# ELI5- why do we need to find different ways to generate electricity if the main thing is turning the turbine? Can’t people turn it manually?

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ELI5- why do we need to find different ways to generate electricity if the main thing is turning the turbine? Can’t people turn it manually?

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A person can manually crank at maybe 200 watts.

That’ll power a medium-sized PC.

So for every computer in the world would need to be a person on a treadmill.

And that doesn’t speak for factories, cars, lighting, heating…

Sure can. In fact you can buy emergency lights and radios with a hand crank on them. And in some parts of the developing world there are generators powered by peddling a bicycle. As long as the generator spins, you get power, it doesn’t really matter how you get it to spin.

The reason you can’t head down to your local power plant and offer to replace their need for fuel is because the amount of power you get out of a generator depends on its size and the bigger it is the harder it is to turn. Also the more power it generates the harder it is to turn. A human, and even a whole bunch of humans, simply can’t turn a big enough generator fast enough to generate the amount of power needed.

Also, even if a person could, you are just trading off the power source. People still need fuel, it is just in the form of food. It is massively less efficient to grow food, feed it to a person, to create the energy needed, to turn a generator, to create electricity. It is much more efficient to burn various kinds of fuel to generate heat to create steam to turn a generator. Less energy goes in for the amount that comes back out.

Instead we search for the most efficient, and these days least polluting, way of spinning the turbine to turn the generator. Some forms are very efficient for the power that goes in, such as hydro or wind. We harvest power that was there naturally to do the work (the water was going to flow and the wind blow regardless if we stuck anything in its path to let it turn). Alas both of them have limits in where you can put them and how much power you can get back out. So we continue to use other options like coal, natural gas, and nuclear. All of which create various levels of undesirable pollution.

No, that’d be too much effort for humans. We use far more electric power than we can generate using our bodies.

>In 2020, the average annual electricity consumption for a U.S. residential utility customer was 10,715 kilowatt–hours (kWh)

https://www.eia.gov/tools/faqs/faq.php?id=97

10,715 kWh ÷ 365.25 days/year = 29.3 kWh of electricity per household per day.

>Over an 8-hour work shift, an average, healthy, well-fed and motivated manual laborer may sustain an output of around 75 watts of power.

https://en.wikipedia.org/wiki/Human_power#Available_power

75 Watts * 8 hours = 600 Wh, or 0.6 kWh. That’s only 1/50^th of the electricity an average household uses in a day.

So we are bad at turning things to produce power. Some bike used to come with a little generator to power the headlight. When you clicked that light on you could really feel the difference it made, and that’s just a little 1/4 watt bulb.

Here’s a great example video. https://youtu.be/S4O5voOCqAQ

So if you are as strong as an Olympic cyclist you can manage to barely toast one slice of bread.