Heat pump assisted distillation. V: A feasibility study on absorption heat pump assisted distillation systems

The problems in matching a heat driven absorption heat pump to a distillation process in heat pump assisted distillation are discussed. The performance of an absorption system is a function of the temperatures in the evaporator, the condenser, the absorber and the generator and the ratio of the mass flow rate in the secondary circuit to the mass flow rate in the primary circuit. In absorption systems design choices are limited by the Gibbs phase rule. Plots are given of the coefficient of performance against the temperatures of the top and bottom products and also against the energy saved.     

污水调节池对污水热能利用影响研究

以污水源热泵系统冬季工况为例,分别分析了污水调节池体积大小的设计方法,污水调节池设置与否对系统供暖建筑面积的影响,为污水热能利用工程的设计及施工提供参考。     

基于热回收的游泳池热泵除湿供暖系统

基于国内室内游泳馆能耗较高且大部分未设热回收装置的现状，讨论了利用热泵对游泳池供暖除湿的同时实现废热回收的系统设计方案以及回收效果，提出了利用太阳能辅助热泵运行的思想，并给出联合运行的设计方案。从能源利用的角度对二者进行了分析，并与常规的锅炉加冷水机组系统进行了经济性分析和比较，阐明将热泵应用于游泳池除湿供暖，不仅可以有效地节约能源，而且在经济上也是一个非常可行的方案。     

某商住楼两种不同空调方案的能耗分析

采用BIN能耗分析的方法,对天津市某一商住楼空调系统的两种不同方案进行能耗分析,比较两种系统在能源消耗上的差别,并提出了系统节能改造建议。     

Energy and exergy analysis of fossil plant and heat pump building heating system at two different dead-state temperatures

In this paper, we deal with the energy and exergy analysis of a fossil plant and ground and air source heat pump building heating system at two different dead-state temperatures. A zone model of a building with natural ventilation is considered and heat is being supplied by condensing boiler. The same zone model is applied for heat pump building heating system. Since energy and exergy demand are key parameters to see which system is efficient at what reference temperature, we did a study on the influence of energy and exergy efficiencies. In this regard, a commercial software package IDA-ICE program is used for calculation of fossil plant heating system, however, there is no inbuilt simulation model for heat pumps in IDA-ICE, different COP (coefficient of performance) curves of the earlier studies of heat pumps are taken into account for the evaluation of the heat pump input and output energy. The outcome of the energy and exergy flow analysis at two different dead-state temperatures revealed that the ground source heat pumps with ambient reference have better performance against all ground reference systems as well as fossil plant (conventional system) and air source heat pumps with ambient reference.     

An approach to optimised control of HVAC systems in indoor swimming pools

Indoor swimming pools are recognised as having a high level of energy consumption and present a great potential for energy saving. The energy is spent in several ways such as evaporation heat loss from the pool, high rates of ventilation required to guarantee the indoor air quality, and ambient temperatures with expressive values (typically 28?30°C) required to maintain conditions of comfort. This paper presents an approach to optimising control of heat ventilation and air conditioning systems that could be implemented in a building energy management system. It is easily adapted to any kind of pool and results in significant energy consumption reduction. The development and validation of the control model were carried out with a building thermal simulation software. The use of this control model in the case study building could reduce the energy efficiency index by 7.14 points (7.4% of total) which adds up to an energy cost saving of 15,609€ (7.5% of total).     

三种商业常用地源热泵系统经济性评价

本文将商业上常用的三种地源热泵系统进行经济性评价 ,并得出它们在一定条件下所需费用 ,最后对这三种系统所需费用进行比较     

Energy consumption of a residential building: comparison of conventional and RES-based systems

The energy needs of a typical one-family house in the Thessaloniki area for heating, cooling and domestic hot water production are calculated. The calculations are based on the typical average daily consumption of hot water and on the degree-day method for heating and cooling. The results are finally translated into thermal energy consumption, assuming the typical Greek situation (heating with diesel oil boilers and conventional radiators, cooling with local air-to-air split-type heat pumps and hot water production with electric heaters). The same energy needs are assumed to be covered by a vertical closed loop ground heat exchanger combined with a water-to-water heat pump system with fan-coils for heating and cooling and a thermosyphonic solar system for domestic hot water production. The ground heat exchanger/heat pump system efficiency is determined using data from an existing and continuously monitored similar system installed in the broader area of Thessaloniki. The solar system load coverage is calculated using the f-chart method. The energy consumption of the renewable energy systems is calculated and compared to that of the conventional system. The results prove that significant energy savings can be achieved.     

