Solar stills:a comprehensive review of designs, performance and material advances

The demand for fresh water production is growing day by day with the increase in world population and with industrial growth. Use of desalination technology is increasing to meet this demand. Among desalination technologies, solar stills require low maintenance and are readily affordable; however their productivity is limited. This paper aims to give a detailed review about the various types of solar stills, covering passive and active designs, single- and multi-effect types, and the various modifications for improved productivity including reflectors, heat storage, fins, collectors, condensers, and mechanisms for enhancing heat and mass transfer. Photovoltaic-thermal and greenhouse type solar stills are also covered. Material advances in the area of phase change materials and nanocomposites are very promising to enhance further performance; future research should be carried out in these and other areas for the greater uptake of solar still technology

Effects of nanoparticle-enhanced phase change material (NPCM) on solar still productivity

This paper investigates the effects of nanoparticle-enhanced phase change material (NPCM) on solar still operation and performance. Technical and economic aspects were considered, to show an advance on earlier works using virgin phase-change materials (PCM). Three types of nanoparticle (TiO2, CuO and GO) were impregnated individually at 0.3 weight% in paraffin to form NPCM-1, NPCM-2 and NPCM-3 respectively. Experiments were conducted with four solar stills (SS) each of 0.5 m2 area using respectively paraffin (SSPCM), paraffin-TiO2 (SSNPCM-1), paraffin-CuO (SSNPCM-2) and paraffin-GO (SSNPCM-3). There was observed an increase in thermal conductivity and a reduction in melting and solidification temperatures, with NPCM compared to PCM. The effects of NPCM on water temperature, storage temperature, hourly and annual productivity were determined. SSPCM, SSNPCM-1, SSNPCM-2 and SSNPCM-3 yielded 3.92, 4.94, 5.28 and 3.66 l/m2/day respectively, corresponding to 26 and 35% increases in productivity of SSNPCM-1 and 2 respectively over SSPCM. Economic analysis showed cost per liter (CPL) of water of $0.035,$0.028, $0.026 and$0.13 for SSPCM, SSNPCM-1, 2 and 3 respectively. Considering the advantages in productivity and CPL, SSNPCM-2 can be recommended as the best solar still compared to SSPCM, SSNPCM-1 and 3, providing clean water at less than half the cost of bottled water in India

Nanoparticles Enhanced Phase Change Material (NPCM) as Heat Storage in Solar Still Application for Productivity Enhancement

Whereas other researchers used various active and passive techniques to improve the productivity of solar still, this paper uses nanoparticles impregnated in phase change material (NPCM) for productivity enhancement. The solar still is fabricated individually with phase change material (PCM) and NPCM and analyzed both experimentally and theoretically. It is found that the solar still with PCM yielded 1.96 kg/0.5m2 whereas the solar still with NPCM yielded 2.64 kg/0.5m2. There was 35% improvement in productivity observed in solar still with NPCM as against solar still with PCM. The experimental results were validated with the predicted results and the discrepancy was found to be ±10%. Hence it is concluded that NPCM has better potential than PCM for solar still application

Techno-economic analysis of solar stills using integrated fuzzy analytical hierarchy process and data envelopment analysis

Desalination using solar stills is an ancient economic method for water desalination. Over the years, research and development in the area of solar still has resulted in increased distillate yield by means of integration of PCM (phase change material), photo-voltaic thermal (PVT), etc with the still. Nano-PCM is an upcoming technology which modifies the thermal performance of PCM. The aim of this research is to analyze the efficiency of 20 solar stills including nano-PCM based solar stills considering various input and output criteria using integrated fuzzy analytical hierarchy process (AHP) and data envelopment analysis (DEA). The efficiency derived here is relative with regard to the parameters and stills considered in this study. The result infers that, even though the productivity of stepped solar still with sun tracking system was high, but when techno-economic aspects were considered it is not among the top solar stills. The analysis indicated pyramid type solar still, single slope solar still with PVT, solar still with NPCM (paraffin + copper oxide), solar still with NPCM (paraffin + titanium dioxide) and solar still with PCM (paraffin) occupies the top five positions with relative efficiency of 100, 100, 88.47, 88.46 and 76.93% respectively

Annual Thermodynamic Analysis of Solar Power with Steam Injection Gas Turbine (STIG) Cycle for Indian Conditions

AbstractSolar thermal energy is now being widely utilized to meet the world's energy demand due to its huge potential. Power generation from solar is varying and high cost of solar thermal energy systems that makes sense only in regions with high solar insolation. In order to overcome these practical issues, low cost solar hybrid steam injection gas turbine (STIG) cycle is adapted. Both gas turbine exhaust stream and solar heat are used for steam generation, and then it is injected into the combustor. The steam injection reduces NOX and CO2 emission in addition to increased power output and plant efficiency compared to the simple cycle. It offers a path for high conversion efficiency without the requirement of operating at high temperature and high pressure in the solar components. The objective of the proposed work is to investigate a conversion method for solar radiation that offers potentially high conversion efficiency and for increased competitiveness against fossil fuels. The annual performance of the cycle for sites in India with local climatic conditions such as ambient temperature, relative humidity and availability of direct normal irradiance to the solar concentrators under two modes of constant and variable power is presented in this paper. The results reveal that the solar to electricity efficiency of solar hybrid STIG plant with a simple Parabolic Trough Collector (PTC) is similar to existing solar thermal technologies and higher solar share is obtained. The study also reveals that the annual CO2 emission is similar to combined cycle plants and lower than gas turbine technologies

