Phase change material board (PCMB) is considered high potential as an efficient passive solution to energy saving in building applications, especially in hot weather. A numerical investigation is conducted on PCMB, with both sides subjected to periodical temperature variations to examine its thermal behaviour. The experimentally validated model is based on the enthalpy method. The inner surface temperature variation is used as a comparison factor, further with two newly introduced parameters, thermal comfort ratio (TCR) and energy saving potential (ESP), to parametrically analyse the influencing factors in terms of both thermal comfort and energy saving aspect. Melting range, latent heat capacity, convective heat transfer coefficients for inner/outer surfaces, thermal conductivity and PCMB thickness are studied parametrically. Furthermore, the optimal heat storage capacity of a PCMB placed on the inner side of a traditional brick-concrete exterior wall is theoretically obtained.
Accurate and robust real-time state estimation is essential to the reliable and safe operation of the hybrid energy storage system. This paper handles a closed-loop method for state-of-charge estimation of lithium-ion battery and ultracapacitor hybrid system. In this work, a fractional-order model is developed to approximate the dynamic behavior of the lithium-ion battery and ultracapacitor. Then, a closed-loop method is proposed for model parameter and state-of-charge estimation. Experiments under dynamic load profiles are used to verify the proposed method. The experimental results indicate that the proposed method can obtain robust estimation results for the hybrid energy storage system, and is appropriate for real-time systems.
This study investigates a fuel spray development process of gasoline–biodiesel blended fuel (GB) in macroscopic and microscopic scales. Long-distance microscopy and shadowgraph were utilized as optical methods to capture the highly transient spray development. Different injection pressures were tested, which ranged from 40 to 120 MPa with a fuel temperature of 323K. Tested four fuels were neat gasoline and biodiesel addition (5%, 20%, 40% by volume) to gasoline in three different ratios. The results regarding the development process for the initial spray near the nozzle show that the spray penetration and the spray tip velocity both decreased with decreasing biodiesel blending ratio. This relationship appears to be due to the associated differences in the mass flow rate and the radial direction velocity vector of the spray. In addition, the different spray tip velocities at the start of spraying result in different atomization regimes between the fuels. The GB fuels with the low biodiesel blending ratio were disadvantaged in spray atomization due to their lower spray penetration and tip velocity. However, as the injection pressure increased, the differences in microscopic spray penetrations between the fuels became smaller, along and there were changes in the atomization characteristics.
Compression ignition (CI) engines have evolved into one of the world’s most capable and reliable forms of motive power for transportation due to high fuel efficiency and high-power output. However, to cope with stringent emission standards, improving the combustion processes, make use of cleaner combustion and implement exhaust gas cleaning systems is necessary. The gasoline biodiesel fuel (GB) blends have the potential to reduce soot formation during the combustion process and will be deeply investigated in this paper. Experiments were performed using 10%, 20%, and 40% blend ratios by volume where both the fuels possess distinct fuel properties to investigate the ignition and soot formation for gasoline biodiesel fuel (GB) blends using an optically accessible constant volume combustion chamber (CVCC). The fuel blends were injected into the CVCC to combust under elevated high pressure-temperature conditions using a singlehole research grade injector. Broadband chemiluminescence technique is utilized to determine ignition characteristics. Natural soot luminous images from the combustible flame were captured by a CMOS camera to determine soot particles during combustion. A wide range of experimental conditions from 800 K to 1200 K and the oxygen concentration 21% was investigated. The experimental observations showed that a higher gasoline content produced a significantly longer ignition delay, thus improving and extending the evaporation process. The combustion properties of gasoline-biodiesel blends are significantly improved with the decrease in gasoline content, and this has the great potential for power generation in the GDI engine.
