Abstract

The pyrolysis behavior of cattle manure was analyzed by three methods in this work: thermogravimetric analyzer (TG), Pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) and pyrolysis photoionization time-of-light mass spectrometry (Py−PI−TOFMS). The pyrolysis process of cattle manure could be divided into four stages, dehydration stage, lignocellulose decomposition stage, lignin and protein decomposition stage, char and mineral matter decomposition stage. The products was mainly classified into six groups: ketones, aldehydes, phenolic compounds, acids, hydrocarbons and N-containing compounds. Based on the time-evolved profiles and temperature-evolved profiles, the characteristics of these major products were analyzed and discussed. Furthermore, their possible formation pathways were also proposed and discussed.

Abstract

This paper describes the thermal performance of an adsorption refrigerator system utilizing activated carbon-ammonia pair. The experiment was done by using thermal energy supplied by electric tape heater to the adsorber at selected temperature of 110°C with varied desorption time from 1 to 4 hours. Records of energy consumption, temperatures for adsorber, condenser, evaporator cold chamber and adsorber pressure were taken. The prototype tested attained evaporator cold chamber temperatures varying from 4.8°C to -0.6°C for desorption times of 1 to 4 hours. These temperatures are relevant to the vaccine storage requirement of 2C to 8C. Therefore, this adsorption refrigeration technology, which can be easily manufactured in least industrialised countries is a promising solution for off grid application.

Abstract

This study proposes building driven-energy payback time (BD-EPBT) as a new life cycle assessment indicator. The BD-EPBT is the time required to outrun the total life cycle energy used in a power system-integrated building with annual surplus energy. As a result of a case study, it was shown that the BD-EPBT is highly associated with the embodied energy of construction materials. Also, by increasing the power system capacity (i.e., PV system) from 3 kW to 5 kW, BD-EPBT can be reduced by one fifth. The BD-EPBT is a novel concept capable of providing comprehensive analytics solutions to energy decision problems for building owners.

Abstract

With globalisation and financialisaton, exchange rates could be sensitive to oil price shocks. Due to differences of exchange rate policy, oil-dependence status, and other factors, the responses of exchange rates to oil price shocks could be either similar or heterogeneous. Therefore, in this paper, we integrate a hybrid research framework to investigate the co-movement of responses to oil price shocks of four major exchange rate of currencies included in the Special Drawing Rights basket from January 2000 to September 2018 from a time varying aspect and considering the asymmetric effect of the oil price shocks. The main results are as follows: compared with the general oil price shocks, unexpected oil price shocks could have greater influence on currency markets over time; pairwise exchange rates tend to move in either a negatively or a positively similar way, rather than in an unrelated manner; in 50% of the sampled market time, the co-movement situation of exchange rates’ response could be captured by specific small numbers of co-movement modes, with the Euro/US dollar (USD) and Great British Pound/USD tending to co-move in more stable manner and having the potential to serve as an early warning of risk, while other pairwise exchange rates are characterised by time varying features.

Abstract

In order to realize the economic operation of the home energy management, the electricity cost of user needs to be reduced and user-side satisfaction should be improved. A home energy scheduling optimization model including the home electricity load model and the photovoltaic power generation model was constructed, the objective function was established, which takes minimizing the electricity cost and the user satisfaction into consideration. With the constraints of power balance, load working time and temperature control load. Finally, combining genetic algorithm with local optimization method, a hybrid Pareto genetic algorithm for multi-objective optimization is proposed to obtain the approximate solution of multi-objective function. Based on the simulation results of MATLAB platform, the optimal solution which both minimizes electricity cost and maximizes user’s satisfaction has been obtained.

