Thermo-Economic Performance of Geothermal Driven High-Temperature Flash Tank Vapor Injection Heat Pump System:A Comparison Study

Process heating constitutes a significant share of final energy consumption in the industrial sector around the world.In this paper,a high-temperature heat pump(HTHP)using flash tank vapor injection technology(FTVI)is proposed to develop low-temperature geothermal source for industrial process heating with temperature above 100°C.With heat sink output temperatures between 120°C and 150°C,the thermo-economic performance of the FTVI HTHP system using R1234ze(Z)as refrigerant is analyzed and also compared to the single-stage vapor compression(SSVC)system by employing the developed mathematical model.The coefficient of performance(COP),exergy efficiency(ηexe),net present value(NPV)and payback period(PBP)are used as performance indicators.The results show that under the typical working conditions,the COP andηexe of FTVI HTHP system are 3.00 and 59.66%,respectively,and the corresponding NPV and PBP reach 8.13×106 CNY and 4.13 years,respectively.Under the high-temperature heating conditions,the thermo-economic performance of the FTVI HTHP system is significantly better than that of the SSVC system,and the larger the temperature lift,the greater the thermo-economic advantage of the FTVI HTHP system.Additionally,the FTVI HTHP system is more capable than the SSVC system in absorbing the financial risks associated with changes of electricity price and natural gas price.

Recent Development and Application of Geothermal Heat Pump Systems in Cold-Climate Regions of the US: A Further Investigation

A Geothermal Heat Pump (GHP) system is known to have enormous potential for building energy savings and the reduction of associated greenhouse gas emissions, due to its high Coefficient Of Performance (COP). The use of a GHP system in cold-climate regions is more attractive owing to its higher COP for heating compared to conventional heating devices, such as furnaces or boilers. Many factors, however, determine the operational performance of an existing GHP system, such as control strategy, part/full-load efficiency, the age of the system, defective parts, and whether or not regular maintenance services are provided. The omitting of any of these factors in design and operation stages could have significant impacts on the normal operation of GHP systems. Therefore, the objectives of this paper are to further investigate and study the existing GHP systems currently used in buildings located in cold-climate regions of the US, in terms of system operational performance, potential energy and energy cost savings, system cost information, the reasons for installing geothermal systems, current operating difficulties, and owner satisfaction to date. After the comprehensive investigation and in-depth analysis of 24 buildings, the results indicate that for these buildings, about 75% of the building owners are very satisfied with their GHP systems in terms of noise, cost, and indoor comfort. About 71% of the investigated GHP systems have not had serious operating difficulties, and about 85% of the respondents (building owners) would suggest this type of system to other people. Compared to the national median of energy use and energy cost of typical buildings of the same type nationwide, the overall performance of the actual GHP systems used in the cold-climate regions is slightly better, i.e. about 7.2% energy savings and 6.1% energy cost savings on average.

Energy savings and CO_2 emission reduction by using geothermal heat pumps

The renewable energy will play significant role in the world primary energy consumption in the future. Geothermal energy is immense with 5 000 EJ/a of technical potential, and geothermal heat pumps (GHPs) are one of the fastest growing applications of renewable energy in the world with annual increases of 10 % and much faster in China. With high coefficient of performance (COP) up to 6, GHPs make efficiency of primary energy more than 240 % with assumed a 40 % of electricity generation efficiency, which means energy savings and CO2 emission reduction. In this paper,the geothermal resources and its utilization are talked about, and GHPs technology was introduced. Due to its high efficiency, there will be energy savings by using GHPs. There is also CO2 emission reduction because of using geothermal heat pumps, which is analyzed in the end.

Geochemical Assessments and Potential Energy Sources Evaluations Based on Oil Shale and Geothermal Resource in Wadi Al-Shallala—North Jordan

Oil shale deposit is considered as one of the fossil fuel sources in Jordan. Despite that, the needs of renewable energy resources become a must in Jordan. Wadi Al-Shallala oil shale is investigated in this work for geochemical, petrographic features and hydrocarbon potential as a conventional energy resource. Various petrographic and geochemical techniques were applied. Oil shale resource potential is evaluated for cooling and heating Sal village houses. Geothermal heat pumps, as renewable energy resource in the study area, were simulated for comparison purposes. Results show that Calcite is the main mineral component of oil shale. Magnesite, Ferrisilicate and Zaherite are exhibited in the studied samples. Other trace elements of Zinc, Cobalt and Molybdenum were presented, too. Calcium oxide of 41.01% and Silicon oxide of 12.4% are the main oxides reflected in this oil shale. Petrographic features of the analyzed oil shale found that the primary mineral constituent is micritic calcite, while the secondary minerals include carbonate mud and opaque minerals. Furthermore, it’s found that total organic carbon averages 3.33% while the total carbon content averages 20.6%. ModerateTOCvalues suggest that Wadi Al-Shallala oil shale has a good source rock potential. Even though nitrogen and sulfur are of low contents in Wadi Al-Shallala oil shale, direct combustion of the reserve for electricity generating will increase CO2 emissions by 2.71 Million m3. Two systems were simulated to cover Sal village cooling and heating demands. The conventional system is compared with geothermal heat pumps. Geothermal heat pumps are found to save 60% of electricity consumption in heating and 50% in cooling systems. The environmental benefits for geothermal system implementation will be a reduction in energy consumption as electricity. The savings in fuel oil will be about 9.35 Million barrels. While the reduction of CO2 emissions will drop to 1.5 Million m3. Results suggest that geothermal heat pumps are the best for satisfying cooling and heating needs in Sal village near Wadi Al-Shallala.

