Energy savings of office buildings by the use of semi-transparent solar cells for windows

The study investigated a PV window that consists of a double glazed window with semi-transparent solar cells. The window provides natural light transmission as well as electricity production. The effect of the PV window on energy consumption of office buildings was analyzed in terms of heating and cooling loads, daylighting, and electricity production. The purposes of the study were to find the optimum solar cell transmittance and window to wall ratio (WWR), and to estimate energy savings of the building. A standard floor of an office building was modeled to run computer simulation, and annual energy simulation was performed with EnergyPlus. The results showed that the solar cell transmittance of 40% and WWR of 50% achieved the minimum electricity consumption in the building when artificial lighting was controlled with daylighting. The optimum solar cell transmittance for PV windows in different orientation was also presented. By using the optimum PV window, the electricity consumption was reduced by 55% compared to the single glazed window with WWR of 30% and no lighting control.     

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.     

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%.     

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.     

Energy efficient office buildings with passive cooling – Results and experiences from a research and demonstration programme

To gain access to information on energy use in office buildings, the German Federal Ministry for Economy launched an intensive research and demonstration programme in 1995. In advance of the 2002 EU energy performance directive a limited primary energy coefficient of about 100 kW h m⁻² a⁻¹ as a goal for the complete building services technology was postulated (HVAC + lighting) for all demonstration buildings to be supported. A further condition was that active cooling be avoided. Techniques such as natural or mechanical night ventilation or heat removal by slab cooling with vertical ground pipes as well as earth-to-air heat exchangers in the ventilation system were applied. An accompanying research was established to keep track of the results and the lessons learned from about 22 demonstration buildings realized and monitored until the end of 2005. As one outcome this paper summarises the energy performance of a selection of characteristic buildings together with an overview on the summer thermal comfort situations achieved. The research program will proceed during the next five years. Detailed reports and future results may be downloaded from the internet: www.enbau-monitor.de.     

The role of corporate reputation and employees' values in the uptake of energy efficiency in office buildings

Although office market actors in the United Kingdom show a growing interest in energy efficiency, the pace of takeup of energy efficient office features is slow. Previous studies have highlighted the roles of limited direct financial costs and benefits (‘efficiency gaps’) and market barriers in limiting the rate of technology adoption. This study provides further evidence on the importance of these factors, but the primary contribution is focused on the role of corporate reputation and on the importance of individuals' values in shaping corporate behaviour. The paper presents a theoretical framework to explain environmental decision making in firms and we present qualitative evidence drawing from sixteen semi-structured individual and group interviews with office market stakeholders in London, Glasgow and Edinburgh. The research finds that companies, despite gradually becoming more energy conscious, still regard energy costs as a negligible part of their business costs. Nevertheless, an increasingly important driver is the reputational gain obtained by corporate businesses implementing sustainable practices. All the interviewees agreed that the pace of change in the office market is slow and that only further policy interventions will accelerate it.     

Energy performance of residential buildings in Singapore

Energy consumption of buildings takes up about a third of Singapore's total electricity production. In this paper, we present a pioneering study to investigate the energy performance of residential buildings. Beginning with an energy survey of households, we established the air-conditioning usage patterns and modelled residential buildings for computer simulations. An ETTV equation for residential buildings was developed. Employing this equation, we demonstrated how to achieve improved energy efficiency in residential buildings. Two types of residential buildings, namely, point block and slab block, were modelled and parametric runs performed. ETTV impacts the energy consumption of residential buildings and thus lowering the ETTV will result in reduced building heat load. Results from the developed equation showed that a unit decrease in ETTV resulted in 4% and 3.5% reduction in annual cooling energy for point block and slab block residential buildings, respectively. In addition, a set of simple energy and load estimating equations were developed using computer simulation and local climatic data. These equations provided a means of estimating the annual cooling energy consumption of residential buildings in Singapore.     

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.     

Economic analysis of the daylight-linked lighting control system in office buildings

The objective of this study is to perform an economic analysis of the daylight-linked automatic on/off lighting control system installed for the purpose of energy savings in office buildings. For this, a building was chosen as a typical example, and the energy cost was calculated by using the daylight and building energy analysis simulation. When the lighting control was utilized, an economic analysis was performed using a payback period that was calculated by comparing the initial cost of installing the lighting control system with the annual energy cost which was reduced thanks to the application of the lighting control.The results showed that the lighting energy consumption, when the lighting control was applied, was reduced by an average of 30.5% compared with the case that there was not lighting control applied. Also, the result for total energy consumption showed that, when lighting control was applied, this was reduced by 8.5% when the glazing ratio was 100%, 8.2% for 80%, and 7.6% for 60% when compared to non-application. The payback period was analyzed in terms of the number of floors in a building; 10 floors, 20 floors, 30 floors, and 40 floors. Hence, the building with 40 floors and glazing ratio 100% resulted in the shortest payback period of 8.8 years, the building with 10 floors and glazing ratio 60% resulted in the longest period of 12.7 years. In other words, the larger the glazing ratio and the number of building floors are, the shorter the payback period is.     

