[hugh3]

Yes and no. I don't think it's an empty tree hugger comment, but I do think we need actual numbers in order to discuss these things.

World energy usage: 474 exajoules per year

Incident solar flux: 1000W per square metre

Let's suppose (optimistically but not unrealistically) we can get 10% efficiency (over day and night, so more like 20% during the day).

How much land (or indeed, water) do we need to cover with solar cells? About 150,000 square km.

So, while the cost of building all these solar cells is significant, the proportion of the Earth's surface they take up isn't.

[jerf]

When people propose the "cover 150,000 km^2 with solar cells solution", I like to see them go on the record as saying that if we actually tried, they would not immediately turn around and start screaming about the 150,000 km^2 of Mother Earth we just converted to industrial land.

Solar of any form has a major power density problem. At least, it does in the biosphere, which it should be observed is only a rather small percentage of the universe....

[hugh3]

I like to see them go on the record as saying that if we actually tried, they would not immediately turn around and start screaming about the 150,000 km^2 of Mother Earth we just converted to industrial land.

Oh, don't get me confused with a tree-hugger. I'm about as anti-greenie as you can get. I'm just here to do the mathematics.

I'm for whatever source of energy is cheapest.

[MichaelApproved]

Transporting electricity is expensive and inefficient. If you take 150,000 sq km of the most efficient solar land, you still have the problem of transporting the electricity created from that to the places that need it.