Abstract

A thermal performance of the metal foam-PCM composite (MFPC) infused latent heat thermal energy storage (LHTES) systems are widely evaluated based on the first law of thermodynamics. The thermal performance of such system is, therefore, investigated using the first and second law of thermodynamics during the melting process in a present study. The influence of metal foam porosity on thermal transport is analyzed. Results show that the phase change thermal transport can be improved substantially with an incorporation of the metal foam (? = 0.97) with the reduction in the melting time by 40% when compared to the pure PCM. A reduction in porosity of metal foam attenuates the high temperature gradients and hence, the entropy generation rate/irreversibility. Subsequently, the steady state exergetic efficiency is found to be 89.20% and 97.87% for the pure PCM and the MFPC respectively.

Abstract

Butanol is a second-generation biofuel which obtained from the biomass feedstock sources to improve the fuel properties and performance of the recent fuels. However, there are certain grey aspects in the combustion characteristics of butanol blends in various operating speeds and loads. This previous work investigated the use of mineral diesel (D), palm biodiesel (B), butanol (10%)-diesel (90%) (DBu10) and butanol (10%)-palm biodiesel (90%) (BBu10) fuels. The objectives of this study are to investigate the cyclic combustion variations of cylinder pressure profiles and peak cylinder pressure, Pmax and analyse the combustion stabilities using recurrence plot (RP) on tested fuels using a diesel engine. The results showed that higher peak cylinder pressures were observed for butanol blends with full load at 1100 rpm. Higher cylinder pressure cyclic variability occurred at high load and speed for all test fuels, especially DBu10 with higher COVPmax values. Thus, in this case, DBu10 produced the most chaotic combustion irregularities and higher cyclic variations for the time series in those conditions. In conclusion, cylinder pressure variations in the time series were found to be affected by the fuel composition of butanol in the blends and types of fuel in engine operation.

Abstract

Multi-evaporator air conditioning system has found increasing applications in buildings. Energy efficient control for this kind of system is a critical issue. The major challenge is the complicated coupling in operation parameters and strong nonlinearities. This paper proposes a novel energy-efficient decentralized control strategy for multi-evaporator air conditioning systems. In this strategy, the compressor speed is controlled to maintain the suction superheat, and the indoor expansion valve is controlled to maintain room temperature of each indoor unit. The command following test shows that the proposed strategy delivers more stable and smooth control performance compared with a conventional strategy. Moreover, simulation results show that the proposed strategy provides 8.6% energy savings. The proposed strategy is also found to be more robust against model error and actuator faults, compared with a model predictive controller.

Abstract

The European Union is funding scientific research through the Horizon 2020 program. Since the key priorities for the next few years are to reduce carbon emissions and enhance the efficiency of energy systems, a collection of the most recent research projects can be beneficial for researchers who want to easily access and identify recent innovation in the energy sector. This paper proposes an overview of the studies on distributed energy systems and their efficient management and control with the purpose of reducing energy consumption. The characteristics of the projects are summarized and the relevant expected outputs are described. Moreover, the main features that should be tackled to obtain smart, optimized and digitalized energy systems are presented.

Abstract

Adaptive action in terms of window operation has closely correlation with indoor air quality and building energy performance. Guizhou is as a traditional undeveloped area in China, even though the GDP growth rate in recent 5 years is remarkable, very few studies on adaptive behaviours in context of built environment are conducted. In this paper, an investigation on window operation considering the influence of subject type was carried out in HVAC-system-equipped university building during winter in Zunyi, China. Due to out of service of HVAC system, indoor thermal conditions are relative poor and not in the ASHRAE’s winter comfort zones. Outdoor air temperature is identified to be the only physical environmental variable driving window-opening behaviour in this study. Active occupants would like to adjust indoor thermal condition or to improve indoor air quality by means of operating windows. On contrary, passive occupants are reluctant to adjust windows during survey period. But overall, more surveyed windows are opened with the rising in outdoor air temperature. The mathematic models predicting the probabilities of window-opening occurrence are also developed based on logistic regression analysis. The predictive accuracy is 69.65%. This is the first time performing a study on interaction between occupants and window adjustments in Zunyi, China. The developed predictable models also fill in the blank the no quantitative models are available in this area. Therefore, the results concluded from the field study are helpful of providing unprecedented guidelines on improvement of indoor thermal environment and building energy efficiency in Zunyi, China. In addition, by integrating into simulation software the accuracy of dynamic simulation of building energy consumption can also be improved.

