Lessons from a PV pumping programme in south Morocco

This paper presents the experience of a PV pumping project being carried‐out in the South of Morocco since 1997. At present, the project has reached 18 villages, affecting 15 000 people. Total involved photovoltaic power is 46 kW_p, and the total volume of pumped water since the installation of the systems approaches 0.7 × 10⁶ m³. About half the PV systems are based on dedicated inverters, while the rest are based on standard frequency drivers. Both perform very similarly in terms of both efficiency and reliability. Wells have been selected to provide good water taste, and pumped water is distributed to all the individual houses. Average daily water consumption in summer varies from 13 to 50 litres per person depending on ease of water access and ‚urban proximity’︁. The maintenance infrastructure is based on an agreement between the European supplier company and a local NGO, which is in charge of all the local organizations. Copyright © 2005 John Wiley & Sons, Ltd.     

The effect of low insolation conditions and inverter oversizing on the long‐term performance of a grid‐connected photovoltaic system

The performance of a roof mounted grid‐connected photovoltaic (PV) system in Northern Ireland was monitored over 3 years on annual, seasonal and monthly bases. The overall system performance was adversely affected by low insolation conditions; 19% of total incident insolation was absorbed at irradiance level below 200 W/m² and 67% below 600 W/m², only 6·2% above 900 W/m². In summer and winter, the PV and system efficiencies were 9·0 and 8·5%, and 7·8 and 7·5%, respectively and inverter efficiencies were 86·8 and 85·8%, respectively. The inverter for this particular system was oversized; 77% of the total DC energy produced when inverter's operating load was 50% of its rated capacity. The annual average monthly system performance ratio (PR) was 0·61 with seasonal variation 0·59 to 0·63. The average monthly PV, system and inverter efficiencies over the whole monitored period were 8·8, 7·6 and 86·8%, respectively. The main losses of the system were inverter DC/AC conversion loss, inverter threshold loss and low insolation loss. Copyright © 2007 John Wiley & Sons, Ltd.     

Optimal sizing and life cycle assessment of residential photovoltaic energy systems with battery storage

This paper presents the optimal sizing and life cycle assessment of residential photovoltaic (PV) energy systems. The system consists of PV modules as the main power producer, and lead–acid batteries as the medium of electricity storage, and other essential devices such as an inverter. Five‐parameter analytic PV cell model is used to calculate the energy production from the modules. Electrical needs for a family living under normal conditions of comfort are modelled and used within simulation of the system performance, with an average daily load of approximately 9·0 kWh. The system's performance simulations are carried out with typical yearly solar radiation and ambient temperature data from five different sites in Turkey. The typical years are selected from a total of 6 years data for each site. The life cycle cost of the PV system is analysed for various system configurations for a 20‐year system life. The role of the batteries in PV energy systems are analysed in terms of the cost and power loss. The system performance is analysed as a function of various parameters such as energy production and cost. It is shown that these change substantially for different system configurations and locations. The life cycle assessment of the energy system described was also carried out to determine the environmental impact. It was found that, with the conservative European average electricity mix, energy pay back time (EPBT) is 6·2 years and CO₂ pay back time is 4·6 years for the given system. Copyright © 2007 John Wiley & Sons, Ltd.     

Field experience with large‐scale implementation of domestic PV systems and with large PV systems on buildings in Japan

Under the auspices of the New Sunshine Program and continuous R&D programs by the New Energy Development and Industrial Technology Organization (NEDO), the authors have been implementing a measurement and evaluation program for photovoltaic (PV) systems since the fiscal year 1997. In this program, a total of 100 residential PV systems, equipped with special data acquisition systems, have been set up over seven years. The purpose of this study was to clarify the operating performance of the grid‐connected PV systems on the rooftops of residential houses in Japan and to develop a simulation methodology in order to estimate the electricity generation and costs in the actual housing environment. The validity of the simulation methodology was assessed by using the actually monitored data from some hundreds residential PV systems. Simulation results were also used to optimize the PV system design as well as to diagnose their operating conditions. The mean value of the final annual yield was around 1000 h; 975 h in 2000, 982 h in 2001 and 975 h in 2002, and the mean value of the performance ratio was over 70%; 73·3% in 2000, 71·8% in 2001 and 72·5% in 2001. Copyright © 2004 John Wiley & Sons, Ltd.     

