Search

Sustainable greenhouses have gained relevance in recent years due to their potential to reduce the carbon footprint of the agricultural sector by being integrated with renewable systems, contributing to the decarbonization of energy. Although solar technologies tend to be more accessible to cover the system's energy demands, greenhouses are subject to installation area restrictions, limiting their energy potential. This research evaluates the energy advantages of hybridizing solar thermal collector fields with photovoltaic module fields to cover a greenhouse's cooling and heating demands. For this purpose, the solar thermal field and the photovoltaic solar system were simulated with TRNSYS and MATLAB, respectively, while a method was developed to simulate the performance of a single-effect absorption chiller that was validated using the temperature measurements of a chiller in operation. The results show that the general method maintains differences between measurements and simulation smaller than 5 % with set temperatures between 5.5 and 12 degrees Celsius. The hybrid system, with an air-to-water chiller as the main machine and absorption chiller, reached a solar fraction of 0.85 and a fractional energy saving of 83 % . This represents a 27 % reduction in area concerning an individual solar thermal system. This research highlights that the solar hybrid configuration reduces fossil energy consumption by improving the global efficiency of energy conversion, thereby reducing the area of the solar field. [ABSTRACT FROM AUTHOR]

The latest generation of concentrated solar power (CSP) systems uses supercritical carbon dioxide (s-CO2) as the working fluid in a high-performance recompression Brayton cycle (RcBC), whose off-design performance under different environmental conditions has yet to be fully explored. This study presents a model developed using the Engineering Equation Solver (EES) and System Advisor Model (SAM) to evaluate the operation of two solar-driven s-CO2 RcBCs over a year, considering meteorological conditions in northern Chile. Under design conditions, the power plant outputs a net power of 25 M W with a first-law efficiency of 48.3%. An exergy analysis reveals that the high-temperature recuperator contributes the most to the exergy destruction under nominal conditions. However, the yearly simulation shows that the gas cooler's exergy destruction increases at high ambient temperatures, as does the turbine's during off-design operation. The proposed cycle widens the operational range, offering a higher flexibility and synergistic turndown strategy by throttling the mass flow. The proposed cycle's seasonal first-law efficiency of 39% outweighs the literature cycle's 29%. When coupled to a thermal energy storage system, the proposed cycle's capacity factor could reach 93.45%, compared to the value 76.45% reported for the cycle configuration taken from the literature. [ABSTRACT FROM AUTHOR]

Process heating is the activity with the most energy consumption in the industrial sector. Solar heating (SH) systems are a promising alternative to provide renewable thermal energy to industrial processes. However, factors such as high investment costs and area limitations in industrial facilities hinder their utilization; therefore, hybrid systems that combine two different solar thermal or photovoltaic technologies where each technology operates under conditions that allow a higher overall performance than conventional configurations have been proposed. In this review, we discuss the limitations of conventional SH systems and the potential of hybrid configurations to overcome them. First, the current literature about conventional and hybrid systems is presented. Then, the application of common performance indicators to evaluate hybrid configurations is analyzed. Finally, the limitation, advantages, and potential applications of conventional and hybrid systems are discussed. This work shows that conventional systems are the most promising alternatives in low and high-temperature industrial applications. At the same time, in medium and processes, hybrid configurations have great potential to increase the performance of SH systems and help to boost their adoption in the industrial sector. There are few studies about hybrid systems in industrial applications, and further research is required to determine their potential. [ABSTRACT FROM AUTHOR]

Industrial energy accounts for a large percentage of global consumption and, thus, it is a target for decarbonization by renewable and in particular solar energy adoption. Low uncertainty simulation tools can reduce the financial risk of solar projects, fostering the transition to a sustainable energy system. Several simulation tools are readily available to developers; differences exist in the format of input data and complexity of physical and numerical models. These tools can provide a variety of results from technical to financial and sensitivity analysis, often producing significant differences in yield assessment and uncertainty levels. IEA SHC Task 64/SolarPACES Task IV—Subtask C aims to address the lack of standard simulation tools for Solar Heating of Industrial Processes (SHIP) plants. This article describes the collaborative work developed by the researchers participating in the task. The identification and classification of several currently available simulation tools are performed on the basis of their capabilities and simulation approaches. A case study of solar heat supply to a copper mining operation is defined, allowing a comparison of the results produced by equivalent simulation tools. The proposed methodology identifies the main sources of differences among the simulation tools, the assessment of the deviation considering a series of statistical metrics for different time scales, and identifies their limitations and bias. The effects of physical characteristics of SHIP plants and different simulation approaches are discussed and quantified. The obtained results allow us to develop a basic guideline for a standardized yield assessment procedure with known uncertainties. Creating this common framework could partially reduce the risk perceived by the finance industry regarding SHIP systems. [ABSTRACT FROM AUTHOR]

