Performance,cost and life‐cycle assessment study of hybrid PVT/AIR solar systems

An alternative and cost‐effective solution to building integrated PV systems is to use hybrid photovoltaic/thermal (PV/T) solar systems. These systems consist of PV modules with an air channel at their rear surface, where ambient air is circulating in the channel for PV cooling and the extracted heat can be used for building thermal needs. To increase the system thermal efficiency, additional glazing is necessary, but this results in the decrease of the PV module electrical output from the additional optical losses of the solar radiation. PV/T solar systems with air heat extraction have been extensively studied at the University of Patras. Prototypes in their standard form and also with low‐cost modifications have been tested, aiming to achieve improved PV/T systems. An energetic and environmental assessment for the PV and PV/T systems tested has been performed by the University of Rome ‘La Sapienza’, implementing the specific software SimaPro 5·1 regarding the life‐cycle assessment (LCA) methodology applied. In this paper electrical and thermal energy output results for PV and PV/T systems are given, focusing on their performance improvements and environmental impact, considering their construction and operation requirements. The new outcome of the study was that the glazed type PV/T systems present optimum performance regarding energy, cost and LCA results. Copyright © 2005 John Wiley & Sons, Ltd.     

PV thermal systems: PV panels supplying renewable electricity and heat

With PV Thermal panels sunlight is converted into electricity and heat simultaneously. Per unit area the total efficiency of a PVT panel is higher than the sum of the efficiencies of separate PV panels and solar thermal collectors. During the last 20 years research into PVT techniques and concepts has been widespread, but rather scattered. This reflects the number of possible PVT concepts and the accompanying research and development problems, for which it is the general goal to optimise both electrical and thermal efficiency of a device simultaneously. The aspects that can be optimised are, amongst others, the spectral characteristics of the PV cell, its solar absorption and the internal heat transfer between cells and heat‐collecting system. Another important level of optimisation is for the PVT device geometry and the integration into a system. The electricity and heat demand and the temperature level of the heat determine the choice for a certain system set‐up. With an optimal design, PVT systems can supply buildings with 100% renewable electricity and heat in a more cost‐effective manner than separate PV and solar thermal systems and thus contribute to the long‐term international targets on implementation of renewable energy in the built environment. Copyright © 2004 John Wiley & Sons, Ltd.     

Overall efficiency enhancement and cost optimization of semitransparent photovoltaic thermal air collector

A semitransparent photovoltaic‐thermal (PV/T) air collector can produce electricity and heat simultaneously. To maximize the thermal and overall efficiency of the semitransparent PV/T air collector, its availability should be maximum; this can be determined through a Markov analysis. In this paper, a Markov model is developed to select an optimized number of semitransparent PV modules in service with five states and two states by considering two parameters, namely failure rate ( λ ) and repair rate (µ). Three artificial neural network (ANN) models are developed to obtain the minimum cost, minimum temperature, and maximum thermal efficiency of the semitransparent PV/T air collector by setting its type appropriately and optimizing the number of photovoltaic modules and cost. An attempt is also made to achieve maximum thermal and overall efficiency for the semitransparent PV/T air collector by using ANN after obtaining its minimum temperature and available solar radiation.     

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.     

A comparative study on cost and life‐cycle analysis for 100 MW very large‐scale PV (VLS‐PV) systems in deserts using m‐Si,a‐Si,CdTe, and CIS modules

This paper is a study of comparisons between five types of 100 MW Very Large‐Scale Photovoltaic Power Generation (VLS‐PV) Systems, from economic and environmental viewpoints. The authors designed VLS‐PV systems using typical PV modules of multi‐crystalline silicon (12·8% efficiency), high efficiency multi‐crystalline silicon (15·8%), amorphous silicon (6·9%), cadmium tellurium (9·0%), and copper indium selenium (11·0%), and evaluated them by Life‐Cycle Analysis (LCA). Cost, energy requirement, and CO₂ emissions were calculated. In addition, the authors evaluated generation cost, energy payback time (EPT), and CO₂ emission rates. As a result, it was found that the EPT is 1·5–2·5 years and the CO₂ emission rate is 9–16 g‐C/kWh. The generation cost was 11–12 US Cent/kWh on using 2 USD/W PV modules, and 19–20 US Cent/kWh on using 4 USD/W PV module price. Copyright © 2007 John Wiley & Sons, Ltd.     

