Solar Thermal Power Plants Research Articles

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.

The potential of arch-shaped fins for energy-charge enhancement in triplex-tube heat storage: Comparative analysis and optimization

Incorporating PCMs with thermal storage systems offer significant potential for improving the energy efficiency of diverse applications, including solar thermal power plants, air conditioning systems, and building heating and cooling systems. However, a key challenge in designing these systems is achieving efficient and rapid PCM melting during the charging process. This study aims to analyze and report on the potential of arch-shaped fins in enhancing the melting rate and overall performance of horizontal triplex-tube storage systems. The influences of fin base height and fin connecting angles were analyzed via simulations. The optimal arch-shaped fin design reduced melting time by 53 % and improved heat storage rate by 117 % compared to the no-fin case. Specifically, equal inner/outer fin base heights of 10 mm minimized melting time to 14.8 min and maximized heat storage to 477.2 W. Increasing the inner fin connecting angle from 0° to 120° decreased melting time by 15.2 % to 12.1 min and increased heat storage by 18.0 % to 591.3 W. Reducing the outer fin connecting angle from 240° to 0° reduced melting time by 10.8 % to 11.5 min and improved heat storage by 12.3 % to 591.3 W. These findings would have implications for advancing the design and optimization of heat storage systems, leading to improved performance and increased utilization of sustainable energy sources.

Economic Optimization of a Thermal Solar Power Plant That Operates With a HRB Cycle by Improving the Operation Schedule

In this paper, two solutions are proposed to increase the sales revenue of a pre-sized solar thermal power plant (STPP) that operates with a Hybrid Rankine Brayton cycle (HRB) by changing the reference operating parameters. In the first solution, the turbine inlet temperature value is optimized to increase the energy production. In the second solution, a new dispatch strategy that prioritizes energy production during the hours of higher sales price is additionally implemented in low solar radiation months. In the remaining months, the reference dispatch strategy that prioritizes production from energy coming directly from the solar field over energy from storage system is maintained. The incremental sales revenue of each solution proposed over the reference case is calculated considering hourly SPOT prices for a three-year period and considering hourly annual simulations for a typical year.

Macroencapsulation of sodium chloride by a double layer strategy for high temperature phase change thermal storage over 800 °C

To solve the key problems of high corrosiveness, easy leakage and low thermal conductivity of sodium chloride as phase change material (PCM) for high-temperature heat storage, this study reports a double-shell coating method to prepare centimeter-sized macrocapsules. The capsules are made of powder raw materials with the help of organic adhesives such as polyvinyl pyrrolidone and carboxymethyl cellulose for shape formation, in which the inner expanded graphite (EG) layer and the outer Al2O3 layer are coated on the salt core spheres and finally are sintered formed at high temperatures. The double-shell capsules can prevent salt from leakage because the inner EG layer is repellent to liquid salt, in contrast, the single Al2O3 shell is penetrated by liquid salt due to their wettability. After 100 cyclic tests, the double-shell capsules have good stability and high durability for long-term use. In order to improve the heat storage density of the capsules, the method of isostatically pressing the cores to increase the compactness is studied. At 200 MPa, the capsules in size of 20@2@2 show a high heat storage capacity of 1024.54 J/cm3 and 551.56 J/g from 600 to 900 °C. The double-shell encapsulated salt PCM can be widely used in high-temperature heat storage over 800 °C in solar thermal power plants and industrial waste heat recovery.

