Solar Plant Research Articles

5G as Communication Platform for Solar Tower Plants

Wiring of heliostat fields for solar tower plants is a cost factor that becomes more important as the overall cost target is decreasing. Wireless heliostats with radio communication and autarchic energy supply have therefore been proposed in the past. But none of the communication solutions investigated so far could realistically scale to commercial size plants with tens of thousands of heliostats. Moreover, the digitalization of CSP plants with numerous mobile and stationary sensor systems requires a suitable data communication, too. The new generation of mobile radio communication (5G) is capable of handling the heterogenous communication profile portfolio comprising large numbers of units with low data rates – like heliostats - and few units with very large data volume – like e.g. drone-based camera systems. The communication requirements of a typical solar tower installation are assessed in this work and a data traffic model is created for the most relevant communication channels. The various existing 5G implementations are assessed to find the most suitable solution. Different operator models for 5G are considered and their applicability in CSP target countries is discussed. A simulation test case is presented that models the radio communication traffic of a heliostat field control during a cloud passage. Finally, the experimental 5G campus network is introduced that is currently installed at the Solar Tower Jülich research plant and will be operated in the upcoming months to demonstrate the technical feasibility of 5G radio for communication in solar fields.

Transcritical Cycles With CO2-based Mixtures for CSP Applications: An Overview of the SCARABEUS Findings

This work summarizes the methodology developed within the H2020 EU project SCARABEUS for the analysis of innovative CO2-based mixtures used as working fluid in transcritical cycles for CSP applications. By adding a specific quantity of carefully selected dopant to CO2 it is possible to reach a high mixture critical temperature, suitable for air cooled cycles at very high minimum temperature in hot environments with high efficiencies. Along the methodology, some results related to the design of the turbine and the heat exchangers for the innovative mixtures are presented, including a focus on the system integration between the power block and the solar plant: as such, these results can be considered as interesting research outcomes to widen the knowledge on innovative solutions for efficient power cycles. The new power cycles are foreseen to drastically increase the profitability and cut the specific cost of CSP systems with respect to the state-of-the-art

Advanced Controllers for Heat Transfer Fluid Mass Flow Rate Control in Solar Tower Receivers

Efficient control strategies for managing the mass flow rate (MFR) of heat transfer fluids (HTF) during cloud transients in Solar Tower receivers play a pivotal role in optimizing plant profitability and receiver durability. This study focuses on the performance and durability of Solar Tower receivers during cloud transients. It evaluates adaptive feedback and feedforward control methods, which adjust the flow rate of heat transfer fluids based on real-time measurements of direct normal irradiance (DNI), receiver outlet and receiver panel outlet temperatures. The effectiveness of an aggressive all-sky and conservative clear-sky control strategy is explored against a conventional PI controller, emphasizing energy efficiency and receiver longevity. Simulations using a thermal Modelica model resembling a 100 MWel Crescent Dunes-like solar tower plant reveal that both advanced controllers provide precise setpoint tracking, while the PI controller struggles. The conservative controller which has a cloud standby mode prevents overheating during cloud transients by using a clear sky mass flow rate, while the aggressive controller uses the receiver panel outlet temperatures to correct for upstream tube temperature variations allowing for fast tracking correction and disturbance rejection, albeit with slight overshoots. Furthermore, the controllers significantly decrease the creep-fatigue damage accumulated in the receiver panels during cloudy days, due to limiting the increase in wall temperature spikes when cloud events end. Overall, this study underscores the pivotal role of HTF mass flow rate control systems in influencing receiver system failure modes and longevity and offers a new tool in controller design and operation assessment.

Development, Construction, Operation and Maintenance of Shouhang Dunhuang 100 MW Molten Salt Solar Power Tower Plant

The Shouhang Dunhuang 100 MW molten salt solar power tower plant is the first 100 MW-scale commercial demonstration project in China. The plant started to break ground in October 2016, was completed and connected to the grid for power generation in December 2018, and achieved full-load operation in June 2019. This paper comprehensively introduces the development, design, and construction process of the project as well as its operation and maintenance over the past five years, and shares experiences and lessons learned from the project.

