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.     

Energy,cost and LCA results of PV and hybrid PV/T solar systems

Hybrid photovoltaic/thermal (PV/T) solar systems provide a simultaneous conversion of solar radiation into electricity and heat. In these devices, the PV modules are mounted together with heat recovery units, by which a circulating fluid allows one to cool them down during their operation. An extensive study on water‐cooled PV/T solar systems has been conducted at the University of Patras, where hybrid prototypes have been experimentally studied. In this paper the electrical and thermal efficiencies are given and the annual energy output under the weather conditions of Patras is calculated for horizontal and tilted building roof installation. In addition, the costs of all system parts are included and the cost payback time is estimated. Finally, the methodology of life cycle assessment (LCA) has been applied to perform an energy and environmental assessment of the analysed system. The goal of this study, carried out at the University of Rome ‘La Sapienza’ by means of SimaPro 5·1 software, was to verify the benefits of heat recovery. The concepts and results of this work on energy performance, economic aspects and LCA results of modified PV and water‐cooled PV/T solar systems, give a clear idea of their application advantages. From the results, the most important conclusion is that PV/T systems are cost effective and of better environmental impact compared with standard PV modules. Copyright © 2005 John Wiley & Sons, Ltd.     

Life cycle analysis of organic photovoltaic technologies

Organic solar cells, both in the hybrid dye sensitized technology and in the full organic polymeric technology, are a promising alternative that could supply solar electricity at a cost much lower than other more conventional inorganic photovoltaic technologies. This paper presents a life cycle analysis of the laboratory production of a typical bulk heterojunction organic solar cell and compares this result with those obtained for the industrial production of other photovoltaic technologies. Also a detailed material inventory from raw materials to final photovoltaic module is presented, allowing us to identify potential bottlenecks in a future supply chain for a large industrial output. Even at this initial stage of laboratory production, the energy payback time and CO₂ emission factor for the organic photovoltaic technology is of the same order of other inorganic photovoltaic technologies, demonstrating that there is plenty of room for improvement if the fabrication procedure is optimized and scaled up to an industrial process. Copyright © 2010 John Wiley & Sons, Ltd.     

Façade–integrated photovoltaics: a life cycle and performance assessment case study

The Solaire Building has the first façade building‐integrated photovoltaic (BIPV) array in New York City. This paper presents the life cycle impacts of the Solaire BIPV and extrapolates its performance to other façade systems. Engineering diagrams, detailed material inventories and 5 years of irradiation and actual performance data in 15‐min intervals offer insights into current BIPV construction and performance. The Solaire BIPV employs waste‐stream monocrystalline silicon wafers. Correspondingly, zero energy input was allocated to this BIPV from wafer production, resulting to a very low energy payback time (EPBT) and global warming potential burden (0.8 years and −10.2 g CO₂/kWh, respectively). A negative EPBT results from subtracting the impact of the thermally and structurally equivalent concrete and brick wall that the BIPV array replaced. Data from current photovoltaic‐dedicated Si wafer supply were also used; these resulted with an EPBT of 3.8 years and a global warming potential of 61 g CO₂/kWh. The performance ratio and EPBT of the Solaire system were compared with those in the International Energy Agency Photovoltaic Power Systems Task 2 inventory database. The drawback of façade BIPV is its vertical orientation, receiving lower incident irradiation than rooftop and ground installations. Nevertheless, BIPV offers two main advantages over such installations: it does not require any ‘virgin’ land for its operation, and it replaces structural units, thus avoiding the cost, embodied energy and corresponding emissions related to those. We detail herein how the replacement of traditional cladding materials can offset the performance drawback of BIPV, in terms of environmental burden and EPBT. Copyright © 2012 John Wiley & Sons, Ltd.     

