Friday, April 24, 2009

Drought and Solar Generated Electricity in the Southwest

Green energy writer are strangely oblivious to environmental issues involving so called Green energy sources. One example is the effect of a Southwestern drought on the power industry. Imagine a coal fired steam plant. in order to operate the plant needs water, quite a lot of water in fact. Water and heat are the main ingredients in steam. Once the steam is run through the generator turbines, it is cooled in a condenser in a process that draws water from the environment and runs it through a heat exchange. Heat from the exhausted steam passes through the heat exchange, in which water is drawn from the environment and heat is exchanged between the purified boiler water and the ordinary environmental water from lakes, rivers and the sea.

In order for Rankine thermal generating plants to operate it has to have access to coolant waters. In fact there has to be quite a lot of coolant waters, in generating facilities that use the Rankine cycles for power. Thus coal fired steam plants typically are built by rivers, lakes or seas, in order to obtain access to coolant waters. The same is also true for nuclear powered steam plants. Occasionally the heat of summer will warm the coolant waters in lakes and rivers, until they are too hot to effectively cool the steam from Rankine cycle power plants. At that point the plant must shut down. Even more rarely extreme drought will cut the amount of water available until it can no longer sustain plant cooling. Again the plant must be shut down.
Climate scientists anticipate growing water shortages in the Southwest during the next decades. They note a long standing climate cycle that brings extreme drought to the American Southwest every few hundred years. Such droughts can typically last for a hundred years or longer. In addition to anticipated reductions in river water flow due to the drought, global warming is expected to decrease the amount of water entering the colorado river from the snow pack.

Now imagine, given these facts, how renewable energy advocates would respond to a plan to build 50 nuclear powered electrical generating plants in the Desert Southwest with cooling water to come from the drought stricken Colorado River and its tributaries. Suppose the plants were coal fired would environmentalist still object? You bet they would. If you asked them, would you object to any thermal plant, the answer would still be yes. Then ask them would they object to a solar thermal plant? The answer would be, "no way." Even if a solar thermal plant used as much water per kWh of electricity produced? The environmentalist are likely to tell you that it would be impossible for solar thermal plants to use as much water as nuclear power plants. Or they will tell you that ST plant's don't really use that much water, or that they can be cooled by air.

Of course, renewables advocates are in total denial about the use of water with solar thermal power. Did you ever read a discussion of solar thermal power in which the word water was used even once? The truth is that Solar thermal plants use as much water as nuclear plants do, and that it is improbably that a drought stricken Southwest could sustain as many solar thermal plants as say the Google or the Greenpeace energy plans call for.

In contrast, nuclear power plants do not have to be cooled by the waters of desert rivers. They can be built by the sea shore. The sea side location can facilitate the use of reactor waste heat for desalinization. Considering the potential water shortage in the Southwest, this production of water as a byproduct of the nuclear generation of electricity would no doubt be considered highly desirable.

3 comments:

David Walters said...

Charles, their answer is that they won't use water cooled condensers but air cooled ones like CCGTs do now or current solar thermal ones do. They don't care about taking an efficiency hit.

David

Bobcat said...

Charles,

There is a story in the NY Times about how the National Park Service is concerned about the effects of renewable energy projects will have on water use and wildlife that are planned to be built on public lands. Here is the link to that story.

http://www.nytimes.com/gwire/2009/04/23/23greenwire-park-service-warns-of-solar-projects-impacts-t-10660.html?pagewanted=1

It appears that many forms of renewable energy are not as benign on the environment as advertised. Though nuclear power plants do have an environmental impact at least they can be constructed in a wider variety of locations to minimize disruption.

But for most forms of renewable energy systems require a certain environmental conditions to work, like areas of geothermal heat, massive amounts of water, constant wind or plentiful sunshine, which limits their site selections. I predict that once more renewable energy projects leave to design stage and construction actually begins we will see more conflicts with environmentalists.

Warren Heath said...

Nuclear can use air cooling, as well. It is simply a cost issue. Since Solar Thermal is running upwards of $15,000 per delivered kw and over 15 cents a kwh, the added cost of air cooling is less significant than for nuclear. The numbers I've read indicate about 1/2 cent a kwh additional cost for air cooling. With current nuclear plants energy cost about 1.7 cents a kwh - that's a significant add-on. Especially since it is completely unnecessary and downright stupid, when you can locate Nuclear power plants near large water bodies. Saying a nuclear power plant is using huge amounts of water is like saying ships are using enormous amounts of water. Water going into the prop and being ejected at higher speed. If you want to look seriously at water use - look at biofuels. Precious FRESH irrigation water used - as much as 2200 gals for every gal of ethanol produced

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