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Photovoltaic solar energy
Abstract
This chapter evaluates the synthesis of polysilicon and the development of photovoltaic panels for the production of electricity from solar energy. The process from quartz to solar grade silicon is analyzed unit by units presenting the mechanism and its kinetics as well as the units themselves. Next, the solar cells are analyzed and their efficiency in capturing solar energy as electrical circuits evaluating the production of electricity from them in a third section of the chapter.
... A solar panel is a flat plate, composed of materials such as: silicon, cadmium telluride, CIGS (indium, gallium and selenium or sulfur), semiconductor polymers and others [23], which in principle absorbs energy from photons and transforms solar energy by means of the photovoltaic effect into electrical energy [24], [25]; this conversion is carried out through solar cells where a constant electromagnetic field is created [26]. ...
Introduction: This paper is the product of the investigation “Identification of relevant variables in the development of photovoltaic solar projects in Colombia” developed at the Universidad Distrital Francisco José de Caldas (UDFJC) between 2020 and 2021. Due to the increase in the number of photovoltaic energy projects in Colombia, it is necessary to quantify the level of relevance related with the factors involved in order to optimize the planning and execution processes. Methods: In this research, the Delphi methodology is applied to evaluate a set of variables selected from literature, putting them to an evaluation by a group of experts with the purpose of quantifying the relationship, under a subjective judgment, between those variables and parameters immersed in low power photovoltaic solar projects in Colombia. Together with the Delphi method, the Torgerson Model was used to quantify what experts said, in order to determine which variables are the most relevant ones to the experts. Subsequently, the validation of these answers is carried out with the application of a second evaluative stage throughout the application of structured instruments. Resultados: Luego de obtener el consenso general, se analizan los resultados con el ideal de identificar las variables que obtuvieron un mayor nivel de relevancia, en las cuales se identificaron seis variables relevantes. Conclusiones: Este trabajo muestra cómo los resultados de los procesos de investigación obtienen las variables más relevantes, siendo 6 variables en total, y se analiza su impacto. Originalidad: Aplicando el método Delphi, es posible encontrar las variables más relevantes en el desarrollo de proyectos solares fotovoltaicos de baja potencia en Colombia, haciendo de este trabajo un elemento importante en el avance de las energías renovables. Limitación: No se logró una muestra masiva de resultados por la dificultad de contactar a los profesionales adecuados en el área analizada.
... Remanufacturing and redesigning are business-as-usual in the space sector as the materials and component values are extremely high [38]. Ramírez-Márquez and Martín [39] propose reducing, reusing, and recycling the photovoltaic panels used to supply electricity to satellites and space stations. The reuse concept in space manufacturing is applicable, such as in the Space X reusable rockets [14]. ...
With the world driving toward net-zero carbon emission, the space sector plays a vital role in addressing climate change and sustainability issues. For instance, satellite earth observation helps monitor natural resources and provides key data for forecasting air quality and carbon emissions; satellite navigation and communications help optimise and improve traffic management, contributing to an effective supply chain and reducing carbon emission. Besides employing space technologies as an enabler in other sectors for achieving sustainability, it is also essential to examine the sustainability agenda within the space sector itself. The European Space Agency (ESA) established the Clean Space initiative in 2012, which delivers a sustainable approach to managing space activities, aiming to minimise the environmental impact on Earth and in space. Following the triple bottom line concept, it is also vital to explore social and economic sustainability apart from the environmental aspect. Circular Economy (CE) is a concept contributing to sustainability. Stemming from sustainable manufacturing, CE was developed and pioneered by Ellen MacArthur Foundation in the UK. CE aims to eliminate waste and pollution by circulating products and materials at their highest value, which drives the efficient use of finite resources. As opposed to the "take, make, use and dispose" linear economy model, CE champions the idea of 6Rs (Reduce, Reuse, Recycle, Recover, Remanufacture and Redesign). As a result, CE profoundly impacts the value chain in an organisation's business model. The value chain in the space sector consists of the upstream and downstream segments involving various actors (stakeholders). The upstream segment covers space manufacturing activities such as launching spacecraft and satellites, which include research and development and manufacturing actors. The downstream segment comprises space applications such as activities using space data for offering products or services. Industry 4.0 is seen as an enabler of achieving sustainability. In the space sector, it is intertwined with the Space 4.0 concept. Industry 4.0, also known as the Industrial Internet of Things, refers to the cyber-physical systems where physical and virtual worlds are merged and enabled by the advancement of sensor, network and data analytics technologies. According to ESA, Space 4.0 revolutionises space activities by including more space actors from governmental to private sectors and encourages collaboration through information exchange. Existing research in other sectors has identified nine specific technologies in Industry 4.0: big data analytics, autonomous robots, simulation, horizontal and vertical system integration, internet of things, cybersecurity, cloud computing, additive manufacturing and augmented reality. Although these technological advancements have the potential to transform the value chain and contribute to developing sustainable business models, this research is still in its infancy in the space sector and no cohesive view on how Industry 4.0 could serve as an enabler in a circular life cycle for sustainability purposes in the space sector. Hence, this initial study aims to explore how Space 4.0 transforms space activities through CE for sustainability purposes. This research adopts a preliminary literature review method. The studies or reports related to this research context were collected and analysed and a number of main themes were identified based on heuristics. Finally, the thematic ontology was applied to describe the relationship between themes, contributing to a conceptual map that sets the foundation for the next phase of this research. The next phase of this research will involve a systematic literature review to expand this conceptual map. Moreover, expert interviews will be conducted to evaluate the feasibility of the themes in assessing the level of Industry 4.0 adoption in enabling this circular approach when managing space activities. The results will lead to developing a sustainability framework. Case studies will be employed to evaluate the applicability of this framework, where space actors involved in both the upstream and downstream segments will be selected. The results will inform the best practices in implementing a circular life cycle approach in managing space activities, which creates new or optimises capabilities for all space actors involved in the value chain for achieving sustainability goals.
