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ABO 3 -type perovskites have been demonstrated as promising redox materials for solar thermochemical H 2 production. In this work, a new energy material screening method based on the neural network system is designed as a feasible way to search for promising H 2 production materials. The predicted oxygen vacancy formation energy of the selected YCrO 3-δ is 4.199 eV, hinting excellent H 2 production potential. Thermogravimetric analysis shows that the doping of Zr into YCrO 3-δ improves oxygen formation capacity, leading to the maximum δ of 0.106. The molar enthalpy and entropy of YCr 0.75 Zr 0.25 O 3-δ have the positive relationship with δ , and the maximum values of which are 273.7 kJ mol−1 and 164.9 J mol−1 K−1 respectively. Based on the equilibrium thermodynamic principle, the peak H 2 yield is predicted to be 444.6 μmol g−1. Considering material kinetic limitation, gas-solid heat recovery and parameter sensitivity, the maximum H 2 production efficiency of YCr 0.75 Zr 0.25 O 3-δ is 17.3%. The combination of neural network and material thermodynamics provides a new pathway to design promising H 2 production materials, and the screened YCrO 3-δ presents excellent solar thermochemical H 2 production capacity. [Display omitted] [ABSTRACT FROM AUTHOR]

Uncertain parameters and factors substantially impact the operational performances of combined cooling, heating, and power (CCHP) systems. This paper constructs a chance-constrained programming model for system design and energy dispatch management of a hybrid solar CCHP system under the uncertainties of solar energy and building loads. The uncertain scenarios with probability distributions are generated in the Latin hypercube sampling and clustering methods. The chance-constrained model transforms stochastic optimization into deterministic optimization based on these scenarios. Then, the multi-objective optimization model of CCHP system considering the performances of economic, energy, emission, and flexibility is established, and the modified ε -constraint method is employed to obtain Pareto solutions. A case study validates the proposed model. The capacities and operational strategies of components in the hybrid CCHP system are optimized, and the impacts of the confidence level of probability distributions of uncertain factors on the optimization results are discussed. The results indicate that the photovoltaic capacity in the hybrid CCHP system declines by 87.5% when the confidence level increases from 0.50 to 0.99. But other components' capacities are raised, and the gas turbine capacity as the key component rises by 10.49%. The energetic and environmental performances of the CCHP system rise with the confidence level, and the operation safety is improved. [ABSTRACT FROM AUTHOR]

A novel solar-driven high-temperature co-electrolysis system is proposed, which consists of a solar photovoltaics module, a parabolic trough collector module, an ammonia-based chemical heat pump (CHP), and a solid oxide electrolyzer cell (SOEC) module. The ammonia-based CHP implemented with a hydrogen-permeant membrane reactor can upgrade solar heat. Numerical models to simulate the hydrogen-permeant membrane reactor, the SOEC, and the entire system have been developed. The models have been validated by comparing model-generated results with experimental data from references. The effects of critical operating parameters on the system performance have been investigated parametrically. Through an optimization, a maximum solar-to-fuel efficiency η STF = 25.4% has been achieved, which is 6.4% higher than a typical solar-driven high temperature co-electrolysis. [ABSTRACT FROM AUTHOR]

It is becoming increasingly important for human societies to use renewable energy. More effective energy storage solutions are crucial to increase the share of renewable energy in the domestic and industrial sectors, which consumes a large amount of thermal energy for heating and cooling purposes. There has been little quantitative analysis of thermal energy storage in solar-based cold production units. An efficient method of designing heat and/or cold storage systems and smart operation planning can help a cooling/heating system to be smaller for the same capacity of supply and thereby reducing the costs of initial investment and costs of operation. This paper attempts to show how the size of a heat and cold storage system affects its thermal performance and how it can lower costs and emissions. For this, a solar-assisted thermally driven cooling supply system with various designs and integrations of their cold storage unit is simulated dynamically through a whole year in Qassim region as the case study. The results show that a system design with double solar heat storage and double cold storage in parallel arrangement results in the best techno-economic-environmental performance. For this case, the levelized cost of cooling will be 383 USD/MWhr, which will be at least 3% lower than the typical hot/cold buffer tank design scenario. [ABSTRACT FROM AUTHOR]

Research on large-scale energy storage systems has so far been very dedicatedly focused on electricity storage. Even for thermal energy-driven technologies, so-called Carnot batteries, larger electricity output, and higher power-to-power efficiency have been the major concerns. On the other hand, energy storage technologies are mainly useful for helping more renewable energy deployment for which recent studies show that most of the energy sectors are going through a smooth and continuous transition towards sustainability except for the industrial heating and cooling sectors. Therefore, developing energy storage solutions that can potentially contribute to this sector will be precious. This study proposes a multi-generating solar-assisted molten-salt-driven Carnot battery that is used for storing excess electricity of a PV farm in Saudi Arabia and delivering power for grid balancing, steam for process heating, as well as space heating/cooling for several industrial factories. The article presents a detailed techno-economic analysis of the system after making the configuration optimized based on multi-objective optimization techniques. The results show that such a multi-generating solar-assisted molten-salt-driven Carnot battery in the optimized configuration may result in power-to-power, power-to-process heat, and overall efficiencies of 26.82%, 55.78%, and 82.6%. With these performance factors, using standard global prices for electricity and heating, with a process heating cost of higher than 10.15 c$/kWh (which is very realistic), the system will outperform only power-generating Carnot batteries. [ABSTRACT FROM AUTHOR]

The paper reports a system combining Solar Thermal Collectors (STC), Borehole Thermal Energy Storage (BTES), a Heap Pump (HP) and a backup boiler for space heating and Domestic Hot Water (DHW) production. The integration of the components and the overall control strategy are described. The system is flexible, being able to select the best thermal source and to use it directly or through a HP, while only the excess solar heat is stored into the BTES. The contribution of every subsystem to the energy mix is discussed. For a "reference configuration" combining the three subsystems ("Design D") and characterized by heating and DHW needs of 510.5 MWh.y−1 and 226.7 MWh.y−1 respectively, a BTES volume of 15000 m3, a distance between boreholes of 3 m, a STC area of 2500 m2, and a solar tank volume of 100 m3, the system uses 274 units of gas and electricity to provide 1000 units of heating and DHW. This reference configuration outperforms any alternative design: Design A (STC only), Design B (STC and HP) and design C (STC and BTES) would respectively require 612, 480 and 591 units of gas and electricity to do so. A one-at-a-time analysis reveals that the STC area, azimuth and inclination, the solar tank volume, the BTES volume, the borehole density and the HP power are key parameters to the overall system performance. [Display omitted] [ABSTRACT FROM AUTHOR]

In the current study, a renewable system with two potential wind and solar energies for electricity production, cooling, and heating has been investigated. The proposed system included reverse osmosis, heat pumps, fuel cell subsystems, wind turbines, photovoltaic/thermal panel units, battery storage, and a hydrogen storage tank. Given Iran's high potential for renewable energy, a performance analysis of six cities, Esfahan, Zanjan, Bandar Anzali, Ahvaz, Bandar Abbas, and Tabriz was done to determine where the proposed power plant should be located. Six decision factors were analyzed for system performance: solar panel angle, solar panel count, wind turbine count, cooling capacity, heating capacity, and fuel cell power. The findings demonstrate that the number of solar panels, wind turbines, and fuel cells significantly influences power, fuel consumption, and system costs. Finally, the outcomes were analyzed by the Response surface method to choose the best system that can satisfy the demand for residential units for one year. To evaluate the effectiveness of the suggested method, a 100-unit apartment building with a 196-square-meter floor space was considered. The results also showed that the combination of hydrogen units and battery storage reduced variations in supply and demand and correctly stabilized the stored energy during a drop in output. The suggested system has a life cycle cost of 674278.4$/h and the capacity to generate 225694.8 kWh of surplus power for residential units with a thermal comfort index. According to the optimization results, the system's optimal panel count was 106, the optimal angle was 26°, the optimal fuel cell power was 65.6 kW, the ideal wind turbine count was 24, the ideal heating capacity was 20.2 kW, and the optimal cooling capacity was 48.7 kW. [ABSTRACT FROM AUTHOR]

