Parabolic Trough Power Plants Research Articles

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.

Design and Implementation of the Solar Field and Thermal Storage System Controllers for a Parabolic Trough Solar Power Plant

Dynamic simulation provides an efficient approach for improving the efficiency of parabolic trough power plants and control circuits. In the dynamic simulation, the possibilities and operating conditions of the plant are evaluated regarding materials, processes, emissions, or economics. Several studies related to the dynamic simulation of the parabolic trough technology are summarised and discussed in this work. This study is the first research that presents a thorough description of the advanced control circuits used in the solar field and thermal storage system of a parabolic trough power plant. This power plant was implemented using advanced process simulation software (APROS). The dynamic model was built based on the real specifications of the power plant.

Design and performance analysis of a parabolic trough power plant under the climatological conditions of Tamanrasset, Algeria.

Algeria’s energy demands are tremendously growing, and on the African continent it ranks among the countries with the highest energy consumption. To counter its growing energy demand, the country is progressively adopting renewable energy technologies, although conventional energy technologies still play a central role in its electricity production. The huge solar energy potential in Algeria can be exploited and utilized to meet the country’s growing energy demand with minimal greenhouse gas production. Given that concentrating solar power is viewed as one of the most promising alternatives in the field of solar energy utilization, this study investigates the viability of a 100 MW parabolic trough-based power plant at Tamanrasset, Algeria. The plant was simulated in the System Advisor Model software considering the actual electricity load profile of the targeted location and implementing two different condenser types: evaporative and air-cooled. By comparing the plant’s electricity production to the city’s real load, the plant was in position of supplying about 78% and 60% of the city’s electricity demand during the winter and summer seasons, respectively. The results show that implementation of such CSP plants could play an important role in meeting the energy demand as well as mitigating climate change through greenhouse emissions avoided in electricity generation process.

Evaluating the Potential Benefit of Using Nowcasting Systems to Improve the Yield of Parabolic Trough Power Plants with Single-Phase HTF

Solar field developers include innovative solutions to optimize the energy production of their plants. Simulation tools play a significant role in the design and testing phases as they provide estimations of this yield in different conditions. Transient processes, like passing clouds and solar field start-up, are specifically challenging to optimize and estimate using such simulation tools. Solar fields are subject to high degree of both temporal and spatial variability in the energy input and a detailed estimation can be achieved by simulating subsystems within acceptable time and computational power. Hence, such simulation tools cannot be utilized for tests under realistic operation conditions. The Virtual Solar Field is a computationally efficient simulation tool that allows a detailed transient simulation of parabolic trough solar fields based on single-phase fluids. Using this tool, developers could reproduce a transient test case with exactly the same disturbances to provide fair comparisons between different configurations. In this paper, an evaluation process based on numerical simulations using the Virtual Solar Field is presented. The economic benefit of novel innovative control concepts can be assessed according to the presented scheme. This is demonstrated by evaluating the potential benefit of availability of spatial DNI nowcasts on the control of parabolic trough solar fields. Results show that nowcasting can increase the economic revenue of commercial power plants by up to 2.5% per day. This proves the feasibility of installing such systems.

Optimal sizing of a concentrated solar power system powering an autonomous water pumping system using the modified electric systems cascade analysis

The optimal sizing by the Modified Electric Systems Cascade Analysis method (MESCA) of an autonomous water pumping system powered by the electrical energy produced by a parabolic trough power plant is the main objective of this work. The desired pumping system consists of pumps powered by the CSP system without thermal energy storage. Also, a water storage tank is used to guarantees the autonomy of the system. The climatic data of the Oujda city (our case study) and the technical and economic data of the system components are used as inputs for the MESCA algorithm, to obtain the size of the parabolic trough power plant and the capacity of the various system components corresponding to the optimal configuration with the minimum Life Cycle Cost as economic criteria.

