Solar Chimney Introduction

Today, due to the challenges of fossil fuel consumption, such as increasing air pollution, greenhouse gas emissions, and limited resources, the world is using renewable energies such as solar, water waves, hydro-static, wind, and ground energy. One way to utilize solar energy is the solar chimney.

The basis for a solar chimney is the difference in density and pressure difference due to the increase in temperature inside the solar collectors, which acts as a force. Solar energy is one of the cleanest and most accessible sources of electricity, especially in areas with high annual solar radiation.

In a solar chimney system, there is a transparent roof capable of absorbing solar radiation energy. On the other hand, the air entering the system from the sides of this roof collects in the space between the roof and the ground; in fact, the transparent roof and the ground appear as a collector.

The heat received by the ceilings of the solar chimney heats the air in this space and moves upwards due to its lightness (buoyancy effect). In the middle of this roof, there is a vertical chimney or tower, which due to the difference in pressure between the hot airflow and the cold air, causes the hot air to rise into the upper part of the chimney.

Generally, we can divide these solar chimneys into two categories:

1. The first category is the chimneys for power generation, which are of the industrial scale.
2. The second category is the ventilation chimneys for cooling and heating used on a residential scale.

Description

In this project, we have simulated a solar chimney using ANSYS Fluent software. The lower part of the chimney is a plate to absorb the heat of the solar radiation, which we assume as a constant temperature in the present simulation. The ground floor below this chimney also has a constant temperature.

The chimney wall is adiabatic to prevent heat loss. The inlet section below the absorber surface has a pressure equal to the atmospheric pressure, while the pressure in the outlet of the chimney is lower than the atmospheric pressure. This causes the air to suck upward to the top of the chimney due to the buoyancy force, thereby discharging warm air through the chimney.

We model the three-dimensional solar chimney modeling using Design Modeler software. We carry out the meshing by ANSYS Meshing software. The mesh is of a structured type, and the element number equals 106323.

Methodology

We have activated the energy equation to consider heat transfer in this simulation.

Solar Chimney Result

As the solar absorber panels increase the air temperature, it becomes lighter, and its density decreases; this causes a pressure drop and suction for upward flow.