A simulation appraisal of performance of different HVAC systems in an office building

The article reports on a simulation appraisal of energy consumption, energy costs and environment impact of three systems used for space heating, and space cooling of an office building in Kragujevac, Serbia. Three investigated systems are (1) a system with a natural gas boiler and convective baseboard heaters for water space heating and window air conditioners for air space cooling; (2) a system with a natural gas boiler and individual air reheaters for air space heating and a chiller plant for air space cooling; and (3) an air-to-air heat pump for air space heating, and cooling. The systems are modeled and simulated by using EnergyPlus software. After simulations, it is found that the first investigated system has the highest energy efficiency, the best economy, and the lowest environmental impact. That is because of the fact that the first system has water as a heating medium and uses predominantly natural gas as fuel. However, in future, when for generation the grid electrical energy requires less primary energy, and becomes decarbonized, the third system would be best to conserve energy resources and environment.     

Addressing climate change in comfort standards

According to the Buildings Energy Data Book published by the U.S. Department of Energy, in 2006 the building sector consumed 38.9% of the total primary energy used in the United States. Of this energy, 34.8% is used by buildings for space heating, ventilation, and air conditioning. This energy often involves the combustion of fossil fuels, contributing to carbon dioxide emissions and climate change. Even if greenhouse gas concentrations are stabilized in the atmosphere, extreme climate events and sea level rise will continue for several centuries due to inertia of the atmosphere. Therefore, adaptation will be a necessary compliment to carbon dioxide mitigation efforts. This paper argues that both mitigation of greenhouse gases and adaptation to climate change should be added to our building codes and standards. Since space heating, ventilation, and air-conditioning utilize a large amount of energy in buildings, we should begin by redefining our thermal comfort standards and add strategies that mitigate carbon dioxide emissions and adapt to predicted climate variability.     

太阳能热泵-地板辐射供热系统实验研究

实验研究了太阳能热泵-地板辐射供热系统的性能,并与燃油、燃气锅炉集中供热系统进行了经济性分析比较。实验结果表明,热管真空管集热器的集热效率为64·4%,U形管真空管集热器的集热效率为59%,热泵机组的能效比为3·08;室内温度变化相对机组供热时间滞后3h,有利于采用间歇运行方式降低运行费用。经济性分析结果表明,在青岛地区为节能型建筑供热时,该系统的单位面积费用年值介于燃气、燃油锅炉集中供热之间。     

我国住宅建筑节能潜力分析——除供暖外的住宅建筑能耗

城镇民用建筑能源消耗分为北方地区供暖能耗、除供暖外的住宅能耗、除供暖外的一般性非住宅民用建筑和大型公共建筑能耗四部分,着重分析了其中的除供暖外的住宅能耗。首先,阐述了我国住宅建筑能耗的现状,指出目前我国住宅建筑能耗水平较低,但呈现加速增长的趋势;其次,针对我国住宅建筑能耗的刚性增长趋势,提出了住宅建筑节能的重点——住宅空调器升级与更新、降低照明能耗和减少家电待机损失。并分析计算了三个方面的节能措施所能达到的实际节能效果。     

Calculation of the yearly energy performance of heating systems based on the European Building Energy Directive and related CEN standards

According to the Energy Performance of Buildings Directive (EPBD) all new European buildings (residential, commercial, industrial, etc.) must since 2006 have an energy declaration based on the calculated energy performance of the building, including heating, ventilating, cooling and lighting systems. This energy declaration must refer to the primary energy or CO₂ emissions.The European Organization for Standardization (CEN) has prepared a series of standards for energy performance calculations for buildings and systems. This paper presents related standards for heating systems. The relevant CEN-standards are presented and a sample calculation of energy performance is made for a small single family house, an office building and an industrial building in three different geographical locations: Stockholm, Brussels, and Venice.The additional heat losses from heating systems can be 10-20% of the building energy demand. The additional loss depends on the type of heat emitter, type of control, pump and boiler.     

建筑组团方式对高密高层居住建筑立面太阳能热利用影响分析

随着城市化进程的发展,高密高层住宅已经成为现阶段居住建筑主导.因此,建筑立面安装分体式太阳能热水系统已成为大势所趋,但此系统应用受到建筑布局与建筑间距的影响.在现有居住建筑常见组团方式及相关规划设计标准的基础上,选择上海市常见的高层住宅形式,利用日照分析软件建立模型,模拟分析全年建筑遮挡关系对建筑立面分体式太阳能热水系...     

基于模糊数学的集中供暖方式的对比研究

作为可再生能源在集中供暖中的应用技术,生物质锅炉的能源性、社会效益、技术导向是否优于传统热源的判定对于其在我国城镇的推广应用具有重要的现实意义.本文选用模糊数学的方法,构建综合评价模型,将生物质锅炉集中供暖与天然气锅炉、煤锅炉集中供暖在能源性、社会效益、技术导向方面进行对比分析,计算结果表明:生物质锅炉取得了最好的优度...     

