Parabolic Trough Power Plants Research Articles

Thermodynamic analysis of a parabolic trough power plant integrating supercritical carbon dioxide Brayton cycle and direct contact membrane distillation

This research advances current efforts to develop 3rd gen concentrated solar power (CSP) systems, addressing current research and practical implementation gaps. It focuses on key challenges identified by the academic community: advanced power cycles and utilising waste heat effectively to enhance efficiency. This research introduced a novel system comprising a direct parabolic trough with supercritical carbon dioxide (sCO2) Brayton cycle, and a Direct Contact Membrane Distillation (DCMD) desalination system, aiming to overcome these barriers. The methodology entailed developing a mathematical model and conducting thermodynamic analyses to evaluate system efficiencies, the impact on water production, and the number of DCMD units needed under various conditions. The results reveal that both thermal and exergetic efficiencies decline with decreasing direct normal irradiance across all pressure ratios with the optimal efficiency observed at pressure ratios of approximately 3.1 to 3.2 with exergetic efficiency of around 0.383. Higher bulk temperature differences increased water production and reduced need for direct contact membrane distillation units. However, an initial decline and subsequent rise in water production at bulk temperature differences of 10 °C and 20 °C indicates that feed temperature alone does not determine water production capacity. The existence of an inverse correlation between the cycle’s efficiency and water production prompted the introduction of a unifying coefficient, the Integrated Performance Coefficient (IPC), peaking at 50.32 between pressure ratios of 3.1 and 3.2. High bulk feed temperatures combined with low bulk permeate temperatures enhance water production but also increase its vulnerability to variations in direct normal irradiance. Conversely, increased bulk permeate temperatures lessen the effect of direct normal irradiance changes on water production, albeit with a reduced output.

Design Basis Document / Owner’s Technical Specification for Nitrate Salt Systems in CSP Projects

Work has begun on a Design Basis Document / Owner’s Technical Specification for parabolic trough and central receiver power plants using nitrate salt as the heat transport fluid and the thermal storage medium. A principal topic of recent interest is the failures of the hot salt tanks in central receiver projects. The paper outlines a hypothesis for the source of the failures, and discusses a range of possible solutions.

Demonstration of 3.5 MWth Parabolic Trough With Ternary Molten Salt at the Évora Molten Salt Platform

Commercial solar thermal parabolic trough power plants use thermal oil as a heat transfer medium in the solar field. Within the framework of the “High Performance Solar 2” (HPS2) research project a molten salt parabolic trough demonstration plant was commissioned in summer 2021 in Évora, Portugal. Since then it has been operated for more than 5.500 h between 180°C and 500 °C, jointly by the University of Évora, DLR and TSK Flagsol. This article presents the main steps of cold and hot commissioning as well as experiences gained in plant operation. It has been shown that filling a preheated solar field with ternary molten salt is not critical, but its drainage can be challenging depending on the quality of the heat tracing and the solar field slope.

Techno-economic feasibility analysis of a large-scale parabolic trough thermal power plant in Effurun-Warri, Nigeria

Abstract 
 In the modern world, solar energy is one of the most mature renewable energy resources for electricity generation. Because of the growing interest in green energy and CO2 reduction, concentrated power technologies have gained prominence all over the world. Several parabolic trough power plants are currently operational in various parts of the world. However, despite the region's favorable weather conditions, Nigeria and Sub-Saharan Africa have yet to adopt this technology. To galvanize the integration of solar energy into the energy infrastructure in Nigeria, technical and economic feasibility studies are required. This paper presents a techno-economic viability assessment of a 25 MW Parabolic Trough solar thermal power plant for electricity generation in Effurun-Warri, Nigeria. The System Advisor Model (SAM) software was used for the analysis, based on the validated technical and financial models inbuilt into the software. Results showed that the plant is technically feasible in Effurun-Warri with a capacity factor of over 35%, which compares favourably with other similar plants across the globe. However, the levelized cost of electricity (LCOE) of 11.87 cents/kWh obtained is significantly higher than the subsidized cost of electricity in the country, by about 99%, leading to a negative net present value of the project. To improve cost, optimized design parameters of the plant should be adopted for performance simulation in the SAM software.

