Life cycle assessment of crystalline photovoltaics in the Swiss ecoinvent database

This paper describes the life cycle assessment (LCA) for photovoltaic (PV) power plants in the new ecoinvent database. Twelve different, grid‐connected photovoltaic systems were studied for the situation in Switzerland in the year 2000. They are manufactured as panels or laminates, from monocrystalline or polycrystalline silicon, installed on facades, slanted or flat roofs, and have 3 kW_p capacity. The process data include quartz reduction, silicon purification, wafer, panel and laminate production, mounting structure, 30 years operation and dismantling. In contrast to existing LCA studies, country‐specific electricity mixes have been considered in the life cycle inventory (LCI) in order to reflect the present market situation. The new approach for the allocation procedure in the inventory of silicon purification, as a critical issue of former studies, is discussed in detail. The LCI for photovoltaic electricity shows that each production stage is important for certain elementary flows. A life cycle impact assessment (LCIA) shows that there are important environmental impacts not directly related to the energy use (e.g., process emissions of NO_x from wafer etching). The assumption for the used supply energy mixes is important for the overall LCIA results of different production stages. The presented life cycle inventories for photovoltaic power plants are representative for newly constructed plants and for the average photovoltaic mix in Switzerland in the year 2000. A scenario for a future technology (until 2010) helps to assess the relative influence of technology improvements for some processes. The very detailed ecoinvent database forms a good basis for similar studies in other European countries or for other types of solar cells. Copyright © 2005 John Wiley & Sons, Ltd.     

On‐site characterisation and energy efficiency of grid‐connected PV inverters

The size of inverters in large grid‐connected photovoltaic (PV) systems is increasing. At present, the largest installed inverters have nominal powers of several hundreds of kW, which makes their characterisation in the laboratory difficult. As an alternative, on‐site characterisation requires only measurement equipment and has the advantage that the inverter is tested in its own PV system under real operating conditions. This paper describes an on‐site testing procedure for assessing the power efficiency of an inverter and the results obtained for 13 inverters with nominal powers between 3.3 and 350 kW. The inverters were tested in PV grid‐connected systems whose aggregate power capacity is nearly 150 MW. The energy efficiency of the inverters tested was also calculated yearly, and the results were compared with both European and Californian energy efficiency parameters, which are widely used in the current PV market. Copyright © 2010 John Wiley & Sons, Ltd.     

Distributed power generation versus grid extension: an assessment of solar photovoltaics for rural electrification in Northern Ghana

The competitiveness of distributed solar photovoltaic (PV) power generation for rural electrification in northern Ghana is assessed and compared with the conventional option of extending the national grid and increasing the capacity for centralised power generation. A model is constructed to calculate the life‐cycle cost (LCC) of the two options and to test the sensitivity of different parameters. All calculations are based on information from the GEF/UNDP pilot region in the East Mamprusi District. In addition to the economic aspect, issues of quality and environmental effects are discussed. The LCC of distributed PV is lower than that of a grid extension for an electricity demand corresponding to solar home systems of 140 W_p or smaller. Thus, distributed PV is cost competitive for purposes of lighting, entertainment, information and basic public facilities, such as schools and hospitals. The LCC for the option of grid extension with central power generation is dominated by the cost of low‐voltage micro‐grids within the communities. Important factors are the density of households and the penetration (fraction of households electrified), as they affect the line length per connected household. The relatively low cost of regional medium‐voltage grids makes the geographical location of each community less important than expected. Battery replacement every fifth year makes up the major part of the LCC of solar home systems and is also responsible for the large energy input in the production of the systems. This could limit both future cost reductions of distributed PV and its potential to mitigate greenhouse gas emissions. Copyright © 2002 John Wiley & Sons, Ltd.     

Analytical study and evaluation results of power optimizers for distributed power conditioning in photovoltaic arrays

The use of modular or ‘micro’ maximum power point tracking (MPPT) converters at module level in series association, commercially known as “power optimizers”, allows the individual adaptation of each panel to the load, solving part of the problems related to partial shadows and different tilt and/or orientation angles of the photovoltaic (PV) modules. This is particularly relevant in building integrated PV systems. This paper presents useful behavioural analytical studies of cascade MPPT converters and evaluation test results of a prototype developed under a Spanish national research project. On the one hand, this work focuses on the development of new useful expressions which can be used to identify the behaviour of individual MPPT converters applied to each module and connected in series, in a typical grid‐connected PV system. On the other hand, a novel characterization method of MPPT converters is developed, and experimental results of the prototype are obtained: when individual partial shading is applied, and they are connected in a typical grid connected PV array. Copyright © 2011 John Wiley & Sons, Ltd.     

