I always wonder about photovoltaic (PV) cells. How much generating capacity degradation occurs over time due to dirt and grime accumulating on the cells’ surfaces? How important is it to keep them clean, and how clean? If you install them on a sloped roof, cleaning is hard and dangerous (and potentially expensive) enough; even worse to 2, 3 or 4-story roofs.

When you talk about parking lots and roadways, the problem becomes orders of magnitude greater: Tire detritus, oil and grease drippings from vehicles, dust and dirt washed out of the skies and the adjoining soils.

I’ve never understood how or if these things are calculated into life-cost, investment payback and/or energy efficiency.

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Go to article: Designers Building Roadways That Generate Solar Power, By Zoë Schlanger / November 17, 2014 1:47 PM EST

• the designers note
• video about Solar Roadways
• project’s website
• A Deutsche Bank report in October concluded that by 2016, solar power will cost the same or less than electricity from the conventional power grid in almost every U.S. state
• In 1972, the price of an average watt of solar power stood at $75. In 2012, that dropped to less than $1 per watt. By 2015, solar modules from China are expected to run the consumer just 42 cents per watt.