Produced-Water Desalination Approach Uses Renewable Thermal Energy

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 211175, “An Innovative Method of Water Management by Desalinating Produced Water Using Thermal Renewable Energy,” by Sharifa M. Al-Ruheili, Felix Tiefenbacher, and Khansaa H. Almahrami, ARA Petroleum Exploration and Production, et al. The paper has not been peer reviewed. _ The operator is adopting a method to manage high-salinity produced water in an environmentally sustainable way by extracting potable water from produced water and reducing discharge water volume by at least 50%. For desalination of the produced water, a combination of forward and direct osmosis technology is used. This process is driven mostly by thermal energy, which is provided to thermal collectors that are 100% solar. This technology uses renewable energy and will have no carbon footprint. Technology Description The technology involves concentrated solar thermal (CST) power plants that provide 100% renewable water desalination. Forward osmosis (FO) and direct osmosis (DO) can desalinate highly saline and polluted water, such as produced water, mainly with solar thermal energy. A pneumatic solar thermal plant consisting of two HELIOtube collectors, each 121 m long, provides the thermal energy for the desalination process. The plant includes a mirror technology based on CST, a cost-effective heat-transfer system using pressurized water as heat transfer fluid (HTF), and a low-maintenance thermal energy storage (TES) system allowing nighttime operations of 35 m3 volume with an operating temperature of 180°C using a pressurized water tank at 10-bar operating pressure. The desalination system will contain a pretreatment unit for the produced water and a desalination (FO) and brine-concentration (DO) unit. The unit will be integrated with thermal power to operate the desalination plant. In addition, a fully automated control system with a live backup will be installed. The system is classified as having low maintenance and cleaning costs because of its encapsulation features, rotatability of 300°, and convex shape. Fig. 1 of the complete paper shows the planned plant layout. The desalination plant will feature two outputs: fresh water of potable quality and brine. The fresh water will be used to serve the company’s freshwater demand, with excess water used for agricultural purposes or mixed with water in an injector well to improve injectivity. The other output, the highly concentrated brine (20% salt), will be collected in the existing evaporation pond where two main research and development studies are ongoing, one related to mineral extractions and the second related to salt monetization (using salt as a drilling additive).

Fate and transport analysis of a Dowtherm–A chemical release event

AbstractA hypothetical chemical release of Dowtherm–A into the environment was simulated using a chemodynamics code. The chemical release was assumed to come from a concentrating solar power plant adjacent to Lake Tahoe. Dowtherm–A is viscous water‐insoluble nonvolatile oil found mostly in liquid form at standard temperature and pressure; however, trace amounts slowly diffuse into the three environmental phases: air, water, and soil. It is a commercial eutectic binary mixture of diphenyl oxide and biphenyl—both are toxic and flammable. Therminol VP–1 is another commercial heat transfer oil made by Eastman that is essentially the same oil as Dowtherm–A made by Dow: same constituents at equal proportions. Therefore, the results reported in this study apply to both fluids. Solar thermal power generation represents a clean source of energy that almost uses no fossil fuels and thus does not emit any greenhouse gases. However, the oil employed in those solar thermal power plants is dangerous and should be carefully handled to avoid leakage.

Electrodeposited nickel coatings for exceptional corrosion mitigation in industrial grade molten chloride salts for concentrating solar power

Molten chloride salt eutectics are attractive candidates for use as thermal energy storage media and heat transfer fluids in generation-three concentrating solar thermal power (Gen3 CSP) plants. However, corrosion of alloys in molten chloride salts, especially at high temperatures, is an extremely challenging problem that studies focus on lower temperatures, shorter durations, or analytical grade, and high-purity, salts. To date, there has been no study on corrosion or corrosion mitigation in an industrial-grade salt at a high temperature such as 750 °C. To alleviate this knowledge gap, the study presents new multiscale fractal-textured Ni coatings on various alloy surfaces for effective corrosion mitigation at 750 °C in molten chloride salts. Using the electrodeposition method, durable double-layer textured coatings were formed on stainless steel alloys (SS316, SS310, and SS347) and In800H. The corrosion performance of the coatings is investigated in both analytical-grade purity and, for the first time, practically relevant industrial-grade chloride salts. Ni-coated ferrous alloys showed an exceptionally reduced corrosion rate in the range of 350–480 μm/y in analytical-grade salts, and between 450 and 490 μm/y in purified industrial-grade salts at 750 °C. Ni coatings on ferrous alloys reduced corrosion rates by as much as 70% compared to uncoated surfaces and were comparable to the expensive Ha230 alloy with a high Ni content. By the use of innovative fractal corrosion mitigation coatings, for the first time, low-cost structural alloys are rendered viable for use with industrial-grade chloride salts, which is profoundly beneficial in practical systems.

