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The moisture resistance of dense- and gap-graded bituminous mixes prepared with the replacement of virgin aggregates and fresh bitumen with reclaimed asphalt pavement (RAP) was evaluated using indirect tensile strength (ITS) and resilient modulus ( Mr). The mechanistic analysis was performed to estimate the effect of moisture resistance on the fatigue performance of thin and thick pavement sections designed with dense- and gap-graded bituminous mixes. The ITS ratio and Mr ratio results indicate that the resilient modulus ratio is more sensitive to moisture damage in bituminous mixes than the ITS ratio. In addition, the results of the fatigue life ratio indicated that the gap-graded mix prepared with different RAP content has better resistance to moisture-related cracking in thick pavement sections than the dense-graded mix. However, the effectiveness of gap-graded and dense-graded mixes prepared with different RAP content on moisture-related cracking depended on the subgrade strength for thin pavement sections.

Concentrated solar power is the technology involving reflectors which reflects the solar radiation and concentrates the radiations onto a receiver which absorbs the solar radiation and rises the temperature of the fluid flowing through it and the fluid is further used for process heating or power generation. Solar parabolic trough is the most established technology among the concentrated solar power technologies. For the optimization of the technology it is important to optimize the parabolic trough collectors from structural point of view as even gravity load is observed to cause a substantial effect on the shape of the reflector. Shape accuracy of the reflector is measured in terms of slope deviation. The slope deviation induced due to gravity and wind loads causes a change in optical and thermal efficiencies. The paper presents the study on pressure distribution at the surface of parabolic trough collector under different wind velocity, angle of attack of wind and orientation of the trough. Further, the pressure values over the trough surface are used to estimate the shape errors for the surface of the trough.

The present study evaluates the existing district-wise cropping system of Kharif and Rabi season prevailing in Telangana State of India. In kharif season, it was observed that all districts of the states are water surplus and whereas during Rabi season all districts become water deficit. In order to enhance the agricultural production and agricultural based rural economy, alternate cropping system weresuggested. Due consideration was given to the existing water resource and farming practices prevailing in the respective district. Re-appropriation of area under various crops was suggested for two scenarios namely, ‘A’ and ‘B’, aimed for reduction in crop water requirement by 10 % and 20 %, respectively. In scenario ‘A’, it was suggested to reduce the area under transplanted paddy and ground nut by half and 40% respectively,in kharif season and substantial enhancement in the area under redgram. For rabi season the area under transplanted paddy could be reduced to half for scope to double the area under oilseed. The scenario ‘B’ however is feasible in 3 districts, suggests restricting the area under groundnut to comprehensive increase in pulse area. For rabi in scenario ‘B’, it is recommended to further reduce the area under oilseed, paddy and other crops allows more crop diversity including millets, sorghum and caster. The economic analysis suggested that the alternate scenario has the potential to significantly improve the benefit cost ratio apart from enhancement in water productivity.

The thermal energy storage system is a pivotal system for solar thermal plants for improving reliability. The stability in the thermocline is more significant to clarify and improve the performance of thermal energy storage tank which legitimately shows the quality of the thermocline. In this stability analysis investigation, the modern engineering energy storage material concrete was used as a filler material for high-temperature thermal energy storage applications as a result of the intrinsic properties. A comprehensive laminar and k-e turbulent flow energy transport model accounts for the heat transfer fluid and filler material with adiabatic and non-adiabatic conditions using LTNE (Local Thermal Non-Equilibrium model). The axial, radial, and diagonal temperature differences were identified which was used to calculate the stability of the thermocline. A thermal energy storage tank size of 1 m height and 0.250 m diameter with a 0.030 m size of filler material packed with an average porosity of 0.3 for the storage capacity of 150 kWh/m3 is used for solar process heating applications considered for the present study. The thermocline stabilities are performed with Reynolds numbers, Re varied from 1 to 3000. It is found that the Re = 1 provides better stability in the axial and radial direction as well as diagonal than other Reynolds number. It is observed that Re = 1 provides superior discharging efficiency for nearly 5.84 hrs which is highly suitable for solar process heating applications and the discharging efficiency consistently drops, when Re increases from 1 to 3000. The wall condition of the tank and velocity of the heat transfer fluid is highly disturbing the thermocline in the radial direction and it creates a ‘spike’ profile in the axial direction. Based on the newly introduced stability scale, the effective length of packing and timing to achieve stability is identified for H/D = 4. From that result, the top and bottom layer of the thermocline tank porosity is also found which is used to decide the porosity of the packed bed distributors. The identified porosity for the top and bottom distributors in the ɛ = 0.3 thermal energy storage tank is less than 0.3 is more suitable for provide the uniform flow in the tank.