A life cycle assessment of perovskite/silicon tandem solar cells

Given the rapid progress in perovskite solar cells in recent years, perovskite/silicon (Si) tandem structure has been proposed to be a potentially cost‐effective improvement on Si solar cells because of its higher efficiency at a minimal additional cost. As part of the evaluation, it is important to conduct a life cycle assessment on such technology in order to guide research efforts towards cell designs with minimum environmental impacts. Here, we carry out a life cycle assessment to assess global warming, human toxicity, freshwater eutrophication and ecotoxicity and abiotic depletion potential impacts and energy payback time associated with three perovskite/Si tandem cell structures using silver (Ag), gold (Au) and aluminium (Al) as top electrodes compared with p–n junction and hetero‐junction with intrinsic inverted layer Si solar cells. It was found that the replacement of the metal electrode with indium tin oxide/metal grid in the tandem cell reduces the environmental impacts significantly compared with the perovskite cell. For all the impacts assessed, we conclude that the perovskite/Si tandem using Al as top electrode has better environmental outcomes, including energy payback time, when compared with the other tandem structures studied. Use of Al in preference to noble metals for contacts, Si p–n junction in preference to intrinsic inverted layer and the avoidance of 2,20,7,70‐tetrakis(N ,N‐di‐p‐methoxyphenylamine)9,90‐spirobifluorene (Spiro‐OMeTAD) are environmentally beneficial. The key result found of this work is that the most important factor for the better environmental impacts of these tandem solar cells is the transparency and electrical conductivity of the perovskite layer after it fails. Copyright © 2017 John Wiley & Sons, Ltd.     

Life‐cycle greenhouse gas emissions and energy payback time of current and prospective silicon heterojunction solar cell designs

Silicon heterojunction (SHJ) cells offer high efficiencies and several advantages in the production process compared to conventional crystalline silicon solar cells. We performed a life‐cycle assessment to identify the greenhouse gas (GHG) footprint, energy payback time (EPBT) and cumulative energy demand of four different SHJ solar cell designs. We analyse these environmental impacts for cell processing and complete systems for both current and prospective designs. On the basis of in‐plane irradiation of 1700 kWh/m², results for current designs show that life‐cycle GHG emissions could be 32 gCO₂‐eq/kWh for complete SHJ photovoltaic (PV) systems (module efficiencies of 18.4%), compared with 38 gCO₂‐eq/kWh for conventional monocrystalline silicon systems (module efficiency of 16.1%). The EPBT of all SHJ designs was found to be 1.5 years, compared with 1.8 years for the monocrystalline PV system. Cell processing contributes little (≤6%) to the overall environmental footprint of SHJ PV systems. Among cell processing steps, vacuum based deposition contributes substantially to the overall results, with 55–80%. Atomic layer deposition of thin films was found to have a significantly lower environmental footprint compared to plasma enhanced chemical vapour deposition and sputtering. Copper‐based compared with silver‐based metallization was shown to reduce the impact of this processing step by 74–84%. Increases in cell efficiency, use of thin silicon wafers and replacement of silver‐based with copper‐based metallization could result in life‐cycle GHG emissions for systems to be reduced to 20 gCO₂‐eq/kWh for SHJ systems and 25 gCO₂‐eq/kWh for monocrystalline system, while EPBT could drop to 0.9 and 1.2 years, respectively. Copyright © 2014 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 greenhouse gas effects of introducing nano‐crystalline materials in thin‐film silicon solar cells

Solar PV is widely considered as a “green” technology. This paper, however, investigates the environmental impact of the production of solar modules made from thin‐film silicon. We focus on novel applications of nano‐crystalline Silicon materials (nc‐Si) into current amorphous Silicon (a‐Si) devices. Two nc‐Si specific details concerning the environmental performance can be identified, when we want to compare to a‐Si modules. First, in how far the extra (and thicker) silicon layer (s) affects upstream material requirements and energy use. Second, in how far depositing an extra silicon layer may increase emissions of greenhouse gases as additional emissions of Fluor gases (F‐gases) are associated to this step. The much larger global warming potential of F‐gases (17 200–22 800 times that of CO₂) may lead to higher environmental burdens. To date, no study has yet analyzed the effect of F‐gas usage on the environmental profile of thin‐film silicon solar modules. We performed a life‐cycle assessment (LCA) to investigate the current environmental usefulness of pursuing this novel micromorph concept. The switch to the new micromorph technology will result in a 60–85% increase in greenhouse gas emissions (per generated kWh solar electricity) in case of NF₃ based clean processing, and 15–100% when SF₆ is used. We conclude that F‐gas usage has a substantial environmental impact on both module types, in particular the micromorph one. Also, micromorph module efficiencies need to be improved from the current 8–9% (stabilized efficiency) toward 12–16% (stab. eff.) in order to compensate for the increased environmental impacts. Copyright © 2010 John Wiley & Sons, Ltd.     

