Energy and exergy analysis of the Greek hotel sector: An application

Energy consumption in buildings vary significantly, depending on factors as the use of the building, the construction type, maintenance, existing heating, cooling and lighting systems and other types of services. Hotel buildings have high energy consumption rate, as a result of their unique operational characteristics. Energy consumption in hotels is among the highest in the non-residential building sector in absolute values. Available specific information on the energy characteristics, thermal performance, energy losses, electric loads, and comfort conditions play significant role for the sustainable development of hotel's systems. These data can also be used to identify whether there is space for improvement in new or existing hotels by comparing them against predicted or actual building energy performance. The aim of the present paper is to analyze the energy and exergy utilization in four hotels in Rethimno, Crete (Southern Greece) and in Kassandra, Halkidiki (Northern Greece).     

Performance evaluation of operational energy use in refurbishment,reuse, and conservation of heritage buildings for optimum sustainability

The operational phase of a building project has increasingly gained importance with their energy performance becoming valuable and determining their operational excellence. In most heritage building projects (HBPs), the operational energy use aspects areless considered, and a systematic way of analyzing their energy performance following project delivery is often lacking. The aim of this study is to evaluate the operational performance of refurbishment and reuse of UK listed church projects. The objective is to assess the operational energyuse with a view to optimizing their sustainable performance. The methodology includes eight selected case study buildings refurbished and converted for multipurpose use. The case study approach provided qualitative insights into how the study contributes to a more structured requirements for energy management in HBPs with specific attention to energy-efficient building operations. The findings show the need to focus on fundamental areas of operational management (i.e.by developing and implementing more focused policy on operational energy performance of heritage buildings) to minimize the energy required to operate them. The challenges of implementing changes in operational energy performance improvement of heritage buildings are addressed in the form of recommendations that could lead to real results. The study concludes that leveraging these areas requires commitment from all heritage building stakeholders because they all have substantial roles in harmonizing the requirement for the project's sustainability and not just the building operators. Meanwhile, baseline project planning, periodic updating, monitoring, and managing the energy use pattern are suggested as measures that could greatly facilitate better energy performance to optimizing their sustainable reuse compared with the traditional approach of trying to improve their thermal performance.     

大型公共建筑运行能耗数据库管理系统初步开发及应用

能耗测试是既有建筑节能改造过程的必要途径,为了对测试数据进行科学有效地管理,作者初步开发了大型公共建筑运行能耗数据库管理系统,并将其应用于若干实际建筑中。本文介绍了该数据库管理系统开发过程,并对其应用结果进行了分析,说明该系统切实可行并发现在建筑耗能系统中存在若干运行问题。     

A case study for the evaluation of realistic energy retrofit strategies for public office buildings in the Southern Hemisphere

The building sector offers significant opportunities for reducing the energy consumption with considerable economic, environmental and health benefits. Governments can lead the way by retrofitting existing public buildings to reinforce their commitment to improve energy efficiency. Similar design standards, end-uses and operational profiles are usually established for public buildings based on the services they offer. Retrofitting a public building can therefore serve as an ideal test-bed for energy efficiency measures for other buildings within a particular service category. This study first analysed the current electricity consumption of a public office building in Mauritius, located in the Southern Hemisphere. A complete model of the building was created, validated and then simulated to investigate the impact of realistic retrofit strategies on the electricity consumption. Results showed that lighting retrofit achieved the most significant reduction while measures that improved the thermal envelope of the building resulted in smaller energy savings. The possibility of exploiting solar energy was explored by simulating a 70 kW_p photovoltaic system installed on the roof. An equivalent of 8.5% of the annual electricity consumption of the building could thus be generated. A financial analysis is also presented for all retrofit scenarios in terms of annual return and payback period.     