... For the selection of a solar PV panel of a solar dryer, the primarily concerned parameter is its cost-effectiveness [125]. Since the dominant material within the PV industry is silicon [126], Si-based solar PV panels are now manufactured at a very low cost, while CIGS and CdTe ones are remaining at a more expensive level [127]. ...
Drying is important in many processes for material preservation, operation optimisation, and easy handling. Various dryers have been developed to ensure controllable drying performance and enhance efficiency. Since traditional mechanical dryers depend heavily upon fossil fuels, ongoing studies have been conducted on solar dryers, focusing on offering alternative sustainable drying methods and utilising local materials in a more sustainable manner. This review features recent work and development on solar dryers from the material and technical perspectives, emphasising the component conceptions and ameliorations, material utilisations, and drying fluid thermodynamics. The overall drying performances, advantages, and current drawbacks of different solar dryer designs are critically discussed. Applications of various solar dryers in different sectors are also described.
The trend towards shift in electric powered systems is increasing the demand for greener sources of energy supply such as renewable energy. In comparison to wind, tidal and hydropower sources of renewable energy, solar derived energy provides an extra advantage for countries located in the tropical regions where solar resource is in abundance. The purpose of this study is to devise a low-cost and portable solar tracker to maximize the capture of solar energy per square meter of photovoltaic cells by considering an innovative ball-joint device for the tracking mechanism. The design specifications of the solar tracker was determined following thorough analysis of existing components on the market, namely the tracking device and solar panel. The methodology section involved key stages of setting up of the solar tracking device, namely the design, sizing, manufacturing, and assembly phase. From results of system-testing, the ball-joint operated solar tracker proved to be effective to precisely orient the solar panels in accordance with the earth’s rotation. The energy consumed by the solar tracking device as a percentage of energy produced was approximately 0.15%, hence demonstrating a system of high efficiency. In terms of performance, panels from the solar tracker outperformed those in the static ones as they generated significantly higher current by up to 37%. The proposed device is projected to have a larger impact in terms of cost saving in scaled-up system. The low-cost, solar-tracking device with innovative tracking mechanism, have shown the potential to maximize the capture of solar power in tropical countries by using small-to medium size solar panels.
The use of coal for electricity generation is the main emitter of Greenhous Gas Emissions worldwide. According to the International Energy Agency, these emissions have to be reduced by more than 70% by 2040 to stay on track for the 1.5-2 • C scenario suggested by the Paris Agreement. To ensure a socially fair transition towards the phase-out of coal, the European Commission introduced the Coal Regions in Transition initiative in late 2017. The present paper analyses to what extent the use of photovoltaic electricity generation systems can help with this transition in the coal regions of the European Union (EU). A spatially explicit methodology was developed to assess the solar photovoltaic (PV) potential in selected regions where open-cast coal mines are planned to cease operation in the near future. Different types of solar PV systems were considered including ground-mounted systems developed either on mining land or its surroundings. Furthermore, the installation of rooftop solar PV systems on the existing building stock was also analysed. The obtained results show that the available area in those regions is abundant and that solar PV systems could fully substitute the current electricity generation of coal-fired power plants in the analysed regions.
In recent years, photovoltaic cell technology has grown extraordinarily as a sustainable source of energy, as a consequence of the increasing concern over the impact of fossil fuel-based energy on global warming and climate change. The different photovoltaic cells developed up to date can be classified into four main categories called generations (GEN), and the current market is mainly covered by the first two GEN. The 1GEN (mono or polycrystalline silicon cells and gallium arsenide) comprises well-known medium/low cost technologies that lead to moderate yields. The 2GEN (thin-film technologies) includes devices that have lower efficiency albeit are cheaper to manufacture. The 3GEN presents the use of novel materials, as well as a great variability of designs, and comprises expensive but very efficient cells. The 4GEN, also known as “inorganics-in-organics”, combines the low cost/flexibility of polymer thin films with the stability of novel inorganic nanostructures (i.e., metal nanoparticles and metal oxides) with organic-based nanomaterials (i.e., carbon nanotubes, graphene and its derivatives), and are currently under investigation. The main goal of this review is to show the current state of art on photovoltaic cell technology in terms of the materials used for the manufacture, efficiency and production costs. A comprehensive comparative analysis of the four generations is performed, including the device architectures, their advantages and limitations. Special emphasis is placed on the 4GEN, where the diverse roles of the organic and nano-components are discussed. Finally, conclusions and future perspectives are summarized.
Photovoltaic (PV) conversion of solar energy starts to give an appreciable contribution to power generation in many countries, with more than 90% of the global PV market relying on solar cells based on crystalline silicon (c-Si). The current efficiency record of c-Si solar cells is 26.7%, against an intrinsic limit of ~29%. Current research and production trends aim at increasing the efficiency, and reducing the cost, of industrial modules. In this paper, we review the main concepts and theoretical approaches that allow calculating the efficiency limits of c-Si solar cells as a function of silicon thickness. For a given material quality, the optimal thickness is determined by a trade-off between the competing needs of high optical absorption (requiring a thicker absorbing layer) and of efficient carrier collection (best achieved by a thin silicon layer). The efficiency limits can be calculated by solving the transport equations in the assumption of optimal (Lambertian) light trapping, which can be achieved by inserting proper photonic structures in the solar cell architecture. The effects of extrinsic (bulk and surface) recombinations on the conversion efficiency are discussed. We also show how the main conclusions and trends can be described using relatively simple analytic models. Prospects for overcoming the 29% limit by means of silicon/perovskite tandems are briefly discussed.
