| ACTIVITY SUMMARY: This
activity begins with an experiment in which students use a liter of water (colored with
black dye or ink) to document the ability of the Sun to heat the water. The experiment can
stand alone as a demonstration of the capacity of the Sun to provide useful energy. We
encourage you have the class also complete the second part of the activity, in which
students use their data in a provided formula (along with other provided information, such
as the specific thermal capacity of water) to calculate an estimate of the density of the
incoming solar radiation - the power of the sun.
TEACHER TIPS:
- Please see the note under Solar Cell Simulation in the
Physical Science / Science and Technology section of the curriculum matrix.
- This activity is not so much about using the sun as an energy source
to heat water as it is about estimating the power of the sun. For an activity more focused
on how to effectively heat water with the sun, see Solar Water Heaters.
- This activity provides an interesting framework in which to
introduce, discuss, and/or review concepts and measurements related to area, volume,
energy, temperature, specific heat, and power.
- Joules are units of work. This is in contrast to watts, which are
units of power, or work over time. One joule of work done in one second equals one watt.
- The average insulation (power density, or intensity of solar energy
available) of the sun is about 1000 watts/sq. meter. The values from this experiment
should be lower because you will not be able to capture all of the sun's energy. Some of
it will be lost as heat. To minimize these losses, the experiment suggests starting with
water 2 degrees Celsius below ambient temperature, and allowing the temperature to raise 2
degrees above ambient temperature. Thus, the work done will be constant-16,800 Joules, or
4 degrees X 1 Kg X 4,200 J/Kg*K. The amount of time it takes to accomplish this work is
what determines the watts, and the space it takes determines the square meters. This final
value, watts per square meter, is a measure of how much energy we get from the sun.
- The Arizona Solar Center website has a colorful map showing solar
insolation across the U.S.; it could be useful in a discussion of why solar technologies
are so appropriate for use in Arizona. http://www.azsolarcenter.com/arizona/solmap.html
- You may link to the specific activity pages by clicking below, or if
you wish you can download the entire curriculum from the website source noted.
- If you would like to have your students pursue other energy-math
calculations, try Energy Transformations from the website of the Alliance to Save Energy.
In this activity, students conduct a simple experiment heating water and then calculate
the Btu's, kilocalories, therms, and kilowatt-hours for the measured temperature change. http://www.ase.org/educators/lessons/e-trans.htm
- Measuring the Sun's Power relates to Units 6 and 7 in SciencePlus:
Technology and Society - Level Green, and to Unit 6 in Level Blue.
Arizona Department of Education Science Standards: 1SC-E1, E3;
5SC-E3, E4.
Source: Solar Exchange Unit, Ages 12-16. Global Solar
Partners / Energy for the 21st Century (Trial Version). Science Around the
World, Association for Science Education, and BP Amoco. Hatfield, Hertfordshire, UK. http://www.solarpartners.org/
View the student notes
View teachers' notes |
