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Graphical abstract Highlights • A 3-layer phase change material configuration was proposed. • A method for temperature selection of phase change material was proposed. • Novel hybrid phase change material wallboards were fabricated and characterized. Abstract Phase change materials are smart, feasible latent heat storage materials and have been incorporated into building materials to reduce energy demand and improve the thermal comfort of buildings. This study proposes a method for improving energy efficiency and thermal comfort in buildings (during both summers and winters) by developing a novel hybrid phase change material wallboard and a method to select the temperature of phase change material for different seasons (29 °C for summer, 18 °C for midseason, and 12 °C for winter). This type of hybrid phase change materials wallboard consists of three types of phase change materials with different phase-change temperatures that can be utilized efficiently in different seasons. The thermal performances of the hybrid phase change material wallboards (two combination modes: Mode1 and Mode2) were evaluated by a guarded hot plate method. The effective thermal conductivity (λ) and apparent specific heat (C p) of these wallboards were investigated. The interior temperature variations of the two types of phase change materials wallboards were compared during heating and cooling, and it could be concluded that the Mode2 hybrid phase change materials wallboard (where phase change material was incorporated into different gypsum wallboard layers) was more suitable for real applications. The goal of this study is to investigate an appropriate method to fabricate a new hybrid phase change materials wallboard for building energy savings over different seasons. [ABSTRACT FROM AUTHOR]

Highlights • Integration of spray cooling with waste heat reusing and peak load shifting. • HCS exhibits excellent energy saving, exergy increase and operation cost saving. • Sensitivity analysis shows the importance of spray cooling inlet temperature. • Economic analysis shows a cost payback period as low as 286 days. Abstract A hybrid cooling system aimed at enhancing energy, exergy and economic efficiency of data center is proposed. The proposed system combines a high cooling efficiency spray cooling system, a waste heat reusing absorption chiller and a peak load shifting chilled water storage. This combination is implemented by replacing the condenser of spray cooling system with the generator of absorption chiller, and storing cooling capacity of absorption chiller during off-peak time to supplement the cooling load during on-peak time. A thermodynamic model is developed based on energy and exergy balance. Parametric sensitivity analysis is performed to investigate the effects of spray cooling inlet temperature, chilled water temperature, cooling water temperature and ambient temperature on the energy saving efficiency, exergy efficiency and operation cost. Comparison study and economic analysis are conducted based on Dawning 5000A supercomputer in Shanghai, China. Sensitivity analysis results show that the effect of spray cooling inlet temperature is the largest, while the effects of chilled water temperature and cooling water temperature are the smallest. At appropriate condition, the absorption chiller and chilled water storage could totally eliminated the cooling load of air conditioner during on-peak time. The energy saving efficiency, exergy efficiency and operation cost saving could be up to 51%, 17%, and 71% with the cost payback period as low as 286 days. [ABSTRACT FROM AUTHOR]

This paper aims to evaluate the year-round applicability of a kind of composite-PCMs wall (PCM-wall). The test was carried out in a full-scale room with a net dimension of 3.25 m ( L ) ∗ 3.86 m ( W ) ∗ 2.91 m ( H ) in three seasons, and comparisons were made with a regular energy-saving wall. Specific thermal capacity of the PCM-bricks was carried out according to DSC tests. Then thermal performance mainly including of energy-saving effect during summer and winter, reduction of interior wall surface temperature fluctuation during midseason was investigated. Results showed a reduction of about 0.2 °C for the maximum interior wall surface temperature, a time delay of about 1–2 h and a reduction of 24.32% of the cooling load for the PCM-wall under summer conditions. For the midseason cases, the PCM-wall was under the phase transition temperature range and could completely resist the ambient thermal disturbance. Besides, fluctuation of the interior wall surface temperature could be effectively reduced. For the winter cases, the PCM-wall could reduce 10–30% of the heating load. Additionally, as for the cases where air-conditioner was off during daytime (8:30–18:30) or nighttime (18:00–9:00 (next day)), a reduction of 9–72% of the heat lost from the interior wall surface could be achieved. To summarize, the PCM-wall performed more excellent thermal behavior all the year round. [ABSTRACT FROM AUTHOR]