Energy payback time of grid connected PV systems: Comparison between tracking and fixed systems

A review of existing studies about life cycle assessment (LCA) of PV systems has been carried out. The data from this review have been completed with our own figures in order to calculate the energy payback time (EPBT) of double and horizontal axis tracking and fixed systems. The results of this metric span from 2 to 5 years for the latitude and global irradiation ranges of the geographical area comprised between –10° to 10° of longitude, and 30° to 45° of latitude. With the caution due to the uncertainty of the sources of information, these results mean that a grid connected PV system (GCPVS) is able to produce back the energy required for its existence from 6 to 15 times during a life cycle of 30 years. When comparing tracking and fixed systems, the great importance of the PV generator makes advisable to dedicate more energy to some components of the system in order to increase the productivity and to obtain a higher performance of the component with the highest energy requirement. Both double axis and horizontal axis trackers follow this way, requiring more energy in metallic structure, foundations and wiring, but this higher contribution is widely compensated by the improved productivity of the system. Copyright © 2008 John Wiley & Sons, Ltd.     

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.     

A novel analytical model for determining the maximum power point of thin film photovoltaic module

Achieving the maximum power output from photovoltaic (PV) modules is indispensable for the operation of grid‐connected PV power systems under varied atmospheric conditions. In recent years, the study of PV energy for different applications has attracted more and more attention because solar energy is clean and renewable. We propose an efficient direct‐prediction method to enhance the utilization efficiency of thin film PV modules by tackling the problem of tracking time and overcoming the difficulty of calculation. The proposed method is based on the p–n junction recombination mechanism and can be applied to all kinds of PV modules. Its performance is not influenced by weather conditions such as illumination or temperature. The experimental results show that the proposed method provides high‐accuracy estimation of the maximum power point (MPP) for thin film PV modules with an average error of 1.68% and 1.65% under various irradiation intensities and temperatures, respectively. The experimental results confirm that the proposed method can simply and accurately estimate the MPP for thin film PV modules under various irradiation intensities and temperatures. In future, the proposed method will be used to shed light on the optimization of the MPP tracking control model in PV systems. Copyright © 2012 John Wiley & Sons, Ltd.     

Experience with PV‐diesel hybrid village power systems in Southern Morocco

In October 2002, under the auspices of Spanish Cooperation, a pilot electrification project put into operation two centralised PV‐diesel hybrid systems in two different Moroccan villages. These systems currently provide a full‐time energy service and supply electricity to more than a hundred of families, six community buildings, street lighting and one running water system. The appearance of the electricity service is very similar to an urban one: one phase AC supply (230 V/50 Hz) distributed up to each dwelling using a low‐voltage mini‐grid, which has been designed to be fully compatible with a future arrival of the utility grid. The management of this electricity service is based on a ‘fee‐for‐service’ scheme agreed between a local NGO, partner of the project, and electricity associations created in each village, which are in charge of, among other tasks, recording the daily energy production of systems and the monthly energy consumption of each house. This register of data allows a systematic evaluation of both the system performance and the energy consumption of users. Now, after 4 years of operation, this paper presents the experience of this pilot electrification project and draws lessons that can be useful for designing, managing and sizing this type of small village PV‐hybrid system. Copyright © 2007 John Wiley & Sons, Ltd.     

