This site has a global map which shows the land area required to replace all current forms of energy ...coal, oil, gas, hydro, nuclear (roughly 18 Terawatts...trillion watts) with solar power at 8% conversion rates....some systems do much better than that so required land areas would be smaller.
http://www.ez2c.de/ml/solar_land_area/
"New World Record Achieved In Solar Cell Technology
ScienceDaily (Dec. 7, 2006) — U.S. Department of Energy (DOE) Assistant Secretary for Energy Efficiency and Renewable Energy Alexander Karsner has announced that with DOE funding, a concentrator solar cell produced by Boeing-Spectrolab has recently achieved a world-record conversion efficiency of 40.7 percent, establishing a new milestone in sunlight-to-electricity performance. This breakthrough may lead to systems with an installation cost of only $3 per watt, producing electricity at a cost of 8-10 cents per kilowatt-hour, making solar electricity a more cost-competitive and integral part of our nation's energy mix"
http://www.sciencedaily.com/releases/2006/12/061206123954.htm
"Australian and U.S. researchers have teamed up to create a breakthrough in solar efficiency.
A solar energy team from the University of New South Wales (UNSW) ARC Photovoltaics Centre of Excellence, along with two U.S. groups, have achieved a new world record of 43 per cent of sunlight converted into electricity"
http://www.thetechherald.com/article.php/200936/4334/New-world-record-in-solar-efficiency
"Researchers On Their Way to Set Solar Panel Efficiency Record at 95%
It’s natural that solar panels should get better and better, just like any other form of technology, especially one that is of relative recent development. But to hear of an improvement in solar panels that is unlike any breakthrough so far is clearly set to raise some eyebrows among buyers and investors.
The breakthrough comes from chemical engineer Patrick Pinhero at the University of Missouri, who claims his solar panels are way better than those on the market now: up to 95% efficiency.
To be more explicit, the best job existing photovoltaic panels (PV) can do right now is a 20% rate of collecting the sunlight.
Pinhero started from the premise that the sunlight spectrum is a lot wider, including the near-infrared region of it. So he created a device which incorporates a sheet of small antennas, whose sole purpose is to harvest as much solar energy as possible. The technology already found its application in the industrial field, where it can take in the heat and give out electricity."
http://www.greenoptimistic.com/2011/05/19/pinhero-infrared-solar-cell/
Thin-cell solar systems...
http://www.youtube.com/watch?v=-XIL9BgPZX0&feature=related
http://greenchemistry.wordpress.com/2008/01/21/nanosolar-powersheet-the-paper-thin-solar-cell-that-could-change-the-world/
Converting all cars, trucks and trains to run only on electricity may be a problem though as rare earth minerals and lithium required for motors and batteries might become scarcer and more expensive as demand rises. China is a major supplier today and is alreading hoarding such supplies...Bolivia has perhaps 50 percent of the world's supply of lithium.
" The United States risks major supply disruptions of rare earth metals used in clean energy products unless it diversifies its sources of the minerals, the Energy Department warns in a report due to be released later on Wednesday.
The United States and other countries are worried that China, which controls 97 percent of the world trade in rare earth metals, will use those supplies as a political weapon and cut back their export when it is in a dispute with another country or to grow China's clean energy technology sector."
http://www.reuters.com/article/2010/12/15/us-usa-rareearths-energy-idUSTRE6BE1D320101215
" A Canadian company hoping to compete with China's near-monopoly of rare earth elements — metals critical for everything from U.S. military weaponry to wind turbines — wants to open a strip mine inside a national forest in northeast Wyoming.
Processing raw ore into rare earths is an intensive operation that has been associated with radioactive water spills. But with China slashing exports of rare earths and Washington concerned the U.S. military could face a shortage of materials for lasers, smart bombs, guided missiles, night-vision goggles and jet engines, Don Ranta is optimistic about his Black Hills National Forest mine proposal."
http://news.yahoo.com/s/ap/us_rare_earths_rush;_ylt=ApbLso6VF0.ZAm4LEbrwnegXIr0F;_ylu=X3oDMTJ2M2VhaTIwBGFzc2V0A2FwL3VzX3JhcmVfZWFydGhzX3J1c2gEY2NvZGUDdmlld3NoYXJlBGNwb3MDMTAEcG9zAzEwBHNlYwN5bl90b3Bfc3RvcmllcwRzbGsDaW53eW9taW5ncHVz
"The Lithium used in electric cars is not a renewable resource (Part 2 / 2)
http://frenchsciencesf.wordpress.com/2011/03/25/the-lithium-used-in-electric-cars-is-not-a-renewable-resource-part-2-2/