A Theoretical Investigation of the Effects of a Trombe Wall for Heating Purposes

Abstract

The building sector accounts for nearly half of all global energy consumption, with space heating representing a major share of this demand. Traditionally, this energy has been supplied through fossil fuel-based systems, contributing significantly to greenhouse gas emissions and temperature change. In response to the growing need for sustainable and energy-efficient heating solutions, this study evaluates the thermal performance of an enhanced Trombe wall system as a passive heating method, integrating renewable solar energy to reduce reliance on conventional fuels. Unlike most prior research that focuses on novel wall construction materials, this work targets retrofit applications, aiming to improve the thermal behaviour of existing brick walls using high thermal conductivity sheet materials. A 2D CFD simulation was conducted to evaluate the influence of sheet material type, thickness, and air gap width on room temperature distribution and wall surface heating. Key parameters studied included sheet material type (copper, aluminium, and stainless steel), sheet thickness (5 mm, 10 mm, and 20 mm), and air gap width (ranging from 10 mm to 100 mm). The radiation model was calibrated using solar data from Abha, Saudi Arabia a high-altitude city (elevation ~2,200 m) known for its cool winter temperatures and strong solar irradiance. Geographic coordinates (18.22°N, 42.50°E) and solar radiation values exceeding 500 W/m² during peak winter hours were used as boundary inputs to simulate realistic climatic conditions. Copper, aluminium, and stainless steel were selected for their distinct thermal properties. Among them, copper exhibited the highest thermal performance across various airflow conditions: - adding a copper sheet enhanced room temperature by approximately 3°C compared to the base case without a sheet. Moreover, increasing the sheet thickness from 5 mm to 20 mm improved the average room temperature from 286 K to 295 K, demonstrating a 9°C increase due to greater thermal mass and inertia. The width of the air gap was also found to be critical, with an optimal value of 80 mm, beyond which natural convection weakened, and thermal performance declined. The proposed system saved around 0.0722 kWh/h per room, translating to 151.62 kWh/year over a 150-day heating season with 14 hours of daily operation. Furthermore, each heating cycle reduced CO₂ emissions approximately 16 grams, offering measurable environmental benefits. The annual cost saving compared to using diesel fuel amounted to 56.94£, with a projected 20-year saving of 1138.8 per room.