Solar energy is one of the emerging technologies and the use of concentrating power technology is increasing in solar power plants. Parabolic trough collector is a concentrating solar power technology that is situated in the open terrain and subjected to wind loads. The structural stability of these devices under such loads determines the ability to accurately concentrate the rays at the absorber tube, which affects the overall optical and thermal efficiencies. A detailed numerical analysis is carried out at different wind loads and design conditions. It is observed that for a change in velocity from 5 m/s to 25 m/s, slope deviations increase from 1.21 mrad to 3.11 mrad at the surface of the reflector exceeding the shape quality of the mirror panels. Higher yaw angles and pitch angles of 60° and 120° are observed to be decisive in the design of collectors. Roof-mounted collectors experience a 40% higher drag force than ground-mounted collectors at a 0° pitch angle. For the Aluminium trough, the slope deviation at the surface of the reflector is higher by 4.62% than glass. The study will be helpful for engineers and scientists in the design of the parabolic trough collectors.

Photovoltaic Thermal (PVT) systems generate hot water and electricity simultaneously. The grade of thermal energy generated by such PVT systems is low, resulting in limited application. To overcome this challenge, the coupling of the PVT system to a secondary flat plate collector (FPC) has been explored in this work. For the system's performance estimation, a 3-D numerical model has been developed for both glazed and unglazed PVT-FPC collector. Based on the numerical model, PVT collectors have been fabricated, and each is then connected in series to a commercially available FPC collector. Experiments conducted on the fabricated PVT-FPC system showed a close match between simulation and experiments. Further, experiments conducted on the unglazed PVT – FPC collector showed a peak outlet water temperature of 60–63 °C at 30 LPH. For the unglazed PVT collector, the peak electrical and thermal efficiency of 16% and 25% is reported respectively, whereas for the FPC collector, the thermal efficiency of 35% is reported. Compared to an individual unglazed PVT collector, 17 °C higher outlet water temperature is reported for the coupled system. Similarly, for the case of glazed PVT-FPC collector, the peak outlet water temperature reported is 65–67 °C at 30 LPH with 14–15 °C higher outlet water temperature.

In this work, a non-imaging low concentrating 2.5X Compound Parabolic Concentrator (CPC) truncated to 1.7X has been explored. CPCs inherently form non-uniform distribution of flux on the PVT module which has been mitigated by the integration of optimized homogenizer referred to as Elongated CPC (ECPC). The study involves detailed optical, thermal, and electrical modeling of the ECPC based Low Concentrating Photovoltaic Thermal (LCPVT) system. Optical simulations provide insight into the flux distribution on the PVT panel surface, which is further coupled with a thermal and electrical model for precise prediction of the performance of the system. These models are validated experimentally with a 315 Wp solar panel integrated with ECPC based LCPVT system. Performance evaluation of the system has shown peak thermal efficiency of ∼40% at ΔT of 16 °C, peak electrical efficiency of 12%, and an overall peak exergy efficiency of 15% at 38 Liters per hour (LPH) flow rate. A comparison of outlet water temperature results obtained from the numerical model and experiments has shown an excellent match with a relative error of 4%. Results also show that the increase in mass flow rate from 22 LPH to 38 LPH improves the electrical efficiency by 3% however a drop in ΔT of 2–3 °C is observed.

The quality and shelf-life of NCS (non-centrifugal sugar) mainly depend on the moisture content present in it. NCS formed by the current practice of open sun drying contains moisture substantially greater than the acceptable level of 3%. This paper presents the work undertaken to design a tunnel dryer to achieve the required moisture content of granular NCS for various load conditions. An experimental investigation was conducted on a laboratory-scale dryer to achieve the required moisture content for various loads. This experimental data was compared with the output of two drying models and a validated one that could be used to design an industrial-scale dryer. For various load conditions on each tray and dryer exit temperature, nine different cases were determined. The number of trucks, drying time, and energy requirements were computed using the validated theoretical model. A tunnel dryer with a length, height and width of 18, 1.2 and 1 m respectively and 18 trucks with 24 trays on each truck is shown to be dry 1 tone of NCS based on the minimum energy requirement of 176.49 MJ, and a drying time of 68 min.