Heat transfer improvement using additive manufacturing technologies: a review

To provide a comprehensive review of additive manufacturing use in heat transfer improvement and to carry out the economic feasibility of additive manufacturing compared to conventional manufacturing. Heat transfer improvement is particularly interesting for different industrial sectors due to its economic, practical, and environmental benefits. Three heat transfer improvement techniques are used: active, passive, and compound.According to numerous studies on heat transfer enhancement devices, most configurations with strong heat transfer performance are geometrically complex. Thus, those configurations cannot be easily manufactured using conventional manufacturing. With additive manufacturing, almost any configuration can be manufactured, with the added benefit that the produced parts’ surface characteristics can enhance heat transfer. It can, however, lead to a significant pressure drop increase that will reduce the overall performance. In the given article, a comparison of the capital cost of a 100 MW parabolic trough power plant has been carried out, considering two types of solar receivers; the first is manufactured using conventional methods, and the second uses additive manufacturing. The heat transfer of the new receiver configuration is investigated using computational fluid dynamics through ANYS Fluent.Although the cost of additive manufacturing machines and materials is high compared to conventional manufacturing, the outcome revealed that the gain in efficiency when using additive-manufactured receivers leads to a reduction in the number of receiver tubes and the number of solar collectors needed in the solar field It implies a considerable reduction of parabolic trough collector plant capital cost, which is 20.7%. It can, therefore, be concluded that, even if initial setup expenses are higher, additive manufacturing could be more cost-effective than traditional manufacturing.With the reduction of the parabolic trough collector plant capital cost, the levelized cost of electricity will eventually be reduced, which will play a role in increasing the use of solar thermal energy.No review studies discuss the manufacturing potential and cost-effectiveness potential of additive manufacturing when producing heat transfer improvement equipment, especially when producing long pieces. In addition, the paper uses a novel receiver configuration to investigate the economic aspect.

Potential Assessment and Economic Analysis of Concentrated Solar Power against Solar Photovoltaic Technology

Competition between concentrated solar power and solar photovoltaic has been the subject of frequent debate in recent years based on their cost of fabrication, efficiency, storage, levelized cost of energy, reliability, and complexity of respective technologies. Taking Pakistan as a testbed, a study was conducted to determine which technology is economical in a particular location and climate. The study assesses the meteorological, orographic, and spatial factors that impact the performance and cost of both renewable energy systems. A SWOT analysis, followed by technoeconomic analyses, was conducted to determine suitable sites for setting up solar power plants in Pakistan. A detailed assessment of siting factors for solar power plants was conducted to shortlist the most suitable sites. Based on the results, economic analysis was performed to install 100 MW photovoltaic and parabolic trough power plants at selected locations. The levelized cost of energy for the 100 MW parabolic trough is 10.8 cents/kWh and 12 cents/kWh in best-case scenarios, i.e., for locations of Toba and Quetta, respectively, whereas the LCOEs of 100 MW photovoltaic systems stand comparatively low at 7.36 cents/kWh, 7.21 cents/kWh, 7.01 cents/kWh, 6.82 cents/kWh, 6.02 cents/kWh, and 5.95 cents/kWh in Multan, Bahawalpur, Rahim Yar Khan, Hyderabad, Quetta, and Toba, respectively. The results favor choosing solar PV plants over solar CSP plants in terms of finances in the selected regions. The findings will assist financiers and policymakers in creating better policies in terms of long-term goals.

