Measuring Solar’s Total Impact
Renewable energy generates clean power, and the fuel is often free: There’s no cost to make the wind blow or the sun shine. But just as many people advocate for considering the full cost of fossil fuels in the price of electricity (the cost of the pollution, mining, etc), so too must the full cost and impact of renewable energy be accounted for.
A new life-cycle assessment study from the Brookhaven National Laboratory in New York examined the four most common types of photovoltaic (PV) solar power cells — multicrystalline silicon, monocrystalline silicon, ribbon silicon and thin-film, if you were wondering — to find out how much energy and waste was involved in their creation.
“Emissions from Photovoltaic Life Cycles” found that even when accounting for the metals required to build PV cells, the efficiency of the cells, and the waste produced, PV cells still emit less global warming pollution throughout their life cycle than the fossil fuels needed to produce the same amount of power. Actually, most of the pollution from the solar power comes from the indirect emissions of the fossil fuels used to generate the electricity of the PV manufacturing facilities.
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The most energy-intensive type of PV cell to make — the monocrystalline silicate cells — only emits 1.8 ounces of global warming pollution per kilowatt hour, compared to 2.2 pounds by a coal-fired power plant. All told, the construction and use of PV power would cut air pollution about 90 percent if it replaced fossil fuels.
The best-case scenario, of course, would be for solar manufacturing facilities to be powered by solar. Researchers concluded that 30 percent of the energy used to make PV cells could come from solar power installed on the roofs and parking lot of facilities.
While some people point out that the study only partly takes into consideration the transportation of PV components (most of which are made in China), the researchers want to broaden their work further to include end-of-life and recycling data of the PV cells. They believe this expansion could further improve overall emissions calculations.
Nanowerk
Scientific American
Treehugger
Great reply Paul D., but the logic of your second-to-last paragraph leaves your argument open for some criticisms. I would ask that you please not get too angry with me by the following dissection, because we are all friends here - even though we have differences of opinion.
Your comments imply that GHG’s only absorb reflected energy from the ground, but none of the energy that comes from the sun. How would this be possible? How would CO2 molecules floating around in the atmosphere determine which heat sources to absorb and which to ignore? You also say that most of the reflected energy actually escapes into space, which would be a good thing from a global warming perspective. What? If the already high concentration of GHG’s are absorbing only reflected heat and warming the planet, why would we want to reflect more heat and compound the problem? Seems like the wrong thing to do considering the crisis and looming doom.
Maybe your statements should have flowed more like this:
If we continue emitting large amounts of CO2 while we work towards converting to 3/4 solar power and survive the heating that we inadvertently speed up by reflecting more heat into an atmosphere already overburdened with reflective-heat-capturing CO2, some day in the future when the atmospheric CO2 returns to its natural percentage of 0.0300% instead of today’s extremely high 0.03811% the world will cool down to the levels that nature intended. Sure the process will take hundreds of years for the correction to occur, but the effort will have been well worth it.
Please remember, we are all friends here.
Bobby, not a bad summation.
I think you misunderstand my point about reflection vs absorbtion. Given an overly warm planet, more reflection is better than more absorbtion.
I did not mean to imply that incoming solar radiation is not absorbed by GHG’s, only that trapping reflected light/heat energy is the bigger problem. (incoming energy that’s absorbed by the atmosphere would otherwise reach the ground anyway)
Whether it is the ground or the atmosphere holding the heat, it is the total absorbtion of thermal energy that is the problem. Our planet was designed to absorb a certain amount of solar radiation and reflect the rest into space. We have thrown it out of balance.
Setting aside the babbling nonsense…
It’s worth noting that the linked study giving us 20-55g CO2e per kWh (see here) doesn’t look at installation, maintenance and decommissioning.
You don’t just drop the PV panels in a field and forget them, but must give them a solid base - typically concrete, with roughly 1kg CO2e emissions per kg - must empoly someone at least to polish them occasionally, and at the end of their useful life they must be removed and replaced, and their materials disposed or or recycled.
Considering the complete lifecycle gives us figures closer to 100g CO2e per kWh. This varies quite a bit. Obviously if you put the thing in Sweden it’s going to give you less power than if you put it in the Sahara, but all the other emissions will be the same, so the emissions per kWh will be lower in Sweden than the Sahara.
Likewise, local conditions will affect how much concrete needs to be used for foundations, and so on.
But we can take as a good rough figure 100g CO2e/kWh. So far as I know, no-one has done complete lifecycle assessments of coal-fired stations, but just the coal makes them 1,325g CO2e/kWh.
The lowest complete lifecycle emissions anyone’s established so far are with wind turbines, at around 50g CO2e/kWh. While they need a lot of concrete for their foundations (a 1.5MW turbine will need 200-450t), producing their materials isn’t as energy-intensive as solar photovoltaic, they don’t need purified silicon, cadmium, gallium or anything fancy like that.
Unfortunately, concrete seems to be the weakest link in the emissions chain. In theory we could produce all the minerals and materials for the renewable generation from renewable energy itself; but concrete requires cement, which is produced by roasting limestone and driving off the carbon dioxide. Worldwide some 5-10% of our CO2 emissions are from making concrete. Since it’s a chemical process, how the stuff is roasted doesn’t matter…
Yeah, maybe so. I will concede that there are forces at work that neither you nor I (nor the greatest IPCC approved scientists) fully understand. There is a balance to be maintained. That’s a given.
The atmosphere does act as a blanket that blocks and retains heat simultaneously. The blanket allows some (but not all) heat to reach the surface during day time hours to be absorbed by the land and seas. A portion of that heat gets released skywards during the nighttime hours, but not all of it reaches outer space. Now this is a good thing, or else the planet would cook during the day and freeze during the night ultimately making it uninhabitable.
I really find it interesting that you say that our planet was “designed to absorb a certain amount of solar radiation and reflect the rest into space”. Your use of the word “designed” indicates a belief in a Designer/Creator, as opposed to the miraculous accident that came to be via the big bang. That leads to a few additional (and possibly off topic) questions. Who designed it? Why would this creator/designer abandon his marvelous creation to let human invaders destroy it? What threw the creation out of balance so many times over millions of years before the advent of man?
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