A parametrical study on the energetic and exergetic assessment of a solar-assisted vertical ground-source heat pump system used for heating a greenhouse

An energetic and exergetic modeling of a solar-assisted vertical ground-source heat pump (GSHP) greenhouse heating system (SAGSHPGHS) for system analysis and performance assessment is presented in this study. Energy (heating coefficient of performance ‘COP’) and exergy efficiencies at various reference and entering water temperatures are also determined. The actual thermal data collected are utilized for the model calculations at different reference temperature values in the range of −0.69 to 25 °C. Furthermore, the performance of a SAGSHPGHS, installed in Solar Energy Institute of Ege University, Izmir, Turkey, is evaluated to show, how energy and exergy efficiencies values change with system. The exergy destructions in the overall SAGSHPGHS are quantified, particularly for a reference temperature of −0.69 °C on 7 January 2004 for comparison purposes. Based upon the measurements made in the heating mode from the 16th of December 2003 till 31st of March 2004, average heating COPs of the GSHP unit and the overall system are obtained to be 2.84 and 2.27, respectively. The best (peak) COP of the GSHP and system were found to be 3.14 and 2.79 on 7 January 2004, respectively. Average exergy efficiency of the system is determined to be 68.11%, while the best exergy efficiency peak values for the GSHP unit and the whole system on a product/fuel basis are obtained to be 76.2% and 75.6%, respectively.     

太阳能-地源热泵串联复合式系统的性能研究

对于总热负荷与总冷负荷不平衡的建筑,单独采用土壤源热泵系统供暖或供冷时,系统运行末期土壤温度发生很大的变化,降低了系统的运行性能。针对此类建筑,搭建太阳能-土壤源串联复合式热泵系统,从集热器单位面积流量、存储水箱体积的影响因素出发,研究供暖期热泵机组蒸发器侧进水温度、系统运行性能和能耗的变化情况,为常规土壤源热泵系统引起的土壤热平衡问题提出解决方案,为今后的实际工程设计及应用提供参考依据。     

Exergetic modeling and assessment of solar assisted domestic hot water tank integrated ground-source heat pump systems for residences

The present study deals with the exergetic modeling and performance evaluation of solar assisted domestic hot water tank integrated ground-source heat pump (GSHP) systems for residences for the first time to the best of the author's knowledge. The model is applied to a system, which mainly consists of (i) a water-to-water heat pump unit (ii) a ground heat exchanger system having two U-boreholes with an individual depth of 90 m, (iii) a solar collector system composing of rooftop thermal solar collectors with a total surface area of 12 m², (iv) a domestic hot water tank with a electrical supplementary heater, and (v) a floor heating system with a surface of 154 m², and (vi) circulating pumps. Exergy relations for each component of the system and the whole system are derived for performance assessment purposes, while the experimental and assumed values are utilized in the analysis. Exergy efficiency values on a product/fuel basis are found to be 72.33% for the GSHP unit, 14.53% for the solar domestic hot water system and 44.06% for the whole system at dead (reference) state values for 19 °C and 101.325 kPa. Exergetic COP values are obtained to be 0.245 and 0.201 for the GSHP unit and the whole system, respectively. The greatest irreversibility (exergy destruction) on the GSHP unit basis occurs in the condenser, followed by the compressor, expansion valve and evaporator.     

地埋管地源热泵系统冬季运行测试研究

对武汉市清江花园小区地源热泵空调系统2007-2008年度冬季的运行情况进行了测试,分析了机组与系统的性能系数、地下土壤温度、地埋管换热量以及机组进出口水温等参数的变化.计算结果表明,在武汉地区(夏热冬冷地区)使用地源热泵系统节能效果显著.     

Effective design and operation of hybrid ground-source heat pumps: Three case studies

One innovation to ground-source heat pump (GSHP, or “geothermal”) systems is the hybrid GSHP (HyGSHP) system. A HyGSHP system can dramatically decrease the first cost of GSHP systems by using conventional technology (such as a cooling tower or a boiler) to meet a portion of the peak heating or cooling load. We monitored and analyzed three buildings employing HyGSHP systems (two cooling-dominated, one heating-dominated) to demonstrate the performance of the hybrid approach. The buildings were monitored for a year and the measured data was used to validate models of each system. Additionally, we used the models to analyze further improvements to the hybrid approach and established that it has positive impacts, both economically and environmentally. We also documented the lessons learned by those who design and operate the three systems, including discussions of equipment sizing, pump operation, and cooling tower control. Finally, we described the measured data sets and models from this work and have made them freely available for further study of hybrid systems.     