A comparative human health,ecotoxicity, and product environmental assessment on the production of organic and silicon solar cells

A life cycle assessment case study involving organic photovoltaic technology using phenyl‐C₆₁‐butyric acid methyl ester and poly(3‐hexylthiophene) is presented. Although solar technology converts freely available solar radiation into more useful forms of energy, potential environmental impacts can occur during the life cycle of the product. A cradle‐to‐gate life cycle assessment is completed, comparing organic solar cells with traditional silicon‐based cells across 18 multiple criteria. The functional unit is defined as the production of 1 watt‐peak of electricity produced. The inventory is based on prospective organic solar cell technology and two traditional silicon technologies. The results demonstrate that from a life cycle perspective, organic solar cells can outperform conventional silicon solar cells with impacts reduced by 93%. The energy payback time for the default organic photovoltaic cell was 0.21 years (75 days) compared with multicrystalline silicon and amorphous silicon's 2.7 and 2.2 years, respectively. The minimum required lifetime of the organic cells, so that their impacts were no worse than amorphous silicon's over 25 years, was measured between 1.2 and 8.9 years. Results of the sensitivity analysis demonstrate that consideration of manufacturing routes (e.g., fullerene or solar cell production) can be targeted using life cycle assessment for further improvements in the environmental, human health, and ecotoxicity profile of organic solar cells. Copyright © 2015 John Wiley & Sons, Ltd.     

Environmental life cycle assessment of roof‐integrated flexible amorphous silicon/nanocrystalline silicon solar cell laminate

This paper presents an environmental life cycle assessment of a roof‐integrated flexible solar cell laminate with tandem solar cells composed of amorphous silicon/nanocrystalline silicon (a‐Si/nc‐Si). The a‐Si/nc‐Si cells are considered to have 10% conversion efficiency. Their expected service life is 20 years. The production scale considered is 100 MW_p per year. A comparison of the a‐Si/nc‐Si photovoltaic (PV) system with the roof‐mounted multicrystalline silicon (multi‐Si) PV system is also presented. For both PV systems, application in the Netherlands with an annual insolation of 1000 kWh/m² is considered. We found that the overall damage scores of the a‐Si/nc‐Si PV system and the multi‐Si PV system are 0.012 and 0.010 Ecopoints/kWh, respectively. For both PV systems, the impacts due to climate change, human toxicity, particulate matter formation, and fossil resources depletion together contribute to 96% of the overall damage scores. Each of both PV systems has a cumulative primary energy demand of 1.4 MJ/kWh. The cumulative primary energy demand of the a‐Si/nc‐Si PV system has an uncertainty of up to 41%. For the a‐Si/nc‐Si PV system, an energy payback time of 2.3 years is derived. The construction for roof integration, the silicon deposition, and etching are found to be the largest contributors to the primary energy demand of the a‐Si/nc‐Si PV system, whereas encapsulation and the construction for roof integration are the largest contributors to its impact on climate change. Copyright © 2012 John Wiley & Sons, Ltd.     

