Performance and control of domestic ground-source heat pumps in retrofit installations

Heat pumps are an essential technology for decarbonisation of domestic heating in the UK. This paper reports on the performance in use of a group of ground-source heat pumps, and in common with other UK studies finds that the seasonal performance is not as good as that reported in trials from continental Europe and that the system controls are unsatisfactory. Control improvements are investigated via a model of the dwelling and heat pump as a combined system, from which the thermal time constant of the building is identified as a critical factor that needs to be considered in retrofit projects incorporating heat pumps. The validity of the conventional practice (and advice from installers to users) of allowing heat pumps to run continuously is tested and bounded. Techniques for improving control are outlined and reasons for the poorer performance in the UK examined with the conclusion that heat pumps need to be better matched in capacity and control to the size and thermal characteristics of UK dwellings. Implementation of these findings by heat pump manufacturers and installers could promote a more rapid transition to renewable heat both in the UK and internationally wherever similar housing stocks and climates exist.     

Experimental performance analysis of a solar assisted ground-source heat pump greenhouse heating system

Ground-source heat pumps (GSHPs), also known as geothermal heat pumps (GHPs), are recognized to be outstanding heating, cooling and water heating systems, and have been used since 1998 in the Turkish market. Greenhouses also have important economical potential in Turkey’s agricultural sector. In addition to solar energy gain, greenhouses should be heated during nights and cold days. In order to establish optimum growth conditions in greenhouses, renewable energy sources should be utilized as much as possible. It is expected that effective use of heat pumps with a suitable technology in the modern greenhouses will play a leading role in Turkey in the foreseeable future.The main objective of the present study is to investigate to the performance characteristics of a solar assisted ground-source heat pump greenhouse heating system (SAGSHPGHS) with a 50 m vertical 1 × 1/4 in. nominal diameter U-bend ground heat exchanger using exergy analysis method. This system was designed and constructed in Solar Energy Institute of Ege University, Izmir, Turkey. The exergy transports between the components and the destructions in each of the components of the SAGSHPGHS are determined for the average measured parameters obtained from the experimental results. Exergetic efficiencies of the system components are determined in an attempt to assess their individual performances and the potential for improvements is also presented. The heating coefficient of performances of the ground-source heat pump unit and the overall system are obtained to be 2.64 and 2.38, respectively, while the exergetic efficiency of the overall system is found to be 67.7%.     

Building Mass,Plant Size and C.O.P.

Using the HOUSE computer program of the UK Electricity Council Research Centre, calculations have been made, as described here, of the effective performance of a house heating system, in this instance specifically related to a heat pump. The results show that the effective coefficient of performance of a heat pump is greater in a ‘heavy’ building than in a ‘light’ one, and is also greater when the capacity of the heat pump is relatively small. Measures to reduce standby operation of the heat pump are shown to be particularly beneficial in improving a heat pump's effective c.o.p.     

宾馆热泵热水系统的试验研究

探讨了适用于宾馆的热泵热水系统的加热方式及水箱布置形式。结合工程实例,对不同卫生热水温度下的热泵制热性能系数及不同水箱布置形式的热泵热水系统耗电量进行了试验研究。在宾馆使用热泵制备卫生热水可行。在选择合适的冷凝器卫生热水进出口温差以提高热泵制热性能系数时,应优化水箱布置形式,减少循环泵数量及其能耗,以提高热泵热水系统的制热性能系数。     

风冷热泵系统在我国北方地区的应用

分析了我国北方地区面临的采暖问题,探讨了风冷热泵的低温性能,通过对三种风冷热泵机组低温性能的测试,指出采用地板采暖的优越性,同时指出风冷热泵结合地板采暖将是替代燃煤采暖的最经济的清洁采暖系统。     

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.     