Photoelectrochemical (PEC) water splitting by direct solar irradiation has been considered as a route to produce solar fuel, but the technique is impeded by limitation of the photocathode materials...

In the present work, two dimensional (2D) and three dimensional (3D) semi-analytical models are proposed to estimate an effective thermal conductivity of two-phase building materials with spherical inclusions. The proposed semi-analytical approach is based on the formulation and the solution of a boundary value problem. Further, the solution is coupled with Maxwell’s methodology to estimate effective thermal conductivity. The 2D model is simple and limited in scope while the 3D model is widely applicable and is based on a multipole expansion method. The 3D model incorporates secondary parameters like size distribution, variation in thermal conductivity among the inclusions, particle interaction and statistical spatial distribution. For the 3D model, spherical representative unit cells (SRUC) based on the face-centred cubic arrangement and trimmed spheres at the boundary are proposed. Effective thermal conductivity estimated by the proposed models is compared and validated with experimental results from the literature. The 2D model predicts the thermal conductivity of conventional concrete with reasonable accuracy where the relative error is less than ±12%. The 3D model predicts accurate results for foam concrete with a relative error of less than ±15%. Predictions of thermal conductivity of lightweight concrete by the 3D model are also in good agreement with experimental results. Finally, the comparison of proposed models with models from literature has shown that the incorporation of particle interaction has improved the accuracy of the solution. Thus, the flexibility with SRUC and incorporation of particle interactions make this 3D model widely applicable for building materials with spherical inclusions.

In this paper, a two-stage square parabolic concentrating photovoltaic (CPV) receiver dish with an overall geometric concentration ratio of 500 suns is designed to provide a uniform intensity distribution on high-efficiency triple-junction solar CPV cell module. The system comprises of a square parabolic dish with an aperture area of 9 m2 as a primary concentrator and an array of the compound parabolic concentrator integrated optical homogenizer of 0.27 × 0.27 m2 as a secondary concentrator in tandem with the dish. The CPV module consists of an array of 12 × 12 triple junction CPV cells with each cell connected in parallel or series combination and integrated CPC homogenizer dedicated to each cell. The homogenizer length is selected based on the peak to average ratio of concentrated flux with the aim to maximize the optical and electrical performance of the CPV system. Monte Carlo ray-tracing model is used to predict the flux distribution. The predicted solar flux distribution on individual CPV cells are used as input to determine the electrical performances of the CPV module with three different cell interconnections. For optimized homogenizer length of 0.005 m and receiver height of 3.7 m, the maximum optical and CPV module efficiencies are obtained as 68.30% and 32.03% respectively. A year-round electrical power output of developed CPV system is 2.19 MWh which is up to 33.54% higher as compared to conventional CPV system. The proposed novel geometric design could accommodate the bypass diode for each cell, effectively reducing the current mismatch effects.

In the current investigation, viable solar desalting sites in coastal India are identified by detailed thermodynamic and enviro-economic analyses. Mathematical model developed for thermodynamic performance assessment is validated using experiments conducted in inclined solar distillation unit under the climatic condition of Chennai (13.08°N, 80.27°E). Distillation unit produced high quality condensate even from highly saline (40,600 to 60,656 mg/L salinity) feed water. Availability analysis indicated the magnitude of improvement potential, availability destruction, losses and ways for further improvement. Maximum condensate yield, energy and availability efficiency of distillation unit is around 7.09 L/d, 53.45% and 5.39%, respectively for Nellore (one of the east coast locations). Condensate production cost of 18.16 to 32.78 USD/kL and desired availability output of 1.80 to 3.38 kWh/USD invested are observed for the distillation unit at 5.0% interest rate. Maximum yearly average life cycle conversion efficiency, net carbon-dioxide, sulphur-dioxide and nitrous oxide emission alleviated by the unit is around 39.19%, 25.83 tons, 185.73 kg and 75.86 kg, respectively. Viability assessment indicated positive signs for deployment of solar distillation units in 14 locations of coastal India. The proposed solar distillation unit requires lower evaporation area compared to other passive solar distillation units installed in India for the same production capacity.