城域网全生命周期自动化运维应用

针对城域网运维自动化水平较低、人工成本高且无法摆脱重复运维劳动的现状,本文探讨了当前城域网自动化运维实现的关键点、难点,并针对目前城域网工作的重点、痛点,结合运维的实际情况以及一些新技术、新方向,提出了完整的、可实现的自动化运维应用体系和应用思路,同时针对典型的应用案例给出了相应的解决方案,从而彻底改变传统运维低质、低效的困难局面,推进城域网全生命周期自动化运维能力的提升。     

Energy payback and life‐cycle CO2 emissions of the BOS in an optimized 3·5 MW PV installation

This study is a life‐cycle analysis of the balance of system (BOS) components of the 3·5 MW_p multi‐crystalline PV installation at Tucson Electric Power's (TEP) Springerville, AZ field PV plant. TEP instituted an innovative PV installation program guided by design optimization and cost minimization. The advanced design of the PV structure incorporated the weight of the PV modules as an element of support design, thereby eliminating the need for concrete foundations. The estimate of the life‐cycle energy requirements embodied in the BOS is 542 MJ/m², a 71% reduction from those of an older central plant; the corresponding life‐cycle greenhouse gas emissions are 29 kg CO₂ eq./m². From field measurements, the energy payback time (EPT) of the BOS is 0·21 years for the actual location of this plant, and 0·37 years for average US insolation/temperature conditions. This is a great improvement from the EPT of about 1·3 years, estimated for an older central plant. The total cost of the balance of system components was $940 US per kW_p of installed PV, another milestone in improvement. These results were verified with data from different databases and further tested with sensitivity‐ and data‐uncertainty analyses. Copyright © 2005 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.     

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.     

基于寿命周期成本管理的输变电设备状态检修方法分析

文章对输变电寿命周期成本管理内涵进行分析,并基于寿命周期成本管理对输变电设备状态检修方法进行研究,最后结合实例进一步了解和掌握检修方法,旨在为输变电状态检修提供更多支持.     

Life‐cycle assessment of photovoltaic modules: Comparison of mc‐Si,InGaP and InGaP/mc‐Si solar modules

A higher conversion efficiency of photovoltaic modules does not automatically imply a lower environmental impact, when the life‐cycle of modules is taken into account. An environmental comparison is carried out between the production and use phase, except maintenance, of an indium–gallium–phosphide (InGaP) on multicrystalline silicon (mc‐Si) tandem module, a thin‐film InGaP cell module and a mc‐Si module. The evaluation of the InGaP systems was made for a very limited industrial production scale. Assuming a fourfold reuse of the GaAs substrates in the production of the thin‐film InGaP (half) modules, the environmental impacts of the tandem module and of the thin‐film InGaP module are estimated to be respectively 50 and 80% higher than the environmental impact of the mc‐Si module. The energy payback times of the tandem module, the thin‐film InGaP module and the mc‐Si module are estimated to be respectively 5.3, 6.3 and 3.5 years. There are several ways to improve the life‐cycle environmental performance of thin‐film InGaP cells, including improved materials efficiency in production and reuse of the GaAs wafer and higher energy efficiency of the metalorganic chemical vapour deposition process. Copyright © 2003 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.     

Comparative life‐cycle energy payback analysis of multi‐junction a‐SiGe and nanocrystalline/a‐Si modules

Despite the publicity of nanotechnologies in high tech industries including the photovoltaic sector, their life‐cycle energy use and related environmental impacts are understood only to a limited degree as their production is mostly immature. We investigated the life‐cycle energy implications of amorphous silicon (a‐Si) PV designs using a nanocrystalline silicon (nc‐Si) bottom layer in the context of a comparative, prospective life‐cycle analysis framework. Three R&D options using nc‐Si bottom layer were evaluated and compared to the current triple‐junction a‐Si design, i.e., a‐Si/a‐SiGe/a‐SiGe. The life‐cycle energy demand to deposit nc‐Si was estimated from parametric analyses of film thickness, deposition rate, precursor gas usage, and power for generating gas plasma. We found that extended deposition time and increased gas usages associated to the relatively high thickness of nc‐Si lead to a larger primary energy demand for the nc‐Si bottom layer designs, than the current triple‐junction a‐Si. Assuming an 8% conversion efficiency, the energy payback time of those R&D designs will be 0.7–0.9 years, close to that of currently commercial triple‐junction a‐Si design, 0.8 years. Future scenario analyses show that if nc‐Si film is deposited at a higher rate (i.e., 2–3 nm/s), and at the same time the conversion efficiency reaches 10%, the energy‐payback time could drop by 30%. Copyright © 2010 John Wiley & Sons, Ltd.