面向路基冻胀的地源热泵装置的设计与试验

针对中国季节性冻土区路基工程广泛存在的冻胀现象，通过路基工程与供热工程的学科交叉分析，提出将地源热泵技术引入路基工程。供热技术应用于路基工程的理念在于，在冬季通过人工热源主动地向路基输入热量，来实时地补偿热量损失，进而消除路基负温状态和冻胀现象。设计与制作一款面向路基工程的专用地源热泵装置，工作原理为蒸气压缩式热力学循环，换热方式为直接膨胀式，通过制冷剂的蒸发、压缩和冷凝实现地热能的搜集、品位提升和释放。该装置自成独立的制热单元，主要包括地表驱动部件和地层换热部件，前者包括压缩机、毛细管、控制器等；后者包括稳定地层集热段和冻胀地层供热段，结构型式为立式柱状。装置供热试验表明，供热温度可达50℃以上，集热温度可达?8℃以下，有效供热半径在1.4m以上。地源热泵装置具有主动供热的技术优势，可以为寒区路基防冻胀问题提供一种新方法。     

土壤源热泵系统能效提升要素分析

随着近几年节能减排政策的不断出台,土壤源热泵的应用范围和项目规模不断扩大,但是由于设计、施工及运行中存在的各种原因,一些已经投入使用的土壤源热泵系统工程的节能效果并不如人意。因此,从系统的角度出发,全面分析土壤源热泵系统能效提升中需要把握的几个关键要素,包括:保证低位热源的能量平衡、提高机组自控级别、优化水力输配系统、减少热损失环节、因地制宜按质用能的配置辅助系统、选择适宜的"供冷高温化和供热低温化末端系统装置",以及加强运行监测管理及维护工作。通过这些对这些关键要素的把握,可以改善和提供土壤源热泵的能效情况,具有现实指导价值和意义。     

地源热泵系统运行中土壤温度场变化特性的实例分析

对某一地源热泵系统的实测土壤温度场数据进行了初步分析,总结了冬季、夏季及过渡季工况下土壤温度场的变化特点及其影响因素。指出地源热泵系统运行过程中的地下能量堆积问题是一个长期效应,记录分析土壤温度场的长期变化趋势对于调控地源热泵系统的运行状态具有积极的指导作用,有利于保证系统的长期可靠性和节能性。     

Exergoeconomic analysis of the Gonen geothermal district heating system for buildings

This paper presents an application of an exergoeconomic model, through exergy and cost accounting analyses, to the Gonen geothermal district heating system (GDHS) in Balikesir, Turkey for the entire system and its components. This exergoeconomic model is used to reveal the cost formation process and the productive interaction between components. The exergy destructions in the overall Gonen GDHS are quantified and illustrated for a reference temperature of 4 °C. The results indicate that the exergy destructions in the system occur primarily as a result of losses in the cooled geothermal water injected back into the reservoir, pumps, heat exchangers, and pipelines. Total exergy destruction and reinjection exergy of the cooled geothermal water result in 1010 kW (accounting for 32.49%), 320.3 kW (accounting for 10%) of the total exergy input to the Gonen GDHS, respectively. Both energy and exergy efficiencies of the overall Gonen GDHS are also investigated to analyze the system performance, as these efficiencies are determined to be 42% and 50%, respectively. It is found that an increase of the load condition leads to a decrease in the overall thermal costs, which will result in more cost-effective energy systems for buildings.     

Achieving total domestic hot water production with renewable energy

Various means of producing domestic hot water (DHW) with renewable energy in zero net energy homes (ZNEH) are examined for two climates (Montréal and Los Angeles). Four alternatives are examined: (i) a regular electric hot water tank; (ii) the desuperheater of a ground-source heat pump (GSHP) with electric backup; (iii) thermal solar collectors with electric backup; and (iv) a heat pump water heater (HPWH) indirectly coupled to a space conditioning GSHP. Results show that heating DHW with thermal solar collectors with an electric backup (which is either provided by the photovoltaic (PV) panels or the grid in a ZNEH) is the best solution for a ZNEH. The second part of this paper focuses on determining what should be the respective areas of the thermal solar collectors and PV array to obtain the least expensive solution to achieve total DHW production with renewable energy.     

