Electrification using solar photovoltaic systems in Nepal

Historically, the rural population of Nepal has been meeting their energy needs from traditional sources like fuel wood and other biomass resources. Only about 44% of the total population has access to grid electricity. Because of country’s rough and mountainous topography, high cost of grid extension, and low and scattered population density, constructing some big power plants (e.g. large hydropower) can not meet the electricity needs of all people, especially those living in rural areas. Distributed generation of electricity, using environment friendly solar photovoltaic (PV) systems, might be one of the reliable alternatives for urban as well as rural electrification. This article begins with a general overview of energy resources in Nepal. Present status and perspectives of solar PV sector have also been discussed. Benefit cost and breakeven analyses of solar PV systems in Nepalese urban areas have been carried out. The breakeven year has been calculated between 2027 and 2036 for PV systems with system life time between 40 and 25 years, respectively. It has been concluded that the solar PV systems are not the economic solutions for grid connected urban areas in Nepal. On the other hand, this article concludes that the rural electrification projects should not be decided on the basis of mere monetary benefits, rather many social aspects should be considered, and in this case, there are not convincing alternatives to solar PV systems for electrification in many rural villages in Nepal.     

Hydrogen vector for using PV energy obtained at Esperanza Base,Antarctica

The use of solar photovoltaic (PV) is universally considered valuable for its renewable and clean nature; solar energy is especially important in regions far from urban centers and power distribution networks. It is known that the loss due to the latitude and the atmospheric layer is partially offset in very different annual distribution (i.e., by the long summer days) and in sparsely populated areas, because of the clearer atmosphere. Even with these assumptions, low temperatures (snow often combined with strong winds) and the effects of seasonality are difficult obstacles for the proper use of solar PV energy at high latitudes.In this work, both analytical and experimental data of the solar resource at Esperanza Base, Antarctica, are presented. The PV modules were installed in a vertical configuration and NW–NE orientation, which not only maximizes performance but also mitigates the adverse effects due to the latitude. In order to overcome the very asymmetric annual irradiance distribution, the use of a system of hydrogen production and accumulation, is proposed for effective energy storage.The results of two years of evaluation of PV potential at Esperanza Base show that duplicating the PV capture area in Esperanza allows to obtain the same total annual energy than the maximum acquired in Buenos Aires (PV module facing north with optimum tilt for solar capture).To effectively overcome discontinuity of solar energy and its sharp drop in four of the twelve months of the year an appropriate hydrogen vector system is proposed and analyzed.     

太阳能光热与光电/光热系统在中国不同建筑气候带下的性能研究

文章利用TRNSYS动态模拟软件研究了在我国不同建筑气候带条件下,不同类型的太阳能PV/T集热系统和普通太阳能PT集热系统的各项性能。其中,太阳能PV/T集热系统分为基于普通玻璃型太阳能PV/T集热系统和基于Low-e型太阳能PV/T集热系统。文章探究了基于普通玻璃型太阳能PV/T集热系统和基于Low-e型太阳能PV/T集热系统的电、热性能,分析了这两种太阳能PV/T集热器的光电转化效率,以及这两种太阳能PV/T集热系统和普通太阳能PT集热系统的光热转化效率、太阳能贡献率、一次能源节约率、供热节能率和环境效益等参数。分析结果表明:普通太阳能PT集热系统的吸热量、太阳能贡献率、供热节能率和CO₂减排量均高于太阳能PV/T集热系统;与基于普通玻璃型太阳能PV/T集热系统相比,基于Low-e型太阳能PV/T集热系统的发电量降低了3.77%,但热效率、太阳能贡献率、一次能源节约率、供热节能率和环境友好度均较高。     

Practical application of building integrated photovoltaic (BIPV) system using transparent amorphous silicon thin-film PV module

