CHM 110 - CHEMISTRY AND ISSUES IN THE ENVIRONMENT
List of Chemicals for the Home Labs
Home Laboratory # 3
C. Ophardt, Elmhurst College c. 2001

ABSORPTION OF SOLAR RADIATION - GREENHOUSE EFFECT


 

PRE-LAB: GREENHOUSE VISUALIZER

GREENHOUSE VISUALIZER


The visualization graphics have been created using a copyrighted program "Climate Watchers".
Daniel C. Edelson (d-edelson@nwu.edu), Institute for the Learning Sciences and School of Education and Social Policy, Northwestern University, 1890 Maple Avenue, Evanston, IL 60201

Energy from the sun provides the heat for the earth's surface and atmosphere. The energy provided by the sun to the earth each day must be in balance with the energy that is radiated back into space from the earth. A hot "body" such as the sun emits radiation in the short wave region (U.V. and visible), while the earth a cooler "body" emits radiation in the long wave region (infrared, IR).
The purpose of this investigation is to use data from satellites to understand the various energy relationships of the earth and its atmosphere. In the process a greater understanding of the greenhouse effect will be achieved.

INSOLATION:

The energy from the sun called "insolation" contains ultraviolet and visible light. The majority of the U.V. light is absorbed by the ozone layer and heats the atmosphere, as a consequence the majority of the solar output that reaches the earth's surface, and is absorbed, is in the form of short wave radiation of visible light. The measurements are made by satellite above the atmosphere. If no other effects are operating, the surface of the earth should have an average temperature of -18 degrees C.

ALBEDO:

A significant portion of the incoming solar radiation is immediately reflected back into space by clouds, ice, snow, sand, water, and other reflecting surfaces. Shortwave Reflectance measures the amount of the sun's energy that is reflected due to the albedo of Earth-Atmosphere system. Short wave radiation is measured in watts per meter squared. The measurements are made by satellite above the atmosphere.

SHORTWAVE ABSORPTION:

On the average about 50% of the incoming solar radiation is absorbed by the earth surface, while another 20% is absorbed by the clouds and gases such as ozone in the atmosphere.

SURFACE TEMPERATURE

Surface Temperature provides a measure of the temperature all over the Earth. The temperatures are measured in Kelvin. To convert to Celsius temperature subtract 273 from the Kelvin temperature. The heat at the surface is translated into long wave radiation.

LONG WAVE TERRESTRIAL EMISSION:

Outgoing Long wave Terrestrial Emission (also called long wave radiation) measures the amount of energy leaving the Earth arising from the Earth's surface temperature. Long wave emissions of energy are in the thermal infrared, IR, region of the spectrum. This IR energy is in the form of heat, analogous to the heat from a hot electric burner on a stove.

GREENHOUSE EFFECT ENERGY:

Greenhouse Effect is the amount of energy retained by the Earth's atmosphere. The natural Greenhouse Effect is not a bad or unusual thing, and is absolutely necessary for maintaining life on Earth. However, if the amount of energy stored in the atmosphere increases, it could cause the average temperature of the earth to increase as well -- this is called global warming and could have significant effects on earth's basic climate and agricultural cycles.
The Greenhouse Effect Energy stored in the atmosphere is calculated by computing how much radiation is on average produced by the surface temperature (using a conversion method called the black body model) and then subtracting the amount that leaves the atmosphere (i.e. the outgoing long wave radiation). The difference is the Greenhouse Effect Energy being retained in the atmosphere measured in watts per meter squared.
As the IR energy is emitted from the earth's surface, only a small fraction of the energy actually escapes to outer space. Two major molecules, water and carbon dioxide temporarily absorb specific wavelengths of IR radiation that correspond to the energy required to bend the molecules. Shortly, the vibrationally excited molecules lose their energy either by colliding with other molecules and heating up their surroundings, or by remitting the radiation. Either process occurs in all directions, half of the energy flows upwards toward outer space, while half flows back to the surface and further heats the surface and the atmosphere. This process is known as the natural greenhouse effect and results in the average surface temperature of +15 degrees C rather than -18 C. This natural greenhouse effect makes the earth habitable. As a comparison, Venus has a much higher concentration of carbon dioxide, an extreme greenhouse effect with surface temperatures of as high as 800 degrees F. On the other hand, Mars with little atmosphere and virtually no gaseous carbon dioxide has temperatures that vary from 80 during the day to -100 degrees F at night.