低密度住宅的绿色设计研究

针对低密度住宅区,分析了某项目中采用的外保温复合墙体、地源热泵系统、小区雨水收集系统等绿色技术。从建筑造价和运行费用出发,在保证良好住宅舒适度的前提下,降低建筑全寿命周期中的资源及能源的消耗量,实现了绿色建筑成本在较短时期内回收。     

Determining the optimal design of a closed loop earth to air heat exchanger for greenhouse heating by using exergoeconomics

This investigation deals with an exergoeconomic evaluation of the earth to air heat exchanger (EAHE) application for determining the optimal design greenhouse heating in Izmir, Turkey. The exergy destructions in the system are quantified and illustrated using tables for a reference temperature of 6 °C. The results indicate that the exergy destructions in the system occur primarily as a result of blower losses and heat exchanger losses. These average losses account for 85% and 4.5%, respectively. Both COP and exergy efficiency of the overall system was investigated to analyze and improve the systems performance. The average COP and exergetic efficiency were determined to be 10.51 and 89.25%, respectively. The results may provide useful insights into the relations between thermodynamics and economics for the EAHE heating systems.     

Modelling the carbon-saving performance of domestic ground-source heat pumps

A ground-source heat pump (GSHP) model is formulated and used to estimate the potential of a domestic GSHP as a carbon-saving technology (compared to a conventional gas boiler) with actual thermal data for a dwelling in the UK. The model shows good agreement with current sizing guidelines but shows possible barriers to the carbon-savings (and running cost savings) of GSHPs. This includes an analysis of output temperatures, system sizes and grid CO₂ intensity. The model suggests that GSHPs should be aimed towards a new-build market (rather than retrofit) due to the likely reliance on high surface area/low temperature distribution systems. Also, grid CO₂ intensity needs to be better understood when estimating the electrical consumption CO₂ emissions of GSHPs, both for current and future scenarios.     

利用温频法对空调冷热源进行经济分析及选择

以天津某五星级酒店为例,采用温频法(BIN法)和费用年值法,比较土壤源热泵对传统型电制冷、集中供热组合和吸收式直燃机3种空调系统冷热源进行经济性分析。结果表明,虽然地源热泵初期投资最大,但是年运行费用在3种方案中最低,具有很好的经济性。     

工业余热在改善冬季地源热泵系统运行中的应用

针对地源热泵系统在冬季供暖高峰期地埋管区域蓄热量不足、系统能效比降低的问题,提出了工业余热与浅层地热复合的地源热泵供热模式。结合实例进行计算分析,结果表明：在性能指标与经济性方面具有明显优势,复合式地源热泵系统是一种有效利用工业余热的方法。     

地埋管地源热泵热水供应系统运行性能的影响因素

建立了地埋管地源热泵热水供应系统实验平台,研究了环境温度、间歇/连续运行工况、管内循环液流速等对地埋管换热器换热能力的影响,并研究了地埋管换热器周围土壤温度场的变化.结果表明,地埋管地源热泵热水供应系统基本不受环境温度的影响;采用间歇运行,有利于提高地埋管换热器的换热能力;地埋管换热器平均单位井深换热量随管内循环液流速的增大而增大,但当流速增大到一定程度时,其增幅趋于平缓.     

福州住宅应用土壤源热泵的全年能耗与可行性分析

以福州地区典型的单户住宅为实例,在全年逐时建筑负荷计算的基础上,进行空气源热泵和地源热泵的全年能耗分析,并在此基础上进行两者的经济性比较。结果表明,从全年能耗比较,土壤源热泵比空气源热泵节能15%,其中夏季节能13%;冬季节能20%。尽管土壤源热泵机组的季节性能比SE-ER高于空气源热泵,但由于福州冬季室外气温较温和,夏季地温偏高,土壤源热泵的节能效果不及夏热冬冷地区明显,并且初投资回收期较长,经济可行性较差。     

浅析沈阳市地源热泵系统应用形式及发展目标

分析了沈阳市地源热泵系统中,地下水源热泵系统、再生水源热泵系统、土壤源地源热泵系统、混合式水源热泵机组与集中供热联供系统的实际应用情况以及不同系统的发展目标及投资分析     

天津市某绿色建筑暖通设计方案分析

以天津市某绿色建筑的计算负荷为基础,通过分析不同冷热源方案全寿命周期成本,确定采用地源热泵为系统的冷热源。对地源热泵系统地源侧的年吸、释热量进行计算和分析,确保系统长期运行的稳定性。结合建筑部分负荷运行时间和地源热泵机组部分负荷性能参数,对热泵机组的选型进行分析。此外,对水系统的运行策略和室内空气品质的调控性加以分析。     

安徽地源热泵应用区域的地温变化预测

通过建立浅层地温预测模型,对安徽地源热泵系统开发利用浅层地热能进行了区域性浅层地温变化模拟预测;分别预测评价了在不同的岩土体、不同的冷热负荷不平衡率、不同的地埋管深度、不同的管间距及不同管群布置方式等条件下,地源热泵系统运行时的浅层地温变化情况;提出了开发利用条件下的地温热平衡措施。