Life cycle assessment and cost analysis of very large‐scale PV systems and suitable locations in the world

Although the Sahara region has a high potential for solar power plants, the amount of installed photovoltaic (PV) system remains relatively low. This paper aims to evaluate these potentials of PV system installation in terms of environmental and economic viewpoints with indices of cost, energy, and greenhouse gas (GHG) emission. Two 1‐GW very large‐scale PV systems are simulated at Ouarzazate in Morocco and at Carpentras in France. The evaluation was performed using life cycle assessment. The lowest energy consumption and GHG emission are obtained while assuming cadmium telluride module. The result of our simulation shows that energy payback time is 0.9 years and CO₂ emission rate is 27.4 g‐CO_2‐eq/kWh in the Ouarzazate case. In cost estimation, generation costs are 0.06 USD/kWh in Ouarzazate and 0.09 USD/kWh in Carpentras in the case of 3% interest rate and 0.5 USD/W for multicrystalline silicon PV module price. In addition, by adapting 15% internal rate of return for 20% of budget, the generation costs become 0.09 USD/kWh in Ouarzazate and 0.13 USD/kWh in Carpentras under the same condition. Furthermore, the selection for suitable locations to install solar power plants in term of GHG emission is identified using geographical information system. Very high‐potential locations (lower than 38 g‐CO_2‐eq/kWh) could be obtained in North Chili, east and west Sahara, and Mexico. Copyright © 2015 John Wiley & Sons, Ltd.     

Rondine® PV concentrators: Field results and developments

In this work the experimental results of a new PV concentrator (named Rondine®) are presented. This concentrating module has a medium concentration level (∼25×) and employs silicon solar cells. The tests have been carried out in Italy and the energy production of a prototype module is compared with that produced from a tracking flat plate crystalline PV panel. The non‐imaging optics of the concentrator allows for larger angular acceptance with respect to many solar concentrators, giving us the possibility to employ trackers for standard PV modules. The first results of complete systems of 3·9 and 4·8 kW of peak power installed in summer 2008 are presented here. Copyright © 2009 John Wiley & Sons, Ltd.     

Evaluation of solar energy potential and PV module performance in the Gobi Desert of Mongolia

Here, we present the results of evaluation of solar energy potential and photovoltaic (PV) module performance from actual data measured over a period of more than 2 years in the Gobi Desert of Mongolia. To allow estimation of solar energy potentials and durability of PV systems in the Gobi Desert area, a data acquisition system, including crystalline silicon (c‐Si), polycrystalline silicon (p‐Si) modules, and two sets of precision pyranometers, thermometers, and anemometer, was installed at Sainshand City in October 2002. This system measures 23 parameters, including solar irradiation and meteorological parameters, every 10 min. High output gain was observed due to operation at extremely low ambient temperatures and the module performance ratios (PRs) were high (>1·0) in winter. In summary, the present study showed that a PV module with a high temperature coefficient, such as crystalline silicon, is advantageous for use in the Gobi Desert area. Copyright © 2006 John Wiley & Sons, Ltd.     

Exploiting existing dams for solar PV system installations

Recognizing the issues of land shortage and growing concerns for protecting natural lands, installers and project developers, with the help of scientists and engineers, continuously try to locate alternative spots for photovoltaic (PV) system installations. In the present paper a novel approach is suggested and analysed: installing solar PV systems on the downstream face of existing dams. This approach provides advantages that could favour even large‐scale systems with a capacity of several MWp. First, produced energy could cover water reservoirs' needs supporting energy‐intensive processes as water pumping and treatment in a sustainable manner. Moreover, energy provision to inhabited areas near the dams and the subsequent creation of independent mini grids could mitigate energy poverty. In the case of hydroelectric dams, the so‐created hybrid system (PV‐hydro) could become notably efficient, because the intermittent solar energy would be counterbalanced by the flexibility of hydropower. Finally, we found a notable number of existing water reservoirs in Africa that are either under‐utilized or non‐powered. That unexploited energy potential can also be amplified by PV‐system installation. The analysis included data collection from various sources. Datasets have been cross‐checked and extended in the newly created GIS‐based model, enabling the selection of the most suitable sites in South Africa, taken as case studies. Following their identification, the selected dams have been analysed using the PVGIS tool in order to estimate the annual energy production. The results have been very encouraging, indicating that PV systems on the face of dams are an advantageous option for renewable energy production. © 2015 The Authors. Progress in Photovoltaics: Research and Applications published by 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.     

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.     

