The total area of solar panels it would take to power the world, Europe, and Germany

[kg4jxt]

177. solar constant - to whom it may concern

just FYI (not directed to Erich specifically), the solar constant is 1360 W/sq. m - that is the solar radiation intensity at the distance from the sun to the earth. The atmosphere absorbs a little bit of the radiation (or a lot if it is cloudy), and the angle of the sunlight on a solar panel affects the amount of power captured. Some solar panels have been made approaching 30% efficiency, but most commercially made panels are around 15%. So a typical square meter panel has a rated capacity around 150 W.

The effective output of solar panels is generally estimated at 6 hours per day, or 0.9 kWh per sq. m; but with sun tracking (which greatly increases the installation cost of the panel array), the effective output can be increased by 50% or more.

Worldwide energy production, according to Wikipedia, for 2008 was 143,851,000,000,000 kWh and increasing at a rate of around 2-5% annually. So, now you can calculate worldwide solar panel demand.

As for batteries, they are a real problem so far. I live on a bank of 20 golf cart batteries, but I do not run air conditioning and sometimes the lights dim when the washing machine starts. So it is a marginal case. Charging efficiency is only about 80%. Pumping water up a hill and regenerating the power when the water runs back down, or driving a locomotive up a mountain and letting it roll back down - these types of kinetic storage are in use along with others, but they are even more inefficient: water pumping and regeneration is only about 30% efficient, a locomotive can do a little better (but costs more).

Several others discuss the transmission problem so I will not belabor it.

Think globally and act locally. Different locations can have different solutions. Solar is pretty easy at the household level; it is getting affordable for most people in the US now. But it is certainly not as easy as hooking to the grid.