Artificial neural networks for energy analysis of office buildings with daylighting

An artificial neural network (ANN) model was developed for office buildings with daylighting for subtropical climates. A total of nine variables were used as the input parameters – four variables were related to the external weather conditions (daily average dry-bulb temperature, daily average wet-bulb temperature, daily global solar radiation and daily average clearness index), four for the building envelope designs (solar aperture, daylight aperture, overhang and side-fins projections), and the last variable was day type (i.e. weekdays, Saturdays and Sundays). There were four nodes at the output layer with the estimated daily electricity use for cooling, heating, electric lighting and total building as the output. Building energy simulation using EnergyPlus was conducted to generate daily building energy use database for the training and testing of ANNs. The Nash–Sutcliffe efficiency coefficient for the ANN modelled cooling, heating, electric lighting and total building electricity use was 0.994, 0.940, 0.993, and 0.996, respectively, indicating excellent predictive power. Error analysis showed that lighting electricity use had the smallest errors, from 0.2% under-estimation to 3.6% over-estimation, with the coefficient of variation of the root mean square error ranging from 3% to 5.6%.     

Daylighting and energy implications due to shading effects from nearby buildings

Daylighting has long been recognized as a potential energy-efficient design strategy for buildings. Natural light can help reduce the electrical demand and the associated sensible cooling load due to artificial lighting. In Hong Kong, however, many buildings are constructed close to each other and hence the external environment plays a significant role in daylighting designs. This paper investigates the shading effects due to nearby obstructions when daylighting schemes are being employed. We used the computer simulation tool, EnergyPlus, to illustrate the energy performance of a generic commercial building with daylighting controls obstructed by neighbouring buildings of various heights. Analysis of electricity savings was carried out for the perimeter zones of the whole building and individual floors. Regression techniques were conducted to correlate the building energy savings and the angles of obstructions. It was found that the shading effects due to nearby obstructions strongly affect the building energy budget when daylighting designs are used. Building designers should critically consider the external environment in order to achieve energy-efficient building designs.     

Analysis of energy conservation standards for Singapore office buildings

The authors have evaluated existing energy conservation standards for office buildings in Singapore and recommend changes in the present lighting and OTTV (overall thermal transfer value) standards. The analysis shows that significant energy savings can be effected by the use of daylighting and several other measures that reduce cooling loads. It was found that some other measures (e.g. ceiling and wall insulation and double-glazed windows) have little impact on energy use.     

Evaluating and ranking energy performance of office buildings using Grey relational analysis

Traditional methods of evaluating energy performance of building tend to focus on comparing the observed energy consumption with the average value of energy consumption by regression method or theoretical value calculated by simulation analysis. For evaluating and ranking the energy performance of buildings, this paper proposed a perspective of multiple objective outputs to evaluate the energy performance of buildings and then use a multiple attribute decision-making approach, Grey relational analysis (GRA), to rank the evaluated buildings. The energy performance of 47 office buildings in Taiwan were evaluated and ranked to serve as a case study to illustrate the procedure and effectiveness of the proposed approach.     

Competing explanations for adopting energy innovations for new office buildings

An integrative model to explain potential adopters’ decisions to adopt energy innovations was adapted and applied in the field of new office building construction. We tested the relative effects of competing theoretical explanations (derived from economics, innovation science and policy science) on the decision to adopt. The research covered 35 projects representing 9% of the total volume of new office construction in the Netherlands between 2000 and mid-2002. Two levels of explanations for adopting innovations were derived: (a) the potential adopter's weighed assessments of the innovations and his or her nature of decision making and (b) explanation of those first-level variables. Using multiple regression techniques, we determined the relative influence on innovation-adoption of variables covering economy and technology, government intervention, company characteristics, and influences from market and society. The decision to adopt ‘mature’ innovations, in contrast to ‘young’ innovations, is based more on routine procedures than project-specific considerations. Policies need to take this difference into consideration. We also show evidence that in promoting adoption of E-innovations for new office buildings the Dutch system of applying Energy Performance Standards and subsidies proofs to be effective.     

Energy consumption,energy savings,and emission analysis in Malaysian office buildings

This paper is concerned with the estimation of energy use in office buildings in Malaysia and with the energy use of major equipment. Energy intensity (EI) – a measure of a building's energy performance – is estimated for Malaysia and compared with a number of selected countries. Air conditioners are shown to be the major energy users (57%) in office buildings, followed by lighting (19%), lifts and pumps (18%) and other equipment (6%). It is estimated that 77,569 MWh of energy can be saved and a huge reduction of emissions achieved through the application of advance glazing, compact fluorescent lamps (CFL), insulation, housekeeping, and by raising thermostat set point temperature of air conditioners, and reducing EI.     

