Impact of the substrate thermal inertia on the thermal behaviour of an extensive vegetative roof in a semiarid climate

The aim of this paper is to evaluate the impact of thermal inertia of the substrate of a vegetative roof on its thermal behaviour. Thermal inertia of the substrate was incorporated in two existing thermal models of vegetative (green) roof systems, the Sailor (2008) and Tabares and Srebric (2012) models. The predicted temperatures across the substrate, with and without inertia, were compared with experimental data obtained on a real vegetated roof located in a semiarid climate. The study shows the absolute need to consider the thermal inertia of the substrate to accurately predict the temperatures within the substrate and thus the heat flux through the roof. When taking into consideration the thermal mass, substrate temperatures predicted by both models agree well with experimental data, with a Root-Mean-Square Deviation of about 1°C at a depth of 10 cm. For the analysed period and investigated vegetative roof, the Tabares and Srebric model outperforms the Sailor model

Seasonal Thermal-Energy Storage: A Critical Review on BTES Systems, Modeling, and System Design for Higher System Efficiency

Buildings consume approximately ¾ of the total electricity generated in the United States, contributing significantly to fossil fuel emissions. Sustainable and renewable energy production can reduce fossil fuel use, but necessitates storage for energy reliability in order to compensate for the intermittency of renewable energy generation. Energy storage is critical for success in developing a sustainable energy grid because it facilitates higher renewable energy penetration by mitigating the gap between energy generation and demand. This review analyzes recent case studies—numerical and field experiments—seen by borehole thermal energy storage (BTES) in space heating and domestic hot water capacities, coupled with solar thermal energy. System design, model development, and working principle(s) are the primary focus of this analysis. A synopsis of the current efforts to effectively model BTES is presented as well. The literature review reveals that: (1) energy storage is most effective when diurnal and seasonal storage are used in conjunction; (2) no established link exists between BTES computational fluid dynamics (CFD) models integrated with whole building energy analysis tools, rather than parameter-fit component models; (3) BTES has less geographical limitations than Aquifer Thermal Energy Storage (ATES) and lower installation cost scale than hot water tanks and (4) BTES is more often used for heating than for cooling applications

An investigation of sensible heat fluxes at a green roof in a laboratory setup

During the last few years, several models have been proposed for the calculation of green roof thermal behavior, but the validation studies of such models are lacking a comprehensive set of highly accurate data. In this study, an experimental laboratory setup was used to create different environmental conditions and to measure sensible heat fluxes to/from a vegetated roof assembly. This experimental setup has been successfully used for different wind velocities (0-3 m/s) to create free and forced convection conditions around green roof tested samples. Furthermore, our study proposed a "basic model" for calculations of the convective heat transfer at green roof assemblies, which is a modified version of the Newton's cooling law, calibrated and then validated with different sets of data. For forced convection flow regimes, the proposed "basic model" resulted in RMSE (Root Mean Square Error) of 11 W/m(2) and R-2 value of 0.81. Similarly, the model provided RMSE of 6.6 W/m(2) and R-2 of 0.90 for sensible heat fluxes with free convection conditions. In the future, this model will be used in on-site experimental studies to understand its performance under wind conditions that exhibit a much wider range than the studied velocity range near the leaf canopy. (C) 2011 Elsevier Ltd. All rights reserved