Sunshine environment and spectrum analysis for concentrator PV systems in Japan

Normal direct irradiance levels for concentrator photovoltaic were investigated and anticipated in 26 sunshine regions in Japan. The spectrum and photon numbers were also examined. Normal direct photon number was assumed to be 92–60% of global the sunshine on sloped surfaces in all the districts in Japan.     

A 24-h forecast of solar irradiance using artificial neural network: Application for performance prediction of a grid-connected PV plant at Trieste, Italy

Forecasting of solar irradiance is in general significant for planning the operations of power plants which convert renewable energies into electricity. In particular, the possibility to predict the solar irradiance (up to 24 h or even more) can became - with reference to the Grid Connected Photovoltaic Plants (GCPV) - fundamental in making power dispatching plans and - with reference to stand alone and hybrid systems - also a useful reference for improving the control algorithms of charge controllers. In this paper, a practical method for solar irradiance forecast using artificial neural network (ANN) is presented. The proposed Multilayer Perceptron MLP-model makes it possible to forecast the solar irradiance on a base of 24 h using the present values of the mean daily solar irradiance and air temperature. An experimental database of solar irradiance and air temperature data (from July 1st 2008 to May 23rd 2009 and from November 23rd 2009 to January 24th 2010) has been used. The database has been collected in Trieste (latitude 45°40′N, longitude 13°46′E), Italy. In order to check the generalization capability of the MLP-forecaster, a K-fold cross-validation was carried out. The results indicate that the proposed model performs well, while the correlation coefficient is in the range 98-99% for sunny days and 94-96% for cloudy days. As an application, the comparison between the forecasted one and the energy produced by the GCPV plant installed on the rooftop of the municipality of Trieste shows the goodness of the proposed model.     

Solar photovoltaic (PV) energy; latest developments in the building integrated and hybrid PV systems

Environmental concerns are growing and interest in environmental issues is increasing and the idea of generating electricity with less pollution is becoming more and more attractive. Unlike conventional generation systems, fuel of the solar photovoltaic energy is available at no cost. And solar photovoltaic energy systems generate electricity pollution-free and can easily be installed on the roof of residential as well as on the wall of commercial buildings as grid-connected PV application. In addition to grid-connected rooftop PV systems, solar photovoltaic energy offers a solution for supplying electricity to remote located communities and facilities, those not accessible by electricity companies.The interest in solar photovoltaic energy is growing worldwide. Today, more than 3500 MW of photovoltaic systems have been installed all over the world. Since 1970, the PV price has continuously dropped [8]. This price drop has encouraged worldwide application of small-scale residential PV systems. These recent developments have led researchers concerned with the environment to undertake extensive research projects for harnessing renewable energy sources including solar energy. The usage of solar photovoltaic as a source of energy is considered more seriously making future of this technology looks promising.The objective of this contribution is to present the latest developments in the area of solar photovoltaic energy systems. A further objective of this contribution is to discuss the long-term prospect of the solar photovoltaic energy as a sustainable energy supply.     

Investigation on abundant photovoltaic power generated by 40 kW PV system in Wakayama National College of Technology

We investigated the output characteristics of 40 kW photovoltaic (PV) power system installed at Wakayama National College of Technology. The total amount of PV power measured from our 40 kW PV system was 53 431.5 kW h/year. This abundant PV power was attributable to the greater amount of solar radiation and low temperature of the PV module.     

Efficiency enhancement of stationary solar energy based power conversion systems in Canada

This paper presents the optimum energy conversion conditions of stationary photovoltaic panels used for electrical power generation. The results are arrived at after performing calculations for 180 days in a given year at the latitude of St. John’s, Newfoundland. The latitude of this city is close to other Canadian major population centers. Various angular orientations of sun’s rays on the earth are considered. On a given day, the incident energy flux of sun is resolved into three components, and the conversion efficiency is based on the flux normal to the panels. The efficiency of conversion of the incident energy is measured with respect to a solar tracking process. The numbers of days in a given year are divided into two groups – one between the winter solstice and the spring equinox, and another between the spring equinox and the summer solstice.     