Optimizing solar power efficiency in smart grids using hybrid machine learning models for accurate energy generation prediction

The fourth energy revolution is characterized by the incorporation of renewable energy supplies into intelligent networks. As the world is shifting towards cleaner energy sources, there is a need for efficient and reliable methods to predict the output of renewable energy plants. Hybrid machine learning modified models are emerging as a promising solution for energy generation prediction. Renewable energy generation plants, such as solar, biogas, hydropower plants, wind farms, etc. are becoming increasingly popular due to their environmental benefits. However, their output can be highly variable and dependent on weather conditions, making integrating them into the existing energy grid challenging. Smart grids with artificial intelligent systems have the potential to solve this challenge by using real-time data to optimize energy production and distribution. Although by incorporating sensors, analytics, and automation, these grids can manage energy demand and supply more efficiently, reducing carbon emissions, increase energy security, and improve access to electricity in remote areas. However, this research aims to enhance the efficiency of solar power generation systems in a smart grid context using machine learning hybrid models such as Hybrid Convolutional-Recurrence Net (HCRN), Hybrid Convolutional-LSTM Net (HCLN), and Hybrid Convolutional-GRU Net (HCGRN). For this purpose, this study considers various parameters of a solar plant such as power production (MWh), irradiance or plane of array (POA), and performance ratio (PR). The HCLN model demonstrates superior accuracy with the RMSE values of 0.012027 for MWh, 0.013734 for POA and 0.003055 for PR, along with the lowest MAE values of 0.069523 for MWh, 0.082813 for POA, and 0.042815 for PR. The obtained results suggest that the proposed machine learning models can effectively enhance the efficiency of solar power generation systems by accurately predicting the required measurements.

Hydro–Solar Hybrid Plant Operation in a Hydropower Plant Cascade: Optimizing Local and Bulk System Benefits

A hydro–solar hybrid system is an important solution for expanding renewable generation capacity under the percepts of the energy transition. This type of association allows for the coordinated dispatch of solar and hydropower plants, resulting in operational benefits in terms of energy generation and reservoir management, that is, the better use of available water and energy resources. As in this case, the operation of the hydropower plant is associated with the cascade in which it operates, when it is hybridized (for example, by associating with a solar power plant), in addition to local changes, there are impacts on the operating conditions of the other hydropower plants in the same cascade. From such a perspective, this study presents an energy system management model for hybrid power plants composed of hydro and solar sources, aiming to optimize the joint operation and measure the operational consequences at the local level and in the cascade. The results from a case study of a hydro–solar power plant hybridization in the Tietê River (Brazil) revealed increased energy production and improvement in the operating conditions of the cascade’s reservoirs, while the grid capacity was found to be an important constraint that limits the capture of synergies resulting from the generation sources complementarity and thus on the benefits to the cascade.

Scenario of solar energy and policies in India

Abstract Solar power is energy from the Sun that is converted into thermal or electrical energy. China, the USA, and India have the world’s richest solar energy sources. India receives solar radiation with an average intensity of 200 MW/km2 and 250–300 sunny days a year. The solar radiation in India varies from 4 to 7 kWh/m2/day, with 2300–3200 sunshine hours yearly, depending on the region. Badhla Solar Park, Jodhpur, India, is the world’s largest solar plant, with 2.25 GW of installed capacity. Solar energy is the best alternative electricity source used explicitly in the agricultural sector. In the farming sector, the consumption of solar energy has been increasing. The major issues were the installation costs, low availability of technicians, and poor quality of panels. The focus on skill development equips the workforce to drive innovation, efficiency, and sustained growth in the renewable-energy field. With the support of international collaboration and a skilled workforce, India’s progress in solar energy development is a boon for the industry.

