[subtenante]

Don't have the details of the study, it was from an informal evaluation from Jean-Marc Jancovici, a well known (in France) climate/energy specialist. A similar argument is made here:

http://spectrum.ieee.org/green-tech/solar/solar-energy-isnt-...

Related quote: "If the photovoltaic panels made in China were installed in China, the high carbon intensity of the energy used and that of the energy saved would cancel each other out, and the time needed to counterbalance greenhouse-gas emissions during manufacture would be the same as the energy-payback time. But that’s not what’s been happening lately. The manufacturing is mostly located in China, and the panels are often installed in Europe or the United States. At double the carbon intensity, it takes twice as long to compensate for the greenhouse-gas emissions as it does to pay back the energy investments."

[maxerickson]

It's not that similar an argument, it suggests a carbon payback time of 3-10 years, not 30 or never (10 years is unfortunate but workable (especially if you expect it to improve, which is basically guaranteed), 3 years is fine, never would be unacceptable).

[subtenante]

True, that depends on the country where the PV panel is installed. The original argument was probably made for France where electricity is very low on carbon.