Solar-driven thermochemical energy storage (TCES) can address the mismatch between solar heat production and heating demand and contribute to decarbonisation in buildings. In many studies of typical salt hydrate TCES systems, massive heat carried by the discharged humid airflow during the charging phase is not well-utilised but directly dissipated to the ambient. Therefore, a solar photovoltaic/thermal-powered TCES system integrating a heat exchanger (PV/T-TCES-HEX system) is proposed in this study for recovering this part of heat. To study the effect of adding the PV/T collector and heat exchanger (HEX) on the performance of the TCES system, the thermal performance of the PV/T-TCES-HEX system is compared with other two TCES systems via COMSOL modelling. Results suggest that the PV/T-TCES-HEX system requires an additional external electricity input of 11.86 kWh on a typical summer day in Nottingham, which is only 40.53% of the TCES-only system. The overall thermal efficiency of the PV/T-TCES-HEX system is 56.00%, indicating an efficiency enhancement of 146.80%. A lower mass flow rate leads to higher thermal efficiency and storage energy. The system has the highest overall thermal efficiency when the reactor bed thickness is 0.04 m (57.55%) and when the reactor bed length is 0.5 m (58.73%). [ABSTRACT FROM AUTHOR]

To solve the intermittent problem of solar drying systems, this study proposes a solar vacuum tube collector coupled heat pump drying (HPD) system that can adopt three operating modes as different climatic conditions. The performance of the system under different working modes and drying characteristics was analyzed; moreover, the system was also based on the relationship between energy supply and consumption. The results show that under load conditions, the system runs in the solar drying (SD) mode and the drying chamber temperature can reach >50 °C. In the HPD mode, the average heating power of the system is 11.88 kW, the heating coefficient is 2.26 and the average thermal efficiency of the heat exchanger is 39.3%. In the solar-assisted heat pump drying (SAHPD) mode, the average coefficient of performance of the system is 3.26, compared to HPD model, a 44.2% increase. The heating ratios of the SD, HPD and SAHPD modes were 37.9%, 58.5% and 3.6%, respectively. Furthermore, the Two-term models with R 2 value of 0.9986 and RMSE value of 0.01038 was considered the best drying kinetics model for the vacuum tube collector coupled heat pump drying grapes. This study guides the application of SAHPD systems in agricultural products drying. [ABSTRACT FROM AUTHOR]

Direct-expansion solar-assisted heat pump (DX-SAHP) system has proven to be an effective energy-saving application. In view of the low output temperature and large radiant heat loss in the conventional flat plate type DX-SAHP, this paper proposed an evacuated tube type DX-SAHP system to realize performance enhancement. Then, an experimental prototype of the proposed system was originally designed and constructed in laboratory. Moreover, the thermodynamic performance of the system was thoroughly investigated and analyzed under different operating conditions. The results indicate that the thermodynamic performance of the proposed system is sensitive to the solar radiation intensity and collector area. About every 100 W m−2 increase of solar radiation intensity, the COP increases nearly 1.70% and the heat collection efficiency decreases nearly 8.44%. Increasing collector area (from 1.5 m2 to 3 m2) results in 8.81% increase of COP and 22.47% reduction of the system exergy efficiency. A higher circulating water temperature can effectively improve its exergy performance and higher ambient temperature can enhance its energetic performance. Additionally, the optimization of the evacuated tube collector-evaporator should be preferential to improve the system due to large exergy destruction and low exergy efficiency. [ABSTRACT FROM AUTHOR]

Recompression Brayton cycles using supercritical CO 2 as the working fluid appear as a prominent alternative for thermo-solar power applications. Also, solar energy's natural variability and intermittence make it difficult for solar plants to operate consistently and predictably. Thus, two of the most explored mitigating alternatives are thermal energy storage and auxiliary heating systems. Hence, this paper used actual meteorological data and transient numerical simulations to investigate the power output dynamics of a 10 MW plant. The modeling of an active control system of the working fluid mass inventory allowed the plant to operate in a stable manner while accounting for the significant variations in the fluid's thermophysical properties. Also, the study investigated the effect of the sizes of the thermal energy storage system and solar collectors field on the dynamics of the system. Finally, statistical analyses with actual meteorological data from Florianopolis/Brazil for nine days between 2017 and 2018 supported determining the optimal thermal energy storage system size. Hence, depending on the daily conditions, the results showed the operating settings that minimize the use of auxiliary heating with reductions of fuel consumption larger than 10%. [ABSTRACT FROM AUTHOR]

Harvesting energy from the hot sun and the cold universe is being investigated and has attracted much attention due to its clean utilization. Herein, a broadband selective absorber/emitter (BS-A/E) is designed and fabricated for the hybrid utilization of diurnal solar thermal and nocturnal radiative cooling. The BS-A/E exhibits high photon absorption in the solar band (i.e., 0.3–3 μm) with a weighted solar absorption of ∼0.83, a strong thermal emission mainly within the atmospheric window (i.e., 8–13 μm), and a low thermal emissivity in other infrared wavelength bands. The outdoor experiment demonstrates that the stagnation temperature of the BS-A/E is 11.6 °C greater than black paint under sunshine and 0.6 °C lower than that of black paint under darkness, showing considerable solar thermal and radiative cooling performance. In addition, thermal prediction also reveals that the BS-A/E can not only achieve solar heating during the day but also obtain sub-ambient cooling phenomenon during the night, indicating that the BS-A/E is capable of providing continuous heating and cooling for humans in various potential applications, such as all-day thermoelectric power generation and thermal storage-based space heating/cooling. [ABSTRACT FROM AUTHOR]

In this experimental work, the thermal and thermohydraulic performance of two novel designs of solar air heater employing confined submerged circular air jet arrays is investigated. Design-I consists of a wavy transparent acrylic sheet for air jet impingement from the top side of the absorber plate, while Design-II consists of a wavy metallic impinging plate for air jet impingement from the bottom side of the absorber plate. Both solar air heaters are designed to induce stable air jets for the range of mass flow rates ranging from 0.01 kg/s to 0.04 kg/s. Obtained results presented the superiority of Design-I in terms of heat transfer augmentation to air and compactness in size compared to Design-II. The thermal and thermohydraulic efficiency of Design-I corresponding to the mass flow rate of 0.04 kg/s is obtained as 89.72% and 89.16%, which is found to be 24.33% and 24.52% high compared to Design-II, respectively. In addition, the recommended value of the mass flow rate is obtained as 0.03 kg/s on the basis of thermohydraulic efficiency and operating cost, that presents an operating cost of 0.109 INR/kWh for Design-I. This work is extended for the numerical investigation to reveal the associated physics of fluid and heat transfer in solar air heater designs. In numerical investigation, 3D structured O-grid mesh is generated and RNG k-ε turbulence model is employed using the commercial CFD tool. [ABSTRACT FROM AUTHOR]

Hybrid photovoltaic/thermal (PV/T) systems are proposed to harvest the two renewable forms of energy, thermal and electrical. The PV/T system generates low-temperature thermal and electrical energy, which is usually not much and might meet the demand for residential building heating and hot water. This research presents the economic evaluation and annual energy performance of a novel series-coupled PV/T and a solar thermal collector (TC) with a solar direct expansion heat pump system. A comprehensive approach was developed and utilized to evaluate the quantitative and qualitative performance of the hybrid refrigerant-based PV/T-TC system using the 1st (energy) and 2nd (exergy) laws of thermodynamics. A 0.5234 kW rating heat pump prototype system with a PV/T-TC area of 3.5 m2 was built and tested under the real conditions of Karachi, Pakistan, and a simulation model was developed via MATLAB to predict the annual energy performance. The experimental results show that the PV/T-TC system's mean daily electrical, thermal, overall energy and exergy efficiencies were 14.08%, 60.12%, 74.20%, and 18.12%, respectively. The numerical results reveal that a PV/T-TC assisted solar heat pump system can generate 303.51 kWh of electricity and 3213.12 kWh of thermal energy annually. The annual average COP of the hybrid refrigerant-based PV/T-TC system is 5.68. According to the comparison of economic performance between the PV/T assisted direct-expansion heat pump system and PV/T-TC assisted direct-expansion heat pump system, the hybrid refrigerant-based PV/T-TC assisted direct-expansion heat pump system has a payback period of 5.20 years, whereas the refrigerant-based PV/T assisted direct-expansion heat pump system has a payback period of 7.15 years. The experimental data is consistent with the simulation outcomes, with an average relative error of 3.30%. [Display omitted] [ABSTRACT FROM AUTHOR]

