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					Earth Science: Solar Energy
Ms. Sommers

8/12/2008

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Investigation 3: Solar Water Heaters
 They catch energy from

the sun and heat the surrounding water (energy transfer)  Romans constructed raised aqueducts lined with black slate and pioneers stored water in black pots on sunny days. Modern rooftop water heaters are a clean, safe alternative to gas/electric
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Investigation 3 Solar Water Heaters
 Part 1: COLOR AND ABSORPTION

– All solar water heaters use some kind of collector to soak up the sun’s energy. What did we use in the last investigation?
• Sand, soil, and water

– In this investigation what were our collectors?
• White and black plastic circles

– What were our two variables?
• White or black • Covered or uncovered

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Our Activity
We explored how the color of our solar collector affected temperature change in water. We also explored whether exposure to air affects temperature

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Our Results
Best collector color?
– The black collector got the water hotter because it absorbed more energy from the Sun.

Lid or no lid?
– The covered containers kept air from carrying the heat away (holds the heat in). If you blow on your soup does it get cooler?
• See Greenhouse Effect
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What Occurred?
How did the heat absorbed by the black

plastic collectors get the water hot? – An energy transfer occurred, where the heat was transferred to the water by direct contact just like it would if you poured cold water into a hot frying pan.

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Vocabulary Part 1
Absorb – to take up, soak in, or capture.

Black plastic absorbs the Sun’s energy. Reflect – is to bounce back. White plastic reflects the Sun’s energy Solar Collector – a material used to capture solar energy in a water heater or other device.
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Part 2 : Surface Area Effect
 We tested different sizes

 NONE
 1–Unit  2-Unit  4-Unit

(total surface Area=LxW) of solar collectors on pieces of cardboard. All collectors were black.  Variables
– – – – No collector 1 Unit Area 2 Unit Area 4 Unit Area

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Activity
 We placed plastic bags filled with 200 ml water and a thermometer onto each collector and measured temperature change in the sun every five minutes for twenty minutes.
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Surface Area Effect
Temperature Change
20 15 10 5 0 5 10 15 20 Surface Area
9

0 Units Baby Bear Mama Bear Papa Bear

Conclusion
We calculated the average temperature

changes in the sun of each surface area. We discovered that our data could be accidentally changed if we were not careful to make all conditions identical (tilt of solar collector) The larger collector surface causes water to heat up more and faster
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Vocabulary – Part 2
Surface Area is the total surface of

an object; for a rectangle or a square surface it equals length times width  A=LxW
This floor is 7 units x 3 units

– Or an area of 21 sq. units
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What is the Greenhouse Effect?
 The greenhouse gases in our atmosphere (N, O, and
small percentage of CO2, methane, H20 vapor, CFCs and oxides of nitrogen) act like a window, letting in visible light and keeping in the infrared heat. This maintains an average Earth temperature of 15 degrees Celsius (59 degrees F) which is nice for most lifeforms on Earth. – CONCLUSION: HEAT TRAPPED IN AN ENCLOSED AREA COOLS OFF MORE SLOWLY THAN AN AREA EXPOSED TO AIR. – Eg. An enclosed car, a garage, a greenhouse.
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Global Warming
 PROBLEM: increased

burning of fossil fuels and other pollution is increasing the amount of greenhouse gases (C02) causing an environmental concern.  This environmental concern is called global warming
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 Some scientists think that these human activities have increased greenhouse gases in the atmosphere, causing it to heat up more and even faster.

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Something About Light Energy
 Light Is Either Reflected  We see white light which

or Absorbed When It Falls on a Surface!  Electromagnetic radiation in waves – Visible light – Ultraviolet (sunburn owie!) – Infrared (heat) next to red

is many wavelengths of light together  We REFRACT light by bending it so we can see different wavelengths (colors) – Roy g BIV

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Light & Color
 Light can REFLECT (bounce off) so objects look white
 If object has pigment that absorbs some colors and reflects others, we SEE the

 A Black object has absorbed all the wavelengths.
 Material that absorbs light gets hotter because of increased kinetic energy

color that is reflected

(motion) of the atoms.

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Solar Houses
INVESTIGATION 4
– Using cardboard solar houses with picture windows, we explored various ways to construct solar houses to keep us warm or keep us cool – Using solar energy to heat surrounding air is called space heating – Solar energy can be transformed into heat energy and transferred from solar collectors to the surrounding air to heat solar houses.
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Space Heating
 We constructed our solar homes using our different variables:
 Interior Color (black/white)  Orientations (away or toward sun)  Insulation (two types)  Heat Sink  Double Glazed Windows  Curtains
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Activity
We took our solar houses outside and

measured their interior air temperatures for 20 minutes in the sun and 20 minutes in the shade. We then graphed our results to see which designs worked the best to maintain the heat.
– Our house with dark green curtains seemed to get the hottest and cool down the slowest
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Our Variable Results (Lamb)
Starting Air Temp. was 25 degrees Celsius
Oriented Away from Sun H39 net gain +5 L30 Rubber Foam Insulation H54 net gain +11 L36 Dark Fabric Curtains H54 net gain +14 L39
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Oriented Toward Sun H58 net gain +11 L36 cardboard only (hottest) Heat Sink (rocks,foil,H2O) H51 net gain +11 L36 White Interior H50 net gain +11 L36
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Fabric Insulation H50 net gain +11 L36 Double glazing H50 net gain +11 L36 Black Interior H51 net gain +11 L36
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More Vocabulary Concepts
 Heat that is created and

distributed throughout a r house simply by letting the sun shine in is passive solar heating (No mechanical or electrical devices are used)
 If heat is moved to

 Orientation – to set

another location with valves, fans, etc., the system is an active solar energy system
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something in a definite direction  Greenhouse Effect – Heating of a closed space when light energy enters, transforms to heat, and is trapped inside, resulting in heat buildup

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Content/Inquiry Notes
 Different methods of home building and design help warm homes and keep them cool.  Houses with black plastic interiors should heat up more and stay warmer longer white interiors
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 Houses oriented toward

the Sun heat up faster  Light transforms to heat (in collector) and is transferred from collector to the air (or water) by direct contact  IT’S WARM IN THE SUN!!!

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Keeping A Healthy Environment
 Access to energy that does not degrade (harm) the quality of the environment any further will be one of the most important human issues in your lifetime.
 Do your part!!!
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