Heat transfer performance of fresh-air handing device using earth energy

In order to reduce the fresh-air handing energy consumption,a fresh-air handing device using earth energy was presented. The major part is a double pipe soil-air heat exchanger. Its performance was tested in summer and winter. The results show that while the volume of the treated fresh-air is 125 m3/h,in summer,at the outlet of the device,the air temperature is 21.5-24.0 ℃,the air humidity ratio is about 17 g/kg,the greatest temperature drop is about 9 ℃ ,and the largest dehydration quantity is about 6 g/kg. In winter,at the outlet of the device,the air temperature is 15-17 ℃,the air humidity ratio is about 11 g/kg,the largest temperature rise is about 11 ℃,and the largest humidification quantity is about 6 g/kg. Therefore,the application of this new fresh-air handing device can take full advantage of the natural energy,thus effectively reduce the traditional energy consumption for fresh-air handing.

A power plant for integrated waste energy recovery from liquid air energy storage and liquefied natural gas

Liquefied natural gas(LNG)is regarded as one of the cleanest fossil fuel and has experienced significant developments in recent years.The liquefaction process of natural gas is energy-intensive,while the regasification of LNG gives out a huge amount of waste energy since plenty of high grade cold energy(-160℃)from LNG is released to sea water directly in most cases,and also sometimes LNG is burned for regasification.On the other hand,liquid air energy storage(LAES)is an emerging energy storage technology for applications such as peak load shifting of power grids,which generates 30%-40%of compression heat(-200℃).Such heat could lead to energy waste if not recovered and used.The recovery of the compression heat is technically feasible but requires additional capital investment,which may not always be economically attractive.Therefore,we propose a power plant for recovering the waste cryogenic energy from LNG regasification and compression heat from the LAES.The challenge for such a power plant is the wide working temperature range between the low-temperature exergy source(-160℃)and heat source(-200℃).Nitrogen and argon are proposed as the working fluids to address the challenge.Thermodynamic analyses are carried out and the results show that the power plant could achieve a thermal efficiency of 27%and 19%and an exergy efficiency of 40%and 28%for nitrogen and argon,respectively.Here,with the nitrogen as working fluid undergoes a complete Brayton Cycle,while the argon based power plant goes through a combined Brayton and Rankine Cycle.Besides,the economic analysis shows that the payback period of this proposed system is only 2.2 years,utilizing the excess heat from a 5 MW/40 MWh LAES system.The findings suggest that the waste energy based power plant could be co-located with the LNG terminal and LAES plant,providing additional power output and reducing energy waste.

Techno-economic feasibility assessment of a diesel exhaust heat recovery system to preheat mine intake air in remote cold climate regions

Underground mines in Arctic and Subarctic regions require the preheating of mine intake air during winter.The cold fresh air of those remote areas can be as severe as
40℃ and commonly needs to be heated to around+3℃.This extensive amount of heating is usually provided by employing large-size air heaters,fueled by diesel,propane,natural gas,or heavy oil,leading to high energy costs and large carbon footprints.At the same time,the thermal energy content of a diesel generator sets(gen-sets)exhaust is known to be one-third of the total heating value of its combusted fuel.Exhaust heat recovery from diesel gen-sets is a growing technology that seeks to mitigate the energy costs by capturing and redirecting this commonly rejected exhaust heat to other applications such as space heating or pre-heating of the mine intake air.The present study investigated the possibility of employing a simple system based on off-theshelf heat exchanger technology,which can recover the waste heat from the exhaust of the power generation units(diesel gen-sets)in an off-grid,cold,remote mine in Canada for heating of the mine intake air.Data from a real mine was used for the analysis along with environmental data of three different location-scenarios with distinct climates.After developing a thermodynamic model,the heat savings were calculated,and an economic feasibility evaluation was performed.The proposed system was found highly viable with annual savings of up to C$6.7 million and capable enough to provide an average of around 75%of the heating demand for mine intake air,leading to a payback period of about eleven months or less for all scenarios.Deployment of seasonal thermal energy storage has also been recommended to mitigate the mismatch between supply and demand,mainly in summertime,possibly allowing the system to eliminate fuel costs for intake air heating.