Life Cycle Assessment of the new Solar Thermal Power Plant SolarCAD II connected to a District Heating Network in Geneva, Switzerland

This paper presents a life cycle assessment (LCA) of the solar heat injected in a District Heating Network (DHN) by a new solar thermal power plant in Geneva. An environmental Life Cycle Assessment (LCA) is conducted according to ISO 14040, ISO 14044 and SN EN 15804+A2:2019. The scope of the study includes the complete life cycle of the solar power plant heat generation system. The baseline GHG emissions results show that the solar heat injected is responsible of about 15 to 18 gCO2-eq per kWh depending on whether we account for the environmental impacts of the steel gratings or not. This value is mostly determined by the manufacturing and use stages. Different sensitivity analyses are then performed in order to test the robustness of the main influential parameters (e.g., lifetime, efficiency, electricity mix) and better quantify the variability of the GHG emissions. Finally, this LCA study of a solar thermal plant connected to a Swiss DHN provides a first value of the solar heat in comparison with other heat production routes for DHN already provided in LCA databases such as the Swiss KBOB 2009/1:2022 platform for LCA in the construction sector.

Genetic algorithm optimization of heliostat field layout for the design of a central receiver solar thermal power plant

The heliostat field layout in a central receiver solar thermal power plant has significant optical losses that can ultimately affect the overall output power of the plant. In this paper, an optimized heliostat field layout based on annual efficiency and power of 50 MW for the local coordinates of Quetta, Pakistan, is proposed. The performance of two different heliostat field layouts such as radial staggered and Fermat's spiral distribution are evaluated and different design points in a year are considered for the analysis. The field layouts are then optimized using a rejection sampling based Genetic Algorithm (GA). It considers the output power and mean overall efficiency for vernal equinox, summer solstice, autumnal equinox, and winter solstice as objective functions. The GA optimizes the heliostat field parameters, namely, security distance (DS), tower height (TH), heliostat width to length ratio (WR), and the length of heliostats (LH). The study system was developed in MATLAB for validation. It was observed that for the radial staggered layout, the number of heliostats decreased by 364 and the efficiency was improved by 8.52 % using GA optimization relative to unoptimized results field layout. The annual efficiency for Fermat's spiral configuration was improved by 14.62 % and correspondingly, the number of heliostats decreased by 434.

Heat transfer in a fluidized bed tubular solar receiver. On-sun experimental investigation

Using particles as heat transfer fluid in a solar receiver is an attractive way to increase the global efficiency of solar power plants. In the case of the particle-in-tube solar receiver concept, the fluidized particles circulate vertically in tubes thanks to a controlled pressure gradient and an additional air injection. Experiments are conducted with olivine particles in a one-tube mock-up at the 1 MW CNRS solar furnace (France). The tube of high aspect ratio (more than 3 m height over 48 mm internal diameter) is irradiated along a 1-m height with several solar flux configurations that correspond to realistic operation conditions of a solar thermal power plant. The novelties of this paper lie in extending the operating parameters compared to earlier studies and in linking the fluidization regimes to wall heat transfer. Slugging, turbulent fluidization and fast fluidization regimes are detected within the receiver tube. It is shown that the system can tolerate high solar flux densities, up to 800 kW/m2. The system proves to be highly controllable and flexible with respect to particle mass flux variation and transient operations. Particle temperature increase ranges from 100 to 650 °C depending on the particle mass flux. Maximum thermal efficiency and particle outlet temperature of respectively ∼ 60 % and 680 °C are obtained, proving that this technology can be combined with highly efficient thermodynamic cycles. Global wall-to-particle heat transfer coefficient varies strongly with particle mass flux. It reaches a quasi-plateau above 15 kg/(m2s) with a mean value of 1000 ± 200 W/(m2K) and peaks data up to 1500 W/(m2K). A dimensionless heat transfer index is derived to account for the effects of the particle mass flux on the experimental results. It highlights that both increasing the temperature and working in the turbulent fluidization regime result in the increase of the heat transfer between the tube walls and the particles.

