How Much Incoming Solar Energy (Insolation) Is Received at Different Locations?

For purposes of designing heating/cooling systems and other uses, average insolation data are available for many sources. One is the US Department of Energy’s National Renewable Energy Laboratory (http://www.nrel.gov). 

Their data are available through: http://rredc.nrel.gov/solar/old_data/nsrdb/redbook/sum2/state.html

The first step is to select a location and become familiar with the format in which the data are presented. To begin, you might wish to find a location relatively near you by choosing from the alphabetical list. At the top, you’re given the city, state, identification (WBAN) number, latitude, longitude, elevation (feet), and other information. Of most importance are the items indicated in bold-face above.

Next come three sets of data providing information averaged over a thirty-year period by collectors at different angles. For you puroses, just look at the first set labeled “SOLAR RADIATION FOR FLAT-PLATE COLLECTORS FACING SOUTH AT A FIXED-TILT (kWh/m2/day).” Within these, just use the top three lines showing the “Average,” “Minimum,” and “Maximum” values for each month and the year.

Select four or five of the available locations.  Try to choose sites with approximately the same latitudes or longitudes.  For each, follow the on-line instructions to:

1) obtain name, latitude, and longitude, and average, minimum, and maximum insolation for each month and for the year.

[Necessary information:

The amount of “incoming solar energy” (“insolation”) can be measured with a “radiometer.”

Average monthly and annual values are reported in units of “kilowatt hours/square meter/day” (kWh/m^2/day).]

2) Present the data in a table or spreadsheet. 

3) Select appropriate portions of the table and make graphs showing patterns in insolation. (Examples:  You can use line graphs to show variations in average monthly solar energy values at different locations, or you could use a bar graph to compare average annual values.)

4) Provide brief interpretations of what you have learned.  You should be able to write at least one or two paragraphs about each part of this project.

[Extension/extra credit:  The web site also provides climate data.  Design an investigation comparing solar radiation and climate conditions.]

1. What factors may affect the amount of solar energy received at a location?

2. What would be three things to consider in deciding where to locate a radiometer site?

    (Consider what should be done to avoid obtaining misleading data.)

3.  If skies over a location become more polluted from natural (ex., volcanic eruptions) or human (ex., vehicle or factory exhaust) sources, what changes might occur in the amount of solar energy reaching the surface?

Example of Data Presentation and Analysis

The station data presented below provides an example of what can be done using the data available on the web site.   The data have been entered into an Excel spreadsheet.  Then the Excel graphing capabilities have been used.

City: BOSTON * State: MA  (WBAN No: 14739)     

Lat(N): 42.37 Long(W): 71.03 * Elev(m): 5 * Pres(mb): 1015 *

Solar Radiation, kWh/m^2/day             

Selected Applicable Key Ideas and Performance Indicators from the NYSED “MST Learning Standards,” especially Physical Setting/Earth Science Core Curriculum

Standard 1--Analysis, Inquiry, and Design

Mathematical Analysis:

--Abstraction and symbolic representation are used to reach mathematical conclusions.

--Deductive and inductive reasoning are used to reach mathematical conclusions.

--Critical thinking skills are used in the solution of mathematical problems.

Scientific Inquiry:

--The central purpose of scientific inquiry is to develop explanations of natural phenomena in a continuing, creative process.

--Scientific inquiry involves testing of proposed explanations involving the use of conventional techniques and procedures and usually requiring considerable ingenuity.

--Observations made while testing proposed explanations, when analyzed using conventional and invented methods, provide new insights into phenomena.

Standard 2--Information Systems

--Information technology is used to retrieve, process, and communicate information as a tool to enhance learning.

Standard 4--Science

--The Earth and celestial phenomena can be described by principles of relative motion and  perspectives.

Objects in the solar system are in regular and predictable motion.

Earth’s motion and its changing position with regard to the Sun and move have noticeable effects.

--Many of the phenomena that we observe on Earth involve interactions among components of air, water, and land.

Earth systems have internal and external sources of energy.

Weather patterns become evident when weather variables are measured.

Weather variables are measured with instruments.

Weather variables can be represented in a variety of formats.

Seasonal changes can be explained using concepts of heat energy.

Standard 6--Interconnectedness

--Through system thinking people can recognize commonalities that exist among all systems and how parts of a system correlate and combine.

--Models are simplified representations used in analysis, explanation, interpretation, or design.

--Grouping into a series provides a useful way to deal with the immense range and changes that  affect systems.

--Identifying patterns of change is necessary for making predictions about future behavior and conditions.

Standard 7--Interdisciplinary Problem Solving

--Knowledge and skills of mathematics, science, and technology are used together to make informed decisions and solve problems.

--Solving problems involves a variety of skills and strategies, including effective work habits, gathering and processing information, generating and analyzing ideas, making connections, and presenting results.