[thackney]

Ultimately, the report estimates, a single kilometer-wide array could collect enough power in one year to rival the energy locked in the world’s oil reserves

That got my attention

It should, it is total BS. It makes the rest of the article not worth reading. The author either doesn't know what he is talking about, or he is a liar.

The sun provides about 1,365 watts per square meter of energy at the Earth's orbit.

A Fresh Look at Space Solar Power
http://www.spacefuture.com/archive/a_fresh_look_at_space_solar_power_new_architectures_concepts_and_technologies.shtml

1 sq meter would provide 11,957 kWH per year of power.

1 km x 1 km would provide 11,957,400,000 kWH per year.

1 KilowattHour = 3,412 Btu

1 Barrel crude oil = 42 U.S. gallons = 5,800,000 Btu

Energy Calculator - Common Units and Conversions
http://www.eia.doe.gov/kids/energyfacts/science/energy_calculator.html

1,317,447 million barrels of oil in latest estimate of world's proved reserves. Note: this only includes reservoirs which have been drilled and flow tested. It does not include areas like ANWR and much of our deep water that is not proved to have the quantities of oil estimated by geological study.

World Proved Reserves of Oil and Natural Gas
Oil, Oil & Gas Journal, January 1, 2007
http://www.eia.doe.gov/emeu/international/reserves.html

11,957,400,000 kWH x 3,412 Btu / kWH = 40.8 Trillion Btu

1,317 billion barrels x 5,800,000 Btu / barrel = 7,641,192.6 Trillion Btu

It would take that Solar Array over 187 thousand years just to equal the oil we have left in explored reservoirs.

We use oil, because it contains a lot of energy.

[thackney]

That is it would take that long if they could capture 100% of the solar energy at perfect efficiency. At a realistic 15% capture, store and transport, it would take 1.2 million years.

[shove_it]

Thanks. I thought it sounded a little high.

[Thermalseeker]

We use oil, because it contains a lot of energy.

Very true, and a point that is totally lost on most Libs. If there were a better alternative, we'd already be doing it. It's perfectly okay with me if the enviroweenies want to drive shoe boxes and believe in fairy tales. Just don't get mad a me when I mistake your econobox for a speed bump in my turbo diesel F-250 4WD......which, btw, gets 26 mpg while carrying several of those econoboxes the Libs love to drive.....

[burzum]

I had to check the numbers myself. Instead I just used 20 million barrels per day of oil to see how well it would do to replace US energy usage. The energy stored in the oil used in one day is 1.22 * 10^17 J. The energy incident on a square array (in a place where it won’t be eclipsed by the Earth often such as a geostationary orbit) is 1.17 * 10^14 J.

To be fair, the article only said a single kilometer-wide array. It *could* be 1000 km long! I also didn’t take into account the efficiencies of transmission or thermodynamics. I’m just drawing a rough conclusion to within an order of magnitude.

Of course when you look at worldwide energy usage of 15 TW, this idea is laughable. Overall 1.3 * 10^18 J are used per day. So now we have a 100 km by 100 km array (or perhaps 1 km by 10,000 km to meet this article’s requirements).

[Hardastarboard]

We use oil, because it contains a lot of energy.

I look at oil as sort of like earth's batteries, where it's stored the accumulated energy of millions of years of sunshine (if you believe the dead dinosaur theory of oil). Since you are clearly versed in this subject, my question is what happens if we actually do use up all the oil? Is it even possible to produce the energy the world requires even at current levels (disallowing for growth) without oil, from ANY source? I would guess nuclear power would work, but it's not portable / storable like petroleum energy is.

[Cvengr]

One major efficiency in solar collection is the amount of heat loss in solar energy absorbed by the atmosphere. Politically, the idea might be also advanced by reducing the dreaded ‘global warming’.

On the other hand, getting that power back to earth is another issue. In the late 70s we had looked at microwaving it back to large collector arrays in the ocean. Of course it might not be so good for birds flying in the area, planes or submarines.

[Cvengr]

I forgot to mention, one impediment to space based solar arrays was the lack of atmosphere on photoelectric materials. The partial pressure for many of those materials would result in their outgassing over time, especially as they heated up during the photoelectric process. I don’t know the state of the art, but that was a purely intellectual exercise back then.

[hippyhater]

http://www.nss.org/settlement/ssp/library/final-sbsp-interim-assessment-release-01.pdf from page 8 of the pdf (page 6 of the document) A single kilometer‐wide band of geosynchronous earth orbit experiences enough solar flux in one year (approximately 212 terawatt‐years) to nearly equal the amount of energy contained within all known recoverable conventional oil reserves on Earth today (approximately 250 TW‐yrs). Pg 11 of the pdf (pg 7 of the document) Typical reference designs involved a satellite in geostationary orbit, several kilometers on a side, that used photovoltaic arrays to capture the sunlight, then convert it into radio frequencies of 2.45 or 5.8 GHz where atmospheric transmission is very high, that were then beamed toward a reference signal on the Earth at intensities approximately 1/6th of noon sunlight. The beam was then received by a rectifying antenna and converted into electricity for the grid, delivering 5‐10 gigawatts of electric power.

[hippyhater]

http://www.nss.org/settlement/ssp/library/1981NASASPS-PowerTransmissionAndReception.pdf

[timer]

good number crunching. Once again it’s an area vs volume ratio. Solar has to cover huge AREAS, oil/coal is already bunched up into small VOLUMES.

[NYCRebublican]

Is that 1,365 watts per sq. meter per day?