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The Study Paper on Solar Absorption Air-Conditioning Systems

Essay by   •  February 11, 2012  •  Case Study  •  2,303 Words (10 Pages)  •  1,731 Views

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Title: The study paper on solar absorption air-conditioning systems

Abstract

An environmental control system utilizing solar energy would generally be more cost-effective if it were used to provide both heating and cooling requirements in the building it serves. Various solar powered heating systems have been tested extensively, but solar powered air-conditioners have received little more than short-term demonstration attention. Solar powered absorption cooling systems can serve both heating and cooling requirements in the building it serves. Many researchers have studied the solar absorption air conditioning system in order to make it economically and technically viable. A number of attempts have been made by researchers to improve the performance of the solar applied air-conditioning subsystems. . This study paper will help many researchers working in this area and provide them with fundamental knowledge on absorption systems, and a detailed review on the past efforts in the field of solar absorption cooling systems with the absorption pair of lithium-bromide and water.

Keywords: Absorption chiller; Air-conditioning; Lithium bromide and water; Solar energy etc

Introduction

Air-conditioning is a particularly attractive application for solar energy because of the near coincidence of peak cooling loads with the available solar power. Many arrangements or cycles are possible. solar collectors can be used to provide energy for absorption cooling, desiccant cooling, Although a large potential market exists for this technology, existing solar cooling systems are not competitive with electricity-driven or gas-fired air- conditioning systems because of their high first costs. Lowering the cost of components and improving their performance could reduce the cost of solar cooling systems. Improvements such as reduced collector area, because of improved system performance, and reduced collector cost will lower the cost of solar components. The performance coefficient of an absorption air-conditioner, defined as the ratio of the heat transfer rate into the evaporator to the heat transfer rate into the generator, can be calculated as a function of the temperatures identified previously. Solar energy is one of the most available forms of energy on the Earth's surface, besides; it is very promising and generous. The earth's surface receives a daily solar dose of 10E+8 KW-hr, which is equivalent to 500 000 billion oil barrels that is one thousand times any oil reserve known to man. The solar energy is collector area dependent, and is a diluted form of energy and is available for only a fraction of the day. Also, its availability depends on several factors such as latitude and sky clearness. At the same time, its system requires high initial cost. But on the other hand, it has some attractive features such as its system requiring minimum maintenance and operation cost, and it does not have negative effects on the environment. Another important feature of solar energy is its ability to satisfy rural areas where conventional energy systems might be not suitable or uneconomical.

Literature survey

Charters and Chen [1] had made a comparison study on air-cooled and water-cooled systems. In January 1998, a solar powered two-stage absorption air-conditioning system was installed in China [2].The system has a cooling power of 100 kW, with collector areas of 500 m2. The nominal generating temperature of the chiller is about 65-750C, and the COP of the chiller is greater than 0.4. This kind of machine was originally suggested by Tanaka, it was first installed at a new building of the Energy Engineering Department of Oita University, Kyushu [3]. After successful operation for a two-year test period, the solar air-conditioning system was operated with steam as the auxiliary fuel. The identical single-double effect absorption chiller was also operated at the Kabe Office Building of the Chugoku Electric Company in Hiroshima.

Fig1.1 Basic structure of a solar air conditioning system

This is where solar air conditioning comes in: The summer sun, which heats up offices, also delivers the energy to cool them. The thermal use of solar energy offers itself: Days that have the greatest need for cooling are also the very same days that offer the maximum possible solar energy gain.

The demand for air conditioning in offices, hotels, laboratories or public buildings such as museums is considerable. This is true not only in southern Europe, but also in Germany and middle Europe. Under adequate conditions, solar and solar-assisted air conditioning systems can be reasonable alternatives to conventional air conditioning systems. This Solar-Report will briefly inform you over the possibilities and technology of solar air conditioning and will also cover economic aspects.

Methods

1) Single effect solar absorption air-conditioning system.

2) Double-effect solar absorption air-conditioning system

Single effect solar absorption airconditioning system.

To begin with, the solar energy is gained through the collector and is accumulated in the storage tank. Then, the hot water in the storage tank is supplied to the generator to boil of water vapor from a solution of lithium bromide and water. The water vapor is cooled down in the condenser and then passed to the evaporator where it again is evaporated at low pressure, thereby providing cooling to the required space. Meanwhile, the strong solution leaving the generator to the absorber passes through a heat exchanger in order to preheat the weak solution entering the generator. In the absorber, the strong solution absorbs the water vapor leaving the evaporator. Cooling water from the cooling tower removes the heat by mixing and condensation. Since the temperature of the absorber has a higher influence on the efficiency of the system than the condensing temperature, the heat-rejection (cooling water) fluid, is allowed to flow through the absorber first and then to the condenser [5]. An auxiliary energy source is provided, so that the hot water is supplied to the generator when solar energy is not sufficient to heat the water to the required temperature level needed by the generator.

Graph1.1single effect absorption air

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