Thanks to solar panels, the sun’s power is harnessed for clean energy production through photovoltaic technology. The sun also has incredible thermal power. Solar heat, or solar thermal energy, is a form of energy that uses the sun’s power to heat items. Heat results when light energy from the sun strikes atoms. As the atoms become activated by the heat, thermal energy is produced. Let’s break this down a bit further.
All objects in our universe are made up of matter and energy. If we look at matter with a magnified lens, we will see that all matter is made up of tiny molecules (groups of atoms). In cold items, the molecules move very slowly and have a limited amount of energy. When you begin to heat an item, the molecules speed up; the faster they move, the hotter the object becomes. The sun’s light can actually cause this molecular reaction, and create environmentally-friendly thermal energy.
In this experiment, we are going to passively collect the sun’s thermal energy and heat up matter. So, let’s get this experiment started and get those molecules moving!
|6 empty soda pop cans|
|Paint (6 different colors)|
|1 Paint brush|
|Outside thermometer or an app/website that provides local weather|
|Cooking thermometer |
Here is an example of what you will need- Click for link
|1 Measuring cup|
|Data collection notebook (any notebook will work or a sheet of paper)|
You can use the below table so to easily organize the data and see the temperatures throughout the day.
Base Temperature of water at 10:00 a.m:__________
Base Temperature of water at 10:00 a.m.: 71.9 Fahrenheit
Take Away 1: The first thing to note in this experiment is the correlation between the outside temperature and the water inside the cans. At the hottest point of the day, the water in the pop cans will likely have also reached their highest temperature. In this example, the temperature peaked around 3:00 pm (for both the outside temperature and the water temperature, and slowly decreased as the sun moved to a lower location in the sky. This happened because at the hottest part of the day, the cans were able to capture the most solar thermal energy!
More, or longer, exposure to sunlight and hotter temperatures equals a higher water temperature.
Take Away 2: It is important to state that dark-colored objects absorb all wavelengths of light and therefore convert more of the sun’s energy into heat. The more sunlight an object absorbs, the more heat! Colors like white have the opposite effect and absorb limited light energy, which creates a smaller amount of thermal heat. With this information, it is easy to see why the black and dark purple pop cans absorbed the most thermal energy while the white and green produced the smallest increase in temperature.
The darker the color, the more light/thermal energy absorbed. Light colors have the opposite effect.
To better understand what was accomplished in this experiment, we need to discuss solar water heaters. There are two basic types of solar water heaters – active and passive. In this experiment, we created a passive solar water heating system. The system is “passive” because it did not use any mechanical parts to aid in the heating process or circulation of water. An active system relies on pumps and other working parts to circulate and distribute the heated water. No matter if you create an active or passive heating system, you are utilizing the sun’s light as a means to heat an object.
It’s important to note that thermal heating does not always need water. In this experiment, water was used as a way to better understand how the sun’s light can heat an object. The sun’s renewable energy can be used in many different ways to create solar heat both with and without the use of water.
- Passive solar heating examples: heating a greenhouse with the sun’s rays to produce a food source, south facing windows in a home to collect heat, building materials that absorb heat to cut down on energy costs, a sunroom in a home to take advantage of the sun’s heat, thick stone floors and insulated walls to keep energy in a building
- Active solar heating examples: solar collectors positioned on a roof to heat water which then pumps the water through an entire building to use as a heat source, a solar thermal heating system for a pool, an air solar system that uses fans, controls, and ductwork to heat air in a home
Variations to Experiments
- Try using a different object as your water collection item (plastic containers, glass jars) and ask the question: Does the container make a difference when dealing with the results?
- Try painting the cans different colors and evaluate the impact.
- What is the difference between passive and active heating systems?
- What is the impact of materials and colors on capturing thermal power?
- What are examples of passive and active solar heating found around your home/neighborhood?