Five years of operating experience at a large,utility‐scale photovoltaic generating plant

Tucson Electric Power Company (TEP), headquartered in Tucson, AZ, currently has nearly 5·0 MWdc of utility‐scale grid‐connected photovoltaic (PV) systems installed in its service territory. These systems have been installed through a multiyear, pay‐as‐you‐go development of renewable energy, with kWhac energy production as a key program measurement. This PV capacity includes a total of 26 crystalline silicon collector systems, each rated at 135 kWdc for a total of 3·51 MWdc, that have been installed at the Springerville, AZ generating plant by TEP making this one of the largest PV plants in the world. This facility started operations in 2001 and recently passed the 5‐year milestone of continuous operations. These systems were installed in a standardized, cookie‐cutter approach whereby each uses the same array field design, mounting hardware, electrical interconnection, and inverter unit. This approach has allowed TEP to achieve a total installed system cost of $5·40/Wdc and a TEP‐calculated levelized energy cost of $0·062/kWhac for PV electrical generation. This paper presents an assessment of operating experience including performance, costs, maintenance, and plant operation over this 5‐year period making this one of the most detailed and complete databases of utility‐scale PV systems available to the US DOE Program. Published in 2007 by John Wiley & Sons, Ltd.     

Sustainability of PV water pumping programmes: 12‐years of successful experience

This paper presents the key points to assure the sustainability of a PV water pumping program that has supplied 5 million m³ of water in the last 12 years to approximately 40 000 people. Key aspects for success have been the proper consideration of user's priorities, rigorous technical quality assurance, and maintenance structure set up. The present work mainly focuses on the maintenance structure aspects: some results to characterize the maintenance carried out, such as the mean time to failure parameter (MTTF) or the failure typology, are shown. Copyright © 2010 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.     

Operational performance of grid‐connected PV systems on buildings in Germany

This paper presents operational performance results of grid‐connected PV systems in Germany, as collected and elaborated for the Photovoltaic Power Systems Programme (PVPS) of the International Energy Agency (IEA). Performance ratios obtained from 235 PV installations in Germany and from 133 PV plants in other countries are compared and discussed. For Germany, a significant rise in PV system performance and reliability was observed for new PV installations due to higher component efficiencies (e.g., inverter) and increased availabilities. There is a lack of long‐term experience in performance and reliability of PV systems, owing to the absence of monitoring programmes. As an outcome of IEA PVPS collaborative work, Task 2 provides reliable and worldwide monitoring performance data and results (www.task2.org). Technical and operational data is available for system planning and comparison, for teaching and training purposes as well as for future developments of financing schemes (e.g., feed‐in‐tariffs) in order to stimulate the PV market. Copyright © 2004 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.     

Electrotechnical requirements for PV on buildings

World‐wide the number of grid‐connected PV systems is growing fast, especially in the built environment. In order to assure the quality and energy output of these systems, a number of electrotechnical requirements need to be fulfilled, at both component and system levels. In addition requirements with respect to electrical safety need to be met. Part of these requirements are covered by international standards, especially with respect to the PV modules. A number of standards is still under development. In the area of systems and utility interfacing local codes are still in use. These local codes differ significantly from country to country. Copyright © 2004 John Wiley & Sons, Ltd.     

Solar irradiation and PV module temperature dispersion at a large‐scale PV plant

When evaluating the performance of a photovoltaic (PV) system, it is extremely important to correctly measure the plant operating conditions: incident irradiation and cell temperature. At large‐size PV plants, the possible dispersion of the plant operating conditions may affect the representativeness of the values measured at one single point. The available literature contains many observations on irradiance dispersion (typically associated to high temporal resolution experiments) and its effects on the PV power output (unexpected power transients, power fluctuations, etc.). However no studies have been made on the long‐term energy‐related effects of geographic dispersion of solar irradiation, which could affect, for example, to the uncertainty in determining energy performance indexes like PR. This paper analyses the geographical dispersion in the PV operating conditions observed at low temporal resolutions (day, month and year) at two PV plants located, respectively, in the south of Portugal and the north of Spain. It shows that daily irradiation deviations are significantly higher than is commonly supposed. Furthermore, once the measurement points are a certain distance apart (a few hundred metres), the deviations in irradiation appear to be independent of distance. This could help to determine how many irradiance sensors to install in order to reduce uncertainty. Daily mean temperature differences between different points at a large‐scale PV plant range from 1 to 7 K and are not related to the distance between measurement points. Copyright © 2014 John Wiley & Sons, Ltd.     

