Re: OT: GO SOLAR ! Was: go nuclear. Was: Detecting ETI via CO2

Rob Dekker wrote:
Matt, 

Sorry I got a little busy the past few days.
But here are some notes that might clear up some differences.


I'll address the following issues below :
  - Solar thermal power plants run at 19%+ efficiency (proven).
  - Power distribution over long distances is not a problem at the moment,
and will (have to) be solved in the future any way


	I have now had the time to look into this. As I said, the original was a Visicalc spread***.

I am not prepared to swear to this as yet. I will need a day or three to think about it. I post it to keep the discussion going.

There are two considerations for electricity, peak capacity and total production. US Department of Energy.

http://www.eia.doe.gov/cneaf/electricity/epa/epa_sum.html

Capacity 948 gigawatts

As of January 1, 2004, total net summer generating capacity in the United States was 948 gigawatts, an increase of 4.8 percent from 2002. The industry added 48 gigawatts of net new capacity (in new generators) in 2003. This is the second largest amount of capacity added in any single year, behind only 2002 when 58 gigawatts were added. The recent trend in large natural gas-fired capacity additions continued in 2003. Eighty percent of the new unit capacity was natural gas-fired. An additional 16 percent of new capacity was dual-fired natural gas and petroleum units, most of which utilize natural gas as the primary energy source.

Generation 3,883 billion kW-hr

In 2003, net generation of electricity rose slightly to 3,883 billion kilowatthours. This represents a 0.6 percent growth in electricity generation over the 2002 level; however, it is significantly below the average annual growth rate of 2.4 percent between 1992 and 2003, due mainly to a cooler summer season than the previous year. Regulated electric utilities’ share of total generation continued to decline (63.4 percent in 2003 vs. 66.1 percent in 2002) as IPPs’ share increased (27.4 percent vs. 24.8 percent in 2002). Figure ES 2 shows net generation by energy source.

	Neither of these numbers matches

> How much electricity does the US use ? Must be 250 GW or so peak power usage.
> You need 250 nuclear power plants for that.

> For solar power : At 100% efficiency,  250 GW at 1000 W / m^2 requires 250
> Mm^2  which is an area of about 10x10 miles.

	So right off we have a problem.

The next problem with most websites on solar power do not give the area of the site. When it does it is not clear if it is the total needed area or the amount set aside for the project as they are usually provided as the government's part of the research.

	On this site we find an area discussion that appears to have addressed the land usage.

http://www.accesstoenergy.com/view/atearchive/s76a3993.htm

ERDA is also looking for a site in the sun-belt states for a solar-thermal-electric plant producing some real power 10 MW. Southern California Edison and the Los Angeles Dept. of Water and Power have offered a 130-acre site plus equipment and other resources toward the total cost of $100 million. The site is in the Mojave desert and receives l5% more sunlight than the minimum specified by ERDA. The proposal envisions a 100-acre field of guided mirrors (i.e., mirrors tracking the sun) to focus the incident rays onto a boiler on top of a 300 to 400 ft tower in the center of the field. The steam produced in the boiler would then run a conventional 10 MW power plant, which would, together with other auxiliary facilities, occupy the remaining 30 acres.

Now we assume the need to meet the peak power usage which is A/C and nicely in the summer and a daytime demand so this gives it the best of it. Also the best I can find in discussing the power ratings of these solar sites is rating is by the same peak output. Note this does no address total watt-hours nor does it address using electricity for heating in winter when solar is at a minimum.

So we need to generate 948 GW peak. Here is 10 MW so we need 94,800 sites of this size. At 130 acres per 10MW

948 GW peak

94800 10MW sites

130 acres/10MW

	For comparision a conventional plant needs about 30 acres for a 1GW plant.

12.3 million acres

640 acres/sq. mile

19,200 sq miles

138 miles square

Ohio is roughly 200 miles square or 40,000 sq. miles.

This is before we consider transmission losses. Even sticking with the latitude of the Mohave we have to send power 1500 miles to the north. Interestingly I came across a map showing the sun belt where solar is considered practical and it did not include Florida or eastern Georgia. That implies a very stringent max clouds requirement.

Now we need solar to collect the heat for 3.88 trillion kW-hr in about 11 hrs * .707 (rms) and assume summer heat can be stored over the winter which is dubious to say the least. So lets go for 8 hours of the day at 948 GW. This allows us to produced 948 * 8/24 GW-hrs per day or 316 million kW-hrs per day. Over 365 days that is 115,340 million kW-hr or 115 trillion so that is doable under the given assumptions. Those assumptions being we have neglected electric heating in winter replacing fossil fuel and that summer heat can be stored over the winter.

If the insulation problem is solved for storing heat for the winter, the size of the storage tanks for that heat are going to be multiples of their present size AND the extra heat for winter has to be produced in the summer. So we have to determine the difference between summer and winter available sun. As the peak power was determined for the summer where the latitude is only 15 degrees north of the sun we subtract cos(15) from cost(15+2*23.5) or .496. This requires us to double the size of the solar field.

That gives us 38,000 sq miles. If a miraculous insulation capability is achieved of only 50% lossy we 78,000 sq miles, 2 square Ohios. Roughly 280 sq. miles.

	And still no transmission losses considered.

	Do you disagree with my assumptions or my arithmetic?

	If I remember correctly I assumed only 50% transmission losses and came up with four square Ohios.

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