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In this work, an optimal algorithm-based integration of solar thermal energy with carbon capture and desalination processes were proposed. The stripper columns, identified as the most energy-consuming equipment, were designed with constant capacities to ensure practicality and applicability. Results show that, without affecting the power plant's efficiency, using a solvent tank as an energy storage system (scenario-2) increases total CO 2 capture from 45 % to 98 % compared to a part-time solar power system (scenario-1). Utilizing two solvent tanks reduces waste energy from 87 % to 67 % (scenario-3), while achieving 100 % CO 2 capture. Using three different stripper columns (scenario-4) lowers the levelized cost of energy by 20 %. Incorporating an additional multiple effect distillation system (scenario-5) reduces levelized cost of energy and energy loss by 26 % and 74 %, respectively. Approximately 28 % of the total solar energy collected (4.64 × 106 MWh) was used to capture 1.57 × 106 ton.year−1 of CO 2. The remaining energy was used in desalination to produce 9.4 × 106 m³.year−1 of fresh water, increasing overall energy efficiency from 28 % to 81 %, and reducing waste energy to 0.88 × 106 MWh, just 26 % of previous scenarios' waste. • Introducing reasonable integrations of solar energy, CO 2 capture, and desalination units. • Developing an optimal algorithm to maximize the CO 2 capture while minimize the energy loss. • The stripper columns were considered with practical and applicable design. • An effective energy storage system was designed based on a three stage solvent regeneration process. [ABSTRACT FROM AUTHOR]

Solar-powered adsorption chillers are a climate-friendly solution for building cooling, but costs and space requirements limit their widespread adoption. Recently developed adsorption cooling facade systems (ACFS) save installation space and further reduce CO 2 emissions. The performance of ACFS depends on the implemented adsorbent. To achieve low costs and high performance of ACFS, this study systematically screened and scored adsorbents using the analytic hierarchy process (AHP) method, focusing on price, stability, driving temperature and adsorption capacity. This method narrowed down 293 adsorbents to top 10 scored adsorbents including 4 silica gels, 4 active carbons and 2 molecular sieves. The adsorbent-specific performance is evaluated by numerical simulation, revealing silica gel Type A++, Type 2560, Siogel and molecular sieve AQSOA-FAM-Z02 have peak adsorber temperatures 1.5–9.3 °C lower and increase solar cooling efficiency (SCE) by 25–27 % compared to reference adsorbent Zeolite 13X. A sensitivity analysis of the Dubinin-Astakhov equation shows increasing E and decreasing V leads to an only minor adsorber temperature decrease and minor system efficiency increase. Lower temperatures and higher capacity cannot guarantee better system performance. This underscores that improving system performance cannot be achieved solely through adsorbent optimization but requires system optimization in parallel. • Systematic screening & rating of almost 300 potential adsorbents for solar cooling. • Simulation-based evaluation of top-ten promising adsorbents. • 4 adsorbents yield higher solar cooling efficiency and lower adsorber temperatures. • Sensitivity analysis on the adsorption isotherm show limited optimization potential. • Adsorbent optimization should be conducted in parallel with system optimization. [ABSTRACT FROM AUTHOR]

This study explores an innovative integration of solar energy with thermal energy storage for power production and cooling system support, utilizing phase change materials (PCMs) to enhance solar system performance, particularly for the cooling demands of an office building. The cooling load of a target office building in Ardabil City, Iran, is calculated for a typical day. Optimization is conducted using Multi-Objective Particle Swarm Optimization (MOPSO) to select the optimal zeotropic mixture as the working fluid, aimed at maximizing efficiency and minimizing heat source requirements. The system is designed to meet the needs of a two-story office building. Analysis of photovoltaic modules integrated with PCM under various parameters led to the selection of 25 PVT-PCM units in a series. The total setup includes 730 modules covering 365 m2, achieving a mass flow rate of 2.92 kg/s and supporting a 40 kW cooling load in the Ejector Refrigeration Cycle (ERC). The development of this solar-powered cooling system presents a sustainable, economically viable solution for building cooling. It demonstrates significant advancements in thermal efficiency through the strategic use of PCMs and optimized zeotropic mixtures in ejector refrigeration cycles. The system's scalable design offers a model for adapting to diverse climatic conditions, marking a notable contribution to sustainable building technologies. • A novel integration of an ejector refrigeration system with a PVT-PCM system is introduced. • The best zeotropic mixture as the working fluid of the ERC system to optimize its performance, is selected. • The building hourly cooling load is calculated utilizing CLTD/CLF methods, expanded in the ASHRAE. • The proposed system supports over 70% of cooling energy needs, even in periods of low sunlight. • In a series of 25 solar systems with a mass flow rate of 0.1 kg/s, the optimum thermal energy can be achieved. [ABSTRACT FROM AUTHOR]

This study examines the performance of a system that integrates solar collectors, a latent heat thermal energy storage system (LHTS) based on phase change material (PCM), and an organic Rankine cycle for power generation. Evacuated tube collectors with a total area of 212.4 m2 were utilized to harvest solar energy, and packed beds of encapsulated PCM, each with a nominal volume of 3.4 m³, were proposed as the LHTS. The integrated system maintains a nominal power generation target of 1.4 kW. Numerical models were verified and validated with data from similar systems found in the literature. Performance metrics, including net power generation, operating time, stored energy, and system efficiency, were evaluated under favorable conditions for a selected summer week, and under unfavorable conditions for a chosen winter week. The results indicate that the use of PCM can extend the system's operating time by 7–8 h during the summer week, and 5–6 h during the winter week, with a power output variation of up to 10 % throughout the central core of the operational period. Remarkably, the use of PCM allows this extension of operating hours with an efficiency reduction of up to 0.1 % irrespective of seasonal conditions. • An integration strategy for a low-temperature solar-ORC system is proposed. • Scenarios with and without Latent Heat Storage system are analyzed. • A packed bed of encapsulated PCM model is adopted as the energy storage system. • The operating time of the system could be extended by up to 8 h a day. • The use of LHTS yields minimal efficiency loss, irrespective of seasonal conditions. [ABSTRACT FROM AUTHOR]

The study of anisotropically thermal conductive phase change composites (PCCs) with shape-stability is of great importance to improve the intermittent issues in solar thermal utilization, while some drawbacks like the high cost, low thermal conductivity, and poor durability of current PCCs restrains their practical applications. Herein, a cheap and scalable biomass-based PCC containing carbonized sugarcane (CSC), polyethylene glycol (PEG), and graphene (GF) is proposed. The abundant vessels inside CSC result in a high PEG loading rate of 82.48 %. The naturally occurring anisotropic structure inside CSC can drive GF to be oriented along the lengthwise direction, which gives PCC a high thermal conductivity anisotropy degree of 1.45. The prominent anisotropy improves the lengthwise thermal diffusion and restrains the transverse heat leakage to the environment. Besides, the loaded GF can further enhance the light absorption of PCC to 98 %. As a result, the prepared PCC can achieve high solar-thermal energy storage efficiencies of 79.3–91.7 % with variable solar intensity from 1 to 2 suns. Meanwhile, good anti-leakage and durability performances promote the practical utilization of PCCs. The present work paves a promising road for manufacturing biomass-based anisotropic PCCs in efficient solar thermal energy storage. • A novel biomass-based PCC with anisotropic structures was fabricated. • The PCC has excellent directional heat conduction and storage performance. • An ultra-high loading capacity was achieved owing to the vessels in sugarcane. • Solar thermal energy storage efficiency of 91.7 % are achieved under 2 suns. [ABSTRACT FROM AUTHOR]

The utilization of solar drying technologies has gained increasing importance in the context of sustainable and energy-efficient processes. This exploration delves into current trends in solar drying, specifically focusing on materials, designs, and their integration with energy storage solutions. Within the materials domain, we examine solar collectors, absorbers, and the impactful role of phase change materials (PCMs) in augmenting drying efficiency. Innovative designs and configurations are discussed, offering insights into advanced solar drying systems. Furthermore, the integration of energy storage technologies is highlighted, critical role of energy management in solar drying applications is emphasized. The assessment encompasses performance and efficiency enhancements, including mathematical modeling and the optimization of heat transfer processes. Challenges and potential future directions in solar drying are explored, along with the promising areas for ongoing research. The object is to provide a comprehensive perspective on the recent advancements in solar drying, offering valuable insights for sustainable practices and future developments. • Overview of solar drying technologies: open sun drying, direct drying, and indirect drying, recent advancements and key findings. • In-depth discussion on materials used in solar drying, focusing on collectors and performance-enhancing components. • Overview of phase change materials (PCMs) for thermal energy storage in solar dryers, emphasizing recent studies and applications. • Evaluation of solar dryers performance, environmental impacts, and policy drivers, highlighting technological advancements and recent UN-driven policies. • Overview of mathematical models and simulations: heat and mass transfer models, collector models, product quality, and computational fluid dynamics (CFD) applications. [ABSTRACT FROM AUTHOR]