An analysis has been carried out on the first practical application in Korea of the design and installation of building integrated photovoltaic (BIPV) modules on the windows covering the front side of a building by using transparent thin-film amorphous silicon solar cells. This analysis was performed through long-term monitoring of performance for 2 years. Electrical energy generation per unit power output was estimated through the 2 year monitoring of an actual BIPV system, which were 48.4 kWh/kWp/month and 580.5 kWh/kWp/year, respectively, while the measured energy generation data in this study were almost half of that reported from the existing data which were derived by general amorphous thin-film solar cell application. The reason is that the azimuth of the tested BIPV system in this study was inclined to 50° in the southwest and moreover, the self-shade caused by the projected building mass resulted in the further reduction of energy generation efficiency. From simulating influencing factors such as azimuth and shading, the measured energy generation efficiency in the tested condition can be improved up to 47% by changing the building location in terms of azimuth and shading, thus allowing better solar radiation for the PV module. Thus, from the real application of the BIPV system, the installation of a PV module associated with azimuth and shading can be said to be the essentially influencing factors on PV performance, and both factors can be useful design parameters in order to optimize a PV system for an architectural BIPV application.     

Integrating photovoltaic and power converter characteristics for energy extraction study of solar PV systems

Solar photovoltaic (PV) energy is becoming an increasingly important part of the world’s renewable energy. A grid-connected solar PV system consists of solar cells for energy extraction from the sun and power converters for grid interface. In order for effective integration of the solar PV systems with the electric power grid, this paper presents solar PV energy extraction and conversion study by combining the two characteristics together to examine various factors that may affect the design of solar PV systems. The energy extraction characteristics of solar PV cells are examined by considering several practical issues such as series and parallel connections, change of temperatures and irradiance levels, shading of sunlight, and bypassing and blocking diodes. The electrical characteristics of power converters are studied by considering physical system constraints such as rated current and converter linear modulation limits. Then, the two characteristics are analyzed in a joint environment. An open-loop transient simulation using SimPowerSystem is developed to validate the effectiveness of the characteristic study and to further inspect the solar PV system behavior in a transient environment. Extensive simulation study is conducted to investigate performance of solar PV arrays under different conditions.     

Domestic application of solar PV systems in Ireland: The reality of their economic viability

Renewable sources of energy are anticipated to play a major role in electricity generation in Ireland in the future. Currently, electricity is mainly generated from imported gas and coal due to a lack of indigenous fossil fuel resources in Ireland. Solar energy is omnipresent, freely available and environmental friendly. The utilisation of solar energy to produce electricity has become increasingly attractive worldwide. However, solar electricity generation has not been very popular in Ireland to-date either on a large scale or on a domestic scale. The unclear economics of domestic solar PV systems, under Irish conditions, is considered the biggest obstacle for expanding domestic solar PV system installation in Ireland. This paper presents a methodology to accurately evaluate the economic viability of a domestic solar PV system on a case-by-case basis. The methodology utilises the software programmes HOMER and Microsoft Excel 2007 for the energy and economic analyses. Utilising this methodology, a realistic economic analysis of eight sample domestic solar PV systems available in Ireland is presented. Based on the predictions, the domestic solar PV system is not economically viable under current conditions in Ireland. Domestic solar PV systems still do not look promising even if better financial support is given.     

Optimal operation of microgrid using hybrid differential evolution and harmony search algorithm

This paper proposes the generation scheduling approach for a microgrid comprised of conventional generators, wind energy generators, solar photovoltaic (PV) systems, battery storage, and electric vehicles. The electrical vehicles (EVs) play two different roles: as load demands during charging, and as storage units to supply energy to remaining load demands in the MG when they are plugged into the microgrid (MG). Wind and solar PV powers are intermittent in nature; hence by including the battery storage and EVs, the MG becomes more stable. Here, the total cost objective is minimized considering the cost of conventional generators, wind generators, solar PV systems and EVs. The proposed optimal scheduling problem is solved using the hybrid differential evolution and harmony search (hybrid DE-HS) algorithm including the wind energy generators and solar PV system along with the battery storage and EVs. Moreover, it requires the least investment.     