Photovoltaic power plant experience at Arizona Public Service: a 5‐year assessment

Arizona Public Service (APS) currently has over 4·9 MW_dc of grid‐connected photovoltaic systems that have been installed in its service territory over the past five years. Most of this installed PV capacity is in support of the Arizona Corporation Commission Environmental Portfolio Standard goal that encourages APS to generate 1·1% of its energy generation through renewable resources by 2007, with 60% of that amount from solar. During this time, much has been learned regarding performance, cost, maintenance, installation and design. This paper presents an assessment of these topics and a perspective associated with this PV experience. Published in 2005 by John Wiley & Sons, Ltd.     

Assessment of the adequacy of EN ISO 15927‐4 reference years for photovoltaic systems

The long‐term performance prediction of photovoltaic systems requires representative meteorological data from a particular location. Among the numerous proposals in the field of solar energy, most of them include procedures oriented towards the generation of test reference years (TRYs). These synthetic years are composed of the concatenation of 12 actual months of the time series of meteorological measurements. Using TRYs to simulate the performance of different types of solar energy systems reduces the computational effort of the simulation and simplifies the analysis of the results. In this sense, the technical standard EN ISO 15927‐4 describes a procedure for constructing a reference year suitable for evaluation of the annual heating and cooling long‐term needs in buildings. In this work, the adequacy of the EN ISO 15927‐4 reference year for photovoltaic systems was studied. The electricity production obtained by simulation with this TRY was compared with that obtained by the Weather Year for Solar Systems. This latter reference year only uses the monthly thermal energy collected by the system as a selection parameter of typical months. This comparison was performed for seven locations in the USA considering two 5.6 kWp grid‐connected photovoltaic systems that only differ in the solar tracking system. The suitability of the EN ISO 15927‐4 reference year for the estimation of the electrical energy generated by a photovoltaic system has been proved, showing good results in the annual and daily predictions in most of the cases studied. Copyright © 2015 John Wiley & Sons, Ltd.     

Analyzing historical cost trends in California's market for customer‐sited photovoltaics

This paper reports highlights from a detailed statistical analysis of the cost of customer‐sited, grid‐connected photovoltaic installations in the largest solar market in the United States: California. It is based on an analysis of 18 942 PV systems, totaling 254 MW_AC, either funded or approved for funding under two separate rebate programs overseen by the California Energy Commission and the California Public Utilities Commission. We find that: (1) solar costs have declined substantially over time; (2) policy incentives have impacted pre‐rebate installed costs, and some cost inflation is apparent; (3) economies of scale have driven down costs for larger systems; (4) systems installed in new home developments and in affordable housing projects have experienced much lower costs than the general retrofit market; and (5) installer experience and type have affected costs, but the effects differ by program. Results hold important implications for solar suppliers and customers, and for policymakers designing incentive programs. Copyright © 2006 John Wiley & Sons, Ltd.     

基于多Agent的光伏并网发电控制系统设计

光伏发电作为一种新型能源得到了广泛的应用,针对光伏发电并网产生的问题,结合多Agent技术建立基于多Agent技术分布式协同光伏并网发电控制系统,依靠Agent技术的特点实现对光伏并网问题的预测和保护,从而确保光伏发电并网安全运行。     

Modeling a grid‐connected concentrator photovoltaic system

A six‐parameter formula is proposed for describing the hourly alternating current performance of a grid‐connected, passively cooled concentrator photovoltaic (CPV) system. These system parameters all have physical meanings, and techniques are described for deriving their numerical values. The predictions of the model are compared with the measured output of a Soitec CPV system at Sede Boqer and found to be accurate to approximately ± 5% at all times of the year. The model should also be valid for systems of similar construction operated in different climates from the system studied here, and also for passively cooled CPV systems of different designs provided that suitable numerical values are determined for their system parameters. Another possible use of the model is as a guide for tailoring CPV cell architecture to the particular spectral conditions of the locations in which they will operate. Attention is drawn to the fact that the numerical values of some of the system parameters are found to depend upon the time binning employed for the data. An explanation is given for this phenomenon, which is also found to occur for non‐concentrating photovoltaic panels. Copyright © 2014 John Wiley & Sons, Ltd.     