Design of a 100 MW Concentrated Solar Power Plant Parabolic Trough in Riyadh, Saudi Arabia

The increase in energy demand and the awareness of renewable energy has been raised due to environmental and climate change and the need to establish sustainable energy development. Using fossil fuels has created a critical situation such as; climate change, air pollution, and emission of greenhouse gases also, the resources are in limited supply. The infinite source of energy such as; the sun can provide an effective and sustainable energy supply. Riyadh city in Saudi Arabia is one of the areas that receive a high quantity of direct solar radiation. An average direct normal irradiance (DNI) for the central region is equal to 2018 kWh/m2/year. This paper shows the design and the performance analysis of 100 MW Concentrated Solar Power (CSP) parabolic trough (PT) power plants with thermal energy storage (TES) for use in Riyadh city. The performance of this design plant is analyzed by using the system advisor model (SAM). Based on the analysis carried out for this design, the capacity factor is equal to 45.3% with an annual energy generation which is equal to 396, 801, 792 kWh. By varying two main parameters, the solar field size and the full load hours of TES to get the optimal design of this plant is done. Based on the simulation result, the proposed design of 100 MW parabolic trough at 1, 150, 000 m2 solar field size and 7 h TES gives the lowest Levelized Cost of Electricity (LCOE) with an assumed lifespan of the plant of 25 years.

Techno-economic optimization for implantation of parabolic trough power plant: Case study of Algeria

This paper deals with Hassi R'mel's solar power plant, a solar power plant one (SPPI) located in Algeria's southern region. The current configuration of the SPPI is a 25 MW parabolic trough used with 130 MW connected cycle gas turbines. In this paper, a techno-economic analysis of the solar part of the SPPI is described. A multiobjective optimization process was carried out to find the most favorable conditions, the most suitable parameters, and the solar power plant's optimum design configuration for better energy production in the future. We optimized the solar multiple, the fossil fill fraction of the backup system, and a full load of thermal storage system for the minimum levelized cost of electricity (LCOE) and the maximum capacity factor. The results showed that the lowest LCOE reached about 5.83 €/kWh for a solar multiple of 1.6. The optimum value of fossil fill fraction is 0.2, with a capacity factor of 60%, and the best optimization of the storage system is 4 h. The optimum power plant produced 118.26 GWh per year. It was concluded that the use of wet cooling was more economical than dry cooling and that among the heat transfer fluids, Therminol VP1 was the best. The validation of the theoretical results confirmed their agreement with the SPPI and solar energy generation system-VI power plants' experimental data. These findings proved that concentrating solar power may be considered as the right solution in countries in the desert and equatorial regions, the Middle East and North Africa region, especially Algeria, where abundant solar energy is available.

Pressure drops, heat transfer coefficient, costs and power block design for direct storage parabolic trough power plants running molten salts

Direct circulation of molten salts in the solar field of parabolic trough solar power plants may be a possible breakthrough to decrease their levelized cost of electricity. While prototypes are being erected around the world, this study addresses the main concerns and changes that are related to the replacement of thermal oils by molten salts, i.e. pressure drops, heat transfer coefficient, anti-freezing solutions, cost and power block design. It combines: 1) an analytical comparison of both technologies with respect to pressure drops and heat transfers; 2) simulations of a 50 MWe/7.5 h-of-storage power plant, using NREL’s SAM software, providing details on the dynamics of the outputs and parasitics. It has been observed the following: 1) pressure drops in the solar field are smaller running molten salts instead of thermal oil, thanks to higher operating temperature ranges; 2) HitecXL molten salt leads to lower electricity consumption than Therminol VP-1 oil and Solar Salt (parasitics); 3) a 6.3% reduction of the levelized cost of electricity when running HitecXL, ∼14.80 c€/kWh, instead of Therminol VP-1, ∼15.80 c€/kWh; 4) simpler power block designs can be considered for the higher operating temperatures of molten salts, resulting in higher efficiencies and/or cheaper power blocks.