Measured energy savings from residential retrofits: Updated results from the BECA-B project

This study summarizes measured data on energy savings from conservation retrofits in existing residential buildings. We have compiled building performance data on approximately 115 retrofit projects (almost twice the size of the initial study) that we put into four general categories: utility-sponsored conservation programs, low-income weatherization programs, research studies, and multifamily buildings. The sample size for each project varies widely, ranging from individual buildings to 33 000 homes. Retrofits to the building shell, principally insulation of exterior surfaces, window treatments, and infiltration-reduction measures, are the most popular, although data on various heating system retrofits are now available. The average retrofit investment per unit in multifamily buildings is approximately $695, far lower than the average of $1350 spent in single-family residences. The median annual space heat savings in the four categories range from 15 to 38 GJ. Savings achieved are typically 20%–30% of pre-retrofit space heating energy use although large variations are observed both in energy savings and in costs per unit of energy saved. Even given the wide range in savings, most retrofit projects are cost-effective. Approximately 75%–80% of the retrofit projects have costs of conserved energy below their respective space heating fuel or electricity prices.     

Building typologies as a tool for assessing the energy performance of residential buildings - A case study for the Hellenic building stock

Successful strategies towards minimizing the energy consumption and greenhouse gas emissions attributed to the building sector require knowledge on the energy-related characteristics of the existing building stock. Despite the numerous studies on energy conservation applications in buildings, current knowledge on the energy-related characteristics of the building stock still remains limited. Building typologies can be a useful instrument to facilitate the energy performance assessment of a building stock. This work is based on a harmonised structure for European building typologies (TABULA) developed for residential buildings, but the methodology may be extended to the tertiary sector as well. National typologies are sets of model buildings with characteristic energy-related properties representative of a country's building stock. The model buildings are used as a showcase for demonstrating the energy performance and the potential energy savings from typical and advanced energy conservation measures (ECMs) on the thermal envelope and the heat supply system. The proposed Hellenic residential building typology is presented for the first time along with an assessment of various ECMs that are used for an estimate of the energy performance of building stock in Greece in an effort to meet the 9% indicative national energy savings target by 2016.     

Energy performance assessment of existing dwellings

The existing buildings stock in European countries accounts for over 40% of final energy consumption in the European Union (EU) member states, of which residential use represents 63% of total energy consumption in the buildings sector. Consequently, an increase of building energy performance can constitute an important instrument in the efforts to alleviate the EU energy import dependency and comply with the Kyoto Protocol to reduce carbon dioxide emissions. This is also in accordance to the European Directive on the energy performance of buildings (EPBD), which has come to effect on 4 January 2006. The energy performance assessment for existing dwellings (EPA-ED) is a new methodology supported by software, developed in the framework of a European project that focuses on energy related issues for existing residential buildings, in line with the EPBD. This paper presents an overview of the method and software that can be used to perform building energy audits and assess buildings in a uniform way, perform demand and savings calculations, provide owners with specific advice for measures to improve energy performance, issue an energy performance certificate for existing buildings, and include some representative results from the pilot studies performed in several European countries. Also the sister-method EPA-NR, on non-residential buildings, currently under construction, is introduced.     

Development of building thermal environment emulator to evaluate the performance of the HVAC system operation

A “performance gap” arises when the actual value of building energy consumption during the operational phase deviates from the value predicted using simulation during the design phase. One cause of this performance gap is that operation is not ideal, as assumed in the simulation, and the control of the heating, ventilating, and air conditioning (HVAC) system is not optimized. These problems occur because the operator has not been trained sufficiently and/or the building automation system is not working as intended by the developer. Both problems are fundamentally caused by the fact that the quality of building operation cannot be quantitatively evaluated by comparison with other buildings because a building is a heterogenous, single-item product. To address the performance gap problem, we developed a method for quantitatively evaluating building operation using a precise simulation based on a thermal environment emulator. The emulator software was developed using the BACnet protocol as an interface to the real world and includes an occupant behavior model to enable the assessment of operation in terms of thermal comfort as well as energy performance. In this paper, we report on the program and network structure of the proposed emulator. In addition, we show the concrete results of changing the operational control, and we assess changes in energy performance and comfort from the perspective of Pareto efficiency.     

