Solar Chimneys or Thermal Chimneys - Components & Features

Solar chimneys are tall passive solar heating and cooling system in the form of a chimney that can be used to regulate the temperature of a building and provide ventilation. Solar chimneys are hollow containers that are connected from the inside part of the building to the outside part as shown in the figure below. 

These chimneys are externally coated by material to absorb the solar radiation and use this energy to heat the air trapped within the chimney and regulate the air, based on the climatic conditions.

Working of Solar Chimneys

Solar chimneys are passive solar ventilation systems installed on roofs or on walls. 

Also Read: Cool Roofs for Buildings | US EPA 

Solar chimneys are primarily solar heaters that can take a vertical or horizontal configuration. The unit absorbs solar energy and heats up the air trapped inside the unit. The heat is transferred through the convective cooling principle, where the hot air rises upwards. This means the chimneys reduce unwanted heat during the day by displacing interior warm air with exterior cool air. 

The air movement in chimneys is performed under buoyancy forces, where the hot air rises and exits at the top of the chimney, and draws cooler air into the building with a continuous cycle. 

Solar Chimneys for Cooling the Space: Here, as mentioned in the working, vents are provided in the solar panels, to take warm air out through the vents provided in the solar chimneys, taking cool air into the space. One vent is placed at the top of the chimney to take the hot air out and the second vent is placed at the opposite end of the building.

The solar chimneys are constructed black as a hollow thermal mass with an opening at the top, to act as an exit for the hot air. The hot air in the room exists from the top of the chimney. The second vent is placed at the opposite end of the building to pull new air from outside, which creates a sort of draft that would provide cool, fresh air into the building.

Solar Chimney Working for Cooling in Summer
Image Credits: ae390-systemsvariety-group6

Solar Chimney for Heating the Building: In this solar heating system, the air is heated using the convective air heating principle by solar energy. There there are no vents for the chimney. The air within the space is heated and forced back into the space, to keep the building warm from outside freezing temperature. 

Solar Chimney Working for Heating in Winter
Image Credits: ae390-systemsvariety-group6

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