Space based solar power will never be half the cost of nuclear power

Again, it all comes down to the question, which is more cost effective, launching the SPS from earth or building it from lunar or asteroidal materials.

65 Watts per kg is the very best they have ever put in space and really like you say closer to 45 Watts without giving benefit of the doubt Our cells are at 16,800 Watt/kg for 12.4% efficient a-Si. We are working on triple junction that showed 26% efficiency last June. Kevin

> http://www.stretchedlensarray.com/TheProject.htm Entech expects that by 2020 their panels will generate 1KW per kg.

According to that page, Entech has only achieved 45 W/kg, and 2010 is in the future. There's no indication on that page that Entech has achieved anything greater than 45 W/kg.

And it said 2024, by the way.

>That means a 1 GW solar panel would weigh 1,000 tons.

No. A frame sufficient to overcome the tidal forces would be necessary. A very precise aiming system, sufficient to overcome the tidal forces, would be necessary. Station-keeping hardware would be necessary. Transmitting hardware would be necessary.

All dual-axis concentration systems suffer from the aiming problem. This problem grows larger as the size of the array is increased, because of the tidal forces pulling the array out of aim, not to mention bending it.

This is why SPS still costs around a quadrillion dollars per GW.

> We could launch that into LEO for $2.6 B using Falcon-9 (then use ion drive to GEO) .... half the cost of an equivalent nuclear power station.

No. China is building 1.25 GW AP-1000 reactor units for "less than $2000/kW, with this reducing to $1600 for further units":
http://www.world-nuclear.org/info/inf63.html