Life cycle primary energy analysis of residential buildings

The space heating demand of residential buildings can be decreased by improved insulation, reduced air leakage and by heat recovery from ventilation air. However, these measures result in an increased use of materials. As the energy for building operation decreases, the relative importance of the energy used in the production phase increases and influences optimization aimed at minimizing the life cycle energy use. The life cycle primary energy use of buildings also depends on the energy supply systems. In this work we analyse primary energy use and CO₂ emission for the production and operation of conventional and low-energy residential buildings. Different types of energy supply systems are included in the analysis. We show that for a conventional and a low-energy building the primary energy use for production can be up to 45% and 60%, respectively, of the total, depending on the energy supply system, and with larger variations for conventional buildings. The primary energy used and the CO₂ emission resulting from production are lower for wood-framed constructions than for concrete-framed constructions. The primary energy use and the CO₂ emission depend strongly on the energy supply, for both conventional and low-energy buildings. For example, a single-family house from the 1970s heated with biomass-based district heating with cogeneration has 70% lower operational primary energy use than if heated with fuel-based electricity. The specific primary energy use with district heating was 40% lower than that of an electrically heated passive row house.     

Do LEED-certified buildings save energy? Yes, but…

We conducted a re-analysis of data supplied by the New Buildings Institute and the US Green Buildings Council on measured energy use data from 100 LEED-certified commercial and institutional buildings. These data were compared to the energy use of the general US commercial building stock. We also examined energy use by LEED certification level, and by energy-related credits achieved in the certification process. On average, LEED buildings used 18-39% less energy per floor area than their conventional counterparts. However, 28-35% of LEED buildings used more energy than their conventional counterparts. Further, the measured energy performance of LEED buildings had little correlation with certification level of the building, or the number of energy credits achieved by the building at design time. Therefore, at a societal level, green buildings can contribute substantial energy savings, but further work needs to be done to define green building rating schemes to ensure more consistent success at the individual building level. Note, these findings should be considered as preliminary, and the analyses should be repeated when longer data histories from a larger sample of green buildings are available.     

The use of normative energy calculation beyond building performance rating

Standardized building performance assessment is best expressed with a so-called normative calculation method, such as defined in the Committee for Standardization/International Organization for Standardization (CEN/ISO) calculation standards. The normative calculation method has advantages of simplicity, transparency, robustness and reproducibility. For systematic energy performance assessment at various scales, i.e. at the unit of analysis of one building up to a large-scale collection of buildings, the authors' group developed the Energy Performance Standard Calculation Toolkit (EPSCT). This toolkit calculates objective indicators of energy performance using either the monthly or hourly calculation method as specified in the CEN/ISO standard for building energy calculation. The toolkit is the foundation for numerous single, medium-scale and large-scale building energy management applications. At the largest level, applications should be able to manage hundreds or thousands of buildings. The paper introduces two novel applications that have the normative calculation at their core: (1) network energy performance modelling and (2) agent-based building stock energy modelling.     

A comprehensive life cycle water analysis framework for residential buildings

Most studies on the environmental performance of buildings focus on energy demand and associated greenhouse gas emissions. They often neglect to consider the range of other resource demands and environmental impacts associated with buildings, including water. Studies that assess water use in buildings typically consider only operational water, which excludes the embodied water in building materials or the water associated with the mobility of building occupants. A new framework is presented that quantifies water requirements at the building scale (i.e. the embodied and operational water of the building as well as its maintenance and refurbishment) and at the city scale (i.e. the embodied water of nearby infrastructures such as roads, gas distribution and others) and the transport-related indirect water use of building occupants. A case study house located in Melbourne, Australia, is analysed using the new framework. The results show that each of the embodied, operational and transport requirements is nearly equally important. By integrating these three water requirements, the developed framework provides architects, building designers, planners and decision-makers with a powerful means to understand and effectively reduce the overall water use and associated environmental impacts of residential buildings.     

