Abstract

Configuration and working fluid are the two important factors that influence Organic Rankine Cycle (ORC) performance. Superstructure technology, which contains as much as possible ORC architecture features, is considered as cutting-edge artificial design technology to ORC configuration, however, it leads to intrinsic difficulty for modelling and calculation. In order to overcome the weakness and to achieve structure construction and fluid selection simultaneously, a nested three-level algorithm employing evolutionary algorithm, sequence quadratic programming (SQP) and 0-1 programming is proposed. Based on HEATSEP simplification method developed by Lazzaretto, ORC structure with different architecture features is decomposed into several elementary cycles sharing one to three of four thermodynamic processes, and this form of combination for elementary cycles is called topology combination. By using real number coding for design parameter and binary coding for topology parameter, evolutionary algorithm based on computational intelligence is adopted to generate ORC structure without artificial design. Using 0-1 programming with working fluid selection coefficient in the outer-level algorithm, simultaneous achievement of fluid optimization and structure design of ORC is realized. A case study is done after verifying accuracy of the algorithm by reference data, with a predefined set of 13 organic fluids. The results show that both intelligent construction for ORC structure and selection of optimum pure organic fluid can be achieved by the algorithm preliminarily in terms of maximum net power output.

Abstract

This paper investigated the energy performance of an innovative double skin façade integrated semitransparent photovoltaic and optimized the design parameters and the operation mode. The simulation model was built and utilized with Grasshopper plug-in Ladybug and Honeybee. The overall energy performance of the innovative DSF-PV including thermal, day lighting and electricity productive performance was investigated in the numerical model. The result indicates that the optimal dimension of this innovative DSF-PV is 0.5m air gap depth, 3.6m floor height, and 0.45 height of the top and bottom opening. The optimal operation mode pf DSF-PV in Tianjin is natural ventilation in cooling season and No ventilation in heating season, which can save about 20%~23.95% energy consumption. The power generation of the PV façade can achieve about 70KW h per unit area, electricity yearly in Tianjin, that is considerable potential for office building integrated the PV façade on the external skin. Thus, if the optimal operation mode of DSF-PV, the overall energy performance conversion efficiency would be improved.

Abstract

The solid-state electric heating thermal storage system is an emerging large-capacity peak shaving technology in the power grid. The studying of the heat transfer matching characteristics is of great significance for improving reliability and heat transfer performance of the solid-state electric heating thermal storage system. In this paper, by establishing the heat transfer rate balance equation and the performance evaluation criteria, the correlation between the design parameters and heat transfer matching of the thermal storage system is analyzed. The results show that the temperature of the thermal storage unit increases linearly with the increase of electric model heating power, decreases exponentially with the increase of hole ratio and circulating wind speed. The reduction of the electric heating power and the increase of the circulating wind speed can enhance the heat efficiency and the temperature uniformity. However, the turn-on of the circulating wind will cause a sudden change of heat efficiency and the temperature uniformity. Changing the hole ratio has little effect on the heat transfer matching performance. The experimental verification proves that through the Multi-parameter collaborative optimization, better heat transfer matching performance can be achieved.

Abstract

A numerical analysis of heat and mass transfer in an indirect evaporative cooling system for building applications is presented. The model is based on the computational fluid dynamics software CFX-4 and makes use of the built-in Spray Drier model to study the droplet movement, heat transfer, and evaporation rate from the water to the exhaust air. The effect of the average droplet size and mass flow rate as well as the angle of the heat exchanger on the cooling performance to the supply air is reported.

Abstract

Plug-in hybrid electric bus (PHEB) have more potential fuel efficiency than traditional hybrid electric vehicle (HEV) [1]. For rule-based energy management, the fuel consumption can be significantly influenced by vehicle architectures and driving condition. Firstly, a specific PHEB transmission configuration utilizing two planetary gear sets was determined for urban road conditions, and different driving modes have been divided by controlling the clutch state. A PHEB model is built by MATLAB/Simulink in accordance with rule-based strategy characterized as a flow chart. Simulation results on china city bus cycle (CCBC) show that fuel economy (13.90 L/100km) still have room for improvement compared with dynamic programming (DP) based energy management strategy (EMS).

