BioSkin defies urban heat island effect to help keep buildings cool
The BioSkin that coats the NBF Osaki Building in Tokyo integrates evaporative cooling to keep its surface temperature down
The urban heat island effect, whereby the high concentration of heat-retaining concrete and bitumen causes metropolitan centers to be significantly warmer than the rural areas surrounding them, is a common problem around the world. The phenomenon is particularly prevalent in Tokyo, Japan, but among the sea of towering structures stands one beacon of hope. The BioSkin that coats the NBF Osaki Building integrates evaporative cooling to keep its surface temperature down and could inspire new solutions to rising city temperatures across the globe.
The 25-story NBF Osaki Building was completed in March, 2011 and is the first structure to use the BioSkin system. The urban facade is inspired by traditional Japanese air-cooling systems, such as the water-spraying Uchimizu and bamboo blinds known as Sudare. Using these methods as a foundation, researchers at the Nikken Sekkei architecture firm conceived BioSkin with the seemingly counter intuitive aim of improving the local environment through building large-scale architecture.
Rainwater is collected on the roof of the building and drained to a subsurface storage tank to be filtered and sterilized. It is then pumped through a network of special porous ceramic pipes which act as a sprinkler system. As the water evaporates, it reduces the surface temperature of the pipes and the air that surrounds them, with excess water fed to the soil below. Solar panels are also fixed to the south side of the building, acting as shades and helping to reduce overall energy costs.
Nikken Sekkei says that according to its simulations, the BioSkin can lower the surface temperature of the building by as much as a total of 12°C (22°F) and the surrounding air by 2°C (3.6°F). This ability to affect the micro-climate is what gained the BioSkin recognition from the the Council on Tall Buildings and Urban Habitat (CTBUH) which bestowed its Innovation Award on the building earlier this month.
"The potential implications of this are substantial," the CTBUH says. "If a large number of buildings in a city used such a system, ambient air temperature could be reduced to the point that cooling loads for many buildings, even those without the system installed, could be reduced."
Source: Nikken Sekkei
About the Author
Nick was born outside of Melbourne, Australia, with a general curiosity that has drawn him to some distant (and very cold) places. Somewhere between enduring a winter in the Canadian Rockies and trekking through Chilean Patagonia, he graduated from university and pursued a career in journalism. Having worked for publications such as The Santiago Times and The Conversation, he now writes for Gizmag from Melbourne, excited by tech and all forms of innovation, the city's bizarre weather and curried egg sandwiches.
All articles by Nick Lavars
Exactly. I was thinking the same things sk8dad!
This is pretty cool use of evaporative cooling. The same idea is used in cooling towers where it is used to dump waste heat into the atmosphere. I had the idea to create a so called 'bong' cooler for water cooling my PC. It's basically a tall PVC pipe with a sprinkler on top and a base that holds water. It removes heat from the system by water evaporation as small water droplets fall through the pipe. I didn't make it due to the hassle with maintenance (continuously add water, organic goo accumulating in the open-loop even with silver coils), but it cools extremely well. Way better than your off the shelve water-cooling.
I did make my custom watercooling loop, which uses an used car radiator. Passively cools itself and less hassle, but still offers exceptional cooling.
Fretting Freddy the Ferret pressing the Fret
I have doubts similar to sk8dad about the benefits of this idea.
Even for those areas exactly in the Goldlocks zone where rainfall is sufficient yet humidity still leaves some room for evaporative cooling, the end result is going to be near saturation outside. In effect this is merely trading a desert heat island effect for a swamp heat island effect.
Maybe someday we will figure out how to "kill two birds with one stone" with the cooling evaporators able to use grey water or seawater without fouling the system. (No need to use cleaned freshwater, the process would provide the cleaning and desalination.)
In an environment where one can collect enough rainwater to have it sprayed down the side of the building, one would probably expect high humidity along with high temperatures. Wouldn't the efficiency of evaporative cooling be diminished? I suppose a little is better than none. On the flip side, places that have low humidity with high temperatures like the American southwest usually don't have enough rainfall to just throw away.
The physics doesn't seem to add up.
The solar panels will by absorbing sunlight and converting it into electricity reduce the solar heating of the building.
Water cooled in a subsurface storage tank could cool the side of a building this is but not what they are claiming.
“As the water evaporates, it reduces the surface temperature of the pipes and the air that surrounds them” …… can lower the surface temperature of the building by as much as a total of 12°C (22°F) and the surrounding air by 2°C (3.6°F). ……… ambient air temperature could be reduced to the point that cooling loads for many buildings, even those without the system installed, could be reduced."
Where does the heat go ?
Evaporative cooling works with the higher energy (hotter) atoms leaving the system and the cooler atoms remaining behind. It also takes energy (enthalpy or ∆Hvap) to escape the liquid surface.
This will cool the specific building but how does it also cool the surrounding air, the microclimate, and surrounding buildings ?
Over 160,000 people receive our email newsletter
See the stories that matter in your inbox every morning