Parabolic Trough Collector (PTC) system for process heat application with medium temperature range is decisive for the tremendous availability of solar energy. In the present work, the prototype of 5.77 m aperture and 80.2 rim angle of PTC system with Evacuated Receiver (ER) and Non-Evacuated Receiver (NER) were designed, fabricated, installed and evaluated for the performances in the IIT Madras, Chennai, India. Experiments were carried out to analyze the optical and thermal performances of the receiver based on the ASHRAE standards 93–2010. The performance parameters such as peak optical efficiency, incident angle modifier, time constant (both heating and cooling), heat loss and thermal efficiency for ER and NER were measured. This article also present the methods for measuring the heat losses of both receivers under laboratory test conditions and on-field experiments based on energy balance of the receiver. The peak optical efficiency of ER and NER is close to 72% and 68% respectively at minimum heat loss condition. The maximum thermal efficiency of the ER and NER of PTC systems are 66% and 64% for the mass flow rate of 0.12 kg/s and 64.3% and 62.1% for the mass flow rate of 0.06 kg/s. Performance studies of receivers were carried out to analyze the effects of the inlet and outlet temperature of HTF, instantaneous thermal efficiency and weather parameters (DNI and ambient temperature) on both sunny and cloudy day. The maximum temperature achieved by the HTF in ER and NER is 155 C and 137 C for the corresponding solar incident radiation 756 W/m2 and 691 W/m2 respectively.

For a CPV system, prediction of focal flux distribution at the receiver area will give insight to more effective, energy efficient designs and to estimate power output. An experimental method for in-situ prediction of heat flux distribution profile using inverse heat transfer technique on a flat plate receiver for a CPV square parabolic dish is presented. An IR camera is used to measure the temperature of the concentrated receiver surface. The receiver domain is discretised into several heat flux elements and heat flux values for each grid is then estimated using the measured infrared (IR) pixel temperature and ordinary least square. A 3-D steady state heat conduction equation with convection and radiation heat loss boundary is regarded as the forward problem. The simulated temperatures generated from the solution of forward problem using the predicted heat flux distribution and measured temperature distribution are in close agreement. For validation purpose, the concentrated heat flux is also measured using Gardon and Schmidt-Boelter heat flux sensor. The peak predicted focal heat flux on the receiver is found to be 37.41 kW/m2 whereas the heat flux value measured by the flux sensor is 39.15 kW/m2 within the deviation of 4.4%.

The intermittent nature of renewable sources, such as solar and wind, leads to the need for a hybrid renewable energy system (HRES) that can provide uninterrupted and reliable energy to a remote and off-grid location with the use of a biogas generator and battery. In the present study, conventional PV panels have been integrated with phase change material (PCM) for power enhancement. In addition, various configurations (i. PV-Wind-Battery system, ii. PV-PCM-Wind-Battery, iii. PV-Wind-Biogas-Battery and iv. PV-PCM-Wind-Biogas-Battery) have been compared for the hot and humid climatic location of Chennai, India. Optimization has been carried out to minimize the cost of energy and the net present cost has also been computed. It has been found that the integration of PCM with the PV-Wind-Biogas-Battery-based off-grid system results in savings of USD 0.22 million in terms of net present cost and reduces the cost of energy from USD 0.099/kWh to USD 0.094/kWh. Similarly, for another off-grid HRES configuration of PV-Wind-Battery, the integration of PCM results in savings of USD 0.17 million, and reduces the cost of energy from USD 0.12/kWh to USD 0.105/kWh.

This article deals with estimation of spatially distributed thermal properties of two-dimensional heterogeneous media from the solution of inverse heat conduction problem. The experimental procedur...