Short-term forecasting of wind speed and related electrical power

Wind speed and the related electrical power of wind turbines are forecasted. The work is focused on the operation of power systems with integrated wind parks. Artificial neural networks models are proposed for forecasting average values of the following 10 min or 1 h. Input quantities for the prediction are wind speeds and their derivatives. Also, spatial correlation of wind speeds and its use for forecasting, are investigated. The methods are tested using data collected over seven years at six different sites on islands of the South and Central Aegean Sea in Greece.     

向太阳索取--中国太阳光-热与光-电应用现状与展望

我国有丰富的太阳能资源,已有25年光-热研究历史。10年来,太阳热水系统的生产发展迅速。2002年各种太阳热水系统销售约1000万m^2,主要是获得生活热水,一些其他的应用正在研究与开发。光-电研究与开发已有30多年了,应用在卫星、灯塔和通信等领域。2002年一个巨大的国家项目“送电到乡”的实施,完成了17MWp,这加速了我国的光-电产业。     

新疆光伏发电现状及发展对策

介绍了新疆得天独厚的环境资源和光伏应用发展现状，分析了在该地区进行光伏电汽推广应用的市场潜力，指出了发展过程中存在的问题，并提出了相应的建议。     

Frequency control by the PV station in electric power systems with hydrogen energy storage

The rapid growth of renewable energy capacity, in particular photovoltaic systems, is creating challenges associated with changing the rate of transient processes in the power system. This is due to the approach PV systems are connected to the grid using power converters and the absence of a rotating mass in the PV power plant. One of the most pressing challenge is the participation of PV stations in the process of frequency control in power systems, including in emergency modes. Simultaneously with PV power plants, it is efficient to use energy storage systems, including hydrogen ones. This is due to the fact that it is possible to obtain hydrogen for such energy storage systems using excess energy from PV power plants. The article proposes to solve the problem of frequency regulation in the power system by using an algorithm that allows to control the frequency in the power system using a synthetic inertia block of PV station, including at different levels of insolation and temperature of PV panels. The robustness of the proposed algorithm allows it to be used at different levels of power generated by the PV station, as well as in emergency modes.     

Combining solar irradiance measurements,satellite-derived data and a numerical weather prediction model to improve intra-day solar forecasting

Isolated power systems need to generate all the electricity demand with their own renewable resources. Among the latter, solar energy may account for a large share. However, solar energy is a fluctuating source and the island power grid could present an unstable behavior with a high solar penetration. Global Horizontal Solar Irradiance (GHI) forecasting is an important issue to increase solar energy production into electric power system. This study is focused in hourly GHI forecasting from 1 to 6 h ahead. Several statistical models have been successfully tested in GHI forecasting, such us autoregressive (AR), autoregressive moving average (ARMA) and Artificial Neural Networks (ANN). In this paper, ANN models are designed to produce intra-day solar forecasts using ground and exogenous data. Ground data were obtained from two measurement stations in Gran Canaria Island. In order to improve the results obtained with ground data, satellite GHI data (from Helioclim-3) as well as solar radiation and Total Cloud Cover forecasts provided by the European Centre for Medium-Range Weather Forecasts (ECMWF) are used as additional inputs of the ANN model. It is shown that combining exogenous data (satellite and ECMWF forecasts) with ground data further improves the accuracy of the intra-day forecasts.     

A novel maximum power point tracking in partially shaded PV systems using a hybrid method

To exploit photovoltaic systems, a major point that merits attention is to find maximum output power for the efficiency increase. The output power of solar cells depends on the ambient temperature and intensity of solar radiation. The cloud phenomenon creates a partially shaded on solar arrays; in this condition, the power–voltage curve of a solar array has several local maximum points. When there is uniform radiation, conventional methods of maximum power point tracking (MPPT) can be used. However, these methods are not efficient in partially shaded, due to the existence of several Maximum Power Points (MPPs) in the power-voltage characteristic. In this paper, a novel method for MPP tracking under the partially shaded is proposed, which is a combination of observational tracking and constant–voltage methods. When there is uniform radiation, the tracking operation is observed and tracked by a fuzzy logic–based approach. The proposed method is based on the existence of a relationship between radiation intensity and MPP voltage. In the existence of this relationship, the MPP voltage can be calculated by measuring the intensity of radiation at any moment. In addition, partially shaded works using the constant-voltage method. To verify the simulation results, laboratory implementation was performed. The results show that with considering the MPPs, the output power increases about 10% while the partially shaded is applied.     

