Search

The purpose of this study is to propose a control method that optimizes the set point of the variable air volume (VAV) terminal unit using real-time prediction model of indoor thermal and air environment and energy consumption. Indoor thermal environment and air environment are predicted through indoor load and carbon dioxide (CO2) concentration. A prediction model was developed through operation data of the VAV terminal unit by artificial neural network (ANN) algorithm. The developed prediction model was used for real-time set point control of the VAV terminal unit. The optimal control of VAV terminal unit can be expressed in 3 step. First, it predicts the current indoor load and CO2 concentration. Second, all supply temperatures and supply air flow rate that can be provided in the predicted condition are repeatedly simulated. Finally, the set point of the minimum energy consumption is applied to the control. The evaluation of the proposed control method was compared with the dual maximum control logic. Comparative evaluation was performed using TRNSYS. It was confirmed that the proposed control method reduced the reheat coil energy consumption by about 20% and the air supply fan energy consumption by about 17% compared to the existing control method.

In this work, the quaternary ammonium salt small molecule inhibitors with melamine and sodium chloroacetate as raw materials was synthesized and it has certain inhibition on the hydration swelling of bentonite. Through linear swelling test, mud ball test and drilling fluid performance evaluation, its inhibition performance in clay is evaluated. The results show that the linear swelling rate of bentonite in 0.5% MAA-3 solution is 57.28% at 90 min, which is similar to that in 4.0% KCl solution.

Electric vessels have developed rapidly with the advancement of transportation electrification in recent years. The power battery capacity of large vessels usually reaches several MWhs, in which case battery change technology is more applicable. A vessel charging and battery swapping station has the dual attributes of power utilization and energy storage and can realize Vessel to Grid through charging and discharging facilities. Aiming at the scenarios of interaction between vessel charging and battery swapping stations and the power grid, this paper studied technical requirements of several participants, established an input-output analysis model and analyzed multiple influencing factors. The results show that revenues cannot be increased effectively with the increase of the number of spare batteries alone; the interactive service can achieve a balance of payments when the battery cost is higher than 1.4 ¥/ Wh, and; benefits may not be gained when the battery life is less than 5 years.

Power companies are mainly capital-intensive companies, and the efficiency of working capital management has a profound impact on the sustainability and stability of the development of power companies. This paper uses the DEA-CCR method to measure the working capital management efficiency of listed Chinese power companies from 2014 to 2019, and uses the Tobit regression method to analyze the factors that affect the working capital management efficiency. The results show: (1) The overall efficiency of working capital management of listed Chinese power companies is low, and there is still much room for improvement. (2) Decomposition of comprehensive technical efficiency results in pure technical efficiency and scale efficiency, both of which have an important impact on the overall working capital management efficiency of listed Chinese power companies. (3) Among listed electric power companies, the overall working capital management efficiency of central enterprises is lower than that of non-central enterprises. In response to the above conclusions, this article proposes measures such as reforming the working capital management system, optimizing the profitability of core businesses, and improving supply chain capital management to improve the working capital management efficiency of listed electric power companies.

Focusing on the battery-charging problem that is brought to the electric automobile users, this paper integrated the “automobile-network-path” multi-source information and presented the multi-level user experience index system which combined charging prices, driving distances, degrees of traffic congestion and other factors. The recommended algorithm and model for charging strategy was built up to improve the user experience. Meanwhile, it invoked map Application Programming Interface (API) to plan multiple paths. Consolidated by the status of charging piles, the distance between the automobile and the piles, the charging prices along with more real-time information, the multi-level user oriented experience index system was set up to recommend an optimal navigation route to the charging station for the automobile owners. Validated by the application results, the proposed algorithm that helped navigate to the charging stations or piles can effectively solve the practical problems1 such as difficulty in orienting the charging piles, waiting in lines, and high charging fees.

Travel anxiety of automobile owners has been aggravated because of the difficulty in accurately controlling the operation energy consumption and imperfection in charging infrastructure construction and other problems. Relying on the massive historical operation data of automobiles, it acquired the powerconsumption increasing coefficient of speed and temperature by means of clustering and control variable methods. Furthermore, the map Application Programming Interface (API) was invoked to obtain the path planning results thus realizing prediction on power consumption. The historical charging data of current automobile was used to build the mapping relations of the state of charge (SOC) and the state of energy (SOE). Combining with the prediction value of energy consumption it calculated the needed charge capacity and judge whether to issue the charging demand alert. Indicated by the application results, the proposed algorithm of energy-consumption forecast is more accurate than traditional average energy-consumption forecast algorithm. Accordingly, the charging demand alert function can effectively relive the travel anxiety of automobile owners.

In the design of hydraulic structures, it is common to deal with the supercritical flow. Abrupt expansion structure represents a type of transition often constructed in manmade hydraulic structure (e.g. chutes in dam structures, sewer or drainage system, an irrigation channel, etc.) to cater the geometry difference. It is important to cater to the design of such transition especially it involves flow with high velocity. The flow features of high-velocity flow at sudden expansion channel are studied. A two-dimensional depth-averaged model (DA model) incorporate with Constrained Interpolation Profile (CIP) scheme is developed to simulate the supercritical flow at the abrupt expansion channel. The numerical model is able to reproduce the flow features of supercritical flow at the abrupt expansion structure. The simulated results are compared with the analytical solution with a different degree of agreement is observed. The same numerical setup is applied to the model generated by FLOW-3D model. The numerical results from the DA model and FLOW-3D model are compared with previous experimental results. The simulated results from the DA model showed better agreement with the experimental results.

The low wind-pressure conductor is a dedicated conductor which obtains low wind resistance coefficient by changing the sectional shape of the conductor and has extensive application prospect in electric power transmission lines in strong wind areas. Previous wind tunnel testing results showed that the wind resistance coefficient in unit length of the low wind-pressure aluminium conductor steel reinforced was obviously lower than that of the conventional aluminium conductor steel reinforced, and the control factors of manufacturing process of the low wind-pressure conductor were proposed. In this paper, the low wind-pressure aluminium conductor steel reinforced JLX1/G1A(DFY)–680/45–338 was designed based on the structure optimization of the conventional aluminium conductor steel reinforced JL/G1A–630/45–45/7, and the service performance study of the conductor was carried out. Results showed that the mechanical properties, electrical properties and construction properties of the low wind-pressure conductor fully satisfied service requirements, and the conductor can be popularized and applied for transmission lines in strong wind areas.

The breeze vibration duration of conductors is long, the vibration amplitude is strong and the frequency range is wide for electric power transmission lines in strong wind areas, which seriously affects the safe and stable operation of transmission lines. There are two design schemes of conductors which can achieve the purpose of reducing wind-induced disaster. One is enhancing the structural strength of conductors to withstand wind load, but the investment is enormous and the effect is limited. The other is developing drag reduced conductors to reduce wind load by changing conductor structure. This paper started from application feasibility analysis of drag reduced conductors and designed four drag reduced conductors by structure optimization of the conventional aluminium conductor steel reinforced JL/G1A-630/45-45/7, denoted as DFY630/45(45°)-R3.5, DFY630/45(60°)-R3.5, DFY630/45(45°)–R3.2 and DFY630/45(60°)-R3.2, respectively. The wind tunnel test was performed and the wind resistance coefficients in unit length of five conductors were compared. Result showed that the wind resistance coefficients in unit length of four drag reduced conductors were obviously lower than that of the conventional conductor. By controlling the manufacturing process, popularization and application of drag reduced conductors for transmission lines in strong wind areas can be realized.