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Old 12-15-2018, 10:47 PM   #4137 (permalink)
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Originally Posted by aerohead View Post
I watched all of the David MacKay video today.
MacKay was a physicist so everyone here should automatically respect him better than some of my other sources. He was pro rebuildable energy but also "Pro Arithmetic". Numbers like TeraWatt are so big that they are hard to grasp so he coined an interesting term to bring total energy down to an everyday scale.
Most people are familiar with an incadescent light bulb. A 40 Watt bulb that is left on uses approximately 1 kWh per day. So he talks about kWh/ day/ person.
The USA uses 250. The UK, Netherlands, or Germany use between 120 to 140.
The problem with solar wind and biomass is that they are very difuse. Here is his chart of power density.

When he made the graphic to show the required land area that is needed to supply 125 kWh/ d/ p for the UK he ran out of room to fit biomass into view so keep in mind that this only shows what it takes to make 16 so this is 1/8th of the area that would be required to power the UK. He also shows concentrated solar in an African desert and gives it a value of 20W/m^2 even though he stated that solar PV rooftop can make 5W/ square meter, gridscale farms in the UK at 4w, and concentrated in the desert at 11w. So multiply everything on the map by 8 to get to 125 kWh/d/p and then the yellow area again by 4 to show solar PV farms at 5W/m^2.
MacKay stated that UK is conuming 1.25 Watts per square meter. To power the UK on wind would need wind farms over 1/2 of the land area. Solar farms would have to cover 1/4 of the land. And would provide 4 times too much energy at noon and nothing all night.
To power a country with wind and solar, they have to be country sized.


Last edited by sendler; 12-16-2018 at 08:10 AM..
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