Optimization and techno-economic assessment of concentrated solar power (CSP) in South-Western Africa: A case study on Ghana

The techno-economic performance of two different CSP technologies i.e. Solar tower (ST) and parabolic trough (PT) were evaluated in this paper, each at two different locations in Ghana (Navrongo and Tamale) using the System Advisor Model (SAM) software. From the simulated results, levelized cost of energy (LCOE) of 13.67 ¢/kWh and 14.73 ¢/kWh were recorded for the ST modelled at Navrongo and Tamale, respectively. The PT power plant simulated at Tamale and Navrongo also recorded an LCOE of 28.83 ¢/kWh and 25.83 ¢/kWh, respectively. It was observed that, the optimum solar multiple (SM) for the ST ranges between 1.4 and 1.9, this is because the least LCOEs for the different thermal energy storage (TES) periods are within that range. In the case of the PT power plants, the SM also depends on the period of the TES and each TES has a distinct SM ranging between 2.4 and 4. Results from the analysis suggests that the ST technology is the optimal system for the Ghanaian weather conditions. The study concludes that the bankability of CSP technology in Ghana depends on the type of financial conditions for the project. Therefore, appropriate policies from government are necessary to help in their development.

Spectral beam splitting retrofit for hybrid PV/T using existing parabolic trough power plants for enhanced power output

Conversion of sunlight into electricity is the fastest growing commercial means of deploying renewable energy at utility scale. The two primary methods for conversion are photovoltaics and concentrating solar thermal power. The complimentary advantages of these two methods motivates interest in hybridizing the two. Here, a spectral beam splitting approach is designed and tested for application as a retrofit in existing parabolic trough concentrating solar power facilities, the first large scale test using such an approach with low-cost silicon photovoltaic cells. Such an approach leverages the existing capital cost of the plant with the potential to boost plant output. The novel on-sun testing here focused on the electrical performance of a silicon photovoltaic module integrated into the most common parabolic trough geometry with a net aperture area of 1.7 m2. The spectral beam splitter has a solar weighted reflectance of 71.2%, and delivered an average flux to the cells of 17,828 W/m2 representing a concentration ratio of 25×, within 10% of the prediction of the optical ray tracing model. The two photovoltaic modules achieved an average efficiency - based upon measured irradiance delivered to the cells - of 12.4% (or 3% if normalized to the total aperture of the area of the mirror). A corresponding decrease in thermal performance was observed when the retrofit was added. Overall the design is capable of providing a path to retrofit existing parabolic trough powerplants to provide a 13% increase in power output using commercially available photovoltaic technology.

Modeling and dynamic simulation of thermal energy storage system for concentrating solar power plant

Thermal energy storage system in concentrating solar power plants can guarantee sustainable and stable electricity output in case of highly unstable solar irradiation conditions. In this paper, the lumped parameter method is used to develop the models of different thermal energy storage systems. In order to improve the reliability as well as the prediction accuracy of developed models, the charging/discharging process is firstly simulated, and then the dynamic characteristics of thermal energy storage systems are fully tested by imposing 15% step disturbance of mass flow. The results show that the charging/discharging characteristics of the three different thermal energy storage systems are almost the same, which have little to do with the storage mediums used in the systems. Besides, for the representative 1MWe solar parabolic trough power plant, a 15% step up disturbance of oil mass flow will result in a small increase (1.8% and 1.3% respectively) on the outlet temperature of oil and molten salt. On the other side, a 15% step down disturbance of oil mass flow will lead a 2.7% and 2.2% decrease on the outlet temperature of oil and molten salt respectively. In order to verify the validity of the proposed models, the simulation results are compared with both the design points and representative experimental data from the 1MWe solar parabolic trough power plant. The results show that the maximum relative error is not more than 1% when comparing with the design points and the maximum relative error is not more than 12% when comparing with the representative experimental data. Conclusions of this paper are good references for system design, control and commissioning of concentrating solar power plants.