PERCENT GREENHOUSE EFFECT:

Greenhouse Percent measures the amount of energy stored in the atmosphere. So, its quite similar to the Greenhouse Effect Energy. However, it shows the Greenhouse Effect as a fraction of the total possible energy that could be stored in the atmosphere, rather than as an amount. This way of measuring the Greenhouse Effect is useful for detecting changes in it over time, since it measures it as an absolute number, thus providing easy comparison between different months or years.

This all is partially summarized in: ProfONotes: Graphic summarizing the Earth Energy Balance

PROCEDURE TO USE THE GREENHOUSE EFFECT VISUALIZER

Pre lab Questions: (4 points)

The visualization graphics have been created using a copyrighted program "Climate Watchers".
Daniel C. Edelson (d-edelson@nwu.edu), Institute for the Learning Sciences and School of Education and Social Policy, Northwestern University, 1890 Maple Avenue, Evanston, IL 60201

Each visualization has been pre-formatted for your use.


TEMPERATURE AND MAP RESOLUTION:
Just like maps, some visualizations are very detailed while others provide a much more general "averaged" view. The level of detail provided by a visualization is called its resolution. The resolution is described by how many degrees of latitude and longitude are covered by a single averaged number.

QUES. 1: For example, look at January surface temperature at the highest resolution at 2.5 degrees per square. Give the coldest and warmest temperatures and general location by matching the colors with the color bar.
The coldest temperature is _________ at __________ ?

a. 55 F at Brazil b. 96.5 F at Brazil c. -46.4 at North Pole

Ques. 2: The warmest temperature is _________ at __________ ?

a. 55 F at Brazil b. 96.5 F at Central Australia c. -46.4 at North Pole

Ques. 3: The mean temperature for the whole world? ________.

a. 55 F at Texas b. 96.5 F at Central Australia c. -46.4 at North Pole

TOTAL RADIATION BUDGET


The earth not only absorbs energy from the sun it also has to give it off energy by retransmitting it. This energy balance is called maintaining the earth's radiation budget. At different parts of the year some portions of the earth absorb more heat than they give off whereas other places give off more heat than they absorb.
These next visualizations show the radiation budget for the earth as a whole.

QUES. 4-6: Read the mean value to give the global single average (Read this in the Data Set in the upper left corner). These are given for March. Report the values read from the map obtained. The energies are given in watts per meter squared in the multiple choice questions below.

Ques. 4. Insolation (March) - The radiation comes from the sun to earth in the form of sunlight.

a. 345 b. 439 c. 15.5

Ques. 5. Shortwave reflectance (March) - The sunlight that is reflected is called short wave reflected radiation. This radiation does not affect processes on earth, since it is never absorbed. Therefore, reflected sunlight does not cause anything to heat up.

a. 7.5 b. 189 c. 99.4

Ques. 6. Shortwave absorption (March) - The sunlight that is not reflected is absorbed by the earth- atmosphere system.

a. 391 b. 246 c. 7.97


Ques 7. Calculate the percentage of sunlight reflected compared to the total insolation? ____________ (Show work)
Note: Answers may not agree exactly with graphic link - Energy Balance on bottom of the Pre lab. That is OK.


Ques. 8. Calculate the percent sunlight absorbed compared to the total insolation? ___________ (Show work)

Ques 9. Outgoing Long wave Terrestrial Emission (March) measures the amount of energy leaving the Earth arising from the Earth's surface temperature; also called terrestrial radiation or emission

a. 118 b. 300 c. 233


Greenhouse Effect Energy (March) - Substantial amounts of energy are stored in the earth's atmosphere. The amount and location of this energy also varies with the seasons. __163_This value is provided for you from a calculation that I did for you____

The Greenhouse Effect Energy stored in the atmosphere is calculated by computing how much radiation is on average produced by the surface temperature (using a conversion method called the black body model) and then subtracting the amount that leaves the atmosphere (i.e. the outgoing long wave radiation). The difference is the Greenhouse Effect Energy being retained in the atmosphere measured in watts per meter squared.

Ques. 10. Percent Greenhouse Effect (March) - Shows the Greenhouse Effect as a percent of possible energy that is stored in the atmosphere compared to the total outgoing energy produced by the earth as a black body. _____
a. 13.8 b. 26.8 c. -7.71

Ques. 11. Carbon Dioxide Emissions - Cite three general areas of the world where the largest emissions of carbon dioxide occur as a result of burning fossil fuels. THREE ANSWERS REQUIRED.

a. Western United States b. Eastern United States c. South America d. Western Europe e. Russia f. India g. Eastern China

Ques. 12: Note the notation of units, for example 4.5e+5 stands for exponential notation = 4.5 x 10 ^5 or 450,000; mi^2 means miles squared.

