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Comment by airbreather | Hacker News Reader

If you go to here and plug in some numbers

https://www.omnicalculator.com/ecology/wind-turbine

You see that at around 0.2m blade length a HAWT will generate 40W at 28 mph wind. 28 mph is "Strong Breeze", according to the National Weather Service and in which you probably really don't want to be camping.

Strong Breeze = "Large branches in continuous motion. Whistling sounds heard in overhead or nearby power and telephone lines. Umbrellas used with difficulty."

But when you get down to 15 mph (moderate breeze) it's only making 6 watts, and at 8mph (gentle breeze) it's making 1 watt.

That is assuming steady wind to think you will get that continuously, derate accordingly.

I suspect there will be some gap between expected and actual performance for many people.

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Still, it can be useful since certain places reliably get strong winds. Think of all the sports that rely on windy conditions, then consider that those sports are conducted far away from the grid. That's your target market.

The best use-case I can think of is when hiking to the top of a mountain or large hill, where the top will be exposed and have much higher windspeeds than might be found in the camp site you came from.

Maybe a hut should have one of these

Well yeah, but a hut could have something a bit more robust, with a larger battery bank. This is optimised for weight, which a fixed installation does not need to be.

Wouldn't solar make more sense? And they are already on the market today.

Thin film photovoltaic is definitely better on a watts-per-kg basis, but it's no good for the charge-while-you-sleep use case.

Also, most portable devices on the market won't provide you with enough power for charging electronic devices in cloudy conditions.

My ideal combination to cover about 80-90% of power needs whilst camping/hiking/cycling would be a combination of water turbine (for rivers or tiny streams) and solar.

In case I'd be hiking in an area with no water supply, I'd consider something like a wind turbine. Yet, I wouldn't know why I would want to hike in an area with no water supply ;-)

I'm surprised they don't sell some kind of reciprocating dynamo-type thing for hikers to strap to their knee to charge while walking.

Doesn't that just increase resistance to your walking, thus is equivalent to you converting calories to battery energy? Wind and solar would be additional energy over what you brought as stored calories or food.

Going by a random Reddit thread [1], it takes less than 5 calories to charge an iPhone. I think that kind of device is already on the market though.

You're not gonna power a heater or aircon through body movement, but devices should be fine.

1. https://www.reddit.com/r/theydidthemath/comments/693daq/comm...

It's just a unit conversion, you don't need to cite reddit.

A Calorie is slightly more than a watt hour.

That's why taking a nap is important

Unless you hike the night shift...

But wind usually drops at night.

It also is only about a meter or so up from the ground. You rarely get a strong breeze there even if there is a strong breeze blowing.

This is correct but if you use it at home you can place it on the roof or on a terrace or stick it to a pole. I didn't research the subject, maybe there are better turbines for that use case.

“On a roof” may not matter much if neighboring houses are as high as yours. You want to be higher than anything close by.

If you’re going to use a longer pole, portability goes out of the window, as the pole will have to be stronger, too.

Then, you might as well get an even stronger longer pole and increase the turbine diameter. Micro wind turbines rarely make sense.

It's great at generating clicks-per-blogpost though.

Wouldn’t you leave it at camp (or a prominence next to your camp) and have it constantly trickle charging a battery?

It would be charging itself all day and all night at a couple of Watts. Then when you come back to camp you speed charge your phone at a full 50W.

I live in North Dakota. I think practically everyday is moderate to strong breeze here.

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