Development of a multicriteria tool for optimizing the renovation of buildings

The renovation of a building involves not just the fulfilment of functional requirements, but also considerations such as energy consumption, investment costs, environmental impact and wellbeing. As things stand, new design methods and tools are needed, and the aim of the research presented in this article was to develop a multicriteria tool, MultiOpt, for the optimization of renovation operations, with an emphasis on building envelopes, heating and cooling loads and control strategies. MultiOpt is based on existing assessment software and methods: it uses a genetic algorithm (NSGA-II) coupled to TRNSYS, and economic and environmental databases. This article illustrates its utilization in the renovation of a school in the southern French city of Nice which was representative of France’s building stock. The study started with the monocriterion optimization of energy consumption, cost, thermal comfort, and life-cycle environmental impact. It then moved onto multicriteria optimizations. The monocriterion analyses focussed on the building’s characteristics and performance; the multicriteria analyses were concerned with the interactions between the different objectives, and with identifying their convergences and divergences. The results demonstrated that MultiOpt can be used to compare different combinations of options and constraints, thus constituting a basis for operational decision-making.     

A solar thermal cooling and heating system for a building: Experimental and model based performance analysis and design

A solar thermal cooling and heating system at Carnegie Mellon University was studied through its design, installation, modeling, and evaluation to deal with the question of how solar energy might most effectively be used in supplying energy for the operation of a building. This solar cooling and heating system incorporates 52 m² of linear parabolic trough solar collectors; a 16 kW double effect, water-lithium bromide (LiBr) absorption chiller, and a heat recovery heat exchanger with their circulation pumps and control valves. It generates chilled and heated water, dependent on the season, for space cooling and heating. This system is the smallest high temperature solar cooling system in the world. Till now, only this system of the kind has been successfully operated for more than one year. Performance of the system has been tested and the measured data were used to verify system performance models developed in the TRaNsient SYstem Simulation program (TRNSYS). On the basis of the installed solar system, base case performance models were programmed; and then they were modified and extended to investigate measures for improving system performance. The measures included changes in the area and orientation of the solar collectors, the inclusion of thermal storage in the system, changes in the pipe diameter and length, and various system operational control strategies. It was found that this solar thermal system could potentially supply 39% of cooling and 20% of heating energy for this building space in Pittsburgh, PA, if it included a properly sized storage tank and short, low diameter connecting pipes. Guidelines for the design and operation of an efficient and effective solar cooling and heating system for a given building space have been provided.     

太阳能-地源热泵系统的运行模拟

以济南市某工程为例,使用DeST软件对该工程进行年逐时负荷模拟,得到冷负荷峰值为313.3 kW,热负荷峰值为293.7 kW,累计年排热量为166 451 kW·h,累计年提热量为210 380 kW·h,热不平衡率为20.88%。利用TRNSYS软件建立了太阳能-地源热泵系统动态模型,并进行模拟分析。当地土壤初始温度均为15.3℃,复合系统的模拟结果显示系统运行20年,地温均值一直保持在14.8~16.4℃的稳定范围内。研究表明:太阳能-地源热泵复合系统具有良好的蓄热能力,提高了太阳能利用率,可有效解决寒冷地区地源热泵的冷热不平衡问题,是解决严寒地区供暖问题的一个重要途径。     

土壤源热泵系统建模及运行参数优化

地埋管换热器的优越性能在当今社会越来越受到重视,在供暖、烘干、能源互补利用方面有广阔的前景。本文基于TRNSYS软件建立上海某建筑的模型系统设计,并介绍了建筑负荷模拟的过程、冷却塔串联和并联方式的模拟计算。针对上海的天气情况、土壤源温度的变化作为原始变量进行了模拟分析,比较得出性能好方案,最后进行较好方案的继续优化。     

严寒地区土壤源热泵系统地埋管特性影响研究

对土壤源热泵应用地埋管材料及热物性进行研究,以长春市某公共建筑为研究对象,采用控制面积分区热补偿法对地源热泵的供热供冷面积进行设计。针对严寒地区的气候条件,利用TRNSYS软件搭建地源热泵系统模型,模拟系统长期运行的土壤温度变化,结果表明合理选用地埋管材料与循环介质情况下土壤源热泵系统在严寒地区的运行状态可以达到基本稳定。     

Dynamical building simulation: A low order model for thermal bridges losses

Thermal bridges losses represent an increasing part of heat losses owing to significant three-dimensional heat transfer characteristics in modern buildings, but one-dimensional models are used in most simulation software for thermal analyses to simplify the calculations.State model reduction techniques were used to develop low-order three-dimensional heat transfer model for additional losses of thermal bridges, which is efficient and accuracy. Coupling this technique with traditional one-dimensional model for walls losses, it is possible to reduce a large amount of time simulations.Low-order model was validated from frequency response and time-domain output. And the effect of this model was shown with its implementation in software “TRNSYS”.     

基于TRNSYS的土壤源热泵热平衡问题的影响因素分析

夏热冬冷这种冷负荷占优地区,若由土壤源热泵系统承担所有的空调负荷,则会造成全年土壤取放热量的不平衡,从而出现常年运行后土壤温度的逐渐上升,降低系统夏季的运行效率,不利于系统持续稳定高效的运行。为此首先利用模拟软件TRNSYS搭建土壤源热泵系统模型,对土壤源热泵系统长期运行性能进行模拟分析,从冬夏累计负荷比、埋管间距、埋管深度、土壤导热系数、回填料导热系数这几个影响因素出发,研究土壤源热泵长期运行的热平衡问题,以期对土壤源热泵系统的合理应用和发展提供支持。     

太阳能-地源热泵系统双地埋管群利用方式研究

以天津地区一项太阳能地源热泵系统工程实例为研究对象,针对其太阳能储热利用率较低的问题提出了将其两个地埋管群互通互联的解决方案。通过对每个系统进行20年的模拟预测,发现采用了互通互联的两个系统储热利用率较原系统有所增加,系统COP得到了提升。双机组双地埋管群系统运行20年的平均COP可达3.54,单机组双地埋管群系统运行20年的平均COP可达3.36,分别比双机组独立地埋管群系统提高7.9%和2.4%。双地埋管群的改造方案的优越性明显,为太阳能地源热泵系统的应用提供借鉴。     

Transient simulation of a solar-based hydrogen production plant with evacuated tube collector and ejector refrigeration system

This article is a careful examination of an energy poly-generation unit integrated with an evacuated solar thermal tube collector. A proton exchange membrane (PEM) electrolysis unit is used for hydrogen production, an ejector refrigeration system (ERS) is utilized for cooling demand, and a heater unit is used for heating demand. All sub-systems are validated by considering recent articles. Cooling and heating demand, as well as the net output power are calculated. The modeled poly-generation system's exergy and energy efficiency are maximized by considering the inlet temperature of the heat exchanger and primary pressure of the ejector with the parametric evaluation of the system. The proposed poly-generation set-up can produce cooling load, heating load, and hydrogen with amounts of 5.34 kW, 5.152 kW, and 63 kg/year, respectively. Based on these values, the energy ef?ciency, and exergy ef?ciency are computed to be 64.14%, and 49.62%, respectively. Higher energy and exergy ef?ciencies are obtained by reducing high pressure of the refrigeration cycle or decreasing the temperature outlet of an auxiliary heater. The heat exchanger and thermal energy storage unit have the highest cost rate among all system components with 73,463 $ and 46,357, respectively. Parametric study indicates that the main determinative elements in the total cost rate of the system are the heater, and the solar collector.