Relative performance of tracking versus fixed tilt photovoltaic systems in the USA

Tracking systems can increase the amount of electricity generated by photovoltaic (PV) modules, by actively orienting each module to intercept more solar energy. We find that horizontal one‐axis tracking systems can increase PV generation by 12–25% relative to south‐facing fixed mount PV systems with 25° tilts in the contiguous USA, and two‐axis tracking systems can increase PV generation by 30–45% relative to fixed mount systems. Tracking systems increase PV generation more significantly in arid regions such as the southwest USA than in humid regions with persistent cloud cover such as the Pacific Northwest and coastal Atlantic states. We find that fixed and tracking PV systems have similar interannual variability in their generation profiles, and this variability is primarily driven by project location. Tracking PV projects cost more than fixed tilt systems, per unit capacity, and we explore how much more tracking projects could cost while generating similar levelized costs of energy as fixed tilt systems. We define this as the breakeven additional cost of tracking and find that it is primarily driven by three factors: (i) regional tracking performance, (ii) fixed tilt system costs that tracking projects compete against, and (iii) additional tracking operation and maintenance costs. Using this framework, we explore the relative competitiveness of tracking systems for a range of fixed and tracking PV prices and evaluate how tracking competitiveness varies by region. Copyright © 2013 John Wiley & Sons, Ltd.     

Update of environmental indicators and energy payback time of CdTe PV systems in Europe

Thin film technologies undergo rapid developments for increasing the module efficiencies and improving production technologies or recycling processes which affect the environmental profile of PV power generation and Energy Payback Time (EPBT). Therefore, especially for the Life Cycle Assessment (LCA) of product systems with short development cycles, the environmental profiles need to be frequently updated to ensure the representativeness and validity of the environmental assessment. The update of LCA results in this paper demonstrates that considerable improvements were reached in the environmental profile of CdTe PV power and EPBT over the last four years. Depending on the location of installation in Europe, the corresponding Greenhouse Gas (GHG) emissions of PV power for ground mounted power plants are between 19 and 30 g CO₂‐equiv./kWh and between 0.7 and 1.1 years in terms of EBPT. Furthermore, for the first time, the environmental impacts due to an already applied recycling procedure of CdTe modules and it's relative contribution to the CdTe PV life cycle has been investigated. This paper presents the main approach, results and outcomes of the study. Copyright © 2011 John Wiley & Sons, Ltd.     

Simplified life-cycle analysis of PV systems in buildings: present situation and future trends

The integration of photovoltaic (PV) systems in buildings shows several advantages compared to conventional PV power plants. The main objectives of the present study are the quantitative evaluation of the benefits of building-integrated PV systems over their entire life-cycle and the identification of best solutions to maximize their energy efficiency and CO₂ mitigation potential. In order to achieve these objectives, a simplified life-cycle analysis (LCA) has been carried out. Firstly, a number of existing applications have been studied. Secondly, a parametric analysis of possible improvements in the balance-of-system (BOS) has been developed. Finally, the two steps have been combined with the analysis of crystalline silicon technologies. Results are reported in terms of several indicators: energy pay-back time, CO₂ yield and specific CO₂ emissions. The indicators show that the integration of PV systems in buildings clearly increases the environmental benefits of present PV technology. These benefits will further increase with future PV technologies. Future optimized PV roof-integrated systems are expected to have an energy pay-back time of around 1·5 years (1 year with heat recovery) and to save during their lifetime more than 20 times the amount of CO₂ emitted during their manufacturing (34 times with heat recovery). © 1998 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.     

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.     

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.     

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.     

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.     

Life cycle assessment of thin‐film GaAs and GaInP/GaAs solar modules

This paper presents an environmental comparison based on life cycle assessment (LCA) of the production under average European circumstances and use in The Netherlands of modules based on two kinds of III–V solar cells in an early development stage: a thin‐film gallium arsenide (GaAs) cell and a thin‐film gallium‐indium phosphide/gallium arsenide (GaInP/GaAs) tandem cell. A more general comparison of these modules with the common multicrystalline silicon (multi‐Si) module is also included. The evaluation of the both III–V systems is made for a limited industrial production scale of 0·1 MW_p per year, compared to a scale of about 10 MW_p per year for the multi‐Si system. The here considered III–V cells allow for reuse of the GaAs wafers that are required for their production. The LCA indicates that the overall environmental impact of the production of the III–V modules is larger than the impact of the common multi‐Si module production; per category their scores have the same order of magnitude. For the III–V systems the metal‐organic vapour phase epitaxy (MOVPE) process is the main contributor to the primary energy consumption. The energy payback times of the thin‐film GaAs and GaInP/GaAs modules are 5·0 and 4·6 years, respectively. For the multi‐Si module an energy payback time of 4·2 years is found. The results for the III–V modules have an uncertainty up to approximately 40%. The highly comparable results for the III–V systems and the multi‐Si system indicate that from an environmental point of view there is a case for further development of both III–V systems. Copyright © 2006 John Wiley & Sons, Ltd.