Intermittant Nuclear Power

Wind and Solar critics constantly point to the intermittent nature of renewables as one of the reasons that renewables are not a viable 24 X 7 power source.  While this is not absolutely true it is also not true that fossil fuels and nuclear are always available.  All generating systems have capacity factors.  Wind varies from 20% for turbines placed in unsuitable locations to 40% for offshore wind.

Nuclear power also has a capacity factor and in the US they have achieved remarkable reliability:
Download u.s._capacity_factors_by_fuel_type.ppt

If you have a look at the attached table nuclear is at 89.8% however the effect on the grid when a nuclear plant drops out is quite dramatic.  The problem is that nuclear reactors need cooling water and as global warming really starts to kick in this commodity is going to be in short supply as evidenced by this news report.

ATHENS, ALA. — The Tennessee Valley Authority shut down one of three units at the Browns Ferry nuclear plant Thursday because water drawn from a river to cool the reactor was too hot, a spokesman said.

The nation's largest public utility shut down Unit 2 about 5:42 p.m. CDT because water drawn from the Tennessee River was exceeding a 90-degree average over 24 hours, amid a blistering heat wave across the Southeast.

"We don't believe we've ever shut down a nuclear unit because of river temperature," said John Moulton, spokesman for the Knoxville, Tenn.-based utility.

He said TVA would compensate for the loss of power by buying power elsewhere. The utility announced earlier Thursday that it was imposing a fuel surcharge on customers because of lower hydroelectric power production caused by drought conditions."

There are two problems here.  One the nuclear plant had to shut down because the river was too warm AND secondly there is not enough hydro to make up the difference.  In this situation a Solar CSP plant would be at it's best performance.

Perhaps we need to figure into nuclear power the cost of the solar CSP plant to back up the intermittent nuclear power.

Comments

[Kirk Sorensen]

"One the nuclear plant had to shut down because the river was too warm AND secondly there is not enough hydro to make up the difference. In this situation a Solar CSP plant would be at it's best performance."

Sorry, wrong again. A concentrating solar plant that uses a steam cycle would need cooling water just the same as the nuclear plant, and if it was here in northern Alabama (with its intermittent and often scattered sunlight) it would be economically located near the river, so as to take advantage of inexpensive cooling water. And if the TVA mandated that the nuclear plant couldn't draw water out the hot river the same thing would be true for the concentrating solar plant.

What I want to know is if they required the Widows Creek coal plant up the river to shut down too, and if not, why?

[Ender]

Kirk - "Sorry, wrong again. A concentrating solar plant that uses a steam cycle would need cooling water just the same as the nuclear plant"

But not in nearly the same quantities and the water can be endlessly recycled without loss of efficiency. As you are not paying for the fuel you can devote some of the plant for re -condensing and cooling the water without loss of efficiency. Also CSP can also be PV plants that do not use water at all.

"And if the TVA mandated that the nuclear plant couldn't draw water out the hot river the same thing would be true for the concentrating solar plant."

A CSP would not be withdrawing water as the lower quantities required for any such plant can easily be met with a condensing plant. As most CSP plants are built in the desert they are always built with low water use in mind. How many NPs are in the desert?

"What I want to know is if they required the Widows Creek coal plant up the river to shut down too, and if not, why?"

They probably did. Just last summer here a couple of thermal coal plants had to shut down because of the same thing.

[Kirk Sorensen]

"But not in nearly the same quantities and the water can be endlessly recycled without loss of efficiency. As you are not paying for the fuel you can devote some of the plant for re -condensing and cooling the water without loss of efficiency. Also CSP can also be PV plants that do not use water at all."

The water drawn from the river isn't used as the working fluid of the plant--it's used for cooling. The working fluid is "endlessly recycled" as you say. For a typical CSP operating on a steam cycle, there would be no difference. The water used in the working fluid loop would have to be recondensed--fundamental thermodynamics--and that heat sink has to come from somewhere. Here in northern Alabama the most attractive thermal sink would be the river. A nuclear plant with 33% conversion efficiency producing 3000 GW of electricity and a CSP system with the same efficiency and the same electrical power generation would consume the same amount of water for cooling. There's no difference except where the heat comes from.

"A CSP would not be withdrawing water as the lower quantities required for any such plant can easily be met with a condensing plant. As most CSP plants are built in the desert they are always built with low water use in mind. How many NPs are in the desert?"

Again, there's no difference in cooling water required for the same power production. Where does the condensing plant get it "cool" from? Is it air cooled? I'm rather familiar with the CSP facilities in Barstow, California and have studied them quite a bit. I'm not sure if they're air-cooled or water-cooled--probably air-cooled. You could air-cool a nuclear plant too but it would be much less economical than using river water. It would be the same way for CSP.

There's CSP systems in the desert but none with anywhere close to the production rate of a typical reactor. Solar Two was 30 MW. A typical nuclear plant is about 1000 MW. And there are a few in the desert--Palo Verde 1,2,and 3 are outside of Phoenix, and use municipal waste water for cooling.

[Kirk Sorensen]

You still have to cool photovoltaic arrays, especially those that work with concentrators. Let's say you have a 20% efficient PV array. Well, 80% of the incident energy heats the array. Since array efficiency drops quickly with temperature, you need to actively cool the array. Most arrays are so incredibly big that air-cooling is sufficient, but when operated with a solar concentrator, if you don't actively cool the array you'll melt the chip. You still need cooling water.

Thermodynamics is thermodynamics.

[Siphon]

That's rubbish Kirk. There is absolutely no need for active cooling in non-CPV. And even for CPV it's not mandatory. There are many CPV designs with high concentration that make use of passive cooling. Heliotube, Amonix, Solfocus and Concentrix are just a few examples.

Facts are facts.

The reason why nuclear power isn't dry cooled, is that this is fiendishly difficult with multi-GW plants. That is, it's expensive, both in capital as well as O&M. It's much more manageable in smaller plants, but that's not cost-effective for nuclear plants.

And nuclear power is already much more expensive than coal when most subsidies are removed. This is why it works well in France (80%), but is pathetic in China (less than 2%). Adding costly dry cooling would make the economics of nuclear fission even more laughable.

The only way nuclear fission could dominate in the USA is with a big fat socialist regime. Odds are that won't happen.