The impact of auxiliary energy on the efficiency of the heating and cooling system: Monitoring of low-energy buildings

This paper presents a detailed meta-analysis of end and primary energy use for heating, cooling and ventilation of 11 low-energy non-residential buildings and one residential building in Germany that belong to the EnOB research program launched by the German Federal Ministry for Economy. In particular, the analysis emphasizes the substantial impact of auxiliary energy use on the efficiency of heating and cooling performance. The investigated buildings employ environmental energy sources and sinks - such as the ground, ground water, rainwater and the ambient air - in combination with thermo-active building systems. These concepts are promising approaches for slashing the primary energy use of buildings without violating occupant thermal comfort. A limited primary energy use of about 100 kWh_prim/(m²_neta) as a target for the complete building service technology (HVAC and lighting) was postulated for all buildings presented. With respect to this premise, a comprehensive long-term monitoring in high time resolution was carried out over the course of two to five years, with an accompanying commissioning of the building performance. Measurements include the energy use for heating, cooling, and ventilation, as well as the auxiliary equipment, the performance of the environmental heat source and sink, and local climatic site conditions.     

我国建筑耗能状况及有效的节能途径

简要分析了我国建筑能源消耗状况,从用能特点出发,对建筑物和建筑用能途径进行了新的分类,给出各类的现状、问题和节能潜力。在此基础上列出为实现建筑节能所需要的主要技术与产品研究领域和政策研究与保障机制。文中列出的关键技术研究为：基于模拟分析的建筑节能优化设计;新型建筑围护结构材料与部品;通风装置与排风热回收装置;热泵技术;降低输配系统能源消耗的技术;集中空调的温度湿度独立控制技术;建筑自动化系统的节能优化控制;楼宇式燃气驱动的热电冷三联供技术;燃煤燃气联合供热和末端调峰技术;节能灯、节能灯具与控制。有关政策与保障机制的研究问题为：建筑能耗数据的统计系统;住宅能耗标识方法与保障机制;大型公共建筑能耗评估与用能配额制;各种建筑用能装置的能耗标识标准与方法。     

公共类居住建筑采暖节能设计探讨

结合《民用建筑节能设计标准(采暖居住建筑部分)》(JGJ26-95)与《公共建筑节能设计标准》(GB50189-2005)两部设计标准的部分条文,探讨集体宿舍、招待所、旅馆、托幼等类型的公共类居住建筑的节能设计。指出了两部标准在适用范围、窗墙比、传热系数、采暖制式等多方面的规定有所不同,结合实际工程分析了该类建筑热工设计执行哪部标准更为合适。并对该类建筑在供暖方式、采暖制式、散热器采用等方面谈了个人设计体会。     

Impact of lifestyle on the energy demand of a single family house

The building sector is one of the highest energy consumers in Austria. The potential to save energy in existing buildings is very high. Current Austrian policy incentives encourage home owners to renovate buildings to meet the European requirements, reduce energy consumption, and reduce CO₂ emissions. Nevertheless, there are often discrepancies between the measured and calculated energy consumption results despite efforts to take parameters into account such as the exact geometry and thermal properties of the building, energy demand for hot water, heating, cooling, ventilation systems, and lighting in the planning phase for selecting the best reconstruction option. To find the answer to this problem, many buildings are carefully investigated with the help of measurements, interviews, and simulations. This paper presents the analysis and results of the investigation of the impact of lifestyle on the energy demand of a single family house. The impact on energy performance of the most important parameters was observed by systematically changing parameters such as changing from a decentralized to a centralized heating system, considering various technologies and fuels for producing electricity and heat, use of renewable energy sources. Different occupant behaviours were changed systematically. The effects of these measures are analysed with respect to primary energy use, CO₂ emissions and energy costs. The results of these investigations show that the lifestyle and occupants’ living standard is mainly responsible for the differences between the calculated and measured energy consumption.     

