Primary energy implications of end-use energy efficiency measures in district heated buildings

In this study we explore the effects of end-use energy efficiency measures on different district heat production systems with combined heat and power (CHP) plants for base load production and heat-only boilers for peak and medium load productions. We model four minimum cost district heat production systems based on four environmental taxation scenarios, plus a reference district heat system used in Östersund, Sweden. We analyze the primary energy use and the cost of district heat production for each system. We then analyze the primary energy implications of end-use energy efficiency measures applied to a case-study apartment building, taking into account the reduced district heat demand, reduced cogenerated electricity and increased electricity use due to ventilation heat recovery. We find that district heat production cost in optimally-designed production systems is not sensitive to environmental taxation. The primary energy savings of end-use energy efficiency measures depend on the characteristics of the district heat production system and the type of end-use energy efficiency measures. Energy efficiency measures that reduce more of peak load than base load production give higher primary energy savings, because the primary energy efficiency is higher for CHP plants than for boilers. This study shows the importance of analyzing both the demand and supply sides as well as their interaction in order to minimize the primary energy use of district heated buildings.     

热泵辅助太阳能中央热水系统压缩机选择研究

采用热泵来完全或部分替代传统的电加热器,可使太阳能中央热水系统全天候工作,同时可降低运行费用。但压缩机类型不同不仅会影响系统的可靠运行范围,也造成其运行费用有所差异。本文选用两种方案进行分析研究,方案1使用MT60活塞压缩机,而方案2采用ZR61涡旋压缩机,在方案2中保留电加热器,建立了合适的数学模型,根据2005年西安地区气象数据、压缩机安全运行和性能曲线进行了模拟计算。结果表明,ZR61系统具有更好的节能效果,但是其结构略显复杂,同时需要更大的配电能力。     

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.     

Energy efficiencies of heat pumps in residential buildings

Using the state-of-the-art computer program, DOE 2.1A, the hourly and resulting seasonal coefficients of performance of four residential heat pumps were simulated for a typical house in one city in each of the four major climate zones in the U.S. For purposes of comparison a conventional gas furnace and air conditioner system were also analyzed. This study shows that heat pump systems could be developed with seasonal thermodynamic efficiencies of over 200% in resource energy. In addition, sizing the heat pumps according to a building's thermal integrity and operating conditions maximizes seasonal efficiencies.     

Primary energy and comfort performance of ventilation assisted thermo-active building systems in continental climates

This article presents a simulation study comparing the primary energy and comfort performance of ventilation assisted thermo-active building systems (TABS) relative to a conventional all-air (VAV) system in a compact office building featuring good thermal envelope performance, heat recovery, and solar gain control for the continental climate of Omaha, Nebraska with pronounced heating and cooling periods. TABS heating is accomplished using a geothermal heat pump and TABS cooling using a geothermal heat exchanger without an additional vapor compression cycle required. It was found that the coordination of the TABS and VAV systems is crucial, i.e., supply air temperature and active layer temperature setpoints and reset schedules greatly affect the performance of the overall system. The small contribution of TABS in the heating case shows the need for the adaptation of the ventilation system configuration to the TABS system. Annual cooling energy demand for the ventilation assisted TABS is higher than for the pure VAV system, which is due to lower occupied period room operative temperatures and thus a higher comfort provided. While a 4% useful energy penalty for the combined TABS/VAV was recorded, the VAV case requires 20% more delivered energy than the TABS case because of the displacement of compressor driven coil loads with low-exergy cooling through the ground heat exchanger in the TABS case. A primary energy intensity of 189 kWh/m² a was recorded for the TABS case; in contrast, the conventional all-air (VAV) equipped building incurs a primary energy intensity of 229 kWh/m²a, which represents a penalty of 20%. Clear advantages of the TABS approach can be observed with respect to thermal comfort: during summer cooling periods, the mean radiant temperature of the TABS case is on average 2 K below that of the VAV case. Moreover, the VAV system is associated with a fairly constant predicted mean vote (PMV) value of 0.75, which is quite warm, while the TABS equipped system reveals an average of 0.56, which results in only 12% instead of 17% of people dissatisfied. Based on these results, ventilation assisted thermo-active cooling systems appear to be a very promising alternative to conventional all-air systems offering both significant primary energy as well as thermal comfort advantages provided the TABS is mated with low-exergy heating and cooling sources.     

The potential of wastewater heat and exergy: Decentralized high-temperature recovery with a heat pump

There is a large potential in the heat losses from the wastewater leaving a building. We present a novel concept for recovering this heat. Instead of recovering it in a mixed state, the recovery immediately after use is evaluated. This allows the exploitation of the higher temperatures found at the points of warm water usage. By integrating a heat pump to utilize this heat, we can produce a higher temperature heat supply while maintaining a low temperature-lift requirement. This leads to the possibility of directly regenerating the hot water supply through wastewater heat recovery. The concept is a result of research into low exergy building systems, and is part of the IEA ECBCS Annex 49. We have modeled the annual performance of two different system scenarios, which result in a potential average annual coefficient of performance (COP) of over 6. The first scenario supplies up to 4400 kWh of heat for all hot water events with only 790 kWh of electricity, while the second scenario regenerated directly the hot water supply just for bathroom fixtures at 2400 kWh with just 410 kWh of energy. This is a significant reduction in the demand for hot water supply of a building compared to most modern installations.     

