Student Research Project Idea: Monitoring Solar Radiation

Research Questions:

Perhaps the most obvious use for a pyranometer, an instrument that measures solar radiation, is to determine the suitability of sites for producing electricity from sunlight, or for heating water. But, there are many other scientifically interesting measurements that can be made with pyranometers! How does the available solar energy change as a function of seasons under tree canopies? How does air quality affect the amount of sunlight reaching Earth's surface? How can we use pyranometer data to study cloud patterns?

Brief Background:

Insolation, in units of watts per square meter, W/m², is defined as the total solar energy reaching a horizontal surface at Earth's surface. Insolation is measured with an instrument called a pyranometer. Some research-grade pyranometers, which use what are called thermopile detectors, cost several thousand dollars. Others use silicon-based photodetectors. These less expensive instruments have been used for decades for routine solar monitoring.

A silicon-based pyranometer developed by IESRE contains less than $10 in parts and, when properly calibrated, will produce results comparable to commercial silicon-based pyranometers costing hundreds of dollars. These instruments are so inexpensive that it is practical to use several of them for monitoring differences in solar radiation that can occur even over small areas. There is a lot of information about pyranometers and monitoring solar radiation on IESRE's website, including models that can be used to predict insolation under clear skies. Students have already used these measurements made with these instruments to study the performance of solar photovoltaic and thermal systems. These are interesting engineering-related projects, but they are not particularly interesting for climate science. Some more interesting climate science project possibilities include:

• Monitoring changes in insolation under tree canopies, compared to open areas
• Generating cloud statistics from pyranometer data, comparing instantaneous sampling with time-averaged data. (Time-averaged data contain much less information about the very short-term variability in insolation that can occur as a result of clouds.)
• Investigating microclimate effects in urban areas, such as urban gardens

Some References: