Electricity generated using photovoltaic (PV) technology can only be economical if the PV modules operate reliably for 25–30 years under field conditions. In order to ensure such levels of ...reliability PV module undergo stringent qualification tests developed as per international standards by International Electro-technical Commission. These tests provide excellent information regarding module design, material and process flaws which can lead to premature failure. Even the well qualified modules are found to fail or degrade more than their expected levels when exposed to the outdoor conditions, indicating that these tests are not adequately addressing the real outdoor conditions and are not sufficient to estimate the module lifetime. Keeping in view this aspect, the performance and degradation analysis studies of solar photovoltaic modules, accelerated aging testing under laboratory and outdoor field testing conditions, are reviewed. The factors affecting the performance of PV module, PV module degradation modes, stress factors responsible for degradation, accelerated aging tests and current PV module qualification standard tests are also discussed along with recently used techniques for the failure mode analysis of PV modules. The main objective of the study is to review the literature on performance and degradation of PV modules under outdoor operation for identifying research gaps for long term reliability of PV modules and improving the PV qualification standards for various geographical and climatic conditions.
Solar radiation data plays an important role in solar energy research. These data are not available for location of interest due to absence of a meteorological station. Therefore, the solar radiation ...has to be predicted accurately for these locations using various solar radiation estimation models. The main objective of this study is to review Artificial Neural Network (ANN) based techniques in order to identify suitable methods available in the literature for solar radiation prediction and to identify research gaps. The study shows that Artificial Neural Network techniques predict solar radiation more accurately in comparison to conventional methods. The prediction accuracy of ANN models is found to be dependent on input parameter combinations, training algorithm and architecture configurations. Further research areas in ANN technique based methodologies are also identified in the present study.
Oxidative stress refers to elevated intracellular levels of reactive oxygen species (ROS) that cause damage to lipids, proteins and DNA. Oxidative stress has been linked to a myriad of pathologies. ...However, elevated ROS also act as signaling molecules in the maintenance of physiological functions — a process termed redox biology. In this review we discuss the two faces of ROS — redox biology and oxidative stress — and their contribution to both physiological and pathological conditions. Redox biology involves a small increase in ROS levels that activates signaling pathways to initiate biological processes, while oxidative stress denotes high levels of ROS that result in damage to DNA, protein or lipids. Thus, the response to ROS displays hormesis, given that the opposite effect is observed at low levels compared with that seen at high levels. Here, we argue that redox biology, rather than oxidative stress, underlies physiological and pathological conditions.
Schieber and Chandel discuss the two faces of reactive oxygen species — redox biology and oxidative stress — and their contribution to both physiological and pathological conditions.
The deficit in electricity and high diesel costs affects the pumping requirements of community water supplies and irrigation; so using solar energy for water pumping is a promising alternative to ...conventional electricity and diesel based pumping systems. Solar water pumping is based on photovoltaic (PV) technology that converts solar energy into electrical energy to run a DC or AC motor based water pump. The main objective of the study is to present a comprehensive literature review of solar pumping technology, evaluate the economic viability, identify research gaps and impediments in the widespread propagation of solar water pumping systems and technology. The study focuses on update on solar water pumping technology, performance analysis, optimum sizing, degradation of PV generator supplying power to pump, economic and environmental aspects and advances in PV materials and efficiency improvements. An update on the current state of research and utilization of solar water pumping technology is presented. Factors affecting performance of PV water pumping system, degradation of PV modules and efficiency improving techniques of PV water pumping systems are identified. Solar water pumping is found to be economically viable in comparison to electricity or diesel based systems for irrigation and water supplies in rural, urban and remote regions. The investment payback for some PV water pumping systems is found to be 4–6 years. The recent Indian incentives for PV pumping and policy initiatives for the promotion of solar water pumping in developing countries are also discussed. Potential follow-up research areas are also identified.
Hybrid energy systems are being utilized for supplying electrical energy in urban, rural and remote areas to overcome the intermittence of solar and wind resources. A hybrid renewable energy system ...incorporates two or more electricity generation options based on renewable energy or fossil fuel unit. The techno-economic analysis of the hybrid system is essential for the efficient utilization of renewable energy resources. Due to multiple generation systems, hybrid system analysis, is quite complex and requires to be analyzed thoroughly. This requires software tools for the design, analysis, optimization, and economic viability of the systems. In this paper, 19 softwares with their main features and current status are presented. The softwares studied are HOMER, Hybrid2, RETScreen, iHOGA, INSEL, TRNSYS, iGRHYSO, HYBRIDS, RAPSIM, SOMES, SOLSTOR, HySim, HybSim, IPSYS, HySys, Dymola/Modelica, ARES, SOLSIM, and HYBRID DESIGNER. The research work related to hybrid systems carried out using these softwares at different locations worldwide is also reviewed. The main objective of the paper is to provide the current status of these softwares to provide basic insight for a researcher to identify and utilize suitable tool for research and development studies of hybrid systems. The capabilities of different softwares are also highlighted. The limitations, availability and areas of further research have also been identified.
