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.     

An international overview of promotion policies for grid‐connected photovoltaic systems

The design of effective future promotion polices for photovoltaics (PV) needs the lessons learned from past experiences. The major objective of this study is to analyse the major PV markets over time to identify the effects caused by the two main promotion schemes: the achievement of economic profitability by means of Feed‐in Tariffs (FiTs) and the use of the Willingness‐to‐Pay (WTP) in investment subsidies. For this purpose, indicators have been defined that characterise the promotion policies for grid‐connected PV since the middle of the 1990s: (i) dissemination effectiveness, (ii) costs for the public, (iii) development of system prices over time, (iv) consumer's WTP and (v) profitability for the consumer. The following are the major conclusions of this analysis. (i) If financial incentive programmes are implemented over a reasonable time frame, they work with respect to both significant price decreases as well as increases in quantities. (ii) FiT schemes and also investment subsidies and combined concepts are able to increase the market penetration and the diffusion of PV systems. They are especially relevant in the context of optimising the own use of PV electricity generated. (iii) Regarding the design of promotion systems, it is important that on the one hand, they consider customers WTP, and on the other hand, they include a well‐defined dynamic component, which considers the effects of Technological Learning. In this context, capacity corridors, as were introduced in Germany, are essential. This tool allows predictable legislations and the correction of incentive payments without generating boom and bust cycles. Copyright © 2012 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.     

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.     

Operational results of grid‐connected photovoltaic system with different inverter's sizing factors (ISF)

This paper presents operational results of a 11·07 kWp grid‐connected photovoltaic system. This system is made up by eight groups with different relationships between the inverter's rated power and the PV generator's maximum power (P / P) . The obtained results led to the verification that the different studied relationships, P / P between 55 and 102%, do not affect significantly the final yields (Y_F). Copyright © 2006 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.     

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.     

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.     

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.     

An investigation into hot‐spots in two large grid‐connected PV plants

This paper details an investigation into the appearance of hot‐spots in two large grid‐connected photovoltaics (PV) plants, which were detected after the visual inspection of trackers whose energy output was decreasing at anomalous rate. Detected hot‐spots appeared not only in the solar cells but also in resistive solder bonds (RSB) between cells and contact ribbons. Both types cause similar irreversible damage to the PV modules, but the latter are the main responsible for the detected decrease in energy output, which was confirmed in an experimental testing campaign. The results of this investigation, for example, how hot‐spots were detected or their impact on the output power of PV modules, may be of interest for the routine maintenance of large grid‐connected PV plants. Copyright © 2008 John Wiley & Sons, Ltd.     

The character of power output from utility‐scale photovoltaic systems

Power produced by utility‐scale solar photovoltaic (PV) systems has fluctuations on both short and long time scales. Power spectral density (PSD) analysis provides information on the character of these power fluctuations. Examination of the correlation and step size of the power output between several PV sites within a multi‐site system allows assessment of geographic diversification for addressing intermittency. Both techniques provide insight into the characteristics of firm power and/or demand response required to accommodate large‐scale PV deployment. Copyright © 2007 John Wiley & Sons, Ltd.     

Technical and economic performance analysis of large‐scale ground‐mounted PV plants in Italian context

During the last decade, the market penetration of photovoltaic (PV) technology has been increased tremendously worldwide. In the EU context, following the quick development in German and Spanish PV sector, Italy is currently one of the most interesting market. In view of these facts, it is strategic to perform detailed technical and economic analyses to establish energy performances and profitability of the PV plants, depending on their configurations. In particular, in addition to the selection of main components, such as inverters and modules, which are now characterized, on average, by good performance levels, the debate on the support structures is still open. In detail, the choice may fall, for example, on traditional fixed structures or on one/two axis tracking systems, that could ensure best productivity per unit of power, but also are typically characterized by higher complexity and land‐occupation factors than the first ones. The purpose of this work is to carry out performance analyses on the most widespread plant configurations, taking into account different Italian climatic contexts, considering technical, energetic, and economic points of view. With this aim, different types of components (modules and inverters) and ground‐mounting structures (fixed, one‐axis, two‐axis) have been evaluated. Subsequently, their obtainable performances have been estimated in three different locations (Milano, Roma, Palermo) that have been considered representative of average irradiation levels available in Italy. Analyses have been carried out by computer simulations, through two consequent levels of detail, highlighting the main performance influence‐factors. In conclusion, the final profitability of each analyzed configuration has been evaluated, giving a reliable indication on their effective economic advantages. Copyright © 2010 John Wiley & Sons, Ltd.     

