蓄热式热泵在空调系统中的应用

讨论了蓄热式热泵的工作原理、特点及设计方法 ,同时介绍了一个实际工程。指出使用蓄热式热泵既可充分合理利用能源 ,降低用户运行费用 ,又为电网提供了一种调荷避峰的好方式。     

Review of latent thermal energy storage systems for solar air-conditioning systems

Solar air conditioning is an important approach to satisfy the high demand for cooling given the global energy situation. The application of phase-change materials (PCMs) in a thermal storage system is a way to address temporary power problems of solar air-conditioning systems. This paper reviews the selection, strengthening, and application of PCMs and containers in latent thermal storage system for solar air-conditioning systems. The optimization of PCM container geometry is summarized and analyzed. The hybrid enhancement methods for PCMs and containers and the cost assessment of latent thermal storage system are discussed. The more effective heat transfer enhancement using PCMs was found to mainly involve micro-nano additives. Combinations of fins and nanoadditives, nanoparticles, and metal foam are the main hybrid strengthening method. However, the thermal storage effect of hybrid strengthening is not necessarily better than single strengthening. At the same time, the latent thermal storage unit has less application in the field of solar air-conditioning systems, especially regarding heat recovery, because of its cost and thermal storage time. The integration of latent thermal storage units and solar air-conditioning components, economic analysis of improvement technology, and quantitative studies on hybrid improvement are potential research directions in the future.     

蓄冰空调系统中分时蓄冷运行的应对策略研究

分时蓄冷方式主要是充分利用低谷电来制冰蓄冷,而在高峰时,以融冰供冷不开制冷机来满足空调负荷要求,真正起到在电网中削峰填谷的作用。分时蓄冷方法在融冰循环运行时,流量变化幅度大,情况特殊,因此需要系统有应对策略。     

A review on thermal energy storage systems in solar air heaters

The drying needs of agricultural, industrial process heat requirements and for space heating, solar energy is one of the prime sources which is renewable and pollution free. As the solar energy is inconsistent and nature dependent, more often there is a mismatch between the solar thermal energy availability and requirement. This drawback could be addressed to an extent with the help of thermal energy storage systems combined with solar air heaters. This review article focuses on solar air heaters with integrated and separate thermal energy storage systems as well as greenhouses with thermal storage units. A comprehensive study was carried out in solar thermal storage units consisting of sensible heat storage materials and latent heat storage materials. As the phase change heat storage materials offer many advantages over the sensible heat storage materials, the researchers are more interested in this system. The charging and discharging characteristics of thermal storage materials with various operational parameters have been reported. All the possible solar air heater applications with storage units have also been discussed.     

Dynamic response of power conditioning systems for superconductivemagnetic energy storage

The dynamic response of two power conditioning systems for superconductive magnetic energy storage (SMES) are presented. One power conditioning system is based on a hybrid current sourced inverter (CSI), the second is a combination of a DC chopper with a voltage sourced inverter (VSI). The response of both systems to a load change, a three phase fault, and start-up is presented     

Optimising PCM thermal storage systems for maximum energy storage effectiveness

A new performance parameter for PCM thermal storage systems, the energy storage effectiveness, is defined. This parameter can be used to optimise the design of any PCM thermal storage system to maximise the use of the thermal storage media. The paper presents results of a parametric study using an experimentally validated numerical model for PCM encapsulated in plates. The results are used to calculate the energy storage effectiveness which is ultimately used to optimise the useful energy that can be stored in the PCM thermal storage system. The energy storage effectiveness is also used to compare the useable storage capacity of the PCM relative to a sensible energy storage system.     

Review on solar air heating system with and without thermal energy storage system

In order to produce process heat for drying of agricultural, textile, marine products, heating of buildings and re-generating dehumidify agent, solar energy is one of the promising heat sources for meeting energy demand without putting adverse impact of environment. Hence it plays a key role for sustainable development. Solar energy is intermittent in nature and time dependent energy source. Owing to this nature, PCMs based thermal energy storage system can achieve the more popularity for solar energy based heating systems. The recent researches focused on the phase change materials (PCMs), as latent heat storage is more efficient than sensible heat storage. In this paper an attempt has been made to present holistic view of available solar air heater for different applications and their performance.     

