An ice thermal storage computer model

In hot humid countries such as Thailand, air conditioning plant is installed in most commercial and industrial buildings. A conventional air conditioning system, which is normally operated when cooling is required, is the most favored option. Ice thermal storage on a large scale, used to provide a cool reservoir for use in peak periods, is however an attractive financial option for large buildings to supply coolness. There are two means of operating ice thermal storage systems, namely full storage and partial storage.In this paper, a computer model has been developed in order to compare energy use in conventional air cooling systems and ice thermal storage systems. Under Thailand electricity tariff rates, the results from the simulations show that the full ice thermal storage can save up to 55% of the electricity cost required for cooling per month when compared with the conventional system. It is also found that using full storage option can reduce the total energy consumption by 5% for the selected building.     

Use of liquid desiccant cooling to improve the performance of vapor compression air conditioning

A hybrid air conditioning system, which consists of sections of desiccant dehumidification, evaporative cooling and vapor compression air conditioning, has been established in this paper. Experimental investigation demonstrates that cooling production and COP of the new hybrid system can be increased significantly, if they are compared with those of vapor compression system (VCS) alone. Assuming that the outlet temperature and humidity of the system are constant, psychrometric analysis at ARI conditions has been conducted under three different cases. The benefits are represented by lower electricity consumption of the compressor, higher COP of the system, less flow rate of condensation air, and reduced size of VCS, etc. The reason that the hybrid system is superior in performance to conventional systems lies in that desiccant dehumidification and evaporative cooling changes the inlet states of the air entering into VCS. Furthermore, the effects of dehumidification and evaporative cooling are analyzed in the paper.     

The use of deep water cooling systems: Two Canadian examples

Deep water cooling involves using naturally cold water as a heat sink in a heat exchange system, eliminating the need for conventional air conditioning. The cold water is drawn from near the bottom or below the thermocline of a nearby water body. In this study Canadian deep water cooling systems in Halifax, Nova Scotia and Toronto, Ontario were documented. The expected economic and environmental benefits were realized, but barriers to large-scale adoption of the technology were apparent. This technology requires that a client with a large cooling need is near a deep, cold body of water, and payback times vary depending on the site. The public–private partnership approach proved to be beneficial in these two examples, and the Toronto approach in which many buildings are serviced at once by combining municipal pumping capacity can deliver cost savings on a shorter time span. Deep water cooling represents a successful example of a niche accumulation process and an example of electricity demand displacement. Many other locations in which heavy air conditioning users are located next to deep, cold water bodies could use this technology; several such sites exist in Canadian urban areas.     

A review on solar cold production through absorption technology

Recently, the traditional energy types have failed to satisfy the human needs because of their limited quantity as well as their negative environmental impacts. Conventional cold producing machines that are based on vapor compression principle are primary electricity consumers and their working fluids are being banned by international legislation. From this perspective, solar powered cooling systems as a green cold production technology are the best alternative. Absorption refrigeration is a mature technology that has proved its applicability with the possibility to be driven by low grade solar and waste heat. In this study, we present a comprehensive literature review on absorption based refrigeration and air conditioning systems that are powered by solar energy. Various systems along with their thermodynamic operating principle are presented. Moreover, the previous experimental and numerical simulation studies for these systems are discussed.     

复合式太阳能空调优化方案

出了融除湿、蒸发冷却、压缩制冷及太阳能热水为一体的复合式太阳能空调的优化方案。分析比较了三种空气处理方案。结果表明 ,与常规空调相比 ,优化方案节电近 4 7%。     

The impact of climate change on the electricity market: A review

Climate change will impact electricity markets through both electricity demand and supply. This paper reviews the research on this topic. Whereas there is much that remains unknown or uncertain, research over the last few years has significantly advanced our knowledge. In general, higher temperatures are expected to raise electricity demand for cooling, decrease demand for heating, and to reduce electricity production from thermal power plants. The effect of climate change on the supply of electricity from non-thermal sources shows great geographical variability due to differences in expected changes to temperature and precipitation. Whereas the research frontier has advanced significantly in the last few years, there still remains a significant need for more research in order to better understand the effects of climate change on the electricity market. Four significant gaps in the current research are regional studies of demand side impacts for Africa, Asia, the Caribbean and Latin America, the effects of extreme weather events on electricity generation, transmission and demand, changes to the adoption rate of air conditioning, and finally, our understanding of the sensitivity of thermal power supply to changes in air and water temperatures.     