Solar energy conversion technologies attain enormous attention to create more efficient energy production sources to meet the current world's demand. The solar thermal conversion system converts solar energy to heat, and the receiver tube is crucial for achieving high photo-thermal conversion efficiency. The absorber coatings with high solar absorptance at normal and wide incidence angles of solar radiation improve the performance of concentrated and non-concentrated solar thermal systems. To achieve high photo-thermal conversion efficiency in the solar thermal conversion system, a novel spinel structured cobalt-rich transition metal oxide-based absorber coating was developed by a cost-effective wet chemical route. The developed absorber coatings with sub-micron scaled surface protrusions with porous structure (size 0.75 μm) exhibit an excellent spectral selectivity (α/ ε = 0.91/0.13). In addition, the coatings show an excellent wide angular solar absorptance of 0.97–0.96 at incidence angles of 10°–40°. Extensive characterization has been carried out to analyze the structural properties of the absorber coatings and correlated to the spectral selectivity and wide angular solar absorptance property. The stability of the absorber coating at 400 °C for 100 h in an open-air atmosphere assessed by the performance criteria (PC) function value of 0.015 indicates the ability of the optimized absorber coatings to employ in solar thermal systems. [Display omitted] [ABSTRACT FROM AUTHOR]

Concentrating solar power (CSP) plants that used thermal parabolic trough collectors (PTC) are the most suitable technology in the clean power production. Several efforts have been done for enhancing the performance of PTCs. In this research, a parabolic trough collector-thermoelectric generator (PTC-TEG) hybrid solar system is proposed. In this system, two approaches to enhancing efficiency were implemented and conducted, and its thermal and electrical performances were experimentally investigated. The first, the heat transfer fluid (HTF) into the absorber tube was pressurized using a pressure control unit under relative pressures of 0.3 and 0.5 bar. The second, it was proposed that a TEG module was installed on the backside of the reflector for generating the additional electrical power from the absorbed solar radiation by it. These two approaches were implemented on a parabolic trough collector was equipped with polar N–S axis and E-W tracking mechanism. The results of the thermal performance evaluation of this system showed that the thermal efficiency increased 6.88% and 14.64% by increasing the HTF pressure of 0.3 and 0.5 bar relative to conventional PTC, respectively. The generated electrical power by a series array 70 TEG module has a 0.96–1.11% contribution to the increasing total efficiency of the proposed system. By increasing the pressure of the working fluid, the rising rate of working fluid temperature increased. Generally, the total efficiency of the proposed hybrid solar system 15.75% enhanced. [ABSTRACT FROM AUTHOR]

Parabolic trough solar collector (PTC) system with a flat receiver is widely used in concentrating photovoltaic/thermal (CPV/T) systems, where the flat receiver and PTC are the key components to exchange the solar radiation into heat or electricity. The optimal design and geometric structure of PTC using a flat receiver are essential to achieve high efficiency and energy yield for CPV/T systems. In this paper, a mathematical model of PTC with the flat receiver was developed to investigate and evaluate optical properties based on Monte Carlo Ray Tracing method, whose feasibility and reasonability was verified by the comparison between the model and published literature's results. An innovative method was proposed to calculate the minimum width by vectoring. The optimal geometric design for the same geometrical focusing ratio was derived through simulations based on MATLAB. The influence of geometric parameters and errors were discussed, which showed that the optical performance has large variations in local concentration ratio (LCR) at the center of the flat receiver and is superior at rim angles of 75°–90° under ideal conditions with the same geometric focusing ratio. The errors were found to have a significant effect on the optical performance, especially on the peak LCR. [ABSTRACT FROM AUTHOR]

Solar water heating has turned out to be a common technique adopted for achieving the development of a sustainable and renewable energy goal. However, the intermittent nature of solar energy confines water heating during nighttime and dusky hours. Thus Direct Expansion Solar-Air Source Heat Pump (SAHP-DX) is used for extracting both the solar energy and ambient thermal energy source in an effective method. In this experimental work, a dual-source heat pump is designed to operate throughout the day for water heating applications in a sustainable manner. Performance of SAHP-DX water heating system in Solar Air Source Mode (SAHP-DX-SAM) and Air Source Mode (SAHP-DX-AM) are experimentally investigated and compared. Energy and exergy performance characteristics are evaluated and compared during summer and winter days. The average coefficient of performance (COP) of SAHP-DX-SAM is comparatively higher than SAHP-DX-AM by 17.6%. Cycle average power consumption and heating time of SAHP-DX-SAM is reasonably lower than SAHP-DX-AM by 16.9% and 23.6%. Exergy destruction from SAHP-DX-SAM is considerably lower than SAHP-DX-AM by 3.4%. Hence the current research shows the recommendation and implementation of SAHP-DX for water heating applications in hot regions for effective and rapid heating. [Display omitted] • SAHP-DX system consisting of dual source evaporator. • Thermal performance of SAHP-DX system was experimentally evaluated. • Impact of I g , T a and T w on system performance are investigated and compared. • COP of SAHP-DX system can reach 5.1. • Prove the feasibility of SAHP-DX for water heating in hot regions. [ABSTRACT FROM AUTHOR]

Steel metallurgy accounts for about 7 % of global greenhouse gas emissions and its decarbonation is a major issue. The direct reduction of iron ore with H 2 using concentrated solar heat offers a carbon-free route for the iron metallurgical process. Such a solar process for clean ironmaking has never been implemented before. This study aims to investigate the reaction characteristics of direct iron ore reduction and further proposes a first experimental demonstration of direct reduced iron production in a packed-bed solar reactor under real solar irradiation. Fe 2 O 3 reduction with H 2 was first studied by thermogravimetric analysis to unravel the effect of temperature, H 2 mole fraction, and particle size. The reaction rate increased with temperature (400–800 °C) and H 2 mole fraction (25–75 %), and the reaction reached completion with an initial conversion starting from 370 °C. An activation energy of 38.5 and 30.4 kJ/mol was determined for commercial Fe 2 O 3 and iron ore, respectively. The size of iron ore particles after pellets crushing (in the range 0.25–2 mm) did not significantly affect the reaction rate. However, fine micron size powder with low bulk density showed improved conversion rates. Finally, the reduction process was demonstrated in a solar-heated packed-bed reactor up to 1000 °C, confirming the feasibility of renewable iron production from complete ore reduction at moderate temperatures (starting above 400 °C), and thus paving the way toward decarbonation of the iron and steel metallurgical industry. [Display omitted] [ABSTRACT FROM AUTHOR]

The energy yield of solar thermal installations is influenced by local climatic conditions, heating demand, and the efficiency of the system. These factors are affected by uncertainties arising from natural variations and a lack of knowledge. Designers typically address these uncertainties by oversizing the collector area. However, this practice usually leads to high costs, low efficiency, and short service lifetimes of the system. This paper proposes a robust sizing methodology for the solar thermal system used for service hot water preparation in a case-study hospital with a daily average hot water consumption of 8.69 m3. This novel approach incorporates uncertainties through probabilistic simulations, assessing the system's reliability in achieving a 70% solar fraction design goal. The simulations reveal a mere 22% confidence in the initial deterministic design concerning the solar target and emphasize the importance of thermal insulation, temperature control, and collector cleaning as key factors to reduce performance variability. Although the final revised design outcome requires a 15% increase in the collector area compared to the initial scenario and stricter specifications for control components, pipe insulation, and valve maintenance, it achieves a 90% reliability. In addition, annual carbon emissions and levelized costs of hot water production can be reduced by 18% and 13%, respectively. • Solar thermal hot water systems play a key role in the sustainability of hospitals. • Standard design practices result in unreliable installations regarding solar goals. • Robustness of the solar system design improved through uncertainty analysis. • Quality insulation, control, and maintenance minimize operational variability. • The design methodology proposed is simple to implement and minimizes project risks. [ABSTRACT FROM AUTHOR]

