第五章 結論與討論
5.3 計畫成果自評
既有建築設施的能源管理是一個重要、而有挑戰性的課題。我國大專校院內各使 用單位管理者在面對能源管理、降低各單位總耗能量之課題時，常遭遇以下三個困境：
無法得知該單位之「實際耗能量」、缺乏適用的評估基準、無法獲知最具節能潛力的改 善方向。有鑑於此，本研究研發出一套建築能源管理系統（Benchmarking Energy Efficiency by 'Space Type', BEEST），試圖協助大學校園內各使用單位提升其能源管理 效率。BEEST 的核心概念是針對某使用單位之各類「空間」、界定「標準使用模式」，
以估算出其「標準耗能量」，作為該單位之耗能量標竿值。BEEST 可以比較某單位之
「實際耗能量」與「標準耗能量」後，得知其「能源效率」；進而找出導致該單位能源 效率不彰之原因；最後本研究對症下藥、提出節能措施與建議。本研究以台科大建築 系及其所屬設施為例，建立滿足各類空間最低耗能需求之使用模式，進行 BEEST 實 例操作並提出相關改善建議。
關於研究學理創新之處，相對於其他大多數研究以同類建築設施之平均耗能量作 為絕對指標值，本研究提出一套「標準耗能量」之概念與方法，更能協助找到適用於 個別使用單位的相對指標值，並可指出節能改善方向。
整體而言，本研究已如期完成原計畫擬定之研究工作，研究成果與原計劃大致相 符，並能達成當初設定之預期目標。本研究之成果已經整理成三篇論文、並已發表於 重要國際學術期刊及研討會中：
國際學術期刊論文－
1. Journal of Asian Architecture and Building Engineering（SCI 期刊）：2012 國際學術研討會論文－
2. 綠建築評估方法國際研討會（葡萄牙波多，iiSBE）：2012 3. 設施管理與維修國際研討會（巴西聖保羅，CIB W070）：2010
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Benchmarking Energy Efficiency by 'Space Type':
An Energy Management Tool for Individual Departments Within Universities
Kung-Jen Tu*1 and Cheng-Hong Lin21 Assistant Professor, Department of Architecture, National Taiwan University of Science and Technology, Taiwan
2 Graduate Student, Department of Architecture, National Taiwan University of Science and Technology, Taiwan
Abstract
'Energy management' is a challenging task for individual departments within universities, especially when several departments occupy the same facility. To assist individual departments in dealing with the complex energy management topics, this study aims to establish the Benchmarking Energy Efficiency by Space Type (BEEST) method. The BEEST is developed around the core concept of 'space type'. It is proposed that the spaces within a department be categorized into several 'space types'; and for each space type, its 'standard operation settings' be defined to further estimate the 'standard energy consumption' for the department, with energy prediction module such as eQuest, as its energy consumption benchmark. The energy efficiency index of a department and its facility can then be assessed by comparing its 'actual energy consumption' against the estimated 'standard energy consumption. The problem areas can be identified and energy saving action plans recommended by conducting further analyses, such as energy analyses by space types, floors, and equipment types as well as sensitivity analyses of the energy reduction effects of various 'standard settings'.
The Department of Architecture of the national university NTUST in Taiwan is used as a case to demonstrate how the BEEST functions as an effective energy management tool.
Keywords: facility management; standard operation settings; standard energy consumption; energy efficiency index 1. Introduction
'Energy management' has become an important facility management issue for universities in Taiwan.
Individual departments within universities are usually held responsible for managing the energy efficiency of their facilities. This becomes an even more challenging task when several departments occupy the same facility. Two obstacles lie in front of individual departments. First of all, the actual amount of energy consumed by each department is usually unknown and hard to estimate: The actual energy consumption of a 'facility' might be measured and monitored; but the actual energy consumptions of the 'individual departments' in the same facility would be difficult to estimate correctly, due to the different work processes and energy demands that might exist among these departments. Secondly, individual departments lack reasonable energy consumption benchmarks or indices.
