Energy consumption in buildings is approximately one third of the total energy consumption. In modern architecture, the area of the glazing is getting bigger and bigger, and this leads to an increasing influence of the windows on energy efficiency of the buildings. A huge amount of electricity is consumed to provide a comfort room temperature through air conditioning. Instead of this advance glazing technologies and materials can be used to reduce buildings energy demands and improve indoor environment.
Based on construction and architectural design trends and due to its unique characteristics the water flow glazing - WFG module is a product of the future. It is a vertical-shaped modular unit which consists of a triple glazing sized 1.3m x 3m (one fluid/water chamber and an argon chamber), a circulator allowing fast flow rates up to 8 l/min per window, and a modular aluminum frame that encloses the glazing and the circulator. Depending on the combination of the glass type and the position of the argon and water chambers the three types of WFG modular units are designed - HeatGlass, CoolGlass and iThermGlass.
The thermal behavior of WFG modules is investigated by using mathematical models covering all physical processes - heat exchange, fluid flow dynamics, optical and structural behavior as well as environmental influences.
To predict the performance and behavior of the WFG, as well as to optimize the modular unit and its components, mathematical and simulation models were developed by Polytechnic University of Madrid in Spain. The software model is successfully integrated under the existing and widespread software product IDA-ICE and describes the change of the thermal conductivity of the glazing due to varying fluid flow rate (g- and U-values) as well as the energy gain in the WFG.
Two main parameters characterized the thermal behavior of WFG. One is water heat gain, which is the solar energy absorbed and transported by the water chamber. The other is internal heat flux - the total heat transfer through the glazing. Figures below presents the average monthly results of the water gain parameter and internal heat flux in Sofia.
The annual Water Heat Gain for iThermGlass shows the biggest fluctuation on the monthly based. CoolGlass is stable during this period. Only for HeatGlass the mean Water Heat Gain is positive, which means that we are harvesting energy through the whole year.
The annual Internal Heat Flux variations are strongly related to the annual changes of the external temperature and solar radiation. For a location like Sofia the best performing WFG unit is HeatGlass.
The results show that the structural configuration and the type of coating play important role for the effective operation of the units. Relying on the simulation software developed under the InDeWaG project we can successfully predict the behavior of the WFG modules and we are able to choose the appropriate configuration of the glazing according to climatic conditions to reduce the energy consumption in buildings.