Prevention of islanding in grid‐connected photovoltaic systems

Recently there has been a resurgence of concern about islanding of grid‐connected photovoltaic (PV) systems. This condition occurs when the PV system continues to energize a section of the grid after that section has been isolated from the main utility voltage source. Generally, islanding is undesirable because it poses a safety hazard to utility service personnel, and also because it can lead to asynchronous reclosure which can damage equipment. It is therefore important that PV systems incorporate methods to prevent islanding. The purpose of this paper is threefold: (1) to critically review the literature on islanding prevention methods for PV systems and discuss their strengths and shortcomings; (2) to review and analyze the islanding behavior of four converters which are prominent in the literature in order to demonstrate the implementation and effectiveness of some islanding prevention methods; and (3) to introduce a new islanding prevention scheme, active frequency drift with positive feedback, which overcomes many of the shortcomings of existing schemes. It is concluded that no ‘perfect’ islanding prevention method yet exists, but also that many existing methods or combinations thereof work very well in practical situations. Finally, it is noted than an investigation of what constitutes ‘sufficient’ islanding prevention is needed. Copyright © 1999 John Wiley & Sons, Ltd.     

Progress in markets for grid‐connected PV systems in the built environment

In the last decade of the 20th century a wide variety of promotion strategies increased the market penetration of small grid‐connected PV systems world‐wide. The objective of this paper is to assess the impact of these promotion strategies on the market for and on the economic performance of small grid‐connected PV systems. The most important conclusions of this analysis are: Pure cost‐effectiveness is not crucial for private customers. Affordability is rather what counts. Non‐monetary issues play an important role for a substantial increase in market deployment. Comprehensive accompanied information and education activities are also important along with financial incentives. There are still considerable barriers in the market: on the one hand transparent and competitive markets exist in only a few countries; on the other hand non‐monetary transaction costs still represent a major barrier. Progress with respect to cost reduction has been achieved, but mainly for non‐module components. Copyright © 2004 John Wiley & Sons, Ltd.     

Software modelling of grid‐connected photovoltaic buildings

This paper presents a software tool, freely available on the Worldwide Web, that can be concurrently run by multiple users on different hardware–software platforms. To evaluate the limits and competitiveness of PV energy in Spain, several companies, utilities and institutions have been working together in a project called FotoRED. Within this project, several computer tools have been developed to analyse the potential of connecting photovoltaic stations to the utility grid. One of these tools is the simulator presented here, a program to estimate the energy balance and economic behaviour of grid‐connected PV buildings. Depending on several construction parameters of the building, the photovoltaic generators installed, the geographical location, weather conditions, etc., the program estimates the energy consumed in the building, the photovoltaic energy that can be generated on‐site and the resulting energy balance on a daily, monthly and yearly basis. The economic behaviour of the building can also be simulated over a 30‐year period, generating cash‐flow diagrams, investment payback curves and other economic information to describe the building's expected performance. Many building designs and several existing buildings have been simulated with this tool so far. One example of these is presented and the conclusions reached during several simulation runs are discussed. Copyright © 2003 John Wiley & Sons, Ltd.     

Grid-connected amorphous silicon photovoltaic array

A roof-mounted photovoltaic (PV) array has been installed at Loughborough University in the UK. The array output is connected through a commercial grid-connected inverter to the University supply network. The system was the third grid-connected PV inst allation to be connected and generating in the UK. It is the first and only grid-connected system using amorphous silicon thin-film PV modules in the UK. The system is fully instrumented to support the research and development that CREST is conducting on grid-connected PV systems, including: inverters; thin-film amorphous silicon and the effects of shading on performance. The paper presented here describes the design, installation and commissioning of the system. Data from the first year of operation along with the results of a preliminary performance analysis are presented and discussed.     

Design methodology for the frequency shift method of islanding prevention and analysis of its detection capability

Islanding protection is one of the most important sources of discrepancy in grid‐connected photovoltaic systems. Even when islanding is not very likely to happen, regulations demand the photovoltaic inverters to implement effective protection methods. Due to its several advantages, the frequency shift method of islanding prevention, commonly known as Sandia Frequency Shift, is one of the most important active methods. This method implements a positive feedback of the frequency that tends to move it outside the trip limits in case of islanding. The method shows a very high detection capability, which depends on both the values of the method parameters and the characteristics of the load that remains in the same power section after islanding. This paper develops a mathematical analysis of the Sandia Frequency Shift method and proposes a new methodology to design its parameters as a trade‐off between the detection capability, which is evaluated as a function of the load characteristics, and the distortion that the method could introduce in the grid as a consequence of transitory frequency disturbances. The ability of this methodology to design the method parameters and achieve the highest detection capability is satisfactorily proved by means of both simulation and experimental results on a commercial photovoltaic inverter that implements the method once its parameters have been designed with the proposed methodology. Copyright © 2005 John Wiley & Sons, Ltd.     

