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Chinese PV are made in a country where electrcity is mainly produced with coal. All construction carbon emission taken into acount, they need around 30 years of use to get carbon neutral, generally more than their expected life time. This is not sustainable at all yet.

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What study says that? These fliers both say less than 5 years for energy payback (as little as 6 months...):

http://www.nrel.gov/docs/fy04osti/35489.pdf

http://www.clca.columbia.edu/236_PE_Magazine_Fthenakis_2_10_...

It doesn't make any sense that China would be subsidizing their panel manufacturers to the extent you are implying.

Energy payback is not the same as carbon neutrality. The former only accounts for the economic value within a regional market and ignores externalities.

Sure but if the energy return is 15x the energy investment, carbon neutrality is pretty likely.

All energy is not created equal. In order to make this calculation in a useful way, one would need to know the amount of carbon emissions per kWh for both the panel production site and ones local grid. And it's actually even harder than that, as one also needs to know if one is lowering base-load generation needs or surge-capacity. Base- and surge-generation are frequently not the same as carbon emissions go.

Consider for instance that you live near the Hoover dam (desert, lots of sun, prime area for solar); your panels might never be carbon-neutral.

Sure, it's complex. Take your example. The Hoover dam sells power into California. So installing solar panels in Boulder City is not that different than installing them in Los Angeles (there would be some extra grid losses in LA). If the Hoover Dam had the capacity to supply the entire southwest it would matter, but it doesn't have that capacity.

There's also the question of whether buying Chinese solar panels makes China more or less likely to convert to solar itself.

Even in a 100%-coal grid, I don't think it's likely that >1000 kg CO₂/kWp is necessary. German manufacturers can achieve 400 kg CO₂/kWp in the still-rather-mediocre German grid.

They are the same.

If energy is the only input to making a solar cell (the worst case) and the cell costs x Wh then the market price can't go below x * ($/Wh), so it pays back when you produced x Wh (thus not buying x Wh from the coal burning power plant) and any energy you produce is both profit for you, and also less total demand for coal energy.

Just compare the price of a solar panel with the price of coal you'd have to pay for in China. That's the uppermost possible limit of what you could expect for CO₂ emissions if you didn't have to pay for anything else. Just conveniently assume all your workers and other raw materials are free. ;) You can probably buy two tonnes of coal in China for the price of a ~250W solar panel. That gives you about 4000 kWh of electricity. At a 15% capacity factor in China, the same panel can generate at least 6500 kWh in 25 years, even including quite substantial degradation. So if used to offset electricity generation within China, it's neutral after 15 years.

In reality, it's most likely much sooner because you don't need 4000 kWh of coal electricity to manufacture a 250W panel; you have to pay your workers and raw material suppliers instead.

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."

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).

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.

You're not taking into account future emissions. If everybody stopped buying PV cells from China, that would severely retard the development and rollout of PV, and so cause more emissions.

China is not the only country which produces PV panels. PV panels are also not the only choice in alternative energy. If one is interested in reducing carbon emissions, it's so much more complicated than "just buy solar".

Not sure. PV generated electricity is around one percent worldwide. CH4 and coal thermal stations have the lowest investment price per kW, so booming economies won't invest massively in PV until CH4 and coal get very expensive. Add to that that PV is very dependent on geography and does not work at night, to make it more than a day peak adjustment you have to also invest in batteries that cost even more carbon-wise.

That country needs to move away from coal as fast as possible for public health reasons and know it. So they'll build massive production capacity anyway irrespective of carbon neutrality etc. (and we in the rest of the world will benefit)

China already has the biggest hydro electric project and I to see massive installations in China for Solar, Wind and Nuclear to combat their air pollution and health problems

'That country'? So does the rest of the world...

You can easily determine that this isn't true on first approximation by multiplying the rated output of the panel by thirty years, and dividing that by the price of electricity. It's well more than the panels are selling for. It wouldn't make any sense for them to sell for so low, so they aren't. It'd be like claiming that the raw materials that go into a $20K car cost $100K. Obviously, they don't.

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