Air purifier or fresh air system?A comparison of energy consumption and cost in urban China residential buildings

Chinese urban residential buildings face serious indoor air quality problems.Air purification systems(e.g.,air purifiers,fresh air systems)that supply fresh air or purify indoor air are widely used in residential buildings to improve indoor air quality.Considering the challenges of energy conservation and emission reduction,it is urgent to guide residents on choosing appropriate air purification systems.The key problem is how to identify the best air purification system with the lowest energy consumption or operating cost.Comparisons of air purification systems have rarely been conducted on the premise that they should deliver air such that the main indoor pollutant concentrations all meet air quality standards.Also ignored in comparisons are the increased filtration resistance caused by dust accumulation on the filter and the cost of filter replacement.In this study,we propose a method to compare residential air purification systems based on energy consumption and total cost,and we provide methods to select air purification systems in China's different climatic regions.We used a standard two-person bedroom as the example,and determined the most suitable(minimum cost or energy consumption)air purification systems for the capital cities of the provinces in Chinese mainland.

The Efficiency Analysis of the Exhaust Air Heat Pump System

This paper is based on long term parameter measurements of the exhaust air heat pumps (EAHP) system in a new built apartment building. The building was equipped with an exhaust air ventilation system and exhaust air heat pump for ventilation heat recover. The results of the measurements show that the COP of the EAHP is mainly related to the temperature graph of the heating system and the supply temperature of domestic hot water (DWH). During the measurement period some other impact factors, such as the quality of maintenance, the nighttime temperature graph of the heating system, the reduction of the exhaust air flows in case of low temperatures, mistakes in designing and low building quality, have also played a role. An analysis of energy consumption shows that in winter conditions the COP is about 3.0 and in the transition period about 3.3. The energy recovery value of the EAHP is 0.5.

Electrochromism-induced adaptive fresh air pre-handling system for building energy saving

Building fresh air supply needs to meet certain regulations and fit people’s ever-growing indoor air quality de-mand.However,fresh air handling requires huge energy consumption that goes against the goal of net-zero energy buildings.Thus,in this work,an adaptive fresh air pre-handling system is designed to reduce the cool-ing and heating loads of HVAC system.The sky-facing surface of the system uses electrochromic mechanism to manipulate the optical properties and thus make full use of solar energy(solar heating)and deep space cold source(radiative cooling)by switching between heating and cooling modes.In the cooling mode,the sky-facing surface shows a transmittance of down to zero,while the reflectance is high at 0.89 on average.In the heating mode,the electrochromic glass is highly transparent,allowing the sunlight to reach the solar heat absorber.To obtain the energy-saving potential under different climates,six cities were selected from various climate regions in China.Results show that the adaptive fresh air pre-handling system can be effective in up to 55.4%time of a year.The maximum energy-saving ratios for medium office,warehouse,and single-family house can reach up to 11.52%,26.62%,and 18.29%,respectively.In addition,the system shows multi-climate adaptability and broad application scenarios,making it a potential solution to building energy saving.

Closed-loop bulk air conditioning: A renewable energy-based system for deep mines in arctic regions

With depletion of shallow deposits,the number of underground mines expected to reach more than 3 km depth during their lifetime is growing.Although surface cooling plants are mostly effective in mine airconditioning,usually secondary cooling units are needed below 2 kmdepth.This need emerges due to the elevated thermal impacts caused by auto-compression of mine air as well as heat emissions from strata and mine machinery.As a result,in cold climates,like Canada,ultra-deep mines need their secondary underground cooling plants running year-round while the intake air must be heated to protect the sensitive machinery and liners from freezing during the winter season.To cool mine air,horizontal bulk-airconditioners with direct spray cooling systems are commonly used due to their high performance.Conventionally,sprayed water in bulk-air-coolers are mechanically circulated and refrigerated in coupled refrigeration plants.This set up can be transformed to a natural cooling/heating process by resurfacing the warm underground bulk-air-cooler spray water for mine air heating on the surface and re-sinking the chilled water for cooling in the underground bulk air coolers.This could significantly cut-down the fossil-fuel consumption in burners for mine air pre-conditioning and refrigeration cost when applicable.This paper presents an anonymous real-life example to study the feasibility of the proposed idea for an ultra-deep Canadian mine.