For example, the national average of energy use intensity for universities (EUI, 120.8 kWh/m2-yr) is the only referable benchmark. However, this benchmark
has failed to become an effective reference. As revealed by an earlier domestic study, the energy consumptions of the thirteen buildings in a certain university varied greatly (ranging from 63.6 to 220.1 kWh/m2-yr), due to large variances in building characteristics, occupancy use patterns and energy needs among different departments (Tu et al., 2010). In such a case, the national average EUI 120.8 kWh/m2-yr is meaningless for those departments/ buildings with lower EUIs and may be unattainably low for those with extremely high EUIs. Individual departments need an effective energy management tool that is capable of establishing reasonable energy consumption benchmarks catering to departments' functional and energy needs as well as diagnosing the energy performance of departments' facilities.
To assist individual departments in their complex energy management tasks, this paper aims to develop the Benchmarking Energy Efficiency by Space Type (BEEST) method. The core concepts of the BEEST methodology will be described, and the procedures and results of applying the BEEST will be demonstrated, step by step, in a case (the Department of Architecture of the national university NTUST).
2. Literature Review
This study has reviewed the existing literature focusing on the energy management aspects of 'existing buildings' and categorized them into two
*Contact Author: Kung-Jen Tu, Assistant Professor, Department of Architecture, National Taiwan University of Science and Technology, 43 Keelung Rd., Section 4, Taipei, 106, Taiwan Tel: +886-2-2737-6512 Fax: +886-2-2737-6721
E-mail: [email protected]
( Received October 5, 2011 ; accepted July 24, 2012 )
groups based on their research objectives. The first group involved diagnosing the energy efficiency of a 'building or system', proposing improvement plans (such as installing external shading devices), and employing energy simulation software to assess the magnitude of energy savings achieved by various plans (Zhu, 2006; Hatamipour, 2007; Sun and Lee, 2006). The approaches taken often involve in-depth investigation and large scale refurbishment, and incur high costs. They thus are not useful for departments in universities, who simply need a tool to perform preliminary evaluation on the energy efficiency of their facilities and to identify problem areas first.
The second group of studies typically involved developing energy efficiency scales or evaluation methods to measure and compare the energy efficiencies of various buildings. For example, in Hong Kong, the Building Environmental Assessment Method (HK-BEAM) was developed to measure the energy performance of buildings against the 'baseline building' (Lee et al., 2007); besides, a ten-level scale was defined to assess the energy efficiency of supermarket facilities (Chung et al., 2006). In the Netherlands, the EPA-ED was established to measure the energy efficiency of existing housing and establish national energy consumption benchmarks (Poel et al., 2007). In Sweden, energy consumption benchmarks for two different classes of hotel chains were developed respectively (Bohdanowicz and Martinac, 2007). In Singapore, a three-level energy efficiency scale was established and criteria defined for office buildings (Haji-Sapar and Lee, 2005). In summary, these energy efficiency scales produced an 'efficiency score' to indicate the energy performance at the 'building' level; yet they fail to inform a 'department', that often occupies only a certain floor of a building, much about
the energy efficiency of its facility.
3. Methodology of the BEEST
Several core concepts underlie the methodology of the BEEST. First of all, it is proposed that the spaces in a department be classified into several 'space types'. Then, for each space type, its typical 'standard operation settings' such as occupancy use patterns, environmental quality, building systems and equipment characteristics are defined and used to estimate the 'standard energy consumption' of the department (regarded as its energy consumption benchmark).
Then, its 'actual energy consumption' is compared against its 'standard energy consumption' to yield its 'energy efficiency index', indicating the overall energy performance of the department and its facility.
3.1 Space type
A department in a university in Taiwan often occupies a portion of a facility (across several floors).
Usually, the spaces within a department can be categorized according to their occupants and 'functional uses' (Fig.1.). In the same type of space, the tasks and processes performed by its occupants, the occupancy use patterns (operation schedule and occupant density), task-supporting equipment, as well as the environmental quality needed could be quite similar.
This paper thus argues that the energy consumptions (per square meter) of the same type of space may be quite close, if other variables such as external weather conditions, building envelope and building control systems are kept the same. Conceptually, an effective yet reasonable 'standard energy consumption' can be identified and established as the benchmark of each space type. The 'standard energy consumption' of all types of spaces of a department can then be added up to the 'standard energy consumption' for the department.
