Simulation study of a dual-cavity window with gravity-driven cooling mechanism

Utilization of high temperature cooling sources or natural energy sources can potentially contribute to improving energy efficiency in buildings.In this study,a dual-cavity window with gravity-driven cooling mechanism(GDC window)was proposed to integrate the low-grade cooling sources into the glazing system for improving the thermal performance of the window.The embedded pipes circulated with low-grade cooling water are the key component of GDC window,which can remove the absorbed solar heat and reduce the heat gain through the window.A numerical model based on CFD simulation was developed to analyze the flow characteristic and heat transfer within the GDC window.Model validation was conducted by comparing the simulation results with measurement data obtained from previous study.Numerical simulations were carried out to compare the thermal performance of GDC window with that of conventional blinds window.Sensitivity analysis was performed to evaluate the influence of some design parameters on the flow characteristic and thermal performance of GDC window.The simulated results show that compared with the blinds window,the GDC window reduces 57.4%and 40.4% of heat gain in summer for the low-grade cooling water of 18℃ and 25℃;respectively.Reducing the flow resistance within the GDC window is significant for improving the heat removal performance of the embedded pipes.This study provides an alternative solution to integrate the low-grade cooling sources into the glazing system for enhancing the energy-efficiency and decreasing the building energy demand in cooling-dominated buildings.

Design and control optimization of energy systems of smart buildings today and in the near future

Buildings contribute to a major part of energy consumption in urban areas, especially in areas like Hong Kong which is full of high-rise buildings. Smart buildings with high efficiency can reduce the energy consumption largely and help achieve green cities or smart cities. Design and control optimization of building energy systems therefore plays a significant role to obtain the optimal performance. This paper introduces a general methodology for the design and control optimization of building energy systems in the life cycle. When the design scheme of building energy systems is optimized, primary steps and related issues are introduced. To improve the operation performance, the optimal control strategies that can be used by different systems are presented and key issues are discussed. To demonstrate the effect of the methods, the energy system of a high-rise building is introduced. The design on the chilled water pump system and cooling towers is improved. The control strategies for chillers,pumps and fresh air systems are optimized. The energy saving and cost from the design and control optimization methods are analyzed. The presented methodology will provide users and stakeholders an effective approach to improve the energy efficiency of building energy systems and promote the development of smart buildings and smart cities.