Assessing dynamic efficiency of air curtain in reducing whole building annual energy usage

The efficiency of air curtain in reducing infiltration and associated energy usage is currently evaluated statically by using an efficiency factor, η _air, based on single steady/static condition, which is often not the case for actual buildings under variable weather conditions and door usages. Based on a new method to consider these dynamic effects on air curtains, this study uses a dynamic efficiency factor η _B in terms of whole building site end-use energy to assess the efficiency of air curtains when compared to single doors (i.e. without air curtains) and vestibule doors. Annual energy simulations were conducted for two reference building models considering their specific door usage schedules in 16 climate zone locations in the North America. The variations of the proposed efficiency factor for different climate zones illustrated the dynamic impacts of weather, building, unit fan energy and door usage frequency on air curtain efficiency. A sensitivity study was also conducted for the operation temperature conditions of air curtain and showed that η _B also considers these operational conditions. It was thus concluded that using whole building site end-use energy to calculate the efficiency factor, ηB, can provide more realistic estimates of the performance of air curtains operations in buildings than the existing static efficiency factor.     

Virtual Building Dataset for energy and indoor thermal comfort benchmarking of office buildings in Greece

The knowledge of building stock energy data of a country is a very significant tool for energy benchmarks establishment, energy rating procedures and building classification boundaries determination, according to the Directive 2002/91/EC and its implementation in EU Member States. The lack of building energy databases in many EU Countries, including Greece, and the difficulties of collecting them lead to the investigation of other potential solutions. The aim of this paper is to present a method of a Virtual Building Dataset (VBD) creation for office buildings in Greece. The philosophy of VBD is based on the creation and simulation of random office buildings that could be found or built in Greece, taking into account the Greek constructional and operational characteristics of office buildings and Greek legislation. The VBD consists of 30,000 buildings (10,000 in each climatic zone) with their detailed constructional and operational data and of their simulation outputs: the annual specific energy consumption for heating, cooling, artificial lighting, office equipment and an indoor thermal comfort indicator. Based on VBD results the energy and indoor thermal comfort benchmarks for office building sector in Greece are assessed and presented.     

Building energy performance: sphere area as a fair normalization concept

ABSTRACT

Residential building energy performance indicators are compared with a different approach for the normalization of the characteristic yearly primary energy use. The purpose is to analyse which approach results in a fair assessment of more compact, energy-efficient building geometries, and of smaller building size. A normalization by floor area is shown to result in a poorer energy performance rating for smaller buildings. The notional building approach, as recently introduced in various countries, does not lead to a fair assessment of efficient geometries. Furthermore, the choice of reference characteristics to calculate the energy performance rating has a different impact on buildings with different characteristics. An average building approach is introduced as an improvement of the notional building approach. Form-efficient buildings are found to achieve a lower energy performance rating, but the choice of the reference characteristics is still present to a limited extent. As a second alternative, it is proposed to normalize the energy use by the sphere-area approach: the area of a sphere with the same volume as the rated building. This method leads to a fair assessment of form-efficient buildings and creates an incentive for more efficient building geometries and typologies.     

Simulation and visualization of energy-related occupant behavior in office buildings

