Vee22
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Magnetic induction / electricity

Postby Vee22 » Sun May 15, 2022 3:17 pm

Hi, I’ve been making a hand powered electrical generator with magnets and a coil of wire. My 5th grade class has been looking at renewable energy. I was wondering why scientists haven’t done more to make renewable energy for houses that is powered by humans?
For example we could attach a stationary bike to a generator to make electricity as an alternative (free!) electricity source. Or maybe we could use static electricity from people moving around inside their houses to make electricity to power their homes?

bfinio
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Re: Magnetic induction / electricity

Postby bfinio » Tue May 17, 2022 4:56 am

Hi - this is a good question with a somewhat complicated answer. The very short answer is that humans use a lot of electricity, and the human body does not actually generate that much power compared to other sources.

To understand the longer answer, it helps to have an understanding of the watts (abbreviated W), the unit used to measure electrical power. Then, you can compare how much power common appliances in your house use, and how much power a human can generate.

Taking a look at a few google results, it looks like athletic humans can generate a few hundred watts of power during intense exercise, and more than that (around a thousand watts) in short bursts or sprints. An "average" person exercising might generate around 100 watts:

https://en.wikipedia.org/wiki/Human_pow ... able_power

https://www.pedalpc.com/blog/how-much-e ... -generate/

Now, compare that to power consumption of common household devices and appliances. Small things like an LED light bulb or a cell phone charger are usually around 10 watts. However, larger appliances - big TVs, computers, microwaves, dishwashers, washer/dryers etc - easily use hundreds or even thousands of watts. You can find long lists of appliances online like this:

https://www.daftlogic.com/information-a ... mption.htm

If you add up all those appliances and look at the average US household, electricity consumption averages to 10,715 kilowatt-hours per year:

https://www.eia.gov/tools/faqs/faq.php? ... er%20month.

(aside: note that a kilowatt-hour is a unit of *energy*, not power. Power is an amount of energy per unit time. One kilowatt is 1,000 watts. One kilowatt-hour means you used 1,000 watts for one hour).

Divided by 365 days, that works out to about 30 kilowatt-hours per day.

Going back to our human power output numbers - say you're an incredible athlete and you can sustain an output of 500 watts for one hour. That is still just 1/2 a kilowatt-hour, or about 1.7% of your household's energy consumption for the day! It would take dozens of people taking turns riding bikes all day to power a single house.

So, while human power output works as sort of a novelty to power small items like lights or phone chargers, it isn't very practical on a large scale. That doesn't mean people aren't trying though. I think you can find examples of gyms where the lights are powered by the exercise equipment in the gym. Scientists are also working on energy-harvesting floor tiles that can be put in high-traffic public places. But both of those are examples where you have lots of people - it just isn't as practical or cost-effective to do it at the scale of an individual household.

Hope that helps answer your question!

Ben

Vee22
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Joined: Sun May 15, 2022 2:57 pm
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Re: Magnetic induction / electricity

Postby Vee22 » Tue May 17, 2022 8:34 am

Thank you Ben.

That makes a lot of sense. The idea of making free electricity sounds nice but when I’m at home I like to play on my computer… I’m sure I burn more electricity than I would produce! LOL.

I didn’t know there were gyms that power their electricity from their members using the gym equipment. That is so cool!

I also like the idea of the energy absorbing tiles in public spaces! Every little bit of green energy helps!

Thanks for answering my question.


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