Evaluation of cross-contamination in indirect thermal storage system in concentrated solar plants

Solar concentration technology is fully dispatchable due to the use of thermal energy storage systems, in particular, commercial parabolic trough power plants use indirect storage systems based on molten salts. This system includes a heat exchanger to transfer energy between the thermal oil from the solar field and the salts used in storage. In addition, some content of water is considered by cross-contamination in the steam generator of the power block. This study analyses the compatibility between both fluids in the event of cross-contamination in the equipment. The degree of compatibility between a triphasic system made up of a mixture of sodium nitrate and potassium nitrate salts (60:40), heat transfer fluid (DP:DPO), and water, when they were subjected to 390 °C for a period of 312 h (two weeks). The study shows how thermal oil undergoes complete thermal-oxidative degradation without high impact on the composition of the salts.

A novel dual feedwater circuit for a parabolic trough solar power plant

The validated dynamic model of a parabolic trough power plant (PTPP) is improved by the combination of a new feedwater circuit (feedwater/HTF circuit) and a reference feedwater circuit (feedwater/steam circuit) as well as the development of the steam turbine model. Such design represents the first effort of research to utilize a dual feedwater circuit inside the PTPP to increase the power output in the daylight from 50 to 68 MWel and raise night operating hours at a lower cost. The purpose of increasing the operating night hours at a power (48 MWel) as in the reference PTPP is to get rid of the fossil fuel backup system and rely only on the absorbed solar energy and the stored energy in the molten salt. During daylight hours, the feedwater circuit is operated using Feedwater/HTF. In the transient period, the feedwater/HTF circuit will gradually be closed due to a decrease in solar radiation. Furthermore, the rest of the nominal feedwater mass flow rate (49 kg/s) is gradually replenished from the feedwater/steam circuit. After sunset, the entirety of the feedwater is heated based on the steam extracted from the turbine. The purpose of this improvement is to raise the number of nightly operational hours by reducing the nominal load from 61.93 to 48 MWel as a result of low energy demand during the evening hours. Therefore, a comparison study between the reference model and this optimization (optimization 2) is conducted for clear days (26th–27th/June and 13th–14th/July 2010) in order to understand the influence of dual feedwater circuit. The comparison indicates that the operational hours of the power block (PB) will be obviously increased. Moreover, this improvement reduces based on the fossil fuel system at night. As the last step, an economic analysis was performed on the costs of the referenced and the optimized PTPP as a function of the levelized energy cost (LEC). The results illustrate that the specific energy cost of a PTPP with 7.5 h of storage capacity is lowered by about 14.5% by increasing the output of the PTPP from 50 to 68 MWel.

Thermo-mechanical investigation of the multi-layer thermocline tank for parabolic trough power plants

Thermo-mechanical investigation of the multi-layer thermocline tank for parabolic trough power plants

Modeling and Performance Assessment of a Hypothetical Stand-Alone Parabolic Trough Solar Power Plant Supported by Climatic Measurements in Ipoh, Malaysia

Abstract This study presents a conceptual design for a concentrated solar power plant by using direct steam generation and a stand-alone power system based on a concentration of solar parabolic troughs. The system is located at the solar research site (SRS) of Universiti Teknologi PETRONAS in Ipoh, Malaysia. The model system uses an integrated turbine with 1.2 kW generators, and steam is generated by a flow loop powered by solar parabolic trough concentrators. An in-situ calculation of normal direct irradiance was conducted in SRS and used as an input for the mathematical model. The model was developed to assess the transient behavior of the system and the behavior of the projected power generation under seasonal variations and daily solar radiation. The parabolic trough power plant achieved the highest average output of 8.85% during the low rainfall season in March.

A Review of Parabolic Trough Collector (PTC): Application and Performance Comparison

In these circumstances, we must search forward to ‘green energy’ for power generation. Green energy means environment-friendly and non-polluting energy (inclusive of solar, biomass, wind, tidal, etc.). Concentrated Solar Power (CSP) generation is one of the maximum promising candidates for mitigating the destiny power crisis. The extracted energy from CSP technology may be very clean, dependable, and environmentally friendly. A review of the parabolic trough collector (PTC) which is one of the CSP technology with a focus on the components, the working principle, and thermal properties of the parabolic trough collector. Also, this study explains the parabolic trough power plants with tracking systems, from the other hand, evaluates the effects of using many types of reflectors and multi kinds of working fluids on the performance of the parabolic trough collector (PTC), in addition of that study presents the use of PTCs in many applications.

