Category Archives: Modeling

Basic Principles of Sunlight

I’d put my money on the Sun and solar energy, what a source of power!  We shouldn’t wait until oil and coal run out before we tackle that.
– Thomas Edison in conversation with Henry Ford and Harvey Firestone, 1931

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Atmospheric Air Mass Models

Introduction

The air mass coefficient defines the path length of sunlight through the atmosphere (e.g. the column depth), and is a key input for estimating solar extinction and the irradiance intensity on the Earth’s surface.  The challenge in modeling air mass and solar extinction is an atmosphere that is highly variable, exhibiting unique behavior at different altitudes.  Atmospheric models seek to overcome some of the errors in the interpolative models of air mass.  Specifically, atmospheric models:

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Basic Air Mass Models

Zenith, Azimuth and Elevation Angles

The position of the Sun relative to a point on the ground is an important input needed to model solar air mass and solar system performance.  The inputs used to describe solar position include:

  • Zenith angle \normalsize\theta_{Z}
  • Azimuth angle \normalsize A relative to the North point on a compass
  • Elevation angle or altitude \normalsize h, where \normalsize h = 90 - \theta_{Z}
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Predicting Technology Progress and Solar Growth

Technology progress is a key to solar growth and pricing.  By extension, the ability to model technology progress is essential to understanding future energy supply and demand.

Solar innovation is widespread. Examples include  solar cell efficiency, module manufacturing, and learning innovations with solar system installation and operation. Solar pricing and growth are also supported by innovations in enabling technology, such as battery storage, smart grids and electric vehicles.

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Aerosol Animation

Aerosol Optical Depth (AOD) defines the degree to which aerosols prevent the transmission of sunlight by absorption or scattering.  AOD is measured using an integrated extinction coefficient over a vertical column of air.  The extinction coefficient can be used to analyze solar extinction and the performance of solar power systems as a function of location and time.

GOCART

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Standard Atmosphere in R

Air Mass Coefficient

Click to enlarge

Click to enlarge

The air mass coefficient defines the path length (or column depth) of sunlight through the atmosphere.  The air mass for dry air, wet air and dust are key inputs for estimating solar extinction and the irradiance intensity on the Earth’s surface.  The air mass coefficient is a ratio between the path length for a specific zenith angle \theta_{Z} and the column depth when the zenith angle equals zero.

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