HEAT FLUX IN A PASSIVE MULTI-LAYERED SOLAR PANEL

Abstract

The paper deals with the question concerning the increase in buildings and structures energy efficiency and environmental safety at the construction and installation of engineering systems with financial constraints. We suggest solving this problem with low-cost method of solar radiation utilization which implies the passive thermal energy transformation into external fencing structures. In spite of the economic expedience of such heating systems, there is an opinion that they are suitable only for climatic conditions characterized by a mild heating period due to low efficiency indicators in comparison with the active solar power plant. As regards this, the paper analyzes the well-known and new building translucent, absorbing, accumulating and insulating materials along with the possibilities to create the multifunctional external fences that can expand the geography of the use of passive systems. We have studied the nonstationary thermal processes arising in multilayer external fences of buildings in order to solve the problems of effective solar radiation utilization by facade integrated panels. The analysis of mathematical methods has shown that theory of thermal waves should be used to describe the diurnal temperature changes inside building structures. The principle of temperature frequency superposition principle has made it possible to calculate the heat transfer in multilayer external panes. In Voronezh region climatic conditions (52º), we have evaluated the solar radiation effect on a two-layer and a four-layer structure consisting of a glass unit, an air layer, reinforced concrete and heater, protected from the outside by double-glass unit. In January at temperature -24 °C of the coldest fiveday period, the average daily heat losses through the surface area of 1 m2 of the two-layer outer wall are 6 W / m2 , and under the same weather conditions an average heat flux through the surface area of 1 m2 of the four-layer solar panel is of 36.3 W / m2 ; the maximum values of the heat flux are achieved in 18 hours. The presented data confirm the expedience of passive solar panels use in case of low temperatures during the cold period of a year. Moreover, considering the facade glazing trends and low cost of the passive solar panels in contrast with the active solar systems, we concluded that they should be used for increase in energy efficient of buildings.