Highlights: [•] A new type of PCM room is proposed, two kinds of PCM were used in the room. [•] The new room can decrease the indoor air temperature fluctuation by 4.3°C in summer. [•] Indoor air temperature fluctuation was decreased by 14.2°C in winter for the new room. [•] Important factors that affect the thermal performance of the new room were studied. [ABSTRACT FROM AUTHOR]

• Carbon corrosion mainly occurs in the outlet of fuel cell during reversal. • Different regions have different performance degradation. • Part of the performance is recoverable after reversal. Hydrogen starvation at the anode of a proton exchange membrane fuel cell (PEMFC) causes cell voltage reversal followed by water electrolysis and carbon corrosion due to an increasing anode voltage. This study designed a set of online testing methods in different regions to take a closer look at the real-time changes of the internal current density and local temperature during the voltage reversal process. Mass spectrometer is used to test the anode tail gas to quantitatively characterize the progress of the reversal. Local Electrochemical Impedance Spectroscopy (Local EIS) and local Pt shedding before and after the reversal are innovatively performed to analyze the performance degradation of the fuel cell in different regions. In addition, the performance of fuel cell before and after the recovery process after the reversal is analyzed. Results show that the carbon corrosion in the outlet region of the reversal anode is the most severe, and the temperature at the inlet region due to the consumption of residual hydrogen is the highest. Compared with the inlet region, the Pt loss and High-Frequency Resistance (HFR) increase in the outlet is more serious. The process of performance recovery after reversal can make the current density distribution in fuel cell more uniform. Besides, the recovery process conducts a more positive impact on fuel cell outlet region than on inlet region. Data of mass spectrometer prove that water electrolysis and carbon corrosion disappear in the second reversal process, and then appear again in the third reversal process due to the performance recovery process. [ABSTRACT FROM AUTHOR]

• Propose a multi-objective optimization and robustness analysis integrated framework. • Merge multi-objective optimization with two-stage stochastic programming. • Generate probabilistic stochastic scenarios capturing multiple uncertainties. • Identify the final optimum solutions by two decision-making methods. • Combine optimization with Monte Carlo simulation for robustness analysis. The optimal design of building integrated energy system is sensitive to the variation of uncertain parameters. For addressing the tradeoff of uncertainty and optimality-robustness, this study proposes a combined multi-objective optimization and robustness analysis framework for optimal design of building integrated energy system. The proposed framework includes two parts. In the optimization part, on the basis of scenario generation for capturing the uncertainties of renewable energy sources and energy demands, two-stage multi-objective stochastic mixed-integer nonlinear programming is conducted to optimize the system's economic and environmental objectives. Two decision-making methods are introduced to identify the final optimum solution from the obtained Pareto frontier. In the robustness-analysis part, a combined Monte Carlo simulation and optimization method is implemented to verify the robustness of the optimal solutions. The two parts of the framework are integrated to investigate the case of a hotel in Beijing, China. The results indicate that compared with the stochastic model, the deterministic model underestimates the annual total cost. Achieving economic and environmental optimum is conflicting and needs a trade-off through decision making. Moreover, in the robustness analysis, an acceptable robustness value is identified, considering both the selected objectives and the operation constraints' probability of failure. The Shannon-entropy-based final optimum solution exhibits the best comprehensive performance, with an annual total cost of $695 × 103/year, an annual carbon emissions of 2100 tons/year, and an 8.81% probability of failure. [ABSTRACT FROM AUTHOR]