An influence of weather conditions on heat demand in district heating systems

The article deals with the problems of determining heat power in a heating system taking into consideration solar radiation surpluses as well as increase in heat demand resulting from a higher wind speed. It is relatively simple to calculate these surpluses and heat losses for a single building. However, it is much harder or sometimes impossible, to estimate heat losses and surpluses related to solar radiation and wind influence for building complexes heated by a heating system. Results of the empirical research of these processes allow to properly, and in advance, steer the work of the heat source or sources feeding the heating system.     

住宅分户热计量系统的实施探讨

从分户热计量的实施方法、内客进行了探讨。     

住宅能耗现状及节能措施

简述了我国住宅建设的能耗现状及其节能潜力,提出四条可行的有效的节能措施。     

住宅集中供暖系统分户热计量和收费的若干问题

认为供暖设计中应考虑户间传热的因素,共用供回水立管和分户独立系统相结合是适合分户热计量的系统制式。探讨了户内系统的布置方式。提出应根据不同户型,围护结构特性、户间传热等因素确定热价和热费的分配比例,目前应注重改进设计消除失调,提高供暖质量并以合理的运行调节实现节能。     

住宅的集中供热供暖系统和节能

指出住宅供暖方式的主体仍将是集中热源供暖系统，实行分户计量和收费的难度在于热量定价影响因素的复杂性、适合国情的热表的开发和应用、尤其是与此相应的新的供暖制式的探索，在传统供暖制式下应以大力提高供暖均匀性为重要的节能手段。分析了室温可调性问题和散热器恒温阀的应用条件和范围。     

Introduction to integration of renewable energy in demand controlled hybrid ventilation systems for residential buildings

In the scope of the EU supported project RESidential buildings HYbrid VENTilation (RESHYVENT), the possible integration of renewable energy solutions (RES) into hybrid ventilation systems has been analysed. The focus has been on solar and wind applications to substitute the use of fossil fuel. The feasibility of the investigated options depends on the ventilation concept the RES is integrated into, the location of the building geographically, placement of the RES in the building and on the urban environment. This paper describes the different renewable technologies, options and constrains in connection with integration into hybrid ventilation systems.     

国外空气-空气能量回收通风装置标准比较

介绍了美国、日本、加拿大及欧洲的相关标准，在适用范围、产品分类、检验项目、试验工况参数、试验装置及样本等方面进行了分析比较。为我国正在编制的标准提出一些建议。     

可再生能源在武汉某住宅建筑中的应用分析

以一住宅小区工程为例,分析了地源热泵和太阳能照明在住宅建筑中的应用.通过方案比较与节能分析,指出了可再生能源在住宅建筑中的应用前景.     

新建居住建筑采暖节能小议

阐述了新建居住建筑采暖的两种基本形式：双立管水平串联式散热器采暖系统和低温热水地板辐射采暖系统,介绍了居住建筑采暖节能的主要方向和措施,以实现节约能源的目的。     

住宅建筑能耗统计方法的研究

根据我国建筑热工气候区划下的气候、社会等条件以及供暖空调方式等特点,提出了住宅建筑能耗统计体系的框架。从住宅建筑概况、住户基本资料、能耗设备的拥有量和使用情况以及住宅能耗量等方面建立起住宅建筑能耗统计指标体系,在此基础上制定了整套报表以对市、省以及全国范围内的住宅建筑能耗情况逐层进行统计,并以湖南省某市住宅建筑能耗情况为例进行统计分析,以验证统计方法的可行性。     

Criteria for use of groundwater as renewable energy source in geothermal heat pump systems for building heating/cooling purposes

Environmental protection measures are conducted directly by the use of renewable energy sources. The energy development of cities in Europe is aimed at the sustainable use of renewable energy sources in order to achieve the substitution of fossil fuels and the reduction of the hazardous gas emission into the atmosphere. Geothermal resources of medium and low enthalpy in Europe being used for obtaining heat energy are providing about 6600 MW_t, currently having the growth trend of 50 MW_t annually. The use of geothermal low enthalpy, namely of subgeothermal groundwater resources, has even higher annual growth rate, and if such a trend is kept till the year 2010, the produced energy will amount about 8000 MW_t. Criteria of the groundwater use as a hydrogeothermal energy resource in heat pumps are complex, and they deal with aspects of incoming temperatures and groundwater quantities. The precise limit temperature of groundwater that would separate the direct use of geothermal energy (only by the use of heat exchangers), and indirectly by the use of a heat pump has not been determined in the professional and scientific practice of Serbia so far. Taking into account that relatively small number of new flat is being built in Serbia nowadays, if we want to save energy it is necessary to carry out the energy reconstruction of the existing flats whose number is estimated to be more than 2.8 million. By the application of subgeothermal energy and the use of heat pumps, energy consumption would be significantly reduced.     

《采暖居住建筑节能检验标准》解读

该标准对采暖居住建筑的节能检验项目、应用类别、仪器仪表的性能要求、检测方法和检验规则作出了明确规定。     

Development and experimental validation of a high-temperature heat pump for heat recovery and building heating

The performance of a high-temperature heat pump unit using geothermal water for heat recovery in buildings is experimentally evaluated. The unit consists of a twin-screw refrigeration compressor, a condenser, an evaporator and an oil cooling system. The effect of the cooled oil temperature on the performance of the heat pump unit is experimentally investigated. Results show that the unit stably produces outlet hot water at a constant temperature of 85 °C and performs well in a wide range of high-temperature conditions with a high energy efficiency ratio. The results also indicate that the key to improving the performance of a high-temperature heat pump unit often depend on the selection of proper cooled oil temperature. The optimum cooled oil temperature is 50-65 °C when the condensing temperature is above 70 °C. At these temperatures, the oil cooling system can increase the energy efficiency ratio of the heat pump by 6.3%.