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Abstract Exergy analysis is very helpful for reducing irreversibility and rising the efficiency of solar collectors. The major objective of the present study is to organize a review on exergy analysis of different parabolic solar collectors. The effects of various flows and geometrical parameters of parabolic thermal collectors on the exergy efficiency were presented and discussed. In addition, comparative study was carried out to select the best solar thermal system for maximum exergy efficiency with minimal thermal losses. This study indicated that the hybrid nanofluids enhanced the exergy efficiency significantly as compared to without hybrid nanofluids. Passive techniques comprising twisted tape inserts, fins and insertion of swirl devices in the stream for changing the stream patterns causes to interrupt the thermal boundary layer and accordingly high exergy efficiency. This review would also throw light on the scope for further research and recommendation for improvement in the existing solar thermal collectors. Finally, this work will be beneficial for the scholars working on exergy analyses of solar parabolic collectors.

Abstract Seasonal solar thermal energy storage (SSTES) has been investigated widely to solve the mismatch between majority solar thermal energy in summer and majority heating demand in winter. To study the feasibility of SSTES in domestic dwellings in the UK, eight representative cities including Edinburgh, Newcastle, Belfast, Manchester, Birmingham, Cardiff, London and Plymouth have been selected in the present paper to study and compare the useful solar heat available on dwelling roofs and the heating demand of the dwellings. The heating demands of space and hot water in domestic dwellings with a range of overall heat loss coefficients (50 W/K, 150 W/K and 250 W/K) in different cities were calculated; then the useful heat obtained by the heat transfer fluid (HTF) flowing through tilted flat-plate solar collectors installed on the dwelling roof was calculated with varied HTF inlet temperature (30 °C, 40 °C and 50 °C). By comparing the available useful heat and heating demands, the critical solar collector area and storage capacity to meet 100% solar fraction have been obtained and discussed; the corresponding critical storage volume sizes using different storage technologies, including sensible heat water storage, latent heat storage and various thermochemical sorption cycles using different storage materials were estimated.

Abstract Solar energy is a potential clean source of energy to meet our thermal and electrical energy demands but its penetration is hindered by the factors such as intermittency of solar radiation, lower thermal efficiency, and capital requirement for the solar energy systems. Improving the thermal performance of the solar collectors and effectively collecting the thermal energy from photovoltaic panels can pave the way to promote clean energy utilization. Heat pipe, being a passive energy system with a high heat transfer rate ability, can aid in ameliorating the performance of solar collectors as well as photovoltaic panels. This review study is proposed to discuss the theoretical and experimental aspects of the design and integration of heat pipes with various solar applications including solar thermal, freshwater production, and photovoltaic-thermal systems. In addition, numerical models relevant to heat pipe and solar energy systems are highlighted. An elaborate analysis of various influencing factors on the thermal performance of heat pipe integrated solar energy systems is also presented. The critical observations from experimental aspects are elucidated, and the future scope of heat pipe systems are also substantiated. This review encourages the selection of a particular heat pipe and the heat transfer enhancement method to attain higher energy conversion rate and the productivity corresponding to various solar energy systems.

Abstract The depletion of fossil fuel and their impact on the environment due to continual usage for our ever-increasing power needs has forced us to look pro-actively towards other renewable forms of clean energy like wind, solar, ocean energy, etc. Amongst all renewable sources of energy, solar energy is abundantly available throughout the world and can meet the energy needs of our planet if appropriately harnessed. Solar thermal collectors are used to collect solar thermal energy, and then it is transferred to the fluid. The fluid may be air, water, oil, etc. depending on the application. Many researchers are working towards performance enhancement of solar thermal collectors. This article concentrates on solar air collectors and different types of modifications made in the recent past to improve its efficiency. This study is an attempt to summarize and present solar air heaters and various modifications for performance enhancement. The effect of modifications on the Nusselt number, friction factor, and thermohydraulic performance of the solar thermal collector is reported. The present article also discusses the effect of impingement of air on the device thermal efficiency and the geometric modifications. This paper will enable researchers working in this field to get a summary of important work done related to solar thermal collectors.

