The Damage Done, Part 8 — Does Solar Power Have Its Environmental Dark Side?

Solar power is often held up as the epitome of clean, renewable energy production. What could be more “green” than spreading millions of solar panels before the sun like flower petals and generating clean electricity for the world?


The European Photovoltaic Industry Association (EPIA) says that

There is more than enough solar radiation available around to satisfy the world’s energy demand. The energy in the Sun’s rays that reach the Earth’s surface could meet global energy consumption 10,000 times over. On average, each square metre of land is exposed to enough sunlight to generate 1,700 kWh of energy every year using currently available technology… if only 4% of the world’s very dry desert areas were used for PV installations, this would meet the whole world’s total primary energy demand.

The SunRight now, solar power provides only a very small percentage of world electricity generation. Solar represents only .35 percent of world renewable generation, or 13 billion kilowatt hours (kWh), according to U.S. Energy Information Agency (EIA) figures. That could change, though.  (Photo: The Sun. Credit: SOHO, ESA and NASA.)

In its “Renewables 2011 Global Status Report,” the clean-energy group Renewable Energy Policy Network for the 21st Century (REN21) says that solar photovoltaic (PV) power is “the world’s fastest growing power generation technology.” World solar PV generation capacity reached 40 gigawatts (GW) in 2010, growing more than sevenfold from 2005 to 2010. Germany alone accounts for 44 percent of installed solar capacity, Spain 10 percent, and Japan and Italy 9 percent each. The U.S. accounts for 6 percent of total.

As you can see in this chart based on Energy Information Agency (EIA) data, solar power represents a growing but relatively small portion of projected U.S. electrical generation from renewables between now and 2035, especially compared to hydro and wind.

Chart showing electrical generation from renewables 2008-2035

Environmental Impacts of Photovoltaic Power

In its report, “Hidden Costs of Energy: Unpriced Consequences of Energy Production and Use,” the U.S. National Academy of Sciences (NAS) says that PV installations consist of two primary parts, the solar panels and the balance of system (BOS) components, which are used to convert direct-current (DC) electricity into alternating current (AC). These components naturally require mining and manufacturing processes, and the facilities have to be built and installed, all of which activities have environmental impacts.

The NAS report says that

Solar panels are made of semi-conducting materials similar to those used in the electronics industry. “Solar grade” silicon, derived from quartz sand, is the most commonly used material to make solar panels. However, emerging thin-film technology, which allow use of solar panels as roof tiles and other building features, can be made of a variety of materials, including amorphous silicon, gallium arsenide (GaAs), cadmium-telluride (CdTe), and copper indium gallium selinide (CIGS)…

Manufacturing these panels is a very high-technology, material- and energy-intensive process. A number of the metals for thin-film PV technology are toxic (for example, arsenic and cadmium), thus raise environmental and public health concerns about metal emissions during the extraction, material upgrading, and manufacturing activities associated with PV systems.

The report also points out potential issues with end-of-life disposal for solar systems:

Worn-out solar panels have potential to create large amounts of waste, a concern exacerbated by the potential for toxic chemicals in solar panels to leach into soil and water. Many components of solar panels can be recycled, but the United States currently does not have or require a solar PV recycling system.

NAS cites the following environmental impacts of solar PV based on previous studies:

Impact Value
Life cycle health impacts (primarily from greenhouse gases, lead, and particulate matter emissions) $.001 – $.002 per kWh
Life cycle GHG emissions 20-60 g per kWh
Nitrous oxide (NOx) 40-180 mg per kWh
Sulfur dioxide (SO2) 50-450 mg per kWh

Solar farmIn an article in Renewable Energy, (“Dynamic life cycle assessment (LCA) of renewable energy technologies,” Renewable Energy, 2006), Martin Pehnt of the Institute for Energy and Environmental Research in Germany, set out life cycle assessments for the primary renewables, including solar PV. LCA, according to Pehnt, involves investigating the “environmental impacts of … systems or products from cradle to grave throughout the full life cycle, from the exploration and supply of materials and fuels, to the production and operation of the investigated objects, to their disposal/recycling.” (See my article about hydropower for more on LCA.) (Photo: Solar farm. Credit: Michael Mees, CC BY 2.0.)

This chart puts together some of Pehnt’s estimates for the LCA environmental effects of renewable sources, comparing them to those for a conventional energy mix of coal, gas, nuclear, etc.:

Environmental Impact Conventional Energy Mix impact
/kWh
Hydro impact
/kWh (large facility)
Wind (on-shore) impact
/kWh
PV Solar impact
/kWh
Geothermal impact
/kWh
Non-Renewable Energy Demand in megajoules (MJ)

8.91

0.10

0.12

1.50

0.54

Iron Ore in grams (Proxy for non-energy resource consumption)

2.60

1.70

3.30

3.30

3.20

Global Warming (g CO2 equiv.)