Policy implications for the performance gap of low-carbon building technologies

ABSTRACT

It is widely recognized that the actual impact of low-carbon technologies is often lower than predicted by models alone, a phenomenon which has been coined the ‘performance gap’. Despite this awareness, in many instances estimates of both energy savings and renewable energy generation in domestic buildings continue to rely on engineering models and building energy simulations rather than approaches that are based on measured parameters. Much of the existing literature on the performance gap focuses on energy efficiency and is concerned with the quantification of the scale of the performance gap. This paper adds to this body of evidence by drawing retrospectively on a range of grey literature evaluations of low-carbon technologies (including energy-efficiency measures, renewable heat and renewable electricity) in the UK household sector. The focus is on not only the quantification of the performance gap but also the qualitative factors often overlooked, such as installation issues or installer/user behaviour. Recommended policy changes include the development of evaluation standards, the experimentation with pay-for-performance programmes, ensuring that installation standards for low-carbon technologies are being enforced, and taking reasonable steps to ensuring that end users can use any new technology effectively.     

What kind of expertise is needed for low energy construction?

The construction industry is responsible for 40% of European Union (EU) end-use emissions but addressing this is problematic, as evident from the performance gap between design intention and on-site energy performance. There is a lack of the expertise needed for low energy construction (LEC) in the UK as the complex work processes involved require ‘energy literacy’ of all construction occupations, high qualification levels, broad occupational profiles, integrated teamworking, and good communication. This research identifies the obstacles to meeting these requirements, the nature of the expertise needed to break down occupational divisions and bridge those interfaces where the main heat losses occur, and the transition pathway implied. Obstacles include a decline in the level, breadth and quality of construction vocational education and training (VET), the lack of a learning infrastructure on sites, and a fragmented employment structure. To overcome these and develop enhanced understanding of LEC requires a transformation of the existing structure of VET provision and construction employment and a new curriculum based on a broader concept of agency and backed by rigorous enforcement of standards. This can be achieved through a radical transition pathway rather than market-based solutions to a low carbon future for the construction sector.     

Fundamental optimal relation of a generalised irreversible quantum Carnot heat pump with harmonic oscillators

An irreversible quantum Carnot heat pump model working with many non-interacting harmonic oscillator systems is established in this paper. The quantum heat pump cycle is composed of two isothermal processes and two irreversible adiabatic processes. The irreversibilities of heat resistance, internal friction and bypass heat leakage are considered in the model. Based on the quantum master equation, semi-group approach and finite time thermodynamics (FTT), the cycle period, heating load and coefficient of performance (COP) of the quantum Carnot heat pump are derived, and detailed numerical examples are provided. At high temperature limit, the fundamental optimal relations between the heating load and COP of the quantum heat pump are deduced and analysed by using numerical examples. The effects of internal friction and bypass heat leakage on the optimal performance of the quantum heat pump are discussed in detail. The endoreversible, frictionless and without bypass heat leakage cases are discussed. The obtained results are general to the performance optimisation of quantum Carnot heat pumps and can provide some guidelines for optimal design of real quantum heat pumps.     

Analysis of retrofit air source heat pump performance: Results from detailed simulations and comparison to field trial data

In the UK, gas boilers are the predominant energy source for heating in housing, due primarily to the ready availability of natural gas. The take-up of heat pumps has lagged far behind Europe and North America. However, with the development of standards for low and zero-carbon housing, gas price rises and the depletion of the UK's natural gas reserves, interest in heat pump technology is growing. Heat pumps, particularly air source heat pumps (ASHPs), have the potential to be a direct, low-carbon replacement for gas boiler systems in housing.In this paper, monitored data and simulations were used to assess the performance of an ASHP when retrofitted into a dwelling. This required the development and calibration of a model of an ASHP device and its integration into a whole-building, dynamic simulation tool. The predictions of the whole-building model were compared to field trial data, indicating that it provided a suitable test bed for energy performance assessment. Annual simulations indicated that the ASHP produced 12% less carbon that an equivalent condensing gas boiler system, but was around 10% more expensive to run. However, the proposed UK renewable heat incentive transforms this situation, with income from ASHP heat generation exceeding the fuel costs.     

单热源枝状分布式水泵供热系统的故障工况分析

分析了该系统中某用户加压泵发生故障时,其支路的处理措施,以及为保持其他用户支路流量不变,热源和其他用户支路的水泵或阀门需做出的调整;热源循环水泵发生故障时,供热系统实现故障工况限额供热的可行性,以及用户加压泵的性能曲线和零压差点位置对故障工况限额供热能力的影响.给出了用户加压泵的选型原则及热源循环水泵是否配置备用泵的依据.     