• A novel open type I-CAES with hydraulic machine and spray cooling is proposed. • A transient thermodynamic model including air-water heat transfer is presented. • OI-CAES enables continuous energy storage and near isothermal compression. • Indicated efficiency of 98% and roundtrip efficiency of 76% are achieved. • Compression and expansion time ratio of 99% and 96% are obtained. Isothermal compressed air energy storage (I-CAES) is a high efficient emission-free technology to facilitate the integration of fluctuating renewable energy into the power grid. However, in conventional closed type I-CAES (CI-CAES), the volumetric energy storage density is very low since two working mediums exist (water and air) and the water storage tank doubles the system volume. Thus, an open type I-CAES (OI-CAES) is proposed to solve this problem. Based on reversible hydraulic pump/turbine, the proposed system could achieve continuous energy storage/release and increase the compression/expansion time ratio, thus increasing the volumetric energy storage density. Combined with spray cooling, OI-CAES system could achieve near isothermal compression/expansion and improve the energy storage efficiency. A transient mathematical model is established based on thermodynamic laws and heat transfer theory. Thermodynamic analyses including a single cycle analysis and a continuous cycle analysis are carried out. A comprehensive performance assessment of the proposed systems is conducted and the effect of spray flow rate is analyzed. The results show that the compression time ratio during energy storage and the expansion time ratio during energy release are increased to 99.2% and 95.6% respectively. The energy storage density is doubled compared to CI-CAES at the same working pressure. The nearly isothermal compression/expansion is achieved with air temperature change as low as 5 °C. The indicated efficiency and roundtrip efficiency are as high as 0.98 and 0.76 respectively. [ABSTRACT FROM AUTHOR]

• An advanced concept of coupling SAGT and SAPG is proposed. • Utilization of solar energy realizes both energy saving and pollutants removal. • Flue gas treatments with an improved order may prevent catalysts from deactivation. • The stability and efficiency of the concept are relatively good. In this paper, an advanced concept of coupling solar-aided flue gas treatment (SAGT) and solar-aided power generation (SAPG) is proposed to realize the low energy consumption flue gas treatment for fossil fuel power generation systems. An improved flue gas treatment sequence outside boilers is proposed in SAGT, where denitration is configured downstream of flue gas desulfurization (FGD). By using a parabolic trough collector (PTC) solar field, flue gas can be heated up to 550 °C in the collectors. The treatment sequence therefore can be achieved with the assistance of solar field. Finally, the waste heat of flue gas is utilized to preheat the feed water of boilers to enhance the power generation of power plants. A 600 MW coal-fired power plant system is analyzed as a case study. The calculation results show that SAGT and SAPG have relatively good performances both on stability and solar-to-electricity efficiency. This study might provide a new solution to deal with the difficulties of treating flue gas inside boilers such as deactivation and blockage of catalysts. Furthermore, efficient utilization of solar energy realizes both environment protection and energy conservation. [ABSTRACT FROM AUTHOR]

Investigating the relationship between the performance of an integrated energy system (IES) and each influencing factor as well as directly calculating IES efficiency based on relevant parameters are of substantial importance to energy saving. To make the research results applicable to various IES, a typical integrated energy system (TIES) which includes typical energy conversion technologies is proposed. After building energy demands and energy conversion processes in TIES are abstracted and simplified by a typical energy flow map, a dimensionless equation for calculating TIES energy and exergy efficiency is developed. Based on the partial derivatives analysis of TIES’s energy and exergy efficiency dimensionless equation, the effects of technological level, demand structure, local renewable energy utilization and IES configuration on energy and exergy efficiency are clarified. Combined with a case study, the usability of the parameter analysis method for IES has been illustrated. The departure phenomenon of energetic and exergetic analysis results in IES are also introduced. Furtherly, we indicate that without proper definition of benchmark environment, it is easy to give perplexing results with an exergetic analysis about IES. [ABSTRACT FROM AUTHOR]

• An inflatable structure is designed for Savonius wind turbine. • A double-layer fabrication process is proposed for the inflatable wind turbine. • Geometry parameters of the inflatable wind turbine are optimized based on CFD. • Static and dynamic performances are investigated through wind tunnel tests. • The inflatable wind turbine shows high portability and rapid deployment capability. Faced with the increasingly severe issue of the greenhouse effect, wind power emerges as a sustainable solution. However, the large size, heavy weight, and high risk associated with traditional wind turbines restrict their widespread deployment in urban, rural, and outdoor settings , wasting a vast amount of untapped wind energy resources. To address these challenges, this paper proposes an inflatable structure for the Savonius wind turbine and explores a double-layer fabrication process to manufacture the inflatable Savonius wind turbine (ISWT). 2D simulations are carried out on ANSYS-Fluent. Within predetermined parameter ranges, this paper successfully identifies the optimal geometric parameters for the ISWT model, with a blade thickness of 7 cm and a blade arc angle of 120°. This model exhibits the maximum power coefficient (C p) of 0.1912 at the tip speed ratio (λ) of 0.7. The manufactured ISWTs are fabricated based on the optimal geometric parameters. Due to deformation after inflation, the actual blade arc angle of the first ISWT sample is only 89.7°. Therefore, by adjusting the fabric template, an approximate blade arc angle of 120° is achieved for the second ISWT sample. Both ISWT samples are subjected to open-section wind tunnel tests. The results revealed that while the C p curves of Sample 1 and Sample 2 display trends similar to those in numerical results, the overall performance is lower. The reasons for the deviation include the simplification of vertical flow in 2D simulation and the lack of endplates. Specifically, Sample 2 also achieves the highest C p value of 0.1486 at λ = 0.7. Due to an inflation time within 60 s to the required pressure of 1.4 bar and a compressed volume lower than 0.021 m3, the ISWTs demonstrate rapid deployment capability during installation, portability during transportation, and storability during severe weather. [ABSTRACT FROM AUTHOR]

