Parabolic Trough Solar Power Plant Research Articles

Effect of short cloud shading on the performance of parabolic trough solar power plants: motorized vs manual valves

This paper uses a dynamic bio-inspired model to simulate cloud movement over a parabolic trough collector solar field. Time-stamped spatially varying solar radiation records resulting from that dynamic model are successively fed into an instantaneous flow distribution model of the same solar field. Two different flow control strategies are simulated to evaluate and compare their impact on plant performance. One strategy employs manual balancing valves resulting in an uneven exit temperature from each loop during cloud cover periods. The other strategy employs motorized balancing valves that constantly adjust to achieve a common desired exit temperature from each loop during cloud cover periods. Model output of both strategies under four different cloud shading conditions are compared. Simulation results showed that employing motorized balancing valves will result in a more efficient operation involving less pressure drop, higher outlet temperature and less pumping load; however, the rate of power generation was almost the same in both strategies.

Thermal analysis of linear solar concentrator for indirect steam generation

The thermal performance of a Parabolic Trough Solar Power Plant (PTSPP) is critical to the overall efficiency of the system. The advancement of this technologies has led to the development of steam production and efficient solution that utilizes the sun’s energy for thermal power generation. In this work a parabolic trough concentrator with aperture area of 10.8 m2 was designed and evaluated in the Research and Technology Center of Energy (CRTEn) in Tunisia. This type of concentrating solar power collector is analyzed for indirect steam generating system. Several parameters, as thermal characterization of absorber; thermal efficiency of mixed heat exchangers; thermal efficiency, concentration ratio and quantification of steam generation, were considered in order to study their effects on energy efficiency. Experimental results show that the receiver of parabolic trough concentrator extracts 552.73 W of absorbed energy. We found that the thermal energy efficiency varies from 24% to 28% for PTSPP system and reach an average concentration factor around 200. As results, the maximum value of the steam generated by parabolic trough concentrator is 8 kg/h.

Optimal Operation Strategies into Deregulated Markets for 50 MWe Parabolic Trough Solar Thermal Power Plants with Thermal Storage

The evolution of electric generation systems, according to relevant legislation, allows for the parallel evolution of the installed power capacity of renewable resources with the development of technologies for renewable resources, therefore optimizing the choice of energy mix from renewable resources by prioritizing the implementation of concentrating solar thermal plants. Thanks to their great potential, parabolic trough solar thermal power plants have become the most widely spread type of electricity generation by renewable solar energy. Nonetheless, the operation of the plant is not unique; it must be adapted to the parameters of solar radiation and market behavior for each specific location. This work focuses on the search for the optimal strategies of operation by a mathematical model of a 50 MWe parabolic trough thermal power plant with thermal storage. The analysis of the different ways of operation throughout a whole year, including model verification via a currently operating plant, provides meaningful insights into the electricity generated. Focused to work under non-regulated electricity markets to adjust this type of technology to the European directives, the presented model of optimization allows for the adaptation of the curve of generation to the network demands and market prices, rising the profitability of the power plant. Thus, related to solar resources and market price, the economic benefit derived from the electricity production improves between 5.17% and 7.79%.

Exergy Optimization of a Novel Combination of a Liquid Air Energy Storage System and a Parabolic Trough Solar Collector Power Plant

In this paper, a parabolic trough solar collector (PTSC) plant is combined with a liquid air energy storage (LAES) system. The genetic algorithm (GA) is used to optimize the proposed system for different air storage mass flow rates. The roundtrip exergy ratio is considered as the objective function and pressures of six points and mass flow rates of five points are considered as design parameters. The effects of some environmental and key parameters such as different radiation intensities, ambient temperatures, output pressures of the second compressor, and mass flow rates of the collectors fluid on the exergy ratio are investigated. The results revealed that the system could produce 17526.15 kJ/s (17.5 MW) power in high demands time and 2233.48 kJ/s (2.2 MW) power in low demands time and the system shows that a value of 15.13% round trip exergy ratio is achievable. Furthermore, the exergy ratio decreased by 5.1% when the air storage mass flow rate increased from 10 to 15 kg/s. Furthermore, the exergy ratio decreases by increasing the collectors inside fluid mass flow rate or by decreasing radiation intensity.

