Analysis of the energy performance of a ground source heat pump system after five years of operation

GeoCool plant was the result of a EU project whose main purpose was to adapt ground coupled heat pump technology to cooling dominated areas. The execution of this experimental plant was completed at the end of year 2004, starting on February 2005 the regular operation of the air conditioning system. Since then, GeoCool facility has been monitored by a network of sensors characterizing its most relevant parameters. Several aspects of the performance and behaviour of the system during its first operational year were presented on a previous paper. This paper presents the energy performance measurements of GeoCool ground coupled heat pump system acquired during five years of operation as well as the evolution of the return water temperature from the ground as a representative of the ground temperature. The analysis of the experimental results shows that the system energy performance is maintained through the years with no appreciable impact on ground thermal response.     

Three-years operation experience of a ground source heat pump system in Northern Greece

The paper presents the basic parameters and the energy flows of a ground source heat pump system (GSHP) used for air conditioning the New City Hall of Pylaia (Thessaloniki area—Northern Greece). The building is a typical public one, with an air-conditioned area of 1350 m². The ground source heat pump installation is the largest in Greece, and its operation is monitored with the aid of a DAQ system. The energy flows presented in the paper are based on DAQ recordings of the first 3 years of system's operation. It is proved that the energy demand of the system is significantly lower, compared to that of conventional heating and cooling systems. The seasonal COP of the system has not yet been stabilized, gradually increasing, as it is expected due to the operation of the ground heat exchanger.     

The influence of the borehole short-time response on ground source heat pump system efficiency

Ground coupled heat pump systems can offer high energy efficiency for heating and cooling of buildings.The coupling of the ground loop with system and building represents a complex system and system performances can vary over long periods, in the range of 10-15 years due to the charge or discharge of the ground loop. In order to correctly concept, size and optimise these systems, numerical simulation is a perfect tool.The assessment of the global performance of such systems through simulation relies on several parameters, from the physical model validity to the operating conditions and control of the system. Typically, a GCHP system is simulated with a 1-h step. Transient phenomena inside the borehole are often neglected since ground models are mainly developed to characterise long term phenomena. However, detailed system simulations considering a realistic control of the system require much smaller time steps. In these cases, the validity of simulation models has to be verified.This paper proposes a hybrid approach combining experiments and simulation to highlight and quantify the impact of borehole short-time response on the system efficiency and system operation. First, a comparison between steady state and transient models as well as measurement is carried out. It reveals significant influence of dynamic effects inside the borehole. The comparison is then extended a parametric study with annual simulations for different European climates.     

Energy and exergy analysis of a ground-coupled heat pump system with two horizontal ground heat exchangers

In this paper we investigate of energetic and exergetic efficiencies of ground-coupled heat pump (GCHP) system as a function of depth trenches for heating season. The horizontal ground heat exchangers (HGHEs) were used and it were buried with in 1 m (HGHE1) and 2 m (HGHE2) depth trenches. The energy efficiency of GCHP systems are obtained to 2.5 and 2.8, respectively, while the exergetic efficiencies of the overall system are found to be 53.1% and 56.3%, respectively, for HGHE1 and HGHE2. The irreversibility of HGHE2 is less than of the HGHE1 as about 2.0%. The results show that the energetic and exergetic efficiencies of the system increase when increasing the heat source (ground) temperature for heating season. And the end of this study, we deal with the effects of varying reference environment temperature on the exergy efficiencies of HGHE1 and HGHE2. The results show that increasing reference environment temperature decreases the exergy efficiency in both HGHE1 and HGHE2.     

Verification of energy efficiency of district heating and cooling system by simulation considering design and operation parameters

This paper aims to verify the advantages of district heating and cooling (DHC) systems in terms of energy efficiency. From the measurement data, the parameters that characterize the energy efficiency of a heating/cooling plant are identified for DHC and an individual building. A simulation model that considers the difference in these parameters is developed. This model examines both the advantages and disadvantages of DHC systems and the effect of each parameter. The results show that the energy efficiency for cooling in DHC systems is superior to that in the case of individual cooling systems because of the “concentration effect” and “grade of operation”.     

