Natural ventilation provided by a self-sufficient facade system

Abstract

In order to meet the requirements of the European Directive on the energy performance of buildings, energy producing elements have to be integrated into the majority of the building envelopes. For integrating photovoltaic or solar thermal modules into the facade system, two different building fields have to be connected, namely the facade system on the one hand and the total building energy system, which controls the HVAC (heating, ventilation, and air conditioning) and integrates an energy storage system, on the other hand. This can result in intersection problems. One solution to overcome intersection problems can be a concept of a standalone facade system that produces energy and at the same time is able to use this energy to control indoor air climate. Thus, no intersection with other building fields is necessary. In the research of the author, a facade system is developed that uses natural ventilation to control indoor air climate. The natural ventilation is controlled automatically to overcome the risk of inadequate user control which could result in higher heating or cooling loads. The auxiliary energy which is required for the opening mechanism is provided by a photovoltaic module and a battery system. Both can be integrated directly into the facade system. This results in a self-sufficient system for natural ventilation. This paper describes the self-sufficient facade system. It contains the construction as well as simulations that are used for dimensioning the energy generating system. One part of the simulations is defining control strategies that enhance the user’s comfort and reduce heating and cooling in order to quantify the opening times and their auxiliary energy needs. Further simulations were performed to quantify the necessary capacity of the battery system. Thus, over- or underestimation of the battery capacity could have tremendous impact on the longevity, production costs, geometry, and weight of such a window. This publication compares a basic method that assumes a 6 Ah battery capacity with a detailed simulation that analyses weather data for each minute of a year. The detailed analysis suggests a battery with 50 % less capacity and can halve the costs of the battery system.