Developing Operational Model for Heat Pumps as Space Heating and Domestic Hot Water Provider

In the United Kingdom, means of meeting domestic heating is being electrified to decarbonise in effort to reduce the greenhouse gases emissions from the burning of natural gas. Therefore, the uptake of heat pumps is on the increase. The operation and working principle of heat pumps must be well understood in the investigations of their impacts on the grid and the grid assets, especially distribution transformers which could be overloaded due to higher peak load demand. This work develops an operational model of heat pumps as combined space heating and domestic hot water provider implemented in MATLAB. The developed operational model of heat pumps is adaptable and repeatable for different input parameters. The developed model is used to generate daily average demand profiles of heat pumps for a typical winter weekday and a typical summer weekday. The generated demand profiles of heat pumps by the developed model compared well with the demand profiles of heat pumps generated from actual field projects which are usually expensive and time-tasking.

Energy efficiency performance of multi-energy district heating and hot water supply system

A district heating and hot water supply system is presented which synthetically utilizes geothermal energy,solar thermal energy and natural gas thermal energy.The multi-energy utilization system has been set at the new campus of Tianjin Polytechnic University(TPU),A couple of deep geothermal wells which are 2 300 m in depth were dug,Deep geothermal energy cascade utilization is achieved by two stages of plate heat exchangers(PHE) and two stages of water source heat pumps(WSHP).Shallow geothermal energy is used in assistant heating by two ground coupled heat pumps(GCHPs) with 580 vertical ground wells which are 120 m in depth.Solar thermal energy collected by vacuum tube arrays(VTAs) and geothermal energy are complementarily utilized to make domestic hot water.Superfluous solar energy can be stored in shallow soil for the GCHP utilization.The system can use fossil fuel thermal energy by two natural gas boilers(NGB) to assist in heating and making hot water.The heating energy efficiency was measured in the winter of 2010-2011.The coefficients of performance(COP) under different heating conditions are discussed.The performance of hot water production is tested in a local typical winter day and the solar thermal energy utilization factor is presented.The rusults show that the average system COP is 5.75 or 4.96 under different working conditions,and the typical solar energy utilization factor is 0.324.

Space heating and hot water demand analysis of dwellings connected to district heating scheme in UK

To achieve CO2 emissions reductions, the UK Building Regulations require developers of new residential buildings to calculate expected CO2 emissions arising from their energy consumption using a methodology such as Standard Assessment Procedure （SAP 2005） or, more recently SAP 2009. SAP encompasses all domestic heat consumption and a limited proportion of the electricity consumption. However, these calculations are rarely verified with real energy consumption and related CO2 emissions. This work presents the results of an analysis based on weekly heat demand data for more than 200 individual fiats. The data were collected from a recently built residential development connected to a district heating network. A method for separating out the domestic hot water （DHW） use and space heating （SH） demand has been developed and these values are compared to the demand calculated using SAP 2005 and SAP 2009 methodologies. The analysis also shows the variation in DHW and SH consumption with size of flats and with tenure （privately owned or social housing）. Evaluation of the space heating consumption also includes an estimate of the heating degree day （HDD） base temperature for each block of fiats and compares this to the average base temperature calculated using the SAP 2005 methodology.

Comparison and Performance Analysis of Heat Storage Equipment in Solar Heating System

Solar heating system is widely used recently. Heat storage equipment is the guarantee for steady performance of solar heating system. A design of latent heat storage exchanger with submerged coil was introduced with the structure, working principle, and the main advantages. This heat exchanger was integrated into solar heating system as the heat storage equipment. Advantage comparison of the designed heat exchanger in solar heating system with hot water tank was carried out. The analysis results show that the latent heat storage exchanger is superior to hot water tank obviously. The heat exchanger performance parameters and variations of these parameters are got： （1） with the increase of phase change material （PCM） volume ratio, heat storage equipment volume ratio decreases; （2） heat storage efficiency has the same varying tendency with outdoor and air temperature; while the bigger PCM volume ratio is, the weaker the effect of outdoor air temperature on heat storage efficiency is; （3） heat storage capacity and heat storage efficiency increase together; when PCM volume ratio is big, heat storage efficiency is high and the system can begin operating effcienfly and quickly; （4） with the increase of heat storage capacity, life cyde operation cost （LCOC） of system increases gradually in high speed; but with the increase of PCM volume ratio, the difference between the two systems LCOCs becomes smaller and smaller; （5） the reasonable range of PCM volume ratio is 0.5 - 0.7. Temperature characteristic analysis shows that, with the filled PCM, heat storage medium temperature presents several segments at different time, under conditions of different heat storage capacity and different PCM state.

