PV Gap

Jean Said:

solar power - any new developments?

We Answered:

There's only about a kilowatt of solar power hitting each square metre of the Earth's surface when the sun is at zenith (i.e. directly overhead) which is even available to harness and that power isn't reliable (things like night and clouds can cause you problems along with seasonal variations reducing the insolation).

If you have 30 m^2 of roof space then the maximum theoretical power you could possibly get out of solar would be around 30 kW but only if the sun is right overhead and the sky clear (you'd need to be between the tropics and you'd only get that at noon on two days a year). In the real world at about 40° of latitude or so you can expect to lose about half the noon insolation due to the angle of the sun with the change in angle going through the day reducing it to low single figures.

Then when you factor in that even really expensive solar cells are around 20% efficient and that small scale inverters along with energy storage systems have some inefficiency it becomes pretty clear that a home solar power system won't power everything you want to run.

Low power emergency equipment like roadside satellite phones can run fine from solar and backup batteries and solar water heating is great but for serious stuff the energy just isn't there (at least not enough to make ground based solar viable without massive environmental destruction).

Jeffery Said:

Need help with solar power?

We Answered:

Assume the solar cell is positioned perpendicular to the arrival angle of the sun's light. The solar insolation value is

p: solar insolation = 1000 W/m²

The power incident on your solar cell is

P: power = 1000 W/m² * 1.6 cm *3.6 cm = 0.576 W

I assume that when you say power is consumed in the solar cell, you are referring to inefficiencies in the light-to-electricity conversion process.

P_Available = 0.576 W -0.300 W = 0.276 W

Marcus Said:

Why aren't cell phones solar powered using photocells/Photovoltaic?

We Answered:

It's called space-based solar power, and a lot of people are taking it seriously.

The most commonly suggested transmission technology would be a beam of microwave radiation, from the satellite to Earth.