Modelling, simulation and optimisation of parabolic trough power plants

We present a mathematical model built to describe the fluid dynamics for the heat transfer fluid in a parabolic trough power plant. Such a power plant consists of a network of tubes for the heat transport fluid. In view of optimisation tasks in the planning and in the operational phase, it is crucial to find a compromise between a very detailed description of many possible physical phenomena and a necessary simplicity needed for a fast and robust computational approach. We present the model, a numerical approach, simulation for single tubes and also for realistic network settings. In addition, we optimise the power output with respect to the operational parameters.

Novel feedwater preheating system for parabolic trough solar power plant

Several improvements in the referenced parabolic trough power plant (PTPP) model (Andasol II) have been implemented by APROS software. The main advantage of this novel feedwater preheating system is to improve electricity production and evening operation hours at a low cost for modifying an existing PTPP in Spain. This in turn leads to less dependence on fossil fuels during the evening and cloudy periods. The reference model is improved by an increase in the collector loops in the reference solar field (SF) model to 208 loops rather than 156 loops to increase the absorbed thermal power, increasing the capacity of the thermal storage system (TSS) from 1017 MWth h to 1,360 MWth h to improve the night operating period, replacing the Feedwater/Steam circuit with a Feedwater/HTF circuit using five shell and tube counter-current heat exchangers that are used instead of condenser heat exchangers. The HTF enters the fifth low-pressure preheater with 128 kg/s and 393 °C in the daytime and 377 °C at night. The main advantage of this improvement is to use the entire generated steam within the steam turbine and not to heat the feedwater in the feedwater circuit. In addition, the control circuits are modified and added new controllers with new limitations for controlling the new operating conditions. This development is the first attempt in the field of research to use a Feedwater/HTF circuit in the PTPP in order to enhance performance. This improvement (optimization 1) in turn leads to a raise in the total HTF mass flow and the quantity of stored molten salt, as well as increasing the mass flow of HTF to the power block (PB). According to optimization 1, no steam will be taken out of the HP and LP-turbine toward the feedwater circuit. Therefore, the feedwater fed through new preheaters is heated by thermal oil instead of steam extractions. The predictions obtained from this optimization are compared to the simulated results that were previously extracted from the reference model on clear and cloudy days for evaluation of the behaviour of the optimized PTPP. It should be mentioned here that it can be used the same turbine and generator in the actual power plant to achieve this increase in the performance of the power plant, according to the technical data of manufacturers. Finally, an economic study of the cost was conducted for referenced and the optimized PTPP depending on the levelized energy cost (LEC). The findings reveal that the levelized energy cost of the optimized PTPP with storage energy is about 10.5% lower than that of the referenced PTPP.

Advances in Process Modelling and Simulation of Parabolic Trough Power Plants: A Review

