Hi, I have seen the STEK exhibition in Heureka, so I hope you will be able to answer my two questions:
1) Let’s imagine one of those round abouts on a playground for kids. How much electricity could one of them produce? Let’s take an imaginary kid of 5y.o. and 20 kilos of weight running around and spinning it. What if it is empty when the kid is turning it? What if it has another 4 kids sitting? what if 2 kids are pushing and 4 are sitting? Let’s say they are going on for 10 minutes non stop. The speed I don’t know. What will this energy be enough for?
2) Same question, but about a spinning class for adults. 40 stationary bikes and they are peddling non-stop for 45 minutes from moderately intense to very intense. Let’s say 10 women 45kg, 10 women 55kg, 10 men and women 65 and 10 80kg. What would that energy be enough for?
Thank you very much for your answer, I will use these results for my project during my UAS studies.
The kids part:
There is a handy calculator:
carousel total weight is 200kg(distributed evenly)
Diameter 2 meters
This has energy content of 5,4 joules corresponding 0,015 watt-hours which is about 1/650 of energy content of a mobile phone battery.
So, in theory, you could accelerate this type of carousel with your fully charged mobile phone 650 times!
Also, it if clear that this energy content is next to nothing. But flywheel batteries are being developed? Answer is high speed!
Doubling the speed gives the flywheel 4 x energy.
Other questions are simple to answer: adult can produce 100-300 watts using largest muscles. Children will produce a lot less, depending on many, many issues. 10-40 watts/child, to give some rough answer. Also, rotating a carousel is not the best ‘geometry’ for producing electricity. How they sit and who is running etc doesn’t matter, this is the energy content for this weight and this is the rough possible energy output for 1 child.
Also, using 50 watts, takes (in theory) only about 1 seconds to accelerate listed carousel to rpm 10.
And, 4 kids working hard(like accelerating carousel with generator installed or bicycling) can produce 50-200 watts depending on many, many issues, so energy generated in 10 minutes is about 8 – 32 watts-hours (about 1 – 3 times what mobile phone battery has). In euros, it is about 0,1 – 0,2 cents.
The adult part:
40 adults in ok or better condition can do a bit more than 10kW. A bit more that 7,5 kWh in 45 minutes.
750 mobile phone batteries. Typical apartment building consumes 1500 – 3500 kWh during a year, without heating energy.
Here is an example of pedaling power:
Janne Käpylehto, inventor, author