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.     

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.     

Quantifying the potential of automated dynamic solar shading in office buildings through integrated simulations of energy and daylight

The façade design is and should be considered a central issue in the design of energy-efficient buildings. That is why dynamic façade components are increasingly used to adapt to both internal and external impacts, and to cope with a reduction in energy consumption and an increase in occupant comfort. To gain a complete picture of any façade’s performance and subsequently carry out a reasonable benchmarking of various façade alternatives, the total energy consumption and indoor environment need to be considered simultaneously. We quantified the potential of dynamic solar shading façade components by using integrated simulations that took energy demand, the indoor air quality, the amount of daylight available, and visual comfort into consideration. Three types of façades were investigated (without solar shading, with fixed solar shading, and with dynamic solar shading), and we simulated them with various window heights and orientations. Their performance was evaluated on the basis of the building’s total energy demand, its energy demand for heating, cooling and lighting, and also its daylight factors. Simulation results comparing the three façade alternatives show potential for significant energy reduction, but greater differences and conflicting tendencies were revealed when the energy needed for heating, cooling and artificial lighting were considered separately. Moreover, the use of dynamic solar shading dramatically improved the amount of daylight available compared to fixed solar shading, which emphasises the need for dynamic and integrated simulations early in the design process to facilitate informed design decisions about the façade.     

Solar cooling system using concentrating collectors for office buildings: A case study for Greece

On a European level there is intense research activity to broaden the applications of solar thermal systems beyond their established domains (hot water, space heating support) and to foster their participation in the energy maps of the EU-Member States. Concentrated Solar Thermal (CST) systems are expected to play a key role in this effort, especially for achieving the medium and high temperatures needed, for electricity generation, for industrial applications but also for hybridized solar heating/cooling and desalination applications.This paper presents a proposal for implementation of a CST system in the building sector, based on a research carried out in the Laboratory of Environmental and Energy Efficient Design of Buildings and Settlements at the University of Thrace. Specifically, an integrated solar cooling system using parabolic trough solar collectors and double-effect chiller is discussed, used to cover the cooling needs of typical office building in Greece.As it was shown, the use of concentrating solar collectors leads to significantly higher output temperatures that can enable the use of two stage absorption chillers with a higher COP. Alternatively, when low or medium temperature heat is required, the use of CST systems takes less space to cope with it than traditional flat plate collectors. The combination of these parameters can contribute to removing key barriers associated with the broader diffusion of solar cooling technology, enhancing the potential to become more competitive to the conventional air conditioning technologies.     

用户侧多能互补发展的实践、问题及对策

梳理了我国在多能互补领域的相关政策,概述了地方政府积极探索的经验做法,通过典型工程案例分析了企业先行先试的实践,同时指出在用户侧多能互补发展领域尚存在标准体系未建立、部分关键技术未突破、项目资源开发受限、用户参与意愿不强、项目投资运行成本较高、项目经济性不佳、商业模式不成熟、综合能源服务水平低等问题和困难,并结合国内新一轮电力体制改革趋势,从用户侧多能互补项目投资机制选择、建设方案确定、运营机制创新、市场机制建设、产业政策完善等多个方面对今后如何进一步推进用户侧多能互补发展提出了建议。     

Analysis of variable-base heating and cooling degree-days for Turkey

The degree-day method is one of the well-known and the simplest methods used in the Heating, Ventilating and Air-Conditioning industry to estimate heating and cooling energy requirements. In this study, the heating and cooling degree-days for Turkey are determined by using long-term recent measured data. Five different base temperatures ranging from 14 to 22°C are chosen in the calculation of heating degree-days. In the case of cooling degree-days, 6 different base temperatures in the range 18 to 28°C are used. Yearly heating and cooling degree-days are given both in tabular form and as counter maps for all the provinces of Turkey (78 weather stations).     