Thermal energy storage is a key issue in efficient energy system applications, especially in renewable energies. In this respect, phase change materials (PCM) have attracted interest as an active solution for efficient energy management, particularly in the building sector. This paper presents a modelling of a PCM thermal battery in solar system assisted by heat pump. The storage stores the heat produced by unglazed solar panels (Batisol®) and releases it into a heat pump. Then this heat is sent to two other PCM storages. In this way, the low-temperature heating and domestic hot water needs of a commercial building in winter are met. The storage consists of a block of PCM contained between two plates of heat transfer fluid. It acts as a plate heat exchanger that can be charged and discharged simultaneously. The objective of the study is to dynamically simulate the thermal behaviour of this storage for different hot inlet temperature profiles. A rectangular profile is used to validate the model using experimental results. Then, a solar system assisted by heat pump and three PCM storages is dynamically simulated. This 2D model would be useful to validate a simpler model for optimising the operational parameters of the system. • PCM thermal battery acts as plate heat exchanger which can be charge and discharge simultaneously. • PCM storage model is validate using experimental results. • Three different PCM are chosen according to the temperature levels of each application. • A solar system assisted by heat pump has been dynamically simulated to supply DHW and low-temperature heating requirements. • No auxiliaries are required to meet the building's needs. [ABSTRACT FROM AUTHOR]

Thermoelectric generator (TEG) can utilize solar heating to generate electricity without any fossil fuel consumption. However, conventional solar driven TEG fails to achieve high efficiency power generation for 24-h, due to the losing of solar concentration at the hot end and additional cooling capability at the cold end. Therefore, a novel TEG system with the combination of solar concentration, greenhouse and radiative cooling is proposed. With the aim to significantly increase the temperature of hot end, a dish-type concentrator is introduced to concentrate solar radiation and a greenhouse seals up heat. Radiative cooling panel is used to decrease the temperature of cold end, which can realize temperature differences of TEG at night. The eight-day outdoor experimental test indicates that the thermoelectric system achieves a maximum temperature difference of 47.5 °C and a voltage output of 1293.8 mV. The system attains the average power outputs of 3.6 W/m2 on sunny and 0.16 W/m2 on cloudy. Moreover, even at the nights of high humidity and low temperature, the system also achieves a maximum power output of 0.08 W/m2, which can enable continuous power generation throughout the day. This innovative TEG system presents a viable strategy for powering small-scale devices in remote areas. [ABSTRACT FROM AUTHOR]

Due to the seasonality of solar energy, achieving 100 % of annual solar fraction for domestic hot water (DHW) production is only possible by greatly oversizing the collector area of a solar system, thus creating a significant energy surplus in summer. This simulation study investigates the possibility of using this surplus to promote space heating during winter, in a moderate South European climate, to try achieving a total solar fraction of 100 %. Priority is given to the DHW reservoir, diverting the excess heat to an additional large-capacity seasonal thermal energy storage (STES) reservoir. The best configuration for the number of collectors and STES tank volume was assessed through a parametric study, to reach a compromise between a high solar fraction and a reasonable system efficiency. The results showed that a system with 10 m2 of solar collectors and a 30 m3 STES tank or, alternatively, 20 m2 of collectors and a 20 m3 tank achieved the desired solar fraction and efficiency for the chosen building and local climate conditions. A comparison with the literature shows that this strategy can achieve better results, requiring less collector area and storage volume. [ABSTRACT FROM AUTHOR]

Efficient utilization of solar energy could effectively alleviate dependence on fossil fuels and contribute to the ambitious target of carbon neutrality. This study first proposes a novel partially covered parabolic trough photovoltaic thermal (PCPTPVT) collector to efficiently exploit solar energy. The thermodynamic model and iterative procedure are built based on the thermal resistance circuit method. Energy, exergy, exergoenvironmental, and exergoeconomic analyses are conducted to evaluate the thermodynamic, environmental, and economic performances of the novel PCPTPVT collector. Besides, multi-objective optimization of the tradeoff between cost-effectiveness and environmental friendliness is also carried out. The results show that 12.42% of the solar energy beamed on the PCPTPVT is converted into solar electricity and 61.38% of that is transformed into thermal energy for heating fluid. The electrical and thermal efficiencies of the PCPTVPT can reach 27.9% and 64.3%, respectively, and the energy and exergy efficiencies have notable improvements of 11.11% and 6.19% when the solar irradiation changes from 300 W/m2 to 1100 W/m2. The unit exergy emissions of CO 2 , NO X , and SO 2 of the PCPTPVT under design conditions are 18.39 g/kWh, 117.8 mg/kWh, and 149.4 mg/kWh, and life cycle pollutant emission reductions reach 136.08 t, 971.92 kg, and 1125.35 kg, respectively. [ABSTRACT FROM AUTHOR]

The compound parabolic concentrator is a non-imaging concentrator that can concentrate solar radiation without tracking system. However, as the concentration ratio increases, the maximum half acceptance angle and the effective working hours decrease. To increase the effective working hours at high concentration ratio, a tracking solar collector is proposed that integrates the compound parabolic concentrator and flat microchannel tube. This new solar collector can track solar radiation by rotating the two reflective surfaces around their respective starting lines. A two-dimensional model is developed for the irradiation concentration of the tracking compound parabolic concentrator. For the geometry of the compound parabolic concentrator and solar irradiant angle, the optimal rotation angles of the reflective surfaces are determined to minimize the irradiation loss. The effects of the rotation angle of the two reflective surfaces on the concentration performance are simulated. The simulation results show that in the tracking mode, the averaged heat flux on the surface of the absorber can reach 7.61 kW m−2 when the concentration ratio and truncation ratio are 8 and 0.5, respectively. Even when the incident angle of solar irradiation is 30°, the averaged heat flux is still 5.12 kW m−2. Compared with other kinds of reflector, the concentration performance of the compound parabolic concentrator is merely influenced by the tracking error. The positive and negative tracking errors lead to different declining rates of normalized optical efficiency and the influence of positive tracking error is more acceptable. [ABSTRACT FROM AUTHOR]

Maintaining a suitable temperature in the greenhouse in the cold season requires the assistance of the heating system, and renewable energy is advocated to replace traditional energy for greenhouse heating. To adjust the microclimate of the greenhouse, this study proposed a multifunctional air conditioning system that utilizes surplus air thermal energy (SATE), and the heat balance is used to calculate the system performance required for heating. Experimental results show that the system increased the minimum air temperature at night by 2.8 °C, and it also improved in continuous cloudy days, making the greenhouse temperature and humidity at night closer to suitable conditions, and the air temperature is more uniform in time and space. The provided heat energy and heat transfer rate of the multifunctional air conditioning system were 168.8 MJ/d and 4289 W, respectively, which were 95% of the Chinese Solar Greenhouse (CSG) heat demand and 50% of the CSG maximum heat load. Adjusting the temperature difference between water and air can also improve the heat release capacity of the system, and the system still has great potential. The multifunctional air conditioning system heating CSG is feasible, and the system is environmentally friendly and energy-saving, suitable for all kinds of greenhouses, and will have broad application prospects. [ABSTRACT FROM AUTHOR]

