•Thermal model of a PV module from both energy and exergy viewpoints.•Brief review on the impact of temperature rise on PV module performance.•Comprehensive overview on recently developed PV module ...cooling technologies.•Passive cooling technologies including the use of phase change material.•Future countenance in PV cooling research.
Photovoltaic (PV) systems operate in a paradox; sunlight is the essential input to generate electricity with PV, but they suffer a digression in performance as the operating temperature goes higher. This work is a comprehensive compilation and review of the latest literature regarding research works rendered to achieve improved efficiency through appropriate cooling systems. Most of the research goals were twofold, that is to enhance the efficiency of the solar PV systems and to ensure a longer life at the same time. The passive cooling systems are found to achieve a reduction in PV module temperature in the range of 6–20°C with an improvement in electrical efficiency up to 15.5% maximum. On the other side, active cooling systems’ performance are better, as may expected, with a reduction in PV module temperature as high as 30°C with an improvement in electrical efficiency up to 22% maximum along with additional thermal energy output with efficiency reaching as high as 60%. Based on the wide-ranging review, it may be predicted that with the swelling growth of solar PV electricity worldwide, the compatible cooling system is becoming obligatory in order to ensure better energy harvest and utilization.
Global energy demand and environmental concerns are the driving force for use of alternative, sustainable, and clean energy sources. Solar energy is the inexhaustible and CO2-emission-free energy ...source worldwide. The Sun provides 1.4×105TW power as received on the surface of the Earth and about 3.6×104TW of this power is usable. In 2012, world power consumption was 17TW, which is less than 3.6×104TW. Photovoltaic (PV) cells are the basic element for converting solar energy into electricity. PV cell technologies, energy conversion efficiency, economic analysis, energy policies, environmental impact, various applications, prospects, and progress have been comprehensively reviewed and presented in this paper. This work compiles the latest literature (i.e. journal articles, conference proceedings, and reports, among others) on PV power generation, economic analysis, environmental impact, and policies to increase public awareness. From the review, it was found that PV is an easy way to capture solar energy where PV based power generation has also rapidly increased.
Vitiligo is the most common acquired pigmentary disorder, which afflicts 0.5%–1% of the world population, and is characterized by depigmented skin patches resulting from melanocyte loss. Vitiligo has ...a complex etiology and varies in its manifestations, progression, and response to treatment. It presents as an autoimmune disease, evidenced by circulating melanocyte‐specific antibodies, and association with other autoimmune diseases. However, autoimmunity may be secondary to the high oxidative stress in vitiligo skin and to intrinsic defects in melanocytes and their microenvironment, which contribute to aberrant stress response, neo‐antigenicity, and susceptibility of melanocytes to immune attack and apoptosis. There is also a genetic predisposition to vitiligo, which sensitizes melanocytes to environmental agents, such as phenolic compounds. Currently, there are different treatment modalities for re‐pigmenting vitiligo skin. However, when repigmentation is achieved, the major challenge is maintaining the pigmentation, which is lost in 40% of cases. In this review, we present an overview of the clinical aspects of vitiligo, its pathophysiology, the intrinsic defects in melanocytes and their microenvironment, and treatment strategies. Based on lessons from the biology of human melanocytes, we present our perspective of how repigmentation of vitiligo skin can be achieved and sustained.
Human epidermal melanocytes play a central role in sensing the environment and protecting the skin from the drastic effects of solar ultraviolet radiation and other environmental toxins or ...inflammatory agents. Melanocytes survive in the epidermis for decades, which subjects them to chronic environmental insults. Melanocytes have a poor self‐renewal capacity; therefore, it is critical to ensure their survival with genomic stability. The function and survival of melanocytes is regulated by an elaborate network of paracrine factors synthesized mainly by epidermal keratinocytes and dermal fibroblasts. A symbiotic relationship exists between epidermal melanocytes and keratinocytes on the one hand, and between melanocytes and dermal fibroblasts on the other hand. Melanocytes protect epidermal keratinocytes and dermal fibroblasts from the damaging effects of solar radiation, and the latter cells synthesize biochemical mediators that maintain the homeostasis, and regulate the stress response of melanocytes. Disruption of the paracrine network results in pigmentary disorders, due to abnormal regulation of melanin synthesis, and compromise of melanocyte survival or genomic stability. This review provides an update of the current knowledge of keratinocyte‐ and fibroblast‐derived paracrine factors and their contribution to melanocyte physiology, and how their abnormal production is involved in the pathogenesis of common pigmentary disorders.
Worldwide primary energy needs are satisfied basically from non-renewable sources that are limited in supply and innately hazardous to the environment. Biomass-based power systems are very much ...potent to address the environmental issues fostering sustainable development, while being able to provide a secured and uninterrupted power supply at the same time. Biomass-based power generation systems not only reduce the GHG emissions but also have enormous opportunities of job creation and promote biomass re-growth through sustainable land management practices. This paper overviews the biomass scenario in Southeast Asian and EU countries to give an overview of the potential and scalable energy harnessed from biomass resources. Economic analyses presented on biomass gasification-based power generation have been evaluated with three specific cost estimations, namely low, average and high. Key economic performance metrics of biomass gasification-based dual-fuel internal combustion engine generator with low investment estimates are as follows: a positive net present value of USD 7.5 million; internal rate of return 14.45%; and a payback period of 5.45 years. A review of the technologies can provide a base for strategic energy policy for the next generation of sustainable energy policies and helps policymakers to frame strategies aiming for clean technology and sustainable development. Biomass integrated gasification combined cycle-based systems are found to be most suitable for power generation or biofuel synthesis.