Optimization of parabolic trough power plant operations in variable irradiance conditions using all sky imagers

The continuously growing penetration of intermittent electricity sources will increase the future demand for dispatchable power plants, which balance out fluctuations within the electrical grids. Parabolic trough power plants with thermal energy storages could be one renewable solution for regions with a high yearly direct normal irradiance (DNI) sum, but in order to compete against other renewable as well as non-renewable technologies, the economic competitiveness must be ensured. Price reductions can be achieved for example by optimizing the plant operation. One shortcoming of state of the art plant controllers is that they only use the DNI measured at one or a few positions in the solar field. Due to the spatial variability of the DNI throughout the solar field this DNI information can be misleading.In this paper, we investigate the optimization potential of solar field control strategies with access to spatially resolved DNI information from all sky imagers (ASI). Uncertainties of the ASI system are considered by introducing additional independent spatial DNI information from a shadow camera system. The spatial and temporal DNI variability of the DNI seen by the controller is classified in distinct DNI variability classes. Two new control strategies are developed, with optimized control parameters for distinct combinations of the spatial and temporal DNI variability classes.These new variability class dependent control strategies are benchmarked in a simulation environment. A relative increase in revenue in excess of 1.9% is observed over a test period with 22 days, compared to a state of the art reference controller.

Thermo-economic analysis of photovoltaic, central tower receiver and parabolic trough power plants for Herat city in Afghanistan

In Afghanistan, more than 60% of the population does not have access to a reliable source of electrical energy. A thermo-economic analysis is conducted to compare the performance of a Photovoltaic (PV), Central Tower Receiver (CTR) plant and a Parabolic Trough Collector (PTC) plant with and without storage for the city of Herat, in Afghanistan. The nominal capacity of both plants is 110 MWe. The PTC plant with energy storage has the highest efficiency of about 43% that is approximately 50% more than the PV plant, however, the PV plant has more uniform power production profile. The output power of PTC with energy storage is 25% more than output power of PTC without energy storage and output power of CTR plant is half of PTC plant with energy storage. The Levelized Cost of Electricity (LCOE) is 0.146 $/kWh for CTR plant, 0.063 $/kWh for PV plant, 0.1076 $/kWh for PTC plant with energy storage, 0.104 $/kWh for PTC plant without storage and 0.12 $/kWh for PTC plat without storage and without backup fossil fuel systems. Increase of incentive by 10% leads to decrease of LCOE by about 20% for PTC and 13% for PV and 12% for CTR power plants.

Techno-economic assessment and environmental impact of concentrating solar power plants in Iran

This study aims to assess the technical, economic, and environmental aspects of parabolic trough and solar tower power plants under the climatic conditions of south-central regions of Iran with an average direct normal irradiation of about 6 kWh/m2/day. The effects of power plant capacity, cooling system, solar multiple, and hours of thermal energy storage on the techno-economic performance of the power plants are examined. In addition, the environmental metrics including reduction of CO2 emissions, fossil fuel saving, and energy payback time are evaluated. Four power plant capacities of 20, 50, 100, and 200 MWe along with two cooling options, including dry and wet are investigated. Besides, the solar multiple and capacity of thermal energy storage are varied from 1.0 to 4.0 with a step of 0.1, and from 0 to 18 h with a step of 1 h, respectively. The ground weather data from the meteorological organization of Iran are used as input data in the System Advisor Model software. Based on the results, the optimal configurations for the studied power plants concerning the techno-economic parameters are determined. It is revealed that the dry-cooled solar tower power plant with a capacity of 100 MWe, 14 h storage system, and solar multiple of 3.0 is the most efficient configuration under the studied climatic conditions. For this concentrating solar power plant, the levelized cost of electricity and solar-to-electricity efficiency are 11.3 ¢/kWhe and 14.7%, respectively. Furthermore, the energy payback time is about 15 months, annual CO2 emissions reduction is 399 kilotons, and annual fossil fuel saving is 190 million cubic meters of natural gas.

