Insulated concrete form foundation wall as solar thermal energy storage for Cold-Climate building heating system

Abstract

Employing green energies for building energy sector decarbonization has captured the world’s attention in the current century. However, the imbalance between energy demand and availability necessitates designing reliable and cost-effective energy storage systems. The present study aims to propose an innovative building-integrated solar thermal storage method using insulated concrete form (ICF) foundation walls for residential buildings in cold climates such as that of Canada. Surplus solar thermal energy is stored inside the ICF wall, which has a high thermal capacity and mass and is integrated into the building envelope. The ICF wall and solar thermal collectors are coupled with a water-to-water heat pump to meet building space heating load and domestic hot water demand. Different configurations integrating the ICF wall are modeled and simulated in TRNSYS software to perform a yearly transient analysis. It is shown that a system with ICF walls has an 11% higher solar fraction (SF) than a similar system with a large water thermal storage tank. By replacing the solar thermal collector with a hybrid photovoltaic/thermal collector, the overall system solar fraction can increase to 20% above that of a similar system with a large water thermal storage tank system. An ICF-based system with a 16 m2 solar collector can completely cover nine months of space heating and domestic hot water load for a single-family house in London, Ontario. A detailed sensitivity analysis shows that the proposed ICF-based systems achieve an optimum solar fraction at high tilt angles (65-70°), unlike a similar design with an extensive water thermal storage tank system. Because of their ability to achieve a high SF at high tilt angles, ICF systems are suitable for vertically mounted solar systems typically required by high-rise buildings due to limited roof area. As part of the building envelope, ICF foundation walls have no additional cost and can be considered a feasible strategy for reducing the residential sector’s carbon footprint..