The performance analysis of a 190 kWp solar photovoltaic power plant installed at Khatkar-Kalan, India, is carried out. The final yield, reference yield and performance ratio, are found to vary from ...1.45 to 2.84 kWh/kWp-day, 2.29 to 3.53 kWh/kWp-day and 55–83% respectively. The annual average performance ratio, capacity factor and system efficiency are found to be 74%, 9.27% and 8.3% respectively. The average annual measured energy yield of the plant is found to be 812.76 kWh/kWp. The average annual predicted energy yield is found to be 823 kWh/kWp using PVSYST. The estimated energy yield is in close agreement with measured results with an uncertainty of 1.4%. The total estimated system losses due to irradiance, temperature, module quality, array mismatch, ohmic wiring and inverter, are found to be 31.7%. The study shows that energy generated is maximum during March, September, and October and minimum in January. The performance of the system is compared with PV systems installed worldwide and found comparable. The results presented provide insight to the long-term performance of the solar power plant under actual operating conditions in India. The need for optimizing solar panel inclination is emphasized for maximizing power generation. Further, follow-up research studies are also identified.
•Performance analysis of the first 190 kWp grid interactive solar photovoltaic power plant installed in India, is carried out.•Reference yield, final yield, performance ratio and the capacity factor of PV plant, are evaluated.•Performance of this system is found comparable with other PV systems installed worldwide.•The estimated energy yield is found to be in close agreement with measured yield of the solar plant.•Results provide an insight to the long-term performance of the solar power plant under actual operating conditions.
Mitochondria have primarily been viewed as bioenergetic and biosynthetic organelles that autonomously co-exist within the cell. However, the past two decades have provided evidence that mitochondria ...function as signaling organelles, constantly communicating with the cytosol to initiate biological events under homeostatic and stress conditions. Thus, the signaling function of the mitochondria may have been selected by nature from the inception of the early eukaryote, as discussed in this essay.
Mitochondria are well appreciated for their robust bioenergetic and biosynthetic capacities. A third emerging facet is their critical function as signaling organelles regulating biological, physiological, and pathological outcomes. In this Essay, Chandel speculates on how mitochondria evolved to regulate signal transduction and highlights the burgeoning field of mitochondrial signaling.
Phase change materials (PCM) are widely used for energy storage applications worldwide. The objective of the study is to review the current state of research on PCM materials, energy storage, ...environmental aspects and identifying potential research areas which needs focus to make this technology widely marketable and economically promising. The paper presents PCM research status, material properties, microencapsulation, shape stabilization techniques, commercial applications and environmental issues and also covers areas which have not been given much attention in previous studies like toxicity, health hazards, fire retardation techniques and current market scenario. The study shows that salt hydrates are safe if carefully handled and commercial grade paraffins being flammable, release toxic vapors thus are potential health hazard so need to be used carefully. Further research on fire retardation of PCM is found lacking in literature. Critical issues to ensure long term performance, are discussed which will help researchers to identify appropriate PCM for different commercial applications. New innovative PCM materials are identified although these are not used in real applications as yet. The commercial potential of PCM products is presented which shows that these materials have promising solutions for textiles, heat or cold storage during transits, pain relief packs, vaccine and blood storage where maintenance of a critical temperature is important. These materials could significantly cut down the air conditioning demands in future provided the current challenges are met. With increased awareness and stricter environmental regulations in future, PCM market potential is expected to rise.
A significant fraction of the solar radiation falling on photovoltaic (PV) panels gets converted into heat thus reducing the efficiency of photovoltaic power plants. Generally the performance of PV ...panels falls by 0.5% for every degree rise in temperature, depending on the type of solar cells used. The temperature regulation of PV power systems therefore becomes important especially for areas experiencing consistently high temperatures to improve PV efficiency. The objective of the study is to review literature on photovoltaic cooling techniques using phase change materials (PCM) including PV-thermal systems and building integrated photovoltaic systems. The main aim is to identify important research areas to ensure reliable performance and commercially viability of the technology. Various parameters are required to be evaluated and optimized for the geographical location of interest to obtain the best output. Increase in electrical efficiency as high as 5% is observed with PV-PCM integrated systems. Study suggests that inorganic PCMs have a good potential for PV cooling. PCM based PV systems will be cost effective only for areas with high insolation year round with less inter-seasonal climatic variations. However, poor thermal conductivity and large undercooling are major problems associated with PCM. There are only few studies on performance testing, economic benefit identification, increase in PV panel lifetime and LCA analysis for testing the suitability of PCM as coolant for PV panels. In this study the research gaps are identified for follow up work. Market review suggests that PCM based PV cooling technology is not yet commercialized due to its inefficiency primarily because of technological challenges, high system costs and non-availability of reliable operating designs. The study suggests that PCM is still not an economic cooling technique for PV systems and further research is required.
Mitochondria are well appreciated for their role as biosynthetic and bioenergetic organelles. In the past two decades, mitochondria have emerged as signaling organelles that contribute critical ...decisions about cell proliferation, death, and differentiation. Mitochondria not only sustain immune cell phenotypes but also are necessary for establishing immune cell phenotype and their function. Mitochondria can rapidly switch from primarily being catabolic organelles generating ATP to anabolic organelles that generate both ATP and building blocks for macromolecule synthesis. This enables them to fulfill appropriate metabolic demands of different immune cells. Mitochondria have multiple mechanisms that allow them to activate signaling pathways in the cytosol including altering in AMP/ATP ratio, the release of ROS and TCA cycle metabolites, as well as the localization of immune regulatory proteins on the outer mitochondrial membrane. In this Review, we discuss the evidence and mechanisms that mitochondrial dependent signaling controls innate and adaptive immune responses.
Mitochondria participate in immune-cell signaling through production of reactive oxygen species, metabolite availability, and by physically acting as scaffolding for protein interaction. Chandel and colleagues provide an overview of these data and propose that mitochondrial metabolism is a central regulator of immune-cell fate and function.
PDF