Modelling and performance analysis of parabolic trough solar concentrator for different heat transfer fluids under Malaysian condition

With the increasing energy demand, depleting fossil fuel, and commitment to the Paris climate agreement, Malaysia should tap into this natural resource and harness its solar energy potential. In this research, a location in Malaysia was chosen based on its yearly direct normal irradiance (DNI) and an optimization strategy for a potential parabolic trough power plant. Besides that, an energetic and exergetic comparison and analysis between 6 HTFs (Pressurized water, Therminol VP-1, Syltherm 800, Solar salt, Hitec XL) on real-world climatic condition (based on Malaysian climatic condition) with varying inlet temperature level (300K–900K), ambient temperature and wind speed was done by using 1-D mathematical model that was coded in MATLAB®. Bayan Lepas received the highest yearly DNI and Sodium liquid outperformed other HTFs at varying DNI and inlet temperature level except at 300K with an advantage ranging between 0.036% and 0.99% in thermal efficiency and 0.438%–0.85% in exergetic efficiency to other HTFs. Sodium liquid at the temperature level of 700K also showed the strongest exergetic gained for any potential implementation of PTSC power plant in Malaysia. For climatic impact on the performance of HTFs, Energetic performance increase with ambient temperature while exergetic performance showed otherwise for all HTFs. Wind speed increment has a negligible impact on PTSC performance for all HTFs with sodium liquid’s performance being the most resistant to any wind increment.

Comparative assessment of classical heat resistance and Wilson plot test techniques used for determining convective heat transfer coefficient of thermo fluids

The present study relates to testing the thermo fluids used for solar thermal power plants for their heat transfer coefficients. Two techniques – the Classical Heat Resistance Method and – the Wilson Plot Technique has been used to experimentally calculate the heat transfer coefficients. In comparison to the Classical Heat Resistance Method, the Wilson Plot Technique is able to cater to the transition flow regime as well as the two-phase fluids which is the nature of the existing commercially available solar grade heat transfer oil “based on diphenyl oxide-diphenyl chemistry” used for parabolic trough power plants. An analysis of repeatability and reproducibility of the two test techniques using the coefficient of variation and standard error of mean calculations shows that the heat transfer coefficients obtained through Wilson Plot Technique is within the experimentally acceptable range of 10% while those obtained from Classical Test Method falls beyond the acceptable range but are still within the workable range of 20%. The standard error of mean also exhibit similar results with the values in case of Wilson Method being much smaller than those in case of Classical Heat Resistance Method. Based on the test results obtained and for the specific geometry of the test setup, the authors have proposed an empirical relationship between the velocity of the oil flowing inside the tube and the mean temperature of the oil including a correction factor of 2.3. Finally, the convective heat transfer coefficient of oil hi up to the permissible operational temperature range of 400 °C of the solar grade oil was calculated based on the proposed empirical relationship. The Wilson Plot Technique shows better fit with the commonly used Dittus-Boelter equation of calculating the convective heat transfer coefficient of oils. The method proposed in the work shall help experimentally evaluate the new chemistries used for heat transfer oils for their convective heat transfer coefficients.

The effect of soiling on the reflectance of solar reflector materials - Model for prediction of incidence angle dependent reflectance and attenuation due to dust deposition

The accumulation of dust and soil on the surface of solar reflectors is an important factor reducing the effective use of solar energy, especially for concentrating solar power plants. In this study, we investigated glass-based mirrors exposed in the desert and mirrors soiled in the laboratory. We achieved artificial, controlled soiling with different soil types by use of an in-house dusting device and measured scattering, hemispherical and specular reflectance. Results showed that small-angle scattering due to dust is noticeable and severely reduces reflectance of mirrors with otherwise high specularity. Prominent result is a significant decrease of reflectance for increasing local solar incidence angles, for example from 0.91 at 8° incidence angle to 0.84 at 70° incidence angle. Therefore, we present a model to predict specular reflectance for different levels of cleanliness. The model applies the Lambert-Beer law and relates the incidence angle dependent attenuation of solar radiation to the dust layer. An application of our model to optical yield prediction indicated a significant relative decrease in predicted annual optical efficiency of up to 1.5% for parabolic trough power plants. In future research, a similar method could be adapted to predict optical losses of photovoltaic modules with flat cover glass.

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.

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.