Here, performance of 11 kW solar-powered lithium bromide water absorption chillers in cogeneration mode is investigated. A 40 m 2 solar parabolic dish of 19 kW th capacity is used for both processes heating and cooling. Extensive thermodynamic design and analysis are carried out, and the results obtained are validated. Parabolic dish and cavity receiver are sized for Chennai (13°N, 80.18°E), India. In the present analysis, a new performance parameter COP WE is introduced by replacing the thermal input component in the calculation of COP, by an equivalent amount of high-grade energy. Both physical and chemical exergy at all state points of the chiller are estimated and found that total irreversibility is about 2.37 kW in desorber followed by absorber which is 0.41 kW. The developed model estimates solution concentration at the exit of solution expansion valve (SEV) that is important since it affects absorption of refrigerant in the absorber.

This paper presents a detailed description and experimental validation of a modified collocated unit cell model for the estimation of effective thermal conductivity of packed beds. The effect of primary and secondary parameters influencing the effective thermal conductivity viz. conductivity ratio (α) and concentration (ν) of the spherical particles (fraction of total volume occupied by the particles) of the packed bed, inter-particle gap, thermal contact conductance between the surfaces in contact, temperature, pressure and Knudsen number respectively are investigated in detail. Analytical expressions for effective thermal conductivity are derived for spatially periodic 2D square cylinder and in-line touching geometries based on the unit cell based thermal resistance approach. Using the developed model, the effective thermal conductivity of various packed materials in the conductivity ratio (ks/kf) range between 1–1000 and concentration (ν) 0 to 1 are predicted for varied temperature and pressure regimes. Predictions obtained from the developed model are compared against existing models available in literature in the pressure range 10−2 to 103 kPa at constant temperature. Furthermore, effective thermal conductivities of packed beds comprising of glass and ceramic beads are predicted using the developed model and compared with measured values obtained using the standard square guarded hot plate (SGHP) apparatus in the temperature range of 323–673 K. Both values are found to agree within ±12.24% and ±14.54% for glass and ceramic beads respectively.

In this article, thermal analysis of Solar volumetric receiver used in concentrated solar thermal power systems is studied. A cylindrical volumetric receiver used in the parabolic dish collector and solar power tower is analyzed using a finite element method based tool COMSOL multiphysics software. A non uniform Gaussian distribution based heat influx is applied at the receiver to mimic the actual conditions. The steady state operation of the receiver is studied for various porosity and thermal conductivity of the solid phase. Different parameters of Gaussian distributions corresponding to different flux profile conditions are studied. The Gaussian profile heat flux amounting to 1 MW/m2 results in the Gaussian like temperature distribution of the fluid phase near the receiver exit region. Higher thermal conductivity of 200 W/(m K) coupled with the high porosity of 0.7 leads to the better operational efficiency of the receiver. Lower porosity results in higher peak temperature in the fluid phase and higher thermal conductivity laterally spreads the temperature across the receiver. The intermittent solar flux condition is realized through transient response study of flux conditions. The temperature gain rate in transient case is found to be approximately 24 K/s while the temperature drop is around 29 K/s.

Photovoltaic (PV) panels convert a portion of the incident solar radiation into electrical energy and the remaining energy (>70 %) is mostly converted into thermal energy. This thermal energy is trapped within the panel which, in turn, increases the panel temperature and deteriorates the power output as well as electrical efficiency. To obtain high-efficiency solar photovoltaics, effective thermal management systems is of utmost. This article presents a comprehensive review that explores recent research related to thermal management solutions as applied to photovoltaic technology. The study aims at presenting a wide range of proposed solutions and alternatives in terms of design approaches and concepts, operational methods and other techniques for performance enhancement, with commentary on their associated challenges and opportunities. Both active and passive thermal management solutions are presented, which are classified and discussed in detail, along with results from a breadth of experimental efforts into photovoltaic panel performance improvements. Approaches relying on radiative, as well as convective heat transfer principles using air, water, heat pipes, phase change materials and/or nanoparticle suspensions (nanofluids) as heat-exchange media, are discussed while including summaries of their unique features, advantages, disadvantages and possible applications. In particular, hybrid photovoltaic-thermal (PV-T) collectors that use a coolant to capture waste heat from the photovoltaic panels in order to deliver an additional useful thermal output are also reviewed, and it is noted that this technology has a promising potential in terms of delivering high-efficiency solar energy conversion. The article can act as a guide to the research community, developers, manufacturers, industrialists and policymakers in the design, manufacture, application and possible promotion of high-performance photovoltaic-based technologies and systems.