An improved SSA-BiLSTM-based short-term irradiance prediction model via sky images feature extraction

The development and utilization of solar energy has become an important strategic decision for the sustainable development of many countries. Short-term variations in solar irradiation have an impact on the safety and stability of photovoltaic and solar thermal power plants, therefore, the development and accuracy of solar irradiance prediction models have received much attention. This paper proposes a short-term irradiance prediction model based on mixed intelligent optimization algorithm and deep learning algorithm that integrates features of various forms of information. First, the sequence containing the picture attributes as well as the color and texture characteristics are recovered from ground-based cloud images, historical irradiance and meteorological feature information is decomposed and reconstructed by singular spectrum analysis (SSA). Secondly, the bidirectional short term to long term memory (BiLSTM) network is optimized for model training and finally assessment using an enhanced chaotic sparrow search method. The technique exceeds benchmark methods and a number of sophisticated individual algorithms in forecasting ultra-short-term global horizontal irradiance (GHI), according to experimental data, while also offering extremely high accuracy and resilience.

Self-adaptive heat extraction controller for solar thermal tower operational with molten salt tanks

Molten salts are commonly used in solar thermal power plants to store heat when sunlight is unavailable. However, solidifying the salts can lead to operational interruptions and prevent an optimal energy output. A self-adaptive heat extraction method has been proposed to regulate salt pipeline temperatures, enabling continuous operations that mitigate unplanned shut-downs. Such a method focuses on maintaining operational temperatures and preventing interferences caused by the freezing of the salts. The proposed Self-Adaptive Heat Extraction Controller (SAHEC) relies on fuzzy logic integrated into MATLAB Simulink to ensure optimal heat extraction control utilizing four distinct temperature variables. Modeling this approach through a created MATLAB-based simulation reveals that SAHEC offers an undeniable improvement over standard conventional methods for manipulating temperatures.

Optimal configuration of oblique air curtains for heat loss suppression from vertical solar-thermal receiver surfaces

An external solar-thermal receiver is critical to the operation of a solar-thermal power plant because it converts concentrated solar radiation into useful heat. However, as these receivers are surrounded by relatively cold air, they suffer from significant convective heat loss that is detrimental to their thermal performance. Air curtains, in the form of air jets directed obliquely from the top of the receiver surface, have been shown to provide significant local reductions in receiver heat loss. This study presents, for the first time, a rigorous optimisation of air curtain operation to increase the mitigation of overall convective heat loss. Two-dimensional computational fluid dynamics simulations in OpenFOAM were used to optimise jet speed, angle, position, and thickness. Performance was measured based on global effectiveness, with a maximum of over 18% achieved for a jet with speed Uac=5.5ms−1, angle α=45°, thickness b=30mm, and gap G=30mm. Increasing jet thickness yielded the greatest gains in overall effectiveness. An equivalent air curtain effectiveness was defined, with the optimal case having an effectiveness of around 14%. The effect of jet outlet temperatures on effectiveness was also examined, with effectiveness gradually decreasing with increasing jet outlet temperature.

Energy and Mass Matching Characteristics of the Heat-Absorbing Side of the Ammonia Energy Storage System under Nonuniform Energy Flow Density.

Ammonia thermochemical energy storage is based on a reversible reaction and realizes energy storage and utilization by absorbing and releasing heat. Under different energy flow densities, the efficiency of an ammonia reactor composed of multiple ammonia reaction tubes is different. Based on the coupling model of light, heat, and chemical energy of an ammonia decomposition reaction system, taking a 20 MW solar thermal power plant as the research object, this paper proposes a new model of ammonia energy storage system, which places the ammonia decomposition side in a low-pressure environment and the ammonia synthesis side in a high-pressure environment. The effects of different inlet temperatures, inlet flow rates, flow distribution, and energy flow density distribution on the ammonia energy storage system were studied. The results show that the increase of inlet temperature and the decrease of inlet flow rate are beneficial to the improvement of thermal efficiency and exergy efficiency of the system to a certain extent, but when the inlet temperature increases or the inlet flow rate decreases to a certain extent, the efficiency of the system will decline. Under the condition of nonuniform energy flow density and nonuniform inlet flow distribution, more ideal system thermal efficiency and exergy efficiency can be obtained.

