Energias renováveis com ênfase em sustentabilidade
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Estudo de Caso Acesso aberto Refrigeração de ambientes por absorção utilizando energia solar térmica com ênfase na redução da carga do sistema elétrico nacional: uma alternativa à refrigeração por compressão mecânica de vapor(2017) Lisboa, Bruno KoechSun delivers to the Earth atmosphere 1.53x1018 kWh per year, while the world energetic consumption according to DOE/EIA in 2008 was 1.48x1014 kWh. In this way, the solar energy that arrives to our planet is 10,000 times bigger than our demand. A great part of this energy comes as light and heat. Light that can be converted in electricity by photovoltaic panels by the photoelectric effect, meanwhile with low efficiency, high expenses of implantation and sensible to high temperatures. On the other hand, the solar thermal waves that reach the Earth, and are directed to the suggested system object of this research, can convert into useful energy with higher efficiency, lower cost of implantation when compared to photovoltaic panels, and with the great advantage that as higher the temperature of the collectors, bigger the energy conversion. PROCEL (2005) says that 44% of electric energy from Brazilian homes are used to bath water heating and air conditioning, transforming electricity, a noble energy, in thermal energy. Electricity, in general, is produced far from the consumer units and involves large amount of resources to deliver this energy to final consumer. This research aims to the rational use of electricity and also to reduce the needs of transmission and distribution lines. Electricity is straight associated to HDI, as the type of energy matrix adopted in a country is another indicator of development, associating cleaner and renewable matrices to developed countries, or in the way of development. The question that targeted this quest was: “Which contributions this form of energy can offer to the transformation for Brazilian energetic reality and why is that belief?” In the way that the main goal of this paper is to point evidences that the use of thermal solar energy can significantly contribute to two vectors of great environmental impacts, which are the rational use of electrical energy and to reduce the needs of building new transmission and distribution lines. However the use of solar energy to heat water is a well-known and wellaccepted technology, the use of heat to produce cold is not well-spread, besides being a technology that precedes the mechanical steam compression and wellstudied. There is no stimulus, neither from the government or society, to embrace the idea of cooling with the Sun. Perhaps just unfamiliarity with the theme. The main principle of this equipment consists in an absorber fluid and a refrigerant in a homogeneous mix, with no interaction between them, which can be separated by the action of heat, be it from the Sun or any other source of energy, in refrigerant steam and liquid absorber. As soon as the refrigerant is alone, it passes through a heat-exchanger to lose heat and condensate. As soon as the refrigerant get in the liquid state it passes through a pressure reducing valve when occurs an adiabatic expansion, reducing its temperature and allowing the formation of bubbles. Then the fluid passes through another heat exchanger, the evaporator, and the bubbles of refrigerant increase its development until the state of saturation as the refrigerant removes heat from the environment to be refrigerated. The saturated steam is then mixed with the absorber fluid that reduces its specific volume and release heat. A pump pushes the solution to the higher pressure of the system and the cycle restarts. The system can use several mixes of refrigerant/absorber according to the conditions of work and temperatures needed. The most common mixes are “ammonia + water” and “water + lithium bromide”, in both cases the first component is the refrigerant and the second, the absorber. During the development of this technology, the mix of “ammonia + water” was widely used, but it lost space to “water + lithium bromide”, because it’s safer and more environment-friendly. This research identifies a large market for this technology, in the field of air-conditioning or refrigeration, and that special attention should be given to this subject.