地源热泵与蓄热式电锅炉冬季制热的节能性实测与分析

地源热泵作为一种节能环保的新型冷热源,越来越受到关注,并逐步推广应用.针对夏热冬冷地区冬季上海市某建筑,利用土壤源热泵加干盘管联合制热对办公用房进行供暖,且在相同制热量的情况下对比蓄热电锅炉系统,对两种能耗进行分析,发现在考虑初投资的情况下,地源热泵比蓄热式电热锅炉节能约35.1％.     

Indoor thermal environment and energy saving for urban residential buildings in China

The purpose of this survey is to investigate the actual conditions of the residential indoor thermal environment in urban areas in China for evaluating thermal comfort and predicting the energy conservation feasibility for space heating and cooling.The apartment homes under investigation were located in the urban areas of nine major cities. The questionnaire survey revealed building characteristics, the types of space heating and cooling system in use, aspects of life style, during winter and summer seasons, and so on. The measurement showed that winter indoor temperatures in Harbin, Urumqi, Beijing and Xi’an remain at a relatively stable level near 20 °C due to the central heating system installed. However in the other cities lacking central heating systems, indoor temperatures fluctuated as a function of the change of outdoor temperature. On the other hand, summer indoor evening temperatures in Shanghai, Changsha, Chongqing and Hong Kong were higher than the comfort zone of ASHRAE. Therefore it is expected that energy use for space heating and cooling in the southern China will increase in the near future because of occupants’ requirement for comfortable indoor environment. Based on the results yielded by this study, in Beijing the calculation of space heating and cooling loads indicated that the energy used to heat indoor spaces can be halved by installing thermal insulation and properly sealing the building.     

燃气锅炉运用分析

结合我国能源结构特点，从家用燃气锅炉单户采暖、分散燃气锅炉采暖及区域燃气锅炉集中采暖三方面，对燃气锅炉三种采暖形式作了介绍，以提高其技术经济效益。     

Determination of heat losses in biogas installations

Insulation has contributed a major part of the energy efficiency improvements so far achieved in domestic buildings, but much less in non-domestic buildings. This reflects more predominant space heating costs in housing compared with other buildings, and the existence of more attractive investment options (e.g. Building Energy Management Systems (BEMS)) for non-domestic buildings. Some of the lessons to be learnt from relevant Building Research Energy Conservation Support Unit/Energy Efficiency Office (BRECSU/EEO) demonstration projects undertaken on behalf of the EEO are briefly discussed.

At present BRECSU is encouraging a more systematic approach to the design of new buildings and major refurbishments, which by virtue of energy-efficiency, will minimize the additional capital costs against a performance specification. One of the main features of such design types will be sufficiently high levels of insulation to make centralized space heating unnecessary, thus permitting large savings on the capital cost of services. An indication is given of the types of project BRECSU wishes to support in future.     

Control of heating systems in residential buildings: Current practice

Heating is the most important energy consumer for households in Belgium. The primary energy consumption of a heating system is determined by the net energy demand of the building, but also by the efficiency of the equipment and the way it is used by the inhabitants.

To estimate the potential primary energy savings, today's situation should be analysed first. Therefore, the results of two surveys are combined to sketch current practice in Belgium. The most common systems in Western Europe, i.e. gas boilers combined with radiators, are then simulated to test their performance in dwellings with varied insulation quality. Typical internal heat gains and set temperature profiles are included, but the influence of the inhabitant behaviour on the heating efficiency is not studied as such.

The results show that current practice does lead to important energy losses, resulting in overall efficiencies as low as 30%, but improvements are possible by using intelligent controllers. However, correct boiler sizing and a sound combination of boiler and heat emitter control are still required to ensure high heating system efficiencies, especially for better insulated buildings with a high heat balance ratio.     

Effects of Global Climate Change on Building Energy Consumption and Its Implications in Florida

ABSTRACT

Many studies have investigated the impact of global warming on energy consumption. In this study, the morphing method and EnergyPlus (E+) software were used to investigate the impact of climate change on commercial building energy use under the A2 medium-CO₂. emission scenario. The study simulated electricity and gas consumption of nine types of commercial buildings in eight cities, representing three climate zones in Florida. The nine types of commercial buildings included apartments, hotels, offices, and schools. The energy simulation results showed the future trends of growth and reduction in electricity and gas consumption for cooling and heating in TMY2 (TMY3), 2020, 2050, and 2080 in the eight selected cities. In general, gas and electricity demands for heating are projected to decrease, and electricity demand for cooling increases, at different rates in various areas of Florida. The study provides guidance for policy‐makers and utility companies as they craft their response to climate change in various regions of Florida.     

