The GreenStalk

Iso-IRR pt 3: Sunlight

Posted in Solar by Paul Grana on June 6, 2010

The Iso-IRR curve seems to be a popular way to think about different solar plants.  So I wanted to use it to look at how much sun matters.

Turns out it matters a lot.  As a location’s sunlight goes up, so does a developer’s willingness to pay for it.  That’s not a big surprise.  What I do find surprising is the overall magnitude of the impact.  A developer in Phoenix would be willing to build a solar plant for roughly $1.75 more per watt (with the same return) than an identical system in Chicago – a 57% premium.

This is why people expect the most promising American solar development to take place in the sunny southwest.  And reinforces how impressive Germany’s support of the industry has been (their sunlight resembles Chicago’s).

Final technical notes:

The model behind this is the same LCOE model that I posted a couple weeks ago (I used model #3).  Keep in mind that, as always, the exact numbers are not precise, use this only directionally.

Also, the sun-hour per city data comes from NREL.  For now, I have been using full-tilt sun data (with the module tilt equal to the location’s latitude), but in future posts I’ll look at how this changes with lower tilt.


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