风光互补电动汽车储能电站系统优化设计

通过对唐山市区太阳能和风能资源状况调查分析,对全年不同方位角和倾角上的太阳能辐射量进行模拟计算,得出南偏东9.8°方向、倾角为39.7°的倾斜面上接收的太阳能辐射量最大,其值为1.62×106Wh/m2。研究中对3kW风力发电机和1kW光伏发电系统的发电量进行了计算,并以1辆纯电动轿车为负载进行了容量配比优化,设计了风力发电系统、风光互补系统及光伏系统三种不同的方案,经过对各方案的经济性、可靠性及稳定性分析,得出最佳的设计方案为风光互补发电系统,该系统风力发电装机容量为3kW,光伏发电装机容量为8.96kW。     

Thermodynamic assessment of photovoltaic systems

In this paper, an attempt is made to investigate the performance characteristics of a photovoltaic (PV) and photovoltaic-thermal (PV/T) system based on energy and exergy efficiencies, respectively. The PV system converts solar energy into DC electrical energy where as, the PV/T system also utilizes the thermal energy of the solar radiation along with electrical energy generation. Exergy efficiency for PV and PV/T systems is developed that is useful in studying the PV and PV/T performance and possible improvements. Exergy analysis is applied to a PV system and its components, in order to evaluate the exergy flow, losses and various efficiencies namely energy, exergy and power conversion efficiency. Energy efficiency of the system is calculated based on the first law of thermodynamics and the exergy efficiency, which incorporates the second law of thermodynamics and solar irradiation exergy values, is also calculated and found that the latter is lower for the electricity generation using the considered PV system. The values of “fill factor” are also determined for the system and the effect of the fill factor on the efficiencies is also evaluated. The experimental data for a typical day of March (27th March 2006) for New Delhi are used for the calculation of the energy and exergy efficiencies of the PV and PV/T systems. It is found that the energy efficiency varies from a minimum of 33% to a maximum of 45% respectively, the corresponding exergy efficiency (PV/T) varies from a minimum of 11.3% to a maximum of 16% and exergy efficiency (PV) varies from a minimum of 7.8% to a maximum of 13.8%, respectively.     

Industrial symbiosis of very large-scale photovoltaic manufacturing

In order to stabilize the global climate, the world's governments must make significant commitments to drastically reduce global greenhouse gas (GHG) emissions. One of the most promising methods of curbing GHG emissions is a world transition from fossil fuels to renewable sources of energy. Solar photovoltaic (PV) cells offer a technically sustainable solution to the projected enormous future energy demands. This article explores utilizing industrial symbiosis to obtain economies of scale and increased manufacturing efficiencies for solar PV cells in order for solar electricity to compete economically with fossil fuel-fired electricity. The state of PV manufacturing, the market and the effects of scale on both are reviewed. Government policies necessary to construct a multi-gigaWatt PV factory and complementary policies to protect existing solar companies are outlined and the technical requirements for a symbiotic industrial system are explored to increase the manufacturing efficiency while improving the environmental impact of PV. The results of the analysis show that an eight-factory industrial symbiotic system can be viewed as a medium-term investment by any government, which will not only obtain direct financial return, but also an improved global environment. The technical concepts and policy limitations to this approach were analyzed and it was found that symbiotic growth will help to mitigate many of the limitations of PV and is likely to catalyze mass manufacturing of PV by transparently demonstrating that large-scale PV manufacturing is technically feasible and reaches an enormous untapped market for PV with low costs.     

Life cycle assessment study of solar PV systems: An example of a 2.7 kWp distributed solar PV system in Singapore

In life cycle assessment (LCA) of solar PV systems, energy pay back time (EPBT) is the commonly used indicator to justify its primary energy use. However, EPBT is a function of competing energy sources with which electricity from solar PV is compared, and amount of electricity generated from the solar PV system which varies with local irradiation and ambient conditions. Therefore, it is more appropriate to use site-specific EPBT for major decision-making in power generation planning. LCA and life cycle cost analysis are performed for a distributed 2.7 kW_p grid-connected mono-crystalline solar PV system operating in Singapore. This paper presents various EPBT analyses of the solar PV system with reference to a fuel oil-fired steam turbine and their greenhouse gas (GHG) emissions and costs are also compared. The study reveals that GHG emission from electricity generation from the solar PV system is less than one-fourth that from an oil-fired steam turbine plant and one-half that from a gas-fired combined cycle plant. However, the cost of electricity is about five to seven times higher than that from the oil or gas fired power plant. The environmental uncertainties of the solar PV system are also critically reviewed and presented.     