In current building performance simulation programs, occupant presence and interactions with building systems are over-simplified and less indicative of real world scenarios, contributing to the discrepancies between simulated and actual energy use in buildings. Simulation results are normally presented using various types of charts. However, using those charts, it is difficult to visualize and communicate the importance of occupants’ behavior to building energy performance. This study introduced a new approach to simulating and visualizing energy-related occupant behavior in office buildings. First, the Occupancy Simulator was used to simulate the occupant presence and movement and generate occupant schedules for each space as well as for each occupant. Then an occupant behavior functional mockup unit (obFMU) was used to model occupant behavior and analyze their impact on building energy use through co-simulation with EnergyPlus. Finally, an agent-based model built upon AnyLogic was applied to visualize the simulation results of the occupant movement and interactions with building systems, as well as the related energy performance. A case study using a small office building in Miami, FL was presented to demonstrate the process and application of the Occupancy Simulator, the obFMU and EnergyPlus, and the AnyLogic module in simulation and visualization of energy-related occupant behaviors in office buildings. The presented approach provides a new detailed and visual way for policy makers, architects, engineers and building operators to better understand occupant energy behavior and their impact on energy use in buildings, which can improve the design and operation of low energy buildings.     

An object-oriented energy benchmark for the evaluation of the office building stock

Energy benchmarking is useful for understanding and enhancing building performance. The aim of this research is to develop an object-oriented energy benchmarking method for the evaluation of energy performance in buildings. Statistical analysis of the four-year monitored energy consumption data for office buildings was conducted. The results show that the energy use intensity follows the lognormal distribution with the Shapiro–Wilk normality test. Based on the lognormal distribution, the energy rating system for office buildings has been established. An object-oriented energy use intensity quota determination model has been developed. This research provides practical tools that enable decision-makers to evaluate a building's energy performance and determine the energy benchmark.     

Mandating transparency about building energy performance in use

In 2002, the European Union Energy Performance of Buildings Directive (EPBD) was ratified. This paper uses the lens of one policy measure triggered by the EPBD – Display Energy Certificates (DECs) for non-domestic buildings – to describe the difficulties experienced in capitalizing on a policy intention to use transparency about actual energy performance to drive better energy management and focus energy efficiency investment on things that really work in practice. It reviews the history and precedents of UK Building Regulations and European building energy efficiency policies to identify what helped and hindered progress towards buildings that use less energy in operation; and compares and contrasts building energy certificates based on asset and operational ratings. It also looks at the development paths of operational rating schemes in the US and Australia. It identifies a tendency of regulators to focus on one part of the problem, the so-called ‘regulated loads'; an unhelpful split of government ownership of the topic between various ministries and agencies; a neglect of follow-through, enforcement and feedback; and a political rhetoric that favours an abdication of central government responsibilities to market forces. Based on this evidence, it identifies a number of lessons for improvements to future policy outcomes.     

Energy savings in Danish residential building stock

A large potential for energy savings exists in the Danish residential building stock due to the fact that 75% of the buildings were constructed before 1979 when the first important demands for energy performance of building were introduced. It is also a fact that many buildings in Denmark face comprehensive renovations in the coming years and in connection with this renovation process energy-saving measures can be implemented relatively inexpensive and cost effective. This opportunity should be used to insure the buildings in the future as far as energy consumption is concerned. This paper gives a short account of the technical energy-saving possibilities that are present in existing dwellings and presents a financial methodology used for assessing energy-saving measures. In order to estimate the total savings potential detailed calculations have been performed in a case with two typical buildings representing the residential building stock and based on these calculations an assessment of the energy-saving potential is performed. A profitable savings potential of energy used for space heating of about 80% is identified over 45 years (until 2050) within the residential building stock if the energy performances are upgraded when buildings are renovated.     

An assessment tool for the energy, economic and environmental evaluation of thermal insulation solutions

The paper discusses an assessment tool, used for the energy, economic and environmental evaluation of Thermal Insulation Solutions (TIS). The results of the assessment undertaken with this tool can take the form of a simple rating system in order to enable users to perform comprehensive comparisons amongst various building materials and TIS. A ranking expressed by A, B and C classes is used for energy, environmental and economic parameters. By evaluating the materials, the tool supports the users to make decisions, depending on preferences or priorities such as the energy efficiency achieved, the total cost and the environmental performance. The assessment tool is applied for the double cavity wall and the External Thermal Insulation Composite Systems (ETICS) as they are used throughout Europe, both in new constructions and in the renovation of existing buildings.