Thermal storage in an air conditioning system with dual energy storage unit

在自行搭建的双蓄能实验平台上进行了制冷兼蓄热实验研究,对比了制冷兼蓄热模式和一般制冷模式,探讨了不同冷冻水流量和不同风机盘管风量对机组性能的影响.实验结果表明:蓄热对机组制冷端的影响很小,但是由于回收了大量的冷凝热,使得机组的综合能效比得到大幅提高,因此蓄热对空调节能具有较大作用.此外,在制冷兼蓄热模式下,冷冻水流量或风机盘管风量越大,机组的综合能效比越大,当风量为1033 m³/h,冷冻水流量为972 L/h时,机组综合能效比高达7.06.     

The thermodynamic effect of thermal energy storage on compressed air energy storage system

With the increasing penetration of renewable energy into energy market, it is urgent to solve the problem of fluctuations of renewable energy sources (RES). Energy storage technology is regarded as one method to cope with the unstable nature of RES. One of these technologies is compressed air energy storage (CAES), which is a modification of the basic gas turbine technology. Electric power supplied by CAES can meet peak-load requirement of electric utility systems. Because there is heat waste in the existing CAES systems during compression process, fossil fuels are used to improve the expansion work to generate peak power. In order to avoid the use of fuels and keep high efficiency of system, CAES system with thermal energy storage (TES) is designed to capture and reuse the compressed air heat. This paper uses a thermodynamic model of a CAES system with TES to analyze the effect of TES on system efficiency. Besides, this paper evaluates the influence of temperature and pressure on the utilization of heat in TES. Results show that even when power efficiency reaches maximum, there is still a proportion of thermal energy left in TES for other use. Meanwhile, the utilization of heat in TES can be affected by pressure in the air storage chamber. With appropriate selection of pressure limits, the utilization of compressed air heat can be optimized.     

Enthalpy estimation for thermal comfort and energy saving in air conditioning system

The thermal comfort control of a room must consider not only the thermal comfort level but also energy saving. This paper proposes an enthalpy estimation that is conducive for thermal comfort control and energy saving. The least enthalpy estimator (LEE) combines the concept of human thermal comfort with the theory of enthalpy to predict the load for a suitable setting pair in order to maintain more precisely the thermal comfort level and save energy in the air conditioning system.     

Analysis of cool storage for air conditioning

The paper investigates the thermal performance of ice-water cool storage systems theoretically and experimentally. Cool storage systems are used to shift electric demand from periods of high demand to those of low demand. A general lump model to determine the thermal storage characteristics is developed. The solution of the system equations is found through a Laplace transformation method. Experimental data of temperature profiles obtained for both single container and packet containers under the conditions of various flow rates and different inlet coolant temperatures confirm the validity of the theory. A closed form solution of the required time for latent-heat storage has also been established on the basis of the quasi-steady-state assumption of the coolant.     

地热空调的研究现状及应用前景

阐述了地热空调系统的结构原理与分类,着重介绍了地热空调技术在国内的研究现状,并分析了有关该系统的一些技术问题,认为其应用前景是广阔的。     

Second-law analysis of aquifer thermal energy storage systems

The application of exergy (second-law) analysis to aquifer thermal energy storage (ATES) systems is investigated in order to facilitate proper assessments of overall system performances. An elementary ATES model is created, and the corresponding expressions are developed for efficiencies and for the quantities of energy and exergy that are injected and recovered. It is demonstrated that ATES performance measures based on exergy often are more useful and meaningful than those based on energy. Exergy efficiencies account for the temperatures associated with energy transfers to and from an ATES, as well as the quantities of energy transferred, and consequently provide a measure of how nearly ATES systems approach ideal thermodynamic performance. Energy efficiencies do not provide a measure of approach to ideal performance and, in fact, are often misleadingly high because some of the energy recovered can be at too low a temperature to be available for a useful purpose.     

Review of mathematical modeling on latent heat thermal energy storage systems using phase-change material

Mathematical modeling of a latent heat thermal energy storage system (LHTES) was used for the optimum material selection and to assist in the optimal designing of the systems. In this paper, two types of models are mainly discussed, on the basis of first law and second law of thermodynamics. The important characteristics of different models and their assumptions used are presented and discussed, the experimental validation of some models are also presented.     

