Mongolia bids to keep city cool with 'ice shield' experiment

[M II A II R II K]

Mongolia bids to keep city cool with 'ice shield' experiment


15 November 2011

By Jonathan Watts



Read More: http://www.guardian.co.uk/environmen...geoengineering

Mongolia is to launch one of the world's biggest ice-making experiments later this month in an attempt to combat the adverse affects of global warming and the urban heat island effect. The geoengineering trial, that is being funded by the Ulan Bator government, aims to "store" freezing winter temperatures in a giant block of ice that will help to cool and water the city as it slowly melts during the summer. The scientists behind the 1bn tugrik (£460,000) project hope the process will reduce energy demand from air conditioners and regulate drinking water and irrigation supplies. If successful, the model could be applied to other cities in the far north.

The project aims to artificially create "naleds" - ultra-thick slabs of ice that occur naturally in far northern climes when rivers or springs push through cracks in the surface to seep outwards during the day and then add an extra layer of ice during the night. Unlike regular ice formation on lakes - which only gets to a metre in thickness before it insulates the water below - naleds continue expanding for as long as there is enough water pressure to penetrate the surface. Many are more than seven metres thick, which means they melt much later than regular ice. A Mongolian engineering firm ECOS & EMI will try to recreate this process by drilling bore holes into the ice that has started to form on the Tuul river. The water will be discharged across the surface, where it will freeze. This process - effectively adding layers of ice rinks - will be repeated at regular intervals throughout the winter.

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[ardecila]

There are Mongolian engineering firms?

[dchan]

Isn't the specific heat capacity of ice roughly half that of liquid water? If the firm is able to successfully creating 'naleds', I'd be curious to see if the concept actually pans out according to their theory, or whether it makes the heat worse because of the difference in respective heat capacities between liquid water and ice.

[mrnyc]

how interesting and rather elegantly simple. worth a try for sure. if it doesnt work out i guess they can just stop keeping up with the drilling/freezing work.

[scalziand]

Originally Posted by dchan

Isn't the specific heat capacity of ice roughly half that of liquid water? If the firm is able to successfully creating 'naleds', I'd be curious to see if the concept actually pans out according to their theory, or whether it makes the heat worse because of the difference in respective heat capacities between liquid water and ice.

Yes and no. Liquid water has a higher specific heat capacity, but there's only so much heat that can be removed from water before it turns into.... ice. To continue be cooled, ice has to be formed. Plus the longer the ice survives into the summer, the more sunlight it will reflect, preventing it being absorbed by the water.

You're effectively implying that on a hot day, a glass full of cold water will stay colder longer than a glass full of water and some ice.

The ice has to absorb more energy than the water before it comes to thermal equilibrium with its surroundings.

[LeeWilson]

^Yeah, I'm having trouble understanding how one could imagine that a gigantic block of ice could actually heat up a city.

[dchan]

Originally Posted by LeeWilson

^Yeah, I'm having trouble understanding how one could imagine that a gigantic block of ice could actually heat up a city.

No, it won't heat up the city. What I'm trying to say is that the river or lake usually acts as heat sink during the summer. Because liquid water has a higher heat capacity than ice, using just ice as the heat sink might not work as intended because it may not contain as much heat as liquid water can. I'm not talking about the ice or water itself, but the surrounding environment that it needs to keep cool by absorbing heat (the city).

I can see scalziand's point here, but I remain skeptical nevertheless. And as other say, if it doesn't work, it'll just melt back into water.