Solar aided coal-fired power generation technologies have proven to be effective in reducing fossil fuel consumption and greenhouse gas emission. In this research, a high-proportion solar tower aided coal-fired power generation system integrated with thermal energy storage system is proposed. According to the constraint conditions, the integration scheme with the highest solar coupling capacity is obtained, and its thermodynamic, economic and environmental performances are researched. The results indicate that the solar coupling capacity that can be accommodated by the 660 MW coal-fired unit after parameter optimization is 339.532 MW th. As the load rate decreases, the power generated from solar and solar to electricity efficiency gradually decreases while the proportion of power from solar increases. The proportion of power from solar reaches a maximum of 24.28 % at 50 % load rate. The effects of different thermal energy storage hours on the levelized cost of electricity are investigated, and the results show that the lowest levelized cost of electricity is only 41.62 $/MWh in the high-level direct normal irradiance area. The new system can reduce about 272,921 tons of CO 2 emissions in a year at 100 % load rate. This study contributes to further promoting the development of a high-proportion solar aided coal-fired power generation system and realizing the low-carbon transition of coal-fired power generation industry. • A high proportion solar tower aided coal-fired power generation system is proposed. • Decisive parameters of new system are analyzed with respect to safety constraints. • The maximum solar coupling capacity after parameters optimization is 329.532MW th. • The maximum solar power proportion of new system is 24.28 % at 50 % load rate. • New system can reduce 272,921 tons of CO 2 emissions in a year at 100 % load rate. [ABSTRACT FROM AUTHOR]

Globally, the efficient utilization of solar energy has garnered significant attention. A hybrid system of photovoltaic/thermal (PV/T) modules integrated with thermally regenerative electrochemical cycle (TREC), i.e., PV/T-TREC has emerged recently and shows higher efficiency for solar-to-electrical conversion than a standalone PV system. However, there is a trade-off between the electricity generation from PV/T and TREC because the thermal energy from PV/T degrades the efficiency of the PV/T but improves that of TREC. Previous studies have failed to investigate this problem. This study therefore focuses on the key parameters that significantly affect the thermal output of PV/T, i.e., different PV materials, air gaps, heat storage tank volumes, and working fluids to investigate the maximum electrical efficiency of the hybrid system. The mathematical and transient-state numerical models are developed with the validation/refinement from the experiments. The results show that the hybrid system with PV material of cadmium telluride presents the best overall electrical efficiency of 25.37 %. The case of the air gap fosters the solar-to-electrical conversion. The electrical efficiency versus heat storage tank volume shows a convex curve, peaking at 200 L. The nanofluid performs the best. This study may help guide the practical application of such a high-efficiency electricity generation system. • Optimization of hybrid PV/T-TREC system is performed. • A comprehensive transient-state model is developed. • Thermal output-related factors are analyzed. • Useful suggestions are made for its practical applications. [ABSTRACT FROM AUTHOR]

Although utilizing phase change materials (PCMs) for thermal energy storage and management has remarkably grown, the reliance on petroleum-based PCMs has raised concerns about their sustainability. Hence, in this study, the mixture of beeswax (BW) and coconut oil (CO) as a new biological-based PCM (bio-PCM) was developed. Also, the effect of 0.5, 1, and 2 wt% of graphene-copper (Gr-Cu) hybrid nanoparticles on the bio-PCM's ability in thermal energy storage (TES) was scrutinized. Thermal, chemical, physical, and stability specifications of BW-CO/Gr-Cu nano- and bio-based PCMs (bio-nPCMs) were examined by Differential Scanning Calorimeter (DSC), Fourier Transform Infrared Spectroscopy (FTIR), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). Also, the thermal conductivity of bio-PCM and bio-nPCMs were explored in a range of temperatures from 25 to 60 °C. FTIR indicated no chemical reactions or new synthesis materials in the final composite. Also, all the used materials were recognized by XRD. DSC analysis showed that melting and solidification of bio-PCM start at 51 and 56 °C while adding 2 wt% Gr-Cu nanoparticles reduced the temperatures to 49.9 °C and 53.8 °C, respectively. In addition, bio-PCM had latent heats of 172.3 kJ/kg and 173.11 kJ/kg for melting and solidification, whereas 2 wt% Gr-Cu nanoparticles shifted them to 160.75 kJ/kg and 167.45 kJ/kg, in respect. On the other hand, the higher the concentration of Gr-Cu in the base PCM, the higher the thermal conductivity of bio-nPCMs maximally about 604 % higher than that of the base bio-PCM at T = 25 °C. Furthermore, a new model was proposed for the thermal conductivity that had an average error of 5 %. Machine learning was employed to estimate the thermal conductivity and latent heat. The former with R-squared, mean error (MSE), and average absolute relative deviation (%AARD) of 0.9996, 1.1253 × 10−4, 1.871, and the latter with 1, 4.7 × 10−10, and 0.01, respectively. The outcomes of this study present a procedure to develop future bio-PCMs and hybrid nanoparticles to pave the way to reaching net-zero carbon. [Display omitted] • Developing a new bio-PCM for a decent alternative to petroleum-based paraffin. • Achieving 604 % higher thermal conductivity by adding Gr-Cu hybrid nanoparticles. • Obtaining melting and solidification latent heat of 172.3 kJ/kg and 173.11 kJ/kg. • Proposing a new temperature-and-concentration-based model for thermal conductivity. • High-accuracy prediction of thermal conductivity and latent heat utilizing ANN-MLP. [ABSTRACT FROM AUTHOR]

Solar–coal hybrid power generation achieves the production of efficient, clean, and low-carbon electricity. The association between solar heat and selective catalytic reduction NO x removal (SCR de-NO x) can lead to the development of a novel solar-aided NO x removal system for peaking power plants. In this study, a novel system was proposed, in which large amount of flat-plate and small amount of trough solar energies were integrated to optimise the SCR de-NO x and energy utilisation in the boiler tail. Thermodynamic, NO x removal, and economic analyses were performed. For a typical peaking unit, the proposed system produced 14.6 MW e of solar-generated electric power and exhibited a high solar-to-electricity efficiency of 30.15 %. The integrated solar heat significantly increased the SCR de-NO x temperature and NO x removal efficiency. Based on its outstanding solar conversion performance, the proposed system achieved a net annual benefit (NAB) of 24.01 million Chinese yuan (CNY) and maintained a low cost of solar-generated electricity (COE s) of 0.56 CNY/kWh. Based on cascade utilisation of solar thermal energy, the proposed system achieved high performance under all loads and significantly improved the NO x removal performance under low and medium loads, especially for peaking power plants. [Display omitted] • Close connections between solar thermal energy and SCR de-NO x are revealed. • Large amount of flat plate solar energy is integrated for SCR de-NO x optimisation. • A little trough solar heat is used for accurate SCR de-NO x temperature control. • High thermal, NO x removal, and economic performances are achieved. [ABSTRACT FROM AUTHOR]

Seasonal thermal energy storage (STES) offers an attractive option for decarbonizing heating in the built environment to promote renewable energy and reduce CO 2 emissions. A literature review revealed knowledge gaps in evaluating the technical feasibility of replacing district heating (DH) with STES in densely populated areas and its impact on costs, fossil fuel consumption, CO 2 emission reduction, and renewable power integration. The effects of large-scale STES applications on the power and DH sectors in a regional energy system were quantified by applying the 2030 and 2050 power structure scenarios. The results indicated that STES reduces fossil fuel consumption and CO 2 emissions at an affordable cost. It facilitates the integration of wind and solar power into power grids. With 100 % replacement of DH by STES, fossil fuel consumption and CO 2 emissions can be reduced by approximately 40 % and 45 % in 2030 and 2050, respectively, with an annual cost increase of 20 %. The CO 2 avoidance costs were predicted to be approximately 60 €/t in 2030 and well below 50 €/t in 2050. STES will reduce renewable power curtailment by 10 % in 2030 and 18 % in 2050. This study investigated STES from an energy-system perspective, supporting the formulation of clean heating transition policies. • The effects of STES on the power and district heating sectors were quantified. • The optimal combination of solar and wind power capacities was calculated. • STES can reduce fossil fuel consumption and CO 2 emissions at an affordable cost. • STES promotes renewable power integration with a reduction in the curtailment of renewables. • With more renewables in the grid, the benefits of replacing district heating with STES increase. [ABSTRACT FROM AUTHOR]

Conversion of sunlight to heat and the subsequent thermal storage by nanoencapsulated bio-based phase change material slurries (NBPCMSs) in a low temperature solar system is investigated. The influences of capsule size, shell material, tilt angle, solar heat flux, PCM mass concentration, nanoparticle and its concentration are explored. The results reveal that the useful heat gain capacity of nano-enhanced coconut oil/Ag, coconut oil/Au, coconut oil/Al, and coconut oil/Cu based slurries is respectively 3.02, 3.12, 2.7, and 3.14 times better than that of pure water, due to an enhanced interaction of light with the functional bio-based PCM nanocapsules. Consequently, the thermal energy storage is reported to be 8.85, 9.29, 7.41, and 9.19 times higher. The increment in mass concentration of PCM from 5 to 20 % and addition of blended nanoparticles further augment the solar thermal energy storage capacity. Specifically, the storage capacity of coconut oil/Au based slurry is improved by up to 74.4 % when the 20 % coconout oil is used as a core material. The energy storage improvements of Cu and Ag based slurries enhance by 4.04 and 4.87 %, respectively, with the insertion of Au nanoparticles at a volume fraction of 25 ppm. Augmenting the core/shell confinement size, on the other hand, diminishes the surface area to volume ratio, allowing agglomeration of the structures inside the slurry. The performance of solar energy storage decreases as the inclination angle of the storage cavity increases from 0° to 60°, reducing the buoyancy force and particles' collision. Further, since Al particles have low optical characteristics and thermal conductivity, the thermal performance of coconut oil/Al nanoencapsulated slurry are at the lowest level. Finally, experiment is conducted to validate the specific heat capacity model prediction under various wind speeds, from 1 to 4 m/s, and solar illuminations, from 400 to 1000 W/m2. • A nanoencapsulated bio-based phase change material slurry-based solar system is analysed. • Nanocapsules enhance conversion of sunlight to heat and thermal storage. • Melting fraction of coconut oil is affected by wind speed and radiation. • Inclination angle lessens conversion thus storage capacity. • Metallic shells due to radiation-matter interaction augment solar capture. [ABSTRACT FROM AUTHOR]