Remote locations, small communities, and weather prohibit the operation of piped sanitary sewers in many Alaska Native Villages (ANVs). Research was conducted to understand the technical feasibility of installing anaerobic digesters (ADs) in remote ANVs which would be heated by solar thermal collectors. Biochemical methane potential (BMP) assays were conducted to understand the effect of freezing and thawing on methanogenic activity of synthetic human feces. BMPs were frozen at −20 or −80 °C for 7 days and then incubated at psychrophilic (20 °C) or mesophilic (37 °C) conditions. Psychrophilic BMPs frozen at −20 or −80 °C yielded 453 ± 119 and 662 ± 77 mL CH 4 /g VS, respectively. Mesophilic BMPs frozen at −20 or −80 °C yielded 337 ± 59 and 495 ± 63 mL CH 4 /g VS, respectively. Freezing caused a lag period, but ultimately many of the assays reached yields similar to or even greater than the baseline, unfrozen assays. Monthly solar radiation and air temperature data were used to identify the number of solar thermal collectors that would be required to supplement heat energy to operate the ADs in several locations. Alaskan subarctic locations receive enough solar thermal energy in summer months to support seasonally operated, psychrophilic ADs. [Display omitted] [ABSTRACT FROM AUTHOR]

Process steam is an important product in the industrial sector but the traditional steam boiler will lead to tremendous fossil fuel consumption and carbon emissions. The non-concentrating solar collectors have a huge potential for process steam generation but their application potential has not been fully explored. In this paper, a high-efficient evacuated flat plate solar collector used for direct steam generation is proposed. Its thermal performance in both direct steam generation mode and pressurization water mode is presented via experiment test and a validated numerical model. The results indicate that the direct steam generation mode can obtain a 10% enhancement (absolute value) of the thermal efficiency compared with the pressurization water mode. The thermal radiant losses of the solar collector can be suppressed and the heat transfer coefficient of the working fluid can also be elevated. Furthermore, a dual-mode evacuated flat plate solar system is proposed to produce thermal energy for space heating in the heating season and generate steam in the non-heating season, thereby solving the solar seasonal mismatch problem for the traditional solar thermal heating system. The comparison with the state-of-the-art study manifests that the dual-mode system proposed in this paper has better performance all year round. [Display omitted] [ABSTRACT FROM AUTHOR]

To utilize effectively passive solar energy for heating buildings, an innovative building envelope is proposed, and its superior performance is for the first time experimentally demonstrated by constructing and testing its full-scale model. The proposed envelope comprises a dynamic Trombe wall incorporating phase change material (PCM). Its salient feature and novelty are its innovative multi-panel solar collector-storage wall and the ability of each panel to independently rotate about its vertical axis. One face of each panel is cladded with PCM, and in a typical 24 h cycle, during sunshine hours, this face is turned towards the incident solar irradiation and the rest of the time towards the conditioned space. The thermal performance of the proposed envelope is compared with that of a companion envelope having a traditional static Trombe wall with the same amount of PCM and wall geometry. The results show that compared to the traditional envelope, the new envelope regulates the thermal load more evenly by preventing large temperature swings, it reduces heat loss during the solidification phase of PCM by 29% and is overall 20% thermally more efficient. These benefits can result in energy saving from non-renewable energy sources over the design life of the building. [ABSTRACT FROM AUTHOR]

In this study, a distributed aerobic composting system was proposed and simulated assisted by a solar photovoltaic thermal (PV/T) heat pump. The PV/T heat pump was adopted to provide the electrical energy and heat energy required by the aerobic composting system. In addition, the area of solar photovoltaic panels required for compost fermenter at different volumes was calculated, and the effects of ambient temperatures, wind speeds and solar radiation intensities on the performance exhibited by the hybrid system were investigated. As indicated from the result, when the temperature of the composting tank was maintained at 60 °C, the C/N ratio can be reduced to 11.5:1 and the GI can reach 101.7%, satisfied the compost maturity standard. Moreover, as the ambient temperature decreased, the heat loss of the composting system and the energy consumption of the hybrid system increased. The wind speed did not significantly impact the comprehensive performance exhibited by the system. Under the average solar radiation of 600 W/m2, a maximum of 10 m2 PV/T panels could be installed on the top of a standard container, and a maximum of 6000L of aerobic composting system could be installed within the container. Accordingly, the 6000L composting system coupling with PV/T heat pump could generate 85.64 kWh electricity in one period (10 days) without consuming energy. [ABSTRACT FROM AUTHOR]

The heat pipe evacuated tube solar collectors were widely used in building heating. The defects in the assembling process caused by the roughness of solid materials have a severe effect on the thermodynamic performance of the solar collector. To enhance the efficiency of the solar collectors, an improvement approach by filling the gaps in the interface between assembling structures using thermal interface materials is proposed. The interface between heat pipe and fin is a major contributor to the heat resistance in collector tubes, thus affecting the utilization efficiency of solar energy. Three thermal greases were selected, and then the interface after filling the gaps was characterized and analyzed. To verify the effectiveness of the new improvement approach, two experimental setups including a solar collector and a solar heating system were built. Experimental results show that the average collection efficiency of the solar collector increases by 4.8% compared with that of the unprocessed one. Moreover, the optimization of the interface enhances the sensitivity and response speed of the collector on solar irradiance, and shortens the startup time by 27.2% of the solar heating system. The work provides a promising way to upgrade the solar collector with heat pipe evacuated tube. [Display omitted] • An improvement approach for the solar collector by optimizing the interface of assembling structure is proposed. • Contact heat transfer of assembling structure is considered in thermal model. • Introduction of thermal grease in solar collector enhances its thermodynamic performance. • Improving assembling interface increases collector sensitivity and start speed. • Effectiveness of the new approach is verified by two experimental setups. [ABSTRACT FROM AUTHOR]

This paper considers three configurations of air source heat pumps and building-integrated photovoltaic (BIPV) systems in a solar house. This study evaluates energy efficiency and flexibility when interacting with a smart grid. The reference case is a 5 kW BIPV system on the roof with a separate air-source heat pump water heater (HPWH). In the two more novel options we have: first, a 5 kW BIPV/thermal (BIPV/T) roof system where the heated air from the BIPV/T system is ducted to the air source of the HPWH, which also contains integrated thermal storage (hot water); in the second case we have an attached solarium with a 5 kW semi-transparent photovoltaic façade, with the solar heated air in the solarium connected to the air source of the HPWH with integrated water thermal storage. The three cases are modelled with an explicit finite difference thermal network model, and energy performance is determined and compared over a typical heating season in Montreal, Canada. The energy flexibility potential of the options is compared for different scenarios, such as heating the thermal water storage during the daytime (e.g. using the solar heat in the novel options) and using it for space heating during the time that the grid is under stress (and may have price incentives). Results show that the second novel case utilizing the solarium air as the source of the heat pump resulted in an over 80% energy use reduction relative to the reference. In comparison, the BIPV/T configuration had around 20% reduction compared to the reference case. The tank volume and solarium size had the highest impact on the flexibility of the system. Optimal sizes for the tank volume were typically between 300 and 600 L for the house with a floor area of 116 m2. • Analyzed BIPV/T scenarios using solar heat to supply heated air to a heat pump. • Compared the energy and flexibility of a ducted BIPV/T and a solar heated solarium. • Novel passive solar STPV covered solarium had lowest energy consumption. • Maximized energy flexibility using a parametric analysis to size key components. • Integrated thermal storage had highest impact on maximizing energy flexibility. [ABSTRACT FROM AUTHOR]

In this paper, a floating multi-effect solar still using parabolic concentrators to directly heat rising seawater film is investigated. The novel desalination device integrates solar still and two concentrators as a whole, which avoids the installation of a heat exchange pipeline and can float on the ocean to produce freshwater. The floating still consists of a front parabolic concentrator, a rear parabolic concentrator, and several embedded distillation cells. The distillation cell is composed of a hydrophilic wick, a condensing plate, and a narrow space in between. The parabolic concentrator greatly increases the solar heat to improve the temperature gradient and enhance the phase transition and diffusion process of water vapor. During desalination, the rising seawater film for evaporation is formed in the hydrophilic wick by capillary force. Through indoor steady-state experiments, some key parameters such as solar irradiance and incident angle on the temperature, water yield and gain output ratio (GOR) of the still were studied. Results indicate that the maximum temperature gradient in the 5-effect still can reach 48.5 °C. Under a 900 W/m2 irradiation, the water productivity and GOR are 2.7 kg/m2/h and 2.2, respectively. Additionally, outdoor experiments show that the daily freshwater reaches 4.7 kg/m2 with an average irradiation of 543 W/m2. • A floating multi-effect solar still coupled with parabolic concentrators. • The GOR of the still reaches 2.2 under stable state. • In the clear weather, the freshwater yield achieves 4.7 kg/m2/day. [ABSTRACT FROM AUTHOR]