In renewable power generation, solar photovoltaic as clean and green energy technology plays a vital role to fulfill the power shortage of any country. Modeling, simulation and analysis of solar photovoltaic (PV) generator is a vital phase prior to mount PV system at any location, which helps to understand the behavior and characteristics in real climatic conditions of that location. In this context, a single diode equivalent circuit model with the stepwise detailed simulation of a solar PV module under Matlab/Simulink ambience is presented. I–V and P–V graph of solar PV module provide a broad understanding to researchers, manufacturers and social communities. The simulated result of the PV module is verified by the manufacturer data-sheet of JAP6-72-320/4BB module and maximum relative error percentage is found 1.65% which shows a good agreement between manufacturer values and simulated values. Moreover, the performance of PV module for real metrological data (irradiance and temperature) shows good results. In addition to this, it is presumed as a sturdy tool to evaluate the performance of any solar PV modules.
One neglected socio-cultural and political dimension to the rapid diffusion of solar power in Sub-Saharan Africa is the question of what happens when things fall apart. Investors in the small-scale renewable energy sector are increasingly concerned with the status of broken or non-functioning products and there is an emerging consensus around the need for centralised recycling systems as the solution to future flows of ‘solar waste’.
But what does the afterlife of off-grid solar products look like from below? Grounded in anthropology, geography and economic sociology, this paper tracks the impact of off grid solar products through contexts of breakdown, repair, and disposal. Combining stakeholder interviews, a longitudinal survey of product failure rates in Kenya and ethnographic research at a repair workshop in the town of Bomet, we challenge narratives of energy transitions that fail to address the environmental consequences of mass consumption and present an alternative approach to solar waste embedded in cultures and economies of repair.
The development in solar PV technology is growing very fast in recent years due to technological improvement, cost reductions in materials and government support for renewable energy based electricity production. Photovoltaic is playing an important role to utilize solar energy for electricity production worldwide. At present, the PV market is growing rapidly with worldwide around 23.5 GW in 2010 and also growing at an annual rate of 35-40%, which makes photovoltaic as one of the fastest growing industries. The efficiency of solar cell is one of the important parameter in order to establish this technology in the market. Presently, extensive research work is going for efficiency improvement of solar cells for commercial use. The efficiency of monocrystalline silicon solar cell has showed very good improvement year by year. It starts with only 15% in 1950s and then increase to 17% in 19705 and continuously increase up to 28% nowadays. The growth in solar photovoltaic technologies including worldwide status, materials for solar cells, efficiency, factor affecting the performance of PV module, overview on cost analysis of PV and its environmental impact are reviewed in this paper.
Photovoltaic energy has grown at an average annual rate of 60% in the last 5 years and has surpassed 1/3 of the cumulative wind energy installed capacity, and is quickly becoming an important part of the energy mix in some regions and power systems. This has been driven by a reduction of cost of PV modules. This growth has also triggered the evolution of classic PV power converters from conventional single-phase grid-tied inverters to more complex topologies in order to increase efficiency, power extraction from the sun, reliability, while not impacting the cost. This paper presents an overview of the existing PV energy conversion systems, addressing the system configuration of different PV plants, and the PV converter topologies that have found practical applications for grid-connected systems. In addition, recent research and emerging PV converter technology are discussed, highlighting their possible advantages compared with existing technology.
We present a model for predicting the solar cell efficiency potential of multicrystalline silicon bricks prior to sawing. Three model inputs are required: bulk lifetime images from the side faces of the bricks, the cell manufacturing process, and its gettering action. The model is set up with numerical device and circuit simulations, but may afterwards be parameterized for inline application. In the example shown here, we chose literature data to quantify the increase in bulk lifetime caused by phosphorus gettering of impurities during cell manufacturing. Our proposed model enables manufacturers to (i) assess initial brick quality in relation to their specific cell production line, (ii) to exclude certain parts of the bricks from cell manufacturing, and (iii) to adjust cell manufacturing to initial material quality. The specific gettering efficiency and cell process can be fed into the model dynamically and need to be calibrated ideally for each material manufacturer and each cell production line. The model presented here can be extended to cast mono and dendritically grown bricks.
Measurements of recombination parameters of both photoconductive materials and structures (solar cells) have been de-scribed. For materials, the methods are based on both steady-state photoconductivity (or quasi steady-state photoconductivity) and photocurrent decay PCD experiments. Examples of PCD measurements taken from literature for c-Si wafers and our own experiments for amorphous a-Si:H and a-SiC:H samples have been discussed. Investigation of solar cells based on the most popular photovoltage decay technique is widely described. Measurement and interpretation details have been discussed. Theoretical description and experimental evidence is, however, focused on combined photovoltage and photocurrent decays technique, developed in the authors' laboratory. This technique enables us determination of both minor-ity carrier lifetime and surface recombination velocity of photocarriers. The measurement setup enabling determination of both open circuit voltage and short circuit current decay times has been described.
