Abstract

Power industry is the most important basic energy industry of national economy development, and it is also a big carbon emitter. With the continuous and rapid growth of renewable energy (RE) capacity, the contradiction between the scale development of renewable energy and the lack of market capacity is becoming more and more obvious. To achieve lowcarbon development and build a low-carbon society, we must develop low-carbon electricity and construct a feasible low carbon electricity price mechanism. In this paper, based on the efficient RE consumption, we introduce carbon cost to construct dynamic and variable low carbon real time electricity price mechanism, including the spot market pricing, grid fees and RE surcharge. Then the paper gives the electricity price strategy and its realization algorithm and verifies the beneficial effect of the proposed pricing mechanism by the example analysis. The proposed low carbon price mechanism is of great practical significance for the development and consumption of large-scale renewable energy.

Abstract

Experiments are conducted under typical humid ambient conditions of Singapore on an advanced airconditioning system wherein desiccant coated fin-tube heat exchangers (DCFTHX) are retro-fitted within the ducting of a conventional HVAC system with a watercooled condenser. The desiccant is regenerated using room-return air (specific humidity of 0.0109 kg/kg d.a.) and the low-grade heat (warm water at 35.5oC) from the condenser unit. During dehumidification, water from the cooling tower helps in maintaining low air temperature, thereby improving the adsorption performance of the DCFTHX. It is found that DCFTHX managed 39% of the cooling load thereby reducing the compressor load by the same percentage. The experiments prove the efficacy of such internally cooled/heated desiccant systems for practical applications.

Abstract

The article illustrates the fluid-dynamic and mechanical analysis of some forms of small-power vertical axis wind turbines, resistant type, whose blades are made of wood and easily workable in a joinery. In particular, a classical-shaped Savonius, a modified two blades Savonius, a three-bladed Savonius and, again, a rotor with three straight blades having a crescentmoon section, were studied. A result of the study, worthy of note, concerns the possibility of greatly reducing the mechanical stresses on the support relatively to the rotor having the last shape. This is very important for its installation near inhabited buildings or even integrated into roofs. Furthermore, the crescent-moon section prototype is able to provide 1 kW power at the nominal wind condition of 12.5 m/s and an annual energy production of 1200-1500 kWh/year, considering a typical urbane site having an average wind speed between 4.5 and 5 m/s.

Abstract

The popularity of electric heating equipment in rural areas has led to an increase of the peak load of electricity. In order to ensure the reliability of the system, the indoor building heat balance and the flexible comfort requirements of users can be comprehensively considered. So we propose a reliability assessment method of rural clean energy supply system based on accurate modeling of user demand. Firstly, the rural clean energy supply system framework is constructed, including the system-side equipment model and userside building heat balance model. Secondly, we model the user’s flexible comfort requirements, which derive indicators of the reliability of energy supply considering flexible comfort requirements. Thirdly, the method of fault impact analysis of rural clean energy supply system is proposed, and the load reduction strategy at failure time and the process of reliability assessment are formulated. Finally, through practical examples, we compare the reliability indicator whether considering the user’s flexible comfort requirements and the building heat balance characteristics or not, which prove the improvement of the reliability of energy supply of the whole system of the proposed method.

Abstract

Demand-driven building control is an emerging approach to mitigate the increasing pressures on buildings and facilities for requirements of energy and comfort services. This study proposes a framework that integrates online learning capabilities to make building systems adapt to occupants’ actual energy and comfort demand. Based on the framework, two types of control strategies are developed: occupancy-based and thermalpreference-based demand-driven controls. Both of them have been implemented in an office building, keeping occupants in the loop of building operation under realistic conditions. This paper first introduces the proposed framework, and then presents two types of controls applied in for a case study. Lastly, lessons learnt from conducting them in the field tests are discussed.

Abstract

Based on the uncertainty surrounding the temporal correlation of wind power forecast error, an energy storage system (ESS) is applied to both a peak shaving mode and a plan following mode, and a multimode optimization model for a wind‐storage integrated system is proposed. Considering the large-scale mixed integer programming (MIP) problem, a peak shaving coefficient of ESS capacity and a two layer optimization algorithm is proposed. Thus, the problem can be solved iteratively, and capacity allocation can be evaluated in different modes. The simulation results show that pool purchase price, penalty price and the stochastic characteristics of wind power influence the optimal operation of a wind‐storage integrated system. The proposed model can realize reasonable allocation and efficient utilization of limited ESS capacity.

Abstract

This paper evaluates the airline productivity change by applying a modified global Malmquist productivity index (GMPI) model that incorporates both CO2 emissions and flight delays into the estimation model. Statistical inference is also performed on GMPI results using the bootstrapping method. Empirical research was conducted on 15 international airlines during 2011-2017. The empirical results showed the productivity of all airlines experienced a slight increase over 2011-2017. The results of GMPI and five driving factors of the 15 airlines were test to be reliable in most cases. Although efforts were made to restrain both CO2 emissions and flight delays, airline CO2 emission reduction was still inadequate to influence the productivity of airlines. Punctuality improvement did not facilitate overall productivity growth as expected. The additional cost paid by airlines to optimize their punctuality performance may not always lead to actual gains in productivity in the short term. Efficiency change and technological change were the major driving factors for the growth of airline productivity. Fifteen airlines had differed efficiency and technology features when considering the scale efficiency. Airlines need to choose targeted operational approaches to improve their productivity.

Abstract

In AC/DC hybrid distribution network with power electronic transformer (PET), the topology is more complex and the operation mode is more flexible. As a result, it is of significance to study the state estimation method of hybrid network. This paper starts from PET steady state model considering the converter loss, and then analyses its control method for AC/DC hybrid network. By adding the virtual nodes, a unified state estimation model for power electronic equipment is established. The pseudo-measurement equation is formulated according to the control equation of power electronic equipment to improve the redundancy of data. Finally, a state estimation method for AC/DC hybrid networks with PET is proposed. A test case of an AC/DC hybrid network with PET is used to verify the effectiveness of the proposed method.

Abstract

In the late period of oilfield exploit, the oilfield production water contains large amount of high temperature water the thermal energy of which should be recovered. The sewage source heat pump system (SSHP) has been widely used for this energy recovery, improving the energy utilization efficiency. However, the heat transfer and flow characteristics of oily wastewater spraying in the heat exchanger are different from the ordinary sewage heat pump system. In this paper, a three-dimensional numerical model was established for a spraying heat exchanger in the oily sewage source heat pump system, and a mixture of water and glycerin was used to simulate the oily wastewater. The VOF model was used to simulate the gas-liquid flow of the spray falling film of oily wastewater over a horizontal tube in the heat exchanger, and the effects of different glycerin content and spray density on heat transfer.

Abstract

This paper presents the heat dissipation problem of an integrated controller in-wheel motor. The temperature field of the in-wheel motor is calculated based on the finite element method. The temperature rise law of the stator winding and IGBT is analyzed, and a cooling channel structure which can simultaneously cool the in-wheel motor and the control system is proposed. The experimental results show that the cooling effect is optimal when the flow rate of the cooling water is 4 L/min, the winding temperature is reduced by 31 °C, and the IGBT temperature is reduced by 49.65 °C. The simulation accuracy error is less than 6.3 %, and the heat dissipation model has a high precision