燃气冷热电三联供与地源热泵的联合应用

以中新天津生态城能源站为例,分析了联合系统一次能源效率、燃料节约率、经济性、影响因素的敏感性和环保性等,结果表明,冷热电三联供系统的能源利用率可达88.9%,联合系统的能源消耗比常规系统少18.5%,冷热电三联供系统的初投资在6年内可以收回。     

Development of a numerical model to predict heat exchange rates for a ground-source heat pump system

Ground-source heat pump (GSHP) systems can achieve a higher coefficient of performance than conventional air-source heat pump (ASHP) systems. For the design of a GSHP system, it is necessary to accurately predict the heat extraction and injection rates of the heat exchanger. Many models that combine ground heat conduction and heat exchangers have been proposed to predict heat extraction/injection rates from/into the ground in the research field of heating, ventilation and air-conditioning systems. However, most analysis models are inaccurate in their predictions for long periods because they are based on a thermal conduction model using a cylindrical coordinate model or an equivalent diameter model. In this paper, a numerical model that combines a heat transport model with ground water flow and a heat exchanger model with an exact shape is developed. Furthermore, a method for estimating soil properties based on ground investigations is proposed. Comparison between experimental results and numerical analysis based on the model developed above was conducted under the conditions of an experiment from 2004. The analytical results agreed well with the experimental results. Finally, the proposed model was used to predict the heat exchange rate for an actual office building in Japan.     

建设工程招投标阶段造价控制探讨

招投标是建立公开、公平、公正和诚实信用的市场秩序的有效手段,也是开展资源节约型经济活动,实现资源配置,提高资产投资效益的重要途径。本文即通过分析建设工程招投标的特点及招投标阶段对工程造价的影响,提出在招投标阶段涩制工程造价应采取的措施,从而达到有效控制工程造价的目的。     

Numerical and experimental analysis of a horizontal ground-coupled heat pump system

The main objective of this work is to evaluate a heat pump system using the ground as a source of heat. A ground-coupled heat pump (GCHP) system has been installed and tested at the test room, University of Firat, Elazig, Turkey. Results obtained during experimental testing are presented and discussed here. The coefficient of performance (COP_sys) of the GCHP system is determined from the measured data. A numerical model of heat transfer in the ground was developed for determining the temperature distribution in the vicinity of the pipe. The finite difference approximation is used for numerical analysis. It is observed that the numerical results agree with the experimental results.     

地源热泵及地下蓄能系统的实验研究

采用系统能量平衡结合热传导方程建立二维温度场模型求解地下蓄能系统埋管换热器的全年动态传热特性。介绍了计算地下温度场的分布情况、单位埋管深度换热量、平均传热系数、进出地下埋管的水温和埋管换热器面积的方法。     

地源热泵不同地源换热器的传热性能比较

本文针对地源热泵的核心技术问题,介绍了对两种典型地源换热器的散热试验研究:粉质粘土中的垂直单U管、地表水中的水平单U管。研究发现,两种换热器的传热性能差别很大。从开始试验到循环水温度稳定所需要的过渡时间上,地表水换热器比粉质粘土埋管型换热器要快得多。从传热能力来看,地表水换热器的单位管长换热量比粉质粘土垂直单U管要大。     

Verification of the energy-saving effect of the district heating and cooling system—Simulation of an electric-driven heat pump system

A district heating and cooling system (DHC) is expected to be a promising energy-saving measure for high-density business areas in Japan. However, it has not been verified what advantages of the DHC are important for energy conservation. The clarification of this issue is supposed to contribute to improving the energy efficiency of the DHC.     