空气源热泵冷热水机组在寒冷地区应用的分析

针对空气源热泵冷热水机组在寒冷地区冬季使用时结霜、热效率低等问题,提出一种双级热泵系统,即由空气源热泵冷热水机组提供10-20℃温水,作为水源热泵的低位热源,组成水源热泵供热系统,分析了这种系统的技术经济性,认为该系统是可行的,具有节能和环保意义。     

地源热泵--建筑节能新技术

在建筑供热空调中采用热泵技术可以有效地提高一次能源利用率，减少温室效应气体CO2和其他大气污染物的排放。本文阐述了利用热泵供热比锅炉直接燃烧供热节能的原理，对主要的热泵供热形式，特别是地源热泵的技术特征、适用范围和经济性作了较详细的介绍。     

空气源热泵在我国暖通空调中的应用与发展

回顾空气／空气热泵和空气源热泵冷热水机组在我国暖通空调中的应用与发展。空气源热泵机组在我国应用十分广泛,它的发展与经济发展息息相关。本文介绍了提高空气源热泵低温适用性的主要技术措施,展望了空气源热泵在我国寒冷地区的应用。空气源热泵供暖属于生态供暖范畴,具有广阔的应用前景.     

地热水耦合热泵供热系统设计方案差异性分析

介绍地热耦合热泵供热系统(以梯级利用地热水热量为原则,采取地热水直接供热与热泵机组利用地热尾水余热的供热系统)设计方案的工艺流程、运行策略,建立供暖期系统能效比的计算模型。结合算例,在分阶段改变流量的质调节运行方式下,对两种地热耦合热泵供热系统的供暖期系统能效比进行计算。方案1:制热设备(地热水换热器、热泵机组)与供热循环泵采取一机一泵的固定设置。方案2:供热循环泵集中并联设置。对于方案1,供热循环泵与制热设备对应关系固定,启用某台制热设备时必须启用相应的供热循环泵。与方案1相比,由于方案2的供热循环泵集中并联设置,供热循环泵与制热设备的对应关系相对松散,匹配更加灵活。方案1、2的供暖期系统能效比分别为9.20、10.03。与方案1相比,方案2的供暖期系统能效比提高9%。     

A raw water source heat pump air-conditioning system

Raw water source is one of the promising new heat sources that researchers are looking into along with various others water-based sources such as ground, lake, river and sewage water. Generally, the water that is taken from the environment and supplied to a water treatment facility is called raw water. In this study, the heating and cooling performance of a heat pump utilizing the heat energy of raw water supplied to a water treatment facility is investigated. The two heat pumps being investigated have a heating capacity of 65.2 kW and were installed at the site for the heating and cooling of the central control room. A brazed plate heat exchanger was used for obtaining heat energy from the raw water. The raw water source provides a favorable heat source compared to the ambient air source except in spring. In the seasons of spring and autumn, the heating and cooling load are extremely low, this is the main reason for the poor performance of the raw-water heat pump system for those seasons. The average unit COP during the heating season is 3.3, and the average unit COP for the cooling season is 7.2.     

太阳能热水系统与地源热泵应用情况分析

对太阳能热水系统和地源热泵系统在工程实际中的应用情况进行了比较分析,分别就其工作原理、优缺点等作了论述,以期更有针对性的推广和应用这两种可再生能源系统。     

单、双级混合式热泵系统切换条件的实验研究

提出了由空气／水和水／水热泵机组组成的单、双级混合式热泵系统,并设计了该系统的实验样机。对空气／水热泵机组在低温条件下的运行情况进行了实验,分析了系统的制热能效比,确定了系统单、双级切换的条件。     

邯郸地区应用空气源热泵供暖可行性分析

空气源热泵是北方城镇集中供暖的有效补充,本文从技术、经济等方面对邯郸市城镇采用空气源热泵供暖的可行性进行了分析,并以空气源热泵作为供暖热源项目为例与其它多种供暖方式进行了对比,验证了在邯郸地区采用空气源热泵能够满足使用需求,经济效益和环境效益明显。     

热泵技术及其应用概述

介绍了热泵技术的产生与意义,具体阐述了空调热泵的分类及各种热泵的优缺点,并进一步分析了地源热泵供热空调系统的技术特点及经济优势,指出热泵技术是合理用能的典范,应大力推广应用.