The efficiency of municipal solid waste to energy incineration plant is limited due to the higher amount of moisture content in the feedstock and huge heat loss. An innovative configuration is proposed in the present study to increase the performance of incineration plant. The new design consists of the integration of a solar thermal system with the incineration plant, so that the steam exiting the superheater of the municipal solid waste (MSW)incineration boiler is further heated by solar thermal system to increase its temperature and quality before entering the steam turbine. In addition, the flue gas is used to drive an iso-butane organic Rankine cycle to produce power that is utilized for hydrogen and freshwater production with the help of a proton exchange membrane electrolyzer and reverse osmosis system, respectively. Through a parametric analysis, the effect of major parameters on the performance of the proposed system is studied. The energy, exergy, and exergo-economic investigations are performed to access the system efficiencies, exergetic cost rates, sustainability index and total exergy destruction rate. The results show that the energy and exergy efficiencies of the integrated system are almost 21.34% and 16.64%, respectively, while thermal and exergy efficiencies of the MSW incineration plat are 37.35% and 35.22%, accordingly. The exergo-economic evaluation concludes that the exergy destruction rate of the system is 42965 kW with the rate of exergetic cost and total cost rate of 542 $/hr and 665 $/hr respectively. The sustainability index of the proposed system is calculated to be nearly 1.64, while fresh water and hydrogen production rates are 26.96 kg/s and 2.87 g/s, accordingly. In the end, the solar integrated waste-to-energy plant can provide multiple outputs simultaneously after adding the waste heat recovery system and the proposed system is theoretically feasible from the results of thermodynamic, economic, and environmental analysis. [Display omitted] • Innovative solar integrated WtE incineration plant with heat recovery system. • Exhaust flue gasses utilized for hydrogen and freshwater production via ORC. • System was evaluated by exergoeconomic analysis for detailed investigation. • Sustainability index used for evaluating environmental performance. • Single flow chart of exergy destruction rate, exergy cost and total cost rate. [ABSTRACT FROM AUTHOR]

Electrochromic (EC) glazing provides a promising solution to actively adjusting the sunlight and radiant heat through windows in response to building visual and thermal environmental requirements, and control strategies play a critical role in the application of EC technology in buildings. However, there is a conflict between the visual and thermal environmental requirements for EC regulation during a cooling season. To solve this problem, this paper developed a predictive control strategy for EC glazing. It was achieved based on two theoretical models which could predict the energy performance of EC glazing at different tint states, including the solar radiation heat transmitted through the glazing and lighting energy consumption. The optimum glazing state was determined based on real-time minimized energy consumption. Study results showed that the predictive control strategy outperformed the rule-based control strategy, with percentage energy saving of an office room in Beijing, China from 8.04% to 12.78% over an entire cooling season. In addition, the paper evaluated the energy-saving of using EC glazing under the predictive control strategy in 28 Chinese cities. The results indicated that EC glazing was highly applicable in most of cities with energy saving from 2.35 kWh/m2 to 5.04 kWh/m2 over an entire cooling season. • A predictive control strategy for EC glazing was developed. • Theoretical models were established to predict the EC glazing energy performances. • Real-time minimized energy consumption determined the optimum EC glazing state. • Balance between the visual and thermal environment requirements was achieved. • The energy-savings of using EC glazing in 28 Chinese cities were assessed. [ABSTRACT FROM AUTHOR]

Improving efficiency, controlling cost and reducing the temperature of solar cells are great challenges for linear concentrated photovoltaic/thermal systems (LCPV/T). In this work, we report a new design with a linear Fresnel lens as the primary optical element and an additional multi-functioned solar collector tube as the secondary optical element. With such design, the low-cost solar collector tube acts multiple roles simultaneously, i.e., lens, spectral beam-splitting filter and heat collector. It was demonstrated that the addition of such multi-functional solar collector tube in LCPV/T system can significantly increase the irradiation uniformity and decrease the average temperature of photovoltaic (PV) module under the same thermal condition, which results in the improved electricity output performance of PV module. Under the solar irradiance and ambient temperature for a typical daytime, the average electrical, thermal and total energy efficiencies of the proposed system are 11.39%, 64.72% and 76.11%, respectively. Our work should be of guidance for the design of LCPV/T system with high efficiency, long-life and low cost. [Display omitted] [ABSTRACT FROM AUTHOR]

The porous solar-driven interfacial evaporator has attracted substantial interest because of its high performance in converting solar energy into heat for water evaporation. However, the effect mechanism of porous structure (e.g., pore size and porosity) on water evaporation efficiency remains controversial and unclear, which largely restricts the design of high-performance solar evaporators. Herein, a porous solar interfacial evaporator with controllable porous structure was presented by integrating carbonized carboxymethyl cellulose with antimony doped tin oxide (ATO) powder (ATO-C). The experimental results revealed that reducing the porosity of ATO-C could reduce heat loss for heating the water inside channels, thereby improving the evaporation efficiency. Moreover, the synergistic light absorption of carbonized cellulose (in the visible region) and ATO (in the near-infrared light region) enable ATO-C to harvest a large fraction of sunlight (more than 98%) for water evaporation. On the basis, the ATO-C exhibited a water evaporation rate up to 1.44 kg m−2 h−1 under one solar irradiation with an evaporation efficiency of 90.38%, outperforming most previously reported solar evaporators. The current work clarifies the effect mechanism of porosity on evaporation efficiency, which helps to develop high-performance solar interfacial water evaporators. [Display omitted] [ABSTRACT FROM AUTHOR]

In this paper, a multi-heat source complementary system of combined drying was designed, which used three heat sources, solar energy, heat pump and combustion furnace, with two drying technologies, hot air drying and vacuum drying. It had the advantages of saving drying energy consumption and improving product quality. The simulation model of the multi-heat source complementary system of combined drying was established based on TRNSYS. Using the meteorological parameters of Xi'an as input, and a comparison of experiments and simulations verified the correctness of the model. The overall error is between 2.0% and 8.9%. The model predicted the system's performance parameters, operating energy consumption, and operating costs. The results show that the operating energy consumption of the system is affected by season, with solar energy and heat pumps being more significant. The average monthly COP of the heat pump system is between 2.4 and 3.62, and the COP of the system decreases after the addition of auxiliary electric heating. The annual operating cost of the multi-source complementary heating mode is reduced by the maximum of 42.6% compared with other heating modes, its carbon emission is reduced by the maximum of 33.1% compared with other heating modes, and the minimum payback period is 1.64 years compared with different heating modes, thus reducing energy consumption and cost. [ABSTRACT FROM AUTHOR]

Hydrothermal processing of agave was performed using a batch solar reactor designed to operate with a coupling method where a concentrated solar system provides heat. This work analyzes the performance of a reactor and the main characteristics of the products at different operational parameters: temperature, biomass concentration and holding time under subcritical conditions. Experimental findings demonstrate that the solar heated reactor prototype allows reaching maximum reaction temperatures of 300 °C with stable pressures. Low heating rates reduced the propensity of the system to leak, which prevented variations in pressure throughout experiments. The most favorable conditions to improve the yields (up to 28%) and properties of the oil produced were 300 °C and no holding time at peak temperature (τ = 0 min), and an average constant direct normal irradiation of 745 ± 47 W/m2. [Display omitted] [ABSTRACT FROM AUTHOR]