Concentrated Solar Power (CSP) and geothermal energy systems are outlined as two of the most promising technologies for sustainable and reliable electricity generation. Several studies in the technical literature have pointed out that the hybridization of solar and geothermal energy sources could lead to a reduction of the levelized cost of energy (LCOE) of geothermal systems, as well as improving the capacity factor of CSP systems. However, the technical literature shows that the integration of solar thermal collectors does not present a positive impact in all scenarios analyzed. The present study aims to further analyze the competitiveness of the hybridization of solar and geothermal systems under high irradiation conditions such as those observed in the Andean region in northern Chile. The evaluation was carried out by coupling a thermodynamic model in Engineering Equation Solver (EES) with a solar thermal model in the System Advisor Model (SAM). The assessment considers the configuration of an existing geothermal plant, considering the design constraints associated with the actual operating conditions of the plant. The analysis is based on an energy and exergy assessment, allowing us to identify the efficiency of the subsystems introduced for the hybridization and assess the competitiveness of the hybrid schemes by an economic assessment in terms of the LCOE. The results show that the hybrid schemes allow a reduction of the LCOE of a geothermal stand-alone plant by about 10 USD / MWh , increasing the competitiveness of the geothermal system. However, a large variation on such a reduction is observed depending on the size of the solar field and the storage tank of the solar system. [ABSTRACT FROM AUTHOR]

Exergy is a thermodynamic property that represents the quantification of the maximum useful work that can be extracted from a system interacting with the environment. Regarding solar radiation, radiative exergy has been a matter of study over the last 60 years where the main models applied describe the radiation as undiluted and diluted. The exergy of solar radiation is useful in the preliminary assessment of the performance of solar technologies, since the efficiency of the system depends directly on this value. The present paper describes a review of the main models reported in the literature considering these two approaches, analysing the main differences between the models and the main assumptions applied. A comparative analysis is carried out for the models of diluted and undiluted radiation, where the behaviour of every expression is discussed in detail. For the undiluted expressions, the behaviour of every model within a temperature range is analysed. For black-body radiation at a source temperature of 6000 K, the model proposed by Jeter determines an exergy factor of 0.96, while Spanner, Petela, Press and Badescu calculate a value of 0.93. Parrott's model obtains a value of 0.99, which is above the value for Carnot efficiency. The diluted exergy expressions were evaluated according to wavelength and temperature range, where the trend in each comparison was that the exergy calculated from Karlsson, Candau and Petela was always the lowest. This result is attributed to the fact that these expressions consider the spectral entropy of the medium the radiation passes through. Finally, some new approaches are analysed which consider empirical correlations based on meteorological variables to model the exergy of solar radiation. [ABSTRACT FROM AUTHOR]

The trend to reduce CO2 emissions in cooling processes has made it possible to increase the alternatives for integrating solar energy with thermal equipment whose viability depends on its adaptation to polygeneration schemes. Despite the enormous potential offered by the industry for cooling and heating processes, solar cooling technologies (SCT) have been explored in a limited way in the industrial sector. This work discusses the potential applications of industrial SCTs and classifies hybrid polygeneration schemes based on supplying cold, heat, electricity, and desalination of water; summarizes the leading SCTs, and details the main indicators of polygeneration configurations in terms of reductions on primary energy consumption and payback times. To achieve an energy transition in refrigeration processes, the scenarios with the most significant potential are: the food manufacturing industry (water immersion and crystallization processes), the beverage industry (fermentation and storage processes), and the mining industry (underground air conditioning). [ABSTRACT FROM AUTHOR]

Solar energy is an economic and clean power source subject to natural variability, while energy storage might attenuate it, ultimately, effective and operationally feasible forecasting techniques for energy management are needed for better grid integration. This work presents a novel deterministic forecast method considering: irradiance pattern classification, Markov chains, fuzzy logic and an operational approach. The method developed was applied in a rolling manner for six years to a target location with no prior data to assess performance and its changes as new local data becomes available. Clearness index, diffuse fraction and irradiance hourly forecasts are analyzed on a yearly basis but also for 20 day types, and compared against smart persistence. Results show the proposed method outperforms smart persistence by ~10% for clearness index and diffuse fraction on the base case, but there are significant differences across the 20 day types analyzed, reaching up to +60% for clear days. Forecast lead time has the greatest impact in forecasting performance, which is important for any practical implementation. Seasonality in data gaps or rejected data can have a definite effect in performance assessment. A novel, comprehensive and detailed analysis framework was shown to present a better assessment of forecasters' performance. [ABSTRACT FROM AUTHOR]