Evaluation of the corrected seasonal energy demand, for buildings classification, to be compared with a standard performance scale

In the European panorama, the relevant increase of the buildings energy consumptions has resulted, from the normative point of view (European directive 2002/91/EC [European Parliament and Council of December 16th, 2002 on the energy performance of buildings, Official Journal of the European Communities, L 1/65] and the relative national norms - for example Italian Decrees 192/05-311/06), in the imposition of minimum standards of construction, limiting the specific energy requirements specifically for heating and cooling. Moreover, in some countries it is being started to introduce, for buildings that respect the minimum performances levels imposed, incentive and defiscalization measures, function of their particular energetic efficiency and the corresponding performance class.Therefore, to compare the construction quality of different buildings, through energy performance classification, the authors propose a procedure for the determination of the corrected energy demand, separately for heating and cooling, independent of buildings location and directly comparable to a standard seasonal performance scale, defined on the entire territory of application.The procedure is so developed through simulation on a wide range of case-studies and then tested on a different buildings set: its effectiveness results in the attribution to each building test of an univocal performance class, providing an energy performance evaluation not affected by the building localization.     

Primary energy implications of ventilation heat recovery in residential buildings

In this study, we analyze the impact of ventilation heat recovery (VHR) on the operation primary energy use in residential buildings. We calculate the operation primary energy use of a case-study apartment building built to conventional and passive house standard, both with and without VHR, and using different end-use heating systems including electric resistance heating, bedrock heat pump and district heating based on combined heat and power (CHP) production. VHR increases the electrical energy used for ventilation and reduces the heat energy used for space heating. Significantly greater primary energy savings is achieved when VHR is used in resistance heated buildings than in district heated buildings. For district heated buildings the primary energy savings are small. VHR systems can give substantial final energy reduction, but the primary energy benefit depends strongly on the type of heat supply system, and also on the amount of electricity used for VHR and the airtightness of buildings. This study shows the importance of considering the interactions between heat supply systems and VHR systems to reduce primary energy use in buildings.     

Opportunities for reversible chillers in office buildings in Europe

Europe with more than 600 millions of square meters of air-conditioned office buildings offers an opportunity to save energy and reduce CO₂ emissions by reconverting chillers into reversible heat pumps in office buildings. One of the questions asked in the framework of the IEA ECBCS Annex 48 is how to assess the energy saving potential and how to identify the most interesting building cases. The methodology proposed here is based on the simulation of office buildings representative of the building stock. The energy consumption has been simulated for different office building types in five European climatic zones on the one hand with boilers for heating and chillers for cooling, and on the other hand with reversible chillers plus back-up boilers. The results of the simulations in terms of energy consumption allow us to assess the primary energy savings and CO₂ emission reduction in Europe by reconverting chillers into reversible heat pumps. The results show that the potential of annual primary energy savings and annual CO₂ emission reduction are about 8 TWh_PE and 3 millions of tons of CO₂ in Europe-15. Even if the temperature level in terminal units can be solved using the cooling coil instead of the heating coil, a back up boiler turns generally out to be required for the coldest days in the year or when simultaneous heating and cooling demands occur.     

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.     

工业余热——新型建筑替代能源的应用分析

分析工业余热作为一种新型建筑替代能源的适用性。结合工业余热特点,详细阐述工业余热建筑应用的特殊性;从相关数据及品位匹配性的角度,指出我国工业余热建筑应用的巨大潜力,以及在建筑节能、工业节水等方面的显著效益;从工业余热利用效果、建设运行成本、政策法规支撑、建筑节能服务市场机制等方面,进一步探讨目前工业余热建筑应用存在的关键难点,并研究相应的解决思路。     

Sensitivity of the total heat loss coefficient determined by the energy signature approach to different time periods and gained energy

