Abstract

Objective

In this science fair project, you will build what are called batch solar collectors, using different colors of plastic bags, to see which color heats water the best.

Introduction

Have you ever been camping out in the wilderness, where there aren't even any bathrooms? Well, after a few days of that, a nice hot bath or shower sure would feel good! But warming water takes energy. When you're camping, that might mean using energy from a cooking stove or a campfire to heat up the water. But just think of all the firewood you'd have to gather! And when you're at home, it probably means a natural gas or an electric-powered water heater heats your water. What if you could warm up water without burning wood, or another fuel, or even without using electricity? Turns out, you can, with something called a batch solar collector. Solar means anything relating to the Sun. Using the Sun to heat water is called solar heating. So can you guess what a batch solar collector does? It's is a piece of equipment that "collects" energy from the Sun to heat water. A batch solar collector is a storage tank that sits inside an insulated box (which means that it holds in heat or cold) that faces the Sun. Water flows into the tank and is heated by the Sun. When you need hot water, simply empty the storage tank. As the tank is emptied, more cold water flows in and continues to be heated by the Sun. Batch solar collectors work best during the summer months, because the Sun is out longer during the day and it doesn't get too cold.

The Sun's energy is both free and renewable, meaning it can be used over and over again and it never runs out. Think of it like a movie your parents have rented for you to watch, or a book you've borrowed from the library. When it's time to take it back, sometimes you can renew it, meaning you can keep using it (but unlike the Sun's energy, you can't keep using it forever!). Other water-heating methods, like the ones mentioned before (electricity or natural gas), often use non-renewable energy sources, like coal. However, non-renewable energy sources cost money, and someday they'll run out, because there is a limited amount of them on Earth. Some of them also cause air pollution, and that isn't good for our health or our environment.

In this energy science fair project, you will test different batch solar collectors. You will make batch solar collectors using different-colored plastic bags and Styrofoam^TM. Do batch solar collectors really work? Does the color of the bag affect how hot the water gets? Do this quick science fair project and find out!

Figure 1. The Sun. (NASA, 1999.)

Terms, Concepts, and Questions to Start Background Research

• Batch solar collector
• Insulation
• Renewable
• Non-renewable
• Pollution

Questions

• From where does coal come?
• What does the word solar mean?
• What does solar energy mean?

Bibliography

• Solar Energy International. (n.d.). Kid's Info: Answers to Questions Frequently Asked by Kids. Retrieved May 7, 2009, from http://www.solarenergy.org/answers-younger-kids
• United States Department of Energy. (2009, March 24). Solar Water Heaters. Retrieved June 25, 2009, from http://www.energysavers.gov/your_home/water_heating/index.cfm/mytopic=12850
• EnergyBible.com. (2008). Solar Hot Water Systems. Retrieved June 25, 2009, from http://www.energybible.com/solar_energy/solar_hot_water.html

For help creating graphs, try this website:

• National Center for Education Statistics. (n.d.). Create a Graph. Retrieved May 7, 2009, from http://nces.ed.gov/nceskids/CreateAGraph/default.aspx

Materials and Equipment

• Styrofoam insulation panel, 2 feet wide X 4 feet long X 1 inch thick (1); available at your local hardware store
• Aluminum foil (1 roll)
• Scotch® tape
• Plastic bags (9)
  1. The plastic bags should be 3 different colors and you should have 3 bags of each color.
  2. You should use black trash bags, white trash bags and, one other color of trash bags, such as green. You can get different-colored bags from department, book, and clothing stores.
  3. The bags should be large enough to hold 2 liters (L) of water.
• Scissors
• Thermometers (3); available online from science stores like Edmund Scientific at www.scientificsonline.com, part # 3113300
• Plastic soda bottle, 2-L, clean (1)
• Kitchen string, cotton
• Stopwatch
• Graph paper
• Lab notebook

Shop for Supplies at Science Buddies Online Store

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Experimental Procedure

Note: Make sure you pick a sunny day on which to try this science fair project.

1. Take the Styrofoam panel and cover one of the large sides with aluminum foil. Tape the aluminum foil to the Styrofoam with Scotch tape so that the foil is securely attached to it.
2. Take three plastic bags, one of each color that you are using, and clip a small hole at the bottom of the bag with your scissors. The hole should be just big enough so that a thermometer can fit through it.
3. Carefully fit a thermometer through the holes in each of the bags. Push the thermometer through, about halfway up the thermometer. Use Scotch tape to tape the bag securely around the thermometer. It should be tight enough that water will not leak out of the hole. See Figure 2.

Figure 2. This image shows an example of a black bag batch solar collector sitting on top of a foil-covered Styrofoam panel.

4. Now fill the plastic bottle with 2 L of water. Empty the bottle into one of the bags. Carefully squeeze the air out of the bag and tie it closed. Have an adult help you with this step. Trim off the extra plastic from the top, using the scissors.
5. Repeat step 4 with one each of the other colored plastic bags. You should now have three different-colored batch solar collectors.
6. Place the foil-covered panel in full sunlight. Place the three colored batch solar collectors on top of the foil-covered panel, next to each other. The collectors should all be in the Sun, and none of them in shade. Check the temperature of the water in each bag. Read each of the thermometers and record the readings in your lab notebook in a data table, like the one shown below. These readings are the starting temperatures of the water in the batch solar collectors.

7. Let the three collectors sit in the sunlight for 15 minutes. Use the stopwatch to time 15 minutes. After 15 minutes, look at the thermometers and record the water temperature for each batch solar collector in your lab notebook.
8. Let the batch solar collectors sit in the sunlight for another 15 minutes, for a total of 30 minutes, and then record the readings from the thermometers in your lab notebook.
9. Repeat steps 2–8 two more times, with the other plastic bags, to make sure that your results are repeatable and accurate. Always record all of your observations in your lab notebook.
10. Make a plot of your data, using graph paper, or a website like Create a Graph. Make a bar graph. Label the x-axis Color and the y-axis Temperature. For each color, make a bar for the starting temperature, the temperature after 15 minutes, and the temperature after 30 minutes. Does the temperature of the water depend on the color of the bag? Which bag got the water hotter than the others? Which bag kept the water cooler?

Variations

• Put out your solar batch collectors at different times during the day. Does the time of day affect the temperature of the water in the solar batch collectors?
• Try making batch solar collectors from bags of many different colors. For example, try a yellow bag or a pink bag and compare the temperatures with the temperature of the white bag.
• Calculate the rate at which the water heats up, with degrees per minute. Graph this data versus color.

• For more science project ideas in this area of science, see Energy & Power Project Ideas.

Credits

Michelle Maranowski, PhD, Science Buddies

• Styrofoam^TM is a registered trademark of The Dow Chemical Company.
• Scotch® is a registered trademark of 3M.

This project is based on an activity found at the following website:

• National Renewable Energy Laboratories Education Programs. (n.d.). R.E.A.C.T. Renewable Energy Activities—Choices for Tomorrow. Retrieved April 22, 2009, from http://www.nrel.gov/docs/gen/fy01/30927.pdf

Last edit date: 2011-10-26 12:20:00