Influence of different outdoor design conditions on design cooling load and design capacities of air conditioning equipments

Outdoor design conditions are important parameters for energy efficiency of buildings. The result of incorrect selection of outdoor design conditions can be dramatic in view of comfort and energy consumption. In this study, the influence of different outdoor design conditions on air conditioning systems is investigated. For this purpose, cooling loads and capacities of air conditioning equipments for a sample building located in Adana, Turkey are calculated using different outdoor design conditions recommended by ASHRAE, the current design data used in Turkey and the daily maximum dry and wet bulb temperatures of July 21st, which is generally accepted as the design day. The cooling coil capacities obtained from the different outdoor design conditions considered in this study are compared with each other. The cost analysis of air conditioning systems is also performed. It is seen that the selection of outdoor design conditions is a very critical step in calculation of the building cooling loads and design capacities of air conditioning equipments.     

Energy and fuel consumption forecast by retrofitting absorption cooling in Malaysia from 2012 to 2025

Electricity demand in residential and commercial sectors has increased steadily over the past 50 years in Malaysia. The bulk of which is being consumed by air conditioning systems. Absorption cooling systems can be a reasonable alternative to have conditioned spaces in the country. The fuel consumption to produce electricity for cooling purposes in residential and commercial sectors has been forecasted from 2012 to 2025. The paper also investigates the effect of applying five different scenarios on energy and fuel consumption by retrofitting absorption chillers instead of conventional cooling systems. This study found that the consumption of natural gas will be raised by increase in utilized absorption chillers however, the consumption of different fuels such as coal, diesel and fuel oil will decrease in thermal power plants.     

A review on solar-powered closed physisorption cooling systems

Cooling, refrigeration, and air conditioning processes are considered essential needs and major requirements for all human beings in our world today. However, the traditional vapor compression machines are dominating electricity consumers and their operation and propagation cause high electricity peak loads during the summer, especially in those countries with tropical climate. That is besides their refrigerants having high global warming as well as ozone layer depletion potentials. Providing cooling by utilizing a green energy such as solar energy is the key solution to electricity and pollution problems. Adsorption refrigeration systems that are driven by solar energy are mature technologies. They are proven to be suitable and applicable for refrigeration as well as air-conditioning applications. Solar adsorption cooling technology is divided into physisorption and chemisorption systems. The physisorption machines include open and closed cycle operation. This paper presents a review on previous researches and developments of the solar driven closed physisorption refrigeration systems. The discussion includes, experimental and numerical simulation studies as well as methods that are suggested to improve the system performance.     

水上和水下提取次表层海水冷量的对比和分析

夏季的酷热迫使人们耗费大量能源以维持狭窄的温度环境,城市空调负荷节节攀升;近在身边的海中,表层以下巨大的水团静静地安卧,闲置着天然的冷量.冷媒水与海水在海中进行换热,是实现水下直接提取海洋冷量的构想.与陆上提取冷量方案的对比,可以证明其技术优势和节能效果.水下取冷方案甚至可应用于高盐度海区,并提高海水与冷媒水的换热温差,以提升海水冷量利用率;采用自来水作为冷媒水,不需要对海水进行处理,也不会出现管道堵塞的故障;作为空调系统回水的自来水,又可用作其它工业或生活用途.该方案在提供相同冷媒水流量的条件下,输水耗功减少幅度达到90%.     

Solar operated absorption air-conditioner for a Kufra house

The use of solar energy for domestic water heating and space heating has proved to be viable. Space cooling is another promising avenue for utilization of solar energy. Solar operated absorption air-conditioning systems, in different situations, have been found to be feasible. Such systems can make use of the expensive collectors which are, in any case, installed for water and space heating.

