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Considering everything that goes into producing a single PV solar panel; from obtaining the necessary materials, transportation etc. is there a net benefit to the environment over the lifetime of the panel?

A net benefit would be one in which less hazardous material is produced as a result of having created and used the panel over its 25 year warranty period as opposed to using regular grid power*.


To provide something of a typical example for which to make calculations from the Australian Energy Matters site it provides the following figures:

System specifications Grid connect solar inverter, 6 x 175W solar panels

Warranty on Solar Panels 25 years

System annual output

1.566 MWh per year
39.15 MWh over warranty period
62.64 MWh over solar panel expected lifetime

Greenhouse gas emission reduction

2035.8 kg per year
50895 kg over warranty period
81432 kg over solar panel expected lifetime

Expected annual energy consumption after install 4274 kWh per year

Energy consumption reduction 26.82%

For the purpose of this exercise, consider the panel to be a Sharp 175Watt 24Volt which has been used in many installations in Australia and what I have on my roof:

  • High Power module 175W using 125mm square single-crystal silicon solar cells with 13.5% module conversion efficiency
  • Photovoltaic module with bypass diode minimises power drop caused by shade.
  • Anti Refection Coating and BSF (Back Surface Field) structure to improve cell conversion efficiency: 16.4%
  • White tempered glass, EVA resin and a weatherproof film along with an aluminum frame for extended outdoor use
  • 24VDC system and high-voltage output for grid-connected system
  • Multi-contact style output leads with waterproof connectors.

Australia's electricity is currently a mix of (approx.):

65% coal
15% hydro
15% natural gas
5% other

*Note regarding grid power. Some energy providers in Australia now provide a green option for electricity where they can source up to 25% of their electricity from renewable sources for as little as $1 extra per quarter.

  • 1
    Not the down-voter, but could you provide some more data on what you consider "solar panel"? It's not wrong to assume that different manufacturers will use different raw material sources which have different production and transportation channels. That would make a considerable impact on any potential answers. Same thing for "lifetime". – AndrejaKo Jul 7 '11 at 17:45
  • as manufacturing processes improves, the answer to this will likely change. – Lie Ryan Jul 7 '11 at 17:48
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    There is an underlying assumption in your question that should be addresed. The energy balance does not need to be positive at all! Suppose I build a solar panel factory which is energy neutral (using whichever technology, as long as it's renewable/non-fossil based)... Who cares about the energy balance at that point? – Sklivvz Jul 7 '11 at 17:53
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    Is this question about photovoltaic or photothermal solar panels? Their manufacturing costs and efficiency are very different. – Suma Jul 7 '11 at 20:02
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    As with many/most environmental footprint issues, I think it's impossible to answer this question conclusively, because you're often comparing apples and oranges. Coal-generated electricity emits carbon into the atmosphere, whereas manufacturing a PV cell may result in some liquids being emitted into a river. It's impossible to provide an apples-to-apples comparison of these two entirely different types of environmental impacts to say which is "worse". One is worse for birds, the other for fish--but how do you measure which is "overall worse?" – Flimzy Jul 19 '11 at 8:33
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Yes, there is a net environmental benefit from photovoltaic panels.

It would be possible to contrive a corner case where there was not a net benefit (for example, having a PV system illuminated only by a light bulb, rather than by the sun); but such cases are extremely rare.

Let's break down the big, somewhat cloudy question of "net environmental benefit" into some component questions that are commonly raised. Does PV have net energy production? How much greenhouse gases from fossil-fuel production does it displace, when the full product lifecycle is accounted for? How do aggregate damage costs compare? I'll deal with each of those in turn.

Net energy production

Fthenakis and Alsema (1) looked at the net energy production of photovoltaics, based on 2004 technology (things have improved a lot since then). They found energy payback times of between 1.0 and 2.2 years, depending on the specific panel technology, and where it was manufactured. So all energy generated after that time is net energy production. Systems typically last 15-30 years.

The 2009 review of life cycle assessments by Sherwani, Usmani and Varun (3) found energy payback times of 1.5-5.7 years, for systems with lifetimes of 20-30 years.

In 2012, Fthenakis (4) looked at historic trends of energy payback times [EPBT], and found that they'd been improving for 40 years (NB the vertical axis has a log scale):

Energy payback time of PV has dropped from around 40 years to 0.5 years

That gives values for energy returned on energy invested (EROEI) in the range 10-40.