Energy and Buildings

Exhaust air heat recovery is of great significance for building energy conservation.Since passive heat recovery systems use temperature or enthalpy difference between outdoor air and indoor air to drive the system,the temperature of fresh air supply cannot meet indoor requirements and the exhaust heat is not fully recovered.In this study,a solar-driven exhaust air thermoelectric heat pump recovery(SDEATHP)system is tested and evaluated for its ability to recover thermal energy from exhaust air to cool or heat fresh air.An experimental platform was established to test its performance.Results show that the SDEATHP system can obtain higher fresh air supply temperature in winter and lower fresh air supply temperature in summer.The system requires only 3.12 W of power for the fans,and the average relative cooling coefficient in summer and the average relative heating coefficient can reach 50.6 and 57.9,respectively.The optimal operating current and voltage of TE modules and photovoltaic system is analyzed,and then the number and types of electrical connections for the TE modules in SDEATHP system are discussed.The SDEATHP system provides a new method for building energy recovery and fresh air supply.

Technical Measures and Selections for Reducing Flue Gas Heat Loss of Large Coal-Fired Boilers

The main technologies for reducing flue gas heat loss of pulverized coal-fired boilers are introduced, and the suitability of these technologies for boiler operation and the principles for selection of these technologies are explored. The main conclusions are： 1） the non-equilibrium control over flue gas flow rates at the inlet of the air heater and the reversal rotation of the air heater rotator should be popularized as regular technologies in large boilers; 2） increasing the area of the air heater to reduce the flue gas heat loss in pulverized coal-fired boilers should be the top option and increasing the area of the economizer be the next choice; 3） low- pressure economizer technology could save energy under special conditions and should be compared with the technology of increasing economizer area in terms of technical economics when the latter is feasible; 4） the hot primary air heater is only suitable to the pnlvefizing system with a large amount of cold air mixed.

一种新型溶液除湿空调系统能耗及应用分析

传统空调系统通常采用温湿度联合处理的方式,该方式存在舒适性差、能源消耗大等问题。针对以上问题,提出一种利用复合直接蒸发冷却制冷水的溶液除湿空调系统,该系统可以有效节省功耗,符合节能减排的发展趋势。在研究过程中,以某办公楼为研究对象,利用TRNSYS仿真软件建立该系统,研究其在制冷季7—9月的能耗,分析其节能性及适用性。结果表明:当空调新风系统使用太阳能热水作为再生热源时,总供热能耗为6.1×10^(5)kW·h,总耗功为8.73×10^(4)kW·h。相比于传统空调系统,节能率达到55.2%,为降低空调系统能耗提供了新思路。

严寒地区超低能耗教学建筑新风系统适用性分析

目的 解决严寒地区超低能耗建筑中人员密集场所供暖期新风系统的适用性问题。方法 以沈阳市某小学教学楼中三种典型教室为例,应用Designbuilder软件建立能耗模型,分析自然通风、有无热回收的定(变)风量机械通风五种工况下超低能耗建筑的各项能耗、相对节能率和本体节能率,以及室内CO_(2)体积分数变化。结果 无热回收的变风量、有热回收的定(变)风量与无热回收的定风量机械通风相比,节能率分别为12%~30%、32%~46%、38%~57%;有热回收的变风量机械通风总能耗最低,且接近自然通风工况;五种工况室内CO_(2)体积分数均小于0.09%。结论 人员密集场所中有热回收的定(变)风量机械通风节能效果显著;建筑气密性的提高导致机械通风系统新风能耗增加,经济性和节能性下降。