Scanning PIV Method and Its Application to the Calorimetry of Ground Source Heat Pump Systems

Ground source heat pump (GSHP) systems that use a direct expansion method?are expected to have higher energy-saving performance than conventional air conditioning systems. The heat transfer rate is evaluated by measuring the temperature, humidity, and flow rate at the indoor unit of the GSHP system. However, it is difficult to evaluate the flow rate by measuring the flow velocity distribution at the outlet of the indoor unit. In this study, the Scanning PIV method is proposed to improve the accuracy of the flow rate measured by hot wire anemometers. The flow rates obtained by the hot wire anemometers were 60.6% and 15.2% higher than those from the PIV method during cooling and heating operation, respectively. Compensation formulas are generated using the results of the Scanning PIV method to correct the measurements from the hot wire anemometers. This compensation formula reduced the error generated by the nonuniformity of velocity distribution. It was 60.6% to 2.5% in cooling operation and 15.2% to 0.9% in heating operation, respectively. The compensation formulas were applied to evaluate the performance of a GSHP system, and the result shows that the GSHP system provides improved performance stability compared to traditional air conditioning systems.

Application of Ground Source Heat Pump to a Supermarket in Portugal

The objective of the present paper is to describe a technical and economical visibility study of the application of ground source heat pumps （GSHP） in a supermarket in Portugal. The study was developed under the European project ＂Integration of Geothermal Energy Into Industrial Application - IGEIA＂, project number EIE 06/001, supported by the Intelligent Energy for Europe, IEE, of EACI, European Commission. In general for supermarkets installed in single buildings, the building envelope has higher rates of envelope areas per indoor air volume. In Portugal this fact produces high need of heating during the winter season and high cooling needs during the summer season. Inside the building there are strong internal heat loads produced by high densities of lights and equipments. However these internal loads are not distributed uniformly. There are some areas with high production of heat but there are others with production of cooling. Therefore the acclimatization of this kind of buildings is not so easy and the balance of heating and cooling needs is depending of different parameters which should be well evaluated. The energy consummation of the cold display cases and deep freezers in market area and storage is also very high. The different energy needs could be studied in an integrated way and could be partially satisfied by geothermal energy using ground source heat pumps. At the same time the boreholes could be used as an energy reservoir increasing the efficiency of whole system. Four different climatic zones in Portugal were selected, （north coast, interior north, south coast and interior south） using the same system. The results of the study show that the all energy needs can by partially satisfied by geothermal energy but they need to be integrated to increase the global efficiency. The paper shows that the geothermal energy can be an attractive application for the supermarkets in Portugal if the energy solution is studied in an integrated way and if it is also considered as a cost the emissions of CO2 avoid by the new system.

Performance analysis of deep borehole heat exchangers for decarbonization of heating systems

Meeting the climate change mitigation targets will require a substantial shift from fossil to clean fuels in the heating sector.Heat pumps with deep borehole exchangers are a promising solution to reduce emissions.Here the thermal behavior of deep borehole exchangers(DBHEs)ranging from 1 to 2 km was analyzed for various heat flow profiles.A strong correlation between thermal energy extraction and power output from DBHEs was found,also influenced by the heating profile employed.Longer operating time over the year typically resulted in higher energy production,while shorter one yielded higher average thermal power output,highlighting the importance of the choice of heating strategy and system design for optimal performance of DBHEs.Short breaks in operation for regenerating the borehole,for example,with waste heat,proved to be favorable for the performance yielding an overall heat output close to the same as with continuous extraction of heat.The results demonstrate the usefulness of deep boreholes for dense urban areas with less available space.As the heat production from a single DBHE in Finnish conditions ranges from half up to even a few GWh a year,the technology is best suitable for larger heat loads.