Environmental payback time analysis of a roof-mounted building-integrated photovoltaic (BIPV) system in Hong Kong

This paper reports the investigation results of the energy payback time (EPBT) and greenhouse-gas payback time (GPBT) of a rooftop BIPV system (grid-connected) in Hong Kong to measure its sustainability. The 22 kWp PV array is facing south with inclined angle of 22.5°. The hourly solar irradiance and ambient air temperature from 1996 to 2000 were used as weather data input. The annual power output was found to be 28,154 kWh. The embodied energy for the whole system in the lifespan was 205,816 kWh, including 71% from PV modules and 29% from balance of system (BOS). The percentage of embodied energy for silicon purification and processing reached 46%. The EPBT of the PV system was 7.3 years, and the GPBT was estimated to be 5.2 years considering fuel mixture composition of local power stations. This paper also discussed the EPBTs for different orientations, ranging from 7.1 years (optimal orientation) to 20.0 years (west-facing vertical PV façade). The results show that the ‘sustainability’ of a PV system is affected by its installation orientation and location. Choosing locations and orientations with higher incident solar irradiance is one key for the sustainability of BIPV technology applications.     

基于相变微胶囊悬浮液的太阳能光伏热系统的研究进展

在太阳能光伏热系统中,光伏电池温度过高会导致太阳能发电效率下降。相变微胶囊悬浮液(MEPCMS)是一种潜热型功能性流体,将其作为冷却介质用于太阳能光伏热系统可以有效降低光伏电池温度,提高系统的能量利用率。针对相变微胶囊易泄露、导热性差等问题提出了改性方法,使其具有光热转换功能并提升了综合性能。基于性能评价指标分析了太阳能光伏热系统性能的影响因素。结果发现,流速、浓度和太阳辐照量是影响MEPCMS在太阳能光伏热系统中换热性能的关键因素。适当增加MEPCMS浓度和流速能提高工质的换热性能,在降低光伏板温度的同时增加太阳辐照量和系统热电产量,但需结合太阳辐照量大小合理匹配工质的浓度和流速。未来研究方向可集中在提升MEPCMS在太阳能光伏热系统中的换热性能、探究运行参数和太阳辐照量之间的匹配关系、优化集热器结构、利用其蓄热性解决太阳能间歇性等方面。     

Scalable methodology for the photovoltaic solar energy potential assessment based on available roof surface area: Further improvements by ortho-image analysis and application to Turin (Italy)

The ongoing rush of the UE member states to the 2020 overall targets on the national renewable energy share (see Directive 2009/28/EC), is propelling the large exploitation of the solar resource for the electricity production. However, the incentives to the large employment of PV solar modules and the relative perspective profits, are often cause of massive ground-mounted installations. These kind of installations are obviously the preferred solution by the investors for their high economic yields, but their social impact should be also considered. Over the Piedmont Region for instance, the large proliferation of PV farms is jeopardising wide agricultural terrains and turistic areas, therefore the policy of the actual administration is to encourage the use of integrated systems in place of massive installations. For these reasons, an effort to demonstrate that the distributed residential generation can play a primary role in the market is mandatory. In our previous work “Scalable methodology for the photovoltaic solar energy potential assessment based on available roof surface area: application to Piedmont Region (Italy)”, we already proposed a basic methodology for the evaluation of the roof-top PV system potential. However, despite the total roof surface has been computed on a given cartographical dataset, the real roof surface available for PV installations has been evaluated through the assumption of representative roofing typologies and empirical coefficients found via visual inspection of satellite images. In order to overcome this arbitrariness and refine our methodology, in the present paper we present a brand new algorithm to compute the available roof surface, based on the systematical analysis and processing of aerial georeferenced images (ortho-images). The algorithm, fully developed in MATLAB®, accounts for shadow, roof surface available (bright and not), roof features (i.e. chimneys or walls) and azimuthal angle of the eventual installation. Here we apply the algorithm to the whole city of Turin, and process more than 60,000 buildings. The results achieved are finally compared with our previous work and the updated PV potential assessment is consequently discussed.     