Solar photovoltaic thermal system (SPTS) can fully tap solar energy resources to realize thermal and electric supply for users simultaneously, but the volatility and uncertainty of renewable energy and load cause the imbalance of energy supply. This paper proposes a multi-time scale optimal scheduling method for SPTS based on event-triggered model predictive control (ET-MPC) considering battery performance deterioration. Firstly, SPTS is divided into day-ahead and day-in optimization layers from different time scales. Day-ahead scheduling takes the minimization economic cost as the optimization function to obtain pre-scheduling plan, and day-in scheduling adapts rolling optimization scheme based on model predictive control (MPC) to reduce power fluctuations and achieve optimal scheduling adjustment. Moreover, the battery performance decay parameter is introduced into the MPC model and embedded into the optimization problem to prolong the cyclic life deterioration, and an event-triggered mechanism is introduced into MPC to improve the computational efficiency and reduce the communication frequency. Finally, the results show that the proposed double-layer scheduling method improves 4.15 %, 66 % and 13.39 % respectively regarding cost, power fluctuation and battery maintenance, and improve the calculation efficiency of 48.89 % compared with standard MPC method, which indicates that the proposed method has good economy, stability and execution efficiency. • This paper proposed energy scheduling for solar photovoltaic thermal system (SPTS). • Double-layer optimal scheduling is proposed to realize the economy and stability. • Battery service time is prolonged through defining performance index. • An event-triggered mechanism is introduced to MPC to reduce the communication burden. • The proposed method improves performance from different perspectives. [ABSTRACT FROM AUTHOR]

Latent heat thermal energy storage based on phase change materials (PCM) is considered to be an effective method to solve the contradiction between solar energy supply and demand in time and space. The development of PCM composites with high solar energy absorption efficiency and high energy storage density is the key to solar thermal storage technology. In this paper, a green and simple method is proposed to fabricate a porous PCM with stable shape, low supercooling degree and excellent photo-thermal conversion performance. The novel PCM which combine porous expanded graphite as the carrier material, n-eicosane as the stabilizer and sodium acetate trihydrate (SAT) as phase change energy storage material are designed and prepared by melt blending method. The expanded graphite contributes to the stable shape of the composites, and provides excellent thermal conductivity channels and light absorption properties as well. The composite PCM sample containing 3.3 wt% expanded graphite achieves excellent performance, phase change enthalpy of 266.54 J/g and a photothermal conversion efficiency of 91.14 %, and shows low supercooling degree of 2.2 °C with almost no leakage at 90 °C. [Display omitted] • A porous PCM with excellent photo-thermal conversion performance was fabricated. • The novel PCM combines porous EG, n-eicosane and SAT. • Phase change enthalpy of 266.5 J/g and supercooling degree of 2.2 °C were achieved. [ABSTRACT FROM AUTHOR]

The paper presents a post-combustion CO 2 capture process which involves two configurations for enhancing the CO 2 separation driving force in the conventional amine-based Carbon Capture System (CCS): a multi-stage membrane module for selective exhaust gas recirculation (SEGR case) and the combination of turbine exhaust gas recirculation with SEGR (EGR + SEGR case). Furthermore, the stripper reboiler in both configurations is integrated with a parabolic trough solar collector field with a 4-h thermal energy storage to provide the required thermal duty for solvent regeneration. Various system components are designed, simulated, and integrated with an economic model to evaluate the system's techno-economic performance across a wide range of loads. The results show that the proposed designs have efficient part-load performance although efficiency degradation is inevitable during partial-loads. A stable supply of solar thermal energy results during the partial operation of NGCC even during night. The EGR + SEGR case represents the case with the lowest levelized cost of electricity and CO 2 avoided cost, 81.43 $/MWh and 101.66 $/tonneCO 2 , among the CCS-equipped designs, which highlight the advantages of this design over baseline and SEGR case. The proposed hybrid system shows promise for significantly decarbonizing fossil-fuel power plants and increasing power sector flexibility. • Economic and part-load performance of a novel CO 2 capture design are analyzed. • The hybrid CCS process is integrated with solar collectors and energy storage. • The process has the LCOE and CO 2 avoided cost of 81.43 $/MWh and 101.66 $/tCO 2. • The proposed design shows an acceptable and flexible part load operation. [ABSTRACT FROM AUTHOR]

In winter, greenhouses located in mid to high latitudes are required a function of dehumidification and warming due to the low outdoor temperature. Focusing on small spires greenhouses, this study regulates the low temperature and high humidity environment inside the greenhouse and proposes a new-type of greenhouse heat and humidity regulation system by combining composite solid desiccant dehumidification with ground heat exchange system. The greenhouse internal environment is warmed and dehumidified at night by utilizing the adsorption effect of the compound dehumidifier and the sensible heat exchange between the heat exchange system in the ground and the greenhouse. Solar thermal energy is collected during the day using multi-curved tank collector (MTC) for thermal storage in the geothermal system and desiccant desorption. The rationality of pipeline layout is verified through CFD simulation, and the indoor temperature and humidity distribution during the system operation is explored. The experimental results show that the moisture adsorption capacity of the composite desiccant SG-CaCl 2 for 10h is 0.511 g/g. The optimal regeneration temperature is 80–100 °C. This system can reduce the nighttime relative humidity of the greenhouse in winter from 96.5 % to 83.6 %, and the average indoor air temperature after warming is 12.8 °C. The heat exchange efficiency of the underground heating exchange system is 0.38. During the desorption phase on daytime, the maximum outlet temperature of MTC is 103.8 °C, and the average heat collection efficiency is 0.42. The system can effectively regulate the air environment in the greenhouse to the appropriate zone for crop growth by combining solar thermal collector technology with recyclable solid dehumidification technology. • A novel heat and humidity control system of solar greenhouse with composite desiccants was proposed. • The performance of the system is analyzed in detail through experiments and simulations. • The moisture adsorption capacity of the composite desiccant SG-CaCl 2 for 10h is 0.511 g/g. • This system can reduce the nighttime relative humidity of the greenhouse in winter from 96.5 % to 83.6 %. [ABSTRACT FROM AUTHOR]

With the advantages of low heat storage temperature, high heat storage density, and a low price, Na 3 PO 4 has been proposed as a thermochemical heat storage candidate material for use in solar low-temperature heat storage engineering applications. However, the application of pure Na 3 PO 4 is limited due to its propensity for agglomeration. In this study, activated carbon-based Na 3 PO 4 (R-AC@Na 3 PO 4) composites with mass fractions of 30 %, 50 %, and 80 % were synthesized by melt impregnation method using activated carbon as the porous matrix. The morphology and structure of the composites were characterized, and their heat storage performances were investigated. The hydration experiments were carried out in a constant temperature and humidity chamber and dehydration experiments were carried out in thermogravimetric analysis and differential scanning calorimetry simultaneously. The results showed that at 30 °C, 60 % relative humidity, the hydration equilibrium time for the composites were only 30 %–40 % of the pure material. Meanwhile, at a mass fraction of 80 %, material's volumetric heat storage can reach 1793 J·cm−3 without agglomeration, and the performance was stable after 20 cyclic tests. This study provides a reference for the research and development of low-temperature thermochemical heat storage materials and offers more possibilities for R-AC@Na 3 PO 4 composites in future engineering applications. [Display omitted] • First successful preparation of AC@Na 3 PO 4 composites for low-temperature chemical heat storage by melt impregnation. • The composite material has the advantage of high heat storage density and low cost in low temperature applications. • After 20 cycles, the composite material performance is stable. [ABSTRACT FROM AUTHOR]

To promote the continuous operating of solar energy systems and increase the proportion of renewable energy consumption, solar devices are often integrated with conventional energy systems to reduce greenhouse gas emissions. In this study, a solar-natural gas coupling system is constructed, utilizing solar photovoltaics, thermal collectors, and high-efficiency energy conversion devices. After modelling the energy system, the operating modes are illustrated considering working sequences of water-cooled devices. A modified genetic algorithm, which incorporates reverse learning, controlled elite, and dynamic crowding distance theory, is constructed to optimize the configurations of the proposed energy system, with the aim of minimizing carbon and economic prices of the products. The performance of the energy system is compared with different algorithms and cases, and the results demonstrate that the proposed algorithm addresses the limitations of conventional methods, albeit with increased optimization times. Moreover, the proposed operating mode (Case 1) exhibits a stable performance, leading to a higher environmental and economic performance compared to conventional modes, with carbon and economic prices of 0.242 kg/kWh and 0.067 $/kWh, respectively. This study provides new insights into carbon footprints and economic performance evaluation of high-efficiency energy systems, offering valuable directions for future research in this field. [Display omitted] • A solar-natural gas coupling system to fulfill building multiple demands. • Comparisons of fours cases considering operating sequences of two types of chillers. • Modified genetic algorithm using reverse learning, elite controlled, dynamic crowding distance theory. • Carbon and economic prices of the products are illustrated. [ABSTRACT FROM AUTHOR]