Arrangement Strategy of Ground Heat Exchanger with Groundwater

The orientation strategy of side pipe and the heat transfer performance of six ground heat exchangers(GHEs) were optimized by numerical simulation,with soil being treated as a porous medium.An experiment on the heat transfer of four GHEs was carried out in 2010.Results indicate that the velocity field is disturbed by GHEs.The optimal orientation strategy of side pipe is that the upward pipe is located upstream and the downward pipe downstream.The space between GHEs should be appropriately adjusted,depending on the direction and flow velocity.Groups of GHEs should be installed perpendicular to the mainstream in a single row,but if the acreage does not meet the requirements,GHEs should be installed in staggered multiple rows.Fewer GHEs parallel to the mainstream strengthen the heat transfer.Moreover,numerical results agree well with the test data,with the maximum relative error being less than 7.7%.

区域尺度地埋管地源热泵与能源地下结构开采浅层地热能评价综述

随着浅层地热能的大规模开发利用,针对地埋管地源热泵和能源地下结构的研究正由单个、单体尺度逐渐转向区域尺度。相较于地埋管地源热泵,能源地下结构占地面积小、成本低,在大规模城市建设及地下空间开发中具有良好的优势。从热物性参数和地下城市热岛效应两方面总结浅层地热能理论潜力现有研究成果,简述浅层地热能的开发形式,重点针对区域尺度地埋管地源热泵与能源地下结构的适应性评价进行系统综述,从适宜性分区、热交换潜力、满足建筑物能源需求效果三方面建立相应的区域尺度能源地下结构评价体系,以我国山东临朐县和德国巴登-符腾堡州地埋管地源热泵及我国南京大学仙林校区能量桩的区域性研究为案例进行深入分析,归纳当前研究中存在的问题,并对区域尺度能源地下结构的下一步研究进行展望。

大型地埋管群地源热泵三维传热-渗流耦合模拟

为确定地下水渗流对大尺度、多分支埋管集群地源热泵系统换热区温度场和换热特性的影响,基于上海天文馆880个地埋管地源热泵场地,建立考虑地下水渗流和地质分层的三维传热-渗流耦合模型,并利用现场热响应试验对模型进行验证。结果表明:渗流作用引起管群内和支管群之间沿地下水流动方向发生温度干扰,89.5~120.3 m埋深范围内的温度干扰现象相对明显;地下水渗流有利于提高管群的换热总量,缩小夏季和冬季工况的换热量差距;换热量增加百分比随水力梯度的增加而增大,两者呈对数函数关系,当水力梯度大于0.005时,换热量增加百分比趋于平稳。

基于改进粒子群算法的中深层地源热泵供暖系统运行优化

构建变工况运行且包含蓄热装置的中深层地源热泵供暖系统,基于改进粒子群算法,分别以运行费用、系统COP和地热能利用系数为目标函数对系统运行进行优化,并对优化结果进行比较和分析。结果表明:对应目标函数优化后的运行费用、系统COP和地热能利用系数分别为279.27元、6.4420和0.8527。以系统COP为目标函数的优化效果与运行费用相反,而与地热能利用系数相近。

地埋管换热系统改造项目关键技术节点施工工艺研究

天津某管业公司建筑原采用常压燃气热水锅炉供热和分体式空调供冷,现拟以浅层地热能为基础能源对原供热制冷系统进行改造,施工前首先通过现场岩土热响应试验、地下管线探测等查明施工场地岩土体结构和换热能力,掌握地下综合管线的分布,并对建筑单位冷热负荷指标校正。重点阐述地埋管换热系统施工过程的关键技术节点,即竖直换热孔钻进、下管、回填及水平管线连接等,为类似改造项目提供参考。

地热驱动的双温热力站系统及其变工况性能

高温地热能是宝贵的可再生能源供热资源,降低地热水回水温度是发挥地热供热潜力、扩大供热面积的重要途径。鉴于既有建筑普遍采用散热器等高温供热末端,而新建建筑多采用地暖等低温供热末端,二者的需求供水温度不同,对此提出了单吸收式热泵+双换热器的地热能驱动双温热力站系统,以制取高、低温末端用双温热水,并尽可能降低地热水回灌温度。模拟分析表明:在地热出水为100℃,二次网高、低温末端供热量相同且供水温度分别为50℃和35℃条件下设计的双温热力站,可将地热水回水温度降至20.1℃,相比于采用2个换热器串联的热力站,其地热水的回水温度可降低14.9℃、流量可降低18.6%,系统的COP提升11%,具有显著的节能优势。变工况分析表明:低温供热末端的应用有利于进一步降低地热水回灌水温,增加向末端用户的供热量,并提高双温热力站系统的COP。