Design and Fabrication of Hybrid Charging Station

A solar collector is a device that transforms solar radiation from the Sun into heat, which is then transferred to working fluid. The use of solar collectors reduces energy costs over time as they do not use fossil fuels or electricity like in traditional waterheating. As well as in domestic settings, a large number of these collectors can be combined in an array and used to generate electricity in solar thermal power plants. There are a number of different types of solar collector designs that use the energy of the sun to heat working fluid. Parabolic dish reflector provides a better alternative way in order to generate higher temperatures with better efficiency. The parabolic dish reflector is a solar energy collector designed to capture the sun’s direct solar radiation over a large surface area and focus or “concentrate it” onto a small focal point area, increasing the solar energy received by more than a factor of two. In the present project we will do the design & development of Parabolic Dish collector with automatic solar trackingfor water heating application. Keywords: Solar energy, water heating application, parabolic dish collector, automatic solar tracking.

Design analysis and performance prediction of packed bed latent heat storage system employing machine learning models

In recent years, the goal of becoming energy independent of fossil fuels has gained prominence. Solar energy is an excellent choice because it has a very less environmental impact in comparison to fossil fuels. The variability of solar radiation creates a divergence between energy demand and supply, making it necessary to implement efficient thermal energy storage systems to bridge the gap and enable solar thermal power plants to become viable solutions for uninterrupted power generation to meet the present and future energy needs. In this study, various data-driven machine learning (ML) models were used to analyze the design and performance of the packed-bed thermal energy storage (PBTES) system. Six different ML models, including linear regression (LR), support vector regression (SVR), K-nearest neighbors (KNN), decision trees (DT), random forests (RF), and extreme gradient boosting (XGB), were employed to evaluate the performance of PBTES. The models were trained and tested using experimental data reported in the literature on PBTES performance. The results of the study showed that the XGB ML model provided the best performance for PBTES analysis and prediction, with a maximum R2 value of 0.982, and minimum MAE, MAPE, and RMSE values of 0.057, 0.182, and 0.16, respectively. The study demonstrated the effectiveness of data-driven approaches in designing and analyzing PBTES performance, which can be useful for developing more efficient and sustainable energy systems. Overall, this study provides valuable insight into the potential of data-driven ML models for the design and performance analysis of PBTES, which could have significant implications for the utilization of renewable energy sources.

Frequency Control of a Realistic Dish Stirling Solar Thermal System and Accurate HVDC Models Using a Cascaded FOPI-IDDN-Based Crow Search Algorithm

Unbalancing the real power in power system leads to fluctuation in system frequency which can cause the several negative effects on the performance and reliability of the interconnected power system. Therefore, to deal with this, the load frequency control (LFC) of a three-area asymmetric thermal power system integrated with a solar thermal power plant (STPP), a realistic dish-stirling solar thermal system (DSTS), and an accurate high voltage direct current (HVDC) link are presented in this work. For the suggested system, a novel cascade controller called fractional-order proportional-integral and integral-double-derivative with filter (FOPI-IDDN) is designed. By minimising a newly proposed performance index called the HPA-ISE and adjusting the controller and other system model parameters using a metaheuristic method called the crow search algorithm (CS). When comparing the system dynamics, it was found that the suggested FOPI-IDDN controller outperformed the FOPI, PIDN, and FOPIDN controllers. The findings of this study show that HPA-ISE shows approximately 30% and 60% improvements in settling time (ST) and peak overshoots (POS) for frequency response, and 32% and 18% improvements for the tie power responses in terms of ST and POS over ISE criteria. Also, studies on different area capacity ratios have shown that a system connected to a greater capacity ratio operates better. The realistic DSTS system with fixed and recurring insolation in area 1 and area 2 outperforms the others, according to experiments using different DSTS insolation. Also, it is discovered that the parallel AC-AHVDC link study is superior to the AC and HVDC connection research. Moreover, it seems from the sensitivity study that the CS-optimized FOPI-IDDN controller improvements obtained under normal settings are consistent across a wide range of changes.

