Thursday, October 25, 2007

Combat Global Warming with Evaporative Cooling


Combat Global Warming with Evaporative Cooling - by Sam Carana

To combat global warming, wind turbines along the coastline could be used for the dual purposes of generating electricity at times when there is wind and evaporating water at times when there is no wind. Just a small breeze over the water can give the top water molecules enough kinetic energy to overcome their mutual attraction, resulting in evaporation of water and associated cooling of both water and air.

Such dual use of wind turbines can be implemented at many places where turbines overlook water; evaporation will work most effectively in hot and dry areas, such as where deserts or dry areas meet the sea or lakes. Evaporative cooling will add humidity to the air, which can also cause some extra rain and thus increase fertility of such dry areas as a beneficial side effect.

The energy needed to run the turbines can be obtained and stored in a number of clean, safe and renewable ways. ]

At times when there is plenty of wind, surplus energy from the turbines could be used to convert Water into hydrogen by means of electrolysis. Alternatively, bio-waste could be burned by means of pyrolysis to create both hydrogen and agrichar, which could be used to enrich soils. The hydrogen could be kept stored either in either compressed or liquid form, ready to power fuel cells that can drive the turbines at any time, day or night.

Another alternative is to run the turbines on electricity from concentrated solar thermal power plants in the desert. A desert area of 254 km² would theoretically suffice to meet the entire 2004 global demand for electricity. Ausra offers a solar thermal technology that uses the sun's heat to generate steam, which can then be stored for up to 20 hours, thus providing electricity on demand, day and night. Ausra points out that just 92 square miles of solar thermal power facilities could provide enough electricity to satisfy all current US demand.

Finally, there are some environmental concerns about wind turbines. There are concerns about carbon dioxide being released into the atmosphere in the process of making the concrete for the turbines. To overcome this, turbines could be made using alternative manufacturing processes, which can be carbon-negative. Furthermore, a recently completed Danish study using infrared monitoring found that seabirds steer clear of offshore wind turbines and are remarkably adept at avoiding the rotors.

In conclusion, wind turbines have a tremendous potential. They can potentially generate 72 TW, or over fifteen times the world's current energy use and 40 times the world's current electricity use. Offshore and near-shore turbines can make seawater evaporate and thus cool the planet, at times when they are not used to generate electricity.

References:
Ausra
http://ausra.com/

Wind power - Wikipedia
http://en.wikipedia.org/wiki/Wind_power

Evaluation of global wind power
http://www.stanford.edu/group/efmh/winds/global_winds.html

Solar power and electric cars, a winning combination!
http://www.gather.com/viewArticle.jsp?articleId=281474977115548

Agrichar
http://www.gather.com/viewArticle.jsp?articleId=281474977139103

Alternative method of manufacturing concrete
http://www.tececo.com/

Massive Offshore Wind Turbines Safe for Birds
http://www.technologyreview.com/Energy/18167/

Footnote:
This article was written by Sam Carana; it can be freely copied and published elsewhere, as long as the autor's name is retained in the article.

2 comments:

Thomas said...

This seems pointless.
Evaporating water does not get rid of heat energy; it just temporarily transforms it - when the water recondenses, it produces heat again. Water vapor is a greenhouse gas, so it will increase retention of heat.

Water droplets, in the form of clouds, fog, or haze, have a complex, mixed effect on the energy balance, depending on whether reflection of radiated heat exceeds reflection of incident sunlight, but this is definitely not a general-purpose planetary cooling method.

Swamp coolers are efficient at moving heat and increasing humidity, but they won't cool the planet.

Sam Carana said...

Sure, Thomas, but for as long as it lasts, the extra evaporation will have had a cooling effect. And as long as the turbines keep evaporating water, this cooling effect will continue.

Similarly, as wind turbines capture the energy contained in the wind and as this energy remains stored in the form of hydrogen, this will have a slight cooling effect, as opposed to the energy of the wind heating up rocks and trees by means of friction.

One can argue whether it makes more sense to use such hydrogen to power transport than to make turbines run in reverse, but it does sound like an interesting discussion in the context of geo-engineering.

Greater humidity thus produced could cause more rain to fall in arid areas, causing vegetation there to grow better, holding the water longer and capturing carbon from the atmosphere in the process. As the article says, evaporation will work most effectively in hot and dry areas, such as where deserts or dry areas meet the sea or lakes. Solar power from such a desert could run the turbines and, as more vegetation will grow, the temperature will go down there and the area will be able to produce food, etc.