Global energydemandandenvironmentalconcernsarethedrivingforceforuseofalternative,
sustainable, andcleanenergysources.SolarenergyistheinexhaustibleandCO2-emission-free energy
source worldwide.TheSunprovides1.4�105 TWpowerasreceivedonthesurfaceoftheEarthand
about 3.6�104 TWofthispowerisusable.In2012,worldpowerconsumptionwas17TW,whichisless
than 3.6�104 TW.Photovoltaic(PV)cellsarethebasicelementforconvertingsolarenergyinto
electricity.PVcelltechnologies,energyconversionefficiency,economicanalysis,energypolicies,
environmentalimpact,variousapplications,prospects,andprogresshavebeencomprehensively
reviewedandpresentedinthispaper.Thisworkcompilesthelatestliterature(i.e.journalarticles,
conference proceedings,andreports,amongothers)onPVpowergeneration,economicanalysis,
environmentalimpact,andpoliciestoincreasepublicawareness.Fromthereview,itwasfoundthat
PV isaneasywaytocapturesolarenergywherePVbasedpowergenerationhasalsorapidlyincreased.
We have investigated the electronic and optical properties of silicene nanomeshes (SNMs) using first-principle calculations. The emerging information indicates that the resulting properties are sensitive to the width (W) of the silicon chains between neighboring holes. Our results show that the bandgaps of SNMs with an odd W value remain closed. On the contrary, bandgaps are opened in SNMs with an even W value at the Γ points. Most importantly, SNMs possess a broad frequency photoresponse ranging from far infrared (0 eV) to ultraviolet (10 eV) and the optical properties of SNMs can be tuned by varying the value of W. Our results reveal that SNMs, as silicon-based materials, have a significant potential for electronic, photonic, and photovoltaic applications.
Silicon has been the dominant material in the photovoltaic (PV) industry since its application in the space industry in 1958. This review focuses on crystalline silicon solar cells, primarily due to their dominance in the photovoltaic industry, omitting other photovoltaic cell technologies such as second generation (e.g. thin films) and third generation (e.g. nano-structured solar cells). The value chain for the production of crystalline silicon solar cells has been reviewed. The primary processing steps for the production of silicon solar cells from quartz are as follows: bulk production of metallurgical-grade silicon via carbothermic reduction in a submerged furnace, refining of metallurgical-grade silicon via the chemical means to polycrystalline silicon, or through the metallurgical route to solar-grade silicon, wafer manufacturing, and, lastly, silicon solar cell manufacturing. During downstream processing, solar cells are interconnected and encapsulated into solar modules (panels), which can be used individually or incorporated into a photovoltaic system for electricity generation and supply. The cost for crystalline silicon based solar cells is approaching one US dollar per watt peak ($1/Wp), while the most cost-effective solar modules in industry have reported costs below $1/Wp, and are based on CdTe thin films. Solar cell energy conversion efficiencies as high as 22% have been reported in industry for crystalline silicon solar cells.
Solar cell performance decreases with increasing temperature, fundamentally owing to increased internal carrier recombination rates, caused by increased carrier concentrations. The operating temperature plays a key role in the photovoltaic conversion process. Both the electrical efficiency and the power output of a photovoltaic (PV) module depend linearly on the operating temperature. The various correlations proposed in the literature represent simplified working equations which can be apply to PV modules or PV arrays mounted on free-standing frames, PV-Thermal collectors, and building integrated photovoltaic arrays, respectively. The electrical performance is primarily influenced by the material of PV used. Numerous correlations for cell temperature which have appeared in the literature involve basic environmental variables and numerical parameters which are material or system dependent. In this paper, a brief discussion is presented regarding the operating temperature of one-sun commercial grade silicon- based solar cells/modules and its effect upon the electrical performance of photovoltaic installations. Generally, the performance ratio decreases with latitude because of temperature. However, regions with high altitude have higher performance ratios due to low temperature, like, southern Andes, Himalaya region, and Antarctica. PV modules with less sensitivity to temperature are preferable for the high temperature regions and more responsive to temperature will be more effective in the low temperature regions. The geographical distribution of photovoltaic energy potential considering the effect of irradiation and ambient temperature on PV system performance is considered.
The traditional polysilicon processes should be refined when addressing the low energy consumption requirement for the production
of solar grade silicon. This paper addresses the fluid dynamic conditions required to deposit polysilicon in the traditional
Siemens reactor. Analytical solutions for the deposition process are presented, providing information on maximizing the rate
between the amount of polysilicon obtained and the energy consumed during the deposition process. The growth rate, deposition
efficiency, and power-loss dependence on the gas velocity, the mixture of gas composition, the reactor pressure, and the surface
temperature have been analyzed. The analytical solutions have been compared to experimental data and computational solutions
presented in the literature. At atmospheric pressure, the molar fraction of hydrogen at the inlet should be adjusted to the
range of 0.85–0.90, the gas inlet temperature should be raised within the interval of 673 and
, and the gas velocity should reach the Reynolds number 800. The resultant growth rate will be between 6 and
. Operation above atmospheric pressure is strongly recommended to achieve growth rates of
at
.
A hybrid polycrystalline silicon production route is optimized following a two-step procedure. First, surrogate models for the main units are developed following different techniques which depend on the available information. Secondly, the optimization of the entire process flowsheet allows determining the optimal tradeoff between yield and energy consumption. A base production capacity of 2000 t/y of polycrystalline silicon is considered, with an equipment cost of 9.97 M$. Three scenarios are evaluated: maximum silicon production, minimum operating costs and maximum total profit. The maximization of the total profit is the most promising scenario, obtaining a selling price of 8.93 $/kgPoly, below the commercial price, 10 $/kgPoly. The revenue obtained is 10 M$/y, with an operating cost of 6.48 M$/y. Furthermore, a plant scale-up study was performed. If the production capacity is increased by a factor of 10, it results in a reduction of 1.03 $/kgSiPoly.
