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Scipplets, where are the numbers from?

Over at the CEP page:
http://cleanenergy.harvard.edu/

There is a Scipplet at the right-bottom, I think it's random showing a few different ones. On one of them there is numbers. It' has title "Lets go solar!".

Where are those numbers from? And can one actually compare those numbers. I can't get it right.

Looking things up on Wikipedia etc:

In 2008, total worldwide energy consumption was 474 exajoules (474Ã10^18 J=132,000 TWh). This is equivalent to an average energy consumption rate of 15 terawatts (1.504Ã10^13 W).[1] The potential for renewable energy is: solar energy 1600 EJ (444,000 TWh), wind power 600 EJ (167,000 TWh), geothermal energy 500 EJ (139,000 TWh), biomass 250 EJ (70,000 TWh), hydropower 50 EJ (14,000 TWh) and ocean energy 1 EJ (280 TWh).[6]

http://en.wikipedia.org/wiki/World_energy_consumption

Also see:
http://en.wikipedia.org/wiki/Solar_energy

89 != 120?? so wheres are the numbers from, and what are they representating.

[Mar 31, 2012 1:28:03 PM]

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Re: Scipplets, where are the numbers from?

Look up David MacKay who's name is printed right hand bottom of many of the info blobs http://www.google.com/search?client=ubuntu&am...amp;ie=utf-8&oe=utf-8

--//--

[Mar 31, 2012 4:07:23 PM]

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Re: Scipplets, where are the numbers from?

I guess the two sources refer to different ways of estimating the amount of energy available from each renewable source. Particularly for solar energy, wikipedia refer to a calculation of how much of the solar energy reaching earth can be converted to usable energy, whereas our number refers to the total energy that reaches earth, which is four orders of magnitude larger than current human consumption. Comparison of the two sets of numbers is presented below:


		Joules	        TWh	        TW							TW	        TWh	        Joules
Consumption	4.74E+20	1.32E+05	1.50E+01		current world use	        1.50E+01	1.31E+05	4.73E+20
solar	        1.60E+21	4.44E+05	5.07E+01		solar energy striking the earth	1.20E+05	1.05E+09	3.78E+24
wind	        6.00E+20	1.67E+05	1.90E+01		extractable wind power	        4.00E+00	3.50E+04	1.26E+20
geothermal	5.00E+20	1.39E+05	1.59E+01		geothermal over all land area	1.20E+01	1.05E+05	3.78E+20
biomass	        2.50E+20	6.94E+04	7.93E+00					
hydropower	5.00E+19	1.39E+04	1.59E+00		hydroelectric	                5.00E-01	4.38E+03	1.58E+19
ocean	        1.00E+18	2.78E+02	3.17E-02		tides and ocean currents	2.00E+00	1.75E+04	6.31E+19

Our source for these numbers is

Prashant V. Kamat. Meeting the Clean Energy Demand: Nanostructure Architectures for Solar Energy Conversion. Journal of Physical Chemistry C 2007, 111, 2834-2860 (numbers on page 2835)

[Mar 31, 2012 9:51:24 PM]

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Re: Scipplets, where are the numbers from?

Thanks for the reference.

I found that the Wikipedia solar energy page has this as reference: http://www.vaclavsmil.com/publications/ and you can find the same number there:

Insolation (at 122 PW) is the only renewable flux that is nearly 4 orders of magnitude greater than the worldâs TPES of nearly 13 TW in the year 2005.

It is the other number that don't match, it says it's 174 PW (this number also from Smil) from beginning and after reflection and absorption it's only 89 PW left. It's like the absorption is included in those 120 PW, and thats what the wiki text and image says:

"The total solar energy absorbed by Earth's atmosphere, oceans and land masses is approximately 3,850,000 exajoules (EJ) per year.[7]"

The image also has this information and it is a derivate from this:
http://education.gsfc.nasa.gov/experimental/a.../trl/inv2-1.abstract.html

[Apr 1, 2012 5:29:34 AM]

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