浅析地表水源热泵空调系统的节能特性

结合实际工程,阐明了地表水源热泵系统的节能原理,分析了系统在实际运行过程中的节能特性、经济效益和环境效益,表明该系统具有明显的节能效果、经济效益和环境效益,有一定的推广和应用价值。     

室温传感器偏差故障对武汉地区暖通空调系统的影响研究

暖通空调系统的高效节能运行高度依赖于传感器测量的准确性。在传感器全寿命运行周期中,不可避免发生各种故障,影响其准确性。为探究传感器故障对不同暖通空调系统的影响,文章以室温传感器偏差故障为例,针对武汉地区某办公建筑,同时开展地源热泵和冷水机组+锅炉两种暖通空调系统形式的能耗建模,对比分析-5℃~+5℃偏差故障对两种系统运行能耗、工作性能及室内热舒适性的影响差异。结果表明:室温传感器故障的偏差幅值方向对两种系统运行能耗、工作性能及室内热舒适性的影响规律不同。其中,地源热泵系统能耗受室温传感器偏差故障影响相对更小。     

Energy efficiency in long-term Mediterranean cropping systems with different management intensities

Optimising the implementation of energy used in agriculture is an important objective in the “Climate Action and Renewable Energy Package” adopted by the European Union. Therefore, studying the management of different cropping systems represents a good method to optimise input requirements, yield and net energy supply. The aim of this study is to compare the energy use of a 12-year rainfed cropping system, located in Tuscany, Italy. The system is cultivated under two different management intensities: a conventional system (CS) and a low input system (LIS) for a six-year crop rotation that included sugar beet, durum wheat, sorghum, sunflower, and durum wheat. In the sixth year, the soil was set-aside. The results showed that crop yield and energy yield were not significantly affected by management intensities, whereas energy efficiency of the low input system increased significantly, by about 30%. Future research should include more crops and locations to obtain further information about the range of energy parameters and their long-term trends. Furthermore, could be interesting to evaluate the overall reduction of environmental impacts and production costs that could occur limiting the use of chemicals and adopting conservative soil tillage strategies.     

Energy and environmental performance of a heat pump in different power grid scenarios

Electric-driven heat pumps are one of the most encouraging systems that could support the raising of renewables contribution in civil sector energy consumption, especially with reference to the Countries with a high contribution of renewable energy sources in electricity generation mix. However, the evaluation of the effective energy and environmental performance of an electric heat pump meeting the space heating and cooling requests of a building has to consider several factors that affect the results. Among them great attention should be given to the variability of weather conditions in which the system operates, the changeability of the efficiency and environmental indicators of power grid. The analysis becomes more complex if the variation of these parameters is considered in terms of time and geographic location but it leads to the actual evaluation of the energy conversion system performance that is neglected by European Regulations. This paper presents an energy and environmental analysis of an electric-driven air-source heat pump providing the space heating and cooling needs of the same building located in two different geographical locations by means of a dynamic simulation performed in TRNSYS 17. The analysis is carried out considering the average and time-dependent values of the carbon dioxide emission factors for electricity and the power grid efficiency indicators evaluated by means of the real electricity generation data. In addition, the paper proposes the evaluation of the average and hourly energy and environmental parameters referred only to the electricity market zones in which the buildings are located. These indices are considered in the analysis too. The results have highlighted that the assessment based on average and high-resolution parameters, as well the evaluation based on indicators referred to electricity market zones only, could return very different outcomes leading to a significant overestimation or underestimation of the energy and environmental performance of the system based on the electric-driven heat pump. Finally, a further analysis has been carried out to determine how the results can vary considering the average value of the electric efficiency indicator suggested by Italian Regulations and that of other European Countries.     