The common design of thermal power plants is fundamentally oriented towards achieving a high-process performance, with market demands necessitating enhanced operational stability as a result of ongoing global support for renewable energy sources. Indeed, dynamic simulation represents one useful and cost-effective choice for optimizing the flexibility of parabolic trough power plants (PTPP) in a range of transient operating conditions, such as weather changes, resulting again in variations of the output load as well as varying start-up times. The purpose of this review is to provide an overview of steady-state and dynamic modelling for PTPP design, development, and optimization. This gives us a greater opportunity for a broad understanding of the PTPPs subjected to a variety of irradiance solar constraints. The most important features of the steady-state and their uses are reviewed, and the most important programs used in steady-state modelling are also highlighted. In addition, the start-up process of the plant, thermal storage system capacities and response dynamics (charging and discharging modes), and yearly electricity yield can be analyzed using dynamic modelling. Depending on the dynamic simulation, specific uses can be realized, including control loop optimization, load estimation for critical in-service equipment, and emergency safety assessment of power plants in the event of an outage. Based on this review, a detailed overview of the dynamic simulation of PTPP, and its development and application in various simulation programs, is presented. Here, a survey of computational dynamic modelling software commonly applied for commercial and academic applications is performed, accompanied by various sample models of simulation programs such as APROS, DYNAMICS, DYMOLA, and ASPEN PLUS. The simulation programs generally depend on the conservation equations of mass, momentum, species, and energy. However, for the equation of equilibrium, specific mathematical expressions rely on the basic flow model. The essential flow models involved, together with the basic assumptions, are presented, and are supplemented through a general survey covering popular simulation programs. Various previous research on the dynamic simulation of the PTPP are reviewed and analyzed in this paper. Here, several studies in the literature regarding the dynamic simulation of the PTPP are addressed and analyzed. Specific consideration is given to the studies including model verification, in order to explore the effect of modelling assumptions regarding the simulation outputs.

Parabolic trough field control utilizing all sky imager irradiance data – A comprehensive robustness analysis

Parabolic trough (PT) power plants focus the sun's irradiation onto an absorber tube using collector mirrors to increase the temperature of the heat transfer medium (HTF). In the power plant, the HTF is used to generate electricity. To heat up the HTF, PT solar fields are set up in large areas and pipes are used to distribute the HTF in the solar field. The control system adjusts the temperature by changing the mass flow into the solar field and the focusing of the individual collectors. Transient conditions such as cloud passage are the main challenge for the system. State of the art control schemes use information from a few irradiation measuring points in the solar field. These measurement points are precise for the individual location but cannot accurately represent the irradiation situation in the whole solar field. In this paper, a control system that uses spatially resolved irradiation information from all sky imager systems is investigated.First, the control system was developed and tested in various simulation runs under ideal conditions. The focus of this work is to investigate the robustness of the control concept under non-ideal conditions. For this purpose, the simulation conditions are adapted to real situations and the behavior of the control system is analyzed.A robust behavior of the control system is shown in the simulations under different non-ideal scenarios. Overall, an improvement in electrical yield of 1.4% can be achieved compared to a reference without access to spatially resolved irradiance data.

Dynamic Modelling and Advanced Process Control of Power Block for a Parabolic Trough Solar Power Plant

A fundamental task in the dynamic simulation of parabolic trough power plants (PTPP) is to understand the behavior of the system physics and control loops in the presence of weather variations. This study provides a detailed description of the advanced controllers used in the power block (PB) of a 50 MWel parabolic trough power plant (PTPP). The PB model is achieved using APROS software based on the actual specifications of the existing power plant. To verify the behaviour of the PB model, a comparison between the simulated results and given real data is documented depending on a previous study, and the results indicate a reasonable degree of correspondence. The purpose of this study is to create reference models for the PB. Thereby, developers and engineers will have a better understanding of the state of the art of advanced control loops in these power plants. Moreover, these types of models can be used to specify the most suitable mode of operation for the power plant. In addition, this study gives an overview of dynamic simulation for the design, optimisation and development of power blocks in parabolic trough power plants.

Efficient utilization of waste heat from molten carbonate fuel cell in parabolic trough power plant for electricity and hydrogen coproduction

Direct steam generating parabolic trough power plant is an important technology to match future electric energy demand. One of the problems related to its emergence is energy storage. Solar-to-hydrogen is a promising technology for solar energy storage. Electrolysis is among the most processes of hydrogen production recently investigated. High temperature steam electrolysis is a clean process to efficiently produce hydrogen. In this paper, steam electrolysis process using solar energy is used to produce hydrogen. A heat recovery steam generator generates high temperature steam thanks to the molten carbonate fuel cell's waste heat. The analytical study investigates the energy efficiency of solar power plant, molten carbonate fuel cell and electrolyser. The impact of waste heat utilization on electricity and hydrogen generation is analysed. The results of calculations done with MATLAB software show that fuel cell produces 7.73 MWth of thermal energy at design conditions. 73.37 tonnes of hydrogen and 14.26 GWh of electricity are yearly produced. The annual energy efficiency of electrolyser is 70% while the annual mean electric efficiency of solar power plant is 18.30%.The proposed configuration based on the yearly electricity production and hydrogen generation has presented a good performance.