• Passive radiation control technologies are discussed by window, roof and wall. • In-depth analysis on spectral characteristics and cooling performance. • The feasibility of realizing building energy saving is proven by thermal analysis. • The favorable characteristics towards solar and thermal radiation are suggested. Buildings inevitably absorb solar (thermal) radiation through the envelope, i.e., window, roof and wall, whose characteristics, in terms of material, thickness, area etc., affects the performance of space cooling, thereby inducing energy wastage by air-conditioning system to maintain satisfied indoor thermal comfort. Metropolises with congested-built architectures and humid climates consume tremendous energy in space cooling, contributing to massive carbon emissions. Space cooling has been the most soaring electricity end-user and its increasing carbon emission amplifies global warming, which in turn increases occupants' dependence on artificial cooling, especially in hot climates. The urgency of the climate crisis has put passive cooling technologies, which can efficiently manage heat transfer of buildings, to the forefront of research. Thermochromic smart windows, daytime radiative coolers and reflective paints are three prominent technologies that have drawn industries' attention. These technologies respond to incident sunlight and thermal radiation differently, compared to conventional building envelope, and can passively mitigate solar radiation absorbed at the building envelope, reducing electricity consumption for air-conditioning. This review article comprehensively discusses the characteristics of the three passive energy-efficient techniques that can be integrated with building façade (window, roof and wall), and their feasibility in building cooling applications through thermal analyses. Through this review, the ideal spectral properties of these technologies will be distinguished. Although the properties of these technologies have been abundantly explored, the research on their long-term cooling performance under the influence of weatherability and aging remains scarce. Further, their cost-effectiveness is essential for realizing commercialization and reducing hesitancy in adopting these novel passive cooling technologies for taking a significant leap towards carbon neutrality. [ABSTRACT FROM AUTHOR]

• A fuel consumption model for Hybrid Electric Vehicles (HEVs) is developed. • Real driving tests of Argonne National Laboratory are used to verified the model. • HEVs show considerable fuel saving in various traffic conditions. • HEVs can not save much fuel when the traffic is in free flow state. Despite extensive work on the fuel consumption of vehicles, the evaluation of hybrid electric vehicles (HEVs) requires a model that can predict fuel consumption second by second. In this paper, a fuel consumption model for hybrid vehicles is developed based on the operation of internal combustion engine (ICE), electric machine (EM) and battery. The fuel consumption model for engine is based on steady-state fuel mapping with a transient correction. EM and battery module (EBM) is introduced to estimate the fuel consumption for different modes of hybrid vehicle. The Argonne National Laboratory (ANL) measurements of different driving cycles including the steady-state cycle, the Urban Dynamometer Driving Schedule (UDDS) cycle, the Highway cycle and the United States 06 (US06) cycle are used to verified the model. With cellular automaton simulation, we study the fuel consumption in traffic flow and show that the fuel consumption can be significantly reduced by hybrid mode. The mean fuel saving is approximately 30% in the traffic flow on a horizontal road. The fuel consumption of traffic flow under uphill, downhill, tailwind and headwind conditions also showes considerable fuel saving. The model can be used to evaluate the fuel economy of HEVs, and provide eco-driving route-choice suggestions for drivers. [ABSTRACT FROM AUTHOR]