The increasing urban population and incorrect patterns of urban activities along with inappropriate development of cities have incurred significant damage to the environment and have faced man with numerous problems such as fossil fuels deficiency. The environmental problems owing to fossil fuels and increasing demand for energy have made the approach to renewable energies and the development and utilization of these sources more and more necessary. The development and promotion of renewable energies aid the realization of countries’ developmental goals in economic, social, and environmental aspect which is one of the basic factors in achieving sustainable development in any country. Biomass is one of the sources that no acceptable assessment of its technical-economic production feasibility has been done yet in various regions of Iran. Biomass is of considerable importance among renewable energy resources and its usage in energy generation prevents pollution caused by its discharge into the environment along with generating clean energy similar to that obtained from other renewable sources. Since biomass is not well known as a source of energy generation in Iran and because there are no clear regulations concerning its use for this purpose, this paper used the HOMER software to study four scenarios of utilizing wind, solar, and biomass energies for the simultaneous generation of electricity and heat in ZarrinShahr located in Isfahan Province. Results showed that receiving electricity from the national grid is superior to the use of biomass if the under study place is less than 2.58 km away from access points to this grid. Otherwise, based on economic optimization performed by HOMER software, it is recommended that a hybrid system of renewable energy including a solar panel, a biomass-fuelled generator, two batteries and a converter at a cost of 1.019 $/kWh be used, in which 1955 kWh is generated by the solar panel and 92 kWh by the biomass-fuelled generator. According to the study of previous researches, no reviews have been made thus far on the use of dump load for the provision of electricity and heat in hybrid renewable energy systems.
With topics ranging from epitaxy through lattice defects and doping to quantum computation, this book provides a personalized survey of the development and use of silicon, the basis for the revolutionary changes in our lives sometimes called "The Silicon Age." Beginning with the very first developments more than 50 years ago, it reports on all aspects of silicon and silicon technology up to its use in exciting new technologies, including a glance at possible future developments. A team of expert authors, many of them pioneers in the field, have written informative and stimulating contributions that will be of interest to all scientists working with silicon.
Solar cell manufacturing is based on solar grade silicon which can be obtained using silane as precursor. Silane is produced by redistribution reactions of trichlorosilane. The aim of the present work is to study the control properties of a multitasking reactive distillation column to produce silane, dichlorosilane and monochlorosilane. Control adjustment was defined in such way that the column may work in multitasking mode producing the three interest components in high purity. Several control strategies were studied to define the best dynamic performance which allow to produce those three components within the same column. In order to observe the dynamic behavior of the multitasking reactive distillation column, this system was tested under various control strategies: temperature, composition and cascade (temperature/composition), having as target to keep silanes purity in 99.5%mol. The results indicated that is possible to obtain a conceptual design of a single reactive distillation column which would be able to produce all products. The proposed multitasking column avoids all hurdles involved in the traditional way to produce and purify all those three components. It was observed those evaluated control structures can stabilize the system against tested disturbances, even the simplest temperature control structure.
Solar photovoltaic (PV) electricity has the potential to be a major energy solution, sustainably suitable for urban areas of the future. However, although PV technology has been projected as one of the most promising candidates to replace conventional fossil based power plants, the potential disadvantages of the PV panels end-of-life (EoL) have not been thoroughly evaluated. The current challenge concerning PV technology resides in making it more efficient and competitive in comparison with traditional fossil powered plants, without neglecting the appraisal of EoL impacts. Indeed, considering the fast growth of the photovoltaic market, started 30 years ago, the amount of PV waste to be handled and disposed of is expected to grow drastically. Therefore, there is a real need to develop effective and sustainable processes to address the needed recycle of the growing number of decommissioned PV panels. Many laboratory-scale or pilot industrial processes have been developed globally during the years by private companies and public research institutes to demonstrate the real potential offered by the recycling of PV panels. One of the tested up lab-scale recycling processes – for the crystalline silicon technology – is the thermal treatment, aiming at separating PV cells from the glass, through the removal of the EVA (Ethylene Vinyl Acetate) layer. Of course, this treatment may entail that some hazardous components, such as Cd, Pb, and Cr, are released to the environment, therefore calling for very accurate handling. To this aim, the sustainability of a recovery process for EoL crystalline silicon PV panels was investigated by means of Life Cycle Assessment (LCA) indicators. The overall goal of this paper was to compare two different EoL scenarios, by evaluating the environmental advantages of replacing virgin materials with recovered materials with a special focus on the steps and/or components that can be further improved.
Polysilicon production costs contribute approximately to 25–33% of the overall cost of the solar panels
and a similar fraction of the total energy invested in their fabrication. Understanding the energy losses
and the behaviour of process temperature is an essential requirement as one moves forward to design
and build large scale polysilicon manufacturing plants. In this paper we present thermal models for two
processes for poly production, viz., the Siemens process using trichlorosilane (TCS) as precursor and the
fluid bed process using silane (monosilane, MS). We validate the models with some experimental
measurements on prototype laboratory reactors relating the temperature profiles to product quality. A
model sensitivity analysis is also performed, and the effects of some key parameters such as reactor wall
emissivity and gas distributor temperature, on temperature distribution and product quality are exam-
ined. The information presented in this paper is useful for further understanding of the strengths and
weaknesses of both deposition technologies, and will help in optimal temperature profiling of these
systems aiming at lowering production costs without compromising the solar cell quality.
