SUNNY DAY: Even accounting for all the energy--and pollution--involved in the manufacture of photovoltaic cells, they still produce less pollution over their lifecycle than other alternatives.
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It takes power to make power—even with a solar grand plan. From the mining of quartz sand to the coating with ethylene-vinyl acetate, manufacturing a photovoltaic (PV) solar cell requires energy—most often derived from the burning of fossil fuels. But a new analysis finds that even accounting for all the energy and waste involved, PV power would cut air pollution—including the greenhouse gases that cause climate change—by nearly 90 percent if it replaced fossil fuels.
Environmental engineer Vasilis Fthenakis, a senior scientist at Brookhaven National Laboratory in Upton, N.Y., and his colleagues examined the four most common types of PV cells: multicrystalline silicon, monocrystalline silicon, ribbon silicon and thin-film. (Other contenders, such as amorphous silicon or superefficient multijunction cells were excluded for lack of data or lack of widespread application to date.) Even taking into account the low efficiency of thin-film solar cells or the energy needed to purify silicon for the other types of PV, all proved to entail significantly fewer emissions in their entire life cycle than the fossil fuels needed to produce an equivalent amount of electricity.
In fact, most of their dirty side derived from the indirect emissions of the coal-burning power plants or other fossil fuels used to generate the electricity for PV manufacturing facilities.
These four types of solar cells pay back the energy involved in their manufacture in one to three years, according to an earlier analysis by the same team. And even the most energy-intensive to produce—monocrystalline silicate cells with the highest energy conversion efficiency of 14 percent—emit just 55 grams (1.9 ounces) of globe warming pollution per kilowatt-hour—a fraction of the near one kilogram (2.2 pounds) of greenhouse gases emitted by a coal-fired power plant per kilowatt-hour.
Even though thin-film solar PVs employ heavy metals such as cadmium recovered from mining slimes, the overall toxic emissions are "90 to 300 times lower than those from coal power plants," the researchers write in Environmental Science & Technology.
The energy benefits of solar photovoltaics will only improve as the technology continues to boost its efficiency at converting sunlight to electricity or proves to last longer than the 30 years anticipated by manufacturers. "There is no reason for this not to last a lot more than 30 years," Fthenakis says.
If solar energy begins to power its own production—a so-called PV breeder cycle, in which PV-generated electricity goes to produce more PV cells—the outlook is even sunnier. "I think 30 percent of the energy consumption in the [manufacturing] facilities is easily met from the land they have available [on] the roof and in the parking lot," Fthenakis says.
And, as Fthenakis and colleagues argued in a recent article in Scientific American, if storage technologies such as compressed air improve, then PV could provide the majority of electricity needs in the U.S. "With storage," Fthenakis says, "it is feasible to go to 100 percent."
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16 Comments
Add CommentNow if we could only get the price down enough to put these on every roof in America.
Reply | Report Abuse | Link to thisOf course they didn't include nuclear power in their study.
Reply | Report Abuse | Link to thisI have to question that 1-3 years to return energy that went into making them figure. Previous studies I have seen say 5-10 years. Few solar cells are sited perfectly. Different locations have highly varying solar power available. Few cells are kept scrupulously clean, etcetera. I strongly suspect the figure in this article uses a 1KW per square meter x 12 hrs. This would be unrealistic, since that's the high-noon figure.
Reply | Report Abuse | Link to thisAside from that, I agree, and I also think 30 years is too short. I also think they should be working out figures for solar satellites in geosynchronous orbit beaming energy to earth as microwaves. This is probably the best option for a nation like China.
The 1-3 year figure is based on 1800 kilowatt-hours per meter-squared per year, which is the average insolation in the U.S. What that means is the figure is far less for areas where solar is widely used, such as the Southwest, which have much more sunshine. But yes, it is an average figure and therefore should be treated with caution.
Reply | Report Abuse | Link to thisAs for nuclear, the energy payback time is not particularly good for such plants, given the massive amounts of steel and cement required to build them. But they certainly share solar's lack of fugitive emissions.
Finally, as far as putting them on roofs goes, well, that might not be cost-effective for the individual. (See Severin Borenstein's analysis [[url http://www.ucei.berkeley.edu/PDF/csemwp176.pdf]pdf[/url]].) But it certainly makes sense from a climate perspective.
I think the payoff the article was referring to is how long until the total ENERGY cost of PRODUCING THE DEVICES is offset by the energy that is captured, compared to that of other technologies.
Reply | Report Abuse | Link to thisJust curious if we are talking about the same thing - the more common question on people's minds is, if I buy this thing and pay to have it installed, how long will it take until my electric bill savings offset the initial "first costs".
Isn't the article just grappling with the question does this make sense in the whole scheme of things? And I think the answer there is a resounding YES! Read on to where they ultimately use solar powered devices to produce more solar powered devices.
If I am misunderstanding the other posts, please forgive.
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Edited by tsugaguy at 02/21/2008 11:27 AM
What is the effect of the high expense of this technology on wealth creation (or destruction, in this case) particularly in poor countries? Wouldn't pollution be reduced if we simply starved to death?
Reply | Report Abuse | Link to thisMaterial constraints for thin-film solar cells, 1998 (Energy 23:407-411) stated:
Reply | Report Abuse | Link to thisHarnessing solar energy by using photovoltaic cells requires Cd, Ga, Ge, In, Ru, Se or Te as major energy-supply technology: these are subjected to severe resource constraints (1998 !)
One question is: how to get out of peak-oil without entering peak-Te etc.