Fig.1. Core Concepts of the BEEST: Type of Space, Standard Settings, Standard Energy Consumption and Energy Efficiency Index Figure 1
Type of space A
Space A-3 … Space A-2 Space A-1
Type of space B
Space B-3 …
Standard settings -Type A Environmental quality A Lighting system scheme A Occupancy use patterns A ---Standard energy consumption A
Standard settings -Type B Environmental quality B Lighting system scheme B Occupancy use patterns B ---Standard energy consumption B
Standard settings -Type C Environmental quality C Lighting system scheme C Occupancy use patterns C ---Standard energy consumption C
Standard
3.2 Standard settings & standard energy consumption This study has proposed that the following 'standard operation settings' be defined for all 'space types' in a department (Fig.1.):
1. Standard environmental quality: the preferred illuminance of each space type; set point temperature of the HVAC systems.
2. Standard lighting system scheme: lighting fixture type and fixture density of each space type.
3. Standard occupancy use patterns: the occupant density, schedule profile, major equipment density, and supplementary equipment density of each space type.
Conceptually, these 'standard settings' are defined in such a way that they represent the most reasonable and effectively regulated way of operation (energy-wise) for each space type. Consequently, a certain type of space operating under its 'standard settings' is expected to consume the least amount of energy possible, i.e. the 'standard energy consumption' of that space type. The summation of the standard energy consumptions of all spaces is defined as the 'standard energy consumption' of the department (Fig.1.). Similarly, it represents the minimal energy consumption of the department, and is considered as the energy efficiency benchmark for the department (measured in kWh/m2 -yr or –month, same as EUI).
The 'standard EUI' of a 'space' is affected not only by its 'standard settings' but also other factors such as the existing external weather conditions, building characteristics (orientation, floor dimensions, building envelope, etc), and HVAC system schemes. It is suggested that data of all factors of all types of spaces be input to and modeled by various energy simulation software (ex. eQuest) or energy prediction models.
3.3 Energy efficiency index
The 'energy efficiency index (EEI)' of a department, defined as the ratio of its 'actual EUI' to its 'standard EUI' (%), is used to indicate the energy performance of a department and its facility (Fig.1.). Since the 'actual EUI' is usually larger than the 'standard EUI', the EEI of a department normally exceeds 100%. The larger the EEI is, the less energy efficient a department is. When the 'actual EUI' of a department can not be physically measured, it is advised that it be estimated by various energy simulation software or other energy prediction models.
The term 'variable energy consumption' is further defined as the 'variable' portion of its 'actual EUI' that exceeds its 'standard EUI' (calculated by subtracting its 'standard EUI' from its 'actual EUI'). It is equivalent to the portion of the EEI that exceeds 100% and represents the portion of energy that can be potentially saved. For example, an EEI of 120% means that the 'variable EUI' is 20% of its 'standard EUI'; and the department has a 20% energy saving potential if its 'existing operation conditions' can be changed to its 'standard operation settings'.
4. Theoretical framework of the BEEST
Implementing the above core concepts, the Benchmarking Energy Efficiency by Space Type (BEEST) method was developed to assist institutions or departments in diagnosing the energy performance of their facilities. The theoretical framework of the BEEST consists of three major parts (Fig.2.).
4.1 Input data
The BEEST collects the following three types of input data from a department (Fig.2.):
1. Existing climate and building infrastructure: include the climate conditions around the site, building envelope characteristics of the building, and HVAC system schemes installed in the occupied spaces.
These are considered the 'fixed' building conditions given to the department and are less likely to alter due to the high costs typically involved.
2. Existing operation conditions: include the existing status of the environmental quality, lighting system schemes, and the occupancy use patterns in all space types. These are considered the 'actual and usual' conditions under which the department is operating.
2. Existing operation conditions: include the existing status of the environmental quality, lighting system schemes, and the occupancy use patterns in all space types. These are considered the 'actual and usual' conditions under which the department is operating.