What is the exact values and give the exact units of measurement for the mean values of carbon emissions?

a. 5.27e+06 pounds carbon per mile
b. 415,000 pounds of carbon per square mile per year
c. 41,500 pounds of carbon per square mile per year

ProfONotes: Graphic summarizing the Earth Energy Balance


INTRODUCTION TO THE SOLAR ABSORPTION LABORATORY:

What is the most effective method to absorb solar radiation?

Solar radiation will be absorbed a series of cups containing colored solutions. The amount of heat absorbed will be calculated and applied to a method of heat storage.
Clear plastic cups filled with colored water, and/or placed in a quart jar in bright sunshine for one hour and the change of temperature is measured. Using the volume of the water and the temperature change, calculations are made to determine the most effective "absorber".
Directly or indirectly, solar energy has provided almost all of the Earth's energy since it was formed. The amount of radiation energy that reaches the surface of the earth in one or two weeks is equivalent to the fossil fuel energy stored in all of the earth's known reserves of coal, oil, and natural gas. In the United States, the solar energy that reaches 1/500th of the land area could satisfy our entire present energy needs if it could be converted at only 20% efficiency. Thus, development of efficient absorbing materials is very important in the search to harness solar energy.

PART 1: EXPERIMENTAL PROCEDURE USING ONLINE DATA: (7 points)

****All Data for Part 1 is given online****
****You do not actually have to complete these procedures. Dr. Ophardt did them for you and took pictures of the results. You should read the procedures to see what was done, record the data, and answer the questions.*****

One objective of this lab is to apply the scientific method in the design of one control (plain water) and four variable experiments to find the best solar absorbing material. Exact directions will not be given, but some suggestions about variables will be made.


General Procedure of the Experiment:
1. Use a clear plastic cup and fill it with exactly one half cup of clear tap water as the "control" experiment. For variable changes again use exactly one half cup of tap water and add 10 drops of different food color dyes.

Alternative: Use clear water as the control, but then use a variety of solids such as sand, soil, salt, or sugar instead of the colored water. Still use one half cup.

2. Quart jar Greenhouse: As one variation, put a wide mouth quart jar upside down on top of the cup. Make a comparison to a cup that does not have the quart jar. The quart jar may be left plain or it may be lined with a semicircle of aluminum foil, plain white paper, or black paper to act as a solar reflector "concentrator" of the solar radiation. Be sure to leave an opening for the sunlight to enter. ProfO Notes: Sample Set up Graphic

3. Let the cups stand in the location for the experiment to allow them to come to room temperature for about 30 minutes before preceding. Record the initial temperature (T init.) of each sample on the data sheet. Then place all of the samples in the direct sunshine* for 1 hour. Finally, record the temperature (T final) of each cup. (The temperature should increase 1-10 degrees)
* Note: If strong sunshine is not available, then use a strong lamp or light bulb placed about 1-2 feet away from the cups.


QUES. 13: EXPERIMENTAL RECORD:
Write the exact details of the experiments that you conduct as this will be evaluated on the proper use of the scientific method i.e. use of control and three variables. The minimum requirement is to use a control and three variables - different solutions in the cups, with and/or without the quart jar. How did you set up the experiments? What is the hypothesis of why each jars is set up as it is? Where did you put the jars? Try to be a little bit descriptive of what you did in this experiment. Do not forget to answer this question. Even though you do not actually do the experiment, still talk about it based upon the pictures.

ProfONotes: Online Experimental Set-Up


QUES. 14: DATA TABLE:


Water Volume = 1/2 cup = 120 ml; also Water Weight = 120 grams.

Time On __11:30 AM______ Time Off ___12:30 PM_______ Absorption Time = 60 Min.

Assume the solar radiation is only absorbed on the top surface of the container:

Diameter (d) of cup Absorbing Surface __6.5__ cm

Ques. 14: Calculation: Top of Cup - Absorber Surface: Area = 3.14 multiplied by (diameter squared divided by 4) = _________ cm2
(approx. ans. 25-50 square cm) Show your work.