In fact, many rare elements have been suggested elsewhere to be at or already over peak.
As good ores become depleted, energy input to extract more will go up, so will environmental damage, and not least, many of such elements are toxic if not handled right.
Have you had your telephone cut off for weeks because some fellow made good money walking away with tel. cables? People become very efficient when the price is right.
New Scientist 2007:
... if all 500 million vehicles in use today were re-equipped with fuel cells, operating losses would mean that all the world's sources of platinum would be exhausted within 15 yrs.
So how are the reserves?
The role of photovoltaics is limited, but there is a role for it. One way to produce the panels is with hydro-electricity. PV manufacturing plant production could be maximized (non-stop, 24/7) during heavy rain to minimize water storage, which is the most damaging aspect of hydro-electricity temporally and physically. That way, the panels transfer the hydro power to PV users without witholding the water at least for long, generating electricity long after the water has been released.
Reply | Report Abuse | Link to thisThe biggest problem with PV systems for domestic use is that they are hopelessly uneconomic.
Reply | Report Abuse | Link to thisA PV system that is only theoretically capable of supplying my needs would cost me over $80K in assets over twenty years when compared with putting the capital cost in the bank and paying my electricity bills using interest
There is one possibility that would make PV systems desireable and worth installing and that is to combine PV technology with cars run on compressed air.
Compressed air vehicles would already cover most of my family needs - especially as far as a second vehicle is concerned. Indeed I could probably use developed compressed air vehicles for both cars
PV cells could be used to drive the compressors that recharge the compressed air cylinders. I could therefore drive at NO fuel cost
And then there is always the possibility of driving a dynamo overnight using the same stored free energy
Could this be the way to go for PV technology?
The family cars could be the key.
"If solar energy begins to power its own production...PV breeder cycle...."
Reply | Report Abuse | Link to thisAt the point where panels from a manufacturing site create as much power per year as the plant uses the breeder cycle is established.
There is no need for the panels to be mounted on the factory roof. (In fact, that might be a bad idea if the factory is located in a non-sunny clime.)
If the panels are hooked to the grid and the factory is hooked to the grid, then the factory is producing its power from its panels. It's just trading what would be unusable sunny hour "peak" power to someplace that has excess 'dark hours' power.
The primary problem with the 1-3 year payback times is that they are theoretical numbers assuming perfect siting, perfect maintenance (i.e.cleaning) and an Equatorial location. Including real world siting, and energy losses inplicit in tieing into the "grid" tends to push the payback times into the 10-20 year range for commercial power production. Nor do the payback time calulations include the energy needed to produce the batteries needed to make solar cells usefull after the sun sets. So, as a suppliment solar cells can have a decent payback time. As the primary power source; not so good.
Reply | Report Abuse | Link to thisYou are citing incorrect facts, leading you to this conclusion, Cfostel. I would advise reading the study: " Energy Pay Back Time for PV Systems -- Alsema, De Wild, Fthenakis, 21st European Photovoltaic Energy Conference, Dresden, 2006 " The study does not show 'perfect' siting in an equatorial location as the systems are analyzed for sites in Central and Southern Europe... hardly idyllic, and certainly lower than the average irradiance in the US which is at lower latitudes. The authors of course include grid losses, as well as system losses in conversion efficiency, line mismatch, shading, etc. They also include all input energies, through the composing component mining of input materials, refining, manufacturing, transportation, installation, maintenance and recycling. but remember... energy storage technology is separate and requires another Life Cycle Analysis. Payback times are indeed 1-3 years, and probably near the lower end for an average system in the U.S.
Reply | Report Abuse | Link to this"The biggest problem with PV systems for domestic use is that they are hopelessly uneconomic.
Reply | Report Abuse | Link to thisA PV system that is only theoretically capable of supplying my needs would cost me over $80K in assets over twenty years when compared with putting the capital cost in the bank and paying my electricity bills using interest"
So unless you spend more than $2,000/year (not considering interest), you would be going in the hole?
Of course the article was addressing the basic question: if I went solar, would I ever produce more energy than going solar used up and if so when? They say one to three years. At one point solar cells required twenty years of output to equal the energy required to manufacture. If they didn't last more than twenty years, you would be backing up.
Your question regarding the economics is important but also changing. The cost of energy fluctuates, the cost of manufacturing photovoltaics goes down.
Imagine a $20 gallon can of self assembling photovoltaic paint which could be painted on and would put out power when dry. It doesn't exist for any price right now but I don't know of any reason it couldn't possibly be made, given the right advances.
Please add in and compare the expense of the Iraq and Afghanistan wars, the Gulf oil disaster, the cost of mountaintop removal, fossil fuel extraction from tar sands, and the mounting exponential costs of climate change in the terms of lives lost or ruined, communities shattered, ecological destruction and climate chaos on a global scale to the cost of manufacturing PV and then tell me solar power is uneconomical. At some point in the near future renewable energy system manufacturing will be powered by its own energy and the argument of economics will die completely. One cannot deny the destructive power of fossil fuels and the path their use and exploitation of are taking humanity and all of biodiversity down.
Reply | Report Abuse | Link to thisCash flow positive and no money down solar photovoltaic has come of age in Vermont. Here is one example:
Reply | Report Abuse | Link to thishttp://www.allearthrenewables.com/news/news-releases/solar-at-no-cost-allearth-renewables-announces-zero-cost-residential-and-community-scale-solar-program/
Renewables time has come. Quite unexpectedly (to me) some of solar's greatest supporters are traditionally staunch conservatives. Solar is a solid investment for investors and locks in electric prices for end-users.
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