EME 810
Solar Resource Assessment and Economics

2.0 Overview



This is the first of three fairly intense lessons covering the fundamentals of solar energy. You will need to distill a lot of information and work hard to internalize the key topics. Make sure that you use the discussion forums to communicate with your peers, and be sure to ask questions. Most of us have learned bits and pieces of the following materials, but never together in one setting. And for some of us, this is the very first time we are learning to juggle all the balls that tie together solar energy. You can do it!

Time and Space are related! This lesson will discuss the tools needed to evaluate spatial and temporal relationships:

  • of the Sun relative to the Earth;
  • of the Observer on the surface of Earth relative to the Sun at any given time;
  • while identifying the angles used to describe the orientation of a Solar Energy Conversion System (SECS) surface relative to the moving Sun;
  • also identifying the times that local shadows might obscure our SECS. We will use sun charts to analyze shadows with respect to solar collectors.

Just like with navigation in a ship or an airplane, time and space relations are linked together in Solar Energy and can be represented and communicated as geographic information. We input that geographic information in terms of angles and use key relations from spherical trigonometry to make time and space relations easy to calculate with a computer. For our purposes:

angles = coordinates in space and time.

The tools we develop are going to explain the sun’s position relative to any point on the surface of the Earth. Once developed, our useful equations can also be applied to estimate the time and location of shadows that block SECSs or tracking technologies for SECSs.

Math warning!

You will observe substantial mathematical relations in this lesson, and you will be expected to demonstrate your skill at applying them to solar problems in shading assessment. These equations are at the core of software like SAM, and a student completing this course should be very familiar with their application. Stick with it!

Celestial sphere. Described in caption below.
Figure 2.1: Celestial Sphere - This blue sphere is a simple representation of the Earth within a larger sphere representing the celestial sphere, an imaginary sphere projected out onto the sky around the Earth. The equator is shown as a ring on the celestial sphere, tilted 23.45 degrees away from the Ecliptic ring, which is parallel with the orbit relative to the Sun.
Credit: J. Brownson © Penn State University is licensed under CC BY-NC-SA 4.0