The high proportion and volatility of renewable energy pose a significant challenge to efficient collaboration between photovoltaic/thermal and wind power in multi-energy systems. Therefore, this paper proposes a Regional Multi-Energy System (RMES) based on Medium-High Temperature Solar Thermal (MHTST) technology. The novelty of the solution integrates dispatchable photovoltaic and photothermal conversion pathways, facilitating flexible and controllable utilization of solar energy via installed Thermal Energy Storage (TES). A multi-objective optimization model is developed to ensure the optimal operation of the proposed system under typical seasonal scenarios. The method that combines Branch-and-Reduce with Multi-Learning-Task is used to handle the formulated Mixed Integer Nonlinear Programming (MINLP) and swiftly identify optimal Pareto solutions. Case studies are performed over the improved united communities of the Test Region for Energy Transition and Comprehensive Reform in Taiyuan, China. Compared with the conventional photovoltaic technology, the simulation results show that the proposed solution has superior performance in both winter-heating and summer-cooling operations across 24-hour scheduling periods: operating costs reduced by 12.5% and 18.7%, carbon emissions decreased by 7.4% and 21.4%, with local solar power accommodation increased by 263.89kW and 487.47kW, respectively. • A novel regional multi-energy system integrating medium-high temperature solar thermal is proposed. • The model solution combined branch-and-reduce with multi-learning-task is proposed. • The proposed strategy offers optimal energy schedules while reflecting renewable electricity trading. • System performances of photovoltaic and medium-high temperature solar thermal systems are compared. [ABSTRACT FROM AUTHOR]

The solar-coal energy complementary technology is an effective way to use solar energy for power generation. In this work, a 330 MW coal-fired power generation unit, with an integrated solar field system, was studied to improve solar energy utilization efficiency and control performance. The dynamic mathematical model of the system was established using a lumped parameter method; the maximum relative error was found to be less than 5 %. Different coupling methods for the solar thermal system and coal-fired power unit were studied, and the dynamic characteristics of the unit under different solar radiation intensities were obtained. Finally, a coordinated control system was proposed based on the multiscale decomposition of load commands. The results show that the new coordinated control system showed more flexibility and less fluctuation of power during regulation. It has the best control effect, with the integral of the absolute value of the error criterion reaching 890.8 and 795 in step and slope experiments, respectively, and the integral of time multiplied by the squared error criterion reaching 4.172 × 105 and 3.043 × 105, respectively. This study successfully demonstrates the effective use of solar-coal energy complementary technology and provides an important reference for future work. • The system performances at different solar irradiation levels are studied. • Analyzed the dynamic characteristics of the system under different coupling methods. • Method 3 has the fastest climbing speed. • The proposed control method is superior to the traditional methods. [ABSTRACT FROM AUTHOR]

With increasing volatility in natural gas markets and the need for residential heat, research for alternative thermal systems based on green hydrogen-based fuels is necessary. Massive implementation of hydrogen in the current fleet presents a challenge for the decarbonisation of conventional thermal processes. This paper presents the integration of green methanol from a seasonal thermochemical energy storage system (TCES) coupled with district heating networks (DHN). It allows for a solar-based storage and low-temperature heat generation from the exothermic discharge reaction. The system uses concentrated solar thermal energy to decompose methanol into syngas at moderate temperatures (<315 °C), reducing GHG emissions from combustion to meet residential heat. Its potential is assessed through an analysis of 458 rural municipalities in Spain, achieving a substitution of 3.1 % of the natural gas demand. The system allows the production of green fuels from syngas using an open-loop approach, offering new market pathways in primary sector. In a closed-loop configuration, roundtrip efficiencies exceeding 60 % and chemical conversion efficiencies exceeding 70 % are reached, resulting in a global efficiency of 12 % for the DHN and methanol-TCES. The results show a levelized cost of stored energy highly competitive with other storage systems (<200€/MWh), given its simplicity. • A novel district heating network integration with methanol TCES is proposed. • Round-trip above 65 % and an overall efficiency of 11.6 % were achieved. • Analysis of presented DH-TCES in 499 rural municipalities in Spain. • Competitive levelized storage price values of €150/MWh was obtained. [ABSTRACT FROM AUTHOR]

Solar thermal energy usage in the Baltic countries is currently low, so there is a need to find technically and economically feasible solutions to increase the appeal of this technology. Integration of solar energy into existing district heating systems is a way to increase the share of renewable energy sources while utilizing the existing infrastructure, thereby reducing capital investments, as well as mitigating the risk of solar collector overheating and eliminating the need for local storage tanks in buildings. This study presents a parametric study for evaluating the effectiveness of using a district heating system to store heat produced by decentralized solar thermal collectors and comparing the district solution to the traditional local solution. The TRNSYS 18 model was developed for this purpose. The model investigates the impact of different hot tap water demand profiles as well as pipeline diameters and lengths on system energy efficiency, showing a statistically significant difference (p < 0.05) between installing solar collectors on residential and restaurant or office roofs, and no significant difference (p = 0.24) between restaurant and office. The model shows that solar energy can be shared within a 500 m distance between neighborhoods and that a larger main pipeline diameter can increase overall system efficiency. • Evaluating of district heating systems as storage for solar energy with TRNSYS 18. • Increasing solar thermal energy production with district heating integration. • Impact of thermal storage size and heating load profile on solar energy production. • Efficient solar collector distribution for district heating networks. • Influence of pipeline length and diameter for efficient prosumer energy share. [ABSTRACT FROM AUTHOR]

Evacuated tubes are extensively utilized for converting solar energy into thermal energy owing to their exceptional thermal properties and affordability. The circumferential temperature gradient of the evacuated tube is significant to the heat and mass transfer inside, but it is often neglected. This research proposed an improved model incorporating non-uniform heat flux and circumferential conduction to obtain the temperature distribution. In the experiment, A thermal insulation material was inserted inside the inner tube to create an adiabatic boundary. Various conditions (non-uniform, rectangular, and uniform heat fluxes, circumferential conduction of the coating) were numerically compared. The enhanced combined thermal transmission model was validated, demonstrating a relative error of 6.45 % in temperature increase calculation and increasing the prediction accuracy by 42.15 % at least. The distribution of the heat flux and the thermal conduction of the coating were identified as the primary factors affecting the heat transfer properties of the evacuated tube. An imbalanced distribution of heat flux resulted in non-uniform heat transfer, whereas the circumferential conduction within the coating effectively modulated the temperature distribution to achieve uniformity. The local heat transfer coefficient exhibited non-uniformity, with calculated values ranging from 0.23 to 3.25 W/(m2∙K), and an error range of −16 to +3 %. • A theoretical model incorporating circumferential conduction was developed. • The non-uniform heat transfer model exhibits the minimum RE avg (6.45 %) in dT. • An imbalanced distribution of heat flux results in non-uniform heat transfer. • The circumferential conduction modulates the temperature distribution to achieve uniformity. • The local heat transfer coefficient exhibits non-uniformity but the value is small. [ABSTRACT FROM AUTHOR]

The utilization of supercritical carbon dioxide (sCO 2) in the Brayton cycle presents several advantages, such as compact equipment, high efficiency, and rapid response time. The sCO 2 power cycle can be applied in coal-fired power, solar thermal power, and nuclear power systems. Over the past 10 years, many scholars have researched sCO 2 power systems. The compression (pressurization) process is a core thermodynamic process in sCO 2 power cycles, achieved through the use of compressors. Therefore, compressors are important components in sCO 2 power systems. This paper provides a summary of recent studies on compression processes and compressors for sCO 2 power systems. The impact of near-critical-point characteristics of the compression process on equipment and sCO 2 power cycle systems is discussed. The investigations of the performance parameters, design considerations, design methods, and performance prediction methods of sCO 2 compressors are reviewed. The typical research results on CO 2 condensation at the compressor inlet, the effects of operating conditions on compressor performance, as well as optimization of design parameters, are also summarized. Additionally, it provides a summary of sCO 2 compressor prototypes developed by research institutes worldwide and experimental studies. Finally, the current issues with sCO 2 compressors are addressed, and the main future research directions are proposed. This paper will contribute to the development of compressors and promote the acceleration of the commercialization of sCO 2 power systems. • Summary of recent studies on compression processes for sCO 2 power systems. • Near-critical-point characteristics of compression process is discussed. • Summary of compressor prototypes by research institutes and experimental studies. • Current issues and future research directions on sCO 2 compressors are presented. [ABSTRACT FROM AUTHOR]

Integrating solar heat and calcium looping (CaL) process into the existing lignite-fired power generation system is a promising technology to control CO 2 emission. However, the heat released from carbonation process led to the temperature increase of exhaust flue gas together with heat losses in boiler. To recover the waste heat from the exhaust flue gas, this paper proposed a solar-aided lignite-fired power generation system with CaL process CO 2 capture, lignite pre-drying and feedwater preheating (i.e., design III). Besides, design I without waste heat recovery and design II with only lignite pre-drying were simulated for comparison. Through the case study based on a solar-aided 330 MW lignite-fired power generation system, thermal and techno-economic performance of design III was the best on the design condition. Its standard coal consumption rate was 374.44 g/kWh, which was 61.12 g/kWh and 8.24 g/kWh lower than design I and design II, respectively. With the new design, the annual net profit of design III is $18.2924 M, with $0.5652 M higher than design II. The sensitivity analysis indicated that the thermal performance of design III was also the best under various conditions of CO 2 capture efficiency and integrated solar heat. • Solar tower, lignite Pre-drying and Feedwater preheating were integrated with CaL process CO 2 capture. • The new design recovered the waste heat from exhaust CO 2 -lean flue gas caused by carbonation process. • The new design decreased the standard coal consumption rate and increased the thermal efficiency. • The new design was proved economically feasible based on annual net profit. • Sensitivity analysis was conducted to study the influences of CO 2 capture efficiency and integrated solar heat. [ABSTRACT FROM AUTHOR]