Benchmarking the energy performance for cooling purposes in buildings using a novel index-total performance of energy for cooling purposes

Benchmarking the energy performance for cooling purposes in buildings is an important tool for energy management. This paper proposes a novel index and develops a benchmarking process for energy performance for cooling purposes by means of data envelopment analysis and cooling degree hour method. The research begins by using climate data to calculate cooling degree hour and proceeds to build an index of total performance of energy for cooling purposes by linear regression method. Finally, data envelopment analysis is adopted to benchmark the energy performance for cooling purposes in buildings with the index of total performance of energy for cooling that has the effect of ventilation factors (floor area and number of occupants) removed. An application to office buildings in Taiwan is presented to illustrate the development and the use of the evaluating method.     

A new approach for predicting cooling degree-hours and energy requirements in buildings

This study develops a novel approach to predict the outdoor temperature fluctuations during daytime as a dimensionless temperature variation coefficient. In this approach, the daily outdoor temperature trend is established by using the daily maximum and minimum temperatures. A case study is performed to calculate the cooling degree-hours for 58 cities in different geographical regions of Turkey as a case study for the present approach. The results are then compared with the published data. The other advantage of this approach is that it allows the prediction of monthly cooling degree-hours for buildings.     

Guidelines for improving natural daytime ventilation in an office building with a double-skin facade

In recent years, there has been a great deal of interest in double-skin facades due to the advantages claimed for this technology in terms of energy saving in the cold season, protection from external noise and wind loads and their high-tech image.The advent of computers and other office equipment has increased the internal heat gains in most offices. Highly glazed facades, together with the extra heat gains from the electric lighting made necessary by deep floor plans and the wider use of false ceilings, have increased the risk of overheating. To preserve comfort and reduce cooling loads, it is important to apply natural cooling strategies, including natural ventilation.Some argue that double-skin facades are designed to improve natural ventilation in buildings by the stack effect, and to allow this even in situation in which it is generally not possible due to high outdoor noise levels and/or high wind speeds.But poor operation of the double-skin facade openings can generate disastrous scenarios such as the injection of hot air from the double-skin facade into the offices and the contamination of offices on the upper floors by used air from the offices on the lower floors.This article examines how natural ventilation can be utilised in an office building with a double-skin facade during a sunny summer’s day. It mainly considers natural daytime ventilation in relation to the orientation of the double skin and the speed and direction of the wind.     

Energy consumption in typical Caribbean office buildings: A potential short term solution to energy concerns

This paper examines the feasibility of energy efficiency as a short term solution to the Caribbean’s energy problems. It considers energy consumption across selected office buildings in Barbados, typical of Caribbean architecture. By comparing their energy consumption to that of the energy consumption for the building with the “best observable” consumption in the selected group, the energy efficiency is determined. Data for five (5) buildings with similar characteristics were collected, analyzed and normalized to facilitate a direct comparison between them. The selected indicator was Energy Consumption per Unit Area (I_E = E/A).On examining the equipment and technology (E&T) currently being used in these buildings a definite inefficiency resulting from this was identified. The undetermined inefficiency was allocated to management and operations (M&O).The “best observable” building had an E&T inefficiency of 10%. Results suggest that E&T is responsible for between 10% and 14% additional energy wastage while the inefficiency due to business processes is believed to be largely responsible for inefficiency beyond 14%. Overall inefficiency rose as high as 56%, indicating an opportunity for significant energy savings through an efficiency response.Electrical energy consumed in a building is shown to be not only related to physical space and E&T inefficiency, but also to an x-efficiency factor that is peculiar to the management and operations of that building.     

Development of a new energy efficiency rating system for existing residential buildings

Building energy efficiency rating systems have been established worldwide to systematically manage the energy consumption of existing buildings. This study aimed to develop a new energy efficiency rating system for existing residential buildings from two perspectives: (i) establishment of reasonable and fair criteria for the building energy efficiency rating system; and (ii) establishment of comparative incentive and penalty programs to encourage the voluntary participation of all residents in the energy saving campaign. Based on the analysis of the conventional energy efficiency rating system for existing residential buildings, this study was conducted in five steps: (i) data collection and analysis; (ii) correlation analysis between the household size and the CO₂ emission density (i.e., CO₂ emission per unit area); (iii) cluster formation based on results of the correlation analysis using a decision tree; (iv) establishment of a new energy efficiency rating system for existing buildings; and (v) establishment of incentive and penalty programs using advanced case-based reasoning. The proposed system can allow a policymaker to establish a reasonable and fair energy efficiency rating system for existing residential buildings and can encourage the voluntary participation of all residents in the energy saving campaign.