How #WindPower Works : When you talk about modern wind #turbines, you're looking at two primary designs: horizontal-axis and vertical-axis. Vertical-axis wind turbines (VAWTs) are pretty rare. The only one currently in commercial production is the Darrieus turbine, which looks kind of like an egg beater.
INFOGRAPHIC: Why solar panels are an affordable and smart investment
This behavior chart is great for students to use a hands on method, as well as individualized choice to decide what he or she would like to work on. Four items is a reasonable number, in which students can make significant improvement without feeling like they are trying to focus on too many things at once.