Solar Hot System and Design of Buildings

Domestic solar hot water system, the use of the status quo and existing problems, by analyzing the solar water heating equipment and building integrated and building integrated design.

Performance Analysis of a Solar Continuous Adsorption Refrigeration System

A study is conducted on the performances of a solar powered continuous-adsorption refrigerator considering two particular days as references cases,namely,the summer solstice(June 21st)and the autumn equinox(September 21st).The cooling capacity,system performance coefficient and the daily rate of available cooling energy are assessed.The main goal is to compare the performances of a solar adsorption chiller equipped with a hot water tank(HWT)with an equivalent system relying on solar collectors with no heat storage module.The daily cooling rates for the solar refrigerator are found to be 102.4 kWh and 74.3 kWh,respectively,on June 21st and on September 21st,using a total collector’s area of 43.47 m2.The corresponding values for the adsorption chiller equipped with a hot water tank of 2 m3(and using a total collector’s area of 72.45 m2),are 127.1 kWh and 106.13 kWh,respectively.

Modulating a Solar Parabolic Dish to Produce Boiled Water

A two-meter parabolic solar concentration dish has been modulated to produce boiled water over 100℃ for various purposes of central heating services. For an effective performance, the system required both continuous exposure of the dish to sunlight during the day time as well as to an electric control circuit （tracking system）. The amount of the potable water was dependent particularly on the accurate centering of the system which could increase upon preheating. This system has therefore been possible to heat up water at home via increasing the temperature in hot tank by both covering the hot water tank and isolating it from the surroundings using insulators. Applications of a successful parabolic solar concentration has also been designed to provide desalinated water for domestic usage which operates with temperatures higher than other types of the solar radiation for the future.

Developments of solar collectors in China

China has abundant solar energy resource. Solar thermal collectors, particularly all-glass evacuated tubular collectors, have been studied and developed for 30 years, and solar thermal industry has developed rapidly for 15 years. There are various solar thermal systems, with an operation area of around 108 million m2 in 2007. These systems mainly provide domestic hot water, but some other applications are under extensive study and development as well.

太阳能-空气源热泵热水系统新型组合优化设计

太阳能-空气源热泵热水系统(solar-air source heat pump hot water system, SAHWS)常用于宿舍楼宇供暖,通过对系统参数的优化设计可显著提高系统能效性能与环境友好性。为得到一种综合考虑SAHWS经济、能源、环保与节能的优化方法,提出了一种新型组合优化设计策略,并利用TRNSYS软件搭建系统仿真模型,以西安、西宁、拉萨这3座不同太阳能资源等级城市为例,对SAHWS运行工况对比分析。结果表明:与常用生命周期成本设计相比,所提出的组合优化设计不仅降低了系统成本,还有着较低的系统能耗;组合优化设计的热泵能耗与工作小时数最短,且有最低的热损,在投资成本、系统季节性能因子、太阳能保证率以及碳粉尘、二氧化碳排放量均有较好表现。

温室传热水道与土壤换热强度影响的数值分析

以呼和浩特市某日光温室铺设的传热水道为研究对象,为提供传热水道在土壤中铺设间距、深度的准确依据,利用CFD数值模拟技术对传热水道在不同供水温度(30、40、50℃)、不同埋管深度(30、40、50cm)、不同管道间距(20、40、50cm)的情况时对温室土壤的换热强度进行研究与分析。结果表明:埋管深度越深对土壤地面温度影响越小,管道间距越宽则土壤的温度分布越分散,使土壤不容易达到温度扩散的饱和值,管温越高对管道以下的土壤影响越大,造成资源浪费;当埋管深度为30cm、管间距为20cm时,土壤的换热效果最佳。研究结果可为温室传热水道对土壤加热提供理论参考。

