A model-based optimal ventilation control strategy of multi-zone VAV air-conditioning systems

This paper presents a model-based optimal ventilation control strategy for multi-zone VAV air-conditioning systems aiming at optimizing the total fresh air flow rate by compromising the thermal comfort, indoor air quality and total energy consumption. In this strategy, one scheme is used to correct the total fresh air flow rate dynamically by utilizing the unvitiated fresh air from the over-ventilation zones based on the detected occupancy of each zone and the related measurements. At the meantime, another scheme is developed to optimize the temperature set point for the temperature control of critical zones with the aim at reducing the variation of the required fresh air fractions among all the zones and further reducing the total fresh air intake from outdoors for energy saving when the first scheme is implemented. This scheme is based on a constructed cost function relating thermal comfort, indoor air quality and total energy consumption together while the cost function is calculated based on the prediction of system responses using dynamic simplified models. Genetic algorithm is used for optimizing the temperature set point of critical zones in the optimization process. This strategy was evaluated in a simulated building and air-conditioning environment under various weather conditions.     

变风量空调系统中的实时优化节能控制

在对变风量空调系统局部控制的分析基础上,利用其变风量末端风门的开度作为各区域相对负荷的指示信号,提出送风静压的实时优化控制方案;同时,针对新的ＡＳＨＲＡＥ通风标准,还提出了基于室内人数检测和焓控制的新风实时优化控制方案。试验结果证明,同常规的控制方案相比,在保证室内热舒适性和空气质量的前提下,这两个方案分别有较好的节能作用。综合采用两种优化方案,系统不仅能够达到节能的目的,而且在较小负荷情况下能够提高室内空气的品质。     

Performance testing of an optimal photocatalytic mop fan air cleaning system

A novel photocatalytic mop fan air cleaning system has been developed. The novel mop fan system is optimized in terms of the pollutant degradation efficiency, energy consumption, appearance and cost reduction based on previous research. The fluid dynamic characteristic and energy consumption of the novel mop fan system has been identified by experimental testing. Pollutant degradation effect of the mop fan on a typical industry pollutant, diesel fume, has also been tested. It was found that the system has very low energy consumption and is very effective to destroy the diesel fume, a microparticulate pollutant. The system is suitable for any indoor environment to clean the air by removing the particulates, odors, virus, bacteria and volatile organic pollutants. Copyright © 2012 John Wiley & Sons, Ltd.     

M市供水泵站优化调度模型及应用

为降低城市供水泵站能耗、提高企业效益,以泵站运行费用最低为目标函数,建立泵站优化调度模型,使用遗传算法求解最优的水泵运行组合,在满足供水量与供水压力的前提下,使水泵均运行在高效段内,减少了能量浪费,并以M市供水系统为例测试了泵站优化调度模型,利用泵站优化调度程序优化了A、B水厂泵站的运行情况,并对比优化能耗与原运行状况的实际能耗。结果表明,A水厂节能效果不明显,B水厂节约能耗约为27.08%,两座水厂的总能耗低于优化前的能耗,节能约14.02%。泵站优化调度理论及其优化方案可在减少供水企业运营成本、提升供水企业服务和管理水平、改善管网水力条件等各方面发挥重要作用。     

Model-based optimal control of a dedicated outdoor air-chilled ceiling system using liquid desiccant and membrane-based total heat recovery

This study presents a model-based control strategy for a novel dedicated outdoor air-chilled ceiling (DOAS-CC) system with the aim of optimizing the overall system performance. The DOAS-CC system incorporates liquid desiccant dehumidification and membrane-based total heat recovery technologies. Simplified but reliable models of major components in the DOAS-CC system are firstly developed to predict the system performance. A cost function is then constructed to minimize total energy consumption while properly maintaining thermal comfort reflected by indoor air temperature and relative humidity. Genetic algorithm is used to search for optimal set-points of the supply air temperature and humidity ratio of the dedicated outdoor air subsystem as well as the supply water temperature. The performance of this strategy is tested and evaluated with different control settings in a simulated multi-zone space served by the DOAS-CC system under various weather conditions. The results show that optimized control variables produced by the optimal strategy can improve the system energy performance and maintain indoor thermal comfort.     