TABLE 1: TEMPERATURES OF THE COLORED WATER ABSORBERS

   Water  Variable 1   Variable 2  Variable 3  Variable 4  Variable 5  Variable 6
 Brief Desc.  plain water red dye in water red dye in water covered by beaker red dye in water covered by beaker with aluminum foil  omit unless doing Part 2  omit unless doing Part 2  omit unless doing Part 2
Final Temp  19.5  21  23  24      
Initial Temp  15  15  15  15      
Temp Change              

Ques. 15: Report the temperature changes

Water _____ Variable 1 _____ Variable 2 _____ Variable 3 _____


Variables 4,5, 6 are usually omitted, unless you do the optional Part 2.

Conversion Units:
1000 cal = 1 kcal
Specific heat of water = 1 cal / g oC (no math is implied - these are just the units of specific heat. 1 cal is absorbed by water per gram per degree Celsius)
100 cm = 1 meter (m)
30.5 cm = 1 ft
1 ml of water = 1 gram of water because the density of water = 1.0 g/ml

CALCULATIONS:

 Water  Variable 1  Variable 2  Variable 3  



Show a sample calculation for each question below.

QUES. 16
. Calories absorbed per 120 ml water per hour =
specific heat of water x grams water x temperature change (ans. Q15)

 Water  Variable 1  Variable 2  Variable 3  
         



(ans. approx. 200-1400)

QUES. 17. Kilocalories (kcal) absorbed per hour ((ans. Q16) divided by 1000)

 Water  Variable 1  Variable 2  Variable 3  
         



(ans approx. 0.2-1.4)

QUES. 18. Kcal absorbed per square centimeter per hour
(ans. Q17) divided by the Total cup surface area (ans. Q14)

 Water  Variable 1  Variable 2  Variable 3  
         



(approx. ans. = 0.005 - 0.05)


QUES. 19. Convert one square meter to square centimeters: ______________
(area = length X width)
(1 meter = 100 cm)


QUES. 20. Kcal absorbed per square meter per hour
(ans. Q18) multiplied by (ans. Q19)

 Water  Variable 1  Variable 2  Variable 3  
         


(approx ans. = 50 - 2000)
As a comparison: Average Solar Input for Illinois = 1200 kcal / hr m2

QUES. 21: Which type "solar absorber" was the most effective solar collector? Least effective? How many kilocalories of heat are absorbed per hour per square meter for the best and the poorest "solar absorber"? Do the results agree with your hypothesis in Question13?




QUES. 22:
Application: If a wall 10 feet high and 20 feet long on the south side of your house had the same absorbing characteristics as the best solar absorber, how much total heat could be collected in an 8 hour day?

a. First convert feet to cm then meters. Then find the area in square meters(length x width). Answer = _____________
(approx ans. on wall area= 15- 25 square meters)
Show work.

 


b. Then use (ans. Q22a) and (ans. Q20) and eventually the 8 hours - the sun only shines 8 hours in the winter not 24 - to find the total heat absorbed by the solar panel in an 8 hour day.
(approx final ans. = 10,000 - 60,000)
Show work.

QUES. 23: Using the above results, calculate the percent of heat that could be absorbed and supplied by your solar collector, if the house needs 17,640 kcal per hour on a typical cold winter day.

a. First calculate the total heat needed by the house in kcal for 24 hours for the house.
Show work.

 

b. Then calculate the percent heat that could be supplied by the solar panel. Use formula below.

percent heat from solar panel = heat supplied by absorber solar panel divided by total heat needed by the house, and finally multiply by 100 to get percent.

QUES. 24: Describe a design for a passive solar heated house, showing how (and location) the solar collector wall of water would be utilized. Remember that the solar collector has to reradiate the heat during the evening hours. Do not just copy the diagram in the text since this uses "active" solar heating. Some internet sources show a concrete wall; I want you to use the wall of water idea. This is an application question asking you to apply what you did in this experiment to a large scale house. Try to be creative and use the materials used in this lab, but make them into a large solar panel as described in QUES. 22. This is worth 2.5 points.

Solar Home Passive designs

 

Part 2: Optional and Extra Credit - At home collection of lab data (4 points)

Do Part 1 at home using solar energy. You could try two experiments. The first is to use a cup of plain water. The second would be to use a cup filled to the same depth as the water but use solid salt or sugar in place of the water. Using these conditions it would not be necessary to cover them with another jar. The rest of the experiment would be the same.

Carry out the same calculations as was done with the computer generated data.

Report carefully your procedures, make table of the data, and show the results of the calculations, and the conclusions.