Heating and Cooling Energy Consumption of Dwelling located in Algeria R.KHARCHI *, B.BENYOUCEF ** * Centre de Développement des Energies Renouvelables, CDER, BP62 Route de l'Observatoire, Bouzaréah, 16340, Algiers, Algeria.
[email protected] ** Faculté des Sciences, Unité de Recherche Matériaux et Énergies Renouvelables, Université de Tlemcen, Algéria. Abstract--Nowadays most countries have adopted normalized procedures to insulate houses in order to minimise energy losses. Renewable energy has the advantage to be clean and free of gas emission. Algeria is considered having the greatest solar potential among Mediterranean countries (5 billion GWh per year, with an average sunshine ranging from 2.250 hours North to 3.600 hours South). Thus, it is of great interest to use this abundant energy for building heating and cooling. The aim of this work is to study the effects of solar heating gain based on energetic thermal consumption of typical house in Algeria. For that, three different sites have been chosen; the first one is located north of the country (Algiers), the second one in high lands (Setif) and the third one in the south (Bechar). Degree day method has been used here to determine both heat losses by transmission and ventilation according to international standards on thermal insulation of building. The study has revealed that the utilization rate of heat gain achieved is 89% for Setif, 79% for Algiers and 75% for Bechar. Heating energy consumption has been reduced by 651,78 kWh (from 2414,28 kWh to 1762,5 kWh during December2008). Keywords--degree day’s method, heat transfer, heating and cooling of building, solar energy, and thermal insulation.
INTRODUCTION
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Fig.3. Thermal losses by transmission and Ventilation (Cooling) 3500 Béchar
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Building energy consumption is difficult to estimate du to the importance of internal and solar contributions, the complexity of heating system regulation and intermittency. In this work, three different sites have been selected in Algeria for the study of the energy consumption evaluation for heating and cooling of standard houses having volume of 313 m³. These habitations are built with local materials according to required insulation standards. The concerned sites are chosen according to the three different climate existing in the country, Algiers North on coast (36°46' 59” North 3°2' 59” East), Sétif in high lands (36°11' 20” North 5°24' 50'' East) and Bechar in Sahara (31°36' 28” North 2°13' 12” West). By using NBN B62301 worksheet, based on the calculation of thermal resistances, the level of total thermal insulation was determined; it was found that the house satisfies the first requirement imposed by thermal regulation. The method of the degree day is better adapted for the monthly and annual energy analysis of building, by considering the effectiveness and the conditions of use of building which vary according to outside temperature. The thermal losses differ from one site to another, thus the energy needs vary according to the site weather parameters (room temperature, solar illumination). The solar contributions by glazed surfaces and opaque walls do have an effect on house energy consumption; this influence constitutes the subject of this study..
METHODOLOGY
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According to the composition of the house envelope (double glazing and good insulation of opaque walls), the level of total thermal insulation agrees with European standards on habitat insulation, K43 was obtained (when the compactness of the building V/A≤1, K=100.ks). The method used for calculations is the degree day’s method which appears to be most suitable. Bechar
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Fig.4. Net requirements for cooling
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Fig.1. Thermal losses by transmission and Ventilation (Heating)
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Fig.5. Total free contributions (solar and internal)
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Fig.2. Net requirements for heating
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Fig.6. Monthly utilization heat gain ratio
CONCLUSION The heat contributions by glazed and opaque walls have an effect on energy consumption in building for heating or cooling, this is why it would be necessary to optimize glazed surfaces and well insulate the roof, so that the energy demand is minimized. The demand for cooling is very important especially in the south and exceeds 3000 kWh/month, for that it is necessary to think of solar protections to decrease the solar contributions by the glazed walls. On the other hand for Algiers and Sétif, the energy demand reaches 1500 kWh/month, the maximum acceptable. Most interesting is that the demand for cooling varies with the radiation, so the fact of using this energy source for air conditioning, and cooling systems of building would be much recommended.