Energy Sciences

Lesson 2: Wind Energy: Building Windmills

For the Warm-Up, students will construct a device that measures wind speed and then measure the wind speed at different times during the day for a week and record their answers. Students will display measurements in a box-and-whiskers plot and determine if wind is a good source of energy in Churchill, Richmond, Va. ³⁸ In order to use the wind as a source of energy, we must have a steady source of wind.

Activity 1: Wind Energy: Building Windmills

In small groups, students will construct a windmill that can do work by picking up a certain amount of weight. Students will then calculate the amount of work and power needed to pick up the weight. Work is the measure of the weight lifted through height; work, W, varies jointly with mass, m, acceleration of gravity, g, and height, h, W=mgh. Power is the measure of energy used over time; power, P, varies directly with energy, E, and inversely with time, t, P = E/t. The two equations are related since energy is the ability to do work, so E=W. Students will then work in groups to complete a virtual lab ³⁹ on wind energy; there will be a competition of who creates the most efficient and economical wind farm.

Activity 2: How much wind power does a fan generate?

Students will calculate the wind power created by a fan set on different speeds: low, medium and high. Wind power, P, varies jointly with half of air density, Ρ, area swept by the turbine blades, A, and the cube of the velocity, V, P = (1/2)ΡV ³. Air density is the mass per unit volume of earth's atmospheric gases and measures 1.25 kg/m ³ at sea level and 68°F.

For homework, students can write, graph and evaluate linear models for the following individual facts: wind integration costs are approximately $10/MWh, the decrease in air density is 3% for every 1000 additional feet in height and 1% for each additional degree in temperature (air density is 1.25 kg/m ³ at sea level and 68 °F), and the Bluestone River Wind Project in Tazewell County, southwest Virginia, could produce nearly 80 MW (1MW of wind energy will provide electricity for approximately 1,000 people).

A possible extension can include looking at a map of wind power potential along the Virginian coast and having students write a system of linear inequalities to describe the area. Students can also use a system of equations to find the intersections of the boundary lines. Students can write energy equations using the language of direct and inverse relationships. They can also make tables and graph direct and inverse relationships. Have students pay attention to independent and dependent values. In some cases, negative numbers do not exist in the domain or range. Finally, students can calculate a curve of best fit for wind energy related data and extrapolate the wattage of future wind power.