Solar Heating and Cooling System for Thermal Comfort Conditions and Lower Building Energy Use
Abstract
EPBD Recast Directive 2010/31/EU promotes the improvement of the energy performance of buildings within the Union, taking into account outdoor climatic and local conditions, as well as indoor climate requirements and cost-effectiveness. Furthermore, it encourages architects and planners to properly consider the optimal combination of improvements in energy efficiency, the use of energy from renewable sources and the attainment of thermal comfort for the users (Directive 2010/31/EU). In this respect, the possibility to design a highly efficient heating and cooling (hereinafter H/C) system that attains thermal comfort conditions beside rational building energy use has to be well considered. Highly satisfied user and the attained minimal possible energy use for H/C purposes assure the favourization of low-temperature-heating and hightemperature-cooling systems as compared to conventional systems for H/C of buildings. Good possibilities present H/C radiative panels that allow the use of low valued energy, which is delivered by renewable energy sources. A new direction in the development of a simple solar H/C system that uses solar exergy for warming up the water to be circulated within the panels was suggested by Hoshino and Shukuya (2008). It can be well upgraded also with solar cooling techology system. H/C radiative panels provide H/C energy at a temperature close to room temperature. They have been implemented into quite a few buildings, owning to their positive impact on thermal comfort conditions (Dijk et al., 1998; Krainer and Meletitiki-Alexandros, 2004; Olesen, 1997, 1998; Sammaljarvi, 1998; Shukuya, 2003, 2006, 2010), better indoor air quality (Lengweiler et al., 1997; Sammaljarvi, 1998; Schata et al., 1990) and lower building energy use (Krainer and Meletitiki -Alexandros, 2004; Krainer et al., 2007). Experiences of architects and engineers working on the design of comfort conditions in winter show that higher mean radiant temperature (hereinafter Tmr) and lower room air temperature (hereinafter Tai) can result in more acceptable comfort conditions. This coincides with the fact that thermally comfortable conditions equal to thermal neutrality seem to lead to lower human body exergy consumption rate. The relation was first investigated by Isawa et al. (2003) and Shukuya et al. (2003, 2006). Simone et al. (2011) studied the relation between the human body exergy consumption rate and the human thermal sensation. Results (Simone et al., 2011) showed that the minimum human body exergy consumption rate was related to the thermal sensation votes close to thermal neutrality, tending to slightly cooler side of thermal sensation. The whole human body exergy balance under typical summer conditions in hot and humid regions was analyzed by Iwamatsu and Asada (2009) and Shukuya et al. (2010). Tokunaga and Shukuya (2011) investigated the human-body exergy balance calculation under un-steady state conditions.