Sparko, John Reece: solar power not good enough! I: psss!

[Teallaura]

You have to manufacture that many solar cells, and maintain them. They are basically glass. And so they will shatter fairly easily, and you need to keep them pointed at the sun, which you can't do if they are mounted on a roof.

It's just not practical. You are better off using hydroelectric plants to generate electricity. All it takes is water and gravity.

No, the newer cells are much lighter and not as fragile. Roof mounted systems can and sometimes do include adjusters and with sufficient sq footage you don't even need to adjust that much - all are surmountable problems IF - which is the actual problem - solar becomes genuinely cost effective. And I didn't say it was practical NOW - I said that it was possible if solar became cost effective.

Hydro-electric has far more issues with environmentalists - snail darter, anyone? You need a dam for commercial applications and most environmentalists are trying to get existing dams torn down, not new ones built. Hydro needs a LOT or water with sufficient head to work commercially so while it's great here in Alabama it ain't gonna be nearly so easy in Arizona. The last major hydro project was TVA - which was a nightmare to get done. In the current regulatory environment I'm not sure it could be done again.

[Leonhard]

You have to manufacture that many solar cells, and maintain them.

This isn't exactly different from regular power plants you know? It takes a lot of cement to make a nuclear power plant, and not nearly the same weight in glass to set up a solar power array.

They are basically glass. And so they will shatter fairly easily,

Remember to put 'Handle with care' on the boxes with them.

and you need to keep them pointed at the sun, which you can't do if they are mounted on a roof.

You're right that this would definitely be more efficient if they always alligned, but its actually not that important. If you make alligning solar panels then you need bigger gaps betweem them so that they don't fall into eachothers longening shadows. Its easier and cheaper just to put them flat down or at a fixed angle (depending on your lattitude). They'll still produce many times more energy than what went into building them.

[robrecht]

I wish I could find the study that showed that an equivalent sized nuclear power plant takes up more land area in total than solar power does.

Are you speaking 'per Giga Watt'?

[Leonhard]

Are you speaking 'per Giga Watt'?

Pretty much.

If you tear down the nuclear power plant, and fill all its land area with solar panels, you'd get more kilowatthours per day. Of course the nuclear power plant would be chugging along evenly and the solar panels would need a battery back up system and other things to even out production. And would be off during the night. And at the moment would set you back more than what it would cost build a nuclear power plant.

At the moment I'd rather have a nuclear power plant over a solar panel array, though the bad thing about nuclear power plants is that it takes decades to build them. So by the time the plant is ready to start operation solar panels might be a better choice.

[Sparko]

Pretty much.

If you tear down the nuclear power plant, and fill all its land area with solar panels, you'd get more kilowatthours per day. Of course the nuclear power plant would be chugging along evenly and the solar panels would need a battery back up system and other things to even out production. And would be off during the night. And at the moment would set you back more than what it would cost build a nuclear power plant.

At the moment I'd rather have a nuclear power plant over a solar panel array, though the bad thing about nuclear power plants is that it takes decades to build them. So by the time the plant is ready to start operation solar panels might be a better choice.

Yeah.... I don't buy it. Solar power can't generate nearly as much power as a nuclear power plant.

http://www.entergy-arkansas.com/cont...e_Land_Use.pdf

[Leonhard]

Yeah.... I don't buy it. Solar power can't generate nearly as much power as a nuclear power plant.

Lets look at the math together Sparko, I know it sounds incredible and I didn't believe it myself until I sat down and did the numbers on this.

Take a look at this picture

4-nuclearpower.jpg

That's a 1.88GW nuclear power station, and its sitting on 7.9 square miles of land area, supplying daily (average annually) 38GWh. Notice all that space around it with nothing built on it? Now imagine that power plant gone, and we've covered that entire area in solar panels. Nobody has ever built an array that large, an currently nobody have factories that could supply enough solar panels for it, but lets imagine that we did that.

Let's pick 20% efficiency for our solar panels as that's the CdTe thin-film cell efficiency, as well as being a nice round number.

The average annual solar intensity in Arizona in the US comes to around 10 kWh/m²/day. Which works out to 26GWh/squaremile/day. And with the efficiency given it would be 5.2GWh/squaremile/day.

Rounding down our solar panel array would produce 41.2 GWh per day, while the nuclear powerplant would manage 38GWh per day.

Admittedly this is for solar panels in Arizona, but that's where the solar industry is taking off in the US right now.

[Sparko]

Lets look at the math together Sparko, I know it sounds incredible and I didn't believe it myself until I sat down and did the numbers on this.

Take a look at this picture

[ATTACH=CONFIG]2097[/ATTACH]

That's a 1.88GW nuclear power station, and its sitting on 7.9 square miles of land area, supplying daily (average annually) 38GWh. Notice all that space around it with nothing built on it? Now imagine that power plant gone, and we've covered that entire area in solar panels. Nobody has ever built an array that large, an currently nobody have factories that could supply enough solar panels for it, but lets imagine that we did that.

Let's pick 20% efficiency for our solar panels as that's the CdTe thin-film cell efficiency, as well as being a nice round number.

The average annual solar intensity in Arizona in the US comes to around 10 kWh/m²/day. Which works out to 26GWh/squaremile/day. And with the efficiency given it would be 5.2GWh/squaremile/day.

Rounding down our solar panel array would produce 41.2 GWh per day, while the nuclear powerplant would manage 38GWh per day.