In order to identify buildings that have energy saving potential there is a need for further development of robust methods for evaluation of energy performance as well as reliable key energy indicators. To be able to evaluate a large database of buildings, the evaluation has to be founded on available data, since an in-depth analysis of each building would require large measurement efforts in terms of both parameters and time. In practice, data are usually available for consumed energy, water, and so on, namely consumption that the tenants or property holder has to pay for. In order to evaluate the energy saving potential and energy management, interesting key energy indicators are the total heat loss coefficient K_tot (W/K), the indoor temperature (T_i), and the utilisation of the available heat (solar radiation and electricity primarily used for purposes other than heating). The total heat loss coefficient, K_tot, is a measure of the heat lost through the building's envelope, whereas T_i and the gained energy reflect the user's behaviour and efficiency of the control system.In this study, a linear regression approach (energy signature) has been used to analyse data for 2003-2006 for nine fairly new multifamily buildings located in the Stockholm area, Sweden. The buildings are heated by district heating and the electricity used is for household equipment and the buildings’ technical systems. The data consist of monthly energy used for heating and outdoor temperature together with annual water use, and for some buildings data for household electricity are also available. For domestic hot water and electricity, monthly distributions have been assumed based on data from previous studies and energy companies. The impact on K_tot and T_i of the time period and assumed values for the utilised energy are investigated.The results show that the obtained value of K_tot is rather insensitive to the time period and utilised energy if the analysis is limited to October-March, the period of the year when the solar radiation in Sweden yields a minor contribution to heating. The results for the total heat loss coefficient were also compared to the calculations performed in the design stage; it was found that K_tot was on average 20% larger and that the contribution to heating from solar radiation was substantially lower than predicted. For the indoor temperature, however, the utilised energy had a large impact.With access to an estimate of K_tot and T_i, an improved evaluation of the energy performance may be achieved in the Swedish real estate market. At present the measure commonly used, despite the fact that monthly data is available, is the annual use of energy for space heating per square metre of area to let.     

European residential buildings and empirical assessment of the Hellenic building stock,energy consumption,emissions and potential energy savings

The existing building 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 (currently at about 48%) and comply with the Kyoto Protocol to reduce carbon dioxide emissions. This is also in accordance to the European Directive (EPBD 2002/91/EC) on the energy performance of buildings, which is currently under consideration in all EU member states. This paper presents an overview of the EU residential building stock and focuses on the Hellenic buildings. It elaborates the methodology used to determine the priorities for energy conservation measures (ECMs) in Hellenic residential buildings to reduce the environmental impact from CO₂ emissions, through the implementation of a realistic and effective national action plan. A major obstacle that had to overcome was the need to make suitable assumptions for missing detailed primary data. Accordingly, a qualitative and quantitative assessment of scattered national data resulted to a realistic assessment of the existing residential building stock and energy consumption. This is the first time that this kind of aggregate data is presented on a national level. Different energy conservation scenarios and their impact on the reduction of CO₂ emissions were evaluated. Accordingly, the most effective ECMs are the insulation of external walls (33–60% energy savings), weather proofing of openings (16–21%), the installation of double-glazed windows (14–20%), the regular maintenance of central heating boilers (10–12%), and the installation of solar collectors for sanitary hot water production (50–80%).     

我国北方地区居住建筑节能率再提高的瓶颈问题分析

对比我国北方地区不同时期的居住建筑节能标准与发达国家相关标准,发现我国建筑节能设计标准尚有待提高。以某多层住宅为例,按照我国建筑节能率的计算方法,计算出芬兰2008年与2010年节能设计标准可以达到的节能率水平;并对实现不同节能率的建筑围护结构保温方案进行了分析,找出我国北方地区居住建筑节能设计标准再提高的瓶颈问题,包括高性能围护结构保温产品匮乏、现有产品的成本过高以及新风耗热量比例过大。建议在引进和吸收国外先进产品与技术的同时,加强国内产品和施工工艺的研发,采用有组织通风换气的热回收,以及加大可再生能源在建筑供能系统中的应用比例等应对策略。探讨了我国建筑节能标准再提高的技术路线。     

Development of system concepts for improving the performance of a waste heat district heating network with exergy analysis