A generalized window energy rating system for typical office buildings

Detailed computer simulation programs require lengthy inputs, and cannot directly provide an insight to relationship between the window energy performance and the key window design parameters. Hence, several window energy rating systems (WERS) for residential houses and small buildings have been developed in different countries. Many studies showed that utilization of daylight through elaborate design and operation of windows leads to significant energy savings in both cooling and lighting in office buildings. However, the current WERSs do not consider daylighting effect, while most of daylighting analyses do not take into account the influence of convective and infiltration heat gains. Therefore, a generalized WERS for typical office buildings has been presented, which takes all primary influence factors into account. The model includes embodied and operation energy uses and savings by a window to fully reflect interactions among the influence parameters. Reference locations selected for artificial lighting and glare control in the current common simulation practice may cause uncompromised conflicts, which could result in over- or under-estimated energy performance. Widely used computer programs, DOE2 and ADELINE, for hourly daylighting and cooling simulations have their own weaknesses, which may result in unrealistic or inaccurate results. An approach is also presented for taking the advantages of the both programs and avoiding their weaknesses. The model and approach have been applied to a typical office building of Hong Kong as an example to demonstrate how a WERS in a particular location can be established and how well the model can work. The energy effect of window properties, window-to-wall ratio (WWR), building orientation and lighting control strategies have been analyzed, and can be indicated by the localized WERS. An application example also demonstrates that the algebraic WERS derived from simulation results can be easily used for the optimal design of windows in buildings similar to the typical buildings.     

Implementing effect of energy efficiency supervision system for government office buildings and large-scale public buildings in China

The Chinese central government released a document to initiate a task of energy efficiency supervision system construction for government office buildings and large-scale public buildings in 2007, which marks the overall start of existing buildings energy efficiency management in China with the government office buildings and large-scale public buildings as a breakthrough. This paper focused on the implementing effect in the demonstration region all over China for less than one year, firstly introduced the target and path of energy efficiency supervision system, then described the achievements and problems during the implementing process in the first demonstration provinces and cities. A certain data from the energy efficiency public notice in some typical demonstration provinces and cities were analyzed statistically. It can be concluded that different functional buildings have different energy consumption and the average energy consumption of large-scale public buildings is too high in China compared with the common public buildings and residential buildings. The obstacles need to be overcome afterward were summarized and the prospects for the future work were also put forward in the end.     

An analysis of daylighting and solar heat for cooling-dominated office buildings

Computer simulation techniques were used to assess the energy performance of a generic commercial office building in Hong Kong. The simulation tool was DOE-2.1E. The thermal and energy performance of daylighting schemes were analysed in terms of the reduction in electric lighting requirement and the cooling penalty due to solar heat. Regression analysis was conducted to correlate the peak electricity demand and annual incremental electricity use with two fenestration variables, namely the solar aperture and the daylighting aperture. Contours of equal annual incremental electricity use were shown to be a function of the solar and daylighting apertures. It is envisaged that these simple charts can be a useful design tool for architects and engineers to assess the relative energy performance of different fenestration designs, particularly during the initial design stage when different building design schemes and concepts are being considered and developed.     

Effectiveness of single and multiple energy retrofit measures on the energy consumption of office buildings

Energy retrofit measures (ERMs) are applied to reduce the energy consumption of buildings. The effectiveness of any ERM depends on many building specific factors, such as location, size, operation, building envelope, electrical, heating, cooling and ventilation system properties. It is common for multiple ERMs to be applied to a building to reduce its energy consumption. However, the reduction in energy consumption when multiple ERMs are applied is not the sum of the impact of individual ERMs. Effectiveness of multiple ERMs depends upon their interactive effects. Using representative office buildings and an energy modelling computer program, the effectiveness of individual and multiple ERM was assessed providing a better understanding of their interactive effects.     

Energy and cost analysis of semi-transparent photovoltaic in office buildings

Solar energy conversion systems and daylighting schemes are important building energy strategies to produce clean energy, reduce the peak electrical and cooling demands and save the building electricity expenditures. A semi-transparent photovoltaic (PV) is a building component generating electricity via PV modules and allowing daylight entering into the interior spaces to facilitate daylighting designs. This paper studies the thermal and visual properties, energy performance and financial issue of such solar facades. Data measurements including solar irradiance, daylight illuminance and output power for a semi-transparent PV panel were undertaken. Using the recorded results, essential parameters pertaining to the power generation, thermal and optical characteristics of the PV system were determined. Case studies based on a generic reference office building were conducted to elaborate the energy and cooling requirements, and the cost implications when the PV facades together with the daylight-linked lighting controls were being used. The findings showed that such an integrated system could produce electricity and cut down electric lighting and cooling energy requirements to benefit the environmental, energy and economic aspects.     