Abstract Conventional jaggery making process utilizes the bagasse for boiling of sugar cane juice which releases pollutants into the atmosphere and high particulate matter from these emissions causes air pollution. In this article, solar powered jaggery industry with freeze pre-concentration is proposed with conventional and modified heating pans. The system performance, environmental impacts and economic feasibility were assessed by carrying out 4E (Energy-Exergy-Environment-Economic) analyses using the developed mathematical model. These systems were designed to produce 300 kg of jaggery per day when operated for 7.5 h in 3 batches with average solar direct normal irradation of 662 W/m2 and 343 °C. These systems are integrated with auxiliary heating for uninterrupted production in the absence of sunlight. These systems can mitigate nearly 2015.95 to 3062.15 tons of CO2 emission during its 25 years of lifespan under 300 clear days of operation each year. Jaggery produced by this technique is rich in its colour and completely safe for human consumption as no artificial clarificants are used. Amount invested in these systems can be recovered in a span of 12.03 to 13.45 years for jaggery selling price of USD.0.514/kg or INR.36/kg.

Abstract A fast scheme for estimation of the instantaneous direct solar irradiance (DSI) at the Earth’s surface is developed based on detailed radiative transfer calculations for the full range of atmospheric conditions. The parameterisation is divided into the components for clear sky and overcast conditions. For the clear sky condition, the effects of absorption due to water vapour, carbon dioxide and ozone on the DSI are explicitly treated. The effects of Rayleigh scattering, aerosols are also treated on a physical basis. Based on the clear sky results, the transmittances due to effects of clouds are determined for both liquid and ice clouds. The results are parameterised in terms of cloud visible optical depth. The input variables required for determination of DSI include precipitable water, column ozone amount, CO2 mixing ratio, aerosol optical depth, cloud visible optical depth, surface pressure and solar zenith angle. These variables are all available in numerical weather prediction (NWP) forecast models or can be obtained from satellite observations. Therefore, the scheme can be used to determine the DSI using NWP model products or satellite data. The scheme has been tested using the observations obtained at three stations of the US Department of Energy Atmospheric Radiation Measurements (ARM) program. The relative mean bias differences under clear-sky and all-sky conditions are better than 3.2% and 5.1%, respectively. The correlation coefficients between modelled results and observations are all greater than 0.99. The sampling errors of DSI due to the use of 3-hourly or 1-hourly low frequency in radiation calculations in NWP models are evaluated using the fast scheme and ARM observational data. It is found that these errors can be greater than 800 W m−2 for many cases where sky condition changes from clear to overcast. Application of the current scheme can reduce these errors to less than 100 W m−2.

Abstract A thermal energy storage system (TES) is a key technology to ensure continuous power supply from solar thermal power plants. Choosing the appropriate storage method and the suitable material for energy storage remains a major challenge in research and development in the solar power field. The sensible heat storage in solid media using thermocline system is a significant cost-effective option when compared to liquid storage material in two tank system. An incorporation of this potential concept is the oil/rock thermocline system which is based on the direct contact between natural rocks chosen as filler material and thermal oil as the heat transfer fluid (HTF), and it is used in the Concentrated Solar Power (CSP) plants. The present paper highlights the thermal energy storage potential of six rocks (quartzite, basalt, granite, hornfels, cipolin and marble) proposed as filler material for thermal oil thermocline storage concept. These rocks were chosen according to their abundance in Morocco. Different technical methods were performed in order to assess the rocks properties (physical, chemical and thermal) at temperatures up to 350 °C (temperature operating conditions using linear Fresnel reflectors or parabolic trough). The thermal performances of the studied rocks inside a thermocline storage system were evaluated using a validated numerical model. Based on the experimental investigation two rocks (Quartzite and Cipolin) were identified as the most suitable filler materials to be used in direct contact with the studied HTF (synthetic oil). While, the numerical analysis revealed that Basalt rock has the best thermal performances inside the studied thermocline storage system concept, but it isn’t chemically compatible with synthetic oil. Hence, it can be used advantageously with other heat transfer medium (e.g. Air).

Abstract The aim of this paper is to examine the energy consumption of and determine energy-efficient design strategies for mid-rise and high-rise office buildings in composite climate. For this purpose, a comparative study is performed of six energy-efficient office buildings in composite climate in India. The selected energy-efficient office buildings are situated in the major cities (Delhi, Gurgaon, and Hyderabad) of India with a composite climate. This study investigates the effectiveness of different design strategies for reducing the heating, ventilation, and air-conditioning (HVAC) and lighting loads of the six buildings. The effect of factors such as the building form, envelope configuration, placement of the service core, window-to-wall ratio (WWR), and percentage of air-conditioned space on the HVAC load are analyzed. Similarly, the effect of the plan depth and WWR on the lighting load is also determined. Finally, the findings of the study are used to recommend effective design strategies for high-rise office buildings in composite climate. Moreover, the energy performance data are compared with the national energy consumption benchmarks for composite climate. The comparison indicates the design strategies performed well, that lead to a decrease in the energy consumption of high-rise office buildings in composite climate.