566.00

10.00

11.00

104.00

41.00

Acidification (mg SO2 equiv., or sulfur dioxide equivalents)

1,083.00

42.00

61.00

528.00

190.00

Eutrophication (mg PO43- equiv., or phosphate equivalents)

59.90

5.00

4.00

44.00

24.80

You can see from these figures that solar PV has the highest environmental impacts per kWh of all the renewable energy technologies. However, its impacts are below those of the conventional energy mix in nearly all impact categories. The exception is in iron ore consumption, which Penht uses as a proxy for the use of material resources overall.

Solar Power and Greenhouse Gases

Solar manufacturing facilityWhat? Solar power creates GHGs? Say it ain’t so!

Well, I’ll grant you that a solar panel soaking up the rays and generating direct current isn’t emitting CO2. However, we are concerned not just with what happens when an energy technology is generating power, but with its entire life cycle — all of the externalities, if it’s posssible to identify them. (See my previous article explaining externalities: “The Damage Done, Part 1 — Is Green Energy Really Better for the Environment?”) (Photo: Solar wafer manufacturing facility. Credit: Oregon Department of Transportation, CC BY 2.0.)

As we’ve considered in the articles on coal, natural gas, nuclear, hydro, and wind, all electrical generation technologies generate GHGs, if you consider their entire life cycles, including manufacturing, construction, and end-of-life disposal.

In an article for Energy Policy, Benjamin J. Sovacool of the Vermont Law School provides useful data comparing the life cycle carbon footprints of various power generation technologies. (“Valuing the greenhouse gas emissions from nuclear power: A critical survey,” Energy Policy, 2008). Carbon footprint is normally expressed in carbon dioxide equivalents, or gCO2eq. In the case of electricity generation, CO2 equivalents are expressed per kilowatt hour (kWh). The following table taken from Sovacool’s study compares the carbon footprints of a number of technologies, including solar:

Source/Technology Lifecycle CO2 Equivalents (gCO2eq/kWh)
Coal 960 to 1,050
Natural gas 443
Nuclear 66
Solar Photovoltaic (PV) 32
Hydroelectric 10 to 13
Wind 9

I note that the 32 gCO2eq/kWh figure for solar is within the 20-60 g range cited above in the NAS study. It’s lower than the 104 g cited in the Pehnt study, but the two figures don’t differ extremely. Solar’s GHG carbon footprint is higher than the other principal renewables but much lower than the conventional mix of energy sources.

Daniel Weisser of the International Atomic Energy Agency, discussing the life cycle GHG emissions of various electrical generation technologies (“A guide to life-cycle greenhouse gas (GHG) emissions from electric supply technologies,” Daniel Weisser, Energy, September 2007) discusses the emissions from solar power as follows:

Unlike fossil fuel systems, most of the GHG emissions [from solar PV] occur upstream of the life-cycle with the majority of the emissions arising during the production of the module (between 50% and 80%). Other significant GHG releases in the upstream relate to the balance-of-plant (BoP) and the inverter. Operation, end-of-life and associated transport activities do not result in meaningful cumulative GHG emissions.

Of the four systems, mono-crystalline plants, on average, may emit the least GHGs ranging between 43 and 62 gCO2 eq/kWh. The other PV systems may emit between 50 and 73 gCO2 eq/kWh over the whole GHG life-cycle. Variations in the results can be for a range of factors, such as the quantity and grade of silicon, module efficiency and lifetime, as well as irradiation conditions. Differences in installation, such as integrated and non-integrated systems, as well as facade, flat roof and solar roof tiles, or the efficiency of the peripheral equipments, such as the balance-of-system (BOS), also significantly affect lifecycle GHG emissions…

Future improvements in cumulative GHG emissions from PV are likely to arise from improvements in module efficiency, increased lifetime, less silicon mass per module and lower use of electricity for the production process.

Did you miss some of the other installments in the “Damage Done” series about the environmental effects of energy technologies, both “green” and conventional? Get caught up here:

The Damage Done, Part 1 — Is Green Energy Really Better for the Environment?

The Damage Done, Part 2 — How Do You Measure the Environmental Effects of Energy?

The Damage Done, Part 3 — Is Coal Really So Bad for the Environment?

The Damage Done, Part 4 — Natural Gas, Green or Dirty?

The Damage Done, Part 5 — Nuclear Power, the Green That Glows?

The Damage Done, Part 6 — How Green Is Hydro Power?

The Damage Done, Part 7 — Wind Power — Really Green, or Is It Just Spin?

The Sun coming from behind the clouds

(Photo: The Sun. Credit: Luis Argerich, CC BY 2.0.)

 

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