Analysis Results of Output Power Loss Due to the Grid Voltage Rise in Grid-Connected Photovoltaic Power Generation Systems

This paper describes the connected photovoltaic (PV) power generation system's grid overvoltage protection function and summarizes the occurrence of the output power loss due to the grid voltage rise. Power injection from the PV system will raise the voltage at the power distribution line. A power conditioning subsystem (PCS) needs to regulate its output if the voltage becomes higher than the upper limit in order to avoid the overvoltage at the power grid. Thus, a PV system cannot generate electricity under the high grid voltage. There are 553 residential PV systems installed in Ota, Japan, for the demonstration research project of clustered PV systems. Measurement data of these 2.1-MW grid-connected PV systems are used for the analysis. Only the limited number of PV systems experienced a significant amount of output energy loss due to the high grid voltage in a particular day, whereas the other system's outputs also raise the grid voltage. The causes of this maldistribution of the output energy loss are the difference of the line impedance, the difference of the starting voltage of the PCS's grid overvoltage protection function, and the imbalance of the load in single-phase three-wire power distribution systems. The present control of the PCS successfully avoids the overvoltage on the grid but cannot share the loss.     

From irradiance to output power fluctuations: the PV plant as a low pass filter

The power generated by large grid‐connected photovoltaic (PV) plants depends greatly on the solar irradiance. This paper studies the effects of the solar irradiance variability analyzing experimental 1‐s data collected throughout a year at six PV plants, totaling 18 MWp. Each PV plant was modeled as a first order filter function based on an analysis in the frequency domain of the irradiance data and the output power signals. An empiric expression which relates the filter parameters and the PV plant size has been proposed. This simple model has been successfully validated precisely determining the daily maximum output power fluctuation from incident irradiance measurements. Copyright © 2011 John Wiley & Sons, Ltd.     

Environmental benefits of parking‐integrated photovoltaics: a 222 kWp experience

The life cycle assessment of a grid‐connected, parking integrated, 222 kW_p cadmium telluride photovoltaic system has been performed. The system was built at the University of Murcia and has been monitored for 2.5 years (sampling data every 5 min). The detailed material inventory, the energy embedded in the system, the energy payback time, and the energy return factor of the facility have been obtained and are 6.31 TJ equivalent primary energy, 2.06 and 12.16years, respectively. The average performance ratio is 0.8 with a slight monthly variation. Additionally, the environmental benefits of the architectural integration (in this case parking integration) have been quantified using a standard methodology for the calculation of several environmental parameters. Finally, the environmental benefits of renewable energy generation because of the savings of producing the same amount of electricity by the Spanish grid system have been assessed. Copyright © 2013 John Wiley & Sons, Ltd.     

Tools for the profitability analysis of grid‐connected photovoltaics

Three key geographical zones—the Euro area, Japan and the USA—are promoting the use of grid‐connected PV through attractive financial support programmes. After a short introduction to the financial analysis of PV grid‐connected systems, this paper presents some time‐saving charts and tables intended to assess the profitability of such PV systems in respect of some of the economic measures of these programmes. These easy‐to‐use tools are addressed to PV designers and investors to help them assess their investment from an exclusively economic point of view. Decision‐makers in the developed countries may also find them of value in planning their PV support measures. Some examples demonstrate how to use these tools, taking into account different available incentives and economic forecasts. Copyright © 2002 John Wiley & Sons, Ltd.     

光伏并网对配网电压影响的PSCAD仿真与分析

讨论了光伏电池的基本工作原理和主要电气参数,PSCAD仿真软件中无光伏阵列仿真元件,根据光伏阵列的数学模型,利用PSCAD自行搭建了自定义的光伏阵列控制元件,来模拟实际的光伏阵列控制装置.基于PSCAD仿真平台搭建了光伏并网模型,通过仿真模型分析了光伏并网对配网电压的影响.     

Smoothing of PV power fluctuations by geographical dispersion

The quality and the reliability of the power generated by large grid‐connected photovoltaic (PV) plants are negatively affected by the source characteristic variability. This paper deals with the smoothing of power fluctuations because of geographical dispersion of PV systems. The fluctuation frequency and the maximum fluctuation registered at a PV plant ensemble are analyzed to study these effects. We propose an empirical expression to compare the fluctuation attenuation because of both the size and the number of PV plants grouped. The convolution of single PV plants frequency distribution functions has turned out to be a successful tool to statistically describe the behavior of an ensemble of PV plants and determine their maximum output fluctuation. Our work is based on experimental 1‐s data collected throughout 2009 from seven PV plants, 20 MWp in total, separated between 6 and 360 km. Copyright © 2011 John Wiley & Sons, Ltd.