proposed approach with 0.502 of the levelized cost of energy for the PV/WT/BAT system has the best result through the compared methods.
This research contributes to the ongoing discussions about the grid-connected solar photovoltaic (PV) systems and draws attention to the optimal design by considering various PV array tracking systems towards enhancing the power generation. The PV tracking system configurations considered in this study include horizontal-axis (monthly adjustment, weekly adjustment, daily adjustment, continuous adjustment), vertical-axis (continuous adjustment), and a two-axis tracking system. HOMER (Hybrid Optimization of Multiple Energy Resources) software is employed whereas the actual data required by the model have been collected in Makkah, Saudi Arabia. The results show that the two-axis tracker can produce 34% more power than the fixed system, while the vertical axis tracker with continuous adjustment was able to generate up to 20% more power than the fixed system. Horizontal tracker with continuous adjustment shows the highest net present cost (NPC) and the highest levelized cost of energy (LCOE), with a high penetration of solar energy to the grid. For the case of Makkah, the vertical axis tracker with continuous adjustment is the best option as it has low LCOE and NPC values with a positive return on investment (ROI) as well as high renewable energy penetration to the grid, which enhances its viability for a utility-size solar PV grid-connected system.
Most research published into stand-alone energy systems, hybridised by supplementing PV with combustion-based prime movers, considers meeting an electric load demand. This paper goes further by studying the role of both electric and heating loads on the optimisation of hybridised stand-alone Combined Heating and Power (CHP) systems. The role of both the load following strategy in these systems (electric only FEL, versus electric and thermal FEL/FTL) as well as the relative magnitude of the heating load is analysed on system cost and performance. The conceptual CHP systems modelled also consider waste system derived from either multiple Internal Combustion Engines (ICEs) or Micro Gas Turbines (MGTs). The research uses MATLAB-based Genetic Algorithm (GA) optimisation throughout and features detailed hardware characteristics as well as temporally fluctuating meteorological (solar irradiance, temperature) and load (electric, heating) data. The outcomes are also tested in relation to CHP systems sized whilst optimising either single (Cost of Energy-COE, $/kW h) or multiple functions (COE and overall system efficiency, ηCHP,%).
Results indicate that whilst the power management strategy used in CHP systems (FEL or FEL/FTL) has minimal effects on the COE, it can appreciably affect other performance indicators. For example, in CHP systems sized based on FEL/FTL, whilst COE = ∼0.20 $/kW h the resulting ηCHP is 66% for PV/Bat/ICE and 44% for PV/Bat/MGT. This is compared to using a PMS of the FEL type which results in similar COE = ∼0.21 $/kW h but with ηCHP = 50% in PV/Bat/ICE systems and 34% in PV/Bat/MGT. In relation to overall environmental impact expressed though Life Cycle Emission-LCE (kg CO2-eq/yr) when heating demand is around 50% of the electric (Electric to Thermal Load Ratio = 60:40), a PMS of the FEL/FTL results in up to 30% lower LCE compared to those with FEL in some CHP systems.
Mauritania faces multiples problems related to the access to electricity, especially in rural areas, whose coverage is uneven and inadequate. This review presents the energy context in Mauritania. The energy situation of the country (energy policy and development of renewable energy) was discussed in the first part, then, energy resources (fossil and renewable) and their applications are processed in the second section. Finally, we propose in the last section (conclusion) some recommendations for Mauritanian government concerning energy policy of the country and its planning.
This paper presents a feasibility study of stand-alone solar photovoltaic (PV) systems for the electrification of three residential case study buildings (T4, T5 and T6) in the capital city of Yaoundé, Cameroon. The system was sized taking into account the load of the buildings and the available energy from the sun. The power, area of PV modules and daily energy generated by the PV for T4, T5 and T6 were respectively determined as: 2103 W, 14 m² and 9.8 kW h/day; 3779 W, 25.2 m² and 17.6 kW h/day; and 2766 W, 18.4 m² and 12.9 kW h/day. The battery bank capacity, size of inverter and controller were respectively obtained as: 40,323 W h, 635 W and 93 A for T4; 72,433 W h, 795 W and 156 A for T5; and 53,017 W h, 826 W and 114 A for T6. The life cycle cost and annualized life cycle cost (ALCC) of the systems were respectively found to be: €15,714 and €1039 for T4; €27,227and €1800 for T5; and €20,006 and €1322 for T6. The average unit electricity cost for T4, T5 and T6 was respectively determined to be €0.52 kW h⁻¹, €0.50 kW h⁻¹ and €0.51 kW h⁻¹, higher than the unit cost of residential grid electricity in Cameroon.