Fan pressure-based testing,adjusting, and balancing of a ventilation system

Ventilation systems are responsible for the thermal comfort and air quality of indoor spaces. The adjustment of ventilation systems is a time-consuming task that may need multiple iterations. Incorrect adjustments of a ventilation system can reduce the quality of working and living conditions and degrade the energy efficiency of the ventilation. In this paper, a testing, adjusting, and balancing method for a ventilation system is presented that uses only the knowledge of the fan total flow rate and pressure. The method does not need additional instrumentation for the ventilation adjustment as the fan operating point can be estimated with the variable-speed drive. The method is noniterative, thereby saving time, and the ventilation system is adjusted to its minimum energy consumption setting without compromise in system operation. The proposed method is assessed with a laboratory test setup to verify the correct operation of the method in practice.     

A cost‐effective operating strategy to reduce energy consumption in a HVAC system

The operation of the building heating, ventilating, and air conditioning (HVAC) system is a critical activity in terms of optimizing the building's energy consumption, ensuring the occupants' comfort, and preserving air quality. The performance of HVAC systems can be improved through optimized supervisory control strategies. Set points can be adjusted by the optimized supervisor to improve the operating efficiency. This paper presents a cost‐effective building operating strategy to reduce energy costs associated with the operation of the HVAC system. The strategy determines the set points of local‐loop controllers used in a multi‐zone HVAC system. The controller set points include the supply air temperature, the supply duct static pressure, and the chilled water supply temperature. The variation of zone air temperatures around the set point is also considered. The strategy provides proper set points to controllers for minimum energy use while maintaining the required thermal comfort. The proposed technology is computationally simple and suitable for online implementation; it requires access to some data that are already measured and therefore available in most existing building energy management and control systems. The strategy is evaluated for a case study in an existing variable air volume system. The results show that the proposed strategy may be an excellent means of reducing utility costs associated with maintaining or improving indoor environmental conditions. It may reduce energy consumption by about 11% when compared with the actual strategy applied on the investigated existing system. Copyright © 2007 John Wiley & Sons, Ltd.     

Hierarchical fuzzy control of low-energy building systems

A hierarchical fuzzy supervisory controller is described that is capable of optimizing the operation of a low-energy building, which uses solar energy to heat and cool its interior spaces. The highest level fuzzy rules choose the most appropriate set of lower level rules according to the weather and occupancy information; the second level fuzzy rules determine an optimal energy profile and the overall modes of operation of the heating, ventilating and air-conditioning system (HVAC); the third level fuzzy rules select the mode of operation of specific equipment, and assign schedules to the local controllers so that the optimal energy profile can be achieved in the most efficient way. Computer simulation is used to compare the hierarchical fuzzy control scheme with a supervisory control scheme based on expert rules. The performance is evaluated by comparing the energy consumption and thermal comfort.     

Air cooling strategy of power battery based on minimum energy consumption

针对目前电动汽车动力电池风冷散热能耗高、散热滞后的问题,提出一种基于最小能耗的动力电池风冷控制策略,根据车载导航系统预报的工况信息预测动力电池的未来温升,在满足动力电池散热需求的前提下以风机能耗最少为目标,运用分段式动态规划算法确定风机在未来路段的开启时机与最优风速。以添加了坡度信息的ARB02、HWFET和UDDSHDV的组合工况为测试工况,对动力电池未来温升的精度进行了硬件在环试验,得出实际路况试验温度与预报工况试验温度的最大差值为0.3℃,最大偏差率为0.7%。与其他两种控制策略进行了Fluent仿真对比,结果表明基于最小能耗控制策略下动力电池的最高温度为39.87℃,最大温差为1.1℃;风机能耗是全程开启型控制策略的77.2%,是温度开关型控制策略的53.7%。该策略能有效控制动力电池的温度且风机能耗最小。     

Inherent correlation between the total output cooling capacity and equipment sensible heat ratio of a direct expansion air conditioning system under variable-speed operation (XXG SMD SHR DX AC unit)