The building sector is responsible for a great share of the final energy demand and national CO₂ emissions in countries like Germany. Nowadays, low quality thermal energy demands in buildings are mainly satisfied with high-quality sources (e.g. natural gas fired in condensing boilers). Exergy analysis, pursuing a matching in the quality level of energy supplied and demanded, pinpoints the great necessity of substituting high-quality fossil fuels by other low quality energy flows, such as waste heat. In this paper a small district heating system in Kassel (Germany) is taken as a case study. Results from preliminary steady-state and dynamic energy and exergy analysis of the system are presented and strategies for improving the performance of waste-heat based district heating systems are derived. Results show that lowering supply temperatures from 95 to 57.7 °C increases the final exergy efficiency of the systems from 32% to 39.3%. Similarly, reducing return temperatures to the district heating network from 40.8 to 37.7 °C increases the exergy performance in 3.7%. In turn, the energy performance of all systems studied is nearly the same. This paper shows clearly the added value of exergy analysis for characterising and improving the performance of district heating systems.     

Applying a multi-objective optimization approach for Design of low-emission cost-effective dwellings

Modern buildings and their HVAC systems are required to be not only energy-efficient but also produce fewer economical and environmental impacts while adhering to an ever-increasing demand for better environment. Research shows that building regulations which depend mainly on building envelope requirements do not guarantee the best environmental and economical solutions. In the current study, a modified multi-objective optimization approach based on Genetic Algorithm is proposed and combined with IDA ICE (building performance simulation program). The combination is used to minimize the carbon dioxide equivalent (CO₂-eq) emissions and the investment cost for a two-storey house and its HVAC system. Heating/cooling energy source, heat recovery type, and six building envelope parameters are considered as design variables. The modified optimization approach performed efficiently with the three studied cases, which address different summer overheating levels, and a set of optimal combinations (Pareto front) was achieved for each case. It is concluded that: (1) compared with initial design, 32% less CO₂-eq emissions and 26% lower investment cost solution could be achieved, (2) the type of heating energy source has a marked influence on the optimal solutions, (3) the influence of the external wall, roof, and floor insulation thickness as well as the window U-value on the energy consumption and thermal comfort level can be reduced into an overall building U-value, (4) to avoid much of summer overheating, dwellings which have insufficient natural ventilation measures could require less insulation than the standard (inconsistent with energy saving requirements) and/or additional cost for shading option.     

Building signatures: A holistic approach to the evaluation of heating and cooling concepts

A sustainable and environmentally responsible building concept aims at a high workplace comfort, a significantly reduced heating and cooling demand, a high-efficient plant system, and the use of renewable energy sources to condition the built environment. This paper presents a comprehensive analysis of the heating and cooling concepts of 11 low-energy buildings in terms of energy use, efficiency and occupant thermal comfort. All buildings investigated employ environmental energy sources and sinks – such as the ground, ground water, rainwater and the ambient air – in combination with thermo-active building systems. A limited primary energy use of about 100 kWh_prim/(m²_neta) as a target for the complete building service technology (HVAC and lighting) was postulated for all buildings presented. With respect to this premise, a comprehensive long-term monitoring in high time resolution was carried out for two to five years, with an accompanying commissioning of the building performance. Measurements include the useful heating and cooling energy use, auxiliary energy use for the hydraulic system, as well as end and primary energy use, occupant thermal comfort and local meteorological conditions. A new methodology is proposed for a holistic approach to the evaluation of heating and cooling concepts, which not only considers the occupants thermal comfort, but also the useful energy consumption and the efficiency of the generation, distribution and delivery of heating and cooling energy.     

