Showing papers on "Solar energy published in 2018"
TL;DR: In this paper, the merits and demerits of solar energy technologies are both discussed and a number of technical problems affecting renewable energy research are also highlighted, along with beneficial interactions between regulation policy frameworks and their future prospects.
Abstract: The development of novel solar power technologies is considered to be one of many key solutions toward fulfilling a worldwide increasing demand for energy. Rapid growth within the field of solar technologies is nonetheless facing various technical barriers, such as low solar cell efficiencies, low performing balance-of-systems (BOS), economic hindrances (e.g., high upfront costs and a lack of financing mechanisms), and institutional obstacles (e.g., inadequate infrastructure and a shortage of skilled manpower). The merits and demerits of solar energy technologies are both discussed in this article. A number of technical problems affecting renewable energy research are also highlighted, along with beneficial interactions between regulation policy frameworks and their future prospects. In order to help open novel routes with regard to solar energy research and practices, a future roadmap for the field of solar research is discussed.
1,331 citations
TL;DR: A hierarchically nanostructured gel (HNG) based on polyvinyl alcohol (PVA) and polypyrrole (PPy) that serves as an independent solar vapour generator that enables highly efficient solar vapours generation.
Abstract: Solar vapour generation is an efficient way of harvesting solar energy for the purification of polluted or saline water. However, water evaporation suffers from either inefficient utilization of solar energy or relies on complex and expensive light-concentration accessories. Here, we demonstrate a hierarchically nanostructured gel (HNG) based on polyvinyl alcohol (PVA) and polypyrrole (PPy) that serves as an independent solar vapour generator. The converted energy can be utilized in situ to power the vaporization of water contained in the molecular meshes of the PVA network, where water evaporation is facilitated by the skeleton of the hydrogel. A floating HNG sample evaporated water with a record high rate of 3.2 kg m−2 h−1 via 94% solar energy from 1 sun irradiation, and 18–23 litres of water per square metre of HNG was delivered daily when purifying brine water. These values were achievable due to the reduced latent heat of water evaporation in the molecular mesh under natural sunlight. Effective energy confinement via tailored water transport in hierarchical nanostructured gels enables highly efficient solar vapour generation.
1,174 citations
TL;DR: Tao et al. as discussed by the authors discuss the development of the key components for achieving high-performance evaporation, including solar absorbers and structures, thermal insulators and thermal concentrators.
Abstract: As a ubiquitous solar-thermal energy conversion process, solar-driven evaporation has attracted tremendous research attention owing to its high conversion efficiency of solar energy and transformative industrial potential. In recent years, solar-driven interfacial evaporation by localization of solar-thermal energy conversion to the air/liquid interface has been proposed as a promising alternative to conventional bulk heating-based evaporation, potentially reducing thermal losses and improving energy conversion efficiency. In this Review, we discuss the development of the key components for achieving high-performance evaporation, including solar absorbers, evaporation structures, thermal insulators and thermal concentrators, and discuss how they improve the performance of the solar-driven interfacial evaporation system. We describe the possibilities for applying this efficient solar-driven interfacial evaporation process for energy conversion applications. The exciting opportunities and challenges in both fundamental research and practical implementation of the solar-driven interfacial evaporation process are also discussed. The thermal properties of solar energy can be exploited for many applications, including evaporation. Tao et al. review recent developments in the field of solar-driven interfacial evaporation, which have enabled higher-performance structures by localizing energy conversion to the air/liquid interface.
1,139 citations
TL;DR: This review sums up recent theoretical and experimental approaches for understanding the underlying photophysical processes in hot electron generation and discusses various electron-transfer models on both plasmonic metal nanostructures and plasMonic metal/semiconductor heterostructure.
Abstract: Visible-light-driven photochemistry has continued to attract heightened interest due to its capacity to efficiently harvest solar energy and its potential to solve the global energy crisis. Plasmonic nanostructures boast broadly tunable optical properties coupled with catalytically active surfaces that offer a unique opportunity for solar photochemistry. Resonant optical excitation of surface plasmons produces energetic hot electrons that can be collected to facilitate chemical reactions. This review sums up recent theoretical and experimental approaches for understanding the underlying photophysical processes in hot electron generation and discusses various electron-transfer models on both plasmonic metal nanostructures and plasmonic metal/semiconductor heterostructures. Following that are highlights of recent examples of plasmon-driven hot electron photochemical reactions within the context of both cases. The review concludes with a discussion about the remaining challenges in the field and future oppor...