Daylighting and energy analysis of private offices with automated interior roller shades

This paper presents a comprehensive analysis to study the balance between daylighting benefits and energy requirements (control of solar gains) in perimeter private office spaces with interior roller shades taking into account glazing properties, shading properties and control together with window size, climate and orientation in an integrated daylighting and thermal manner. Daylight autonomy and useful daylight illuminances were computed as a function of façade design parameters. A thermal simulation module using the explicit finite difference thermal network approach runs at the same time step and calculates heating, cooling and lighting source energy consumption as well as surface temperatures and operative temperature. Based on the daylighting results, lighting internal gains (continuous dimming control) are simultaneously input to the thermal module. The model also considers the air in the gap between shade and interior glass as a separate thermal node.Detailed results for Chicago and Los Angeles showed that windows with visible transmittance higher than 50% have the ability to allow enough daylight into the space for all locations and orientations for window-to-wall ratios higher than 50%. Useful daylight illuminances between 500 and 1000 lux were considered in detail – it was found that this index can be maximized for specific window-to-wall ratios and that depends on the glazing properties and fabric properties for each orientation. Moreover, the complex interactions of the studied parameters and their impact on the heating, cooling and lighting energy performance revealed an interesting result: windows occupying 30–50% of the façade can actually result in lower total energy consumption for most cases with automated shading. This illustration of daylighting benefits can be realized only if the integration of daylighting and thermal climate-based analysis is modeled efficiently and depends on glazing and shading properties and control. Finally, best designs for each orientation and location were pointed out based on both daylighting and thermal results.     

Implementation conditions for energy saving technologies and practices in office buildings: Part 1. Lighting

This paper provides a review of lighting energy saving and energy efficiency policies and practices in office buildings. The results of a face to face survey of 685 managers of companies are presented, which give insights into the factors that have influenced them to invest in lighting saving technologies. The assessment of the available lighting technologies in use in office buildings, showed that the installation of lighting saving technologies was positively influenced by a number of parameters, such as high annual financial turnover, recently established companies and companies managed by older, highly educated and energy aware people. The acceptability of the adoption and use of new efficient lighting technologies and the willingness to pay for proposed new efficient office lighting technologies, following a technico-economic information session, were also investigated. The willingness of a manager to invest in lighting energy saving/efficient technology was positively influenced by a number of factors including when a company was located in old buildings, if it was companies affected by electricity shortages, and/or if it had a large floor area.     

Comparison and analysis of energy consumption of energy-efficient office buildings in different climate regions in China: case studies

The purpose of this paper is to analyze the energy consumption (EC) and find out the determining factors of energy-efficient office building cases according to specific case studies in typical cities of different climate zones in China. The investigated building cases were located in four cities (Beijing, Ningbo, Nanjing and Shenzhen) of three architecture thermotechnical design zones (cold zone, hot summer and cold winter zone, hot summer and warm winter zone). The analysis indicates that the energy consumption index (ECI) of these four cases ranges from 41.06 to 74.23 kW·h/(m²·a). Besides, the outdoor climate can change the EC of air conditioning/heating systems, and further determine the monthly volatility of the total EC of the whole building.     

蓄冰空调系统在办公类建筑中的经济性分析

针对蓄冰空调系统的工程应用,阐述系统工作原理及其适用性分析,选取河北省某办公建筑作为研究对象,按照此建筑用能特点以及当地电价结构,选择了100%、80%、60%、40%、20%五档部分负荷率对蓄冰空调系统与传统空调系统进行全年运行能耗及电费对比,分析结果表明:虽然蓄冰空调系统初投资偏高,但其年运行费用比传统空调系统节省电费32.4%,寿命期内年费用节省20.43%。     

托管型合同能源管理模式在高校建筑节能减排中的研究

以江苏科技大学东校区某综合楼为研究背景,对其进行合同能源管理模式实践的可行性分析,并确定实施内容和实施步骤。研究方案包括节能项目评估、节能改造方案设计、计算节能效益。研究结果表明能源费用托管型合同能源管理模式在高校建筑节能中具有重大的推广与实施意义。     

Asset and operational benchmarking for office buildings in Greece

The aim of this paper is to compare the asset and operational rating of buildings by the creation of a thermal model in TRNSYS 16 in order to simulate the thermal behaviour of a multi-storey (seven floors) office building that belongs to BYTE Computer S.A. located in Athens, Greece. Then based on the validated building model, the generalisation of this method is investigated for the creation of a virtual database for office building energy benchmarking in Greece. The data collected for the case-study building are based on engineering plans and studies, on in-situ measurements and mainly on the building management system (BMS) already implemented in the building. The building is modelled in detail by splitting it into 45 thermal zones. The simulation results are compared with the measured values provided by the BMS for two periods (winter and summer). The processing of the results leads to conclusions regarding the reliability of the model, the accuracy of asset rating compared to operational rating, as well as its usefulness in evaluating building retrofitting scenarios and its application as a general energy audit model for office buildings in Greece.