March 11, 2009
Atmospheric Sulfur Particles Cut Solar Power Output

If we inject large amounts of sulfur particles in the atmosphere to cool the climate then the resulting diffusion of light will cut power output of concentration solar power installations by as much as a fifth. Photovoltaics and solar water heaters will not suffer as much loss of output.

The concept of delaying global warming by adding particles into the upper atmosphere to cool the climate could unintentionally reduce peak electricity generated by large solar power plants by as much as one-fifth, according to a new NOAA study. The findings appear in this week’s issue of Environmental Science and Technology.

“Injecting particles into the stratosphere could have unintended consequences for one alternative energy source expected to play a role in the transition away from fossil fuels,” said author Daniel Murphy, a scientist at NOAA’s Earth System Research Laboratory in Boulder, Colo.

The problem comes from diffused light which does not hit solar concentrators at the right angles.

Murphy found that particles in the stratosphere reduce the amount and change the nature of the sunlight that strikes the Earth. Though a fraction of the incoming sunlight bounces back to space (the cooling effect), a much larger amount becomes diffuse, or scattered, light.

On average, for every watt of sunlight the particles reflect away from the Earth, another three watts of direct sunlight are converted to diffuse sunlight. Large power-generating solar plants that concentrate sunlight for maximum efficiency depend solely on direct sunlight and cannot use diffuse light.

Murphy verified his calculations using long-term NOAA observations of direct and diffuse sunlight before and after the 1991 eruption.

After the eruption of Mt. Pinatubo, peak power output of Solar Electric Generating Stations in California, the largest collective of solar power plants in the world, fell by up to 20 percent, even though the stratospheric particles from the eruption reduced total sunlight that year by less than 3 percent.

Solar panels and solar hot water panels would suffer much less decrease in output. But passive solar house heating would become less effective.

Flat photovoltaic and hot water panels, commonly seen on household roofs, use both diffuse and direct sunlight. Their energy output would decline much less than that from concentrating systems.

Even low-tech measures to balance a home’s energy, such as south-facing windows for winter heat and overhangs for summer shade, would be less effective if direct sunlight is reduced.

Interesting result. Enhanced dimethyl sulfide (DMS) excretion by marine phytoplankton might be a low cost way to use the natural sulfur cycle to cool the planet. The silicon dioxide approach would cool the planet for a very low cost. A massive satellite-based reduction of insolation would avoid the diffuse light problem. But the cost would be much higher. Though one group proposes a satellite approach which they claim would cost only a half trillion dollars. Another and much lower tech way to cool the planet: paint all rooftops white. Throw in the use of lighter colored materials for road construction and we could achieve an even greater increase in albedo.

Another problem with reduced insolation: less rainfall. But a satellite approach might be able to reduce that side effect by selectively reducing sunlight only on deserts and therefore plenty of sunlight would still hit ocean surfaces and cause evaporation.

Share |      Randall Parker, 2009 March 11 11:04 PM  Climate Engineering

K said at March 12, 2009 12:29 PM:

"Atmospheric Sulfur Particles Cut Solar Power Output"

I think that argument is too diffuse to be taken seriously.

But wouldn't diffusion make the skies brighter at night? And seemingly lengthen the day as the eastern and western skies glowed more before sunrise and after sunset?

Off hand, deserts where life is now marginal, the Arctic and Antartic would change the most.

Paul F. Dietz said at March 12, 2009 6:34 PM:

But wouldn't diffusion make the skies brighter at night?

No. They might prolong twilight a bit, but they are not going to make sunlight shine through the solid Earth.

K said at March 12, 2009 10:09 PM:

Paul: Obviously I don't take the article very seriously. And I phrased my question poorly.

Here is what I meant: The diffusion would make each star less bright by scattering incoming light. And at the same time any light - such as citylights - from Earth would also be diffused. So it seemed to me that the night sky would be a little brighter but each star would have less contrast.

In other words there would be an increase of the same effects we already have.

Denan said at July 8, 2011 11:39 AM:

It is safe to assume that if solar arrays are negatively affected by atmospheric sulfur injection, then photosynthesis both on land and in the oceans would be as well. The resultant negative effects on O2 generation and carbon sequestration via photosynthesis should be considered if one believes the process of photosynthesis might be just a bit more important than solar electrical power generation.

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