SGDD: self‐managed grid‐based data dissemination protocol for mobile sink in wireless sensor network

The reduction of energy consumption in order to increase network lifetime is one of the most major challenges in the design of wireless sensor networks. During data dissemination, the sensors that are located in the sink's neighborhood are responsible to relay data to the other nodes; hence, their energy is exhausted expeditiously. Therefore, the idea of utilizing mobile sinks can be so advantageous to decrease energy consumption during data dissemination process. In this paper, we propose self‐managed grid‐based data disseminating protocol for mobile sink in wireless sensor networks by using the idea of constructing a virtual grid. In self‐managed grid‐based data disseminating protocol, sink and nodes map their geographical position to a virtual location. In order to increase the performance, we have employed a cell head for each grid cell. Cell heads are selected based on two parameters, centralization and residual energy. Our data dissemination protocol is simple and has low overhead to construct and maintain. Also, we have presented a new method for sink location update, which leads to the least cost in data transfer. Simulation results illustrate that by utilizing hierarchical functionality and determining an optimal size for grid cells, energy consumption is decreased, which leads to increasing network lifetime. Copyright © 2015 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‐tracking PV plants in Navarra: A 10 MW assessment

Currently, the know‐how and experience concerning the behavior and reliability of large tracking photovoltaic (PV) plants is scarce. Information such as the availability rate is rarely known. Acciona Solar PV plants installed in Navarra (Spain) in the frame of the Spanish utility grid constitute a representative source of information. The scope of this study is to analyze in detail the behavior along 2006 of six of these plants, located in Arguedas (two plants of a rated nominal power of 940 kWp and 2·1 MWp, respectively), Sesma (1·12 MWp), Cintruénigo (1·44 MWp), Rada (1·78 MWp), and Castejón (2·64 MWp). In our analysis, the influence of each type of energy loss affecting the plants has been quantified; and the advantages of dedicating human resources to the surveillance and maintenance of a limited number of generators have been stated. Thanks to the work of the operators, the plants registered mean availability rates above 99·7%. Copyright © 2009 John Wiley & Sons, Ltd.     

Constrained parity testing

A generalized testing technique called constrained parity testing is presented for detecting multiple stuck-at faults in any single-output irredundant combinational network by verifying the subparities of the network. Implementation independent testability conditions are established for single- and multiple-input stuck-at faults. A spanning parity signature (SPS) is introduced to detect vacuous faults, which include all the input stuck-at faults and a majority of all other multiple stuck-at faults. The SPS is considered for testing all stuck-at faults in networks with small numbers of fanout lines, and a method of deriving tests for nonvacuous faults is proposed. For networks with large fanouts, a hybrid scheme by combining with syndrome testing is suggested to eliminate or reduce the need for expensive fault simulation. The proposed technique is a theoretical generalization of many existing methods and offers advantages such as versatility, flexibility, low test volume, low test time, high fault coverage, and reduced fault simulation and test generation costs.     

Performance of a mesoscale liquid fuel‐film combustion‐driven TPV power system

Combustion‐driven thermophotovoltaic (TPV) systems have obtained increasing attention in recent decades, but most studies have focused on developing narrowband photovoltaic cells and selective emitters. In terms of the heat source, conventional combustion configurations and light gaseous fuels are extensively utilized in macro‐ or meso‐scale TPV power systems to simplify thermal management and mechanical fabrication. As far as miniaturization is concerned, however, fuelling these systems with liquid hydrocarbons would provide inherent advantages of high energy density and low volatility. Liquid fuels also promise easy and safe fuel recharging for small‐scale power systems. In this paper, a central porous‐medium combustor was employed in a small scale TPV power system. The combustor incorporated an emitting chamber wall and a heat recuperator. The radiant efficiency and overall efficiency were compared using different liquid hydrocarbon fuels in the system. The electric output characteristics of the combustion driven TPV system have been investigated to demonstrate the feasibility of a GaSb cell‐based TPV power system and to provide design guidance for mesoscale liquid‐burning TPV systems. Copyright © 2008 John Wiley & Sons, Ltd.     

Soiling and other optical losses in solar‐tracking PV plants in navarra

Field data of soiling energy losses on PV plants are scarce. Furthermore, since dirt type and accumulation vary with the location characteristics (climate, surroundings, etc.), the available data on optical losses are, necessarily, site dependent. This paper presents field measurements of dirt energy losses (dust) and irradiance incidence angle losses along 2005 on a solar‐tracking PV plant located south of Navarre (Spain). The paper proposes a method to calculate these losses based on the difference between irradiance measured by calibrated cells on several trackers of the PV plant and irradiance calculated from measurements by two pyranometers (one of them incorporating a shadow ring) regularly cleaned. The equivalent optical energy losses of an installation incorporating fixed horizontal modules at the same location have been calculated as well. The effect of dirt on both types of installations will accordingly be compared. 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.