That's not "a fit man" that's a trained and fit cyclist, good marathon runners (2h15) were measured at an average 300W over the run, a fit adult might reach 200W.h over an hour or two, over long periods of time (e.g. an entire workday) you won't get much more than 100W.h if even that, an average fit labourer would be around 75W.h.
And that's mechanical in all cases, not electrical, you then have to factor in conversion losses. While a large rotary generator is ridiculously efficient (98~99%) it doesn't scale down that well (you'll be at about 80~90% at the generator output) following which you still need to remove the losses from the voltage regulator, battery, and possibly AC converter.
And then you still have the issue that your base energy sources (people) is not really efficient at converting food to mechanical energy in the first place.
Frankly, you'd be better off with a team of draft animals powering a big crank/wheel (with a flywheel for regulation), the average draft horse can produce ~740W (1hp) sustained. There's a reason why they (and oxen and other beasts of burden) have been used until engines became a thing.
('Only' because you need to do 580W to gain those six seconds. 2% faster = 6% more power)
It's just pointless to generate electricity by human power. It's not pointless to ride a bike.
440 watts for a world hour record.
350 watts for one hour, once a day, would be challenging to maintain for one week.
First of all, human power releases tons of carbon dioxide just like burning fossil fuels does .
Second of all, modern society currently depends on burning millions of years of stored sunlight energy in a matter of centuries (i.e. fossil fuels). Human power doesn't begin to compare. Bang Goes The Theory (BBC show) did an entire episode on this. It's shocking how many bicyclists were needed to run a tiny household .
I was disappointed that for all its calculations, the article completely avoided the question of "How green is human power?" Instead, it just repeated "could become one of the cleanest energy forms available".
But they had to, of course - answering that would have destroyed the entire idea. Fueling humans burns a huge amount of carbon, and neither the food > muscle conversion or the muscle > electricity conversion is even passably efficient.
(This is assuming you didn't use a bunch of fossil fuels to create and transport food in the first place, and you're instead using human/animal power to do that.)
On a bike I can do around 220W for an hour, and 160W for an indefinite period (have done up to 12 hours before).
Biking is known to be 20-25% efficient from calories burned to power at the wheel, so that's ~700 kCal/h for an hour at 160W.
My idle consumption is ~1600 kCal/day, or roughly 70 kCal per hour, so riding on the bike uses 10x as much; therefore I'm going to be producing 10x as much CO2 (obviously).
It takes ~140 L of oxygen to burn those ~700 calories, resulting in ~110 L of CO2.
So if I do a 4 hour ride at 160W to produce maybe 600Wh of energy after conversion inefficiencies, that's 2800 kCal just for the ride and 4400 kCal for the whole day, around 2.75x my idle consumption.
Disclaimer: I've done this quickly. Feel free to point out any errors.
> Whether a human eats the plant or it decomposes naturally, the same amount of carbon dioxide is released.
Yes, but we produce agricultural crops to meet demand. If as per the calculations above, every human suddenly started consuming 2.5x as much food, we'd have to grow more.
And yes, this is part of the carbon cycle. The problem is that we use fossil fuels and release CO2 above and beyond what's part of the normal cycle.
Unfortunately, agriculture is a major driver of deforestation (and forests are excellent at actually sequestering carbon in the ground). It also requires trucks, boats, and planes to haul supplies to farms, work the land, move water around, and transport the produce to stores. You have processing and packaging that rely on fossil resources (paper, plastic, metal cans...)
That doesn't even touch on the impact of meat production, which is several times worse for the environment.
Food consumption is absolutely not carbon neutral. You're far better off taking public transportation to work (if available) than walking or riding a bike, if you care about the environment.
But it's all the other costs of owning a car that make it so much more expensive: depreciation, licensing, registration, maintenance, blah, blah.
But most people are in an unwanted caloric surplus so it's really even better than this for those people.
I choose not to drink pure canola oil because reasons. But if I did, my ride to work would be fueled by 30mL - so I could maybe just start taking a shot in the morning and a shot in the evening. Yummy.
You can just make some delicious fried or oily snack, like crisps or chips or sauteed spinach, or fried what-have-you.
...but even a shot of oil is more healthy, pleasurable and hygenic (assuming you burn it all) than filling your tank with petrol :)
It's greener in a pleasantly 'immediate' way - i.e. you could quite literally be keeping the lights, music system, etc on at the gym :-) And what's more, assuming power costs are a non-trivial overhead, it could even result in lower membership fees.
If somebody opens a gym like this, sign me up!