Solar thermochemistry shows great potential as a viable solution for addressing the challenge of energy storage. The design of the reactor is still challenging the development and rapid upscaling of solar thermal conversion and storage processes. This study presents a novel reactor that capable of gas reheating and develops a comprehensive three-dimensional model that effectively couples the processes of heat transmission, gas flow and chemical reaction for the optimization of the reactor. It is demonstrated that the maximum thermal efficiency is 43.67% as the incident solar power is 3730 W, but it decreases as the temperature rises. The re-radiation loss at the reactor front face is found as a major factor affecting the reactor thermal efficiency. The result indicates that the thermal efficiency of the reactor is significantly improved as using the cutoff wavelength coating technology. As the cutoff wavelength is 1 μm, the average temperature of porous material increases from 1510.77 °C to 1634.87 °C at 60 min, and the reactor's thermal efficiency increases from 11.65% to 13.51%. This study provided comprehensive insights into heat and mass transfer in a porous solar thermochemical reactor. • A comprehensive three-dimensional model that couples heat transmission, gas flow and chemical reaction is established. • The maximum thermal efficiency is 43.67%. • The effects of the incident solar power and the cutoff wavelength coating are considered. • The reactor's thermal efficiency is improved with cutoff wavelength coating. [ABSTRACT FROM AUTHOR]

This study applies the microchannel membrane-based module to develop a novel modular and compact thermal energy storage system to meet building requirements with solar or waste thermal energy in a low-carbon path. Compared to traditional systems, the novel system demonstrates significant improvements, with the charging and discharging rates increased by 2 and 3 times. The energy storage efficiency is enhanced from 0.470 to 0.772, while energy storage density based on fluid and setup volume are increased by 78.62% and 120.90% respectively. The charging/discharging rate and solution concentration glide increase continuously as the heat source temperature rises from 75 °C to 100 °C, leading to continuous increases in energy storage density and efficiency. As increasing channel length, width, number, and module number, or decreasing channel height improves the charging/discharging rate. Energy storage density can be enhanced by augmenting the channel height and width, increasing the quantity of both channels and modules, or diminishing the channel length. Conversely, smaller channel dimensions and larger channel heights are advantageous for higher efficiency. The scaling up combined with customizability, and popularization of the proposed compact modular microchannel membrane-based absorption thermal energy storage system would be required for mass uptake of this innovative solution in building cooling applications. • Microchannel membrane-based absorption energy storage system (MMATES) is proposed. • MMATES improves the charging and discharging rates by 2 and 3 times compared to ATES. • Energy storage efficiency is enhanced by MMATES from 0.470 to 0.772 • Energy storage densities based on fluid and setup volume are all enlarged by MMATES. • Impacts of heat source temperature and module geometries on MMATES are studied. [ABSTRACT FROM AUTHOR]

A novel strategy for the decarbonization of crude oil distillation was proposed considering two distillation columns located in Sicily that were simulated by adapting the equipment datasheet of the refinery Raffineria di Milazzo (RAM). The proposed approach consists of the integration of the topping section with a concentrating solar power (CSP) plant to decrease the carbon dioxide emissions and the consumed fossil fuels in the furnaces of the distillation columns. Three hypothetical scenarios of applicative interest were considered. In that most economically sustainable, the use of solar heat allowed a decrease of CO 2 emissions of 54.2 kt/year corresponding to a reduction of about 11% of the greenhouse gas emissions joined with the saving of 19.9 kt/year of methane with a rate of return of investment (ROROI) of 16.2%. As a comparison, if the land surface occupied by the CSP plant is used for photovoltaic production of green hydrogen considering an energy consumption of the electrolyzer of 4.70 kWh/Nm3, just 24.6 and 9.0 kt/year of CO 2 and methane respectively can be saved and the ROROI decreases to 8.5%. This study indicates that solar heat can be effectively and economically integrated in crude oil distillation to achieve a significant decarbonization of refineries. • Solar heat was integrated in the topping section of a refinery • Reduction of 11% of topping CO 2 emissions was achieved • CSP better than PV to decarbonize and decrease fuel consumption • Proposed strategy seems effective and economically sustainable [ABSTRACT FROM AUTHOR]

Solar energy as a clean and abundant energy source has been widely utilized in the drying domain. Much research has focused on the drying system driven by solar energy to improve the performance and sustainability of the drying system. In this review, the construction, working principles and related studies of various solar drying technologies including direct, indirect, mixed and hybrid solar dryers were summarized and compared. In particular, we reviewed hybrid solar dryers integrated with electrical heating, biomass energy, thermal energy storage and wind energy, and then concluded their advantages and disadvantages. It was found that hybrid solar dryers can achieve a stable and continuous drying operation, which can effectively improve the performance of the dryers and the quality of the products. Among the four hybrid solar dryers, the solar dryer integrated with thermal energy storage has strong scalability and applicability, because thermal energy storage materials can integrate with solar collector and drying chamber. Furthermore, the investment cost of this hybrid solar dryer is low, with a payback period within 3 years. For solar-biomass and solar-wind dryers, they are driven by biomass and wind energy, which dramatically improve the utilization ratio of renewable energy sources. • Recent advancement on various types of solar dryers is summarized and compared. • Solar dryers combining multiple auxiliary energy sources or units are developed. • Hybrid solar dryer shows better performance for agricultural drying. • Hybrid solar dryers integrated with heat energy storage have better practicality. • Provide a recommendation on the future direction of research on solar dryers. [ABSTRACT FROM AUTHOR]

A novel cascade Rankine cycle is proposed for treating brackish groundwater using a reverse osmosis system. The cascade RO system is arranged in a loop with a steam Rankine cycle (SRC) at the top and an organic Rankine cycle (ORC) at the bottom to provide high recovery, electricity-free, and scalable options. The system comprises a solar Scheffler dish for heat input, steam turbine and expander for work output, evaporative condenser and ORC condenser for heat rejection, SRC pump, ORC pump and RO high-pressure pump for work input devices, and RO module for water desalination. This study evaluated the thermodynamic design of the system along with energy, exergy, and economic analyses performed by considering eight working fluids such as R245fa, HFO1336mzz(Z), R1225ye(Z), R1224yd(Z), R1233zd(E), R1243zf, R1234yf, and R1234ze(E). The highest overall efficiency was found 14.08% with R1234yf, and the highest RO permeate flow rate was found with R245fa, HFO1336mzz(Z), and R1233zd(E), which require the lowest mass flow rate of ORC working fluid. The highest exergy destruction was found in the solar collector and RO unit. The treated water cost is estimated to be 0.89–0.924 $/m3 of permeate water. [Display omitted] • The thermodynamic design of solar-powered SRC, ORC, and RO systems is investigated. • Energy, exergy, and economic analyses are performed with eco-friendly working fluids. • The treated water cost of selected ORC working fluids is examined. [ABSTRACT FROM AUTHOR]

Eutectic salts, a promising thermal storage material for the next generation of concentrating solar power plants, have attracted extensive attention. Its thermal performance is a crucial factor affecting the efficient utilization of efficient solar energy. Utilizing NaCl–KCl–LiCl as the phase-change material and introduced Al 2 O 3 nanoparticles to enhance thermal conductivity, thus study explores potential mechanisms for improving heat transfer and thermal storage performance. Experimental and molecular dynamics results consistently showed that doping Al 2 O 3 nanoparticles significantly increased the specific heat and thermal conductivity of eutectic salt. Specifically, at a nanoparticle content of 1.0 wt%, liquid-specific heat and thermal conductivity increased by 44.58 % and 21.43 %, respectively. Experimental and simulation results mutually validated a consistent upward trend. However, nanoparticle introduction unavoidably led to increased viscosity, with a maximum increase of 32.15 %. Subsequently, detailed simulation analysis of a shell-and-tube heat storage unit for composite materials highlighted that heat conduction rate was influenced by both natural convection and heat conduction. Therefore, viscosity and thermal conductivity should be simultaneously considered in the system applications. This scientific strategy holds promise for widespread application of eutectic salts in solar thermal energy storage, further promoting sustainable development of renewable energy. • Thermophysical properties can be improved by doping with Al 2 O 3 nanoparticles. • Doping with 1.0 wt% Al 2 O 3 nanoparticles achieves a maximum specific heat. • Thermal conductivity and viscosity showed the largest increases of 21.43 % and 22.56 %. • Thoroughly assessed the systemic application scenarios of thermal storage materials. [ABSTRACT FROM AUTHOR]

