The Meteorology of the Solar Power Revolution

There is a quiet revolution in energy production that will change the lives of many:  the solar energy revolution.

With the cost of photovoltaic solar systems dropping rapidly, there has been a rapid expansion of solar power installations, both commercial and residential, around the U.S., with particularly rapid growth in California.

Consider the geographical distribution of the resource:  where are the best locations in the U.S. for solar power?

By considering both solar angle, cloudiness, and other factors,  NREL (National Renewable Energy Lab) has produced solar energy resource maps for the U.S.   Here is the annual average values (per day in kilowatt hours per square meter).   The southwest U.S. is the Saudi Arabia of solar energy, with the highest values stretching from western Texas to California.    It is really better than Saudi Arabia, since there is huge population hungry for energy  in the Southwest (e.g., Los Angeles, San Diego, Las Vegas, Phoenix, Tucson, etc.)  Lots of sun during the day, exactly when folks need it for air conditioning and their daily lives.

There are, of course, two main factors than produce this geographical distribution.  First, annual solar radiation increases towards the equator.  But more importantly there is the distribution of cloudiness with the desert SW have less clouds (see map)

For us here in the Northwest, there is substantial solar energy potential over eastern Washington and Oregon.  This is particularly true during the summer months when our region enjoys clear skies and LONG summer days.  To illustrate, here is the solar resource for July.  The Columbia Basin is world class, as good as California.

There is a factor that enhances the NW solar energy potential, making up a bit for the fact we are relatively far north:  our temperatures.    It turns out the photovoltaic cells are sensitive to temperature, with efficiency greater at COOLER temperatures.    Thus, high temperatures in the

desert southwest works against solar cell efficiency.  But cooler temperatures makes our solar panels more efficient, partially leveling the playing field for us a bit.

The amount of solar energy being produced today is far greater than many people think, particularly in California, the U.S. state with the most installed solar units.  Here is a plot of the renewable energy output for California yesterday (April 16, 2015).  Solar energy is the dominant source of renewable energy during the daytime hours.

But here is the amazing thing.  The next plot shows total energy production yesterday in CA from all sources.  Renewables (mainly solar) are roughly 25% of the total energy production during the day--and this does not include solar production at individual homes!

But what about here in cloudy Seattle?   It turns out that solar energy from photovoltaics can make sense for local residents, particularly with all the Federal, State, and local subsidies.   One of the faculty members in my department installed a solar system two years ago.  He finds that for the sunny six months of the year be pays nothing for electricity AND produces enough juice to charge his Chevy Volt for all his local driving.  His estimated payback period is 7 years.   Even without subsidies his solar array would make financial sense.  Electric cars are a perfect adjunct to solar energy, allowing excessive power to be stored in the car's batteries for transportation and other uses. Warm climates like the U.S. Southwest are also good since energy demand (for air conditioning) is closely related to solar output.

The U.S. is hardly tapping it potential for solar energy, and with supportive policies U.S. solar generation could easily be 10 times larger than today in ten years, supplying 10-15% of all U.S. electricity demand, and much more in the solar rich regions like the southwest U.S.  These are conservative numbers--I bet we could do much better.

There are several firms, with meteorological modeling and statistical expertise, that supply solar energy forecasts for industry and others.   One of the biggest is here in Seattle:  3-Tier/Vaisala:

In short, solar energy collection is growing rapidly today, but is only a shadow of what it could be, particularly since prices are dropping rapidly and the technology is progressively improving.