A hybrid molten carbonate fuel cell and parabolic trough solar collector, combined heating and power plant with carbon dioxide capturing process

In this paper, a combined heating and power plant consisting of molten carbonate fuel cell and parabolic trough solar collector with the carbon dioxide capturing process is investigated. Electrochemical model of the fuel cell and numerical modeling of the solar system is done using MATLAB software and thermodynamic model of the power plant is done by HYSYS software. In this plant, solar system is used as a heat exchanger with a capacity of 10.4 MW. The gas turbine and molten carbonate fuel cell are able to produce 640 MW and 81 MW of electrical power, respectively. The results show that, the electrical, overall and exergy efficiencies of the power plant are 37.68%, 71.29% and 45.13%, respectively. Also, total exergy destruction of the process and carbon capture ratio are 346029 kW and 91%, respectively. The impacts of other parameters such as fuel and oxidant flow rate, outlet pressure of the turbine, air compressor and control valves and capacity of the solar farm on the performance of the process are also investigated.

Numerical analysis of magnetic field effects on the heat transfer enhancement in ferrofluids for a parabolic trough solar collector

A parabolic trough is defined as a type of solar thermal collector that is straight in one dimension and curved as a parabola in the other two, lined with a polished metal mirror. Enhancing the thermal efficiency of this collectors is one of the major challenges of developing and growing of parabolic trough solar thermal power plants. Ferrofluids were proposed as a novel working fluid for industrial applications, due to their thermal performances. In this study, the convective heat transfer of Fe3O4-Therminol 66 ferrofluid under magnetic field (0–500 G) is evaluated using computational fluid dynamics. The ferrofluid with different volume fraction (1–4%) and the Therminol 66 (as the base fluid) are considered as the working fluids for a parabolic trough solar collector. Numerical analysis first validated using theoretical results, and then a detailed study is conducted in order to analyze the effect of the magnetic field on different parameters. The result demonstrated that using magnetic field can increase the local heat transfer coefficient of the collector tube, thermal efficiency as well as output temperature of the collector. In addition, increasing the volume fraction of nanoparticle in the base fluid and intensity of magnetic field increased the collector performance.

Dynamic performance and stress analysis of the steam generator of parabolic trough solar power plants

The thermal stress on thick-walled components, such as tubesheets and steam drums, limits both the temperature ramp-up rates and the temperature differences between outer and inner walls. The cyclic operation of concentrating solar power plants may lead to fatigue damage. For these reasons, a stress analysis of the steam generator is required to assure its lifetime.A methodology is presented for the thermo-mechanical analysis of the steam generator for a parabolic trough power plant. This methodology consists of coupling transient thermodynamic and stress models of the heat exchangers in order to calculate the stress. Besides the heat exchanger models, a transient model for a TEMA H heat exchanger is proposed. Finite element simulations are carried out to calculate the deviations of the simplified analytical models. In this way, a powerful tool that allows the analysis and optimization of the steam generator operation is proposed.The results suggest that U-tube tubesheets are exposed to high thermal stresses on the no-tube-lane zone, especially in the reheater. The steam generator start-up can be accomplished in around 45 min using 36.4 MWhth. Furthermore, the TEMA X evaporator presents a thermal stress reduction of 35% compared to the kettle evaporator.

Optimal start-up operating strategies for gas-boosted parabolic trough solar power plants

Concentrating solar power plants are taking an increasing share in the renewable energy generation market. Parabolic trough is one of such technologies and the most commercially mature. However, this technology still suffers from technical challenges that need to be addressed. As these power plants experience daily start-up procedures, the optimal performance in transient operation needs to be considered. This paper presents a performance based modelling tool for a gas-boosted parabolic trough power plant. The objective of the paper is to define an optimal operational strategy of the power plant start-up procedure with the aim of minimizing its fuel consumption while at the same time maximizing its electric energy output, taking into account all the thermo-mechanical constraints involved in the procedure. Heating rate constraints of the steam generator and the booster heater, and the steam turbine start-up schedule were considered. The simulation model was developed based on a power plant located near Abu Dhabi, and was validated against real operational data with a maximum integral relative deviation of 4.3% for gross electric energy production. A multi-objective optimization was performed for a typical operating week during winter and spring weather conditions. The results suggest that in order to minimize the fuel consumption and at the same time maximize the electric energy production, an evaporator heating rate of 6 K/min is an optimal value both for winter and spring conditions.

Modeling and performance study of a parabolic trough solar power plant using molten salt storage tank in Egypt: effects of plant site location

Modeling and performance study of large parabolic trough solar power plant using molten slat storage tank is conducted and presented for three different locations in Egypt (Aswan, Al-Arish and Hurghada) using 16 h storage system. The simulation algorithm and solar modeling have been created and simulated by MATLAB/SIMULINK program. A comparison between studied cities is introduced to select the best location for constructing the solar plant based on selection criteria; hot header outlet temperature, volume (hot and cold) variations during charging and discharging, and cycle power efficiency. A full design of the thermal power plant with the storage tanks is also conducted using a molten salt (60% NaNO3 and 40% KNO3). Moreover, hourly electricity plant output to obtain the influence of the thermal storage tank on the plant performance was calculated and presented. The results indicated that Aswan city is the optimum location to construct a 500 MW solar power plant under the Egyptian climate. A comparison for current model validation between simulated results and the actual results of existing plant (Archimede) was fulfilled and good agreement was obtained by maximum error 5%.