With the widespread application of solar-energy-air-source heat pump composite heating, optimizing the regulation of air temperature in heating zones, enhancing system thermal comfort, and reducing energy consumption have become crucial. To ensure residential comfort while minimizing HVAC system energy costs, a control method combining guided policy search (GPS) with model predictive control (MPC) is proposed for composite heating systems. This method replaces state estimation in MPC with policy search and substitutes the offline trajectory optimization used in guided policy search with MPC, thus integrating the strengths of both approaches. This strategy not only improves control precision but also reduces energy consumption and enhances system robustness. The GPS-MPC control algorithm was validated against reinforcement learning and MPC. A simulation model was developed and validated on a real physical platform. Simulations compared the control effects of on-off control and MPC on pump frequency, flow rate, stratified thermal storage tank temperature, component, and system energy consumption. The data results indicate that the GPS-MPC algorithm offers superior predictive accuracy, efficiency, and robustness in composite heating control systems compared to conventional methods. Under the GPS-MPC strategy, indoor temperature fluctuations, pump frequency response speed, and energy consumption were significantly improved, with temperature fluctuation limited to only 0.8 °C, and the system achieving energy savings of over 12 %. [ABSTRACT FROM AUTHOR]

Industrial processes share a relevant portion of global energy consumption. A large variety of high energy-demanding industrial processes need hot air in the medium temperature range, provided by natural gas combustion or by electricity. Hot air is used as a medium in a large variety of processes such as drying, curing, and thermal treatments of several products and materials. Heat can be provided by solar thermal technologies aimed at the sustainable industry. Non-concentrating flat plate type solar collectors can directly heat air up to 100 °C while higher temperatures can be achieved using linear concentrating technology. In this study an innovative system using linear Fresnel collectors directly provides hot air for the industry up to 350 °C, avoiding the need for liquid heat transfer fluids. Accordingly, the installation is simplified, and lower installation and maintenance requirements are expected compared to other solar technologies. The present studies provide an energetic and economic analysis of the concentrating solar air heater, considering a medium-scale benchmark as a reference case in representative European locations. The results indicate that the solar technology here presented can be economically competitive with conventional natural gas heating, having a huge potential for fossil fuel source replacement in hot air based industrial processes. [Display omitted] [ABSTRACT FROM AUTHOR]

Zhengzhou of Henan province is an important agricultural production base. To improve the performance of the combined drying system and promote the development of agricultural products in Zhengzhou area, a solar assisted multi-source heat pump (SMSHP) drying system was proposed based on a traditional solar assisted air source heat pump (SASHP) drying system. The simulation models were developed for the air source heat pump (ASHP), SASHP, and SMSHP drying system respectively. The coefficient of performance, energy consumption and specific moisture extraction rate of the drying systems under different seasons were analyzed. Moreover, to validate the simulation models, an experimental platform of the combined drying system was designed and set up, and the experimental tests were carried out on the ASHP, SASHP, and SMSHP drying system. The simulation results revealed that the SMSHP drying system had lower energy consumption, higher coefficient of performance and specific moisture extraction rate than that of the SASHP drying system. The most significant performance enhancement was observed in spring, where the SMSHP system demonstrated a 22.69 % increase in coefficient of performance, a 19.2 % increase in specific moisture extraction rate, and a 16.11 % decrease in energy consumption compared to the SASHP drying system. Comparing with the experimental data, the simulation model errors of the energy consumption, coefficient of performance, and specific moisture extraction rate of the SMSHP drying system were 3.19 %, 0.28 %, and 2.27 %, respectively. Therefore, the accuracy of the simulation results was confirmed. To better calculate the heat provided by the solar collection system, the concept of the tank heating guarantee rate was first introduced, and it was found to be more scientific than the solar energy guarantee rate. At last, The economic and environmental benefit of the drying systems were analyzed during the life cycle, and the SMSHP drying system exhibited better comprehensive performance than the SASHP drying system. This paper provides valuable insights into the comprehensive utilization of solar energy and the control logic of solar assisted air source heat pump combined drying system under different seasons. [ABSTRACT FROM AUTHOR]

Vacuum-photovoltaic glazing, renowned for exceptional thermal insulation and solar energy utilization, faces limitations in its adaptability to varying seasons. While it effectively reduces heat transmission into indoor spaces during summer, it becomes detrimental during winter. To address this challenge, this study introduces an innovative solution: vacuum-photovoltaic-thermoelectric (VPT) glazing, which integrates vacuum, photovoltaic and thermoelectric cooling/warming technologies. The theoretical models were developed and validated through WINDOW and Fluent simulations. A comparative analysis is conducted considering thermal performance under various environmental parameters. The results demonstrate that VPT glazing exhibits enhanced thermal performance, with interior glass temperature decreased by 3.0–9.6oC in summer while increased by 2.5–6.2oC in winter, accounting for ∼55.0 % reduction in air-conditioning load. Compared to vacuum-photovoltaic glazing, VPT glazing reduces the coupling U -value from 7.88 to 5.87 W m−2 K−1 in summer and increases from −0.31 to 2.61 W m−2 K−1 in winter. The solar heat gain coefficient decreases from 0.37 to 0.30 in summer and increases from 0.24 to 0.29 in winter. These results demonstrate the effectiveness of VPT glazing in adapting to different seasons and achieving better thermal environment performance. This study provides insights into VPT glazing design for environmental adaptation and offers implications for future research and applications in energy-efficient building technologies. [Display omitted] • A vacuum-photovoltaic-thermoelectric glazing is introduced for thermal adaptation. • Ray-tracing-based optical and heat transfer models are developed and validated. • Interior glass cools by 3.0∼9.6 °C in summer and warms by 2.5∼6.2 °C in winter. • Solar heat gain coefficient is reduced from 0.46–0.75 to 0.18–0.39. • PVT glazing enables ∼55.0 % decrease in air-conditioning load transmitted through. [ABSTRACT FROM AUTHOR]

Carbon nanotube (CNT) heat absorbers were developed to enhance the direct solar heating of liquid tin as a heat-transfer fluid in ground solar receivers. To improve the thermal transfer of absorbed solar energy to tin, absorbers reinforced with carbon black (CB) were fabricated by compression molding. As the compressive strength increased, the CNT absorber formed denser nanotube arrays, which increased the thermal conductivity by 1.68 times. Increasing the CB content further enhanced the conductivity by 1.19 times through grape cluster-like structures. The thermal properties of CNT absorbers predominantly depend on the compressive strength and CB content, and a correlation is proposed for predicting the conductivity. The most effective absorber was prepared at 50 kPa with a CB/CNT ratio of 1.0. The heat absorption characteristics of the solar receivers (50 mm i. d., 60 mm high) with the prepared CNT absorbers were determined. Tin temperatures with CNT absorbers rose more steeply than in bare tin systems, exhibiting a higher temperature increase per irradiance. The efficiency of the bare tin system improved from 24.8 % to 45.4 % using absorbers at 50 kPa and to 46.4 % using a CB/CNT ratio of 0.75 at 20 kPa. Under wind-free conditions, the receiver with the highest thermal conductivity achieved 67.7 % efficiency, a 1.69-fold increase over a tin-only receiver. This study confirmed that the improved thermal conductivity of the CNT absorbers significantly enhanced the receiver efficiency by facilitating rapid solar-energy transfer to liquid tin. [Display omitted] [ABSTRACT FROM AUTHOR]