风机盘管加新风系统室内微循环热舒适性研究

随着人们生活水平的提高,医院在提升治疗服务的同时迫切需要改善患者就医环境和医护人员的工作环境。目前,医院建筑中特别是病房广泛应用的风机盘管加新风系统存在温度分布不均匀、吹风感较强、噪音大等问题,导致了患者的室内热舒适性无法得到保障。因此,针对医院病房,探索研究风机盘管加除湿置换新风空调系统,在实际搭建的实验平台基础上建立CFD数值模拟模型,将模拟结果与实验数据相对比,论证了模型的准确性之后,通过CFD模拟的方式,在保证对流换热可以达到室内设定温度的前提下,找到一种新的气流组织形式,这样不仅有效降低室内人员的吹风感和噪音,而且避免了传统置换通风容易出现温度分层、垂直温差过大的问题。

Design and engineering implementation of non-supplementary fired compressed air energy storage system: TICC-500

The integration and accommodation of the wind and solar energy pose great challenges on today’s power system operation due to the intermittent nature and volatility of the wind and solar resources.High efficient large-scale electrical energy storage is one of the most effective and economical solutions to those problems.After the comprehensive review of the existing storage technologies,this paper proposes an overall design scheme for the Non-supplementary Fired Compressed Air Energy Storage(NFCAES)system,including system design,modeling and efficiency assessment,as well as protection and control.Especially,the design principles of the multistage regenerative,i.e.heat recovery system which is used to fully recycle and utilize the waste heat from compression are provided,so as the overall system efficiency evaluation method.This paper theoretically ascertains the storage decoupling rules in the potential and internal energy of molecular compressed air and reveals the conversion mechanism of gas,heat,power,electricity and other forms of energy.On this basis,a 500-k W physical simulation system of CAES system(TICC-500,Tsinghua-IPCCAS-CEPRI-CAES)is built,which passed a system-wide 420-k W load power generation test with less pollution and zero carbon emissions.Besides,the multi-form energy conversion of multi-stage regenerative CAES and storage efficiency is verified,especially its incomparable superiority in solving the uncertainty problem in wind and solar power generation.Finally,the propaganda and application scenario of the CAES system in China is introduced.

Energy saving potential of a fresh air pre-cooling system using radiative sky cooling

To achieve required indoor air quality,fresh air supply in buildings should meet relevant standards and regulations.However,the handling of fresh air introduced a cooling load that takes up a large portion of building energy consumption,especially in tropical and subtropical areas.A proper way should be employed to reduce the cooling load of fresh air.Radiative sky cooling,which is the process that an object cools itself by emitting thermal radiation to outer space without any energy input,is a cost-effective and eco-friendly technology.In this work,a fresh air pre-cooling system using radiative sky cooling is proposed to reduce fresh air cooling load.The system,consisting of filters,a radiative air-cooling system,an air handling unit(AHU),fans,etc.,is installed on the rooftop of the modeled building.Six cities in low-latitude areas are selected and investigated.Results show that with the radiative air-cooling system installed,annual cooling energy consumption of the modeled building can be reduced by around 10%in most cities.For arid areas,e.g.,Abu Dhabi,the system has even better performance with 19.34%annual cooling energy saving.

纺织空调绿色生产技术途径

探讨纺织空调实现绿色生产的途径和方法。针对纺织空调运行能耗高、耗水量大的问题,以创建绿色工厂为目标,从提高设备能效、优化空调热湿处理方法、加强运行调试与能源管理等方面提出具体要求和措施,并提出了细纱车间热分流、热回收、送回风系统低能耗运行的方法。认为:做好纺织空调节能降耗工作有助于实现纺织车间绿色生产。

太阳能驱动闭式转轮除湿空调系统性能研究

为解决传统开式转轮除湿空调系统再生排风能量浪费的问题,本文提出了可高效回收再生排风空气显热和潜热的太阳能驱动闭式转轮除湿空调系统,利用TRNSYS软件对系统进行建模,模拟研究了冷水流量比和新风比对系统性能的影响和系统动态性能,并对模拟的准确性进行实验验证。结果表明:模拟结果与实验结果的相对误差最大为±9.8%。太阳能驱动闭式转轮除湿空调系统的最优冷水流量比为1∶5∶4。系统在广州地区整个制冷季(6月1日—9月30日)平均电力COP_(e)为2.4,平均热力COP_(th)为2.1,累计取水量为25.66 t,热回收量为9.70 MW。相比于太阳能驱动开式转轮除湿空调系统,太阳能驱动闭式转轮除湿空调系统平均COP_(e)和COP_(th)分别提高42.1%和69.2%,CO_(2)排放量减少29.3%。