The post-lunch effect of regular and decaffeinated coffee on psychomotor performance: a randomized double-blind cross-over study

Background: This study aimed to compare the effect of regular coffee and decaffeinated coffee on psychomotor performance in healthy volunteers during post-lunch period.Methods: In this randomized double-blind cross-over study, adult healthy volunteers were given hot coffee (3 g each of regular or decaffeinated coffee) during post-lunch period. Psychomotor functions (critical flicker-fusion frequency (CFF), choice reaction time (CRT) and error count in hand-steadiness test (HST)), blood pressure and heart rate were measured pre-lunch, pre-coffee (1-hour post-lunch) and 1-hour post-coffee consumption. Subjective ratings of sleepiness and mood were also assessed during post-lunch sessions.Results: The mean age of the participants (n=16) was 27.4±2.7 years with a male: female ratio of 7:9. There was no significant deterioration in psychomotor performance post-lunch when compared to pre-lunch on both the days. The mean CFF, CRT, errors committed in HST and cardiovascular parameters did not differ significantly between regular coffee and decaffeinated groups during post-lunch sessions. There was no significant difference in values of cardiovascular parameters as well as subjective ratings of sleep and mood between two groups.Conclusions: In healthy adult individuals’ consumption of both regular coffee and decaffeinated coffee during the post-lunch period did not affect psychomotor performance

Unique Locomotive Wheelchair Robot Mechanism using Gesture and Android

Wheelchairs are used by the people who cannot walk due to physical illness, injury or other disability. Elderly peoples are unable to walk, we need to take care of these peoples every days .so, elderly people to maneuver a mechanical wheelchair, which many of them normally use for locomotion. Hence there is a need for designing a wheelchair that is intelligent and provides easy transportation for the physically challenged peoples and elderly peoples. In this context, an attempt has been made to propose a thought controlled wheelchair, which uses the captured signals from the user’s action and processes it to control the wheelchair. The signals which are captured and translated into movement commands by the microcontroller which in turn move the wheelchair

Follower Emotional Intelligence: A Mediator between Transformational Leadership and Follower Outcomes

Purpose:The purpose of this paper is to understand the impact of transformational leadership on Follower EI and examine the potential mediation role played by follower emotional intelligence in the relationship between transformational leadership and follower outcomes (i.e. growth satisfaction in the job & job stress). Design:Data were obtained through survey using questionnaire collected from 908 employees who worked across six different sectors, i.e. manufacturing, IT, health care, hospitality, educational and public services in southern India. The mediation model proposed in this study was tested using structural equation modelling and bootstrapping method. Findings :The relationship between TL and Follower EI was significant. Follower emotional intelligence (EI) was found to partially mediate the relationship between transformational leadership and followers' growth satisfaction in job. Contrary to expectations, the follower EI did not significantly predict job stress in this study and hence the follower EI did not mediate in the proposed model. However, follower EI and growth satisfaction in the job jointly mediated the relationship between transformational leadership and follower job stress fully. Implications :This study established a partial and joint mediation of follower EI on the relationship between transformational leadership and follower outcomes. Basing on these findings, this study highlights the need for the practitioners to better understand the importance of emotional intelligence training for the leaders in the organisations for obtaining better outcomes in the followers. Originality/Value:This study is among the first to examine the impact of TL on follower EI and the potential mediation of follower emotional intelligence between transformational leadership and follower outcomes. From a theoretical perspective, this study is one step closer to fully understand the intervening process between transformational leadership and follower outcomes

Association of Long-Term Exposure to Fine Particulate Matter and Cardio-Metabolic Diseases in Low- and Middle-Income Countries: A Systematic Review.

: Background: Numerous epidemiological studies indicated high levels of particulate matter less than2.5 μm diameter (PM2.5) as a major cardiovascular risk factor. Most of the studies have been conducted in high-income countries (HICs), where average levels of PM2.5 are far less compared to low- and middle- income countries (LMICs), and their socio-economic profile, disease burden, and PM speciation/composition are very different. We systematically reviewed the association of long-term exposure to PM2.5 and cardio-metabolic diseases (CMDs) in LMICs. METHODS: Multiple databases were searched for English articles with date limits until March 2018. We included studies investigating the association of long-term exposure to PM2.5 (defined as an annual average/average measure for 3 more days of PM2.5 exposure) and CMDs, such as hospital admissions, prevalence, and deaths due to CMDs, conducted in LMICs as defined by World Bank. We excluded studies which employed exposure proxy measures, studies among specific occupational groups, and specific episodes of air pollution. RESULTS: A total of 5567 unique articles were identified, of which only 17 articles were included for final review, and these studies were from Brazil, Bulgaria, China, India, and Mexico. Outcome assessed were hypertension, type 2 diabetes mellitus and insulin resistance, and cardiovascular disease (CVD)-related emergency room visits/admissions, death, and mortality. Largely a positive association between exposure to PM2.5 and CMDs was found, and CVD mortality with effect estimates ranging from 0.24% to 6.11% increased per 10 μg/m3 in PM2.5. CVD-related hospitalizations and emergency room visits increased by 0.3% to 19.6%. Risk factors like hypertension had an odds ratio of 1.14, and type 2 diabetes mellitus had an odds ratio ranging from 1.14-1.32. Diversity of exposure assessment and health outcomes limited the ability to perform a meta-analysis. CONCLUSION: Limited evidence on the association of long-term exposure to PM2.5 and CMDs in the LMICs context warrants cohort studies to establish the association