Heteroepitaxy-atomically aligned growth of a crystalline film atop a different crystalline substrate-is the basis of electrically driven lasers, multijunction solar cells, and blue-light-emitting diodes. Crystalline coherence is preserved even when atomic identity is modulated, a fact that is the critical enabler of quantum wells, wires, and dots. The interfacial quality achieved as a result of heteroepitaxial growth allows new combinations of materials with complementary properties, which enables the design and realization of functionalities that are not available in the single-phase constituents. Here we show that organohalide perovskites and preformed colloidal quantum dots, combined in the solution phase, produce epitaxially aligned 'dots-in-a-matrix' crystals. Using transmission electron microscopy and electron diffraction, we reveal heterocrystals as large as about 60 nanometres and containing at least 20 mutually aligned dots that inherit the crystalline orientation of the perovskite matrix. The heterocrystals exhibit remarkable optoelectronic properties that are traceable to their atom-scale crystalline coherence: photoelectrons and holes generated in the larger-bandgap perovskites are transferred with 80% efficiency to become excitons in the quantum dot nanocrystals, which exploit the excellent photocarrier diffusion of perovskites to produce bright-light emission from infrared-bandgap quantum-tuned materials. By combining the electrical transport properties of the perovskite matrix with the high radiative efficiency of the quantum dots, we engineer a new platform to advance solution-processed infrared optoelectronics.
This chapter discusses the principles, history, and importance of photovoltaics. The physical effect which underlies photovoltaics was first observed by Becquerel in 1839, when he produced a current by exposing silver electrodes to radiation in an electrolyte. The effect was described in more detail by Adams and Day in 1877. The main driving force behind the widespread use of photovoltaics for terrestrial power supplies came in 1973 with the notorious oil shock. All the available options for cost reduction were examined, as it was already recognised that the excessive costs of photovoltaic plants posed the largest obstacle for the widespread use of photovoltaics. The operation of water pumps using photovoltaics is a viable application in this area. In the more distant future environmental concerns and the finite supply of fossil fuels make it certain that the sun will also be used for large scale power supplies.
Hydrogenation of silicon tetrachloride (STC) in the presence of silicon was investigated both thermodynamically and experimentally. The thermodynamic results revealed that the reaction is thermodynamically constrained and the STC equilibrium conversion is nearly temperature-independent but increases with increasing pressure and H2/STC feed ratio. Trichlorosilane (TCS) was calculated to be the dominant product, with trace amounts of dichlorosilane (DCS) and HCl as feasible byproducts. Experimental tests were conducted in a fixed-bed reactor loaded with silicon. The results indicated that the reaction is kinetically restricted in the absence of a catalyst. Adding CuCl to the silicon mass bed was found to result in a dramatic increase in the STC conversion, and Cu3Si was determined to be the active species. In all of the tests runs, TCS was determined to be the dominant product, and the STC reaction rate was found to increase markedly as the temperature and STC partial pressure increased but not to depend on the silicon particle size.
This paper presents a reactive distillation column for the catalytic disproportionation of trichlorosilane to silane which includes three consecutive reversible reactions with a thermodynamic conversion to silane as low as 0.2% and is of no practical significance using the conventional reactors. This reaction system is however characterized by a large distinction in the boiling points of the components, which makes the reactive distillation extremely favored. Nevertheless, the normal reactive distillation column possesses the shortage of high refrigeration requirement as the standard boiling point of the overhead product silane is −112 °C. A novel reactive distillation column with intercondensers placed within has been simulated using Aspen Plus package for a feasible alternative to alleviate this drawback. The calculated results show that a reduction in the refrigeration load of more than 97% can be obtained when one intermediate condenser is inserted between the rectifying and reaction zones, and that another normal intermediate condenser equipped within the reaction section can further decrease the condensation requirement of the first intermediate condenser by 50%. Effects of the configuration parameters and operational conditions have also been investigated for optimal design and operation of the proposed reactor.
Over recent years, there has been marked recent improvements in the efficiency of energy conversion of photovoltaics, enhancing this technology's potential as a long term energy generation option. This paper describes the physics behind these improvements and outlines factors placing the upper bounds upon perfommance, suggesting paths towards increased efficiency in the future.
For an installed silicon based solar cell panel, about 40% of the energy costs involved in the production of the panels can be attributed to the production of the silicon feedstock itself (poly production and crystal growth). Hence reducing the energy consumption in these steps is crucial in order to minimize the energy payback time of installed capacity. For the first step, viz., the poly production, the most promising cost reduction alternative is the fluidized bed reactors (FBR) using silane as a precursor rather than trichlorosilane (TCS) since for TCS the reverse reactions makes the theoretical trichlorosilane conversion substantially lower. Use of silane has, however, many challenges and scaleup to larger capacity can be achieved if associated risks are properly dealt with. This paper outlines some of these challenges and provides a detailed survey of the current status on the growth mechanism and kinetics of silane pyrolysis. The paper also provides a summary of modeling of fluidized bed reactors (FBR) in some depth and give some empirical insight to key aspects in FBR scaleup design.
Solar grade silicon, as a starting material for crystallization to produce solar cells, is discussed here in terms of impurities whose maximum content is estimated from recent literature and conferences. A review of the production routes for each category of solar-grade silicon (undoped, compensated or heavily compensated) is proposed with emphasis on the metallurgical route.Some recent results are proposed concerning segregation, showing that directional solidification systems can be used for solidification even at high solidification rate (15 cm/h). Results on inductive plasma purification, where boron is evacuated as HBO in a gas phase blown from an inductive plasma torch, are shown to apply as well to arc plasmas and purification by moist gas.Special attention is paid to the history of impurities in the purification processes, showing that impure auxiliary phases (silicon tetrachloride, slag, aluminum, etc.) often need their own purification process to enable their recycling, which has to be considered to evaluate the cost (financial, energetic and environmental) of the purification route.