Advances in heat pump systems: A review

Heat pump systems offer economical alternatives of recovering heat from different sources for use in various industrial, commercial and residential applications. As the cost of energy continues to rise, it becomes imperative to save energy and improve overall energy efficiency. In this light, the heat pump becomes a key component in an energy recovery system with great potential for energy saving. Improving heat pump performance, reliability, and its environmental impact has been an ongoing concern. Recent progresses in heat pump systems have centred upon advanced cycle designs for both heat- and work-actuated systems, improved cycle components (including choice of working fluid), and exploiting utilisation in a wider range of applications. For the heat pump to be an economical proposition, continuous efforts need to be devoted to improving its performance and reliability while discovering novel applications. Some recent research efforts have markedly improved the energy efficiency of heat pump. For example, the incorporation of a heat-driven ejector to the heat pump has improved system efficiency by more than 20%. Additionally, the development of better compressor technology has the potential to reduce energy consumption of heat pump systems by as much as 80%. The evolution of new hybrid systems has also enabled the heat pump to perform efficiently with wider applications. For example, incorporating a desiccant to a heat pump cycle allowed better humidity and temperature controls with achievable COP as high as 6. This review paper provides an update on recent developments in heat pump systems, and is intended to be a “one-stop” archive of known practical heat pump solutions. The paper, broadly divided into three main sections, begins with a review of the various methods of enhancing the performance of heat pumps. This is followed by a review of the major hybrid heat pump systems suitable for application with various heat sources. Lastly, the paper presents novel applications of heat pump systems used in select industries.     

几种常见风力发电系统的技术比较

结合国内外风力发电的发展现状介绍了几种常见的风力发电系统，详细阐述了风力发电原理和风力机系统的数学模型，并对这几种风力机系统进行技术比较，最后简要介绍了风力发电接入系统后对电网的影响。     

Estimation of potential savings from reducing unburned combustible losses in coal-fired systems

A potentially significant loss emanates from the combustion of coal fuels is usually called as the unburned carbon loss. All coal-fired steam generators and coal-fired vessels inherently suffer from efficiency debit attributable to unburnt carbon. The aim of this study is to develop a simple-to-use predictive tool which is easier than existing approaches, less complicated with fewer computations and suitable for engineers to determine the approximate potential savings resulting from reducing unburned coal fuel loss. The proposed method determines the benefits of reducing the combustible losses in terms of annual fuel savings for coal-fired units as a function of percent combustibles in ash, achievable percent combustibles in ash, unit design heat output and average fuel cost. Results show that the proposed predictive tool has a very good agreement with the reported data with average absolute deviation percent being around 1.77%. The proposed method is superior owing to its accuracy and clear numerical background, wherein the relevant coefficients can be retuned quickly for various cases. The developed tool can be of immense practical value for the utility engineers to have a quick check on the benefits of reducing the combustible losses in terms of annual fuel savings for a coal-fired unit for wide range of operating conditions without the necessity of any pilot plant set up and experimental/plant trials. In particular, practice engineers would find the methodology to be user friendly involving transparent calculations with no complex expressions for the design and operation of coal-fired systems such as furnaces and boilers.     

Temperature distribution and performance of ground-coupled multi-heat pump systems for a greenhouse

The primary objective of a greenhouse is to produce good plant-growth conditions such as temperature and humidity. One of the hot issues for the greenhouse is to provide an appropriate heating system which can achieve favorable temperature condition and save energy. In this study, the performance of a ground-coupled multi-heat pump system for the greenhouse heating was investigated. The ground-coupled multi-heat pump system was composed of GLHX (ground loop heat exchanger) and multi-heat pump unit which had one outdoor unit and two or more indoor units. The temperature distribution within the greenhouse using the ground-coupled multi-heat pump system was represented relatively uniform comparing to when the conventional heating system and GCHP system were adopted, because the capacity of each indoor unit could be changed linearly according to the variation of load. The temperature difference between the maximum and minimum temperatures and the standard deviation of inside temperature for the greenhouse were 2.1 °C and 1.2 °C, respectively. It is necessary to develop the multi-heat pump unit which can be operated with high performance at relatively low temperature setting conditions. The system COP of the ground-coupled multi-heat pump unit decreased greatly at part load condition due to relatively high power consumption of the ground circulation pump. Therefore, it is suggested that a control algorithm of the ground circulation flow rate has to be developed to maximize energy saving by applying the ground-coupled multi-heat pump system to the greenhouse.     

