A solar chimney that saves lives and energy

  Last updated May 12, 2020 at 8:14 am


This solar chimney can slash energy costs and now research reveals it could also help save lives in a building fire.

Why This Matters: Clever concepts like this can reduce the massive weight of energy resources on the environment.

In a world-first, researchers have designed a solar chimney optimised for both energy saving and fire safety.

Modelling shows the specially-designed solar chimney radically increases the amount of time people have to escape the new building during a fire – extending the safe evacuation time from about two minutes to over 14 minutes.

A solar chimney is a passive solar heating and cooling system that harnesses natural ventilation to regulate the temperature of a building.

With an estimated 19% of the world’s energy resources going to heating, ventilating and cooling buildings, integrating solar chimneys into new builds and retrofitting to existing structures offers great potential for reducing this massive environmental cost.

Solar chimney potential to improve fire safety had not been explored

In the new project, a collaboration between RMIT University and the City of Kingston, researchers designed a solar chimney to maximise its efficiency for both ventilating fresh air and sucking smoke out of a building in case of fire.

RMIT’s Dr Long Shi says solar chimneys have well established environmental credentials, but their potential for improving fire safety had not been explored.

Also: Dr Marianne Foley – Fire Safety Engineer

“In an emergency situation where every second counts, giving people more time to escape safely is critical,” says Shi.

“Our research demonstrates that solar chimneys offer powerful benefits for both people’s safety and the environment.

“Delivering on two important functions could boosts the already strong cost-effectiveness of this sustainable technology.

“We hope our findings will inspire more investment and development of solar chimneys in Australia, and around the world.”

solar chimney_carbon monoxide_fire

Modelling of carbon monoxide levels about 16 minutes after a fire breaks out shows the dramatic difference in CO with a solar chimney (top) and without (bottom). Credit: RMIT

While calculations around the 6-fold increase in safe evacuation time were specific to the new building, previous research by the team from RMIT’s School of Engineering has confirmed solar chimneys can successfully achieve both functions – ventilation and smoke exhaustion.

Hot air rises: how a solar chimney works

The passive design approach behind solar chimneys operates on the well-known principle that hot air always rises.

Modern solar chimneys usually feature a wall of glass next to a wall that is painted black, to maximise the absorption of solar radiation. Vents at the top and bottom control the airflow in and out of the chimney for heating or cooling.

Also: Painting buildings white could help avoid extreme heat

As the sun warms the chimney, the air inside it heats up.

The hot air rises and is vented out of the top of the chimney, which draws more air in at the bottom, driving ventilation through a building to naturally cool it down.

When it’s cold outside, the chimney can be closed, to direct the absorbed heat back into the building and keep it warm.

It’s an ingeniously simple concept that is relatively cheap to retrofit and adds almost no extra cost to a new build, but can drive energy consumption down.

solar chimney_room temperature_temperature control

The solar chimney helps control temperature in case of a fire. Modelling shows temperature at 16 minutes with a solar chimney (top) and at 3 minutes without a solar chimney (bottom). Credit: RMIT

Reducing smoke, increasing safety

During a fire, the same principle – hot air rises – enables the solar chimney to suck smoke out of the building.

Less smoke means better visibility, lower temperatures and reduced carbon monoxide – all of which contribute to increasing the amount of time people have to safely evacuate.

Teach This: Education resource – A solar chimney that saves lives and energy

To understand exactly how much evacuation time a solar chimney could deliver for a specific building, you need to model for that exact design, Shi says.

“This will differ from building to building, but we know that any extra time is precious and improves fire safety, which could ultimately help to save lives.”

The new research offers a technical guide for optimising the design and engineering of solar chimneys in real buildings, to expand their application across the two functions.

The research is published in the journal Energy and Buildings.

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