In this paper the cooling of a prototype house, in Kufra, is reported. Starting with measured radiation and ambient data, calculations are performed on an hourly basis to determine the cooling load, radiation in the collector plane, heat delivered by the collectors and the heat stored in or discharged from the storage tank. Three different types of collectors with varying efficiencies are considered. These collectors are of the evacuated tube, selective coated and black painted types. The study confirms that the water-lithium bromide absorption system can provide summer air conditioning in arid zones of Jamahiriya where there are diffuclties with the supply of electricity and fossil fuels.     

Need for thermal-storage air-conditioning in Saudi Arabia

In Saudi Arabia, the growth of demand for electrical energy in the rapidly expanding towns, cities and industries, far exceeds the growth of the power being made available. Recently the Saudi Consolidated Electric Companies (SCECO) are facing a shortage of electricity during the summer period mainly due to the high consumption of electricity in the air conditioning sector. The incorporation of thermal energy storage (TES) technologies with a conventional air conditioning system is found to be an appropriate solution for energy-demand management. In this paper an introductory overview of thermal storage air conditioning is presented, comparing phase change (e.g. ice) and sensible heat (e.g. chilled water) storage technologies. The pros and cons of each are evaluated. The suitability of TES technology for the Saudi HVAC (heating, ventilating and air conditioning) industry is explored with the benefits to the owner such as: reduced energy consumption; less operation and maintenance costs; and downsizing of the chiller plant and system for new facility; alternative to new chiller installation to cater for increased cooling load; and stored water as a fire protection source. Furthermore, an economic study has been presented to illustrate the feasibility of TES based air conditioning in Saudi Arabia.     

表冷器热工性能数值模拟的探讨

表冷器是空调机组的核心部件,通常的热性能计算都以试验为基础。提出一种数值模拟方法,从最基本的结构参数来计算表冷器的热性能。按此方法所编制的计算程序经过试验验证,已经取得了预期的效果。     

Methodology for the economic evaluation of gas turbine air cooling systems in combined cycle applications

During the last decades, gas turbines (GT) have been widely used to produce electricity power. Despite their numerous applications, one of the most important shortcomings affecting GT behaviour is their power output decrease at higher air ambient temperatures. This problem is frequently solved by installing air cooling systems at GT inlet as a proper alternative in order to stabilise GT power output.Although maximising power output has been usually considered as the main objective of the cooling system, economical profits should also be considered, replacing the usual power increase as the main strategy to select the most suitable temperature. Moreover, especially when electricity markets tend to a deregulated scenario and its prices are settled by a pool system. Hence, an accurate methodology needs to be developed to analyse and compare the different alternatives, including the time-dependent variables involved in the technical and economical system behaviour. These variables include: ambient temperature, relative humidity, hourly electricity prices and natural gas tariff.The proposed methodology takes into account the performance simulation at the combined cycle, the air cooling system, ambient conditions, equipment maintenance and investment, and electricity and natural gas prices, in order to obtain cash flows and another relevant economical variables that maximise the profit of the integrated system. In this paper, this method has been applied as an example to a three-level-pressure combined cycle model with different GT inlet air cooling systems in a certain location and economical framework. The proposed method allows a better results interpretation, showing that some cooling systems, appearing as a proper alternative from a historical point of view, are not necessarily the most profitable option. Consequently, the proposed methodology for the economic evaluation of the cooling systems offers more straightforward information that allows the cooling equipment technology to be sized or selected.     