The main motivation of this study is to offer, develop, and optimize a novel solar combined technology to bring sustainability to the industrial sector via supplying 100 % green and cost-effective heating and cooling. The combination of a special type of parabolic trough collector designed to be inexpensive with low-concentration yet high-optical efficiency and a specially developed bio-driven boiler to compensate for the fluctuations of the solar energy is the heart of the proposed system. The article presents a thorough complex optimization and techno-economic-environmental analysis of the proposed solution and conducts a benchmarking analysis against cheap but unsustainable technologies of today's industries for a large case study in Northern Europe. The results prove the strong impacts of the technology in emission reduction and lower cost production of industrial heating and cooling. The solar component of the system fulfills nearly 50 % of the total demand, with the biomass heater, burning sugarcane bagasse, covering the additional demand. For the proposed system, a levelized cost of energy of 69.9 USD/MWh and an emission index of 267.7 tons/GWh are achieved, while the identical and alternative systems would necessitate 9,660, 11,600, and 3860 tons of coal, wood, or LPG, respectively, to fulfill the park's thermal requirements. • A combined solar-driven technology is proposed for the industrial sector's sustainability. • The technology may supply year-round green, and cost-effective heating and cooling. • Hybrid optimizations make a trade-off of technical, economic, and environmental impacts. • The system can supply heat and cold at a competitive LCOE of below 7 c$/kWh. • The solution can prevent annual emissions of up to 20 million kg of equivalent CO 2. [ABSTRACT FROM AUTHOR]

Solar power tower (SPT) system is a promising candidate to improve the flexibility of renewable energy power systems. Accurately predicting the dynamic performance of the SPT system is an important prerequisite for stabilizing or dispatching the system. To this end, an integrated transient model of an SPT system has been established, taking into account the dynamic behavior of all its subsystems, including concentration, thermal energy storage, and power cycle. System dynamic response characteristics are then explored under varying environmental and operational parameters. Then, a dual-time-scale hybrid method combining steady and transient models is proposed to predict system performances. Finally, based on predicted annual performances, the capacities of subsystems are optimized. The results indicate that the direct normal irradiance (DNI) and mass flow rate of molten salts and working fluids have substantial impact on the system. When the DNI and mass flow rate of molten salt vary by more than 30 %, the required adjustment time exceeds 280 s, potentially resulting in a significant reduction in output power. The proposed hybrid method allows for rapid and accurate forecasting of overall performance, reducing calculation time by 32 % while maintaining a low relative error compared with the complete transient model. Additionally, based on the annual performances predicted by the proposed calculation method, the solar multiple and thermal storage time are optimized to be 3.0 and 12.5 h, respectively, which have considered the system efficiency, stability, and cost of energy storage. • An integrated transient model of the entire SPT system is established. • Dynamic response characteristics of the system are analyzed. • A dual-time-scale hybrid method for performance prediction is proposed. • The capacity configuration of subsystems is optimized. [ABSTRACT FROM AUTHOR]

Salinity gradient solar ponds are a promising technology for harnessing/storing solar thermal energy. The energy storage capacity of solar ponds can be enhanced by incorporating phase change materials (PCMs). However, the low thermal conductivity of PCMs can negatively affect energy charging/discharging rates. In this study, an external energy storage system filled with CuO nanoparticle-enhanced PCM was employed to improve the performance and stability of a solar pond. The results were compared with water and pure PCM (paraffin) as control materials. Energy and exergy analysis was used to assess the effects of nanoparticles and their concentration on the overall solar pond performance. According to the results, the upper convective zone temperature remained consistent across all experiments and varied within the same range throughout the day. A slight temperature variation at specific times indicated the stability of the developed solar pond system. The system's exergy (energy) efficiency was increased from 10.72% (51.83%) for water to 14.71% (70.1%), 22.77% (82.13%), and 25.93% (87.58%) for PCM, PCM with 1 wt% nanoparticles, and PCM with 2 wt% nanoparticles, respectively. Incorporating nanoparticle-enhanced PCMs in external heat exchangers can effectively improve the stability and performance of solar pond systems. [Display omitted] • Nanoparticle-doped phase change material (PCM) improved the solar pond stability. • An external heat exchanger filled with PCM enhanced the solar pond performance. • The upper convective zone temperature remained consistent across all experiments. • The maximum energy efficiency (87.58 %) was found for 2 wt% nanoparticle-doped PCM. • 2 wt% nanoparticle-doped PCM provided the highest energy efficiency (25.93 %). [ABSTRACT FROM AUTHOR]

To facilitate the integration of greater amounts of renewable energy into the power grid, it is crucial to enhance the peak shaving capabilities of conventional thermal power units. This paper proposes a novel system that combines compressed steam energy storage with the Rankine cycle of a thermal power plant (referred to as the coupling system), and focuses on modeling a 200 MW thermal power unit. The performance evaluation and parameter selection of the coupling system are conducted through comprehensive energy analysis, exergy analysis, and economic analysis. The results indicate that the energy storage cycle in the coupled system can prevent boilers and turbines in the Rankine cycle from operating at extremely low loads during deep peak shaving. Specifically, when the boiler and steam turbine operate at 66.45 % of their design load, the external power of the coupling system can be reduced to 30 % of the rated power. This results in a reduction of coal consumption by 63.42 g/W * h compared to direct peak shaving of the original thermal power unit, and an improvement in exergy efficiency by 2.99 %. In this study, a 1300 m3 energy storage circulating water storage tank capacity is used as an example, and it is found that the 200 MW unit can achieve continuous deep peak regulation operation for 8.58 h. The study also reveals that a 1 % increase in the isentropic efficiency of energy storage cycle compressors can lead to a reduction in coal consumption by 2.4 g/kW*h. Moreover, economic analysis suggests that maintaining a compressor efficiency of 86 %, utilizing 7 compression stages, and prioritizing the effectiveness of the heat exchanger are optimal for maximizing the system's revenue. These factors collectively result in a shorter payback period for the coupling system and an overall increase in total income. • A new thermal power plant compressed steam energy storage and Rankine cycle coupling system is proposed. • Compared with other energy storage systems, this system occupies a small area. • The economic analysis of the system was carried out to determine the most suitable component performance and quantity for the system. • Compared the advantages and disadvantages of different energy storage systems in thermal power peak regulation. [ABSTRACT FROM AUTHOR]

Deep reinforcement learning (DRL) has gained attention from the scientific community due to its potential for optimizing complex control schemes. This study describes the implementation of a DRL platform that allows training smart agents to manage a complex water heating system in an institutional building that uses solar energy and waste heat from a water chiller as energy sources. In addition to optimizing the use of energy while delivering hot water, the agents are also trained to activate the chiller, to avoid the premature degradation of the system, and to continue providing hot water in case of failures of heating devices of the system. The definition of the reward function, which is fundamental to simultaneously impose all these goals on the agent, is tested by comparing different agents trained to prioritize different goals. In comparison with a previous study done on the same system with standard reinforcement learning techniques, this method allows far more freedom to control the system. The deep neural networks and the DRL algorithm were programmed without specialized libraries, implying that the algorithm could be used to train smart agents in programs without direct access to deep learning libraries, or in the actual system with a simple programmable controller. • Discussion on the foundations of the Deep Q-Network algorithm. • Reward function that considers more than one pair of opposing goals is formulated. • Developed algorithm does not rely on specialized deep learning platforms. • Reward function is validated by analyzing the behavior of the controlling agents. • Agents are trained to adapt the controlling strategy when failures occur. [ABSTRACT FROM AUTHOR]

The present work deals with the dynamic modelling of a small-scale thermo-hydraulic engine, designed for residential application. Comparing to Organic Rankine systems, the CAPILI cycle uses a hydraulic motor instead of a turbine. The solar activated CAPILI engine produces electricity through a liquid piston oscillating between two reservoirs connected alternatively to a high pressure evaporator and a low pressure condenser. The heat rejected by the condenser is discharged in the ground through geothermal probes at 13 °C while the solar panels provide heat at about 70 °C. The liquid piston drives a hydraulic motor coupled to an electrical generator to produce electricity. Based on these temperature conditions, the dynamic modelling approach undertaken in the study enables a sensitivity analysis of the most impacting parameters of the CAPILI system. In particular, the study focuses on the volume capacity and the filling ratio of transfer cylinders, the switching -balancing- volume of the cycle as well as the electrical load. The results highlight the effects of each investigated parameters on the whole behaviour of the simulated CAPILI system. The best performance of the investigated CAPILI system operating under the given operating conditions, highlights a thermal efficiency of 9.14 % and almost 55 % for the exergy efficiency. [Display omitted] • The new CAPILI energy system is investigated for a residential application. • The thermohydraulic system is activated with solar thermal energy to produce electricity. • Dynamic modelling and sensitivity analysis are conducted to assess the performance of the patented CAPILI system. • Sensitivity analysis includes volume capacity, filling ratio, switching volumes and the electrical loads. • The best thermodynamic performance we evaluated at 9.14% for the thermal efficiency and almost 55% for exergy performance. [ABSTRACT FROM AUTHOR]