“空气源热泵-太阳能”热水系统在高校学生公寓的应用

学生公寓热水需求量大且用水时间较为分散,选择少污染且高效的热源形式,对高校的节能减排有重要的意义。空气源热泵辅助太阳能热水系统水温恒定,可全天候供应热水,满足阴雨天及冬季使用热水需求,智能化程度高,节能效果明显且项目回收周期短,可以在高校中推广使用。介绍山东某高校公寓实际运行的空气源热泵辅助太阳能热水系统及其控制原理;并通过对电热水器和单独采用空气源热泵制取热水方式的年耗电量计算,与实际运行项目的年耗电量比较,对其节能性进行分析。由于对系统各设备的启停采用了智能控制系统,能够对系统运行模式进行灵活调控,使得该系统比电热水器节电75%,比独立空气源热泵系统节电30%。根据2021年项目实际年收入,预计该系统回收周期为4.2年。

太阳能热水系统节能率与设计参数的探讨

太阳能热水系统的能耗主要为辅热系统的能耗,其节能率与系统设计保证率呈正相关。通过分析太阳辐照量与生活热水耗热量的关系可知,选取节能率变化曲线偏离点处的太阳能保证率可避免出现热量浪费和一次投资过大,保证较高的经济效益。选取了长沙地区的3种典型的设置集中热水供应系统的建筑进行分析,依据长沙地区的气象参数和此三类建筑生活热水耗热量的变化特征,得出各自节能率变化曲线偏离点处的太阳能保证率的取值。同时,根据公式计算了长沙地区平板型太阳能集热器的年平均集热效率;推导了q_(rid)值的计算方法并推荐了在长沙地区的取值。

太阳能热泵复合系统应用与节能分析

本文分析计算了广东某地区一个300间客房的酒店采用太阳能和热泵复合系统供应热水的方案,并且和采用电热水器供热水的方案进行了对比。研究表明,采用太阳能热泵复合系统仅需要18匹的热泵配20平米的太阳能集热器,即可满足每间客房8小时供热水的需求。供应热水的方案无论从初投资还是运行费用以及环保方面,都具有明显的优势。该方案可以为类似热水需求单位提供理论和现实的指导。

低谷电制备生活热水设计研究

结合现行国家标准中关于低谷电加热制备生活热水的要求,从低碳、节能、经济的角度出发,优化现有低谷电加热制备生活热水系统提出了若干种适用于不同场景的低谷电耦合太阳能或空气源热泵制备生活热水的可行方式。

基于旧建筑改造的高端酒店式公寓热水系统设计难点探讨

近年来,由于我国社会经济转型、人口结构的变化,原先建造的大量建筑已经不满足市场经济的需要,存量旧建筑的改造成为一种行业现象。而改造项目由于新、旧标准不一致,建筑定位、功能、分隔变化,需要衔接原系统等原因,设计难度往往大于新建项目,通过海南三亚某小区3栋高层住宅楼改高端酒店式公寓的改造案例,分析阐述了原建筑集中热水系统存在着诸如系统过于复杂、热损失较大、采用太阳能+空气源热泵作为热源的双能源耦合热水系统无法实现耦合等比较典型的改造设计难点,并针对这些现存问题提供了如减少热源,简化、优化系统等一系列解决方案。旧建筑改造完毕后,至今运营良好。通过案例剖析,探讨了高端酒店式公寓热水系统改造设计思路。

“双碳”目标下零碳建筑电气化研究

鉴于建筑用能全面电气化是实现零碳、低碳运行的最佳途径,根据供暖、炊事、生活热水现状调研分析零碳建筑电气化,分别通过居住建筑和公共建筑工程实例进行供暖、炊事、生活热水有无电气化的碳减排计算,进而研究零碳建筑电气化潜力,得出采用高效的空气源热泵制热可以有效降低建筑供暖的碳排放,电炊具比燃气炊具产生更多的碳排放,采用电热水器碳排放高于燃气热水器,但采用空气源热泵热水器、太阳能等方式能有效降低碳排放。同时,分析了“双碳”目标下零碳建筑电气化中存在的问题,如在超高温热泵、大容量高温热泵、超大容量热泵领域有待深入开展研发,能源价格体系改革等,最后提出零碳建筑电气化未来技术展望。