891 citations
TL;DR: Wang et al. as discussed by the authors designed a novel type of plasmonic material, which is made by uniformly decorating fine metal nanoparticles into the 3D mesoporous matrix of natural wood.
Abstract: Plasmonic metal nanoparticles are a category of plasmonic materials that can efficiently convert light into heat under illumination, which can be applied in the field of solar steam generation. Here, this study designs a novel type of plasmonic material, which is made by uniformly decorating fine metal nanoparticles into the 3D mesoporous matrix of natural wood (plasmonic wood). The plasmonic wood exhibits high light absorption ability (≈99%) over a broad wavelength range from 200 to 2500 nm due to the plasmonic effect of metal nanoparticles and the waveguide effect of microchannels in the wood matrix. The 3D mesoporous wood with numerous low-tortuosity microchannels and nanochannels can transport water up from the bottom of the device effectively due to the capillary effect. As a result, the 3D aligned porous architecture can achieve a high solar conversion efficiency of 85% under ten-sun illumination (10 kW m−2). The plasmonic wood also exhibits superior stability for solar steam generation, without any degradation after being evaluated for 144 h. Its high conversion efficiency and excellent cycling stability demonstrate the potential of newly developed plasmonic wood to solar energy-based water desalination.
623 citations
TL;DR: In this article, a salt-rejecting evaporation structure that can operate continuously under sunlight to generate clean vapor while floating in a saline body of water such as an ocean is presented.
Abstract: Although desalination technologies have been widely adopted as a means to produce freshwater, many of them require large installations and access to advanced infrastructure. Recently, floating structures for solar evaporation have been proposed, employing the concept of interfacial solar heat localization as a high-efficiency approach to desalination. However, the challenge remains to prevent salt accumulation while simultaneously maintaining heat localization. This paper presents an experimental demonstration of a salt-rejecting evaporation structure that can operate continuously under sunlight to generate clean vapor while floating in a saline body of water such as an ocean. The evaporation structure is coupled with a low-cost polymer film condensation cover to produce freshwater at a rate of 2.5 L m−2 day−1, enough to satisfy individual drinking needs. The entire system's material cost is $3 m−2 – over an order of magnitude lower than conventional solar stills, does not require energy infrastructure, and can provide cheap drinking water to water-stressed and disaster-stricken communities.
599 citations
TL;DR: A thermochromic solar cell for smart photovoltaic window applications utilizing the structural phase transitions in inorganic halide perovskite caesium lead iodide/bromide is demonstrated.
Abstract: Smart photovoltaic windows represent a promising green technology featuring tunable transparency and electrical power generation under external stimuli to control the light transmission and manage the solar energy. Here, we demonstrate a thermochromic solar cell for smart photovoltaic window applications utilizing the structural phase transitions in inorganic halide perovskite caesium lead iodide/bromide. The solar cells undergo thermally-driven, moisture-mediated reversible transitions between a transparent non-perovskite phase (81.7% visible transparency) with low power output and a deeply coloured perovskite phase (35.4% visible transparency) with high power output. The inorganic perovskites exhibit tunable colours and transparencies, a peak device efficiency above 7%, and a phase transition temperature as low as 105 °C. We demonstrate excellent device stability over repeated phase transition cycles without colour fade or performance degradation. The photovoltaic windows showing both photoactivity and thermochromic features represent key stepping-stones for integration with buildings, automobiles, information displays, and potentially many other technologies.
578 citations
TL;DR: In this article, the authors reviewed the methods for enhancing thermal conductivity of phase change materials (PCMs), which include adding additives with high thermal conductivities and encapsulating phase change material.