Right off the bat, the sentence "Unlike fossil fuels, human power can be a clean energy source, and its potential increases as the human population grows." This is utter bullshit. The modern food supply is dependent on huge amounts of fossil fuels and mined minerals to create fertilizer. Much more oil just goes into feeding a human than you'd ever get out of him.
Hu? Where do you [they] think the human power comes from? It comes from food - you could just burn those plants for fuel, and skip the useless multiple conversion.
What does flowing the energy through a human accomplish? It certainly doesn't change the energy source.
"a human needs to be motivated in order to produce energy."
Historically, "ourselves" was equivalent to "members of a disfavored ethnic group and/or social class" and the "motivation" was provided by guys with swords, whips, pistols, etc.
I'd rather not see routine slavery/serfdom come back, thanks.
Handwaving doesn't count as "specifically addressing". Sorry.
The article's discussion of human power and incentives to use it beg the point to be made about the right way to fix the tragedy of the commons market failure with atmospheric pollution (and all the other problems with fossil fuels as well).
There are so many ways to reduce energy consumption that government regulation can't possibly legislate and adequately regulate (and it's barely even trying at the moment).
For example, I try to make a point to bike, walk, take the stairs, use efficient driving habits, and try to often take cold showers. I admittedly do this primarily because I like the exercise, the cold water is more refreshing and better for my skin, I save money, but as as an added bonus I feel some satisfaction that I consume less fossil fuels. But I would do all these things more if I saved more money from it.
And taxing bad things is better than taxing good things (like income and investment).
I think this is one of the things we will look back from the future and think, what were people thinking--they taxed jobs when they could have taxed something like environmental destruction? What?
But American politics are what they are. Our public transport across the country varies, but generally it is laughably bad, and that's just another example of an extremely low hanging fruit to grab.
So we see all governments going through loops and hoops to tax something bad, and at the same time regulate so that a sufficient amount of that bad thing still happens so they wouldn't lose the tax money.
Tax 'bad' thing, to pay for education about or mitigation of 'bad' thing. the feedback loop solves itself.
Actually, this would not always be true. Yes, in many cases would, but it would depend on the elasticity of supply and demand. The total size of the tax incidence would be government revenue from the tax.
The idea is not necessarily to outlaw carbon emissions, but to set a tax equal to the economic burden the emissions place on the global economy.
But a tax such as this should be designed to be revenue neutral--which we as humans are capable of doing.
Even though these things are possible, economic policy is so filled with politics, and politics is so filled with corruption, that I have little to no hope it will change.
Good writeup, but unfortunately in finnish.
(google translate) https://translate.googleusercontent.com/translate_c?depth=2&...
The best citation I have off hand is this https://anthropology.artsci.wustl.edu/courses/wucrsl/L48/361...
Plants absorb solar energy and store it as chemical energy. Animals roam far and wide to eat those plants, collecting the chemical energy in one place- themselves. Then human hunters come along and simply 'pick' the energy from the dense source that is the animal.
Now, the humans don't need to do much work because the energy is all in one place (they just need to find that one place). But the energy itself was collected over a huge area.
For beef it is more like 10-15% of the feed energy.
I guess the advantage is that you don't have to rely on nature and chance to get that food, since you literally create it from scratch.
It's still a plus to acquire just another added perspective on fuel yields for different types of human societies and lifestyles
This is also why reduced calorie intake is much more effective than increased activity if you want to lose weight.
Rick and Morty covered that in this episode.
Clever, but I'm guessing many will find this creepy or 'problematic'.
In this particular example, I certainly have no problem believing that it's true that among contemporary college-aged individuals from American and European cultural traditions, that on average the men would be more motivated to work out harder by the chance to see scantily clad women in a jacuzzi than the reverse. But that's extremely unlikely to be true for _all_ men or _all_ women. I would doubt that it's true for homosexual individuals. I would doubt that it's true for people raised in cultures that aren't so open to the display and ogling of near-naked humans, or contrariwise, cultures wherein the display of near-naked human form is not so sexualized.
This statement would be a cute aside between two people who share a similar cultural background. But in a semi-scientific article describing a utopian vision of power generation, it feels out of place to me.
From a global point of view, it's narrow-minded. The generalization given is not true of all cultures. From an individual point of view, generalizations about men and women who do share our culture tell us nothing about the individual in front of our face, who may or may not personally fit in with the profile. From a camaraderie-building point of view for residents of the building, making decisions about how to run the residents' responsibilities based on sexual objectification of other residents is probably not going to build a healthy local culture. And from a purely practical point of view, ignoring individual preferences and motivations is a great way to get substandard performance from everyone. Maybe the chance to see the girls in the jacuzzi would motivate the guys more than the girls, but I am betting it's unlikely to be the best strategy to get the best performance out of each individual man and woman.