Analysis of grid connected solar PV system in the southeastern part of Bangladesh

Bangladesh is a potential site of implementing renewable energy system to reduce the severe power crisis throughout the year. According to this, Chittagong is the southeastern part of Bangladesh is also a potential site for implementing renewable energy system such as grid-connected photovoltaic (PV) system. Financial viability and green-house gas emission reduction of solar PV as an electricity generation source are assessed for 500 kW grid connected solar PV system at University of Chittagong, Chittagong. Homer simulation software and monthly average solar radiation data from NASA is used for this task. In the proposed system monthly electricity generation varies between 82.65 MW h and 60.3 MW h throughout the year with a mean value of 68.25 MW h depending on the monthly highest and lowest solar radiation data. It is found that per unit electricity production cost is US$ 0.20 based on project lifetime 25 years. The IRR, equity payback and benefit-cost ratio shows favorable condition for development of the proposed solar PV system in this site. A minimum 664 tones of green-house gas emissions can be reduced annually utilizing the proposed system.     

Technico-economic analysis of off grid solar PV/Fuel cell energy system for residential community in desert region

A technico-economic analysis based on integrated modeling, simulation, and optimization approach is used in this study to design an off grid hybrid solar PV/Fuel Cell power system. The main objective is to optimize the design and develop dispatch control strategies of the standalone hybrid renewable power system to meet the desired electric load of a residential community located in a desert region. The effects of temperature and dust accumulation on the solar PV panels on the design and performance of the hybrid power system in a desert region is investigated. The goal of the proposed off-grid hybrid renewable energy system is to increase the penetration of renewable energy in the energy mix, reduce the greenhouse gas emissions from fossil fuel combustion, and lower the cost of energy from the power systems. Simulation, modeling, optimization and dispatch control strategies were used in this study to determine the performance and the cost of the proposed hybrid renewable power system. The simulation results show that the distributed power generation using solar PV and Fuel Cell energy systems integrated with an electrolyzer for hydrogen production and using cycle charging dispatch control strategy (the fuel cell will operate to meet the AC primary load and the surplus of electrical power is used to run the electrolyzer) offers the best performance. The hybrid power system was designed to meet the energy demand of 4500 kWh/day of the residential community (150 houses). The total power production from the distributed hybrid energy system was 52% from the solar PV, and 48% from the fuel cell. From the total electricity generated from the photovoltaic hydrogen fuel cell hybrid system, 80.70% is used to meet all the AC load of the residential community with negligible unmet AC primary load (0.08%), 14.08% is the input DC power for the electrolyzer for hydrogen production, 3.30% are the losses in the DC/AC inverter, and 1.84% is the excess power (dumped energy). The proposed off-grid hybrid renewable power system has 40.2% renewable fraction, is economically viable with a levelized cost of energy of 145 $/MWh and is environmentally friendly (zero carbon dioxide emissions during the electricity generation from the solar PV and Fuel Cell hybrid power system).     

Integration of temperature and dust effects in siting large PV power plant in hot arid area

Recently, solar PV technologies witnessed a commercial vigor due to their tremendously decreasing prices. However, these technologies are vulnerable to dust and temperature which can significantly degrade their efficiency. Taking into account, the effect of dust and temperature during the site assessment for large PV power plant will reduce their vulnerability and optimize their operation efficiency. Most of the site assessment for large PV power plants does not take into consideration spatio-temporal variability of dust and temperature effects due to their measurement complexity. This paper presents an original approach of integration of the effects of temperature and dust in siting large PV power plant using Fuzzy logic and GIS-based spatial multi-criteria evaluation. Dynamical downscaling approach of the high resolution COSMO Numerical Weather Prediction model is used to simulate the annual pattern of temperature and the Aerosol Optical Depth (AOD) derived from Multi-angle Imaging Spectro-Radiometer (MISR) is used to retrieve the contamination degree of the air with mineral aerosol. Land suitability analysis for large PV farms implementation is carried out for the case study of Oman. Compared to previous results obtained without temperature and AOD, the new results show that several areas are declassified because of their exposure to high temperature and dust risks. It is noticed that the highly suitable land areas decreased significantly by 81% after considering the temperature and dust constraint layers. Different PV technologies are considered and it is found that the Concentrated Photovoltaics (CPV) technology provides higher potential for implementing large solar plants. In fact, if all highly suitable land is exploited for CPV farms, it can supply more than 750 times the current total power supply in Oman estimated at 16.1 TWh in 2010.     