Abstract: In recent years, energy conservation and environmental protection have become most important issues for humanity. Phase change materials (PCMs) for thermal energy storage can solve the issues of energy and environment to a certain extent, as PCMs can increase the efficiency and sustainability of energy. PCMs possess large latent heat, and they store and release energy at a constant temperature during the phase change process. Thereby PCMs have gained a wide range of applications in various fields, such as buildings, solar energy systems, power systems and military industry. However, low thermal conductivity of PCMs leads to low heat transfer rate, thus, numerous studies have been carried out to improve thermal conductivity of PCMs. The main purpose of this paper is to review the methods for enhancing thermal conductivity of PCMs, which include adding additives with high thermal conductivity and encapsulating phase change materials. It is found that addition of thermal conductivity enhancement fillers is a more effective method to improve thermal conductivity of PCMs, where carbon-based material additives possess a more promising application prospect. Finally, the applications of PCMs in solar energy system, buildings, cooling system, textiles and heat recovery system are also analyzed.
538 citations
TL;DR: In this article, the potential of plasmonic nanostructures in photoelectrolysis was reviewed and their potential in photo-splitting was shown to increase the efficiency of solar water splitting.
Abstract: Solar water splitting by semiconductor based photoanodes and photocathodes is one of the most promising strategies to convert solar energy to chemical energy to meet the high demand for energy consumption in modern society. However, the state-of-the-art efficiency is too low to fulfill the demand. To overcome this challenge and thus enable the industrial realization of a solar water splitting device, different approaches have been taken to enhance the overall device efficiency, one of which is the incorporation of plasmonic nanostructures. Photoanodes and photocathodes coupled to the optimized plasmonic nanostructures, matching the absorption wavelength of the semiconductors, can exhibit a significantly increased efficiency. So far, gold and silver have been extensively explored to plasmonically enhance water splitting efficiency, with disadvantages of high cost and low enhancement. Instead, non-noble plasmonic metals such as aluminum and copper, are earth-abundant and low cost. In this article, we review their potentials in photoelectrolysis, towards scalable applications.
479 citations
TL;DR: An extremely simple and standalone solar energy converter consisting of only an as-prepared 3D cross-linked honeycomb graphene foam material without any other supporting components is demonstrated, providing a paradigm change in water purification by using a simple, point of use, reusable, and low-cost solar thermal water purifying system for a variety of environmental conditions.
Abstract: Harvesting solar energy for desalination and sewage treatment has been considered as a promising solution to produce clean water. However, state-of-the-art technologies often require optical concentrators and complicated systems with multiple components, leading to poor efficiency and high cost. Here, we demonstrate an extremely simple and standalone solar energy converter consisting of only an as-prepared 3D cross-linked honeycomb graphene foam material without any other supporting components. This simple all-in-one material can act as an ideal solar thermal converter capable of capturing and converting sunlight into heat, which in turn can distill water from various water sources into steam and produce purified water under ambient conditions and low solar flux with very high efficiency. High specific water production rate of 2.6 kg h–1 m–2 g–1 was achieved with near ∼87% under 1 sun intensity and >80% efficiency even under ambient sunlight (<1 sun). This scalable sheet-like material was used to obtain p...
475 citations
TL;DR: In this paper, the authors reviewed the sources of energy-related emissions, risks of climate change, global solar energy potential, sustainability indicators of renewable energies, environmental impacts of fossil fuels and renewable energies and benefits of solar energy utilization.
Abstract: The growing global demand for energy from fossil fuels plays a key role in the upward trend in greenhouse gas (GHG) emissions and air pollutants. Rapid population growth and increasing energy demand in the developing countries have brought many concerns such as poverty, pollution, health and environmental problems. While for these countries, particularly the poorest ones, modern energy is necessary to stimulate production, income generation and social development plus reduce the serious health issues that are caused by the use of fuelwood, charcoal, animal dung and agricultural waste. Solar energy is the best answer to energy poverty and it can provide excellent opportunities for reduction of GHG emissions and indoor air pollution through substituting kerosene for lighting and firewood for cooking. Solar photovoltaic (PV) can be an appropriate technology for a source of renewable electricity in developing nations especially in remote rural areas where grid extensions are financially or technically not viable. PV can also be used to reduce demand for fossil fuels and associated emissions, including carbon dioxide (CO2), nitrogen oxides (NOx) and sulfur dioxide (SO2). The use of PV systems can reduce 69–100 million tons of CO2, 126,000–184,000 t of SO2 and 68,000–99,000 t of NOx by 2030. In case countries use concentrating solar power (CSP) systems, each square meter of concentrator surface is enough to save about 200–300 kg (kg) of CO2 emissions annually. Although there are excellent renewable opportunities in many developing countries, several key barriers have prevented large-scale deployment of solar energy technologies in these countries. This study reviews the sources of energy-related emissions, risks of climate change, global solar energy potential, sustainability indicators of renewable energies, environmental impacts of fossil fuels and renewable energies, benefits of solar energy utilization. It also discusses barriers to widespread use of solar energy.
