In “Solar Chimneys & Solar Updraft Towers,” we described these solar solutions as ancient passive solar technology, whereby natural heat convection processes are harnessed to provide ventilation. The basic idea is to harness the power of natural ventilation to increase the turnover rate for air within a building by amplifying natural convection processes through the use of a (typically external) vertical shaft that heats up rapidly when exposed to the sun.
RMIT University researchers have energetically enhanced the safety aspect and designed a solar chimney optimized for a 6-fold increase in fire safety — as well an increasing energy saving.
As a passive solar heating and cooling technology, this type of ventilation and/or cooling system has seen widespread use in the region encompassing and surrounding Greater Iran, throughout the Middle East and North Africa, and in Roman Europe throughout the millennia. It’s time to spread its use with the advancements of RMIT University and the Australian town of Kingston, Victoria. This could be a turning point towards expansion.
2 minutes to over 14 minutes
EurekAlert! sums up the potential of stifling energy costs by up to 50%. Saving lives is even more vital, and now the chimneys can provide both. In a world-first, researchers find the specially-designed solar chimney extends the safe evacuation time from about 2 minutes to over 14 minutes. The increase is a much better time for a safe response time in a crisis. The firefighters in Victoria must be smiling. In fact, we all should be.
“Researcher Dr Long Shi said solar chimneys have well established environmental credentials, but their potential for improving fire safety had not been explored.”
“‘In an emergency situation where every second counts, giving people more time to escape safely is critical,’ Shi said.
“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.”
According to the US Department of Energy, an estimated 19% of the world’s energy resources go to heating, ventilating, and cooling buildings.
More from the press release:
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 maximize the absorption of solar radiation. Vents at the top and bottom control the airflow in and out of the chimney for heating or cooling.
As the sun warms the chimney, this heats the air inside it.
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.
RMIT Univesity’s modelling of carbon monoxide levels approximately 16 minutes after a fire breaks out demonstrates the dramatic difference in CO with a solar chimney (top) and without (bottom). Image: RMIT University
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.
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 said.
“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,” he said.
The new research offers a technical guide for optimizing the design and engineering of solar chimneys in real buildings, to expand their application across the two functions.
Related Story: Solar Chimneys & Solar Updraft Towers 101
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