Numerically study on a new hybrid photovoltaic thermal (PVT) collectors with natural circulation

Traditional design of Hybrid photovoltaic thermal (PV/T) system has the solar cells fixed on the top of the absorber. A new PV/T system in which the solar cells are pasted on the bottom of the glass cover is suggested with the aim of realizing higher electricity output considering the lower temperature of glass cover compared with that of absorber. A numerical analysis model is set up to compare the performances of the traditional PV/T and the new PV/T in this study. It is found that compared to the traditional PV/T, the new PV/T shows higher daily electric efficiency. But this superiority is not as apparent as expected. The key point to increase the daily electric efficiency of a PV/T lies in increasing the solar energy transfer efficiency of the solar cell. The total energy gain of the new PV/T is about 7% lower than that of the traditional PV/T because of smaller mass rate and more energy loss from glass cover with higher temperature.     

跟踪式光伏发电系统研究

根据某地实测的太阳辐射数据,仿真比较了配备有单轴跟踪和双轴跟踪等4种跟踪控制的光伏发电系统与固定式光伏发电系统的太阳辐射利用率。并在此基础上对4种跟踪系统的跟踪角控制规律及跟踪控制方式进行了详细的分析,得出倾纬度角单轴跟踪系统控制规律最为简单,算法实施更为实用的结论。同时,也在理论上证明了采用步进式控制方式的跟踪系统能够在保持较高太阳辐射利用率情况下简化控制系统设计,有利于工程设计及应用。     

Hybrid photovoltaic/thermal (PV/T) solar systems simulation with Simulink/Matlab

The purpose of this work consists in thermodynamic modeling of hybrid photovoltaic–thermal (PV/T) solar systems, pursuing a modular strategy approach provided by Simulink/Matlab.PV/T solar systems are a recently emerging solar technology that allows for the simultaneous conversion of solar energy into both electricity and heat. This type of technology present some interesting advantages over the conventional “side-by-side” thermal and PV solar systems, such as higher combined electrical/thermal energy outputs per unit area, and a more uniform and aesthetical pleasant roof area. Despite the fact that early research on PV/T systems can be traced back to the seventies, only recently it has gained a renewed impetus. In this work, parametric studies and annual transient simulations of PV/T systems are undertaken in Simulink/Matlab. The obtained results show an average annual solar fraction of 67%, and a global overall efficiency of 24% (i.e. 15% thermal and 9% electrical), for a typical four-person single-familiar residency in Lisbon, with p-Si cells, and a collector area of 6 m². A sensitivity analysis performed on the PV/T collector suggests that the most important variable that should be addressed to improve thermal performance is the photovoltaic (PV) module emittance. Based on those results, some additional improvements are proposed, such as the use of vacuum, or a noble gas at low-pressure, to allow for the removal of PV cells encapsulation without air oxidation and degradation, and thus reducing the PV module emittance. Preliminary results show that this option allows for an 8% increase on optical thermal efficiency, and a substantial reduction of thermal losses, suggesting the possibility of working at higher fluid temperatures. The higher working temperatures negative effect in electrical efficiency was negligible, due to compensation by improved optical properties. The simulation results are compared with experimental data obtained from other authors and perform reasonably well.The Simulink modeling platform has been mainly used worldwide on simulation of control systems, digital signal processing and electric circuits, but there are very few examples of application to solar energy systems modeling. This work uses the modular environment of Simulink/Matlab to model individual PV/T system components, and to assemble the entire installation layout. The results show that the modular approach strategy provided by Matlab/Simulink environment is applicable to solar systems modeling, providing good code scalability, faster developing time, and simpler integration with external computational tools, when compared with traditional imperative-oriented programming languages.