Gravity & wind load analysis and optical study of solar parabolic trough collector with composite facets using optimized modelling approach
In the present work, structural and optical analysis of 23.08 m2 (Aaperture) solar parabolic trough has been done utilizing different composite materials with an optimized modelling approach. The linear parabolic trough collector is subjected to gravity and wind loads and thereby it undergoes surface deformations. Various trough materials are structurally analysed and a hybrid composite is designed. The RMS values of local slope deviations of trough termed as SD value is calculated using Modified Element Approach to observe the behaviour of trough at various tracking positions varying from 0° to 90° orientations. The cases been discussed are trough-alone (stiff) case and full collector (elastic) case under gravity and wind loading conditions with wind speed of 15 m/s. Trough parameters like fibre orientation of laminae, stacking sequence and direction and size of reinforcement conduits are optimized to minimize SD values. Furthermore, the setup is optically studied and the slope deviations are compared for individual models through intercept factors (γ). The comparative study reveals that the solar parabolic trough collector with its facets made of woven jute/glass fibre-reinforced polyester hybrid composite material yields γmax = 0.957 for avg. SD = 1.34 mrad in stiff case and γmax = 0.955 for avg. SD = 1.349 mrad in elastic case under gravity load, and γmax = 0.866 for avg. SD = 3.78 mrad in stiff case and γmax = 0.863 for avg. SD = 3.81 mrad in elastic case under both wind and gravity loads, resulting to be the best among considered models. Maximum weight reduction of up to 30% in stiff case and up to 4.5% in elastic case has also been observed compared to conventional glass collector for hybrid composite model thus reducing the tracking power and producing a cost effective system.
Solar collector field design and viability analysis of stand-alone parabolic trough power plants for Indian conditions
The parabolic trough collector is one of the most proven and commercial concentrating solar power (CSP) technologies. The implementation of parabolic trough in large scale power plants is an effective solar energy option in an arid and semi-arid region. In this article, analysis of solar parabolic trough collector field for power generation is carried out using different working fluids like oil and water. The analysis of collector field for power generation is carried out based on the various geometric parameters (rim angle, collector aperture); collector configurations (spacing distance, shading distance, land area) and solar radiation. The land area required for different plant operating hours and insolation conditions are analyzed. The optimum configuration of the collector field is found as 6m aperture, rim angle (Ψrim)=65° with spacing distance between the collector rows equivalent to shading distance after 2h of sunrise at δ=0° and plant operates between 1h after sunrise and before sunset. Techno-economic feasibility analysis of solar trough power plant is carried out for 58 locations in India. The annual power generation capacities of solar trough power plant are estimated for various locations such as eastern (14), western (18), northern (15) and southern (11) regions of India. The levelised costs of electricity generation of stand-alone solar parabolic trough power plant are estimated with oil and water as working fluids and it is found that Rs. 11.00 (¢ 24) and Rs. 11.84 (¢ 26) for oil and DSG respectively for Jodhpur. © 2012 International Energy Initiative.
Wind load and structural analysis for standalone solar parabolic trough collector
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.
Simulation studies of thermal and electrical performance of solar linear parabolic trough concentrating photovoltaic system
This paper presents thermal and electrical analyses of solar linear parabolic trough concentrating photovoltaic (CPV) collector system under different design and operating conditions. The receiver tube receives concentrated non-uniform solar flux over its outer surface, leading to high local temperature and large circumferential temperature difference. A Compound Parabolic Collector (CPC) has been incorporated as a secondary reflector to homogenize the flux. The co-generation system consists of a Parabolic Trough Collector (PTC) with 5.1 m2 aperture area (AAP) and a highly reflective mirror with dual axis tracking. The study envisages maximizing electrical output using CPV with non-uniform thermal energy over receiver tube. Various configurations are analyzed which include 2-cell and 3-cell strings without CPC and 3-cell and 4-cell strings with CPC. The detailed thermal and electrical analysis carried out for all the cases using Al2O3/Water nanofluid with 0%, 1% and 6% vol. and various synthetic fluids with constant velocity of 0.1 m/s. The flux values for the thermal analysis have been imported from the non-sequential ray tracing optical simulation software ASAP. Maximum thermal and electrical output is computed to be 2592.42 W with 78.2% thermal efficiency by 2-cell without CPC configuration using Syltherm-800 and 692.2 W with 20.88% electrical efficiency by 3-cell without CPC with Al2O3/Water (φ = 1%) respectively. Reduction in electrical output by ∼7.2–9.8% and enhancement in thermal output by ∼0.91–1.16% has been observed on replacing nanofluids with synthetic fluids. Long lasting synthetic fluids leads to higher cell temperatures hence higher cell degradation but nanofluids give optimized electrical and thermal output with lower cell temperatures. Numerical results are compared with reference data which shows the reasonable agreement.
4-E (energy-exergy-environmental-economic) analyses of line-focusing stand-alone concentrating solar power plants
In this study, energy-exergy-environmental-economic (4-E) analyses of stand-alone line-focusing concentrating solar power plants are carried out for different plant capacities ranging from 1 to 50 MWe. Solar power plants based on concentrating power technologies are used to harness the solar radiation effectively. Among the solar power technologies, line-focusing concentrating systems such as linear Fresnel reflector (LFR) and parabolic trough collector (PTC) are simple in design and cost-effective with high dispatchability. The energy and exergy efficiencies of various components of the solar field and power block are determined. The overall energy and exergy efficiencies of 50-MWe LFR power plants are estimated as 12.17 and 17.21% and 23.16 and 32.76%, respectively, for the PTC power plant. The results show that a maximum energy loss occurs in the solar field and power block for LFR and PTC power plants respectively, and a maximum exergy loss occurs in the solar field for both power plants. The analyses of solar power plants have been carried out to estimate the environmental benefits; the results showed that a 1-MWe stand-alone line-focusing concentrating solar power plant can save 1813 tonnes of CO2, 12.52 tonnes of SO2, 6.23 tonnes of NOx and 0.98 tonnes of particulate matter annually compared with that of an Indian subcritical coal power plant. The levelized electricity cost for the LFR- and PTC-based stand-alone solar power plant varies from INR 14.77 to INR 10.19 and INR 14.7 to INR 8.48 for the plant capacities that vary from 1 to 50 MWe. © The Author 2012. Published by Oxford University Press. All rights reserved.