Modeling and dynamic simulation of a steam generation system for a parabolic trough solar power plant

Abstract In a parabolic trough solar power plant, the steam generation system is the junction of the heat transfer fluid circuit and the water/steam circuit. Due to the discontinuous nature of solar radiation, the dynamic characteristics of working fluid physical parameters, such as mass flow rate, temperature, and pressure, are more evident in the steam generation system in this kind of plant, increasing the complexity of system operation. In this paper, a zero-dimension dynamic model of an oil/water steam generation system was developed based on the lumped parameter method. Based on the developed model, four typical single-parameter disturbance processes were simulated, and then the control strategy was obtained. System-level simulations on different days (clear and cloudy) and in different seasons (spring, summer, autumn, and winter) were also conducted on a STAR-90 simulation platform using real meteorological data. The simulation results show that PI control can be used to adjust the water level, that system operation on cloudy days should be avoided, and that the system can continue to generate steam after the sun sets. The simulation results can provide a useful reference for plant operators.

Numerical analysis of a new thermal energy storage system using phase change materials for direct steam parabolic trough solar power plants

This paper presents the numerical analysis of a novel thermal energy storage (TES) system using phase change material (PCM) for direct steam solar power plants. The energy storage system consists a preheater, steam generator and superheater in a cascade arrangement. The performance of the integrated system that constitutes a novel concept of thermal storage system is analyzed, numerically. The numerical model is verified against experimental data and the realistic effects of the operating conditions on the energy storage system performance are considered. The effects of different design parameters on the performance of the system are investigated. The effects of thermal conductivity of PCM, heat transfer fluid (HTF) flow rate and the diameter of heat exchanger tubes are analyzed during the entire thermal cycling of the evaporator. The effects of HTF flow rate and temperature on the exergy efficiency of TES system are analyzed. The results indicate that thermal conductivity of PCM is the most effective parameter, and increase of this parameter from 0.5 to 5 W K−1 m−1 leads to decrease of charging time from 25 to 4.5 h and increase of output steam quality from 0.2 to 0.5 during the discharging process. It is observed that cascade arrangement in preheater and superheater heat exchangers results in lower temperature gradient of the output HTF.

Impact of steam generator start-up limitations on the performance of a parabolic trough solar power plant

Concentrating solar power plants are an attractive option in the renewable energy generation market. The possibility of integrating relatively cheap forms of energy storage makes them a desirable solution when power generation must be readily available at any time of the day. Solar power plants typically start-up and shut down every day, so in order to maximize their profitability, it is necessary to increase their flexibility in transient operation and to initiate power generation as rapidly as possible. Two of the key components are the steam generator and steam turbine and the rates at which they can reach operational speed are limited by thermo-mechanical constraints. This paper presents an analysis of the effects of the thermal stress limitations of the steam generator and steam turbine on the power plant start-up, and quantifies their impact on the economy of the system. A dynamic model of a parabolic trough power plant was developed and integrated with a logic controller to identify start-up limitations, and subsequently the dynamic model was integrated in a techno-economic tool previously developed by the authors. The plant was analysed under two different operating strategies, namely solar-driven and peak-load. The results indicate that for steam generator hot start-ups, a 1.5% increase in peak-load electricity production would be achieved by doubling the maximum allowable heating rate of the evaporator. No useful increase would be achieved by increasing the rates beyond a limit of 7–8 K/min, as the turbine would then be the main limiting component during start-up. Similar conclusions can be drawn for the solar-driven case, for which the solar field and the energy source availability would pose the major constraint when starting up the steam generator system.

