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Dr. Vladimir Gagarin

Research Institute of Building Physics, Moscow, Russian Federation

 

Talk Title
ACCOUNTING OF HEAT INPUT THROUGH LOW-E GLAZING WITH ASSESSING THE ENERGY-SAVING EFFECT FOR THE HEATING PERIOD

Talk Abstract
 

In order to reduce transmission heat loss in the building, glazing is installed, which has energy-saving properties. Such glazing is double-glazed units with glasses with low-emissivity (low-e) and multifunctional coatings. Energy-saving effect is usually determined by the value of the heat transfer coefficient, determined by the glazing center, U0, which for low-e glazing is lower than for glazing without coatings. When using such glazing, the transmission heat loss is decreased, but the heat input from solar radiation is also decreased during the heating period. Then the choice of glazing should be based on the compilation of the optimum ratio of transmission losses and heat input from solar radiation. This article discusses an approach based on comparing the heat loss and heat input through the glazing 1 m2 area having energy saving coating and not having any.In the calculation of heat input and heat loss, the glazing characteristics take part: the solar factor g, relative units, the heat transfer coefficient for the center of the glazing U0, W/m2•°C, the glazing area A, m2, and the climate characteristics: solar radiation entering the vertical surface of the building facade Iver, MJ/year•m2, degree-day of the heating period Dd, oС•day/year.For comparative calculation, the value of heat input and transmission heat loss through the glazing is determined first when installing glass units with uncoated glasses, and , and then when installing glass units with coated glasses and , accordingly. Further, the difference in heat loss and heat input is calculated using glazing without coatings and with coatings:Q_irr^uncoat-Q_irr^(low-e)=A∙I^ver∙(g^uncoat-g^(low-e) ), MJ/yearQ_tr^uncoat-Q_tr^(low-e)=0,0864∙D_d∙A∙(U_0^uncoat-U_0^(low-e) ), MJ/yearThe glazing area is assumed to be A = 1 m2.To assess the feasibility of using low-e glazing instead of glazing without coatings, the difference of heat loss should exceed the difference of heat input, because low-e glazing should provide increased thermal protection, but minimally reduce the arrival of solar radiation. Then the inequality is written:0,0864∙D_d∙(U_0^uncoat-U_0^(low-e) )>I^ver∙(g^uncoat-g^(low-e) )This inequality is transformed to the form when on the left side are the characteristics of the climate, and on the right - the characteristics of the insulating glass unit:I^ver/(0,0864∙D_d )<((U_0^uncoat-U_0^(low-e) ))/((g^uncoat-g^(low-e) ) )The characteristic of the glazing that affects its building energy consumption through its physical parameters is denoted by G (glasing) - as an indicator of the ratio of heat loss and heat input through a double-glazed unit:G=((U_0^uncoat-U_0^(low-e) ))/((g^uncoat-g^(low-e) ) ), W/(m2 oC)Thus, each double-glazed unit has a fixed characteristic G, which can be used to determine the appropriateness of its application in a given climate. The higher this characteristic, the better the glass unit keeps the heat and passes the solar radiation required for heating the room.Climate characteristics C (climate), as the ratio of solar radiation entering the glazing to Dd:C=I^ver/(0,0864∙D_d )Then the efficiency of replacement of a double-glazed unit for the best use of incoming solar radiation with a decrease of heat loss is:C<GThe resulting ratio was used to assess the efficiency of energy-efficient glazing in various cities of Russia. Analysis of the results showed that the use of this inequality makes it possible to determine the optimal ratio of heat-saving and heat-transmitting properties of glazing used in different climates and, thus, to choose the most suitable glazing.

Short Biography

1978 graduated from the Electromechanical department of Institute of water transport, Leningrad. 1994 graduated from the Macroeconomics department of Economic Academy of the Ministry economy of Russia. Since 1975, he worked in the laboratory of electrical analogy of thermal processes of Research Institute for Building Physics.In 1980, he entered the graduate Research Institute of Building Physics and graduated in 1985 as a PhD in specialty HVAС. In 1989, he entered the doctoral to Research Institute for Building Physics and graduated in 1993. HegraduatedasaDoctorofTechnicalScience, on specialtyHVACand building constructionin 2000. He worked as head of the Laboratory of Building Thermal Physics at the Research Institute for Building Physics and Head of the Department HVAСat the Moscow State University of Civil Engineering.In 2010 he became a corresponding member of the Russian Academy of Architecture and Building Sciences.In 2009, he was awarded the Prize of the Russian Government in the field of science and technology.

Field of research: energy savings in buildings, moisture conditions of enclosing structures, heat and moisture properties of building materials, integrated research and development of enclosing structures with high thermal insulation properties, building aerodynamics, building lighting, history of building physics.Published over200 scientific publications.

 
Talk Keywords
energy saving, solar radiation, low-e glass, heat loss, heat gain.
 
Target Audience
Students, Post doctoral, Industry, Doctors and professors
 
Speaker-intro video
TBA
 

 

 

In order to reduce transmission heat loss in the building, glazing is installed, which has energy-saving properties. Such glazing is double-glazed units with glasses with low-emissivity (low-e) and multifunctional coatings. Energy-saving effect is usually determined by the value of the heat transfer coefficient, determined by the glazing center, U0, which for low-e glazing is lower than for glazing without coatings. When using such glazing, the transmission heat loss is decreased, but the heat input from solar radiation is also decreased during the heating period. Then the choice of glazing should be based on the compilation of the optimum ratio of transmission losses and heat input from solar radiation. This article discusses an approach based on comparing the heat loss and heat input through the glazing 1 m2 area having energy saving coating and not having any.
In the calculation of heat input and heat loss, the glazing characteristics take part: the solar factor g, relative units, the heat transfer coefficient for the center of the glazing U0, W/m2·°C, the glazing area A, m2, and the climate characteristics: solar radiation entering the vertical surface of the building facade Iver, MJ/year·m2, degree-day of the heating period Dd, oС·day/year.

For comparative calculation, the value of heat input and transmission heat loss through the glazing is determined first when installing glass units with uncoated glasses,  and , and then when installing glass units with coated glasses and , accordingly. Further, the difference in heat loss and heat input is calculated using glazing without coatings and with coatings:

, MJ/year

, MJ/year

14

 

The glazing area is assumed to be A = 1 m2.

To assess the feasibility of using low-e glazing instead of glazing without coatings, the difference of heat loss should exceed the difference of heat input, because low-e glazing should provide increased thermal protection, but minimally reduce the arrival of solar radiation. Then the inequality is written:

This inequality is transformed to the form when on the left side are the characteristics of the climate, and on the right - the characteristics of the insulating glass unit:

The characteristic of the glazing that affects its building energy consumption through its physical parameters is denoted by G (glazing) - as an indicator of the ratio of heat loss and heat input through a double-glazed unit:

, W/(m2 oC)

Thus, each double-glazed unit has a fixed characteristic G, which can be used to determine the appropriateness of its application in a given climate. The higher this characteristic, the better the glass unit keeps the heat and passes the solar radiation required for heating the room.

Climate characteristics C (climate), as the ratio of solar radiation entering the glazing to Dd:

Then the efficiency of replacement of a double-glazed unit for the best use of incoming solar radiation with a decrease of heat loss is:

The resulting ratio was used to assess the efficiency of energy-efficient glazing in various cities of Russia. Analysis of the results showed that the use of this inequality makes it possible to determine the optimal ratio of heat-saving and heat-transmitting properties of glazing used in different climates and, thus, to choose the most suitable glazing.
The International Conference on Innovative Applied Energy (IAPE’18)