YSI 1995 / Reporting Groups / Solar Energy

Students: DeSheadra Benford, Jameene Banks, Ne'el Williams


Measuring Energy From the Sun

DeSheadra Benford, Jameene Banks, Ne'el Williams

De Sheadra's part

Good morning. The purpose of our experiment was to see how much energy the earth receives from the sun. First I will explain what energy is. Energy is the ability to do work. No matter what you say or what you do, you're using energy. For example, playing video games, trying to get to the next level, from the food we eat (which was originally grown by the sun), or even walking you're dog, A good source of energy is our star, the sun.

In our experiment, we measured the sun's rays by using a cup of coffee. Let me explain in a little bit more detail.

Specifically, what we did in our class was measured how much energy we receive on earth from the sun. The materials that we used were: four styrofoam cups, two of them covered with plastic, two of them in aluminum foil, filled with 200ml of coffee, four digital thermometers, and clocks.

In our process, we used celcius because with these thermometers, you have to set it to whatever measurements of temperature you wish to use. The temperature measurement is important with this process because all of the calculations and formulas involve Celcius. If we would have calculated our data in Fahrenheit, all of our calculations would have been wrong.

Jameene's part

We took the end of the wire and put it into the coffee and took the temperature before we went outside into the sun. That gave us our starting temperature which averaged around 80 degrees. Next we took the cups of coffee out and sat it in the sun and monitored the increase in temperature for seventeen minutes. the final temperature averaged around 90 degrees.

I know you're all wondering why we used coffee instead of water. Well, we used coffee instead of water because coffee is black, without milk and/or cream. Since dark colors absorb light , it allowed us to trap the light in the coffee and measure the temperature accurately. When we finished taking the temperature of the coffee, we had all the data we needed to make our calculations. We'll have Ne'el explain the exact calculations.

Before she explains ,though, I want to briefly give some defintions to some units that you may find difficlt as we go along. In our experiment, we measured the amount of energy in calories. A calorie is a unit of energy that measures one gram of water being raised one degree. For instance: if you in gram of water in a container and the temperature was raised two degrees, two calories of energy has been transferred into the water. Basically, the degrees multiplied by the grams will give you the calories of energy.

A joule is also a measurement. One joule represents 4.186 calories. Calories are basically used when talking about food and joules are used when measuring electricity. When you receive your electric bill, the amount of energy that you have used in a month is given to you in joules or in a way that you can calculate them into to joules.

Ne'el's Part

As Jameene explained, I've measured the amount of energy being transferred from the sun to the cup of coffee. Our Starting temperature was around 80 degrees F which was about 27.6 degrees celcius. After the 17 minute period, the final temperature was around 90 degrees F, which was around 30.2 degrees C. Then we had to follow the instructions in our pamphlet to find out exactly how to calculate the amount of energy.

We first had to convert 17 minutes to seconds which was 1.020 seconds. This is how we got our elapsed time (ET) which was exactly how long it took to do the entire experiment. Next we subtracted the festooned temperature from the first temperature to get the temperature increase. That number was 2.6. The next thing we had to do was plug in he numbers to the total energy transferred formula which was (TI)x (4.186)x (vol of water in container). when we multiplied that we came up with 2.176 joules. from there we had to get our energy flux. In this formula we had to divide the total energy ransferred by the surface area by the elapsed time. This computation gave us .0524333 joules per centimeter squared per second. The energy flux is actually the final answer to our question which was how much energy do we, here on earth, receive from the sun.

Go back to the Solar Energy group page.


Go back to the YSI 95 On-Line home page.