An analysis of the heat transfer rate and efficiency of TE (thermoelectric) cooling systems

The heat transfer rate and efficiency of TE (thermoelectric) cooling systems were investigated. The emphasis of the present study is focused on the use of large-scale TE refrigerators for air conditioning applications. A one-dimensional heat transfer analysis was performed to determine the cooling power and electricity consumption of the TE elements. The constant-property results are in good agreement with the variable-property solutions for TE materials and temperatures typical for air conditioning applications. A heat transfer analysis was also carried out for TE refrigerators equipped with a heat exchanger. Both parallel- and counter-flow heat exchangers were considered. Fluid temperature variations of these two flow arrangements were found to be quite different, but the efficiencies and cold fluid exit temperatures differed only slightly when a uniform current was used for all TE elements. If the length of the heat exchanger exceeds an optimal value, the cold fluid temperature begins to rise and the efficiency drops for both parallel- and counter-flow arrangements. The second law of thermodynamics was applied to the optimization of TE refrigerators operating between two constant-temperature reservoirs and between two flowing fluids. It was found that if a TE cooling system incorporates a heat exchanger, a nonuniform current distribution should be used to achieve the maximum efficiency and the lowest cold fluid temperature. The optimization results for TE refrigerators operating between two constant-temperature reservoirs are not applicable to TE cooling systems between two flowing fluids. The most energy-efficient current distribution for the parallel-flow arrangement is the one which increase in the direction of the cold fluid.     

Air conditioning market saturation and long-term response of residential cooling energy demand to climate change

Existing state-level models relating climate parameters to residential electricity consumption indicate a nominal sensitivity of 2–4% for each degree Celsius increase in ambient temperatures. Long-term climate change will also impact electricity consumption through corresponding increases in the market saturation of air conditioning. In this paper we use air conditioning market saturation data for 39 US cities to develop a generalized functional relationship between market saturation and cooling degree days. The slope of this saturation curve is particularly high for cities that currently have low to moderate saturation. As a result, the total response of per capita electricity consumption to long-term warming may be much higher than previously thought. A detailed analysis of 12 cities in four states shows that for some cities changes in market saturation may be two to three times more important than the role of weather sensitivity of current loads. While actual behavioral response to climate change will be more complicated than that captured in our model of market saturation, this approach provides a new perspective on the sensitivity of space conditioning electricity consumption in the US to climate change.     

Determination of free cooling potential: A case study for İstanbul,Turkey

A significant portion of energy consumed in buildings is attributed to energy usage by heating, ventilating and air conditioning (HVAC) systems. Free cooling is a good opportunity for energy savings in air conditioning systems. With free cooling, commonly is known economizer cycle, the benefits of lower ambient temperatures are utilized for a significant proportion of the year in many climates. The detailed analysis of local weather data is required to assess the benefits of economizer. In this study, free cooling potential of ?stanbul, Turkey was determined by using hourly dry-bulb temperatures measurements during a period of 16 years. It is found that the free cooling potential varies with supply air temperature and months. It is determined that although there are substantial energy savings during a significant portion of the year especially in transition months (April, May, September and October), the high outdoor air temperatures from June to August, made the system not beneficial for free cooling except at high supply air temperature.     

Parametric analysis of space cooling systems based on night ceiling cooling with PCM‐embedded piping

A parametric analysis is conducted for space cooling systems based on cold water flowing, during the night, within regularly arranged pipes embedded in a layer of phase change material (PCM), located among the structural layers of the ceiling. The introduced PCM layer in conjunction with night cooling add to the usual ceiling cooling systems offers the advantages of low energy consumption, high cool storage capacity, operation under reduced night electricity price, smoothing of electricity consumption by eliminating daily peak loads, improved thermal comfort and elimination of ceiling dripping. Our parametric analysis is based on a transient three‐dimensional finite‐difference solution of the related heat‐transfer problem for various values of all the main system parameters. PCM phase change process is simulated by using the effective thermal capacity function, which is determined experimentally for PCM suitable for air‐conditioning applications. Our tests showed that the main parameters of the system are pipe spacing, PCM layer thickness, pipe depth within the ceiling, cooling water inlet temperature, night cooling duration and PCM properties (thermal conductivity, phase change heat and ends of phase change temperature range). The effect of all the above parameters is analysed and suggestions are made for selecting the proper combinations of their values in order to obtain the lowest energy consumption in conjunction with the highest level of thermal comfort. Copyright © 2010 John Wiley & Sons, Ltd.     

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。