The concentrated parabolic dish collector (PDC) systems are widely utilized for the purpose of generating high-temperature heat by receiving and converting solar energy efficiently into thermal energy. Cavity receivers including spiral coils have a common use in PDC system for optimal thermal performance. Therefore, to enhance the thermal performance of a PDC system, the present study investigates different cavity receiver configurations, such as cylinder and conical shaped receivers with flat and spherical absorber surface as well as the effect of spiral coil arrangement. To identify the most optimal spirally coiled cavity receiver, the comparison is conducted based on outlet temperature, heat exchange rate, thermal efficiency, effectiveness, and thermal performance capability (TPC). The investigations were conducted using the ANSYS Fluent CFD simulation software package. The SolTrace software package was utilized to compute the maximum heat flux incident on the absorber surface of the receiver, and peak heat flux data was used as input parameter at the absorber surface of the receiver. Furthermore, to select the suitable working fluid in PDC system, different heat transfer fluids, such as Syltherm 800, Xceltherm 600, ParathermHR™ and water, respectively were studied. From the thermal analysis of various proposed receiver geometries, the receiver with conical shape and spherical absorber surface is more efficient over other configurations. It provides 50 % higher heat transfer rate thancylindrical receiver with flat absorber surface. Moreover, receiver's thermal performance could modestly be improved by modifying the spiral coil pitch (variable pitch). In terms of pumping power consumption, readily availability, low viscosity, and high specific heat, water is suggested as working fluid for receiver of PDC system. • Receiver shape optimization for performance enhancement of parabolic dish collector. • Cylindrical and conical receivers with spherical absorbers are investigated. • Effects of modified spiral coil arrangement inside the receiver were studied. • Conical receiver with spherical absorber has higher heat transfer rate than others. • Water can be used as heat transfer fluid as it has a low requirement of pumping power. [ABSTRACT FROM AUTHOR]

Solar thermal power system and photovoltaic coupled system can supply electric energy based on renewable solar energy. To explore the optimal configuration of hybrid microgrid driven by solar energy and to achieve a stable and sufficient electric power supply for the distributed energy system, this paper configures a solar thermal-photovoltaic hybrid microgrid and compares the performance of several microgrids based on the power load analysis of the building. The working fluid and the microgrid configuration are determined based on the performance evaluation of single and hybrid microgrids. The effect of solar irradiation on economic and environmental performance is analyzed under the meteorological data of Xi'an and Lhasa in China. Furthermore, the configuration optimizations of a hybrid microgrid based on the actual load and basic load of the building are carried out to examine the performance of the system. Results indicate that economic and environmental performances are sensitive to solar irradiation. More than 50 % of the area of solar thermal collector can be saved for Lhasa compared with Xi'an. Solar thermal-photovoltaic hybrid microgrid with battery can decrease carbon emission and avoid dependence on the external power grid. • Cooling, heating, power load of a six-story building is evaluated and converted. • Multi-objective optimization of solar thermal power system microgrid is performed. • Configuration optimization of solar thermal-PV hybrid microgrid is carried out. • Optimal microgrid configuration under different power load types is compared. [ABSTRACT FROM AUTHOR]

Notwithstanding the gradual substitution of conventional fossil fuels with sustainable energies, the enduring relevance of nucleate boiling persists, owing to its remarkable prowess in heat transfer. This article undertakes a comprehensive review of the diverse applications of nucleate boiling within the renewable energy (concentrated solar thermal and geothermal energy) and unconventional thermal management (concentrator photovoltaic, wind turbine, electronic battery and fuel cell) as witnessed in recent years. These initial forays have incontrovertibly validated the vast potential of boiling across various nascent fields. Nevertheless, considerable scope remains for refining both the design of its energy conversion schemes and the methodologies employed in boiling modeling. Furthermore, the latest advancements in theoretical modeling of nucleate boiling are reviewed as well. In the future, greater emphasis will be placed on comprehending the intricacies of bubble dynamics, while adopting transient simulations and differentiation of individual bubbles. The objective of this article is to foster effective communication between researchers operating within the realm of renewable energy systems and unconventional thermal management and those engaged in the conventional study of boiling, thereby facilitating the wider application and optimal utilization of nucleate boiling within the domain of unconventional energy systems. • Boiling research is still relevant and promising in the new energy era. • Boiling modeling of concentrated solar thermal and geothermal is rapidly improving. • Boiling mostly achieves overfulfilled cooling, but needs further optimization. • Refining bubble behavior is the core of improving nucleate boiling simulation. • Systematic boiling models coupling more bubble dynamic behaviors are trends. [ABSTRACT FROM AUTHOR]

Solar thermal systems are far more important than solar PV systems in residential and commercial applications. Improving the efficiency of solar thermal technology is a major challenge. Several researchers separately studied the effects of turbulence enhancers and nanofluids to enhance heat transfer of solar flat plate collectors (SFPC). The current research focuses on the synergic effect of an internally grooved absorber tube and Al 2 O 3 -WEG-based nanofluid on SFPC performance. The experimental investigation used various concentrations of nanoparticles (0.01 %, 0.05 %, 0.1 %, and 0.2 %) and mass flow rates (MFR) (0.024 kg/s, 0.036 kg/s and 0.048 kg/s). The outcomes of Al 2 O 3 -WEG based nanofluid and plain working fluid were compared. MFRs of 0.036 kg/s and 0.2 % vol. Showed the highest efficiency for SFPC models 1 and 2. The efficiency enhancement of model 2 over model 1 of plain fluid increased in an order of 46.37 %, 54.13 %, and 33.83 % for MFRs of 0.024, 0.036, and 0.048 kg/s, respectively. The maximum efficiency enhancement of model 2 over model 1 was 54.1 % for a MFR of 0.036 kg/s with 0.2 % vol. The created ANN models predicted the output values of the SFPC experiment accurately in real-time. • Nanofluid was prepared by Al 2 O 3 nanoparticles in WEG fluid in the ratio of 50:50. • The optimum conditions for model 1 and model 2 of SFPC was 0.036 kg/s and 0.2 % vol. • Model 2 obtained 54.1 % efficiency over model 1 at optimum conditions. • ANN model is utilized to forecast the performance, heat gain and outlet temperature. [ABSTRACT FROM AUTHOR]

The photovoltaic-thermal collector (PV/T) is an innovative technology that combines PV cells and solar thermal collectors into a co-generation unit, enabling full-spectrum solar utilization. This research proposes and examines a hybrid PV/T system with novel trapezoidal fluid channels embedded in graphite, arranged in a parallel S-shaped structure under outdoor conditions of Beijing. Parametric discussions and daily performance analysis are conducted to assess its effectiveness and stability. A daily average of 12.7 °C reduction in cell temperature compared to PV modules results in a relative 5.20 % improvement in electrical output under the intensity of solar radiation is 597 W/m2. Similarly, the peak temperature of the water tank reaches 56.9 °C, and thermal efficiency is enhanced by 7.86 % over conventional sheet-tube PV/T collectors. For further optimization, a constrained adaptive particle swarm optimization algorithm (EPF-APSO) is constructed based on the experimental data, implementing a variable water flow rate (VWV) strategy. Compared to a constant water flow rate (CWV), the overall energy collected varies from 2.755 to 2.828 kWh per day, potentially reducing pump energy consumption by 17.93 %. The contribution of this paper provides references on structural and operational parameters optimization of PV/T collectors applying machine learning algorithms for better comprehensive efficiency. [Display omitted] • The novel trapezoidal fluid channels embedded in graphite were investigated. • Parametric discussions and daily performance analysis were to assess effectiveness. • A daily average of 12.7 °C reduction in cell temperature compared to PV modules. • The strategy of variable water flow rate was implemented for further optimization. • APSO algorithm is constructed with the experimental data, seeking optimal groups. [ABSTRACT FROM AUTHOR]

The application of integrated energy systems (IES) in urban areas is gradually increasing, yet the constraint of limited building space poses a significant challenge to effective system planning. In this paper, to address the issue of area limitation from the perspective of improving solar energy utilization. A novel IES utilizing solar spectral beam splitting (SBS) for hydrogen production is proposed, which introduces SBS technology to make full use of the sun's full-spectrum energy. Furthermore, the incorporation of photocatalytic hydrogen production introduces an innovative approach to meet the hydrogen needs of hydrogen refuelling stations, facilitating highly efficient co-generation of cooling, heating, electricity, and hydrogen supply. To determine the optimal system configuration, a comparison is made with a stand-alone solar system using a honey badger-simulated annealing optimization algorithm. The results show that the SBS-IES achieves a solar energy utilization rate of 37.72% and reduces equipment footprint by 20.48%. Furthermore, a sensitivity analysis is performed to analyse the impact of changes in floor space on the system. This innovative system is suitable for small-scale IES and serves as an efficient solution for urban energy systems. • Application of equipment using solar spectral beam splitting technology to integrated energy systems. • Providing hydrogen demand for hydrogen refuelling stations and expanding the application scenario for integrated energy systems. • Feasibility validation of photocatalytic hydrogen production for on-site hydrogen supply. • An integrated energy system suitable for small buildings in urban areas is proposed. • A honey badger-simulated annealing optimization algorithm is applied. [ABSTRACT FROM AUTHOR]

Maintaining the security of supply is one of the challenges that system operators face. Variability and uncertainty increase due to the penetration of variable renewable energy sources such as solar and wind, while flexible technologies such as traditional thermal units are phased out to reduce emissions. The current methods for assessing power system adequacy are based on historical operations and are generally intended to be applied to thermal-dominated electricity systems. Therefore, it is necessary to improve current adequacy assessment methods since they usually neglect the flexibility of power systems. This paper presents a methodological approach for jointly assessing the adequacy and flexibility of power systems. The methodology's usefulness is demonstrated through its application to the Spanish power system. For the case study, results show that new closed-looped pumped storage hydro technology provides 25% flexibility while contributing to adequacy due to higher installed capacity and round-trip efficiency. Due to shorter storage duration, batteries only contribute to flexibility, supplying 16% of the total operating reserves. Therefore, this study shows that metrics of flexibility and individual contribution to the power system adequacy complement each other and simultaneously enable the scarcities of power systems to be observed. • The approach identifies technologies contributing to adequacy, flexibility, or both. • Storage technologies behave differently depending on the service to be provided. • New pumped hydro storage provides 25% flexibility regarding power variations. • Batteries provide 15% of flexibility requirements in terms of operating reserves. • 12% of the battery capacity serves to maintain adequacy during critical periods. [ABSTRACT FROM AUTHOR]

