Using the sun to heat water is not a new idea. Humans have been harnessing the thermal energy of the sun for centuries. Today, solar thermal systems are found on roof-tops around the world, providing affordable, pollution-free hot water for millions of people.
The KidWind Solar Thermal Exploration Kit that you will use in this experiment is a model of an “active” or “forced circulation” system. This type of solar water heater requires a pump to move water from the storage tank to the collector. Most solar water heaters in the United States are forced circulation systems because this type of system works well even when temperatures drop below freezing. Passive systems that do not use an electric pump are also common, but are not practical for colder climates where the water may freeze.
The color of the solar absorber affects the ability of the solar collector to take advantage of the greenhouse effect. Every color reflects a certain amount of light while absorbing the rest as heat energy.
In this experiment, you measure the reflectivity of various colors using a Light Sensor, and then compare these values to the reflection value of aluminum foil. Aluminum foil will arbitrarily be assigned a reflectivity of 100 percent. You will calculate percent reflectivity using the relationship
After determining the best color choice for the background of the solar collector, you will set up a solar collector and determine the change in water temperature during data collection.
Use a Light Sensor to measure reflected light.
Use a Surface Temperature Sensor to measure changes in temperature.
Calculate percent reflectivity of various colors.
Use results to design and set up a solar collector.
Determine the temperature change of the water in a solar collector.
Sensors and Equipment
This experiment features the following Vernier sensors and equipment.