TL;DR: In this article, the photothermal effect has been used as a novel strategy to augment vaporization and catalysis performance, and the design of efficient photothermal conversion materials in terms of both light harvesting and thermal management.
Abstract: Solar energy is a major source of renewable energy with the potential to meet the energy demand and to support the sustainable development of the world. The efficient harvesting and conversion of solar energy is one of the key factors to maximize the utilization of solar energy. In general, solar energy can be harnessed and converted into various kinds of energy, including electricity, fuels and thermal energy, through photovoltaic, photochemical and photothermal processes, respectively. Among these technologies, photothermal conversion is a direct conversion process that has attained the highest achievable conversion efficiency. The photothermal effect has been used as a novel strategy to augment vaporization and catalysis performance. In this review, we look into the basis of the photothermal conversion process, the design of efficient photothermal conversion materials in terms of both light harvesting and thermal management, a fundamental understanding of various system schemes, and the recent progress in photothermal evaporation and catalysis applications. This review aims to afford researchers with a better understanding of the photothermal effect and provide a guide for the rational design and development of highly efficient photothermal materials in energy and environmental fields.
TL;DR: This work presents detailed protocols for preparing PSCs in regular (n–i–p) and inverted (p–i-n) architectures with ≥20% PCE and encourages the practice of reporting detailed and transparent protocols that can be more easily reproduced by other laboratories.
Abstract: Perovskite solar cells (PSCs) are currently one of the most promising photovoltaic technologies for highly efficient and cost-effective solar energy production. In only a few years, an unprecedented progression of preparation procedures and material compositions delivered lab-scale devices that have now reached record power conversion efficiencies (PCEs) higher than 20%, competing with most established solar cell materials such as silicon, CIGS, and CdTe. However, despite a large number of researchers currently involved in this topic, only a few groups in the world can reproduce >20% efficiencies on a regular n–i–p architecture. In this work, we present detailed protocols for preparing PSCs in regular (n–i–p) and inverted (p–i–n) architectures with ≥20% PCE. We aim to provide a comprehensive, reproducible description of our device fabrication protocols. We encourage the practice of reporting detailed and transparent protocols that can be more easily reproduced by other laboratories. A better reporting sta...
TL;DR: In 2017, global CO2 emissions from burning fossil fuels reached 33 gigatons, twice the natural rate at which CO2 is absorbed back into land and ocean sinks as mentioned in this paper.
TL;DR: In this article, the mass and energy circulation in the solar-hydrogen-electricity circle are delineated, and different strategies for light-driven water splitting proposed in laboratories are introduced, the progress of electrocatalytic hydrogen and oxygen evolution reactions are reviewed, and finally, the reactions in hydrogen fuel cells are briefly discussed.
Abstract: Artificial photosynthesis provides a blueprint to harvest solar energy to sustain the future energy demands. Solar-driven water splitting, converting solar energy into hydrogen energy, is the prototype of photosynthesis. Various systems have been designed and evaluated to understand the reaction pathways and/or to meet the requirements of potential applications. In solar-to-hydrogen conversion, electrocatalytic hydrogen and oxygen evolution reactions are key research areas that are meaningful both theoretically and practically. To utilize hydrogen energy, fuel cell technology has been extensively investigated because of its high efficiency in releasing chemical energy. In this review, general concepts of the photosynthesis in green plants are discussed, different strategies for the light-driven water splitting proposed in laboratories are introduced, the progress of electrocatalytic hydrogen and oxygen evolution reactions are reviewed, and finally, the reactions in hydrogen fuel cells are briefly discussed. Overall, the mass and energy circulation in the solar-hydrogen-electricity circle are delineated. The authors conclude that attention from scientists and engineers of relevant research areas is still highly needed to eliminate the wide disparity between the aspirations and realities of artificial photosynthesis.
TL;DR: In this article, a bulk-passivation strategy via incorporation of chlorine, to enlarge grains and reduce electronic disorder in mixed tin-lead low-bandgap perovskite absorber layers is reported.