Lifetime optimisation of integrated thermally and electrically driven solar desalination plants

We compare the performance of photovoltaic (PV), flat-plate and evacuated-tube solar-thermal (ST), and hybrid photovoltaic-thermal (PV-T) collectors to meet the energy demands of multi-effect distillation (MED) desalination plants across four locations. We consider three scales: 1700 m3day−1, 120 m3day−1 and 3 m3day−1. We find a strong dependence of the capacity and configuration of the solar collectors on both the cost of sourcing electricity from the grid and the specific collector employed. We find specific costs as low as 7.8, 3.4 and 3.7 USDm−3 for the three plant capacities. We find that solar-driven systems optimised for the lowest specific cost result in CO2eq emissions equal to, or higher than, those from grid-driven reverse osmosis (RO) and in line with PV-RO. This highlights the need to consider the environmental footprint of these systems to ensure that desalination is in line with the United Nations’ Sustainable Development Goal 6.

Energy, economic and environmental evaluation of the energy storage capabilities of artificial lakes based on pumped-hydro storage systems with a case study of Daghgoli artificial recreational lake

In the present study, Daghgoli artificial recreational lake has been investigated as an energy storage system. This lake with a capacity of 54,000 (m3) is located in the largest metropolis of northwestern Iran, above the Eynali Mountains, in the vicinity of the city. The elevation of this lake is about 450 (m) from the downstream lake with a capacity of 60,000 (m3). The energy storage capacity of the lake has been evaluated based on the pumped-hydro method. Then, the capacity of this large “battery” to store a part of the excess energy generated by the Tabriz thermal power plant has been evaluated. In addition to the technical evaluation, a full economic analysis as well as environmental investigation of application of the lake as an energy storage system has been conducted. The capacity that can be develop the existing small wind farm in the vicinity of the lake so that its generated energy can be fully stored by the energy storage system based on Daghgoli Lake has also been determined. Finally, the capacity of the photovoltaic solar power plant that can be established in the flat plain adjacent to the lake to store its generated electricity by the lake to be used at night or peak hours has been also evaluated. The results showed that using the presented energy storage plan, 74.7(MWh) of excess electrical energy generated by the thermal power plant can be stored daily. By releasing this energy during peak hours, 13.24 (MW) of electricity can be generated with an energy conversion efficiency about 71 %. At the same time, the emission of 8508 tons of carbon dioxide can be prevented during a year. The investment payback period of the project is estimated to be 4.7 years. By using the designed energy storage system, a wind farm consisting of 16 turbines with a capacity of 660 (kW) or a photovoltaic solar plant with a capacity of 9.34 (MW) can be created.

Enhancing Solar Photovoltaic Panel Performance in India's Tropical Climate: An Experimental Study on the Influential Effects of Optical Filters

<p>Due to the increasing global energy demand and consequent climate change from burning fossil fuels, researchers are getting more focused on renewable energies as a potential solution to the world's energy problems. Solar energy is a prominent form of sustainable energy. The solar photovoltaic power generation system’s electrical performance is negatively influenced by several factors, including the impact of solar irradiance, incident angle, temperature, dust accumulation on the top of the solar cell, cracks in the solar panel, shadowing, shunt resistance, solar cell materials, load mismatch, maintenance and cleaning schedule, spectral mismatch loss, and cable loss. The direct environmental factors that have the biggest impact on efficiency are the effects of sun irradiance and temperature. This empirical investigation examined the impact of optical filters on the electrical efficiency of a 40W polycrystalline solar PV panel in India while considering real-time ambient conditions. Through the utilization of an optical filter, the solar PV panel's temperature is diminished, hence enhancing the output power of the solar panel. Based on the experimental findings, the utilization of a transparent plexiglass sheet equipped with a coolant system installed on the solar panels leads to a drop in the average operating temperature of the solar PV module by up to 6°C. Additionally, the output power is enhanced by up to 10W in comparison to the reference solar panel’s output performance.</p>