Solar-assisted heat pumps (SAHPs) with photovoltaic-thermal technologies are promising systems for efficiently converting solar energy into useful thermal energy. In this paper, the performance of a SAHP coupled with a novel photovoltaic-thermal air heater (PVTAH) was evaluated under various operating and geometrical parameters. The PVTAH used in this study has a triangular block to improve its thermal efficiency, which also increases the heat pump performance. Using the heat balance equations, a mathematical model was developed and validated through experimental results. With the developed model, the effects of the air mass flow rate, PVTAH area, solar intensity, ambient temperature, and inlet water temperature on the performance of the SAHP with a PVTAH were examined and discussed. The results indicate that the SAHP with PVTAH could operate independently without power from the grid under most conditions, as the PVTAH generates more power than the system requires. In addition, compared to the traditional air-source heat pump, the SAHP with PVTAH enhanced the coefficient of performance of the heat pump by 13.28 %. Consequently, the feasibility of the proposed system was confirmed and this hybrid system is worthwhile to promote and apply. • Mathematical model for a SAHP coupled with a novel PVTAH has been developed. • Mathematical model was validated successfully using experimental data. • The influence of various parameters on the system performance was studied. • SAHP with PVTAH operated without power from the grid in most conditions. • SAHP with PVTAH improved heat pump COP by 13.24 % compared to air source heat pump. [ABSTRACT FROM AUTHOR]

Ternary chloride salt (NaCl–KCl–MgCl 2) is considered as a potential high temperature thermal storage material owing to its low melting point, excellent thermal properties and low cost. However, the thermophysical properties of ternary chloride salts are difficult to measure under high-temperature conditions. In this study, the microscopic model of ternary chloride salt is constructed by Materials Studio software. The ratio of Na ions, K ions, Mg ions and Cl ions in the simulation system is determined according to the molar ratio of NaCl–KCl–MgCl 2 eutectic ternary chloride salt. The total number of ions is identified based on computational resources and the accuracy of simulation results, and the number of the four ions in the system is finally determined. LAMMPS software is used to simulate the microstructure and calculate the thermal properties. Simulation results indicate that as the temperature increases, the distance between cluster ions increases, while the coordination number decreases, resulting in the ion association weakens. Simulation results of thermophysical properties are in good agreement with the experimental measurements. The decrease in density and viscosity is attributed to the weakening of ion association with increasing temperature. All the results are expected to provide reliable guidance for the design and preparation of next-generation concentrating solar thermal energy storage materials. • Thermodynamic properties were comprehensively investigated by the NEMD simulations. • Thermodynamic properties of ternary chloride salt at high temperature were obtained with desirable accuracy. • The influence mechanism of microstructure on macroscopic thermophysical properties was revealed by ionic structure. [ABSTRACT FROM AUTHOR]

Hybridizing nuclear and renewable energy systems helps enhance the benefits of both sources and eliminate their disadvantages. In order to provide resilience, energy systems need to be designed in a complementary manner to achieve an uninterrupted energy supply. The current study proposes a hybridization of a sodium fast reactor with a concentrated solar plant and molten salt energy storage system. By considering the community requirements, additional subsystems are added that use process heat and power to generate more useful commodities. The proposed nuclear and renewable hybrid energy system generates heat, power, hydrogen, fresh water, and cooling effect for communities in order to meet their needs in a sustainable fashion. The proposed system is a potential alternative to currently available fossil fuel-driven systems. Intermittency and flexibility issues of such systems are overcome with hybridization and integration. Apart from the other commodities, hydrogen is produced and supplied to the community by considering hydrogenization along with the electrification of transportation. Specifically, a parabolic trough collector-type concentrated solar plant, a sodium-cooled fast reactor, a molten salt energy storage unit, a lithium bromide absorption refrigerator, a solid-oxide electrolyser, a multi-effect distillation-type desalination unit, and a district heating system are considered to be used in the integrated system. The proposed system is investigated by considering the first and second laws of thermodynamics, which assess energy and exergy inputs and outputs of the system and subsystems. In order to analyze the system with realistic conditions, actual data for California, the United States, is considered. For a community with 240243 residents, a sodium fast reactor with 1.5 GW th capacity and parabolic trough collectors with 0.5 GW th capacity are considered, along with a 4 GWh of molten salt energy storage system. Annual average energy and exergy efficiencies are found to be 63.54 % and 57.96 %. The maximum energy efficiency is calculated as 84.4 %, and the maximum exergy efficiency is found as 81.28 %. Apart from the current community needs, 53,285.15 tonnes of hydrogen is produced annually. • A new solar integrated sodium fast reactor with molten salt storage is designed and analyzed. • A complementarity between energy systems and demand is studied with a time-dependent analysis. • Energy and exergy efficiencies are investigated for each hour in a year. • An operational algorithm is developed for various scenarios. [ABSTRACT FROM AUTHOR]

The goal of the study is to present two independent solutions capable of modelling the thermal behaviour of the solar assisted district heating systems with seasonal thermal storage. The study uses a new approach in modelling the thermal behaviour of the solar assisted district heating systems, by using two calculation methods: the analytical method and TRNSYS to perform the simulations, and by using two climatic data as input: EnergyPlus and Meteonorm. The heat demand of the buildings, the shares of energy produced by the solar thermal system, and by the gas boiler used as backup, and a very large number of the system parameters: temperature variation in each layer of the seasonal heat storage tank, temperatures, and flow rates on all the circuits, etc. were calculated. The results were compared using three parameters: Mean Deviation, Mean Bias Error and Root Mean Square Error. All the results calculated with the two methods were found to be very close. The annual solar fraction was found to be in the range of (34.9–50.2) %, depending on the type of the considered solar thermal collector, the combination of calculation method and climatic data as input. The study proves that both analytical method and TRNSYS can be used successfully to simulate the thermal behaviour of solar assisted district heating systems with seasonal heat storage. [Display omitted] • Analytical modeling and TRNSYS simulation of district heating system. • Solar assisted and seasonal storage district heating. • Complex investigation with large number of parameters. • EnergyPlus and Meteonorm climatic data as input. [ABSTRACT FROM AUTHOR]

The hybridization of solar and biomass energy systems is a promising technology for mitigating the issues of energy generation-related greenhouse gas emissions and high energy prices. The global warming potential and economic feasibility of a hybrid solar-bioenergy system, comprised of a concentrated solar tower, biomass gasifier, thermal storage, and combined cycle gas turbine, have been evaluated by using life cycle assessment and cost benefit analysis, respectively. Sensitivity analysis is carried out to identify the hotspots of costs and emissions. The net present worth of the proposed system at the 30th year was calculated to be about €–0.7 billion. There are two suggestions to enhance the economic viability of the system, allowing for a payback period of less than 10 years. The first suggestion involves reducing the O&M cost of the system by 19% at 43.9 €/MWh, and the second suggestion entails increasing the overall efficiency of the system by 20%. This system can save 787.7 kg of CO 2 -eq/ton waste-wood and generate a total of about 0.8 million MWh of electricity each year. The findings provide scientific evidence for the design and deployment of the hybrid technology to enhance energy security, while reducing carbon emissions. Overall, this study highlights the potential benefits of hybrid solar-bioenergy systems and encourages the adoption of sustainable energy practices for a greener future. • Carbon footprint and economics of CSTGB-based electricity generation was explored • The CSTGB system generated 0.8 million MWh electricity annually • The CSTGB system saved 787.7 kgCO 2 -eq/ton waste-wood • CCS had the most significant impact on the carbon footprint • Operation and maintenance cost significantly affected economic viability [ABSTRACT FROM AUTHOR]

Solar hydrogen production by water splitting reaction is an important route to realize the storage of solar energy. The involvement of light and chemical energy can reduce the high reaction temperature of direct thermochemical water splitting reactions, but the pivotal issues such as energy, exergy, and energy level relationships behind the temperature reduction remain under-researched. A graphic analysis of water splitting reactions using the temperature-entropy and energy utilization diagrams is proposed to research the energy, exergy, and energy level relationships. The energy composition and conversion mechanisms with the light and chemical energy are presented in the diagrams by comparing with direct thermochemical water splitting reactions. Three cases, including the photocatalytic, photo-thermochemical, and methane steam reforming reactions, are studied to explain the effect of light, the synergistic effect of heat and light, and the effect of chemical energy in reducing the temperature of water splitting reactions. The energy levels of light and methane are higher than those of hydrogen, thus lowering the energy level of heat and reducing reaction temperatures. The discovery of the energy level required for hydrogen production will provide guidance for reducing its temperature. • The graphic analysis method of the water splitting reactions is proposed. • The roles of heat, light, and chemical energy in the reaction are studied. • The energy, exergy, and energy level laws for temperature reduction are revealed. • The energy levels of the input energies should be higher than that of hydrogen. [ABSTRACT FROM AUTHOR]