Due to the introduced spatial-temporal uncertainty and flexibility of the increasing Electric vehicle (EV) charging load, distribution network operation will be greatly impacted by the large-scale EV charging power. This paper proposes a reliability assessment approach considering the stochastic EV charging and movement in an integrated power and traffic system. The improved sequential Monte Carlo method is applied to evaluate the reliability of distribution network. Based on a spatial-temporal charging load model, the influence of different factors on the reliability for distribution network is analyzed in a case, including permeability and the ratio of trip chain, which provides a theoretical basis for the formulation of orderly charging strategies and the planning of charging stations. Furthermore, the reliability analysis considering the future distributed generators (DGs) and EVs development mode is given.
commitments vary considerably among countries. This study explores the cross-country difference in climate change policy stringency and its association with respective cultural differences. Particularly, we hypothesize that more religious countries incline to have lesser stringent climate change policies. Our empirical evidence using ordinary least square estimates provide support for this supposition. Estimates using instrumental variables and further evidence from individual-level analysis with a panel data of up-to 220758 observations over the past three decades confirm our main findings. The results hold up to a bunch of robustness checks. Our findings may be of relevance to policymakers looking to design climate change policy reforms.
Analysis of electricity consumption is important because it concerns the resilience of a country. Data mining techniques are needed that can handle fluctuations in these data, one of which uses SVR. The best parameter search for SVR is the most important for forming the model. In this paper, we will discuss in detail the combination of SARIMA-SVR and Firefly algorithms. The firefly algorithm is one of the metaheuristic techniques that provides accuracy which proven by the value of MAPE and RMSE.
This study presents an experimental rig of singlestage heat transformer (SSHT), to compare its performances in case of producing high-temperature water (HTW) or low-pressure steam (LPS). SSHT was built with four vertical falling film heat exchangers using a LiBr-water binary working fluid and is driven by lowgrade hot water. Bilateral falling film vertical absorber is adopted for production of HTW or LPS. Following the principle of single variable, the effects of temperature and flowrate of heating water on the useful output heat, coefficient of performance (COP) and gross temperature lift (GTL) of the vertical SSHT were tested, respectively. The results show that bilateral falling film made it easier for the absorber to generate HTW and LPS directly. In case of producing water or steam, temperature at inlet and flowrate of heating water have similar effect on the useful output heat and COP. To some extent, we can improve the performance of SSHT by increasing the temperature.
This study researched an efficient-utilization planning method for community buildings, which considers supply- and demand-side factors comprehensively. The method consists of three key aspects. The first is the goal orientation of renewable energy utilization planning boundary condition optimization. The second is community building function optimization based on load leveling, and the third is building morphology optimization based on the energy control. The method is an important reference for community energy planning in China.
This paper presents a social, economic and environmental study on a novel solar-powered zero-bill rural house space heating system compared to the conventional coal-powered and gas-powered systems. The system can significantly reduce the fossil fuel consumption, and reach to zero-bill operation, thus decreasing the operation charge and air pollution. By using the established model, the research analyses the energy performance of the novel zero-bill solar-powered system under a typical northern China weather condition (Taiyuan city). Then, it compares the economic and environmental performances between three space heating systems. It is found that, for a 100m2 typical rural house, the total heat demand is 8081kWh during the heating season. According to the local feed-in tariff, 0.75RMB/kWh , the PV model can earn 1297.2RMB per year, which is higher than the annual system electricity bill, 732.48RMB, and thus the novel system can reach to zero-bill and zero energy consumption. When it comes to economic analysis, due to the zero-bill and zero energy consumption characteristics, the system has a cost payback period of 14.8 years and a life-cycle net cost saving of 17573RMB compared with the coalpowered system. In contrast with the gas-powered system, the system has a cost payback period of around 5.9 years and a life-cycle net cost saving of 52723RMB. Furthermore, under the view of environment, one set system can annually save 1320kg standard coal or 1022.39m3 natural gas. Besides, it also annually reduces the 897.6kg harmful dust, 3220.8kg CO2, 99kg SO2 and 49.5kg NOx compared to the most environmentally contaminated coal-powered system. The widely use of the novel solar-powered system can enormously help to improve the living standard of the residents staying in a wide range of rural areas in northern China, and thus the system can harvest greater social, environmental and economic benefits subsequently.