商场照明节能潜力及其对空调能耗的影响

分析了商场照明现状及其节能潜力,深入探讨了商场中央空调动态冷负荷的特征并指出照明对于空调冷源全年能耗的影响可达4 0 % ,说明高效照明措施对于照明节能和空调节能均具有重要意义。     

A review of novel thermal management systems for batteries

In the recent years, significant developments in the electric batteries have made them one of the most promising storage technologies for electrical energy. Among the various rechargeable batteries that are developed, lithium ion batteries stand out due to their capability of storing more energy per unit mass, low discharge rate, low weight, and lack of a memory effect. The advantages that batteries offer have promoted the development of the electric and hybrid electric vehicles. However, during charging and discharging processes, batteries generate heat. If this heat is not removed quickly, the battery temperature will rise, resulting in safety concerns and performance degradation. Thermal management systems are developed to maintain the temperature of the battery within the optimum operation range. This review paper focuses on novel battery thermal management systems (BTMSs). Air, liquid, phase change material, and pool‐based BTMSs are considered. Air‐based thermal management systems are discussed first. Liquid cooling systems and phase change‐based systems are discussed subsequently, and then the recently proposed evaporating pool‐based thermal management system is considered.     

Energy,exergy, and economical analyses of a photovoltaic thermal system integrated with the natural zeolites for heat management

In this study, the first time in the literature, natural zeolite has been employed for photovoltaic thermal (PVT) and experimentally tested as a thermal energy storage material. The main aim of the paper is to introduce natural zeolite as a heat storage material for PVT systems. The PVT systems integrated with phase change materials and natural zeolite were designed, the components of the system were explained, the thermodynamical modelling including the first and second laws was presented, the system performances were evaluated, performance parameters were investigated, energy and exergy efficiencies were determined, and economical analyses of each system were performed. Besides, all results were compared with a conventional PVT system. The average overall energy efficiency values for PVT experiments were 33% for paraffin, 37% for stearic acid, 40% for zeolite, and 32% for conventional PVT systems. The payback period of the PVT system with paraffin, zeolite, stearic acid, and conventional PVT was calculated as 10, 8, 9, and 9 years, respectively. The results show that the natural zeolite is a material with significant potential to be used for heat management in PVT for any meteorological condition.     

Analysis of the water and thermal management in proton exchange membrane fuel cell systems

Water and thermal management is essential to the performance of proton exchange membrane (PEM) fuel cell system. The key components in water and thermal management system, namely the fuel cell stack, radiator, condenser and membrane humidifier are all modeled analytically in this paper. Combined with a steady-state, one-dimensional, isothermal fuel cell model, a simple channel-groove pressure drop model is included in the stack analysis. Two compact heat exchangers, radiator and condenser are sized and rated to maintain the heat and material balance. The influence of non-condensable gas is also considered in the calculation of the condenser. Based on the proposed methodology, the effects of two important operating parameters, namely the air stoichiometric ratio and the cathode outlet pressure, and three kinds of anode humidification, namely recycling humidification, membrane humidification and recycling combining membrane humidification are analyzed. The methodology in this article is helpful to the design of water and thermal management system in fuel cell systems.     

Performance assessment of thermal management systems for electric and hybrid electric vehicles

Thermal management systems (TMS) are one of the key components of electric and hybrid electric vehicles to achieve high vehicle efficiency and performance under all operating conditions. Current improvements in electric battery technology allow vehicles to have relatively long ranges, fast acceleration, and long life while keeping low‐maintenance costs and considerably lower emissions. However, the vehicle performance is significantly affected by the battery operating conditions. Moreover, the cell life cycle, safety, and possibility of thermal runaway significantly depend on peak temperature rise and temperature uniformity of the battery. Therefore, various TMSs are created to keep batteries within ideal operating ranges. In this article, three different TMS systems—passive cabin cooling (via air), active moderate liquid circulation (via refrigerant), and active liquid circulation (via refrigerant and coolant)—are analyzed and compared with electric and hybrid electric vehicles. A second law analysis is used to examine the areas of low exergy efficiency in each system and minimize the entropy generation based on the system configuration. Moreover, TMS systems are compared on the basis of battery temperature increase and temperature uniformity. Various parametric studies are conducted to compare the TMS in different ambient and operating conditions. On the basis of the analysis, the active liquid circulation (via refrigerant and coolant) is determined to have the lowest battery temperature increase (3.9 °C in 30 min) and most cell temperature uniformity (2.5 °C median) as well as the lowest entropy generation rate (0.0121 W/K) among the compared systems. Copyright © 2012 John Wiley & Sons, Ltd.     

Numerical investigation of thermal and electrical management during hydrogen reversible solid-state storage using a novel heat exchanger based on thermoelectric modules

In order to reduce the costs generated by the hydrogen solid storage tank's accessories such as the heat exchanger, this work was carried out. It shows thermal and electrical investigations of transient hydrogen (H₂) solid storage in a tank filled with porous medium (LaNi₅) to activate a potential PEM automotive fuel cell. For this purpose, we use a novel heat exchanger with a heat sink combined with thermoelectric modules (TEMs). We realize a simulation that helps us verify if thermoelectric exchanger will be an alternative to the conventional ones. The main results are that a thermoelectric cooler and heater with 127 couples of semiconductors coupled with 19 fins heat sink could be used during the reversible hydrogen solid storage. Also, results show that we can avoid the water freezing at negative temperatures when using a conventional heat exchanger by using TEM during hydrogen absorption. Finally, during the endothermic desorption of the hydrogen, TEG use can avoid boiling water used in the heating system. Also, the hydrogen tank will be lighter and compact without fins and water tubes.     

Experimental investigation of thermal management system for lithium ion batteries module with coupling effect by heat sheets and phase change materials

Some potential safety risks for lithium ion battery such as overheating, combustion, and explosion occurred in practical application may cause accidents of electric vehicles. Phase change material (PCM)‐based thermal management system was demonstrated as a feasible approach. However, the batteries have to endure various environment and climate, which would not work normally under cold area. Especially when the surrounding temperature falls to below 10°C, which can bring about the energy and power of Li‐ion batteries rapidly reducing. In this study, a coupling heating strategy of the PCM‐based batteries module with 2 heat sheets at low temperature was proposed for batteries module and cannot only balance the temperature among different batteries in the module but also ensure to pre‐heat the batteries module at low temperature. The experiment displayed that 7% of EG in paraffin‐based composite PCMs was the best proportion for batteries module, considering both fluidity and thermal conductivity factors. In addition, the temperature difference of PCM‐based batteries module was 2.82°C, while that of the air‐based one was 14.49°C, which was 5 times more than former, exhibiting an excellent performance in balancing temperature uniformly, and was beneficial for prolonging the lifespan of batteries. The coupling heating strategy‐based PCM with heat sheets provided as an extremely promising technology for lithium batteries module at low temperature.