Experimental determination of convective heat transfer coefficients of synthetic oil using wilson plot technique

This paper describes the experiments to determine the convective heat transfer coefficients on a synthetic heat transfer fluid flowing in a Shell-and-Tube heat exchanger. The analysis of results is carried out by application of the Wilson plot Technique, on the basis of which, the convective heat transfer coefficients were experimentally obtained for the fluid flowing inside the tube. The convective heat transfer coefficient of oil derived through Wilson plot is then compared with the convective heat transfer coefficients obtained using the classical thermal resistance equation. An empirical correlation between the convective heat transfer coefficient of oil with respect to its mean velocity of flow in the tube and the bulk oil temperature has been proposed. A correction factor of 2.3 and exploration of the exponent value of 0.2 pertaining to the velocity of oil was obtained. The values of convective heat transfer coefficients obtained after applying the correction factor are consistent with the values reported in the literature for oil-water heat transfers. The variation of the heat transfer coefficients at different temperatures is attributed to factors like vapor blanketing effect, surface temperature measurement difficulty as well as dependence of convection phenomenon on surface geometry and physical conditions of the fluids. Experimental results obtained for a temperature range of 50-200°C are extrapolated upto 400°C, the actual upper operational fluid temperatures used in concentrated solar parabolic trough power plant. The test method proposed in this paper can be useful for the development of oil as heat transfer fluids, where already established or commercialized oil is compared with the oil under development, in the same test setup and under similar test conditions.

A Comparison Study on the Improved Operation Strategy for a Parabolic trough Solar Power Plant in Spain

The present work focuses on the development of a detailed dynamic model of an existing parabolic trough solar power plant (PTSPP) in Spain. This work is the first attempt to analyse the dynamic interaction of all parts, including solar field (SF), thermal storage system (TSS) and power block (PB), and describes the heat transfer fluid (HTF) and steam/water paths in detail. Advanced control circuits, including drum level, economiser water bypass, attemperator and steam bypass controllers, are also included. The parabolic trough power plant is modelled using Advanced Process Simulation Software (APROS). An accurate description of control structures and operation strategy is necessary in order to achieve a reasonable dynamic response. This model would help to identify the best operation strategy due to DNI (direct normal irradiation) variations during the daytime. The operation strategy used in this model has also been shown to be effective compared to decisions made by operators on cloudy periods by improving power plant performance and increasing operating hours.

Hydrogen production through parabolic trough power plant based on the Organic Rankine Cycle implemented in the Algerian Sahara

This paper investigates overall performance of a small-scale electrolytic hydrogen production, using an Organic Rankine Cycle (ORC) driven by a parabolic trough collector (PTC) plant, under the Algerian Sahara climate. The evaluations of PTC plant and the thermodynamic analysis of the ORC are performed by SAM and EES software, respectively. These results are then used for hydrogen production calculations. Among three southern cities investigated, Ghardaïa is most favorable site to implement the proposed system. For the ORC plant, eight alternative working fluids (butane, n-pentane, isopentane, benzene, toluene, R245fa, R123 and water), are considered for comparison. As results, the highest output power and plant efficiency are achieved with benzene during May to August with maximum power of 8.74 kW and cycle efficiency of 21.65% during July. The highest hydrogen production rate is achieved in July with 847 Nm3 using the high temperature water vapor electrolyzer and benzene as working fluid.