Heating and Cooling Systems in Building – Air Vs. water

Abstract

This project compares the performance of two different heating and cooling systems. These two systems are a water based system, which is mainly based on Thermally Activated Building Systems (TABS), and an air based system, which is based on a simple heating, ventilation and air conditioning (HVAC) system. A climate classification for the use of TABS has been created in the current project. The intention of this classification is to determine in which climate zones a building requires to implement a heating, a cooling or a dehumidification system. A climate classification system that considers dehumidification is important when TABS are implemented, since risk of condensation can be a problem when these systems are used for cooling requirements. The new European Climate Classification (ECC) system is based on a combination of the annual number of heating and cooling degree days and the outdoor dew-point temperature. Four different thermal categories, which are defined by the number of heating and cooling degree days, and three dew-point categories, which are defined by the dew-point temperature, are introduced in the ECC system. In total, the current classification is based on twelve possible final climate categories and has been evaluated in 92 European cities. Some parameters have been introduced in thermal and dew-point categories. These parameters are investigated in a parametric analysis conducted in this project. This analysis investigates how changing some parameters in the ECC system affects the location of the different climate zones in the map of Europe. As shown in this analysis these parameters have a significant effect on the climate classification of the locations in Europe. Only two of the five initial base temperature cases were evaluated in the entire parametric analysis as more suitable classifications for Europe according to existing climate classifications were obtained with these two cases. These base temperature cases are HDD18°C/CDD18°C and HDD16°C/CDD19°C. Thermal comfort and energy consumption are compared between water and air based systems using the building simulation program IDA ICE. The performance of both systems is tested in ten European cities classified in seven different climate zones found with the ECC system. The comparative analysis is carried out in four different offices of the Balanced Office Building (BOB) in Achen, Germany. The BOB is an energy-efficient and well-insulated office building in which TABS are implemented for cooling and heating requirements. The shading devices implemented at the beginning are modified for offices A, C and/or E, according to each city case, in order to improve thermal comfort. For all ten locations the initial shading coefficients have been reduced for office C, since during the first simulations it was found that indoor temperatures were too high in this office.