Solar receiver endurance assessment under non-conventional operation modes

Central receiver endurance in solar power tower plants is a critical aspect to ensure their viability. In this work, two receiver configurations, with and without flow path crossover, are compared in thermal and mechanical performance. Considering their thermomechanical limits during operation, results show that panels in the crossover configuration would endure from 1.22 to 2 times that in the no-crossover, just marginally penalising its thermal efficiency. Additionally, two plant operation strategies are compared: continuous operation and nighttime strategy. The former results in 1.89-times more damage but roughly a 1.9-times increase in energy output, obtaining a practically constant trade-off between damage and energy generation for these two strategies. Lastly, the effect of considering either a linear or bilinear (interaction point set at 0.05,0.05) creep/fatigue damage interaction is explored. While producing more conservative results, linear interaction error is below 3 % in the most critical receiver regions. Such a low discrepancy is caused by the creep-damage dominance over fatigue in the most critical regions. Other areas show heavier creep-fatigue interaction, resulting in larger error, but these areas obtain times to failure much longer than expected receiver lifespan.

Addressing Data Scarcity in Solar Energy Prediction with Machine Learning and Augmentation Techniques

The accurate prediction of global horizontal irradiance (GHI) is crucial for optimizing solar power generation systems, particularly in mountainous areas with complex topography and unique microclimates. These regions face significant challenges due to limited reliable data and the dynamic nature of local weather conditions, which complicate accurate GHI measurement. The scarcity of precise data impedes the development of reliable solar energy prediction models, impacting both economic and environmental outcomes. To address these data scarcity challenges in solar energy prediction, this paper focuses on various locations in Europe and Asia Minor, predominantly in mountainous regions. Advanced machine learning techniques, including random forest (RF) and extreme gradient boosting (XGBoost) regressors, are employed to effectively predict GHI. Additionally, optimizing training data distribution based on cloud opacity values and integrating synthetic data significantly enhance predictive accuracy, with R2 scores ranging from 0.91 to 0.97 across multiple locations. Furthermore, substantial reductions in root mean square error (RMSE), mean absolute error (MAE), and mean bias error (MBE) underscore the improved reliability of the predictions. Future research should refine synthetic data generation, optimize additional meteorological and environmental parameter integration, extend methodology to new regions, and test for predicting global tilted irradiance (GTI). The studies should expand training data considerations beyond cloud opacity, incorporating sky cover and sunshine duration to enhance prediction accuracy and reliability.

Fault ride through enhancement of large‐scale solar plants using distributed converters

AbstractThe grid‐connected photovoltaic plants (GCPVPs) encounter various types of anomalies during fault occurrence in the main grid. During a fault occurrence on the grid side, the voltage of the point of common coupling (PCC) drops, causing the DC connection voltage to become too high for power balancing. This high DC voltage may damage the inverter and DC link equipment, which necessitates a reliable control scheme with low voltage passage requirements. These requirements, which obligate the GCPVP to remain connected to the main grid during abnormal conditions are generally known as low voltage ride‐through (LVRT). Herein, a developed LVRT method in the control approach that injects maximum rated current during a sag is proposed to rectify the shortcomings in single and multi‐inverter grid topologies. The proposed approach utilizes a current limiter combined with a DC braking chopper to guarantee the GCPVP's continuous participation in the power supply. Different scenarios including low and high power generations as well as two‐phase and three‐phase severe faults to the ground are considered. The results show that the proposed approach not only improves the performance in the single‐inverter system but also remedies the defects aggravated in the case of a GCPVP with several inverters.