Abstract: Multi-junction all-perovskite tandem solar cells are a promising choice for next-generation solar cells with high efficiency and low fabrication cost. However, the lack of high-quality low-bandgap perovskite absorber layers seriously hampers the development of efficient and stable two-terminal monolithic all-perovskite tandem solar cells. Here, we report a bulk-passivation strategy via incorporation of chlorine, to enlarge grains and reduce electronic disorder in mixed tin–lead low-bandgap (~1.25 eV) perovskite absorber layers. This enables the fabrication of efficient low-bandgap perovskite solar cells using thick absorber layers (~750 nm), which is a requisite for efficient tandem solar cells. Such improvement enables the fabrication of two-terminal all-perovskite tandem solar cells with a champion power conversion efficiency of 21% and steady-state efficiency of 20.7%. The efficiency is retained to 85% of its initial performance after 80 h of operation under continuous illumination. Two-terminal monolithic all-perovskite tandem solar cells are attractive due to their flexible nature and low-cost fabrication. Here the authors develop a process to obtain high-quality Sn–Pb perovskite thin films by incorporating chlorine. Such layers are employed to fabricate 20.7%-efficient tandem cells with 80 h operational stability.
TL;DR: In this paper, the authors focused on the heterogeneous photocatalytic water splitting and on CO2 reduction with nanostructured semiconductors, metals, and their hybrids.
Abstract: The inexorable rise of carbon dioxide level in the atmosphere, already exceeding 400 ppm, highlights the need for reduction of CO2 emissions. Harvesting solar energy to drive reverse chemical reactions to fuel combustion offers a possible solution. The produced chemical fuels (e.g. hydrogen, methane, or methanol) are also a convenient means of energy storage, not available in photovoltaic cells. This Review is focused on the heterogeneous photocatalytic water splitting and on CO2 reduction with nanostructured semiconductors, metals, and their hybrids. The stages of light absorption, charge separation and transfer, and surface reactions are discussed, together with possible energy-loss mechanisms and means of their elimination. Many novel materials have been developed in this active field of research, and this Review describes the concepts underpinning the continued progress in the field. The approaches which hold promise for substantial improvement in terms of efficiency, cost, and environmental sustainab...
TL;DR: In this article, the authors investigated the recent advances in the nanofluids' applications in solar energy systems, i.e., solar collectors, photovoltaic/thermal (PV/T) systems, solar thermoelectric devices, solar water heaters, solar-geothermal combined cooling heating and power system (CCHP), evaporative cooling for greenhouses, and water desalination.
Abstract: Solar energy systems (SESs) are considered as one of the most important alternatives to conventional fossil fuels, due to its ability to convert solar energy directly into heat and electricity without any negative environmental impact such as greenhouse gas emissions. Utilizing nanofluid as a potential heat transfer fluid with superior thermophysical properties is an effective method to enhance the thermal performance of solar energy systems. The purpose of this review paper is the investigation of the recent advances in the nanofluids’ applications in solar energy systems, i.e., solar collectors (SCs), photovoltaic/thermal (PV/T) systems, solar thermoelectric devices, solar water heaters, solar-geothermal combined cooling heating and power system (CCHP), evaporative cooling for greenhouses, and water desalination.
TL;DR: All the latest reported technologies from the year 2007 onwards on transparent photovoltaic technologies with at least 20% average transmission are state to provide a crucial review on the latest developments in the field of TSCs.
Abstract: Energy is essential for economic development and growth. With the rapid growth of development and the drive to expand the economy, society demands more electricity. Coupled with the realisation that unsustainable energy production can have a detrimental effect on our environment. Solar energy is the most prolific method of energy capture in nature. The economic drive to make solar cells more cost effective and efficient has driven developments in many different deposition technologies, including dipping, plating, thick film deposition and thin film deposition. Typically, in order for solar energy to work efficiently and supply energy to a building, a very large amount of space is required, in the form of rooftops or land, in order to install solar panels; these solar panel space requirements are a large impediment to practical usage. This drawback drove researchers to come up with transparent solar cells (TSCs), which solves the problem by turning any sheet of glass into a photovoltaic solar cell. These cells provide power by absorbing and utilising unwanted light energy through windows in buildings and automobiles, which leads to an efficient use of architectural space. There are approximately nine transparent photovoltaic (TPV) technologies under development, and studies regarding these technologies aim to achieve high transparency along with electrical performance that is compatible with solar panels that are sold in the market. The main objective of this review paper is to state all the latest reported technologies from the year 2007 onwards on transparent photovoltaic technologies with at least 20% average transmission. This includes demonstrating the process used in each technology (including the materials and the methods) and explaining its advantages and disadvantages from a performance, aesthetic and financial perspective. Therefore, this study provides a crucial review on the latest developments in the field of TSCs.