Abstract

The Thermal Electrochemical Co-drive System (TECS) has the advantages of high desorption rate and low energy consumption. However, the fluid flow, heat and mass transfer performance is still unknown in TECS. Thus, a comprehensive experiment and simulation work on TECS is performed to demonstrate the fluid flow, heat and mass transfer performance in a pilot scale TECS. The reaction kinetics of the electrolyzed MEA/SG solution is discussed. A pilot-scale TECS is set up and gas-liquid two-phase flow model is developed for the TECS. According to the numerical computation and experiment, the gas-liquid two-phase flow field was analyzed under the thermal electrochemical co-drive conditions. The mechanism of heat and mass transfer was clearly understood. The synergy of thermal desorption and electrochemical desorption was quantified numerically. The results showed that the temperature of TECS was reduced below 60 ℃ and the energy consumption amount was determined at 1.3GJ/t to 2.1GJ/t, which is much lower than the conventional process. LNG cold energy reduced the desorption energy consumption.

Abstract

Potassium is a natural catalyst in biomass thermochemical conversion and plays an essential role in plant’s growth. To figure out the catalytic effects of potassium on the thermochemical behaviors of biomass, the pyrolysis characteristics of rubber wood are comprehensively studied using a thermogravimetric analyzer where the biomass is impregnated by different concentration of potassium carbonate (K2CO3=0.004 M, 0.008 M, and 0.012 M). The thermal degradation with independent parallel reaction (IPR) model is adopted. To maximize the fit quality between the established kinetic models and experimental data, particle swarm optimization (PSO), a kind of evolutionary computation, is employed. The results suggest that the thermal degradation curves of the raw and impregnated rubber wood can be predicted with a fit quality of at least 97.5%. It is proved in this work that the IPR model and the calculation of the PSO can be used to predict the pyrolysis kinetics of impregnated biomass to a good level of fitness.

Abstract

Aquifer thermal energy storage (ATES) has been proved to be an efficient way to achieve seasonal thermal energy storage and can improve the efficiency of heat pump systems greatly. But for ATES systems using brine aquifer as thermal energy storage medium, there is large reduction in permeability of the aquifer due to the difference of salinity and temperature between the injected water and aquifer, then heat transfer process could be influenced. In present work, effects of injection salinity and injection temperature on the underground temperature and performance of the ATES system are studied. Results indicate that reducing injection salinity slows down the heat transport in the brine aquifer, and improve the thermal energy storage of the brine aquifer thermal energy storage system due to the decrease of hydraulic conductivity of brine aquifer. Decreasing injected cold water temperature or increasing injected hot water temperature is helpful to improve the thermal energy storage, which is the comprehensive influence of the reduction of hydraulic conductivity and the increase of temperature difference.

Abstract

The way towards a more sustainable future, involves increasing amounts of variable renewable energy (VRE), yet the inherent variability in VRE generation poses challenges on power system management. In this paper, a method is presented to quickly assess the fluctuating discrepancies between VRE production (wind and solar) and electricity consumption for system planning purposes. The method utilizes a discrete Fourier transform (DFT) analysis to disentangle the energy storage and power flexibility requirements on different frequencies and is applied here to different geographical areas and to current and future scenarios in both real and simulated hourly data. Novelties include a subdivision of the residual load in more temporal scales than usually adopted, a pie chart visualization to compare the strength of different oscillations and a ready‐to‐use Python module.

Abstract

An experimental study of a two-phase ejector with R134a as the working fluid is presented in this paper. The main objective is to determine the effects of the divergent section of the nozzle on the ejector performance under various working conditions. For the same conditions of operation, the ejector with a convergent nozzle presents a higher critical primary mass flow rate and a lower critical pressure in comparison to the version with a convergent-divergent nozzle. Globally the ejector with the convergent-divergent nozzle provides a higher entrainment ratio. The nozzle geometry has no impact on the optimal position of the nozzle. The same position giving the best entrainment ratio was found for the two tested nozzles. Unlike the convergent-divergent nozzle, the convergent nozzle has an entrainment ratio almost insensitive to a wide range of primary inlet subcooling. Primary and secondary mass flow rates increase with the subcooling level in a proportional way, resulting in a quasi-constant entrainment ratio.