Simultaneous applications of fins and nanomaterials in phase change materials: A comprehensive review

Irregular nature of renewable energies namely solar and wind entails making use of storage units to improve the reliability of the designed systems and enhance the overall performance and output. In conditions of applying thermal energy technologies like solar thermal power plants and solar collectors, storage systems with ability of storing energy in thermal form are employed. In general, due to some advantages of latent heat thermal energy storage mainly known as Phase Change Material (PCM), like high heat capacity, these types of storage materials are widely used in thermal systems. In addition to energy storage, PCMs are utilizable for some other purposes namely device thermal management like solar PV/Thermal systems. In spite of benefits of PCMs in term of capacity of storage, low thermal conductivity is one the main disadvantages of them. Some techniques and approaches like utilization of nanomaterials, fins and foams are suggested to resolve this issue. The aim of current study is to review the research works on the simultaneous applications of fins and nanomaterials in PCMs. With respect to the findings of the research works it can be stated that there is significant potential in improvement of phase change rate by simultaneous usage of both fins and nanomaterials. The rate of phase change in these cases can be affected by the type of nanomaterials and the characteristics of the fins.

The Anomalous Reflection and Refraction of Metasurface in the View of Solar Concentrators

Solar thermal power generation integrates photothermal conversion power generation and low-cost, large-scale heat storage, which is the primary support for constructing a green power system with new energy as the main body. The concentrating system is a critical component of solar thermal power plants. However, traditional concentrators are bulky and require complex solar tracking systems, limiting the reduction of solar thermal power costs. The metasurface can freely regulate electromagnetic waves and can be used in the field of solar concentrators, making it suitable for developing lightweight, low-cost, tracking-free solar concentrators and being a transformative technological solution in the energy field. Considering that the solar position varies with respect to a fixed planar metasurface concentrator, in this paper, we investigate the anomalous reflection and refraction phenomenon on the metasurface when the incident plane is not parallel to the direction of the static phase gradient of the metasurface. Utilizing vector equation derivation, Matlab calculation, and full-wave simulation based on the Finite difference-time domain (FDTD) method, all found the new property of the metasurface: its refracted ray, reflected ray, and normal are in the same plane, which is called the exit plane, and is at a certain angle to the incident plane.

Advances in solar thermal power plants based on pressurised central receivers and supercritical power cycles

This work addresses the comparative thermo-economic study of different configurations of solar thermal power plants, based on supercritical power cycles and pressurised central receiver systems. For all the cases examined, two innovations are introduced in the solar subsystem, compared to other similar studies. Firstly, the heat transfer fluid in the receiver is either a pressurised gas or a supercritical fluid. Secondly, the receiver is composed of compact structures performing as absorber panels, arranged in a radial configuration. The investigation considers different supercritical CO2 recompression cycles of 50 MWe, including a novel proposal of a directly coupled cycle with heat input downstream of the turbine. Furthermore, the study evaluates different heat transfer fluids in the receiver, specifically CO2, N2, and He, concluding that the former is preferred due to its better thermal performance.The main results show that an increase in the receiver inlet pressure yields to a reduction in its size, favouring the thermal efficiency but penalising the optical efficiency of the solar field. Therefore, optimal working pressures may exist for each configuration, depending on the operating temperature. When comparing the optimal configurations, it is observed that the plant based on the intercooling cycle demonstrates the highest overall efficiency, reaching 32.05%. At last, an economic analysis is conducted to assess the viability of the identified optimal configurations. In this regard, the plant based on the partial-cooling cycle exhibits the lowest levelised cost of electricity at 0.15 $/kWh. This is primarily due to its lower investment cost. The innovative directly coupled cycle follows closely with a cost of 0.17 $/kWh, driven by its high electricity production resulting from its low self-consumption.