Development of a radiant heating and cooling model for building energy simulation software

Efficient radiant heating and cooling systems are promising technologies in slashing energy bills and improving occupant thermal comfort in buildings with low-energy demands such as houses and residential buildings. However, the thermal performance of radiant systems in buildings has not been fully understood and accounted for in currently available building energy simulation software. The challenging tasks to improve the applicability of radiant systems are the development of an accurate prediction model and its integration in the energy simulation software. This paper addresses the development of a semi-analytical model for radiant heating and cooling systems for integration in energy simulation software that use the one-dimensional numerical modeling to calculate the heat transfer within the building construction assemblies. The model combines the one-dimensional numerical model of the energy simulation software with a two-dimensional analytical model. The advantage of this model over the one-dimensional one is that it accurately predict the contact surface temperature of the circuit-tubing and the adjacent medium, required to compute the boiler/chiller power, and the minimum and maximum ceiling/floor temperatures, required for moisture condensation (ceiling cooling systems), thermal comfort (heating floor systems) and controls. The model predictions for slab-on-grade heating systems compared very well with the results from a full two-dimensional numerical model.     

Influence of building parameters and HVAC systems coupling on building energy performance

The performance of different HVAC systems varies when coupled with different buildings. This paper examines the relationship between building heating and cooling load and subsequent energy consumption with different HVAC systems. Two common HVAC systems in use throughout the UK office building stock, variable air volume (VAV) system and fan coil (FC) with dedicated outside air system, have been coupled with a typical narrow plan office building with and without daylight control and for both cellular and open plan.The results presented in this paper clearly indicate that it is not possible to form a reliable judgment about building energy performance based only on building heating and cooling loads. For the two investigated systems, variable air volume system and fan coil with dedicated outside air system, the difference between system demand and building demand varied from over −40% to almost +30% for cooling and between −20% and +15% for heating. If a heat recovery unit is used, the difference in heating performance is even greater, rising to −70%.     

A new methodology for renewable and rational use of energy policy in building sector: Case study for the island of Crete

This paper discusses the future development of efficient energy policies with respect to building sector, using a new simulation computer model called INVERT. The building sector incorporates supply side systems (heating, domestic hot water (DHW) and cooling systems) and Demand Side Management (DSM) measures. Simulation runs have been carried out up to 2020 for the Greek island of Crete based on sensitivity analyses for different building types, heating/cooling technologies and DHW systems. Promotion schemes for renewable energy sources (RES) and rational use of energy (RUE) are also implemented in the simulation model, since they have a strong impact on long-term financial investment strategies. Transfer costs and CO₂ emissions of various hypothesis scenarios about new or additional promotion schemes for energy conservation in residential buildings have been compared with a reference scenario for the island of Crete. The outcome of this case study is presented and discussed in this paper.     

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 consumption and conservation in the Russian apartment building stock

Energy consumption of buildings in Russia and other states of the former Soviet Union has typically been reported in very coarse terms, as annual energy use normalized by weather and floor area. Reported figures, based on estimates derived from available energy-delivery data, have shown that Russian residential buildings consume on the order of twice as much primary energy for space-heating as those in some developed Western countries. Reports have been accompanied with qualitative assertions that higher levels of insulation, reduced air infiltration, and better control of heating systems could reduce energy use. However, there has been a dearth of data that first distinguish Russian buildings by construction type and insulation level, and second attempt to quantitatively pinpoint causes for the relatively high energy use. Such data are needed to focus contemporary energy-conservation efforts in Russia on the most promising areas. This paper presents a preliminary set of information that illuminates these areas, concentrating on the city of Moscow. The analysis breaks down Moscow's district-heated apartment building stock by type and year of construction and by the required thermal standards in force at the time of construction. It aggregates these buildings into three classes according to the type of external wall construction — brick or large block, single-layer panel, and three-layer panel — and estimates overall annual energy use for space-heating via a steady-state model. It then compares predicted and measured energy use, for the aggregation and, more accurately, for a single building for which detailed energy-use data are available. In both cases there is a large discrepancy, with actual space-heating energy use exceeding design predictions by at least 60%. Analytical efforts to reconcile the excess energy consumption for the metered building strongly suggest that the most important cause of relatively high space-heating energy use in the building is poor control of heat delivery from the district heating system.