Solar eclipses are astronomic phenomena in which the Earth's moon transits between the planet and the Sun, projecting a shadow onto the planet's surface. As solar power installed capacity increases, detailed studies of this region-wide phenomenon's effect in irradiance is of interest; however, the literature mainly reports its effects on localized scales. A measurement campaign spanning over 1400 km was pursued for the 2 July 2019 total solar eclipse in Chile, to register the event and establish a modeling framework to assess solar eclipse effects in irradiance over wide regional scales. This work describes the event and presents an estimation framework to decompose atmospheric and eclipse effects on irradiance. An analytical model was applied to study irradiance attenuation throughout the Chilean mainland territory, using satellite-derived and astronomical data as inputs compared to ground measurements in eight stations. Results showed good agreement between model and observations, with Mean Bias Errors of −0.008 to 0.98 W/m2 for Global Horizontal Irradiance and −0.004 to −4.664 W/m2 for Direct Normal Irradiance, with Normalized Root Mean Squared Errors of 0.7–5.8% and 1.4–12.2%, respectively. Energy losses due to obscuration corresponded between 20–40% for Global Horizontal Irradiance and 25–50% for Direct Normal Irradiance over Chilean territory. [ABSTRACT FROM AUTHOR]

The water–energy–food nexus has captured the attention of many researchers and policy makers for the potential synergies between those sectors, including the development of self-sustainable solutions for agriculture systems. This paper poses a novel design approach aimed at balancing the trade-off between the computational burden and accuracy of the results. The method is based on the combination of static energy hub models of the system components and rule-based control to simulate the operational costs over a one-year period as well as a global optimization algorithm that provides, from those results, a design that maximizes the solar energy contribution. The presented real-world case study is based on an isolated greenhouse, whose water needs are met due to a desalination facility, both acting as heat consumers, as well as a solar thermal field and a biomass boiler that cover the demand. Considering the Almerian climate and 1 ha of tomato crops with two growing seasons, the optimal design parameters were determined to be (with a solar fraction of 16% and a biomass fraction of 84%): 266 m 2 for the incident area of the solar field, 425 kWh for the thermal storage system, and 4234 kW for the biomass-generated power. The Levelized Cost of Heat (LCOH) values obtained for the solar field and biomass boiler were 0.035 and 0.078 €/kWh, respectively, and the discounted payback period also confirmed the profitability of the plant for fuel prices over 0.05 €/kWh. Thus, the proposed algorithm is useful as an innovative decision-making tool for farmers, for whom the burden of transitioning to sustainable farming systems might increase in the near future. [ABSTRACT FROM AUTHOR]

To identify the trends in new flexibility markets, a set of market and aggregator platforms were selected and compared. The analyzed initiatives are relevant to consider alternative designs for European electricity markets. This review proposes a common methodology for analyzing these market models by comparing their description, market structure, market timing, and implementation. Furthermore, a range of policy implications and future research directions towards implementing these markets are presented. The results provide compelling evidence that the new market models represent a promising business with technical and economic justification, as they incentivize the uptake of flexibility from distributed resources by providing services to Distribution System Operators (DSOs) in coordination with Transmission System Operators (TSOs). Moreover, the interactions between these new market platforms and existing markets are of particular interest, and the contributions from aggregator platforms are also relevant to enhance the political vision of empowering the customers through their active participation in markets. [ABSTRACT FROM AUTHOR]

A simplified mathematical model of parabolic-trough solar thermal power plants, which allow one to carry out an energetic characterization of the main thermal parameters that influence the solar field performance, was evaluated through a comparison of simulation results. Two geographical locations were selected to evaluate the mathematical model proposed in this work—one in each hemisphere—and design considerations according with the practical/operational experience were taken. Furthermore, independent simulations were performed using the System Advisor Model (SAM) software, their results were compared with those obtained by the simplified model. According with the above, the mathematical model allows one to carry out simulations with a high degree of flexibility and adaptability, in which the equations that allow the plant to be energetically characterized are composed of a series of logical conditions that help identify boundary conditions between dawn and sunset, direct normal irradiance transients, and when the thermal energy storage system must compensate the solar field energy deficits to maintain the full load operation of the plant. Due to the above, the developed model allows one to obtain satisfactory simulation results; referring to the net electric power production, this model provides results in both hemispheres with a relative percentage error in the range of [0.28–8.38%] compared with the results obtained with the SAM, with mean square values of 4.57% and 4.21% for sites 1 and 2, respectively. [ABSTRACT FROM AUTHOR]