多种可再生能源渗透场景下的热电联产系统优化

针对传统热电联产(CHP)系统受热电耦合的限制,灵活调节能力低、可再生能源消纳能力弱的问题,分析了传统热电联产系统的灵活性不足机理,提出采用地热源热泵来提高其灵活性。为了确定地热源热泵(GSHP)的最优容量,建立了考虑切负荷惩罚、可再生能源弃用惩罚、设备投资成本及运行成本的热电联产-地热源热泵系统优化模型,将该模型运用到可再生能源渗透率(可再生能源发电量/总发电量)分别为15%,40%和55%的3种情景中。结果表明：地热源热泵的容量随可再生能源渗透率的提升而提升,同时地热源热泵的集成可以扩大系统的可运行域,提高可再生能源的消纳容量;在最优地热源热泵容量下,3种场景的日节约成本分别为38%,64%和70%,同时集成系统的能源利用率可超过100%,可再生能源弃用的惩罚成本分别下降100%,89%和89%。     

Energy and exergy analyses of fabricated solar drying system with smooth and rough surfaces at different conditions: A case study

For this experimental work, the solar dryer system has been fabricated. Various experiments have been performed to evaluate the performance of the fabricated dryer system. Energy and exergy concepts have been used for the assessment. And comparative analyses have also been done with smooth and rough surfaces: Grade 150 and Grade 300. This experimental work has been concluded as the maximum collector (i.e., 74°C) and cabinet temperatures (i.e., 66°C) are attained at 13:00 p.m. with Grade 300 surface. Maximum moisture loss (i.e., 35 g) and percentage moisture loss (i.e., 7.53%) are recorded at 13:00 p.m. again with a rough surface. Minimum exergy destruction rate (i.e., 0.294 W) but minimum exergy efficiency (i.e., 20.82%) are found at 17:00 p.m. with a black painted surface, which is not an acceptable condition. Maximum energy efficiency (i.e., 35.98%) and heat removal factor (i.e., 0.56) are obtained at 13:00 p.m. with a rough surface. The best performance from the fabricated solar system is received between 12:00 and 14:00 p.m. This study recommends rough surfaces and 12:00–13:00 p.m. timings for the solar drying system as the performance of the system is better in terms of energy–exergy.     

Energy savings and heat efficiency in the paper industry: A case study of a corrugated board machine

The paper presents the improvement of energy management in a steam system used for corrugated board production. The system consists of a steam boiler (fired with natural gas), steam and condensate pipelines and a corrugated board production installation (steam consumer). In the existing system, the boiler works in unison with an open condensate tank. This tank is responsible for energy losses due to secondary steaming. Therefore, a system of a closed tank has been proposed to eliminate these energy losses. The coefficients of thermal performance and the energy losses in both cases (open and closed tank) are compared. The study shows that the losses of the closed steam system are always lower than those of the open system. The coefficient of performance could be increased by about 8% by the proposed modernization. The recovery of expenses for modernization should be very quick, taking place within a year.     

A review of methods to evaluate borehole thermal resistances in geothermal heat-pump systems

In the design of a ground-source heat pump (GSHP) system, the heat transfer from the fluid to the ground is influenced by the thermal borehole resistance between the fluid and the borehole surface and also by the interference resistance between the two (or four) pipes inside the borehole. Several authors have proposed empirical and theoretical relations to evaluate these resistances as well as methods to evaluate them experimentally. The paper compares the different approaches and proposes good practice to evaluate the resistances. The impact of the different approaches on the design of heat exchanger is also examined. Two-dimensional and fully three-dimensional numerical simulations are used to evaluate the different methods. A new method is also proposed to evaluate the borehole resistances from in situ tests.