BRONZE

Human batteries

We will be seeing if we can generate electricity from body heat, and if so, which body type is most efficient for doing so.
Dependra Khatri Zartash Sandhu
Grade 8

Hypothesis

If we attach a thermopile to a shirt and put it on someone then it will generate energy because the human body produces enough heat to generate an electric current.

The ideal body features will be: Tall, Heavy, Female, Sapien(Human)

Research

There are a lot of ways to generate electricity with heat like using heat to make steam which is the most commonly used way but there is one other way called thermocouples. Thermocouples require no moving parts to create energy and make no pollution. A thermocouple takes advantage of the fact that electrons like to move from hot areas to cold ones. They give off a tiny amount of voltage (millivolts) but if you combine many of them they will give off a higher voltage. Thermocouples are normally used for sensing temperature in a lot of different applications from fire sensors to factory uses. Though they are used to sense the temperature, they still generate some electricity. There are different types of thermocouples J, K, T, E, R, S, and B. In our project, we are going to use a type J thermocouple which consists of iron as the positive leg and copper as the negative leg. Most of the time type J wires are made up of iron and constantan which is 45% nickel and 55% copper. The lowest temperature a type J can sense is 0℃(32℉) which means it will generate energy with body heat. There are two types of junctions in a thermocouple wire one is a cold junction that stays at room temperature and 1 hot junction where the heat is applied. The cold junction is attached to a copper wire and the voltage is measured at the end of the copper wires. 

This is a diagram of a thermocouple:

Now imagine that the hot source is the person and instead of running into a voltage counter, it runs into other thermocouples. By doing this we would have a thermopile powered by human body heat. A thermopile is multiple thermocouples combined. But that's not using it to its full potential. By cooling the cold junctions we can heighten the temperature gradient and generate a stronger electric current. Factories do this while operating thermocouples, they dunk the cold junctions in an ice bath to drastically decrease the temperature. For now, though, we'll be using icepacks to make greater temperature differences.

    This idea will not work if we don't have a heat source, so our heat source is going to be the body. So how does our body create heat? The body has many methods of maintaining your body temperature such as Vasoconstriction. Vasoconstriction is when the blood vessels under your skin narrow to reduce the amount of blood that gets to your skin. When this happens it retains your body heat. Another way your body produces heat is thermogenesis, which is when your muscles, organs, and brain produce heat in many ways such as shivering. One last way your body produces heat is hormonal thermogenesis. Hormonal thermogenesis is when your thyroid glands release hormones to increase your metabolism, this increases the amount of energy your body creates resulting in more heat.

 

Variables

-natural heat of the subject

-activities that are done during the span of the testing

-temperature of the room

-length of the testing period

-height and weight of the subject

-clothes that are worn over top by subject

Procedure

Construction Materials:

Shirt

speaker wire (has to have iron and copper)

Multimeter

needle

string

scissor 

Steps:

  1.  Cut copper and iron wire in equal length (they should be about 9cm)
  2. Twist the tips of one iron and one copper wire together. Do this to all of them (this makes a thermocouple)
  3. Make a small cut in the shirt  and put 1 thermocouple in the hole and stitch it up (repeat for the rest of them)
  4. connect the ends sticking out of the shirt together (make sure it is copper to iron or vice versa)
  5. There should be a pair of thermocouples that aren't connected, connect the copper wire of one and the iron wire of the other together.
  6. now you can attach a multimeter to the ends test the voltage or attach it to a battery pack and store the energy

Testing:

  1. A subject is chosen and asked to sign the consent form
  2. The subject's height, weight, gender and species is determined
  3. They are to remove any extra layers and only wear a standardized uniform
  4. The subject is asked to put on the shirt
  5. The multimeter is tested to see if it works
  6. A voltage is immediatly taken and several more over a period of 1-2 hours
  7. An average is taken from the recorded voltages and recorded
  8. This process is repeated with as many subjects as necessary (in our case, 7)

Observations

We realized heavy males made the most energy while lighter males produced less heat. Also, females make more electricity than males of the same weight and height but our data is biased toward men since not many females volunteered to do the experiment.Another thing we noticed is that after gym class the electricity produced was more than other parts of the day. Here are graphs showing our observation

imgpsh_fullsize_anim (527×404)

Analysis

In the experiment several points of information can be gathered. First of all, females are definitely much warmer than males. Second of all, the biggest factor in determining heat emission is height, not weight. By looking at the graphs, we can see that those who scored as taller held a higher average than those who were heavier. One factor not accounted for during the experiment though, was time of day. For example, someone in the afternoon immediatly coming back from gym class would be far warmer than someone who just got to school in the morning. Even though this factor was not accounted for, it was solved. By doing several experiments on the same subject at different times, we could assure that the time of day had no affect on the results. 

Conclusion

This experiment was to see if we could generate electricity from body heat, and to see who would generate the most. The purpose was to see if a passive renewable energy source could be made. According to the results, the one who generated the most energy was the tall, female human. Though she wasn't the heaviest, if we look at the results for males, we can see that the heaviest one generated the most energy. This proves a direct correlation between weight and heat emission. All this means is that our hypothesis was correct. The electricity wasn't much, but it was still something. But these results are excluding subject R. Subject R is our special guest, the cat. In the competition to see who could generate the most heat, cats won by a long shot. If we had more feline test subjects we could create a better average for the sp;ecies as a whole. This begs the question, if body heat is the future of renewable energy, then will overweight cats lead us to it. Back onto the huan subjects, a discovery that emerged was that height has more to do with body heat than weight. This claim is supported by the fact that the tall subjects had a higher average voltage than the heavy ones. In the end, this project was a massive success. Body heat most likely won't be the future of renewable enrgy, but only time will tell.

Application

There are numerous applications for this if it was made more efficient with better technics and manufacturing. Some uses for this are, charging a phone, powering an electric car or storing the energy in a power bank that can be extracted somewhere else such as, to a phone, store it for later somewhere else via a special hanger or closet and selling the energy off to others. With more refined thermocouples and designs, there can be much more energy produced and it will be renewable and pollution-free. Though it would require more enrgy to keep the host alive than it produces, the spare energy it produces as the host wears it will add up over time.

Sources Of Error

faulty wires

different shirts the participants wear under the projects

Temperature inside room

Activities that are done by participants

food eaten by participants (mainly spice foods)

 

Acknowledgement

We would like to thank all the subjects for participating in our test. We would also like to thank Mr. Tackney for supervising us and Dependra's dad for the wiring and multimeter.