吨水耗电量在太阳能空气源热泵热水系统的应用

随着建设绿色低碳校园的理念提出,太阳能空气源热泵技术在高校得到了广泛应用。为了更好地分析和评价太阳能空气源热泵热水系统的节能降碳效果,以某高校宿舍楼为研究对象,设计了并联式太阳能空气源热泵(SC-ASHP)热水系统,分析了该系统的年实际运行情况,并与单一热泵(ASHP)热水系统的运行情况进行了对比研究。结果表明:该高校宿舍楼典型用水高峰期在18:00-22:00时,这有利于并联式太阳能空气源热泵热水系统在白天利用太阳能加热水箱,剩余不足部分由热泵进行补热。吨水耗电量可作为评价该热水系统运行效果的关键参数,并联式太阳能空气源热泵热水系统吨水耗电量y随环境温度T_a升高在逐渐降低,随进水温度T_(in)升高先减小后增大。在T_a和T_(in)都是11.5℃时,系统吨水耗电量达到最小值,这是因为当T_(in)>11.5℃时,不利于热泵凝汽器放热,热泵效率降低,热水系统吨水耗电量随之增大。并联式太阳能空气源热泵热水系统吨水耗电量整体低于单一热泵热水系统,其中热泵对系统吨水耗电量的影响最大。并联式太阳能空气源热泵热水系统比单一热泵热水系统年平均节省电量为4.18万kW·h,年平均降低CO_(2)间接排放量为41.67 tCO_(2),具有明显的节能降碳效果。

太阳能建筑的研究进展综述

对被动式太阳能建筑和主动式太阳能建筑的应用现状和研究进展进行阐述,并对主动式太阳能建筑中可与建筑相结合的太阳能热利用技术和可与建筑相结合的光伏发电技术进行分析。结果表明:1)被动式太阳能建筑技术研究方法逐渐由定性分析为主转向定性、定量和综合分析,并以节能低碳、室内热舒适度、设计优化及相变材料的应用作为研究重点。2)系统的性能系数和太阳能保证率是建筑太阳能热利用技术的研究重点,设备选型、系统设计、运行策略是主要研究内容;阴、雨、雪天等太阳能无法利用的工况多采用太阳能辅助热泵供暖系统。3)增强光伏组件通风性可使光伏组件降温,提升光伏建筑一体化(BIPV)建筑的光伏发电量;回收利用光伏发电伴生热量有助于提升能源综合利用率。

深圳某医院热水系统案例分析

为切实推动国家绿色建筑高质量发展,实现房屋用能自给自足及“双碳”目标,积极利用清洁可循环能源是当下的重要思路。深圳地区太阳能、空气热能资源丰富,空调使用率高,项目应优先采用太阳能、空调余热作为主要热源,空气源热泵作为辅助热源。有条件的情况下采用双热源并联系统,减少空气源热泵的开启时间,从而最大程度节省能源。文章以深圳某综合医院为案例分析热水系统在结合深圳地区特性的前提下,采用太阳能、余热加空气源热泵双热源供水系统的可推广性。

基于太阳能和热回收预热的空气源热水系统逻辑控制监理要点

由于涉及系统效率的问题,多种热源的热水系统在不同情况下,采用一种或几种热源要有严格的逻辑控制。文章通过对系统原理图进行剖析,从单个热源如太阳能集热、空调热回收等的逻辑控制,到预热、加热和保温等各层逻辑控制,再到热水回水循环加热等系统运作逻辑控制,都进行了详细的分析和说明。此外,对关键部件如紫外线光催化二氧化钛(AOT)消毒器、膨胀罐和循环水泵的安装和运作也进行了分析,以保证各部件的有效运行。