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.     

Positioning of PV panels for reduction in line losses and mismatch losses in PV array

Partial shading decreases the power output of PV arrays due to mismatch losses. These losses are dependent on the shading pattern and the relative positions of shaded modules in the array. Various static and dynamic reconfiguration techniques have earlier been proposed to mitigate these losses. In an earlier proposed static reconfiguration technique, the power generation is enhanced by altering the physical location of the PV panels using a random Sudoku configuration without modifying the TCT (Total-Cross-Tied) based electrical connections. However, this arrangement faces drawbacks due to ineffective dispersion of shade and significant increase in wiring required. In this work, an optimal Sudoku arrangement to overcome these drawbacks is formulated. Further analysis indicate that the global peak of the optimal Sudoku based PV array occurs as the right most peak in the curve for most shading conditions, thus evidently obviating the need for complex MPPT (Maximum-Power-Point-Tracking) algorithms. The proposed configuration is compared with various other existing reconfiguration schemes in terms of power output and the comparison is presented. In addition, a general formulation is proposed to expand this pattern to any generic array. A strategy is also proposed to make such an interconnection practicable for very large size PV arrays.     

Business models and financing options for a rapid scale-up of rooftop solar power systems in Thailand

Diverse solar PV business models and financing options exist in the international landscape, helping expand and accelerate the adoption of rooftop solar PV systems. The conditions for their emergence are context specific, depending on the policies, regulations, incentives, and market conditions of each country. After a review of the international landscape, this paper compiles and analyzes business models and financing options for rooftop solar PV investment in Thailand that have emerged during the period between 2013 and 2015. Despite policy discontinuity for the support of rooftop solar systems, diverse business models and financing options are driving market expansion and expanding solar access to more Thai consumers. Drawing on our policy and regulatory analyses and in-depth interviews with business representatives, we identify four types of business models and one financing option. The business models include Roof Rental, Solar PPA, Solar Leasing, and Community Solar, and the financing option is the solar loan. We analyze the drivers for their emergence, barriers to their success, and the risks from the business owners' and consumers' viewpoints. Our policy recommendation is focused on crafting a net-metering regulation with evidence-based studies on the potential costs and benefits to different stakeholders.     

Estimation of the PV potential in ASEAN with a high spatial and temporal resolution

Further exploitation of renewable energy sources for power generation could mitigate the current rapid increase of greenhouse gas emissions in South East Asia. In this context, solar PV is a promising option as PV system costs have been declining continuously over the past. In order to define strategies towards a low-carbon future power supply, detailed information on the potential power output of solar PV is essential.Therefore, this paper analyses the resource and technical potential of solar PV in South East Asia in high temporal and spatial resolution. An empirical, climate-based Ångström-Prescott model is proposed in order to adjust MERRA solar radiation data. The possible power output of PV is derived considering topographic and land-use constraints as well as technological characteristics of typical PV systems.Java, central Myanmar and eastern Thailand were identified to be the best locations for PV use, with capacity factors exceeding 15%. Due to the large land area which is suitable for PV installations, South East Asia offers an abundant theoretical potential of solar PV, amounting to 430 TW h with conservative assumptions.     

Influence of local wind speed and direction on wind power dynamics – Application to offshore very short-term forecasting

Wind power time series usually show complex dynamics mainly due to non-linearities related to the wind physics and the power transformation process in wind farms. This article provides an approach to the incorporation of observed local variables (wind speed and direction) to model some of these effects by means of statistical models. To this end, a benchmarking between two different families of varying-coefficient models (regime-switching and conditional parametric models) is carried out. The case of the offshore wind farm of Horns Rev in Denmark has been considered. The analysis is focused on one-step ahead forecasting and a time series resolution of 10 min. It has been found that the local wind direction contributes to model some features of the prevailing winds, such as the impact of the wind direction on the wind variability, whereas the non-linearities related to the power transformation process can be introduced by considering the local wind speed. In both cases, conditional parametric models showed a better performance than the one achieved by the regime-switching strategy. The results attained reinforce the idea that each explanatory variable allows the modelling of different underlying effects in the dynamics of wind power time series.     

