Summer comfort in a low-inertia building with a new free-cooling system

Abstract

Wood-framed buildings are considered to have low energy consumption since their construction mode generally gives high U-values and limited thermal bridges. Although the construction mode results in low heating consumption, the lack of storage capacity in the internal walls makes passive cooling designs such as night ventilation inappropriate. Consequently, the interior is subject to considerable temperature swings and higher temperatures than those of buildings with more massive internal surfaces. This paper investigates the possibility of reducing the energy used for cooling buildings by linking a so-called "phase-shifter" air/mass system to the HVAC system. This system is capable to restore the night cooling potential in the daytime by shifting the input temperature oscillation to around half a day, whereas temperature swing is conserved. The numerical model implemented on the SimSpark platform has been validated against the analytical solution for the constant airflow and harmonic temperature profile; then experimental data (obtained from the full-scale prototype designed and installed at the CSTB) has been used to assess its predictive capability with non-constant airflow. Using reduced ventilation periods has been numerically studied regarding environmental air resource and thermal storage efficiently of the system. The size and electricity consumption were optimized by this way. A comfort analysis was carried out on an experimental building with very high energy efficiency (INCA, INES, Le Bourget-du-Lac, France) based on the EN ISO 15251 adaptive model. Energy building simulations demonstrate that associating a phase-shifter to a low-inertia building gives it similar internal conditions to those of a more massive night-ventilated structure. Furthermore the proposed optimization greatly reduces the size of the system (by 30%) and the electricity consumption (by at least 38%) while the temperature is out of the comfort range for an extra 5% of the time.

Modeling and simulation of a phase change material system for improving summer comfort in domestic residence

“…The general idea presented in this paper is to provide the building http with stocks having an inertial potential enable to exploit the freshness of the night when available in order to smooth the internal temperature during summer. Some systems using the inertia of some materials coupled with ventilation have been studied in [1].…”

“…Spatial discretization scheme in the PCM with airflow in x direction 1. For interpretation of color inFig.…”

Critical review of latent heat storage systems for free cooling in buildings

“…The latent heat transfer is approximately an isothermal process as PCMs absorb and discharge heat at almost a constant temperature or within a narrow temperature range which is more applicable for maintaining thermal comfort compared to SHS [46,47]. Another important advantage of LHS is their easy integration where other SHS substances are difficult to be installed particularly in existing buildings and lightweight structures [48]. This is because PCMs are capable of enhancing the mass effect with much lighter weight and volume estimated at 5-14 times compared to conventional SHS systems which require a large space for accumulator accommodation [49,50].…”

Air–soil heat exchangers for heating and cooling of buildings: Design guidelines, potentials and constraints, system integration and global energy balance

“…As a main result, the diffusive heat transfer coefficient and thereby the global air/soil heat transfer coefficient are derived as a function of the available soil layer, which leads the way to the design rules developed in this article. As a second result it is also shown that, for a particularly thin layer submitted to adiabatic boundary condition, it is possible to completely phaseshift the periodic input while barely dampening its amplitude, a phenomenon that lead to the development of a new passive cooling technique [21,22], which will not be treated in this article.…”