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• Heat Transfer anaylsis for Scheffler dish collector was conducted to identify areas from where heat losses are occurring. • Efficiency of cooking pots was analysed to estimate overall performance of the system. • Recommendations for operations and maintenance are provided based on thermal analysis. The escalation of energy demand in both developed and developing countries has prompted people to search and utilize clean and sustainable energy resources. Omshanti Retreat Centre (ORC) situated in Gurugram, Haryana, India utilizes solar energy to meet most of its energy demand. It has installed Scheffler dish type solar thermal cooking system having a capacity to cook 6000 meals per day in the year 2001 and is being utilized to cook food three times a day for approximately 200 days per year. The present research was conducted to study the performance of the solar thermal cooking system both experimentally and analytically; identify areas from where heat losses are occurring in the system and suggest steps that should be taken for improvement of overall system performance. Experiments were performed for seven consecutive days at ORC during summer. The system consists of twenty eight collectors arranged in such a way that a pair of Scheffler reflectors of 10 m2 aperture area concentrates solar radiation on one absorber. Thermal efficiency of 70–80% was obtained for the collectors experimentally for an average direct normal irradiance of 800 W/m2. The overall system efficiency was estimated to be 25% which suggests significant losses in the overall process. The research identified the areas which act as sources for heat losses from the system. [ABSTRACT FROM AUTHOR]

• Thermo-enviro-economic modeling of novel passive multi chamber vertical diffusion still. • East-west manually tracked unit is superior than sole south oriented unit. • Yield, exergy efficiency and performance ratio of about 11.13 kg/m2-d, 23.15% and 2.0. • Mitigation of 67.9 tons of CO 2 emission in 20 Yr life time. • Low distillate production cost of about 0.90 INR/L. Multiple-effect solar distillation units are more promising in fulfilling the potable water demands of population in rural and remote areas. Among multiple-effect distillation units, diffusion type is more compact, portable and high productive. In the present study, a novel type of passive multi-chamber vertical solar diffusion still is proposed and the impact of various system and climatic parameters on its performance and economics has been evaluated and presented. Triple chamber vertical diffusion still is found economical and it has a performance ratio and exergy efficiency of around two and 23.15%, respectively. Exposing the aperture of distillation unit to wind flow revealed a negative impact on its yield but the reverse is observed when the last condensing unit is exposed to the wind. Lower distillation and exergy efficiency is observed for 1st diffusion chamber compared to other chambers due to increased heat loss from absorber plate. Evaporative heat transfer ratio of diffusion chambers increased from 0.81 to 0.97 with increase in solar radiation intensity from 100 to 1000 W/m2. The optimized unit is simulated under the climatic conditions of various locations of Tamil Nadu state of India under sole south orientation and east-west manually tracked mode. Annual average yield of 11.13 kg/m2d is obtained with an exergy efficiency of 13.85% for east-west manually tracked unit. Distillate production cost and financial payback time of the unit are estimated to be 900.00 INR/kL and 0.63 Year, respectively. The proposed unit also has a capability to mitigate 67.93 tons (average) of CO 2 emission during its 20 Year lifetime. Better yield, low distillate production cost and huge environmental benefits justify the capability of proposed triple chamber passive vertical solar diffusion still for sustainable desalination in under privileged/developing countries. [ABSTRACT FROM AUTHOR]

• Single and two-phase flow model is developed for thermal performance of ETC. • The investigation is based on average data for varying seasonal conditions. • Overview of the applicability of solar collector for the location of Silchar. • Outlet temperature, overall heat loss coefficient etc are analysed. • Low mass flow rate favours the formation of vapor in the solar collector. The standard condition for evaluation of solar heating system considers solar insolation of 1000 W/m2 which provides a good estimation of the performance of the system, but not able to predict a realistic situation due to the fluctuating behaviour of solar insolation. Therefore, an attempt is made to simulate a practical condition for a solar heating system by varying solar radiation throughout the day as well as months of a year. Hourly solar insolation data are collected from web-based resource PVGIS for the region of Silchar, a north-eastern location in India. The results revealed that the temperature profile of the working fluid in the Evacuated Tube Collector is non-linear and the rise in temperature is more in the months of November-March than April-October. The outlet temperature is highest for the month of February and lowest in June which signifies that the system can be practically applicable in this region for water heating purpose, as it produces a higher temperature in winter days. Also, the daily analysis shows the efficiency of the system is very low during the morning and evening hours. Moreover, there is a possibility of obtaining a two-phase flow in the outer pipe under certain circumstances and this production of vapour is accompanied by a reduction in efficiency. The analysis shows that with radiation being fixed, inlet temperature and mass flow rate are the most dominant factors for two-phase flow. Present model also suggests an optimum mass flow rate beyond which the flow becomes two-phase and not desirable. [ABSTRACT FROM AUTHOR]