Abstract

Overhead transmission line is an important part of power system, it is easy to be affected by natural disasters. In order to enhance the ability of power system to resist those disasters, the resilience assessment indices should be established to provide decision support for power grid dispatchers and operators in advance, which has become one of the economical and efficient technical routes to improve the power system resistance ability. In this paper, windstorm is taken as an example, the wind speed related fragility model of overhead transmission line and impact-increment state enumeration method based resilience indices are proposed. The resilience indices are proposed form the perspective of system and component respectively. The system resilience indices can reflect the resilience from a holistic perspective and the component resilience indices are expected to determine the weak points of the whole system. The system resilience and weak points of the IEEE RTS-79 system are analyzed under one certain windstorm and the numerical results verify the effectiveness of the proposed resilience assessment indices.

Abstract

Methane hydrate formation has been a crucial factor affecting the blockage of in subsea oil and gas transportation pipelines. To study the rheological properties of hydrate slurries, methane hydrate were formed in situ from water-oil emulsion with different water cut (20 vol%-70 vol%). Meanwhile, viscosity measurement and yield stress measurement were conducted with a high-pressure rheometer. Emulsion exhibit a shear-thinning behavior and increase in viscosity under hydrate formation. Hydrate slurry viscosity and yield stress had a significant increase with increasing water volume fraction. And hydrate formed in oil-in-water emulsions were more likely to aggregate and cause blockage than in water-in-oil emulsions.

Abstract

In this paper, BPSO algorithm is used for DSM implementation in the SG environment. Load shifting technique is applied in the residential and industrial area and shifted the load from peak hours to off-peak hours. Load shifting technique is mathematically formulated and implemented as a minimisation form. In this paper, it has been clearly shown that BPSO based load shifting method can be able to handle a large number of devices of various types compared to the traditional DSM method. The focus of this work is to reduce the peak load demand, electricity cost, PAR as well as to achieve substantial cost savings. BPSO based load shifting method shows the better result in terms of peak load reduction when compared to GA based DSM.

Abstract

This paper presents a correlative method for the cost-efficient measurement of the energy content of propanated biomethane, which is relevant for injection into gas distribution grids. The gross calorific value and Wobbe index were predicted by the regression models from the measured set of physical properties of the gas sample, including speed of sound, sound attenuation parameter, and carbon dioxide concentration. The required properties can be measured using standard sensors and instruments; therefore, they enable in situ application of the method. The results of the experimental validation corroborated with the results of chromatographic analysis.

Abstract

In this work, two choline-based low-cost ILs (i.e., [Ch][Gly] and [Ch][Cl]) were synthesised in laboratory and applied for the delignification treatment of “Rice Husk (RH)”, an abundantly available lignocellulosic biomass in Australia. The synthesised choline based ILs were compared with commercially available imidazolium based IL ([Emim][OAc]). Among the all ILs studied, [Ch][Gly] outperformed over others in terms of degree of delignification. In addition, it has been established for the first time that RCRM produced from the choline-based ILs has higher porosity, crystallinity and thermal stability compared to imidazolium based ILs. The findings from this work recommends that pre-treatment with choline-based ILs is highly favorable for the production of platform chemicals from lignocellulosic biomass.

Abstract

Lithium-ion battery state-of-health estimation plays an important role in battery management system in electric vehicles. Here, we report a novel method for battery state-of-health estimation through grey relational analysis with entropy weight method. Firstly, an interpolation method is proposed to obtain the differential voltage curves. Then health performance indicators are extracted from the partial differential voltage curve considering the inflection points. Secondly, the evaluation indexes are proposed by using entropy weight method to evaluate the significance of health performance indicators in the partial differential voltage curve. The evaluation indexes of the fresh cycle battery are defined as reference sequence and others as comparative sequences. Then the proposed method to calculate the grey relational degrees between the reference and comparative sequences and the results are applied to analyze battery health condition. At last, the corresponding experiment indicates that the proposed method can accurate estimation battery health condition.

Abstract

LCL filters are widely used in microgrid converters because of their high level of harmonic attenuation introduced by series inductors. The main challenge of the LCL filters is to damp the associated resonance peak in order to improve the quality of grid injection current. To address this challenge, this paper presents an improved weighted average current control (WACC) method. It applies grid-voltage-feedforward in an inner loop to solve the resonance peak of the filters and reduce the impacts of the grid voltage harmonics on the grid injection current. A PI controller is designed in an outer loop to keep the DC voltage stable. The improved strategy not only simplifies the design process, but also makes the LCL filter system more robust. Simulation and experimental results verify the feasibility of the proposed strategies applied to a dual-buck bidirectional converter with a LCL filter.

Abstract

The majority of single-family houses in Sweden are affected by deteriorations in building envelopes as well as heating, ventilation and air conditioning systems, since they are about 30 years old. Theses house are therefore in need of extensive renovation, which provides an excellent opportunity to incorporate energy efficiency measures to reduce both the energy consumption and also operational. Although former studies analyzed the cost effectiveness of various renovation packages, they mainly excluded the evaluation of energy price implications on cost effectiveness of different renovation package in Sweden. Accordingly, this study considers three energy prices and quantifies the payback period (PBP) and internal rate of return (IRR) of the packages, when renovating a single-family house in Sweden. The renovation packages included three distinct energy supply systems, commonly installed when implementing energy renovations: ground source heat pump (GSHP), photovoltaic solar panels (PV), and an integrated GSHP and PV system. The analyses of results show that a the GSHP system provides higher IRR and the lowest PBP compared to the other two renovation packages, due to its high performance in reducing energy consumption and its relatively low investment cost. Furthermore, results show that raising the energy price can increase the IRR and reduce the PBP of the renovation packages and respectively. Moreover, increasing the interest rate adds on PBP of renovation packages, since it depreciates the cost for saved energy.

Abstract

In order to effectively develop a future European energy system based on variable renewable energy systems (VRES), the probabilistically-occurring low generation periods from wind and PV generators must be better understood. However, little explicit information on these VRES lulls is currently available in relation to: how long these VRES lulls could last, how often they could occur, and how these qualities vary between differing regional contexts. This work, therefore, addresses these issues for wind and PV generation in the context of an exemplary future European energy system. To accomplish this, future-oriented wind and PV generation is recreated at high spatial and temporal resolution from the basis of a literature-derived European energy system scenario in 2050. The occurrence of VRES lulls are then observed in the resulting generation profiles over a 37 year time frame for the whole of Europe and several nations. The likelihood of observing a lull spanning X hours at least once in a randomly selected year is then found. Results of this work can be used by energy system planners and researchers to estimate minimal backup and storage needs in future VRES-prominent European energy systems.

Abstract

In this study the performance characteristic of a CO2 ejector-expansion system applied for battery pack cooling is investigated. An experimental bench is set up and the performance of the system is experimentally studied under different working conditions. The cooling capacity and COP of the system decrease with the increasing of gas cooler outlet temperature. There is an optimal opening degree of EEV for both the capacity and COP to get a maximum value. The entrainment ratio of the ejector is improved by introducing an IHX. Compared with the basic cycle, ejector-expansion system can improve both the cooling capacity and COP significantly, around 21.7% increment in cooling capacity and 28.0% increment in COP, respectively.