The work presented here pertains to the study of hydrochlorination of silicon in a fixed bed reactor to produce primarily trichlorosilane. Most of the data on this reaction system is patented. Reaction takes place between hydrogen chloride gas and dry silicon powder in a fixed bed condition. The optimum temperature for this reaction was determined by changing the reaction temperature and collecting the condensed product of this reaction, i.e. trichlorosilane, and was found to be 321°C at atmospheric pressure. Using the reaction kinetics theory, fixed bed reaction rate constants were determined for 124, 141, 160, 208 and 438 µm average silicon particle sizes at 321°C and atmospheric pressure. It was observed that the fixed bed reaction rate constant values were of the same order and around 0.7 s. The conversion of HCl increases with a decrease in particle size of silicon and lowering of the superficial velocity of HCl gas.
A detailed mathematical model for the hot-wall, multiple-disk-in-tube, low-pressure, chemical vapor deposition reactor is developed by using reaction engineering concepts. This model includes the convective and diffusive mass transport in the annular flow region formed by the reactor wall and the edges of the wafers as well as the surface reactions on the reactor wall. In addition, the model describes the coupling of diffusion between and reaction on the wafers. The model predictions show good quantitative agreement with published experimental data from different sources.
A general model has been developed for multicomponent‐multireaction systems in the hot‐wall multiple‐wafers‐in‐tube LPCVD reactor. The modeling equations describe the coupled convective and diffusive mass fluxes in the annular reactor flow region as well as those between each pair of wafers. Complex reaction mechanisms involving both gas‐phase and surface reactions can be included in the model formulation. Multicomponent transport effects in the deposition of pure and doped polycrystalline Si are analyzed. The model predicts experimentally observed growth rates for pure polycrystalline Si quite well. However, because of insufficient data, a comparison of model predictions and experimental growth rates has not been feasible for in situ doped Si. The model is also used to predict the performance of a new continuous moving boat LPCVD reactor offering excellent film uniformity and process automation.
The main applications of photoconductance measurements of silicon wafers are the determination of implicit device voltages, bulk minority carrier lifetimes, emitter recombination currents and surface recombination velocities. These applications are illustrated with selected experiments. Multicrystalline and single crystal silicon wafers are used with different surface c onditions. The practical situations considered here range from industrial process control to advanced research. Interpreting photoconductance in terms of implicit device voltage is particularly useful: the swept illumination conditions used in a quasi-steady-state photoconductance measurement permit the determination of complete I-V characteristic curves, ideality factors and saturation currents. The more classical interpretation in terms of an effective lifetime τeff allows to discriminate different recombination mechanisms. Shockley-Read-Hall bulk recombination with a large asymmetry between the fundamental electron and hole lifetimes is found to explain the strong variation of τeff at low injection level observed in some samples. Measurements in the high injection range permit the determination of the emitter saturation current density. This saturation current can impose quite restrictive limits on the measurable minority carrier lifetimes at low injection, particularly for low resistivity wafers. The surface recombination velocity of the Si/SiO 2 interface can also be a source of variability of τeff.
THE large-scale use of photovoltaic devices for electricity generation is prohibitively expensive at present: generation from existing commercial devices costs about ten times more than conventional methods1. Here we describe a photovoltaic cell, created from low-to medium-purity materials through low-cost processes, which exhibits a commercially realistic energy-conversion efficiency. The device is based on a 10-µm-thick, optically transparent film of titanium dioxide particles a few nanometres in size, coated with a monolayer of a charge-transfer dye to sensitize the film for light harvesting. Because of the high surface area of the semiconductor film and the ideal spectral characteristics of the dye, the device harvests a high proportion of the incident solar energy flux (46%) and shows exceptionally high efficiencies for the conversion of incident photons to electrical current (more than 80%). The overall light-to-electric energy conversion yield is 7.1-7.9% in simulated solar light and 12% in diffuse daylight. The large current densities (greater than 12 mA cm-2) and exceptional stability (sustaining at least five million turnovers without decomposition), as well as the low cost, make practical applications feasible.
A simulation model for the low-pressure chemical vapor deposition of polycrystalline silicon using a silane-hydrogen mixture in a multiwafer batch record has been developed. This model was employed to study the effects of temperature, flow parameters, reactor geometry, and wafer size upon the process, particularly the uniformity of silicon deposition. Potential improvements in the system performance were determined by utilizing optimum temperature staging and reactant injection schemes. The results also showed that nonuniform wafer spacing can improve deposition uniformity and wafer throughput while decreasing the process sensitivity to reactant flow rate variations.
Surface voltage and surface photovoltage measurements have become important semiconductor characterization tools, largely because of the availability of commercial equipment and the contactless nature of the measurements. The range of the basic technique has been expanded through the addition of corona charge. The combination of surface charge and illumination allows surface voltage, surface barrier height, flatband voltage, oxide thickness, oxide charge density, interface trap density, mobile charge density, oxide integrity, minority carrier diffusion length, generation lifetime, recombination lifetime and doping density to be determined. In this review I shall briefly review the history of surface voltage, then discuss the principles of the technique and give some examples and applications.
As photovoltaic penetration of the power grid increases, accurate predictions of return on investment require accurate prediction of decreased power output over time. Degradation rates must be known in order to predict power delivery. This article reviews degradation rates of flat-plate terrestrial modules and systems reported in published literature from field testing throughout the last 40 years. Nearly 2000 degradation rates, measured on individual modules or entire systems, have been assembled from the literature, showing a median value of 0.5%/year. The review consists of three parts: a brief historical outline, an analytical summary of degradation rates, and a detailed bibliography partitioned by technology.
