Submitted by Maria.Kapsalaki on Wed, 05/07/2014 - 17:36
Fixed shading systems are saving energy by reducing the cooling loads of the space they shade, but can be a source of energy losses due to the increased need of daylight that they create. Aim of this paper is the comparative assessment of different typologies of buildings' shading systems with integrated photovoltaics. The assessment is focused on their energy efficiency and degree of internal visual comfort conditions that they can ensure. The purpose of the comparison is to optimize the combination of shading systems and their integrated solar cells.
For that study , three german buildings with double facades have been monitored for at least one year in order to evaluate their energetic performance. The first building had no air conditioning facilities, the second one had cooling equipment without mechanical ventilation, and the third one had cooling equipment combined with mechanical ventilation.
Several thermal building simulators also allow coupled modeling of bulk air movements using airflow network models.However, solving the combined flow and thermal problem can be problematic, both in the context of traditional building simulators and for modern environments, where both airflow and thermal models are formulated as sets of differential-algebraic equations (DAE). For variable-time-step DAE-basedsimulators, difficult coupled problems often lead to small time steps and slow simulations.
An energy balance over an urban area and over a rural one, reveals that the first case is always more complex than the last one. The urban context is able to change all the energy transferences mainly due to its own layout. Thus, analysing all the energy transferences one by one, we can find how they affect in a different way depending on the surroundings, among other influences.
The air exfiltration part of ventilation is often difficult to determine and its part of the energy balance is therefore usually determined as a remainder or given a constant value. This paper examines ventilation systems in six different modern houses. The constant concentration tracer gas technique tended to underestimate the total ventilation. A simplified theoretical one-zone model made accurate estimations of the air exfiltration. For detailed information on air flows a multi-zone network model was useful.
The study presented has resulted in a simplified procedure for obtaining an overview and a comprehensive picture of the analysis of energy turnover in single family houses, with special consideration given to random and time dependent variations. This procedure is particularly suitable for use in thesolution of sub problems such as the heat storage capacity of various structures and its influence on the energy supply required for the heating system. Harmonic analysis makes it possible to study problems of non-steady heat with arbitrary periods.