TL;DR: The all-nanofiber aerogel presents a new route for designing biodegradable, sustainable, and scalable solar steam generation devices with superb performance.
Abstract: The global fresh water shortage has driven enormous endeavors in seawater desalination and wastewater purification; among these, solar steam generation is effective in extracting fresh water by efficient utilization of naturally abundant solar energy. For solar steam generation, the primary focus is to design new materials that are biodegradable, sustainable, of low cost, and have high solar steam generation efficiency. Here, we designed a bilayer aerogel structure employing naturally abundant cellulose nanofibrils (CNFs) as basic building blocks to achieve sustainability and biodegradability as well as employing a carbon nanotube (CNT) layer for efficient solar utilization with over 97.5% of light absorbance from 300 to 1200 nm wavelength. The ultralow density (0.0096 g/cm3) of the aerogel ensures that minimal material is required, reducing the production cost while at the same time satisfying the water transport and thermal-insulation requirements due to its highly porous structure (99.4% porosity). Owi...
TL;DR: In this paper, a critical survey of the recent progress in perovskite absorber and charge transport materials that account for the exceptionally higher PCE of perovsite devices is presented.
Abstract: The breakthrough discovery of organic-inorganic hybrid perovskite materials for converting solar energy into electrical energy has revolutionized the third generation photovoltaic devices. Within less than half a decade of rigorous research and development in perovskite solar cells, the efficiency is boosted upto 22%. Aforesaid high PCE is accredited to high optical absorption properties, balanced charge transport properties, and longer diffusion lengths of carriers. Two dominant perovskite solar cell architecture has evolved; n-i-p, and p-i-n with mesoporous or planar heterojunction. In planar heterojunction configuration, perovskite light harvester is layered between hole/electron transport layers and the electrodes. The electron and hole transporting films increase charge collection efficiency and reduce recombination at interfaces. In the following review, we present a critical survey of the recent progress in perovskite absorber and charge transport materials that account for the exceptionally higher PCE of perovskite devices. Furthermore, numerous fabrication techniques and device architectures are summarized.
TL;DR: In this paper, phase change materials (PCMs) can be applied to several different solar energy systems for the extended heat energy storage which is quite useful as the solar energy is intermittent in nature and is unavailable during the night period.
Abstract: Phase change materials (PCMs) can be applied to several different solar energy systems for the extended heat energy storage which is quite useful as the solar energy is intermittent in nature and is unavailable during the night period Application of PCMs in solar energy systems allows the solar energy to be used at any time even in the absence of the natural solar radiation Thus, the use of PCMs in the solar energy systems can bridge the demand and supply gap of the normal electrical energy This paper deals with the recent advances in PCMs application in different solar energy systems and presents almost all of the emerging areas where the applications of PCM in solar energy systems are urgently required The novel and most recent developments of PCMs in solar thermal energy systems, such as, solar thermal power plants, solar air heater, solar water heater and solar cooker have been duly covered Furthermore, the application of PCMs in heating and cooling of buildings have been presented as well as the investigation of the PCM application in the solar photovoltaic systems for the performance enhancement of PCMs Intrinsically important, from the study it has been found that PCMs have been in use in almost all of the solar energy systems even though their uses are still limited and commercially not available due to several economic and environmental constraints Thus, the paper attempts to present recent and novel approaches by the authors around the world on PCMs applications in the solar energy in well documented forms Based on the findings, future recommendations have also been given to provide the idea and pragmatic concepts for the researcher to work on the areas of research for further improvements in the systems
TL;DR: In this article, the main challenges in photocatalytic CO2 reduction systems and strategies to improve the efficiency of solar fuels production were discussed. And the challenges lingering on against achieving the higher photocalytic conversion of CO2 into solar fuels are also investigated.