Experience on the application of a ground source heat pump system in an archives building

A ground source heat pump (GSHP) system was designed and constructed in Minhang archives of Shanghai. As a demonstration project, it is the first archives to use a GSHP system in China. The system consists of two heat pumps with the rated cooling capacity of 500 kW for each and 280 boreholes with 80 m in depth. In the cooling mode, the heat extraction from the condenser of the heat pump was divided: part of it was rejected to the soil while the rest was used to reheat the air in air handling units. The GSHP system has continuously run for nearly two years. It was shown that the indoor thermal environment met the “Archives Design Code” issued by China national archives. Compared with an air source heat pump system which is widely used in archives buildings, the operating cost of the GSHP system is reduced by 55.8% and the payback time is about two years. Owing to its great potential in energy conservation, such kind of GSHP system is testified to be applicable to the air-conditioning systems of the archives buildings. Besides, the applications of GSHP systems corresponding to different climatic zones of China were analyzed.     

土壤源热泵系统建模及运行参数优化

地埋管换热器的优越性能在当今社会越来越受到重视,在供暖、烘干、能源互补利用方面有广阔的前景。本文基于TRNSYS软件建立上海某建筑的模型系统设计,并介绍了建筑负荷模拟的过程、冷却塔串联和并联方式的模拟计算。针对上海的天气情况、土壤源温度的变化作为原始变量进行了模拟分析,比较得出性能好方案,最后进行较好方案的继续优化。     

Ground source heat pump systems: current status

Geothermal energy is critical to achieving more sustainable and environmentally friendly energy usage. Geothermal energy and the availability of the technology, Ground Source Heat Pump (GSHP) systems are becoming increasingly popular for heating and cooling of buildings. GSHP installations in different countries are increasing at a rate greater than 25–60%. The GSHPs produce near zero emissions rates of greenhouse gases (GHGs).     

混合式地源热泵系统优化设计

介绍了几个文献中关于冷却塔-土壤源热泵系统的设计方法,提出了笔者研究的设备选型方法。结合工程设计,介绍了混合式地源热泵系统的几种设计方案,并进行了能耗模拟,以探讨最优方案。     

污水源热泵系统和污水冷热能利用前景分析

分析了污水热源／热汇的特点，介绍了以未处理污水作为热源／热汇和以二级出水或中水作为热源／热汇的污水源热泵系统，分析了污水源热泵系统的技术经济性和其应用潜力，介绍了国内外的应用情况，并对其推广使用需要解决的问题进行了探讨。     

Optimal design of district heating and cooling pipe network of seawater-source heat pump

The district heating and cooling (DHC) system of a seawater-source heat pump is large system engineering. The investments and the operational cost of DHC pipe network are higher than a tradition system. Traditional design methods only satisfy the needs of the technology but dissatisfy the needs of the economy, which not only waste a mass of money but also bring problems to the operation, the maintenance and the management. So we build a least-annualized-cost global optimal mathematic model that comprises all constrict conditions. Furthermore, this model considers the variety of heating load and cooling load, the operational adjustment in different periods of the year. Genetic algorithm (GA) is used to obtain the optimal combinations of discrete diameters. Some operators of GA are selected to reduce the calculation time and obtain good calculation accuracy. This optimal method is used to the design of the DHC network of Xinghai Bay commercial district which is a real engineering. The design optimization can avoid the matter of the hydraulic unbalance of the system, enhance the running efficiency and greatly reduce the annualized-cost comparing with the traditional design method.     

Field performance measurements of a heat pump desiccant unit in heating and humidification mode

In this study, a novel self-regenerating electric vapor compression heat pump desiccant (HPD) unit operated in the heating and humidification mode during the winter season is introduced. The HPD unit was installed in an office suite for the field test. The performance of the HPD unit and the provided indoor conditions were measured over a wide range of operating conditions. The target indoor humidity ratio was set to 4.4 g/kg, which is the minimum required indoor humidity ratio for a comfortable indoor environment indicated in the ASHRAE winter thermal comfort zone. The seasonal comparison revealed that even though 77.7% of all outdoor humidity ratio data was lower than 4.4 g/kg, 78.2% and 85.8% of all the indoor humidity ratio data of each room were found to be higher than 4.4 g/kg. In addition, due to the significant sensible capacity of the HPD unit, the indoor temperatures could be maintained within 20-25 °C. These results prove that the HPD unit not only properly humidifies the indoors without using any additional water source, like the conventional humidifier, but also helps to keep the indoor temperature at the desired temperature levels.     

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。