Fatigue analysis of the steam generator of a parabolic trough solar power plant

This work proposes a methodology to perform the fatigue analysis of the steam generator of a parabolic trough power plant. The following methodology assumes cycling duty scenario (300 start-ups and shut downs per year). Two start-up operations of the steam generator are analyzed: evaporator temperature ramp and heat transfer fluid temperature ramp. Furthermore, a part load operation is studied.The results show that the most compromised parts of the steam generator are the reheater tubesheet for the TEMA CFU design, the steam drum-downcomer junction and the superheater nozzle. Besides, former reheater design (TEMA CFU) does not fulfil the 25-year lifetime condition. To overcome this problem, two alternative designs for the reheater are proposed: U-shell and two TEMA CFU in series. Finally, the lifetimes of TEMA NXU and kettle evaporator designs are compared. Our results show that TEMA NXU allows temperature ramps up to 9 °C/min without putting the steam generator lifetime at risk, whereas kettle temperature ramps greater than 5 °C/min do not fulfil the designed lifetime of 25 years.Respect to the load changes, the evaporator drum is the most stressed element. A 50% load change produces a damage equivalent to 60% of the damage produced by a daily start-up/shut-down cycle.

Characterization and Corrections for Clamp-On Fluid Temperature Measurements in Turbulent Flows

A clamp-on measurement system for flexible and accurate fluid temperature measurements for turbulent flows with Reynolds numbers higher than 30,000 is presented in this paper. This noninvasive system can be deployed without interference with the fluid flow while delivering the high accuracies necessary for performance and acceptance testing for power plants in terms of measurement accuracy and position. The system is experimentally validated in the fluid flow of a solar thermal parabolic trough collector test bench, equipped with built-in sensors as reference. Its applicability under industrial conditions is demonstrated at the 50 MWel AndaSol-3 parabolic trough solar power plant in Spain. A function based on large experimental data correcting the temperature gradient between the measured clamp-on sensor and actual fluid temperature is developed, achieving an uncertainty below ±0.7 K (2σ) for fluid temperatures up to 400 °C. In addition, the experimental results are used to validate a numerical model. Based on the results of this model, a general dimensionless correction function for a wider range of application scenarios is derived. The clamp-on system, together with the dimensionless correction function, supports numerous combinations of fluids, pipe materials, insulations, geometries, and operation conditions and should be useful in a variety of industrial applications of the power and chemical industry where temporal noninvasive fluid temperature measurement is needed with good accuracy. The comparison of the general dimensionless correction function with measurement data indicates a measurement uncertainty below 1 K (2σ).

Performance Analysis and Optimization of a Parabolic Trough Solar Power Plant in the Middle East Region

The Middle East is one among the areas of the world that receive high amounts of direct solar radiation. As such, the region holds a promising potential to leverage clean energy. Owing to rapid urbanization, energy demands in the region are on the rise. Along with the global push to curb undesirable outcomes such as air pollution, emissions of greenhouse gases, and climate change, an urgent need has arisen to explore and exploit the abundant renewable energy sources. This paper presents the design, performance analysis and optimization of a 100 MWe parabolic trough collector Solar Power Plant with thermal energy storage intended for use in the Middle Eastern regions. Two representative sites in the Middle East which offer an annual average direct normal irradiance (DNI) of more than 5.5 kWh/m2/day has been chosen for the analysis. The thermodynamic aspect and annual performance of the proposed plant design is also analyzed using the System Advisor Model (SAM) version 2017.9.5. Based on the analysis carried out on the initial design, annual power generated from the proposed concentrating solar power (CSP) plant design in Abu Dhabi amounts to 333.15 GWh whereas that in Aswan recorded a value of 369.26 GWh, with capacity factors of 38.1% and 42.19% respectively. The mean efficiency of the plants in Abu Dhabi and Aswan are found to be 14.35% and 14.98% respectively. The optimization of the initial plant design is also carried out by varying two main design parameters, namely the solar multiple and full load hours of thermal energy storage (TES). Based on the findings of the study, the proposed 100 MW parabolic trough collector solar power plant with thermal energy storage can contribute to the sustainable energy future of the Middle East with reduced dependency on fossil fuels.

An integrated program of a stand-alone parabolic trough solar thermal power plant: Code description and test

Solar thermal systems produce steam after being energized by solar parabolic trough concentrators, are incorporated with a steam turbine-generator assembly to produce electricity. This study presents a code for prediction of performance, while under-taking preliminary plant-sizing for a variety of parabolic trough solar fields operating under nominal conditions. The code, named as PTPPPP (Parabolic Trough Power Plant Performance Predictor) consists of four blocks. The code allows prediction of variables including: heat loss coefficient, UL, aperture effective direct normal irradiance, I, heat gain, Qgain, and the thermal efficiency of stand-alone parabolic trough solar thermal power plant in commerce, ηp. The conceptual design of the stand-alone parabolic trough solar involves: selection and sizing of system components, power generation cycles, working fluid types, and power block sizing. The input weather parameters and the operational parameters to the code have been acquired from in-situ measurements. The prediction results of the code have been found in good agreement with literature data with mean error of 0.18% in prediction of output power. In addition, this code is able to provide a flexibility in terms of temperature, heat transfer, and pressure range.