Numerical analysis of the heat transfer performance of the absorber tube of a parabolic trough solar collector using the swirling flow technique

In the present work, the absorber tube of the DISS (Direct solar steam) solar plant in Plataforma Solar de Almeria (Spain) is powered by fluid flows in a swirl motion. Numerical simulations are used to predict the performance of a parabolic trough solar collector with inlets that allow the working fluid to flow in a swirl motion inside the absorber tube. There are numerous sites for tangential inlets distributed along the absorber tube. There is one inlet placed up, one located down, two located up, and two located down. High Reynolds numbers between 2.2 × 105 and 6.2 × 105 are used for the simulation. When the collector with the tangential inlet is compared to a conventional collector, the results reveal that using one inlet down causes a 9.1K decrease in the average temperature of the lower surface of the absorber tube. Compared to axial flow, one inlet down increases useful heat and heat transfer by 12.7 % and 41.7 %, respectively. The average friction factor of axial flow is 16.4 % higher than that of one inlet down. The collector with a tangential inlet reduces surface area by 10.9 % over Reynolds ranges when compared to an axial flow collector. Therefore, the thermal strain on the absorber tube and collector surface area is reduced by the swirling flow in the parabolic trough solar collector. As a helpful design tool, thermal performance correlations of absorber tubes with tangential inlets are constructed.

Assessment of suitability for photovoltaic power generation in periurban seminatural grasslands: toward the coexistence of seminatural grasslands and photovoltaic power generation

Renewable energy has grown substantially in recent years due to its efficacy in mitigating climate change. The rapid proliferation of solar photovoltaic (PV) systems and subsequent alterations in land use have led to concerns about the impact on local ecosystems. Particularly in Japan, seminatural grasslands, which are valuable habitats, are being developed as solar PVs. Here, we focused on stilt-mounted agrivoltaic systems, capable of both photovoltaic power generation and plant growth beneath solar panels. By repurposing this technology, the coexistence of vegetation and solar PV systems can be possibly ensured. To assess the feasibility of this proposed approach, we initially examined the suitability of installing solar PV in seminatural grasslands. The suitability of seminatural grasslands, solar PVs, and random points for solar PV was evaluated in terms of electricity generation and construction costs. The environmental conditions of seminatural grasslands were found to be advantageous for electricity generation. On the other hand, in terms of construction costs, seminatural grasslands were comparable to randomly selected sites. These findings indicate that the suitability of existing seminatural grasslands for solar PV plant installations is not considerably lower than that of other land types. The idea of reconciling solar power generation with ecosystem conservation holds promise and warrants further investigation toward its realization.

Analyzing the Feasibility of Photovoltaic Solar Systems in the Parking Area of Universitas Multimedia Nusantara: A PVSyst Simulation-based Investigation

The article explores the feasibility and economic viability of installing a solar power generation system at the rear parking area of Universitas Multimedia Nusantara (UMN). Utilizing PVSyst simulation, the study demonstrates that the proposed system can generate 224 MWh of electricity annually, meeting 20% of the energy needs for nearby buildings A and D. Despite requiring an initial investment of Rp. 781,883,953.26, the system proves financially sound with an NPV of Rp. 4,380,435,791 and an IRR of 34.28%. Moreover, the installation significantly reduces carbon emissions by 2775.513 tons. This research underscores the practicality and environmental benefits of adopting solar energy in university campuses.

Long-term complementary scheduling model of hydro-wind-solar under extreme drought weather conditions using an improved time-varying hedging rule

The frequent occurrence of extreme drought weather poses serious challenges to the complementary scheduling of renewable energy, including uncertain production processes, ineffective scheduling rules, and complex model solving, which further reduces the reliability of the power grid. To address these issues, a long-term complementary scheduling model of hydro-wind-solar (LCMHWS) considering hedging rules is proposed. First, to fully eliminate the uncertainty in monthly variables, Monte Carlo simulation and K-means clustering are sequentially absorbed into the model to process historical sequences and provide deterministic scenarios in which variable characteristics are conformed as input factors. Second, an improved time-varying hedging rule with strong drought resistance capability is proposed to optimize the complementary process of hydro-wind-solar and maximize the objectives of power generation and final energy storage. Last, NSGAII and membership function are adopted to search for the optimal Pareto solution for the uncertain multi-objective model. LCMHWS is validated for 7 hydropower and nearby wind and solar plants on the Lancang River in China. The results indicate that, while meeting the guaranteed output of the system, LCMHWS can increase the power generation and final energy storage by 14 % and 3 % under extreme drought conditions, respectively, and also smoothed the output process of power grid.