Appropriately controlling indoor air humidity at a suitable level in buildings is important. To simultaneously control both indoor air dry-bulb temperature and relative humidity requires the match between the total output cooling capacity of an A/C system and the total cooling load in a space served by the A/C system, as well as the Equipment sensible heat ratio (SHR) of the A/C system and the Application SHR of the conditioned space. This paper reports on an experimental study on the inherent correlations between the total output cooling capacity and Equipment SHR of a DX A/C system. Experiments were carried out under different combinations of compressor speed and supply fan speed, and also under different inlet air conditions to the DX evaporator. The results obtained would lead to a better understanding of the operating characteristics of a DX A/C system under variable-speed operation, as well as the constraint of using these characteristics in developing appropriate control strategies, so as to better design, operate and control DX A/C systems for improved indoor thermal environmental control.     

含能效电厂的输电网不确定性规划方法

在全球能源互联网背景下,负荷不断增加、能源消耗增多、环境污染严重给输电网规划带来诸多挑战。为此,在输电网规划中引入能效电厂,建立含能效电厂的多阶段输电网不确定性二层规划模型,其上层模型以总投资成本最小为目标函数,下层模型以N、N-1运行条件下的切负荷量最小为目标函数,就可保证上层模型所得最优规划方案的可靠性。结合改进小生境遗传算法和原始—对偶内点法两种算法的优点对所提模型进行求解,进而得到规划的最优结果。以IEEE-RTS 24节点系统为例,验证了所提方法的有效性和实用性。     

燃料电池汽车高压供氢系统辅助供冷仿真

通过数值模拟的方法,从稳态和驾驶循环2种工况对供氢系统辅助供冷方案进行评价。仿真结果表明：氢气的高膨胀比有利于空调系统能耗的下降。当环境温度为45 ℃,在中国乘用车驾驶工况下,辅助供冷方案可使空调系统能耗下降5.4%。但辅助供冷方案会给空调系统的稳定运行和座舱温度的控制带来一定的挑战。     

Optimisation of night-time ventilation parameters to reduce building's energy consumption by integrating DOE2 and MATLAB

We have developed an algorithm to optimise the fan flow rate by integrating DOE2 (building's energy simulation software) with MATLAB's genetic algorithm. In our developed algorithm, MATLAB can send desired values of optimisation variables for different hours to DOE2 to simulate building's energy use, and it can also receive building's energy consumption and other data from DOE2 for the optimisation. This powerful optimisation tool can be used for finding optimal solution of night-time ventilation fan flow rates and maximising energy savings. Results of optimisation are used to train a neural network to predict fan flow rates for different conditions. Night-time ventilation investigated in DOE2 considers parameters such as (1) night-time ventilation duration, (2) ventilation fan flow rate, (3) outdoor temperature, and (4) temperature difference between outdoor and indoor. Optimisation results show outdoor temperature between 10°C and 18°C and the temperature difference of more than 8°C are appropriate for night-time ventilation.     

Indoor thermal comfort characteristics under the control of a direct expansion air conditioning unit having a variable-speed compressor and a supply air fan

Indoor thermal environment is important as it affects the health and productivity of building occupants. Direct expansion (DX) air conditioning (A/C) units are commonly used for environmental control in small- to medium-scaled buildings. This paper reports on an experimental study to investigate the indoor thermal comfort characteristics under the control of a DX A/C unit having variable-speed compressor and supply fan at a fixed space cooling load but having three different ratios between its sensible part and latent part. The experimental results suggested that under a fixed indoor total cooling load with three different space sensible heat ratios (SHRs) of 0.92, 0.72 and 0.62, varying both speeds of compressor and supply fan in the DX A/C unit would influence indoor thermal comfort. Furthermore, when a DX A/C unit having variable-speed compressor and supply fan is used for indoor thermal comfort control under abnormal indoor load conditions, its ability of indoor thermal comfort control through varying compressor speed and supply fan speed may be duly restricted.     