Abstract

Aiming at the establishment of energy system structure and energy network in the new-style towns in North Region of China, based on the BP neural network method, a regional energy consumption calculation model is established to calculate and predict the energy consumption in Beijing in the next 50 years. The total energy consumption, total coal consumption and total oil consumption, the total amount of natural gas consumption, and the total amount of hot water supply are predicted. Results indicate that in the next 50 years, the total energy consumption of all forms in Beijing will increase substantially, but the turning point of growth will be different. The growth of fossil energy such as coal and petroleum will be larger in the first several years, while the growth of clean energy will increase sharply during the period of the last several years.

Abstract

Two high-pressure reactors with effective volumes of 1.0 L and 3.3 L were employed to investigate the dynamic behavior of methane hydrate formation and dissociation induced by depressurization with the aim of elucidating the difference in production behavior and developing the scaling criteria. Based on the experimental results, to synthesize aqueous-rich MHBS of the same saturations, the amount of hydrate-formers and the sandy media should strictly adhere to the volume ratio. Increasing the sample size of MHBS resulted in 20.7% increase in gas recover ratio and 53.8% decrease in water recovery ratio under bottom hole pressure of 4.0 MPa. Heat transfer direction were similar from outer boundary inward to the core center. Understanding the effect of scaling on production profile could shed light on better experimental design and possibly field production tests.

Abstract

The free-piston engine linear generator (FPELG) has the high thermal efficiency and simply structure. Thus, it is investigated by many researcher groups. However, many researchers main focused on the FPELG characteristics from the simulation results. Therefore, in the paper, the piston dynamics and the combustion characteristics of the gasoline FPELG from the experimental results were investigated. The experimental results demonstrated that the piston TDC is 32.2mm, the peak velocity is 5.3m/s and the frequency is 32.8Hz. And it is found that the optimal ignition timing of the free-piston engine is between 27.5 mm and 28 mm.

Abstract

China is a vast country with great regional variations in economy level, resource endowments, industrial structure, demographics, and CO2 emissions level. Previous studies on regional CO2 emissions were usually confined to production- or consumption-based perspectives and neglected the emissions under income-based perspective as they also can be enabled by the use of primary inputs. To fill this gap, we investigate the variations of provincial CO2 emissions under these three perspectives in China during 2007–2012 and intend to identify out which type of final demand and primary input contributes most to the variations of provincial CO2 emissions. Results show that variations of domestic outflow and gross fixed capital formation contributed most to the emissions growth for most provinces under consumption-based perspective, while variations of domestic inflow and compensation of employees did so under income-based perspective. This work can help guide the development of just and effective mitigation policies for various provinces in China.

Abstract

In order to improve the efficiency of the existing plunger grouting pump, a new grouting pump based on Wankel engine is proposed. The structure, principle and mathematical model of the Wankel pump were proposed. The efficiency of plunger pump and Wankel pump are analyzed, and the calculation formulas of mechanical, volumetric and hydraulic efficiency of Wankel pump are proposed. The efficiency characteristics of the wankel pump were studied experimentally, and a plunger pump and a Wankel pump of the same power are selected to compare their working efficiency under different working conditions. In general, ηm and ηv increased with increasing n until the load on the shaft was too large. At the same n, The smaller the outlet, the lower the efficiency. When the outlet is a, b and c, the wankel pump test data at n of 190 r/min, 160 r/min and 140 r/min is optimal. When the outlet is big such as a and b, Wankel pump performs higher flow and higher efficiency. However, when the outlet is small such as outlet c, plunger pump performs higher pressure and stable flow and efficiency.