Abstract

District heating (DH) systems play an important role in increasing the share of renewable energy utilization. In this study, the operation of the still new concept of a prosumer in a DH system by means of mathematical modelling was analysed. The DH ring of a university campus was investigated to find out the consequences of datacenter waste heat energy exploitation on the operation of DH. Based on fundamental equations from continuum mechanics, the hydraulic and thermal parts of the system were modelled and developed in MATLAB. The scenarios for network performance improvement were introduced and investigated. The result showed that integrating waste heat to DH grids might cause pressure imbalance in substations located close to the prosumer. Variable speed pump control together with valve flow control wasfound as an alternative solution to solve this issue. Lowering temperature levels in the DH grid led to heat energy saving in distribution pipes, while reduced annual waste heat recycling. Despite the assumptions and simplifications applied, the result indicated the main features, advantages, and disadvantages of integration of a prosumer to DH grids.

Abstract

To study the power generation characteristics of a thermoelectric module under low temperature, a test system was built to measure the thermoelectric performance of semiconductor modules in low temperature environments, and the influence of the loading pressure and the hot and cold end temperatures of the temperature difference power generation module on the module performance is measured. The results show that the power generation performance of the module increases with the increase in the load pressure, but the rate of increase decreases gradually. The performance of the module under low- temperature conditions is much lower than that under normal temperature conditions. When the temperature at the cold end interface is –110 °C and the temperature difference between the hot and cold ends is 51.0 K, the maximum output power is 0.28 W, and the maximum efficiency is 0.38%. Compared with the room temperature power generation under the same temperature difference,the power is approximately 1W lower, and the efficiency decreases by 78%.

Abstract

The pump-storage system is used to improve the reliability of water supply, particularly in locations where water supply is unreliable. However, the drawbacks of this system are excessive pumping and water loss to tank overflow. Therefore, an operational optimisation is proposed to address these challenges. This paper presents a linear programming model to minimise the operating cost of the proposed system under the timeof-use (TOU) electricity tariff. The model is applied to a practical case study and solved by the solving constraint integer programming (SCIP) solver in MATLAB’s OPTI toolbox. Simulation results show that the proposed approach eliminates water loss to tank overflow and improving energy savings by up to 18.3%.

Abstract

Based on the current situation and development planning of Meishan Planning Area Ningbo Province, this paper obtains a preliminary plan for cold energy utilization by analyzing the characteristics and feasibility of different LNG cold energy utilization methods. In order to improve the utilization ratio of LNG cold energy, this paper proposes a cascade utilization scheme for rubber cryogenic comminution, Meishan Ice and Snow World refrigeration and coastal fresh preservation storage, and builds a integrated LNG cold energy utilization industrial chain and determines the process of gradient utilization. Through economic analysis, it is concluded that cold energy utilization of LNG has great economic benefits.

Abstract

The ventilated exhaust-air window provides an approach to combine the window system with exhaust air heat recovery. This new window can act as a heat exchange to recover the heat or cold of the exhaust-air to mitigate the heating or cooling load of the window. The zonal model is a reliable method to analyze the two-dimensional heat transfer of the ventilated exhaust-air window. However, the optimal subsection number of the zonal model for evaluating the thermal performance of the ventilated exhaust-air window has not been identified. In this study, a sensitivity analysis is carried out to estimate the effect of the subsection number on the simulation results of zonal model, and to identify the suitable and recommended subsection number for the numerical modeling of the ventilated exhaust-air window. The results indicated that reducing the subsection number in vertical direction will lead to a higher calculation deviation. In current case studies, the subsection number of 10 for the zonal modeling can zonal model can predict the thermal performance of the ventilated exhaust-air window with promising accuracy, while spending less computation time.