钻井平台温控风机研制及节能评价

根据目前钻井平台风机运行中存在的能源浪费的现状,提出了在保障安全前提下的风机温控方案,并开展设备研制,在钻井平台上成功应用。对温控风机系统的能耗监测表明该系统起到了预期的节能效果,为钻井平台技术节能提供了实施案例。     

计及天然气压力能的微电网储荷协调优化调度

为解决天然气输送过程中压力能的浪费问题,提高天然气能源利用率,提出将天然气压力能发电系统引入至微电网整体调度方案中。针对天然气压力能发电系统中前后端口的补热需要,将微电网中的风冷热泵补热系统与压力能发电系统进行耦合。考虑到由天然气管网中流量波动和环境因素造成的压力能出力波动问题,提出微电网储荷一体化协调优化方案,以确保系统高效稳定运行。基于上述内容,构建考虑可控电源出力成本、储能调度成本、微电网与配电网的交互成本和负荷调度成本的微电网优化调度模型,并采用Yalmip工具包编写优化调度程序。最后,通过对西南地区某调压站数据进行仿真,验证该方案的可行性与经济性。     

Heating energy performance and part load ratio characteristics of boiler staging in an office building

Commercial buildings account for significant portions of the total building energy in South Korea and thus a variety of research on the boiler operation related to heating energy in office buildings has been carried out thus far. However, most of the researches have been conducted on the boiler itself, i.e., the part load ratio characteristics and the corresponding gas energy consumption patterns are not analyzed in the existing studies. In this study, the part load ratio and the operating characteristics of gas boiler have been analyzed within an office building equipped with the conventional variable air volume system. In addition, the gas consumption among different boiler staging schemes has been comparatively analyzed. As a result, significant portions of total operating hours, heating load and energy consumption has been found to be in a part load ratio range of 0 through 40% and thus energy consumption is significantly affected by boiler efficiency at low part load conditions. This suggests that boiler operation at the part load is an important factor in commercial buildings. In addition, utilizing sequential boiler staging scheme can save a gas usage of about 7%. For annual heating energy saving, applying the sequential control boiler with a 3:7 proportion staging is considered to be the optimal control algorithm for maximum efficiency of boilers.     

厂级AGC机组负荷优化分配系统研究

针对我国目前电网的调度模式,提出了在自动发电控制(AGC)方式下的厂级负荷优化分配系统实现方案,该方案不改变电厂原有网络结构,直接在厂级监控信息系统中增加负荷控制节点,这样既不改变控制系统原有的各项功能,又使厂级负荷控制的投切比较灵活,大大增强了系统的稳定性。在优化算法上提出了遗传禁忌混合算法,以某电厂的3台机组为例,采用2008年负荷数据进行优化分配,并与实际分配进行对比,结果表明采用该算法进行优化分配后煤耗率下降了0.2g/(kW.h)～5.3g/(kW.h),对电厂节能降耗,提高经济效益有重要意义。     

Maximum power point traking controller for PV systems using neural networks

This paper presents a development and implementation of a PC-based maximum power point tracker (MPPT) for PV system using neural networks (NN). The system consists of a PV module via a MPPT supplying a dc motor that drives an air fan. The control algorithm is developed to use the artificial NN for detecting the optimal operating point under different operating conditions, then the control action gives the driving signals to the MPPT. A PC is used for data acquisition, running the control algorithm, data storage, as well as data display and analysis. The system has been implemented and tested under various operating conditions.The experimental results showed that the PV system with MPPT always tracks the peak power point of the PV module under various operating conditions. The MPPT transmits about 97% of the actual maximum power generated by the PV module. The MPPT not only increases the power from the PV module to the load, but also maintains longer operating periods for the PV system. The air velocity and the air mass flow rate of the mechanical load are increased considerably, due to the increase of the PV system power. It is also found that, the increase in the output energy due to using the MPPT is about 45.2% for a clear sunny day.     

供水泵站变频调速系统节能运行研究

为了探究供水泵站变频调速系统的最佳节能运行方式,以单方水耗电量为考核目标,通过对供水系统工作原理的分析,并以供水泵站设备及系统实测数据为依据,利用Matlab软件拟合数学方程及曲线,以沧州泊头供水泵站为例,分析了供水系统能量损失原因及能量损失分布情况,提出了相同工况不同运行方式下的效率模型,计算并比较不同方案的单方水耗电量,确定了最佳运行方案。结果表明,相同工况下选择最优运行方案可达到提高供水效率,降低能耗的目的。