The point is, it's a mistake to embrace these generalizations as universal truisms. They are anything but. And relying on them leads you to make poor and sometimes hurtful assumptions about other people.
And now you are complaining about people falling into an us-vs-then mentality while at simultaneously falling into an us-vs-them mentality yourself.
What I actually think is that current social justice thinking is as harmful as you seem to imply but that the way you are responding to it is literally just as bad.
We need an advance in our ways of thinking about this - not just un-thought-out reaction.
I would like to point out that what I said and what you said were different. I spoke of norms and tendencies, while you took a black-and-white approach. I agree that there needs to be a middle ground found. Extremists on both sides make progress difficult.
I'd like to point out that you have doubled down on the us-vs-them mentality.
Extremists are doing absolutely nothing to prevent you from coming up with a better way of looking at this problem.
No elderly or physically disabled students need apply.
By contrast, most US cities are well under 10%. Even LA, which has pretty excellent weather overall, is only at 4%: https://en.wikipedia.org/wiki/Modal_share
1. This is true of nearly all cities in the US, and
2. This feeds into my point about cultures favoring physical activity or not. LA's geography/weather is great for walking and biking. What holds it back are intentional design decisions borne out of culture.
The repeated "lets rape the sex bot again" scenes didn't help either. Funny how when she gets her revenge, that’s not described at all, just the aftermath. But we get page after page of lascivious detail on her abuse. Frankly, it left a really bad taste & I didn’t want to read anything by the author in question ever again.
also, James May tried to plug gym machinery to an electric car, the human output is just too low for electrical appliances - think not laptops, but washing machines, vacuum cleaners etc.
The modern food system is woefully inefficient at converting primary energy into food calories and the human body isn't all that great at it converting food into mechanical work. Useful amounts of heat are even more elusive. Toasting a slice of bread might take a half hour of vigorous exercise.
I'm pretty sure it would take more energy to heat a jacuzzi than one could extract from a dozen people showing off in front of it.
It's all converting from one form to another. In the case of "human power" it's extracting energy from plants and animals that we kill.
Wait but Why has an excellent deep dive on this: http://waitbutwhy.com/2015/06/how-tesla-will-change-your-lif...
On top of this, the premise is crazy. They want to have two societies: one that produces technology with non-human-generated power so the other society can use that technology to live on human-generated power.
If you think they're dreaming, I suggest reading it nor for engineering detail, but to try out their perspective. Most people would answer 'no,' leave it at that, and not reach some interesting perspectives they did.
Not that it goes into engineering detail, but for the creativity, thoughtfulness, and, most importantly, change in perspective from the predominant views of: we must produce more power! ... we must not change our way of looking at things!
I use my rowing machine regularly, which creates resistance through a fan and wind resistance. If it used a generator, I could power most of my apartment's electrical needs. Maybe not my refrigerator, which I shouldn't use when it's cold outside. Most of my electrical bill is fixed costs and taxes, not my electrical use, so a little less power and I could drop my contract. Articles like this one get me thinking that way.
If you keep extending how little you can use and what the world would be like if we had to work for our power instead of lazily flicking a switch and not caring about externalities, it's very interesting. Not to mention what it would do to our declining physical fitness, growing obesity, increasing disconnect from nature, and probably mental fitness too.
I bought a hand-powered washing machine a while ago and it did the job fine until it broke. Sadly, our culture doesn't promote great solutions that reduce consumption. I'd be happy to wash my clothes under my own power and other things like that if well-built ones were available. I can solve some things myself, but it's a lot easier when solutions are on sale. There are thousands of options for plug-in washing machines and only one or two hand or foot powered.
I'd love to see people engineer solutions that work and endure. This article isn't trying to solve all global power problems, but I bet its authors feel something like Stallman when he started writing GNU utilities, which people probably saw as tilting at windmills. Or even Torvalds writing the kernel, though Stallman's platform made his project more plausible to help. By the time people started Wikipedia, they could look back and build on several successful models. Or maybe like Feynman considering how much room there was at the bottom. Contemporaries probably said they were crazy and didn't see the point.
I, for one, support people thinking along these lines and seeing how far they can take us -- beyond engineering solutions to new ways of thinking about ourselves in the context of nature. I bet a lot further than most of us suspect.
I mean, I ask for no other reason than curiosity.
(Hey, you're the one that asked)