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Amyotrophic lateral sclerosis (ALS) is the most common motor neuron disease in adults and is characterized by neurodegeneration of motor neurons in the brain and spinal cord. The incidence of ALS is ...approximately 1-2.6 cases per 100 000 persons annually, whereas the prevalence is approximately 6 cases per 100 000. The average age of onset of ALS is currently 58-60 years and the average survival from onset to death is 3-4 years. Between October 19, 2010 and December 31, 2011, there were an estimated 12 187 prevalent cases diagnosed with definite ALS in the USA alone. Sporadic ALS (90-95%) constitutes the large majority of cases, while the remaining 5-10% are hereditary and termed familial ALS. Sporadic ALS is suspected to involve genetic susceptibility to environmental risk factors. The purpose of this review is to present a clinical overview of ALS and provide an epidemiologic summary of personal and environmental risk factors shown to be related to the risk of disease. A discussion of the most recent research initiatives is also included.
This work proposes a novel fault diagnostic technique for photovoltaic systems based on Artificial Neural Networks (ANN). For a given set of working conditions - solar irradiance and photovoltaic ...(PV) module's temperature - a number of attributes such as current, voltage, and number of peaks in the current–voltage (I–V) characteristics of the PV strings are calculated using a simulation model. The simulated attributes are then compared with the ones obtained from the field measurements, leading to the identification of possible faulty operating conditions. Two different algorithms are then developed in order to isolate and identify eight different types of faults. The method has been validated using an experimental database of climatic and electrical parameters from a PV string installed at the Renewable Energy Laboratory (REL) of the University of Jijel (Algeria). The obtained results show that the proposed technique can accurately detect and classify the different faults occurring in a PV array. This work also shows the implementation of the developed method into a Field Programmable Gate Array (FPGA) using a Xilinx System Generator (XSG) and an Integrated Software Environment (ISE).
Melanin, the pigment produced by specialized cells, melanocytes, is responsible for skin and hair color. Skin pigmentation is an important protective mechanism against the DNA damaging and mutagenic ...effects of solar ultraviolet radiation (UV). It is acknowledged that exposure to UV is the main etiological environmental factor for all forms of skin cancer, including melanoma. DNA repair capacity is another major factor that determines the risk for skin cancer. Human melanocytes synthesize eumelanin, the dark brown form of melanin, as well as pheomelanin, which is reddish-yellow in color. The relative rates of eumelanin and pheomelanin synthesis by melanocytes determine skin color and the sensitivity of skin to the drastic effects of solar UV. Understanding the complex regulation of melanocyte function and how it responds to solar UV has a huge impact on developing novel photoprotective strategies to prevent skin cancer, particularly melanoma, the most fatal form, which originates from melanocytes. This review provides an overview of the known differences in the photoprotective effects of eumelanin versus pheomelanin, how these two forms of melanin are regulated genetically and biochemically, and their impact on the DNA damaging effects of UV exposure. Additionally, this review briefly discusses the role of paracrine factors, focusing on α-melanocortin (α-melanocyte stimulating hormone; α-MSH), in regulating melanogenesis and the response of melanocytes to UV, and describes a chemoprevention strategy based on targeting the melanocortin 1 receptor (MC1R) by analogs of its physiological agonist α-MSH.
Considering that renewable energy is the primary energy source in the future, this study investigates biomass power for sustainable and secure energy supply. Biomass fuels in Malaysia include empty ...fruit bunch, mesocarp fiber, palm kernel shell, oil palm frond, oil palm trunk from palm oil plantation, and woody biomass from forests. The moisture content and heating value of palm oil-based biomass fuels are analyzed relative to their cost savings in a 10 MW biomass power plant. The net present value, internal rate of return, and payback period for various finance options and at various system efficiencies are also presented. Results indicate that for an empty fruit bunch priced at MYR 20/t without loan, the net present values are MYR 45.31 million, MYR 54.32 million, and MYR 57.74 million, with 20%, 30%, and 40% system efficiencies, respectively; the internal rates of returns are 21.88%, 22%, and 21.11%, respectively; and the payback periods are 4.16, 4.20, and 4.22 y, respectively. The 10 MW plant releases 50,130 t less CO2, 750 t less SO2, 218.65 t less NOx, and 22.83 t less CO emissions in the environment compared with the existing energy mix.
•Biomass-based power generation can secure sustainable and clean energy supply.•Moisture content of biomass affects energy conversion efficiency and cost.•Low-cost palm biomass is a potential source of biomass-based power in Malaysia.•Biomass-based power plant can save currency by reducing import of fossil fuels.•The plant can improve environmental sustainability by reducing gas emissions.
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