Energy and exergy analyses of a parabolic trough solar power plant using carbon dioxide power cycle

This paper examines both energy and exergy performances of parabolic trough collectors (PTCs), as part of a solar power plant, under different design and operating conditions. The proposed solar power plant utilizes an innovative supercritical carbon dioxide (S-CO2) power cycle to convert the heat produced by the PTCs to power. In addition, the present system integrates a thermal energy storage (TES) to overcome the intermittent nature of solar energy and extend the hours of operation. Therefore, detailed thermodynamic and heat transfer analyses are conducted to assess heat losses, exergy destructions, and energy and exergy efficiencies. The state-of-the-art PTCs technologies are considered to set the design parameters used in the modeling of the solar field. Furthermore, the effects of varying some operating conditions on the energy and exergy performance of the PTCs and the S-CO2 power cycle are investigated. These parameters include beam radiation intensity, beam incidence angle, and receiver emittance. Subsequently, the resultant impacts of changing these parameters on the overall solar power plant energy and exergy efficiencies are examined. The energy and exergy efficiencies of the PTC are found to be 66.35% and 38.51%, respectively.

Potential assessment of using dry cooling mode in two different solar thermal power plants.

Most of Concentrating Solar Power (CSP) plants are usually installed in desert regions where water resource availability is a critical limitation due to the lack of water required for the exploitation of these systems in these regions. Therefore, the aim of this study is to investigate the techno-economic competitiveness of deploying both modes of cooling (wet and dry) in two different parabolic trough solar thermal power plants integrated with thermal energy storage and fuel backup system; the first one is using thermic oil, while the other is working using molten salt. The obtained results show that the dry cooling mode can decrease the yields of the two power plants down to 8.7 % and 9.3 % for oil and salt configurations respectively. On the other hand, the levelized cost of electricity can increase by using this cooling option up to 9.3 % for oil plant, and 10.0 % for salt one. However, the main advantage of using dry cooling option is reducing water consumption which has been decreased by more than 94 % for both plants. The application of our methodology to other two sites worldwide, confirms the viability of the obtained results. The importance of this results is to show the effect of working fluids on the cooling system of solar power plants.

Thermal load and bending analysis of heat collection element of direct-steam-generation parabolic-trough solar power plant

The reliability of heat collection element (HCE) in parabolic trough collector (PTC) system is of importance to the solar thermal energy harvesting. The present work proposes the 2D-finite volume method (FVM) and 3D-finite element volume (FEM) coupled model to conduct the thermal load and bending analysis of the HCE of direct-steam-generation (DSG) PTC solar power plant. The emphasis is focused on the evaporation and superheating stages of a DSG loop in re-circulation mode due to the presence of the phase-change process and the relatively lower heat transfer performance, respectively. It is found that the thermal deflection is far less than 1cm for a 4-m HCE in the evaporation stage. However, in the superheating stage with DNI=1000Wm−2 (DNI being the direct normal irradiance), the circumferential temperature difference and the deflection of a 4-m HCE can reach up to 48°C and 2.16cm, respectively. It should be pointed out, based on the present work, that the non-uniform heating and local overheating issues exist in the evaporation and superheating stages, respectively, the latter of which seems more serious and potentially causes damage.

Nonlinear Adaptive Control of Heat Transfer Fluid Temperature in a Parabolic Trough Solar Power Plant

Control of highly nonlinear processes such as solar collector fields is usually a challenging task. A common approach to this problem involves deploying a set of operation point range-specific controllers, whose actions are to be combined in a switching strategy. Discontinuities in control actions upon switching may lead to instabilities and, therefore, achieving bumpless transitions is always a concern. In addition, linear adaptive predictive controllers need to cope with nonlinearities by using high adaptation speeds, often leading to model vulnerability in the presence of aggressive perturbations. Finally, most of the proposed solutions rely on complex plant model developments. In this work, a multivariable nonlinear model-based adaptive predictive controller has been developed and tested against a parabolic trough solar power plant simulation. Since the model employed by this controller accounts for process nonlinearities, adaptation speed can be dramatically reduced, therefore increasing model robustness. The controller is easily initialized and is able to identify and track the process dynamics, including its nonlinearities as it evolves with time, thus requiring neither process up-front modeling nor switching. The presented controller outperforms its linear counterpart both in terms of accuracy and robustness and, due to the generality of its design, it is expected to be applicable to a wide class of linear and nonlinear processes.