某调度通信楼空调系统节能减碳改造设计实践

重点介绍了某调度通信楼空调系统的节能减碳改造设计,通过综合运用余热回收、可再生能源、固体蓄热、高效制冷机房等多项技术,构建了安全可靠、绿色低碳、高效节能的空调系统。采用HDY-SMAD空调负荷计算及分析软件模拟了建筑物全年的空调能耗,并对优化前后空调系统的运行能耗和碳排放进行了测算。结果显示,优化方案空调系统全年节约电量100万kW·h,全年碳减排573 t,节能减碳效果显著。

空调新风系统需求响应潜力评估及影响因素研究

需求响应是保障电力供需平衡的重要措施,空调是重要的需求响应资源。空调新风负荷能耗占比高,但是基于室内二氧化碳浓度的新风负荷参与电力系统需求响应的潜力尚不清晰。该文以办公建筑新风系统为例,分别以单位小时能耗最低和全天电费最低为目标,提出了新风系统短期响应和全天响应策略,并建立了相应的响应潜力评估方法。研究结果表明:室内二氧化碳浓度惯性小,新风系统调节速度快,是优良的短期响应资源,单位小时能耗可削减20%~100%,人员密度越低,响应潜力越大,夏季尖峰电价时段平均可削减34%的新风负荷。以峰谷分时电价为响应信号,全天总运行费用可节省14%。在此基础上,进一步探究了室内二氧化碳浓度上限、人员密度、换气次数和气候区对新风负荷响应潜力的影响规律。新风柔性为建筑参与电网响应提出了新的解决方案,对于改善电力供需矛盾有较高的应用价值。

耦合液态乙烯冷能的液态空气储能系统热力学及经济性分析

液态空气储能(LAES)技术因其高储能密度和与外部能源的灵活耦合特性,成为了一种重要的大规模储能技术。构建了一种回收液态乙烯再气化废冷、引入外部低温热源的LAES系统。从热力学和经济性两方面对压缩机等熵效率、膨胀机等熵效率以及热源温度等系统关键参数进行分析,结果表明:当乙烯流量为34 t/h,储能容量可达5 MW/40 (MW·h);在90%的压缩和膨胀等熵效率下,仅依赖25℃的环境热源加热空气,往返效率为77.45%;当热源温度提升至125℃时,系统的最优往返效率、净现值及动态回收期分别达到了106.99%、14 473万元和3.56年。该研究结果能为LAES系统与外部冷能的耦合研究提供参考。

Design and analysis of a novel dual source vapor injection heat pump using exhaust and ambient air

A novel dual source vapor injection heat pump(DSVIHP)using exhaust and ambient air is proposed.The air exhausted from the building first releases energy to the medium-pressure evaporator and is then mixed with the ambient air to heat the low-pressure evaporator.A vapor injection(VI)compressor of two inlets is connected with the low and medium pressure evaporators.It’s first time that a VI compressor is employed to recover the ventilation heat.The system can minimize the ventilation heat loss and provide a unique defrosting approach by using the exhaust waste heat.Fundamentals of the proposed DSVIHP are illustrated.Mathematical models are built.Both energetic and exergetic analyses are carried out under variable conditions.The results indicate that the DSVIHP has superior thermodynamic performance.The superiority is more appreciable at a lower ambient temperature.It has a higher COP than the conventional vapor injection heat pump and air source heat pump by 11.3%and 23.2%respectively at an ambient temperature of-10°C and condensation temperature of 45°C.The waste heat recovery ratio from the exhaust air is more than 100%.The novel DSVIHP has great potential in the cold climate area application.