Abstract: The massive burning of fossil fuels to fulfill the augmenting energy demands of world have triggered the ever-increasing emission of carbon dioxide (CO2); the main cause of global warming. Photocatalytic reduction of CO2 into solar fuels and chemicals using everlasting solar energy seems promising technology to contemporaneously curb the globa1 warming and partially fulfill the energy requirements. This study focused on understanding the main challenges in photocatalytic CO2 reduction systems and strategies to improve the efficiency of solar fuels production. The overview of fundamentals and latest developments in titania (TiO2) based photocatalytic CO2 reduction systems have been discussed. More specifically, thermodynamics, mass transfer, selectivity and reaction mechanism of photocatalytic CO2 reduction are critically deliberated. In the main stream, developments have been categorized as strategies to enhance the different aspects such as visible light response, charge separation, CO2 adsorption and morphology of photo-catalysts for TiO2 based photocatalytic CO2 reduction systems. Different modification techniques to overcome the low efficiency by fabricating advance TiO2 nanocomposites through surface modifications, doping of metals, non-metals and semiconductor are discussed. The challenges lingering on against achieving the higher photocatalytic conversion of CO2 into solar fuels are also investigated. In conclusion, brief perspectives and recommendations on the development of efficient photocatalysts are outlined which would be of vital importance for the improvements of conversion efficiency of CO2 reduction system.
TL;DR: In this article, the most recent advances of nanofluids in thermal energy storage systems, solar collectors, solar stills, and photovoltaic/thermal systems are presented.
TL;DR: In this paper, the evolution in the understanding of point defect behavior from Si-based photovoltaics to thin-film CdTe and Cu(In,Ga)Se2 technologies, through to the latest generation of halide perovskite (CH3NH3PbI3) and kesterite (Cu2ZnSnS4) devices, is reviewed.
Abstract: Control of defect processes in photovoltaic materials is essential for realizing high-efficiency solar cells and related optoelectronic devices. Native defects and extrinsic dopants tune the Fermi level and enable semiconducting p–n junctions; however, fundamental limits to doping exist in many compounds. Optical transitions from defect states can enhance photocurrent generation through sub-bandgap absorption; however, these defect states are also often responsible for carrier trapping and non-radiative recombination events that limit the voltage in operating solar cells. Many classes of materials, including metal oxides, chalcogenides and halides, are being examined for next-generation solar energy applications, and each technology faces distinct challenges that could benefit from point defect engineering. Here, we review the evolution in the understanding of point defect behaviour from Si-based photovoltaics to thin-film CdTe and Cu(In,Ga)Se2 technologies, through to the latest generation of halide perovskite (CH3NH3PbI3) and kesterite (Cu2ZnSnS4) devices. We focus on the chemical bonding that underpins the defect chemistry and the atomistic processes associated with the photophysics of charge-carrier generation, trapping and recombination in solar cells. Finally, we outline general principles to enable defect control in complex semiconducting materials. Point defects have a key role in determining the performance of photovoltaic materials. In this Review, we assess defect processes in a range of photovoltaic materials and outline how point defect engineering could be used to improve the efficiency of solar cells.
TL;DR: A state-of-the-art account on the recent advancements in solar thermal fuels based on azobenzene photoswitches and their fundamentals and new perspectives on the future scope, opportunities and challenges are provided.
Abstract: Development of renewable energy technologies has been a significant area of research amongst scientists with the aim of attaining a sustainable world society Solar thermal fuels that can capture, convert, store, and release solar energy in the form of heat through reversible photoisomerization of molecular photoswitches such as azobenzene derivatives are currently in the limelight of research Herein, we provide a state-of-the-art account on the recent advancements in solar thermal fuels based on azobenzene photoswitches We begin with an overview on the importance of azobenzene-based solar thermal fuels and their fundamentals Then, we highlight the recent advances in diverse azobenzene materials for solar thermal fuels such as pure azobenzene derivatives, nanocarbon-templated azobenzene, and polymer-templated azobenzene The basic design concepts of these advanced solar energy storage materials are discussed, and their promising applications are highlighted We then introduce the recent endeavors in the molecular design of azobenzene derivatives toward efficient solar thermal fuels, and conclude with new perspectives on the future scope, opportunities and challenges It is expected that continuous pioneering research involving scientists and engineers from diverse technological backgrounds could trigger the rapid advancement of this important interdisciplinary field, which embraces chemistry, physics, engineering, nanoscience, nanotechnology, materials science, polymer science, etc
TL;DR: The optimization results demonstrate that a wind and solar energy based hybrid system with electrochemical storage offers more cost effective and reliable energy than a hybrid system for renewable energy with chemical storage.