This paper presents the optimal cost analysis of wind-solar hybrid systems connected to DC and AC irrigation pumps. HOMER software is used for optimizing the systems components based on load profiles and wind-solar energy potentials at the Bagalkot, India. AC load profile is considered constant for seven hours/day and DC load profile is obtained by conducting performance tests on 1 HP DC pump installed in Energy Park, Basaveshwar Engineering College (Autonomous), Bagalkot, India. Developed HOMER model include SPV panels and two DC wind turbine generators for generation. Optimal configurations of wind-solar capacities are listed by considering Total Net Present Cost as objective function. Cost and electricity generation are compared and analyzed. It is observed that, annual electricity generated by both systems is nearly equal. However, cost comparison of AC and DC loads indicate that, for renewable energy powered small scale irrigation systems, AC pumps leads to uneconomic results and excess generation. On other hand, DC pumps prove to be economic and reliable.
This paper proposes a feasibility analysis of grid connected photovoltaic energy systems in Algerian dairy farms considering technical and economic requirements and respecting the local specific characteristics and legislations. The aim is to design an optimal solar system satisfying the farms' electric needs for each Algerian region and investigate the feasibility as well as the impact of replacing the existing conventional systems with solar energy systems. Real electricity consumption data from experimental dairy farms are recorded using typical herd size for each region and projected herd size according to the livestock intensification policy followed by the government. The pilot farms are determined to be the farms of the technical institute of breeding ITELV. The electricity consumptions of a set of Algerian family farms, ranging from 10 to 30 milking cows, were analyzed. It is found that the average energy requirements are between 330 kWh/cow/year and 560 kWh/cow/year, which is considerably lower than north European and North American dairy farms consuming up to 2900 kWh/cow/year. The results indicate that the on-farm self-produced electricity is able to achieve the energy balance between forecasted photovoltaic generation and farm energy demand with a cost of electricity ranging from −0.008 $/kWh to 0.033 $/kWh.
Anaerobic digestion of renewable feedstocks has been known as a prospective technology for the production of clean energy in the form of biogas. Biogas is a sustainable energy carrier which is mainly composed of methane (60%) and carbon dioxide (35–40%). Among the raw substances, organic matters obtained from farm animal waste are pivotal sources for biogas production. In recent years, the number of animal husbandry has drastically grown in Malaysia. Accordingly, a large amount of animal waste including manure, blood and rumen content are produced which provide a tremendous source of biogas generation. This paper presents biogas potential from the organic waste obtained from the farm animals and slaughterhouses in Malaysia. The findings of this study indicated that biogas potential of 4589.49 million m3 year−1 could be produced from animal waste in Malaysia in 2012 which could provide an electricity generation of 8.27×109 kWh year−1.
In this study, a hybrid power system consisting of PV (Photovoltaics) panels, a wind turbine and a biogas engine is proposed to supply the electricity demand of a village in Kenya. The average and the peak load of the village are around 8 kW and 16.5 kW respectively.
The feasibility of using locally produced biogas to drive a backup engine in comparison to using a diesel engine as backup has been explored through a techno-economic analysis using HOMER (Hybrid Optimization Model for Electric Renewables). This hybrid system has also been compared with a single diesel based power system.
The results show that the hybrid system integrated with the biogas engine as backup can be a better solution than using a diesel engine as backup. The share of power generation by PV, wind and biogas are 49%, 19% and 32%, respectively. The LCOE (Levelized Cost of Electricity) of generated electricity by this hybrid system ($0.25/kWh) is about 20% cheaper than that with a diesel engine as backup ($0.31/kWh), while the capital cost and the total NPC (Net Present Cost) are about 30% and 18% lower, respectively.
Regarding CO2 emissions, using a biogas engine as backup saves 17 tons of CO2 per year compared to using the diesel engine as backup.
Implementation of power sector reforms in Africa picked up speed in the 1990s. These reforms are driven largely by governments' need for development loans available from international financing institutions only upon commitment to reform. The main model advocated has been commercialisation followed by privatisation on the basis that the private sector is more efficient than the government. Reform promises better services, jobs, competition and lower tariffs. However, emerging lessons indicate cause for concern. Competition has hardly come into place. Instead there are shifts from government-owned monopoly utilities to foreign-controlled companies, some of which are in reality foreign-government monopolies. This has energy security implications. Financial instability suffered by many of these companies is placing these already economically unstable and vulnerable countries on a riskier path than before reform. The old utilities have not been particularly attractive to the private sector. This is mainly due to the small market sizes available since electrification rates are rather low. This has led to transfers of the utilities at unfavourable prices and conditions for the host governments. The socio-economic status related to the power sector has worsened as many employees are retrenched, tariffs rise and the majority of the population remains unconnected. A review of the reform process to integrate social and developmental needs is vital.
