A rapid evaluation method for design strategies of high-rise office buildings achieving nearly zero energy in Guangzhou

Highlights

• Establishing the typical high-rise office building in Guangzhou by survey.

• Defining the effective strategies for NZEB by parametric and sensitivity analysis.

• Developing a rapid and reliable evaluation tool for NZEB.

Abstract

The construction of nearly zero energy buildings (NZEB) has achieved dramatical impact on global warming and energy crises. It is still a challenge for designers to derive design strategies on how to achieve NZEB in the early design stage, because a complex modelling process with many input parameters of the current NZEB design and evaluation tool is still unavoidable. This article, therefore, aims to introduce a tool suitable for the rapid and reliable evaluation of NZEB design strategies for high rise office building in the city of Guangzhou in China. Firstly, a high-rise office building with typical geometry features is established by sensitivity analysis and survey, thereby the reference building consumption is obtained. Secondly, comprehensive simulations on cases with various envelope features, air conditioning performances and lighting control methods is carried out. Based on the sensitivity analysis on simulation results, key influencing parameters are selected out, effective strategies which fulfills “Technical standard for nearly zero energy buildings (NZEBTS)” are put forward. Finally, a parametric building energy evaluation model is built by regression analysis on simulation results. Combined with energy efficiency index from “NZEBTS”, an evaluation tool is developed to help designer determine NZEB strategies. The results revealed that the most effective strategies to achieve NZEB in Guangzhou are to apply high performance external windows, improve air conditioning systems and utilize intelligent zone-controlled lighting systems, meanwhile, the utilization ratio of renewable energy (η_s) should be more than 40% of building total annual energy consumption.

Introduction

Globally, the significant increase of fossil fuel consumption due to rapid development of human society and economy has triggered serious environmental issues such as global warming and energy crises, which seriously impacts our lives and the lives of future generations. Among which, the building sector has become one of the major energy consumers worldwide. Therefore, it is critical and urgent to come out with a thorough plan for effectively reducing the demand of energy. In the recent decades, more lights are shed to nearly zero energy building (NZEB), which consumes less energy while eases energy shortages and smooths climate changes. In other words, promoting NZEB has become a global trend, where related policies and development goals were established by many regions and countries globally, as well as the technical standards and systems. The European Union (EU) published the “CA EPBD report” [1] in 2016, including the zero energy building standards/energy regulations of major member states. “Advanced Energy Design Guide for K-12 School Buildings Achieving Zero Energy” [2] was issued in 2018, which is the first guidance document related to the design, construction and operation of zero energy building in the US. The “Advanced Energy Design Guide for Small to Medium Office Buildings Achieving Zero Energy” [3] was promulgated in the US in 2019. The “ZERO Code” [4,5] is currently being developed to set a “zero net carbon” pathway for new buildings. China also promulgated and implemented the “Technical standard for nearly zero energy buildings (NZEBTS)” [6] in 2019, which signifies a new beginning for Chinese building energy efficiency.

The current research on NZEB can be divided into two fields. The main category of the research is focusing on the interpretation and comparison of the standards for NZEB in different countries and regions, as well as the establishment of the appropriate technical systems. The standards of China, EU and American are different in terms of the scope of building energy consumption and the energy use targets, so the energy performance, design features and technical selection of their buildings are also different [7]. For public buildings, primary energy consumption is the main energy efficiency index in most European and American countries, while in China, the building energy saving rate (η_p), building energy efficiency improvement rate (η_e) and utilization ratio of renewable energy (η_s) are the common constraints [6].

While the other main category of research is focusing on the optimal solution to achieve nearly zero energy consumption for a building case. Some of them apply a single parameter analysis, such approach adopts direct modeling and simulation workflow in which the effect of altering the values of parameters on energy performance are evaluated one at a time, without considering the combined effect of parameters [8]. E. Pikas [9] conducted cost optimal and NZEB solutions for office buildings in the cold Estonian climate by 3 steps. Step 1 identified optimal ranges for wall insulation thicknesses, Step 2 analyzed window parameters to determine optimal window sizes, PV generation was in step 3. Similar literature such as studies by Muhammad Wasim Anwar [10], Ebrahimpour [11], Eshraghi [12] and Riahi Zaniani [13] investigated the possibility of reducing energy consumption by considering the geometry, the building envelope, the interior layout, and the mechanical system in a stepped-wise approach, without considering the combined effect of parameters. Others considered multiple variables simultaneously, such multi-variable parametric exploration techniques have led to dramatically broader and more feasible design solutions [14]. Maria Ferrara [15] conducted the ranking of the twelve combinations of three envelope systems with four energy systems and the definition of a cost-optimal set of design parameters for each envelope system/technical system combination. Gholamreza Heravi [16] identified cost-optimal options for a typical residential NZEB design in Kabul city. However, the costs and challenges of setting up the simulations for a large space of options is a barrier for broader application of this approach [17]. Therefore, in order to consider a comprehensive combination of different study variables while reducing computational time and cost, Roya Rezaee [18] proposed a parametric framework for a feasibility study of zero-energy residential buildings for the design stage, the paper developed a parametric model, considering both geometric prototypes and non-geometric parameters, which generated a large number of options for the analysis of building energy consumption and photovoltaic electricity generation. Current research is gradually transitioning from single-parameter analysis to multi-parameter analysis, through which the optimal nearly zero energy strategy solutions for many building cases have been perfectly solved. Although a lot of simulations and quantitative analysis have been done in the studies, there is no mathematical relationship between building energy consumption and the various energy consumption influencing factors, which lead the lack of a simple and intuitive tool to assist designers comparing different options efficiently.

In the early stages of NZEB design, all options should be considered comprehensively. The modelling process of IBE [19], which is currently used in China as a NZEB design and evaluation tool, is sophisticated and requires lots of parameters to be entered. The information needs to be constructed separately for each room on each floor, rendering it time consuming to compare options in the early stages of design. Considering this as a necessity, the paper offers a new rapid evaluation tool for high rise office building achieving NZEB in Guangzhou, which could quickly obtain the building energy consumption under the combined influence of multiple parameters, without detail building model in the early design stage, so as to determine the energy efficiency targets required and the effective strategies to achieve NZEB. Although there are significant differences in building energy consumption characteristics and approaches to achieve NZEB for different building type in different climate zone, the research method could be reference to establish the evaluation tool for different type buildings nationwide.