HelioPoint – A Fast Airborne Calibration Method for Heliostat Fields

Abstract The initial pointing calibration of a newly built heliostat field can take up to several years. The state-of-the-art method typically used is accurate but slow. A faster method could reduce the commissioning time and therefore increase the viability of a solar tower plant significantly. In this work, we present HelioPoint, a fast airborne heliostat calibration technique, and demonstrate its accuracy to be below 0.3 mrad. The measurement is performed using an LED and a camera fitted to a drone. The only infrastructure required are the roughly pre-aligned heliostats themselves. The method is independent of the sun position and can be performed at any time for arbitrary calibration points.

Assessing the Complementarity of Wind and Solar Energy in Kentucky

Recently, there has been a push by countries to diversify their energy mix considering various factors. In this regard, there have been several studies conducted to assess the potential for using sources such as wind and solar to generate supplemental energy to the already present energy generation setup. In this regard, this study explores the potential of wind for the Commonwealth of Kentucky. To perform this study, wind data were sourced for eight locations across Kentucky from the publicly accessible wind speed information present at Weather Underground for the years 2020–2021 (two years). An analysis was performed concerning the seasonal, monthly, and hourly variation in the wind speed so as to identify the expected times of sufficient wind energy generation. Moreover, a comparison of the collected data was performed with data from a home-based weather station as well as a deployed wind turbine to validate the variation pattern of the publicly sourced data. Finally, in order to investigate the variation patterns of wind and solar energy sources, a comparative analysis was also performed using data from a solar power generation plant in Kentucky. A seasonal and monthly complementarity was observed between the wind and solar energy. However, when considering daily patterns, the wind was found to follow solar generation with an offset. While further research is required, this analysis indicates that it is possible to deploy wind energy power generation projects in the Commonwealth of Kentucky. The seasonal complementary behavior of wind and solar energy can be used along with battery storage in conjunction with natural gas to provide a diversified electricity generation portfolio.

Unlocking the power of LiOH: Key to next-generation ultra-compact thermal energy storage systems

This study explores the potential of untapped lithium hydroxide (LiOH) as a phase change material for thermal energy storage. By overcoming the challenges associated with the liquid LiOH leakage, we successfully thermal-cycled LiOH in a laboratory scale experimentation, and observed its stability (>500 thermal cycles), without chemical decomposition. This step has never been performed to date. Its solid-to-liquid reversible transitions temperatures and related solidification/melting enthalpies values have been verified. Then, the first experimental characterization of LiOH's thermal properties shows unexpected values for its heat capacity, thermal conductivity and diffusivity, in contradiction with the few ones available in literature. This opens avenues for LiOH's applications for the storage of sensible and latent heat, as shown through the increased cycle efficiency potential of a thermal energy storage system if based on its energy storage capacity; up to six times more volumetric energy density compared to traditional Solar Salt-based systems used in the solar tower plant (4.5 GJ/m3 vs. 0.76 GJ/m3 over 1000 thermal cycles). Additionally, we observed a softening phenomenon that occurs inconsistently during heating, but which may account for its excellent melting properties and the interplay with other raw chemicals. This new insight contributes certainly to the underlying mechanisms in the synthesis of another promising heat storage material in development: the peritectic compound Li4Br(OH)3. This pioneering work suggests LiOH as a promising ultra-compact thermal energy storage material for filling the intermediary gap from current to next-generation solar power plants, although its large-scale application requires further investigation to achieve economic viability.