TL;DR: This review presents the forefront achievements in visible- NIR photon capture and promotes the development of novel visible-NIR photon harnessing catalysts toward efficient solar energy utilization.
Abstract: Utilization of diffusive solar energy through photocatalytic processes for environmental purification and fuel production has long been pursued. However, efficient capture of visible-near-infrared (NIR) photons, especially for those with wavelengths longer than 600 nm, is a demanding quest in photocatalysis owing to their relatively low energy. In recent years, benefiting from the advances in photoactive material design, photocatalytic reaction system optimization, and new emerging mechanisms for long-wavelength photon activation, increasing numbers of studies on the harnessing of visible-NIR light for solar-to-chemical energy conversion have been reported. Here, the aim is to comprehensively summarize the progress in this area. The main strategies of the long-wavelength visible-NIR photon capture and the explicitly engineered material systems, i.e., narrow optical gap, photosensitizers, upconversion, and photothermal materials, are elaborated. In addition, the advances in long-wavelength light-driven photo- and photothermal-catalytic environmental remediation and fuel production are discussed. It is anticipated that this review presents the forefront achievements in visible-NIR photon capture and at the same time promotes the development of novel visible-NIR photon harnessing catalysts toward efficient solar energy utilization.
TL;DR: A comprehensive overview of major advances in the synthesis of core-shell structured TiO2 nanomaterials for solar energy utilization and their applications in photocatalysis, water splitting, photocatalytic CO2 reduction, solar cells and photothermal conversion is provided.
Abstract: Because of its unmatched resource potential, solar energy utilization currently is one of the hottest research areas. Much effort has been devoted to developing advanced materials for converting solar energy into electricity, solar fuels, active chemicals, or heat. Among them, TiO2 nanomaterials have attracted much attention due to their unique properties such as low cost, nontoxicity, good stability and excellent optical and electrical properties. Great progress has been made, but research opportunities are still present for creating new nanostructured TiO2 materials. Core–shell structured nanomaterials are of great interest as they provide a platform to integrate multiple components into a functional system, showing improved or new physical and chemical properties, which are unavailable from the isolated components. Consequently, significant effort is underway to design, fabricate and evaluate core–shell structured TiO2 nanomaterials for solar energy utilization to overcome the remaining challenges, for example, insufficient light absorption and low quantum efficiency. This review strives to provide a comprehensive overview of major advances in the synthesis of core–shell structured TiO2 nanomaterials for solar energy utilization. This review starts from the general protocols to construct core–shell structured TiO2 nanomaterials, and then discusses their applications in photocatalysis, water splitting, photocatalytic CO2 reduction, solar cells and photothermal conversion. Finally, we conclude with an outlook section to offer some insights on the future directions and prospects of core–shell structured TiO2 nanomaterials and solar energy conversion.
TL;DR: An example with near perfect energy conversion efficiency in the process of solar vapor generation below room temperature is reported, when the operational temperature of the system is below that of the surroundings and the total vapor generation rate is higher than the upper limit that can be produced by the input solar energy because of extra energy taken from the warmer environment.
Abstract: 100% efficiency is the ultimate goal for all energy harvesting and conversion applications. However, no energy conversion process is reported to reach this ideal limit before. Here, an example with near perfect energy conversion efficiency in the process of solar vapor generation below room temperature is reported. Remarkably, when the operational temperature of the system is below that of the surroundings (i.e., under low density solar illumination), the total vapor generation rate is higher than the upper limit that can be produced by the input solar energy because of extra energy taken from the warmer environment. Experimental results are provided to validate this intriguing strategy under 1 sun illumination. The best measured rate is ≈2.20 kg m-2 h-1 under 1 sun illumination, well beyond its corresponding upper limit of 1.68 kg m-2 h-1 and is even faster than the one reported by other systems under 2 sun illumination.