PV water pumping systems based on standard frequency converters

Standard frequency converters (FCs) are evaluated in this work as a universal solution for photovoltaic (PV) water pumping systems. FCs can be connected directly to a PV generator to power centrifugal submersible pumps driven by three‐phase asynchronous induction motors. In comparison with dedicated products, the use of standard FCs and centrifugal motopumps encompasses several advantages: power range, broad range of products and technological independence. This paper describes the main rules to implement standard FCs in PV pumping systems, and presents a model to estimate its performance from standard pumps manufacturers' data. The experimental validation of the model is also presented. Copyright © 2003 John Wiley & Sons, Ltd.     

Technical and economic analysis of grid‐connected PV systems by means of simulation

Research on monitored grid‐connected PV systems can lead to an improved performance of PV systems. This view is based on monitoring results from PV systems in Western Europe which lag behind the expected values. However, current methods for analysing these systems do not allow to investigate the potential system efficiency improvement on the basis of field experience. Hence, we have developed a method for analysing monitored grid‐connected PV systems which meets this need. In this method the common technical approach to analysing PV systems is broadened with an economic assessment. First an energy loss analysis of the PV system is made using its monitored data. In our analysis the energy loss effects in the PV system are split up by simulation. This provides a profound insight into the actual performance of the system. Next, measures to enhance the performance of the system are identified. The costs involved to improve the performance are analysed. Finally, the cost‐effectiveness of the potential improvements is calculated. In this paper we will present our method TEAMS. Although we will not formulate strict rules, we will provide a well‐defined frame and structure for the application of the TEAMS method. It is shown that applying TEAMS contributes to improved transparency in the evaluation of monitored grid‐connected PV systems. Copyright © 1999 John Wiley & Sons, Ltd.     

On the calculation of energy produced by a PV grid‐connected system

This study develops a proposal of method of calculation useful to estimate the energy produced by a PV grid‐connected system making use of irradiance‐domain integrals and definition of statistical moment. Validation against database of real PV plants performance data shows that acceptable energy estimation can be obtained with first to fourth statistical moments and some basic system parameters. This way, only simple calculations at the reach of pocket calculators, are enough to estimate AC energy. Copyright © 2006 John Wiley & Sons, Ltd.     

The energy payback time of advanced crystalline silicon PV modules in 2020: a prospective study

The photovoltaic (PV) market is experiencing vigorous growth, whereas prices are dropping rapidly. This growth has in large part been possible through public support, deserved for its promise to produce electricity at a low cost to the environment. It is therefore important to monitor and minimize environmental impacts associated with PV technologies. In this work, we forecast the environmental performance of crystalline silicon technologies in 2020, the year in which electricity from PV is anticipated to be competitive with wholesale electricity costs all across Europe. Our forecasts are based on technological scenario development and a prospective life cycle assessment with a thorough uncertainty and sensitivity analysis. We estimate that the energy payback time at an in‐plane irradiation of 1700 kWh/(m² year) of crystalline silicon modules can be reduced to below 0.5 years by 2020, which is less than half of the current energy payback time. Copyright © 2013 John Wiley & Sons, Ltd.     

Performance of household grid‐connected PV system in Thailand

This paper presents the performance of a 2·88 kW_p household grid‐connected PV system installed in a house at Bangkok. This was one of the 10 houses identified for a household rooftop PV grid‐connected demonstration project by the Electricity Generating Authority of Thailand in 1997. Data measured over 12 months was used to estimate the PV array output, inverter output, inverter efficiency, system efficiency, yields (reference yield, array yield, final yield) performance ratio (PR) and the losses. The variations of these parameters over time indicate that the yields are high during June and July in Bangkok. The annual final yield and the average performance ratio were found to be 1166 kW h/kW_p and 0ċ73 respectively. The monthly highest final yield was 129 kW h/kW_p during June and July. The inverter efficiency was greater than 80% throughout the study period and the maximum system efficiency was 5·4%. The result of the study indicates that the system installed in Bangkok worked satisfactorily. Following the success of the demonstration project, a second phase of 50 households has recently been initiated. Copyright © 2003 John Wiley & Sons, Ltd.