So PV has a high net energy production

Greenhouse gases displaced

First, let's note that the power into a grid and the power consumed must match at all times. So if PV generation increases, some other source of power must decrease, in order to keep the system balanced. So some other generator will get turned down. The type of generation being displaced does make a difference. In most of the world, in 2012, it will usually be a fossil-fuel plant - coal or gas (see the World Energy Outlook, IEA).

Fthenakis and Alsema (1) cite the ExternE and Australian Coal Association research on full-lifecycle greenhouse-gas emissions, and found that monocrystalline silicon PV came out at 100-180gCO2e/kWh, whereas coal was 900g, and gas CCGT was 400-439g. Their own calculations for different PV technologies gave even lower results: 37g for polycrystalline silicon; 21g for EU Cadmium Telluride; 25g for US Cadmium Telluride.

Similarly, Sherwani et al (3) found full-lifecyle greenhouse gas emissions from PV were in the range 9.4-104gCO2e/kWh

On a full-lifecycle analysis, there are substantial greenhouse-gas savings with PV.

Total Damage costs

Flimzy poster, in comments on the question, notes that:

you're often comparing apples and oranges. Coal-generated electricity emits carbon into the atmosphere, whereas manufacturing a PV cell may result in some liquids being emitted into a river ... how do you measure which is "overall worse?"

That's true. And there is a standard method for aggregating externalities, which is to monetise each aspect of damage, and then sum those costs.

Fthenakis and Alsema (1) found that the unit damage cost for PV systems was 0.126-0.177 eurocent per Kwh, using a remarkably low value of CO2 damage (€19/tCO2e). Even at that level, the CO2-damage alone from fossil plant exceeds the total damage costs from PV (€19/tCO2e x 400gCO2e/kWh = 0.76 eurocent per kWh).

Total environmental damage costs from PV, are less than those of the fossil-fuel generation that they displace.

Metal specifics

For anyone interested in the detail of metal extraction for PV, Ftheankis, Wang and Kim looked at the specifics for zinc, copper, aluminum, cadmium, indium, germanium, gallium, selenium, tellurium, and molybdenum (2).

Sources

(1) Fthenakis VM, Alsema E. Photovoltaics energy payback times, greenhouse gas emissions and external costs: 2004-early 2005 status. Progress in Photovoltaics: Research and Applications. 2006;14(3):275–280. DOI:10.1002/pip.706

(2) Fthenakis VM, Wang W, Kim H. Life cycle inventory analysis of the production of metals used in photovoltaics. Renewable and Sustainable Energy Reviews. 2009;13(3):493–517. DOI:10.1016/j.rser.2007.11.012

(3) Sherwani AF, Usmani JA, Varun. Life cycle assessment of solar PV based electricity generation systems: A review. Renewable and Sustainable Energy Reviews. 2010;14(1):540–544. DOI:10.1016/j.rser.2009.08.003

(4) Fthenakis V. How long does it take for photovoltaics to produce the energy used?, in PE Magazine, from the National Society of Professional Engineers, Jan/Feb 2012. PDF available here.

  • On what basis do you say that (€19/tCO2e) is "remarkably low"? How was this number determined? – Muhd Oct 16 '12 at 0:35
  • @Muhd the $19 is from the 2003 Externe-Pol study. For more recent figures, see papers by Dr Chris Hope. There are several Area51 proposals where such questions could be answered - please do support one or more of: Sustainable Living, Climate Change, and Economics – EnergyNumbers Oct 16 '12 at 7:12
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    I just came across an article (lowtechmagazine.com/2008/03/the-ugly-side-o.html) that claims that, on the question of greenhouse emissions, solar panels may in fact not offer a net improvement over other energy sources. Interestingly, the study they reference (pubs.acs.org/doi/full/10.1021/es071763q) reaches the opposite conclusion. However, the analysis in the article, which suggests that the study authors reached an unrealistically optimistic conclusion, seems cogent. Do you, EnergyNumbers, have any response to this article? – devuxer Mar 27 '13 at 18:38
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    @DanM None of its calculations or references support its conclusions. It's a poorly-assembled attempted hatchet job, in keeping with the rest of that blog. So, I guess my response is: oh look, there's an ignorant ill-informed badly-reasoned blog. – EnergyNumbers Mar 28 '13 at 8:26
  • @EnergyNumbers, thanks for the response. Maybe the blog title wasn't being ironic after all :) – devuxer Mar 28 '13 at 20:09

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