Pebble bed-oil thermal energy storage for solar thermo-electric power systems

Results of a study to examine the operating characteristics of a 100 kWh thermal energy storage (TES) system suitable for solar thermo electric applications is described. The system chosen consisted of a pebble bed as the primary storage medium and oil as the heat transfer cum storage medium. The operating temperatures considered were between 230 and 250°C with a 20 deg C swing. A full-size unit consisting of a steel tank of volume 10 m³ with 50 mm pebbles, suitable instrumentation and facility for heating the oil was built. The important operating variables and characteristics of the system studied included the transient behaviour of the bed, namely the thermal wave front characteristics. Results of the theoretical analysis of the transient bed behaviour were compared with the experimental data on the wave front propogation characteristics and the comparisons are discussed. The uniformity of flow distribution is also examined.     

Operation strategies guideline for packed bed thermal energy storage systems

Packed bed thermal energy storage (TES) systems have been identified in the last years as one of the most promising TES alternatives in terms of thermal efficiency and economic viability. The relative simplicity of this storage concept opens an important opportunity to its implementation in many environments, from the renewable solar‐thermal frame to the industrial waste heat recovery. In addition, its implicit flexibility allows the use of a wide variety of solid materials and heat transfer fluids, which leads to its deployment in very different applications. Its potential to overcome current heat storage system limitations regarding suitable temperature ranges or storage capacities has also been pointed out. However, the full implementation of the packed bed storage concept is still incomplete since no industrial scale units are under operation. The main underlying reasons are associated to the lack of a complete extraction of the full potential of this storage technology, derived from a successful system optimization in terms of material selection, design, and thermal management. These points have been evidenced as critical in order to attain high thermal efficiency values, comparable to the state‐of‐the‐art storage technologies, with improved technoeconomic performance. In order to bring this storage technology to a more mature status, closer to a successful industrial deployment, this paper proposes a double approach. First, a low‐cost by‐product material with high thermal performance is used as heat storage material in the packed bed. Second, a complete energetic and efficiency analysis of the storage system is introduced as a function of the thermal operation. Overall, the impact of both the selected storage material and the different thermal operation strategies is discussed by means of a thermal model which permits a careful discussion about the implications of each TES deployment strategy and the underlying governing mechanisms. The results show the paramount importance of the selected operation method, able to increase the resulting cycle and material usage efficiency up to values comparable to standard currently used TES solutions.     

The layer perovskites as thermal energy storage systems

A series of compounds of the general formula (n-C_nH_2n+1NH₃)₂MCl₄ (where M is a divalent metal atom and 8 n 18) undergoing high enthalpy reversible solid-solid phase transitions is considered. Although their transition enthalpy values are lower than those of the corresponding normal paraffins, the advantage of remaining solid after the phase change, together with other properties, makes these compounds of potential interest in the field of thermal energy storage systems.     

Review of flywheel energy storage systems for wind power applications

风力发电可以解决能源短缺和环境污染等问题,但由于风速随机性和间歇性的特点导致风电输出电压、功率和频率存在较大波动,因此风电的大规模并网会对现有电网的稳定运行造成不利影响。飞轮储能是一种高效无污染的储能技术,而且通过合理的控制策略和控制设备可实现电网调频及短时间调峰以解决大规模风电并网带来的问题。本文主要介绍了飞轮储能在风力发电领域的应用背景、飞轮储能的结构原理和目前国内外在飞轮储能控制策略方向的研究进展。     

Evaluation and selection of energy storage systems for solar thermal applications

Energy storage is one of the key technologies for energy conservation and therefore is of great practical importance. One of its main advantages is that it is best suited for solar thermal applications. This study deals with a comprehensive discussion of the evaluation and the selection of sensible and latent heat storage technologies, systems and applications in the field of solar energy. Several issues relating to energy storage are examined from the current perspective. In addition, some criteria, techniques, recommendations, checklists on the selection, implementation and operation of energy storage systems are provided for the use of energy engineers, scientists and policy makers. Copyright © 1999 John Wiley & Sons, Ltd.