Solar Wind Energy Tower Inc. (fka SWET)

[Nomad505]

The only long term concern that comes to my mind occasionally is the water usage. I'll start with the facts as I know them.

The SWET tower won't use any more water than the previous agricultural use of the land the tower sits on used.

The water will come from the city out of their allocated water rights and will be pulled from nearby wells. The company will pay the city to drill additional wells and purchase the water directly from the city.

The City already has water rights for significantly more water than it currently uses. The additional water sold to the tower won't be more than a fraction of that surplus.

Please keep in mind that this is only a legal right to the water. It's not a guarantee of the water being able to be extracted from the aquifer.

Water will be recycled within the tower which will reduce the burden on the city.

I've seen various members post their concerns about the water here on ihub. Up until now I've dismissed them, but I've always been a little uneasy about it.

One thing that stuck in my mind from the conference call was the part where Pickett mentioned that water that isn't collected and recycled will be returned to the environment where it will be absorbed into the ground and replenish the aquifer. (paraphrased)

I just cannot see it as possible.

Water is sprayed into the top of the tower. A significant amount of this water is evaporated into the air. This endothermic reaction is the power that drives the whole process.

I guess they spray more water in than can be absorbed into the air by evaporation. The excess is collected and recycled.

The chilled air falls rapidly through the tower and is directed into turbines which circle the base of the tower.

The turbines could be considered as the exhaust. The air is released directly into the atmosphere at the base of the tower. The only difference between the intake & exhaust is the water vapor that has been absorbed into the air.

The tower is a simple & clean technology. I don't see anything wrong with the process. It should work as advertised. I'm sure there's plenty of science behind their energy calculator.

Now back to Pickett's statement of the water that escapes the tower somehow finding its way back into the aquifer.

The cool moist air leaving the tower would likely linger along the ground in the area surrounding the tower. Unless there's a wind to disturb it it could lower the temperature of the surrounding area significantly. The tower is basically a giant swamp cooler.

In order for water vapor to condense back into water it would have to be cooled past it's condensation temperature. As I understand it that temperature is somewhat variable depending on various factors.

I suppose that it's possible that for some portion of the year that the temperature at night may fall below the condensation point, so I'll give Pickett the benefit of the doubt for step one of getting the water back into the aquifer. Some portion of the exhaust may condense locally.

Any water vapor that doesn't condense would be carried away with the air. It's destination impossible to determine.

Step two is simply insurmountable IMHO. Any condensation would only be absorbed into the surface. That surface is probably fairly sandy and is separated from the aquifer below either by sold rock or most likely a layer if impermeable clay or other impermeable soil of similar properties. If an impermeable layer didn't exist the aquifer would have been lost long ago.

As far as I know water in an aquifer is ancient. It's been underground for thousands of years. It takes a very long time for this water to be collected deep underground.

And finally, my concern.

I'm sure that Pickett & his team have done their homework with the tower. It's great work IMO. It's revolutionary and could one day be a dominant technology in the generation of electricity.

But did they put much effort into the water? When asked in the conference call Pickett dismissed the concern rather casually. In his eyes water simply won't be an issue. Then he backs up his dismissal with an assurance that the exhausted water vapor would magically return to the aquifer. I think that I've proven my case that it's just not possible for that to happen. Obviously, there's a gap in the thought process of the water cycle. Hopefully, it's not in indicator of a larger problem.

The first site was abandoned after a dispute over the protection of a lizard. Small details can make or break a project like this.

I'm thinking about the long term. The tower has to be operational for at least 20 years in order to make good on its agreement with National Standard. I would imagine that water is on their minds as well. After all, water is basically the fuel for this power plant.
BTW, this long post came out of my previous thoughts combined with a news story I discovered this morning expressing concerns about the ground water in the Western States. The proposed tower is located at the end of the Colorado River Basin in the US which is exactly the area that the article is discussing.

http://news.sciencemag.org/earth/2014/07/western-u-s-states-using-ground-water-alarming-rate

I don't think that the water concerns will be a deal breaker. If it comes down to it I'm sure that there's plenty of room for compromise. After all, which would you rather have a lettuce farm or electricity?