Development of a Sustainable, Hybrid Ventilation System

Abstract

As building insulation and airtightness are constantly improving, ventilation plays a dominant role in fresh air supply, thermal comfort and managing heat losses and cooling needs. By designing an integrated ventilation system, it is possible to improve air quality and thermal comfort, at the same time enhancing energy efficiency. This thesis focuses on the development of such a ventilation system. It is done by employing the best features of existing systems and including several new features.
Throughout the thesis, ventilation, night cooling, solar shading, heat balance, heat recovery unit and renewable energy sources are studied. In this study, the demanded yearly ventilation air flow rates are found, the optimal heat exchanger model is selected and optimized, yearly energy consumption is calculated, while at the end, a wind cowl is selected and saved yearly energy using the cowl is calculated. The Excel Macro tool is developed and used to establish the needed yearly air flow rates, applying night cooling and solar shading. The Matlab tool
is used for the selection and optimization of the heat exchanger as well as yearly energy consumption, with and without the wind cowl. The main specifications of the new system are found. Since a resize of the heat exchanger passage is recommended, an experiment is carried out in order to verify the heat transfer coefficient of the air traveling in the heat exchanger.
The developed ventilation system provides the dwelling with a ‘good’ indoor air quality at any time of the year, using minimum required air flow rates per room. Thus, combined with the heat recovery device the heating demand for ventilation air is minimized. The system also provides thermal comfort at most times of the year using natural cooling and optimal shading. Thus, the cooling need of the dwelling is minimized. However, due to the heat recovery unit and high night cooling flows, the newly developed ventilation system has an enhanced electricity use. Therefore it is recommended to also redesign the air distribution ductwork system within the dwelling for low pressure use The wind cowl contributes to electricity savings even more if the ventilation system has a well-designed, low pressure air distribution system.