In this work, a non-imaging low concentrating 3X Compound Parabolic Concentrator (CPC) truncated to 1.7X has been explored. Since, CPC is a linear concentrator, the linear image formed on the absorber results in non-uniform distribution of flux. To reduce the non-uniformity in flux distribution, an optimized homogenizer has been integrated with the CPC, referred to as Elongated CPC (ECPC). Thereafter, numerical model has been developed for predicting the thermal performance of the ECPC integrated with homogenizer using actual meteorological data (wind speed and ambient temperature). Finally, the system is fabricated, and its performance is evaluated under real-world conditions. Experimental results showed a peak thermal efficiency of ~35% and peak electrical efficiency of 10%. The outlet water temperature obtained from simulations and experiments show a good match with variation of ±2 ℃.

Sustainable desalination can be achieved by adopting renewable energy-based low-cost and low-impact desalting techniques. In this investigation, capability of inclined felt sheet solar distiller in desalting seawater is assessed by evaluating its performance, distillate water quality, economics, and environmental impacts. The distiller with 1.18-m2 aperture area produced around 4.60 L/day of distillate for a cumulative incident solar radiation intensity of about 20.52 MJ/m2 day. Its pollutant removal efficiency is very much superior to other available solar stills reported in literatures. Thermal model developed for estimating distiller’s performance is able to predict its productivity with reasonable accuracy (only 8.0% deviation from experimental values) and was used for estimating distiller’s performance in various seashore locations in India with varying clear days (191 to 246). Yearly mean distillate production and thermal and exergy efficiencies of the proposed distiller range between 3.60 to 4.50 L/day, 36.45 to 42.39%, and 2.85 to 3.65%, respectively, in east seashore locations of India. Moreover, 18.46 tons of CO2, 132.72 kg of SO2, and 54.20 kg of NO emission can be mitigated by adopting the distiller for potable water production. Distillate production cost of inclined felt sheet solar distiller is in the range of 1.15 to 2.29 INR/L and highly depends on the interest rate at which the distiller is financed. Generation of reasonable quantity of high-quality potable water at low cost with huge environmental benefits makes proposed inclined felt sheet solar distiller a suitable option for quenching thirst in coastal and remote locations.

The quality and shelf-life of NCS (Non-centrifugal sugar) mainly depend on the moisture content present in it. NCS formed by the current practice of open sun drying contains moisture substantially greater than the acceptable level of 3%. This paper presents the work taken up to design a tunnel dryer to attain require moisture content in granular NCS for various load conditions. Initially, an experimental investigation had been carried out on a laboratory scale dryer to achieve required moisture content (< 3%) for various load conditions. This experimental data was used for validating two drying models and found that one of the models is best suitable for designing an industrial-scale dryer. For various load conditions on each tray and dryer exit temperature, nine different cases were arrived at. The number of trucks, trays, drying time and energy requirements were computed using the suitable theoretical model. Tunnel dryer with a length of 18 m, a height of 1.2 m, a width of 1 m, number of trucks of 18 and 24 number of trays on each truck was found to be the suitable dryer to dry 1 tone of NCS based on the minimum energy requirement of 176.49 MJ, and a minimum drying time of 68 minutes.

The accumulation of soiling on photovoltaic (PV) modules affects PV systems worldwide. Soiling consists of mineral dust, soot particles, aerosols, pollen, fungi and/or other contaminants that deposit on the surface of PV modules. Soiling absorbs, scatters, and reflects a fraction of the incoming sunlight, reducing the intensity that reaches the active part of the solar cell. Here, we report on the comparison of naturally accumulated soiling on coupons of PV glass soiled at seven locations worldwide. The spectral hemispherical transmittance was measured. It was found that natural soiling disproportionately impacts the blue and ultraviolet (UV) portions of the spectrum compared to the visible and infrared (IR). Also, the general shape of the transmittance spectra was similar at all the studied sites and could adequately be described by a modified form of the Ångström turbidity equation. In addition, the distribution of particles sizes was found to follow the IEST-STD-CC 1246E cleanliness standard. The fractional coverage of the glass surface by particles could be determined directly or indirectly and, as expected, has a linear correlation with the transmittance. It thus becomes feasible to estimate the optical consequences of the soiling of PV modules from the particle size distribution and the cleanliness value.