Admittedly this is for solar panels in Arizona, but that's where the solar industry is taking off in the US right now.

You can't count unused land.

[robrecht]

Is the unused land actually being used as a kind of safety buffer of any kind? If not, it should not be counted. On the other hand, one should also count any land used for the storage of nuclear waste.

[Sparko]

Is the unused land actually being used as a kind of safety buffer of any kind? If not, it should not be counted. On the other hand, one should also count any land used for the storage of nuclear waste.

I think the point is power generated per sq ft. So unused land, even if used as a buffer should not be counted since it is not generating power. It could also be re-purposed for other uses such as farming, etc.

I linked a pdf above showing the comparison of area of nuclear power compared to wind and solar. And it was generously given a 90% efficiency rate (even though wind and solar come nowhere near that)

http://www.entergy-arkansas.com/cont...e_Land_Use.pdf

Arkansas Nuclear One Station
Power Output: 1,800 Megawatts
Number of Reactors: 2
Land Use:1,100 acres (1.7 square miles)

Nuclear energy is a base load energy source that generates power more than 90 percent of the time,
24 hours a day, 365 days a year on average.

Wind and solar energy sources run average capacity
factors of 33 percent and 25 percent,
respectively.

A 100 percent capacity factor would mean that
the energy source was producing at 100 percent power output every hour of every day of the year.
Assuming the wind and sun were able to generate electricity at a 90 percent capacity factor (of
course the sun cannot shine 22 hours, or 90 percent of each day), land requirements necessary to
generate 1,800 MW of electricity, the equivalent of Arkansas Nuclear One, would be as follows:

Modern Wind Power
Power Output: Above Average Wind Turbine Generates 2.5 Megawatts/turbine
Number of 2.5 MW Turbines Needed to Generate 1,800 Megawatts: 720
Average Acres Per Megawatt: 60
Land Use: 108,000 acres (169 square miles)

Modern Solar Power
Power Output: 1 Megawatt per 7.4 acres of photovoltaic solar panels
Land Use: 13,320 acres (21 square miles)

[Littlejoe]

Lets look at the math together Sparko, I know it sounds incredible and I didn't believe it myself until I sat down and did the numbers on this.

Take a look at this picture

[ATTACH=CONFIG]2097[/ATTACH]

That's a 1.88GW nuclear power station, and its sitting on 7.9 square miles of land area, supplying daily (average annually) 38GWh. Notice all that space around it with nothing built on it? Now imagine that power plant gone, and we've covered that entire area in solar panels. Nobody has ever built an array that large, an currently nobody have factories that could supply enough solar panels for it, but lets imagine that we did that.

Let's pick 20% efficiency for our solar panels as that's the CdTe thin-film cell efficiency, as well as being a nice round number.

The average annual solar intensity in Arizona in the US comes to around 10 kWh/m²/day. Which works out to 26GWh/squaremile/day. And with the efficiency given it would be 5.2GWh/squaremile/day.

Rounding down our solar panel array would produce 41.2 GWh per day, while the nuclear powerplant would manage 38GWh per day.

Admittedly this is for solar panels in Arizona, but that's where the solar industry is taking off in the US right now.

Hi Leonhard, where did you get your figure for 10KWh/m²/day figure? The map at this website shows it to be 1/2 that. Which would be 5KWh/m²/day. That would effectively cut your estimate in half to 20.5 GWh per day.

[Teallaura]

Hi Leonhard, where did you get your figure for 10KWh/m²/day figure? The map at this website shows it to be 1/2 that. Which would be 5KWh/m²/day. That would effectively cut your estimate in half to 20.5 GWh per day.

Um, I think he's averaging winter and summer - your map appears to be the winter map (yes, they are confusing as heck). Here they are shown together. Your map agrees with the winter but not the summer.

[Leonhard]

Hi Leonhard, where did you get your figure for 10KWh/m²/day figure?

http://rredc.nrel.gov/solar/old_data...tlas/serve.cgi

Pick annual average, horizontal flat arrangement (no tracking).

[Leonhard]

You can't count unused land.

Says who? Nuclear Power Plants have a massive buffer zone, usually of land that isn't and can't be used for crops (otherwise building there would be way too expensive).

We can keep redefining the problem until one of us wins. I just wanted to show you that nuclear power doesn't really fit into a much tighter space than solar power. If you're ready to sacrifice thousands of square miles of land for nuclear power, its odd to complain about solar power taking up much space.

Even if solar took up three times more space it wouldn't be much of an argument against it. The US lacking in ground you can build on. Its harder in Denmark where most of the ground which isn't cities, consists of farms. Here we'd have to trade off ten percent of our arable land.

[Littlejoe]

Um, I think he's averaging winter and summer - your map appears to be the winter map (yes, they are confusing as heck). Here they are shown together. Your map agrees with the winter but not the summer.

Your link has winter as 4.5-5.0 and Summer around 7.0 That would be an average of 6.25? Still not 10 as Leon quoted.

Hmmm...According to the site I linked to, it says above the first map:

The following maps give an example of the amount of energy falling on a particular place on earth as a yearly average. Remember these figures will increase in the local summer months and decrease in the local winter months. The numbers represent the amount of energy from sunlight in Kilowatt-hours that falls on a square metre of land per day.

[Littlejoe]

http://rredc.nrel.gov/solar/old_data...tlas/serve.cgi

Pick annual average, horizontal flat arrangement (no tracking).

When I do that, it looks like it agrees more with my number than yours.... Around 6 -7 KWh