城市集中供热方式的探讨

城市集中供热方式可分为热电厂集中供热系统、锅炉房集中供热系统、混合系统。热电厂的突出特点是热电合产,使能源的有效利用程度提高,从而能节约燃料。但受诸多因素制约。集中锅炉房节能效果较热电厂差,但热电厂种种制约条件致使其不可能全部替代集中锅炉房,二者长期共存将起到取长补短的作用。应广泛探索提高集中供热经济性途径,使城市集中供热在节能工作中发挥应有的作用。     

关于燃气锅炉入户供暖问题

通过对某小区采用的燃气锅炉入户供暖方案的分析，认为这种独立式供暖方式存在技术、经济、安全、环保等问题；可用于别墅，但不宜用于多层或高层住宅建筑。     

Comparison of natural gas driven heat pumps and electrically driven heat pumps with conventional systems for building heating purposes

Electrically driven heat pumps achieve good efficiencies for space heating. If heat pumps are driven directly by a combustion engine instead of an electric motor, losses attributed to the production and transport of electricity are eliminated. Additionally, the use of the combustion engine's heat leads to a reduced temperature difference across the heat pump. This article presents annual efficiencies of these systems and compares internal combustion engine and electrically driven heat pumps in terms of primary energy consumption and CO₂ emissions. Because heat pump performance depends strongly on the heating circuit's flow temperature level, the comparison is performed for air-to-water and geothermal heat pump systems in two cases of maximum flow temperatures (40 °C and 60 °C). These temperature levels represent typical modern buildings with large heating surfaces and older buildings with high-temperature radiators, respectively. In addition to the different heat pump setups, conventional space heating systems are included in the comparison. The calculations show that natural gas-driven heat pumps achieve about the same efficiency and CO₂ emissions as electrically driven heat pumps powered with electricity from the most modern natural gas-fired combined cycle power plants. The efficiency of such systems is about twice that of conventional boiler technologies.     

Statistical analyses on winter energy consumption characteristics of residential buildings in some cities of China

The purposes of this paper are to analyze winter energy use of residential buildings in different cities of China, and to figure out the influence factors of winter residential energy use. The investigated residences were located in seven typical cities of five architectural thermotechnical design zones. Questionnaire surveys revealed building characteristics, household characteristics, the utilization of domestic appliances, and thermal environment in winter. Winter energy consumption in different cities bears obvious regional characteristics. In south China, Hong Kong has the largest mean household energy use amount, and Changsha and Chongqing follow Hong Kong; Kunming in the warm zone has the small energy use. In north cities, if district space heating is excluded from total energy use, Urumqi and Xi’an have the energy use at the smallest level, but space heating use is very huge. The energy use amounts of space heating of Tangshan, Urumqi and Xi’an are several times as large as the amounts of all the end uses in the southern cities. The analysis on influence factors of winter energy use are made for Chongqing and Hong Kong, respectively, by Quantification Theory I, and the results show there exist obvious differences in influence factors between the two cities.     

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.     

太阳能热泵供热系统的应用及经济性分析

以0.7 MW的供热功率为评价标准,分别对太阳能热泵、燃油锅炉、燃气锅炉和电加热锅炉四种供热系统进行了初期投资、运行费用、燃料价格等因素的综合技术经济分析与评价,评价结果表明：太阳能热泵供热系统的综合效果最好,适合在青岛推广应用。     

Glazed spaces in Nordic climates

A semi-climatized zone in the shape of a glazed space is heated to some degree by solar radiation and to some degree by excess heat or heat loss from the main and fully insulated part of the building. Such a space will not offer full thermal comfort for permanent occupancy during the winter season, but it is useful for secondary functions such as circulation, storage, physical activities, etc. During the summer season glazed spaces will also be very attractive for ordinary occupancy.

A condition for energy conservation is that these spaces are not heated directly but utilize heat loss and possibly excess heat from the adjoining buildings. If they are properly positioned and constructed, they will also function as solar collectors.

The energy reduction potential will vary greatly with the relative size of the spaces, with the system installed, and with possibilities for long term storage. If the glazed space covers relatively large parts of the adjoining buildings, the reduced heat loss from these may be considerable. If in addition a certain minimum temperature can be kept in the glazed space, the need for heating in the adjoining buildings may be minimal.

Abroad such spaces are often used consciously as architectural elements due to their special spatial character. In countries like Norway they may in addition serve several needs resulting from the special climatic conditions.

SINTEF has developed energy conservation systems based on this concept and has tested them in experimental buildings. One example is the three solar energy houses in the Heimdal low energy dwellings project which totals 14 houses. Another example is a day care centre now under development for the local student union.