Powering the World by Solar

All of us reading this, use electricity, and why shouldn't we. It powers so many useful items in our homes, it powers industry, and can power transport. Plus, once it has been generated, by whatever means, it is a very clean source of energy.
It is not surprising then, that the use of electricity expected to increase considerably.

According to a report from the US Government Energy Information Administration a total world electricity consumption of approximately 17 trillion Kwhours in 2005, is expected to rise to 24 Trillion by 2015, and 33 Trillion by 2030.
1 Trillion = 1,000,000,000,000

So what are the chances of generating this lot from solar power?
The better parts of the world for insolation (amount of solar power received from the sun) receive an average of around 250 watts/m² (night and day, 365 days per year)
That amounts to around:
250x24x365/1000 = 2,190 Kwhours per year.

Or we could say that a sq. Km receives around:
2,190x1000x1000 = 2.19 billion Kw hours per year.

Following on from this, we can calculate that:
33 trillion/2.19 billion = 15,000 sq Km would receive enough energy to meet the requirements of 2030.

If we assume that our method converting that energy is only going to be 15% efficient, then we would need 100,000 sq Km.
Then perhaps we would need to double that to allow room for roads and other infrastructure within our solar collecting area, so requiring 200,000 sq Km of the earths surface.
That's a lot of space, but when you consider that the Sahara desert is around 9 million sq Km,the Arabian desert and the Australian Great Sandy desert are both around 2.3 million sq Km, these sort of areas are available.

OK, so the above was not intended to suggest that all the worlds electricity should be produced in the Sahara Desert, but was an exercise to illustrate how only a small proportion of the earths surface could produce all the worlds electricity.

According to figures produced by the Organisation for Economic Co-operation and Development, the proportions of electricity produced produced by different methods in OECD counries was as follows in 2008
Combustible Fuels: 64%
Nuclear: 20%
Hydro: 13%
Geothermal/wind/solar/other: 2%

Accepting that solar (and wind) have the disadvantage of not being able to continually produce electricity, there is still clearly scope for a much greater proportion to be produced by solar.