Experimental investigation of porous disc enhanced receiver for solar parabolic trough collector
In this article, experimental investigation of 15m2 solar parabolic trough collector with porous disc enhanced receiver is carried out according to ASHRAE 93-1986 test procedure. Six different receiver configurations are developed and investigated to compare their performance. The performance of solar parabolic trough collector with two conventional and four porous disc receivers is characterized in terms of time constant, collector acceptance angle, peak performance, daily performance and heat loss tests. The tests are carried out for wide range of flow rates (100L/h-1000L/h) and weather conditions. Based on experimental investigation, the time constant of the parabolic trough collector is varied from 70s to 260s for different receiver configurations. The collector acceptance angle is determined for both un-shielded tubular receiver (USTR) and shielded tubular receiver (STR) as 0.58° and 0.68° respectively. The collector efficiencies are obtained as in the range of 63.9%-66.66% under ASHRAE standard test condition. Off-Sunset heat loss test is conducted to determine the steady state heat losses from the parabolic trough collector receiver. The heat losses from the parabolic trough collector are in the range of 455W/m2-1732W/m2 for average fluid temperature of Tamb+30°C. Stagnation temperature of the collector is obtained as 258°C and 312°C respectively for USTR and STR corresponding to direct normal insolation (DNI) of 786W/m2 and 761W/m2. Based on the above analysis, the porous disc enhanced receiver improves the performance of the parabolic trough collector significantly and it can be used effectively for process heat applications.
Design, development and performance investigation of solar Parabolic Trough Collector for large-scale solar power plants
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.
Numerical investigation of entropy generation in a solar parabolic trough collector using supercritical carbon dioxide as heat transfer fluid
Parabolic trough collector (PTC) is a widely used and efficient Concentrating Solar Power (CSP) technology for generating solar thermal power. Supercritical CO2 (s-CO2) is a heat transfer fluid (HTF) that shows good promising for use in solar PTC for further improvement in its efficiency and operations. A numerical thermal model is developed to understand the performance of s-CO2 as an HTF in a solar PTC. The local temperature and velocity fields were used to calculate the entropy generated within HTF due to finite temperature differences and fluid flow friction. A commercially available LS-3 parabolic trough collector is used for the analysis with a modified receiver. An optical analysis tool based on Monte Carlo Ray tracing is used to calculate non-uniform heat flux distribution around the circumference of the PTC receiver. Entropy generated at various operating pressures, inlet temperatures, and inlet Reynolds number using s-CO2 as HTF is calculated and analyzed. Results showed that entropy generated in the PTC receiver is reduced to a minimum at optimal Reynolds number for each of the operating pressures and inlet temperatures of the HTF. The Bejan number estimates the contribution of entropy generated due to heat transfer irreversibilities to the entropy generated due to heat transfer and fluid flow irreversibilities which is between 0.2 and 0.4 at high flow rates and close to 1 at low flow rates. Exergy efficiency analysis supported the optimized inlet boundary conditions.
Thermal analysis of solar parabolic trough with porous disc receiver
In this paper, 3-D numerical analysis of the porous disc line receiver for solar parabolic trough collector is presented. The influence of thermic fluid properties, receiver design and solar radiation concentration on overall heat collection is investigated. The analysis is carried out based on renormalization-group (RNG) k-ε turbulent model by using Therminol-VP1 as working fluid. The thermal analysis of the receiver is carried out for various geometrical parameters such as angle (θ), orientation, height of the disc (H) and distance between the discs (w) and for different heat flux conditions. The receiver showed better heat transfer characteristics; the top porous disc configuration having w = di, H = 0.5di and θ = 30°. The heat transfer characteristic enhances about 64.3% in terms of Nusselt number with a pressure drop of 457 Pa against the tubular receiver. The use of porous medium in tubular solar receiver enhances the system performance significantly. © 2008 Elsevier Ltd. All rights reserved.
Numerical investigation of solar parabolic trough receiver under non uniform solar flux distribution
Three dimensional numerical modeling of parabolic trough receiver is performed to study the non uniform flux distribution on the outer surface of the receiver by coupling Monte Carlo Ray-Tracing Method (MCRT) with the Finite Volume Method (FVM) and calculated non uniform flux distribution is considered as a thermal boundary condition. The numerical model is solved by considering RNG k-ϵ turbulent model. In this paper, different Heat Transfer Fluids (HTF) with respect to the various operating parameters such as mass flow rate, Direct Normal Irradiation (DNI), inlet temperature and ambient conditions are considered. The temperature profile of both absorber and glass envelope follows the non-uniform solar heat flux distribution curve. Three dimensional temperature distribution of the absorber tube is calculated numerically for different inlet temperature and velocity of HTF. The maximum solar heat flux attained by the PTC receiver is 9753.3 W/m2, 19506 W/m2, 29260 W/m2, and 39013 W/m2 when the DNI are 200 W/m2, 400 W/m2, 600 W/m2, and 800 W/m2 respectively.