Semi-transparent PV: Thermal performance, power generation, daylight modelling and energy saving potential in a residential application

In this research, semi-transparent PV is proposed as top light material for residential application. Using the results of field measurements, essential parameters pertaining to the power generation, thermal and optical characteristics of semi-transparent PV panels are understood. Calculation models presenting the above characteristics are developed and validated. The validated models are incorporated into Energy Plus to carry out overall energy consumption analyses in five climate regions in Japan to assess the energy saving potential of the semi-transparent PV panels. With appropriate optimization measures, the semi-transparent PV top light with 50% radiation transmission rate contributes to a maximum of 5.3% reduction in heating and cooling energy consumption compared with a standard BiPV roof. The effect of daylighting in lighting energy saving is subtle as most of the residential lighting demand occur during night-time. In the aspect of total energy consumption, net energy savings in the range of 3.0–8.7% are achieved for the 50% radiation transmission semi-transparent PV top light case relative to the base case of BiPV roof, where reduction in heating and cooling energy demand contributes most to the total energy saving.     

中德财政合作项目西部村落光伏电站运行情况及性能分析

中德财政合作项目"西部村落光伏电站"预计建设光伏或光柴互补村落电站约210个,解决近万户农牧民及部分学校、卫生所等公益设施的基本用电需求,目前已有62座电站通过验收开始运行.以已经通过最终验收的新疆维吾尔自治区一期9个电站为例,分析了西部边远地区村落光伏电站系统效率、供电情况与居民用电特点、村落电网线路损耗以及户均用电量.电站的长期运行与设备情况仍需要进一步的数据监测与分析.     

On the use of reactive power as an endogenous variable in short‐term load forecasting

In the last decades, short‐term load forecasting(STLF) has been the object of particular attention in the power systems field. STLF has been applied almost exclusively to the generation sector, based on variables, which are transversal to most models. Among the most significant variables we can find load, expressed as active power (MW), as well as exogenous variables, such as weather and economy‐related ones; although the latter are applied in larger forecasting horizons than STLF. In this paper, the application of STLF to the distribution sector is suggested including inductive reactive power as a forecasting endogenous variable. The inclusion of this additional variable is mainly due to the evidence that correlations between load and weather variables are tenuous, due to the mild climate of the actual case‐study system and the consequent feeble penetration of electrical heating ventilation and air conditioning loads. Artificial neural networks (ANN) have been chosen as the forecasting methodology, with standard feed forward back propagation algorithm, because it is a largely used method with generally considered satisfactory results. Usually the input vector to ANN applied to load forecasting is defined in a discretionary way, mainly based on experience, on engineering judgement criteria and on concern about the ANN dimension, always taking into consideration the apparent (or actually evaluated) correlations within the available data. The approach referred in the paper includes pre‐processing the data in order to influence the composition of the input vector in such a way as to reduce the margin of discretion in its definition. A relative entropy analysis has been performed to the time series of each variable. The paper also includes an illustrative case study. Copyright © 2003 John Wiley & Sons, Ltd.     

Integrated standalone hybrid solar PV,fuel cell and diesel generator power system for battery or supercapacitor storage systems in Khorfakkan,United Arab Emirates

Renewable energy resources play a very important rule these days to assist the conventional energy systems for doing its function in the UAE due to high greenhouse gas (GHG) emissions and energy demand. In this paper, the analysis and performance of integrated standalone hybrid solar PV, fuel cell and diesel generator power system with battery energy storage system (BESS) or supercapacitor energy storage system (SCESS) in Khorfakkan city, Sharjah were presented. HOMER Pro software was used to model and simulate the hybrid energy system (HES) based on the daily energy consumption for Khorfakkan city. The simulation results show that using SCESS as an energy storage system will help the performance of HES based on the Levelized cost of energy (LCOE) and greenhouse gas (GHG) emissions. The HES with SCESS has renewable fraction (68.1%) and 0.346 $/kWh LCOE. The HES meets the annual AC primary load of the city (13.6 GWh) with negligible electricity excess and with an unmet electrical load of 1.38%. The reduction in GHG emissions for HES with SCESS was 83.2%, equivalent to saving 814,428 gallons of diesel.