It is not cost effective or feasible to extend a centralized power grid to islands and other isolated communities. Decentralized renewable energy sources are alternatives. Among these alternatives are hybrid photovoltaic systems which combine solar photovoltaic energy with other renewable energy sources like wind. A diesel backup system can be used when PV system fails to satisfy the load and when the battery storage is depleted. If the hybrid systems are optimized, these would be cost effective and more reliable.
a b s t r a c t Today, there are 1.4 billion people around the world that lack access to electricity, some 85% of them in rural areas. Without additional dedicated policies, by 2030 the number of people drops, but only to 1.2 billion. Some 15% of the world's population still lack access, the majority of them living in Sub-Saharan Africa. The number of people relying on the traditional use of biomass is projected to rise from 2.7 billion today to 2.8 billion in 2030. Addressing these inequities depends upon international recognition that the projected situation is intolerable, a commitment to effect the necessary change, and setting targets and indicators to monitor progress. A new financial, institutional and technological framework is required, as is capacity building in order to dramatically scale up access to modern energy services at the local and regional levels. In this paper, we discussed the energy situation of the developing countries for sustainable development.
We integrated findings from 35 recent, longitudinal studies of the onset of heterosexual intercourse. Correlates of adolescent sexual intercourse onset, whether in early (before age 16) or middle (ages 16–18) adolescence, included living with other than two biological parents, being less monitored by parents, having more advanced physical maturity and more involvement in dating behavior, and having more permissive attitudes toward sex. When studies were organized by age of participants, the onset of intercourse was more strongly associated with alcohol use, delinquency, school problems and (for girls) depressive symptoms in Early studies (sexual intercourse by age 15 or before only) than was found in studies classified as Middle (assessment of sexual intercourse up to age 18) or Late (knowledge of those who delayed until after age 18). Although more research is needed, additional factors were associated with delaying first sexual intercourse until after age 18, including religious attitudes and anxiety, with some factors more relevant for girls and some more applicable to boys. In total, the evidence suggests there are many similarities, but also some important differences, in the correlates associated with early versus middle versus later onset of sexual intercourse. This seems to signify more than one pathway (set of distal and proximal correlates) associated with sexual behavior during adolescence that should be tested in future research. Throughout the review, we highlight differences in the correlates of girls’ versus boys’ sexual intercourse and how race/ethnicity moderates associations. These gender and racial/ethnic differences were found largely in analyses of family processes, school and religion, and parent education. We end by summarizing several priority areas for future research.
In an earlier paper (Kosnik, 2008), the potential for small scale hydropower to contribute to US renewable energy supplies, as well as reduce current carbon emissions, was investigated. It was discovered that thousands of viable sites capable of producing significant amounts of hydroelectric power were available throughout the United States. The primary objective of this paper is to determine the cost-effectiveness of developing these small scale hydropower sites. Just because a site has the necessary topographical features to allow small scale hydropower development, does not mean that it should be pursued from a cost-benefit perspective, even if it is a renewable energy resource with minimal effects on the environment. This analysis finds that while the average cost of developing small scale hydropower is relatively high, there still remain hundreds of sites on the low end of the cost scale that are cost-effective to develop right now.
Hybrid energy system is an excellent solution for electrification of remote rural areas where the grid extension is difficult and not economical. Such system incorporates a combination of one or several renewable energy sources such as solar photovoltaic, wind energy, micro-hydro and may be conventional generators for backup. This paper discusses different system components of hybrid energy system and develops a general model to find an optimal combination of energy components for a typical rural community minimizing the life cycle cost.The developed model will help in sizing hybrid energy system hardware and in selecting the operating options. Micro-hydro-wind systems are found to be the optimal combination for the electrification of the rural villages in Western Ghats (Kerala) India, based on the case study. The optimal operation shows a unit cost of Rs. 6.5/kW h with the selected hybrid energy system with 100% renewable energy contribution eliminating the need for conventional diesel generator.
High crude oil prices and pollution problems have drawn attention to alternative vehicle technologies and fuels for the transportation sector. The question is: What are the benefits/costs of these technologies for society? To answer this question in a quantitative way, a web-based model (http://vehiclesandfuels.memebot.com) has been developed to calculate the societal life cycle costs, the consumer life cycle costs and the tax for different vehicle technologies. By comparing these costs it is possible to draw conclusions about the social benefit and the related tax structure. The model should help to guide decisions toward optimality, which refers to maximum social benefit. The model was applied to the case of Thailand. The life cycle cost of 13 different alternative vehicle technologies in Thailand have been calculated and the tax structure analyzed.
Seasonal analyses of solar radiation on flat ground for different stat of sky: Case of Nouakchott, Mauritania
- J A Eslemhoum
J. A. Eslemhoum, et al., "Seasonal analyses of solar radiation on flat ground for different stat of sky: Case of Nouakchott,
Mauritania," Int. J. Phys. Sci., vol. 14, no. 12, pp. 125-138, 2019.