As the global population ages, the demands imposed by medical treatment and care for the elderly are becoming increasingly pressing. To reduce energy consumption and systemic defects in the process of integrating medical treatment and care for the elderly, the authors of this study designed a highly efficient, flexible and low-carbon combined cooling, heating, and power (CCHP) system for the integration of medical and nursing complexes by using a multi-level model of optimization. The complex was modeled in DeST software to obtain the cooling and heating loads, and the general algebraic modeling system software and mixed-integer linear programming (MILP) were used for the collaborative optimization of the choice of equipment, capacity allocation, and operational strategy. The results showed that the proposed system could reduce the total consumption of electric power by 40.95 % when a semiconductor wall was installed on floors 8–12 of the complex for elderly care. The energy management strategy of the system was also optimized by using the vehicle-to-building subsystem in a novel wind–solar–storage and heat pump-based combined cooling, heating, and power system. The rates of reduction in emissions of CO 2 and NO x , and the rate of reduction in primary energy consumption of the Wind–Solar–Storage and Heat Pump (WSSH)–CCHP system were 96.5 %, 99.1 %, and 95.6 %, respectively. Finally, the heat pump-assisted liquid-gap membrane distillation (HP-LGMD) subsystem were optimized in MATLAB. The resulting gained output ratio, flux, thermal efficiency of the system, and energy consumed for water production were 0.0269, 4.22 kg/m2, 17.07 %, and 46.88 %, respectively. The proposed system is highly energy efficient, is capable of economical scheduling, and can use energy cascading, which provides guidance on sustainable development of environment and energy. [ABSTRACT FROM AUTHOR]

Using phase-change slurry (PCS) as the working medium for solar energy systems, for example, in solar-assisted heat pump (SAHP), offers numerous advantages such as photovoltaic (PV) and photothermal (PT) energy generation and heat supply. The PCS experiences a dual-phase change coupled heat transfer during the heat release and refrigerant vaporization, as investigated through simulation. This study confirmed a coupled heat transfer with dual-phase change. It was found that there is more vapor at the upper coupling interface than at the lower coupling interface, and the difference is obviously enhanced when the flow rate decreases from 0.4 m s−1 to 0.1 m s−1 or the temperature increases from 12 °C to 16 °C. The increased rate of flow or decrease in refrigerant temperature is associated with a reduced equilibrium concentration at the lower coupling interface. Nevertheless, an increase in the flow rate at the lower coupling interface causes a decrease in the equilibrium concentration, while raising the temperature increases the concentration. When the flow rate increases from 0.1 m s−1 to 0.4 m s−1, the heat transfer coefficient at the upper/lower coupling interface increases from 159.77 W m−2 K−1/292.58 W m−2 K−1 to 593.54 W m−2 K−1/654.36 W m−2 K−1, and the heat transfer enhancement ratio reaches 45.39% and 9.29%, respectively. When the refrigerant temperature increases from 12 °C to 16 °C, the heat transfer coefficient at the upper/lower coupling interface decreases from 579.16 W m−2 K−1/572.91 W m−2 K−1 to 329.44 W m−2 K−1/365.67 W m−2 K−1, respectively. Increasing tilt angle of the pipe within a moderate range is a potential solution to enhance heat transfer and improve heat transfer uniformity. [Display omitted] [ABSTRACT FROM AUTHOR]

This research aims to manage thermal energy in a solar system to make it more functional due to solar energy variability. A parabolic trough collector (PTC) was integrated with a tank of phase change materials (PCMs) to produce hot air with a temperature close to the PCM melting point over a lengthy period. A comprehensive computational fluid dynamic (CFD) model was developed for the system. After model validation, parametric sensitivity analysis was performed and the proper ranges of the effective parameters were attained. Obtained results reveal that the PTC dimensions must be selected based on inlet temperature to the PCM bed as follows that could melt the entire or a part of PCMs. The PTC's length to its aperture ratio, R l in the range of 0.85–2.25, bed length and diameter greater than 0.9 and 0.35 m, respectively, bed porosity in the range of 0.1–0.5, and inlet air rate in the range of 0.01–0.06 kg/s can satisfy the objectives of the present work. The system can produce up to 1025 m³ of hot air with a temperature of 60 °C and ±2 °C fluctuations during 12.5 h of system operation from the early hours of the day until late at night. [Display omitted] [ABSTRACT FROM AUTHOR]

In 2030, 80% of the world's population will live in cities, when cities are responsible for over 70% of global carbon dioxide emissions. As the built environment accounts for 40% of the global primary energy consumption, changes need to take place towards the energy sustainable transition. The above, combined with Europe's aging building stock, bring the energy renovation and the building integration of active solar systems on existing buildings to the forefront of discussions. The research performed herein, investigates the effects on thermal comfort in public spaces caused by the building integration of active solar energy systems on existing facades in two coastal cities, Naples, Italy and Thessaloniki, Greece, using the Physiological Equivalent Temperature. A typical example of the urban system of each city is chosen, and active solar systems are integrated on the buildings' facades. The thermal conditions on the street level are then simulated by the means of Envi-MET software. The aim is to compare the thermal conditions in the public space, before and after the integration, evaluated through different filters of solar urban planning/building integration of active solar systems, and subsequently focusing to propose the most viable combination of urban practice and building integration strategy. • Integration of a BIPVs for energy retrofitting of existing buildings. • Thermal conditions on the street level simulated with Envi-MET. • Effects on thermal comfort in public spaces caused by building integration of PVs. • Proposal of the most viable combination of building integration strategy. • Use of Physiological Equivalent Temperature (PET) to evaluate thermal conditions. [ABSTRACT FROM AUTHOR]

The employment of solar space heating is a significant measure to achieve carbon neutrality. However, the design of the solar space heating system usually leads to the dilemma of a trade-off between the economic benefit and environmental protection, which cannot be solved by single-objective optimization. In this work, in order to design a solar space heating system of a bungalow equipped with radiant floor heating, multi-objective optimization of the solar collector area and the volume of the water thermal energy storage (TES) tank is performed by coupling TRNSYS simulation, machine learning and genetic algorithm (GA). Simulation for the entire winter operation of the solar space heating system is conducted in TRNSYS, and a database with various combinations of the design variables are generated, based on which an artificial neural network (ANN) is constructed to capture the mapping of the design variables and the system performance indicators. After proper training and validation, the ANN model with satisfactory forecasting precision is utilized as the objective function for optimizing the system. GA is employed for searching the solutions of the multi-objective optimizations. This data-driven approach combining ANN and GA is helpful to achieve the optimal solutions. For the solar space heating system, the CO 2 emission reduction can benefit most from the enlargement of the solar collector area and the TES tank volume, while the payback period reaches its minimum when both the solar collector area and the TES tank volume are small. By comparing single-objective with multi-objective optimizations, it is found that the single-objective optimization cannot reveal the interactions among the CO 2 emission reduction, annualized life cycle cost (ALCC) and payback period (PBP) and that the optimization focusing on a single objective probably leads to apparent defects and inapplicability in reality. Better balance among the CO 2 emission reduction, ALCC and PBP can be achieved from the Pareto optimums of the multi-objective optimization rather than the single-objective optimization. According to the TOPSIS evaluation, the most appropriate design scheme is obtained from the multi-objective optimization and has the potential to reduce the carbon emission by 5480.6 kgCO 2 eq/year while the ALCC and payback period are only 33.40 ¥/(m2·year) and 3.70 years, respectively. [Display omitted] [ABSTRACT FROM AUTHOR]

Solar water heating system is inefficient during winter due to the chances of water freezing and higher viscosity at low temperatures. Several investigations are being done to increase the efficiency of the solar water heater using various secondary fluids for different climatic conditions. This paper emphasises on the study of heat transfer and fluid flow behavior of CO 2 based naturally circulated indirect solar water heating system. Subcritical (liquid and vapour) and supercritical CO 2 are considered as loop fluid, and the results are compared with water based system. Three-dimensional computational fluid dynamics simulations are carried out for two different weather conditions i.e., winter (278 K) and summer (305 K). Results are obtained for 33° collector inclination angle from horizontal at various operating pressures 50–70 bar for subcritical and 80–100 bar for supercritical CO 2. The CO 2 based system yields very high Reynolds number (subcritical liquid: ∼160 times; subcritical vapour: ∼204 times; supercritical vapour: ∼260 times) and very high Nusselt number (subcritical liquid: ∼14 times; subcritical vapour: ∼19.5 times; supercritical vapour: ∼48 times) compared to water based system. Supercritical CO 2 based system exhibits 12% higher energy efficiency compared to water. Whereas, subcritical vapour based system exhibits 140% higher exergy efficiency relative to water based system. Schematic of a CO 2 based naturally circulated solar water heating system. [Display omitted] [ABSTRACT FROM AUTHOR]