IntroductionFundamental Properties of SemiconductorsPN -Junction Diode ElectrostaticsSolar Cell FundamentalsAdditional TopicsSummaryReferences
The history of silicon terrestrial module evolution over the last 50 years is briefly reviewed. Key technical developments that occurred over a rapid evolutionary period between 1975 and 1985 are identified. Information is included on improvements in both the energy conversion efficiency and prices of commercial modules over the 50-year timeframe. Copyright © 2005 John Wiley & Sons, Ltd.
We review the technical progress made in the past several years in the area of mono- and polycrystalline thin-film photovoltaic (PV) technologies based on Si, III–V, II–VI, and I–III–VI2 semiconductors, as well as nano-PV. PV electricity is one of the best options for sustainable future energy requirements of the world. At present, the PV market is growing rapidly at an annual rate of 35–40%, with PV production around 10.66 GW in 2009. Si and GaAs monocrystalline solar cell efficiencies are very close to the theoretically predicted maximum values. Mono- and polycrystalline wafer Si solar cells remain the predominant PV technology with module production cost around $1.50 per peak watt. Thin-film PV was developed as a means of substantially reducing the cost of solar cells. Remarkable progress has been achieved in this field in recent years. CdTe and Cu(In,Ga)Se2 thin-film solar cells demonstrated record efficiencies of 16.5% and almost 20%, respectively. These values are the highest achieved for thin-film solar cells. Production cost of CdTe thin-film modules is presently around $0.76 per peak watt.
The first fabrication and performance studies of PV devices with bulk heterojunction (BHJ) structure using an organic-solution-processable functionalized graphene (SPFGraphene) material as electron-acceptor material and P3OT and P3HT as donor materials, was presented. The results show that the graphane sheets are homogeneously dispersed together with organic materials, especially conjugated polymers, in organic solvents used for PV and other applications. It can be seen that the P3OT/SPFGrephene composite film has almost the same absorption as pure P3OT film in the wavelength range 400-650 nm. Processing highly delocalized electrons on a large 2D π-conjugated plane, graphene could also exhibit strong donor/acceptor interactions with conjugated polymers for PV device applications. When the SPFgraphene content increases to 5 wt%, the graphene sheets may be enough to produce an effective donor/acceptor interface.
This paper considers intrinsic loss processes that lead to fundamental limits in solar cell efficiency. Five intrinsic loss processes are quantified, accounting for all incident solar radiation. An analytical approach is taken to highlight physical mechanisms, obscured in previous numerical studies. It is found that the free energy available per carrier is limited by a Carnot factor resulting from the conversion of thermal energy into entropy free work, a Boltzmann factor arising from the mismatch between absorption and emission angles and also carrier thermalisation. It is shown that in a degenerate band absorber, a free energy advantage is achieved over a discrete energy level absorber due to entropy transfer during carrier cooling. The non-absorption of photons with energy below the bandgap and photon emission from the device are shown to be current limiting processes. All losses are evaluated using the same approach providing a complete mathematical and graphical description of intrinsic mechanisms leading to limiting efficiency. Intrinsic losses in concentrator cells and spectrum splitting devices are considered and it is shown that dominant intrinsic losses are theoretically avoidable with novel device designs. Copyright © 2010 John Wiley & Sons, Ltd.
Global environmental concerns and the escalating demand for energy, coupled with steady progress in renewable energy technologies, are opening up new opportunities for utilization of renewable energy resources. Solar energy is the most abundant, inexhaustible and clean of all the renewable energy resources till date. The power from sun intercepted by the earth is about 1.8 x 1011 MW, which is many times larger than the present rate of all the energy consumption. Photovoltaic technology is one of the finest ways to harness the solar power. This paper reviews the photovoltaic technology, its power generating capability, the different existing light absorbing materials used, its environmental aspect coupled with a variety of its applications. The different existing performance and reliability evaluation models, sizing and control, grid connection and distribution have also been discussed.
In order to find an upper theoretical limit for the efficiency of p‐n junction solar energy converters, a limiting efficiency, called the detailed balance limit of efficiency, has been calculated for an ideal case in which the only recombination mechanism of hole‐electron pairs is radiative as required by the principle of detailed balance. The efficiency is also calculated for the case in which radiative recombination is only a fixed fraction f c of the total recombination, the rest being nonradiative. Efficiencies at the matched loads have been calculated with band gap and f c as parameters, the sun and cell being assumed to be blackbodies with temperatures of 6000°K and 300°K, respectively. The maximum efficiency is found to be 30% for an energy gap of 1.1 ev and f c = 1. Actual junctions do not obey the predicted current‐voltage relationship, and reasons for the difference and its relevance to efficiency are discussed.
The maximum efficiencies of ideal solar cells are calculated for both single and multiple energy gap cells using a standard air mass 1.5 terrestrial solar spectrum. The calculations of efficiency are made by a simple graphical method, which clearly exhibits the contributions of the various intrinsic losses. The maximum efficiency, at a concentration of 1 sun, is 31%. At a concentration of 1000 suns with the cell at 300 K, the maximum efficiencies are 37, 50, 56, and 72% for cells with 1, 2, 3, and 36 energy gaps, respectively. The value of 72% is less than the limit of 93% imposed by thermodynamics for the conversion of direct solar radiation into work. Ideal multiple energy gap solar cells fall below the thermodynamic limit because of emission of light from the forward‐biased p‐n junctions. The light is radiated at all angles and causes an entropy increase as well as an energy loss.