超长重力热管联合热泵的地热利用系统热力经济性分析

深层地热资源储量巨大,采用超长重力热管取热技术对深层地热资源进行开采,将其与热泵系统联合为用户供热是一种高效利用深层地热资源的方法。针对如何调节不同参数下超长重力热管与热泵联合运行以期获得最佳热力经济性的问题,建立了系统热力经济性模型,研究了热泵系统蒸发温度、超长重力热管热阻、井深、地温梯度以及蒸发器面积不同的情况下系统热力经济性变化规律。结果表明存在一个最佳蒸发温度使供热成本最低,如在地温梯度30℃/km、井深3 000 m的条件下,最佳蒸发温度为-2℃;超长重力热管热阻越小或地温梯度越大时可实现供热成本越低且最佳蒸发温度越高;存在最佳的井深和蒸发器面积使得供热成本最低。研究结果可为优化超长重力热管在开采深层地热联合热泵系统性能方面提供理论指导。

中深层套管式地埋管地源热泵系统能效分析

中深层套管式地埋管地源热泵系统的能效受多种因素影响,为保证其高效运行,对其影响因素进行研究尤为重要。本文建立了中深层套管式地埋管地源热泵系统换热器传热模型,采用工程实测数据验证该模型的准确性。基于该模型,量化了一个供暖期内多种因素对系统能效的影响。结果表明:进口水温和岩土导热系数对系统能效具有重要影响,回填材料导热系数对其影响较小;增大循环流量会提高取热功率,但系统能效也随之降低,当循环流量由8.33 kg/s增大至10.56 kg/s时,取热功率提升4.95%,能效下降1.23%;增大外管管径、岩土和回填材料的导热系数能够提升系统能效,但达到一定数值后,对能效提升效果不显著。本研究对中深层套管式地埋管地源热泵系统长期稳定运行及能效提升具有参考意义。

岩土源热泵在喀斯特地区的应用问题及对策

地源热泵目前的主要形式是岩土源热泵.为厘清系统在喀斯特地区应用时影响运行效果的因素,进行了换热试验和工程调研,认为不利的地层岩性和水文地质条件会在一定程度上制约系统的可持续开发利用,空气潜孔锤钻井技术与施工中存在的问题也会使系统不能正常运行.提出了加强基础地质和水文地质调查、地球物理勘察、钻探技术提升及过程管理等建议和对策.

面向清洁电力消纳的中深层地埋管热泵蓄能系统设计方法研究

电驱动热泵技术在为建筑提供清洁冷热的同时,也成为了与电网协同、消纳清洁电力的关键环节。本文以电驱动热泵技术为核心,冬季供热采用中深层地埋管提供高品位低温热源,夏季供冷结合冷却塔技术构建高效冷热供应系统。在此基础上结合用户侧蓄能技术,实现日间冷热蓄存,同时以充分消纳本场光伏发电及市政清洁电力为目标提出了系统的设计方法与运行控制策略。随后以我国某大型公共建筑为例开展了定量分析,以明确其实际节能减排效果。

温室大棚地热能与空气能多能互补能源配比研究

“双碳”目标下采用可再生能源解决温室大棚的供冷、供暖,构建安全、绿色、智慧、高效的能源系统成为了温室大棚的发展方向。近年来,中深层地热能、浅层地热能、空气能在温室大棚供热中的应用得到快速发展。以河南省周口市扶沟县某农业产业园为例,结合区域地热资源情况,提出了中深层地热+地源热泵+水源热泵、中深层地热+地源热泵+空气源热泵、地源热泵+空气源热泵、地源热泵+水源热泵4种可再生能源配比方案。结果表明:地源热泵+水源热泵投资最高,地源热泵运行费用是中深层地热的2.01倍,空气源热泵运行费用是水源热泵1.95倍,地源热泵运行费用与水源热泵相相近。能源利用优先级排序为中深层地热能>地源热泵>水源热泵>空气源热泵,采用中深层地热+地源热泵+水源热泵方案为最优的能源搭配方式。

PV/T耦合中深层地源热泵供暖系统运行特性研究

为解决中深层地源热泵系统(GSHP)地温衰减的问题,以邯郸市某民用节能建筑为研究对象,基于TRNSYS建立一种PV/T耦合中深层地源热泵系统(PV/T-GSHP),并与GSHP系统对比,模拟分析运行20 a PV/T-GSHP系统运行特性。探究PV/T组件的相关参数对土壤平均温度的影响。最后,将PV/T-GSHP系统与其他系统进行能耗对比。研究结果表明:与GSHP系统相比,PV/T-GSHP系统机组COP从6.44提高到6.81,但由于增加了泵功,系统COP降到2.38,但考虑发电量,平均每年可获得10015.831元收益;相似结构建筑PV/T组件屋顶铺设占比越大,集热泵流量越小,土壤平均温升越快;不考虑发电量时,PV/T-GSHP系统比燃气锅炉系统能耗高8.46%,与燃煤锅炉和电锅炉系统相比,分别可节约11.04%和48.55%的能耗;综合发电量时,20 a实际获得的发电量收益折合成燃煤量为210.05 t。