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Converting human energy and storing it

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  • #16
    Originally posted by SLK001 View Post
    At rest, a human body gives off approximately 100W of heat energy. Making them work, they can sustain a rate of about 1/6th of a horsepower, or about 125W. Assuming 100% conversion rate, that gives you about one small light and a small laptop. To get any meaningful amount of energy from humans means that you have to have a lot of them

    Thanks to modern advances, 125 watts does a lot more than it used to. For instance, a single 3 watt LED can provide sufficient light to illuminate a living area. When used for a task light a 3 watt LED (with a focusing mechanism such as optics or reflector) can nicely illuminate the area for reading, cooking, repairing things. As for that laptop... New micro computers like the Raspberry Pi use less than 10 watts and are quite capable for most common uses. Match that with a small led screen and it's amazing how little energy it uses.

    In essence, if you can gather and store 100 watts an hour for most of the day you can live a modern (although restricted) lifestyle.

    Dan
    At the end of the project, there is a profound difference between spare parts and extra parts.

    Location: SF East Bay.

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    • #17
      Originally posted by danlb View Post


      Thanks to modern advances, 125 watts does a lot more than it used to. For instance, a single 3 watt LED can provide sufficient light to illuminate a living area. When used for a task light a 3 watt LED (with a focusing mechanism such as optics or reflector) can nicely illuminate the area for reading, cooking, repairing things. As for that laptop... New micro computers like the Raspberry Pi use less than 10 watts and are quite capable for most common uses. Match that with a small led screen and it's amazing how little energy it uses.

      In essence, if you can gather and store 100 watts an hour for most of the day you can live a modern (although restricted) lifestyle.

      Dan
      Even modern laptops are amazingly energy efficient. No need to struggle with Rasperry Pi and tiny screen when 13" ultrabooks manage 10-12hour runtime on battery. Dell XPS for example 52Wh and 12hours = about 4 watts!
      5 minutes at 400 watts would be 33Wh so one high-intensity exercise would power modern laptop for 10 hours.

      For long treks in wilderness a small human-powered generator would be better than carrying batteries. Human body is about 30% efficient in producing mechanical energy and if fueled by mostly fats. 1kg of body fat would be ~2400Wh of energy out of generator assuming 30% metabolic efficiency and 90% generator efficiency. That is same amount of energy as five large e-bike batteries or 40 laptop batteries.
      Location: Helsinki, Finland, Europe

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      • #18
        Might have been Expo 86, don't recall, but somewhere there was a pedal machine where you could read the amount of energy you were giving off. I got on it and reached a peak at about 800 watts for a few seconds. It was a chore to maintain 200 watts, and I think I only got about 30 seconds at that rate. There's certainly nothing practical about it if you're trying to offset your electric bill. You might make what- one dollars worth of electricity in a month?
        I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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        • #19
          Given the low output of our own efforts I'd suggest that the best way to store human power is to "bank our power output" towards building a solar collector array that we can then lounge below in shady comfort with a nice suitable summer time drink. The human calories used in terms of effort needed to work to pay for the panels and support structure and work directly towards installing said structure will pay back many times over in terms of power produced and saved in some sort of storage batteries. Power that can then be used for powering LED lights and other low voltage operation tools or implements of entertainment.

          As noted we hoomans totally suck when it comes to being mechanical energy producers. 125watts for a reasonable time from a body in reasonable shape. And competition cyclists appear to be able to produce around 250 to 300 watts for reasonable periods. And peaks of up in the high 300's or low 400's during short term sprints of 5 to 10 minutes. At least that's what I'm seeing with a short and sweet search on the topic.

          So I come back to how I think it's reasonable to suggest that our best use of our energy is as a "seed" input to build something that will capture and convert some other source of energy that is otherwise going to waste. Years ago it was building a water wheel on a creek or a dam with water wheel. Then use it to grind grain which was otherwise done by hooman or animal power. These days the trend is to storing electrical power.

          If you're simply tired of seeing your heartbeats go to waste then from the perspective of home shop machining I'd suggest simply take a cue from some of the musicians and "go unplugged". Cut your metal with a hacksaw. Find and restore an old hand power post drill. Convert the lathe to treadle power. Box up and sell off all the power grinders and buy a nice assortment of cold chisels and good files. And in among the rest set up a proper blacksmithing forge so you can hammer the metal roughly to shape before using those other tools. Just like they did before we had electrical power.

          Chilliwack BC, Canada

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          • #20
            Originally posted by CCWKen View Post
            wheeeeew. Man, I'm exhausted just reading all this. I'm reminded of a movie/cartoon where everybody is riding around on floating easy-chairs on a spaceship. They had to leave Earth due to all the garbage piling up everywhere. Please don't invent and add to the garbage. I like it here.
            Wall-E, a nice movie.

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            • #21
              Maybe have kids. They stored up all your energy and they spend it all in their first 10 yrs or so. Make em mow the lawn.

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              • #22
                Originally posted by BCRider View Post
                As noted we hoomans totally suck when it comes to being mechanical energy producers. 125watts for a reasonable time from a body in reasonable shape. And competition cyclists appear to be able to produce around 250 to 300 watts for reasonable periods. And peaks of up in the high 300's or low 400's during short term sprints of 5 to 10 minutes. At least that's what I'm seeing with a short and sweet search on the topic.
                Yeah, pretty reasonable numbers. I can do:

                348 watts for 5 min
                311 watts for 10 min
                288 watts for 30 min
                275 watts for 60 min
                200+ watts for 5+ hours

                A lot of the guys I ride with can eclipse those numbers.

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                • #23
                  Originally posted by tomato coupe View Post
                  Yeah, pretty reasonable numbers. I can do:

                  348 watts for 5 min
                  311 watts for 10 min
                  288 watts for 30 min
                  275 watts for 60 min
                  200+ watts for 5+ hours

                  A lot of the guys I ride with can eclipse those numbers.
                  Many years ago I was into mountain biking when it first appeared on the scene. I remember avidly following the Tour de France at the time, and some of the news casters had a panel discussion with some team physicians about how much can a top cyclist put out? Answer is basically about 1/3 HP all day long, short bursts of almost 1 HP -- but this is far far beyond average human performance.

                  As for myself, I was content with a couple hundred miles a week on flat land.

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                  • #24
                    Originally posted by nickel-city-fab View Post
                    Many years ago I was into mountain biking when it first appeared on the scene. I remember avidly following the Tour de France at the time, and some of the news casters had a panel discussion with some team physicians about how much can a top cyclist put out? Answer is basically about 1/3 HP all day long, short bursts of almost 1 HP -- but this is far far beyond average human performance.
                    1/3 HP all day is pretty difficult, but 1 HP in a short burst is doable by many recreational cyclists. Serious cyclists are in the 1.5-2 HP range for short bursts, and track cyclists can reach 3 HP.

                    A big difference between ordinary cyclists and professional cyclists is not the power they produce, but their power-to-weight ratio.

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                    • #25
                      I mean, you could mess about with a clever system of clutches and springs to try to store kinetic energy, or you could hook an alternator up to a bike wheel and use it to charge a Li-on power bank. Li-ons lose very little power, have an insanely high energy density when compared to a spring, and i cant think of very many times where id rather have stored kinetic energy, instead of just electricity

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                      • #26
                        A number of aid agencies donated bicycle powered water pumps to poor African comunities. They actually worked quite well, and when one child got tired there was a whole bunch to take over. A similar system is also used in poor rural areas in India. I even saw a large grinding wheel power by a bicycle for sharpening farming tools, car altenator used to charge a car battery (for charging cell phones and LED lamps), an air compressor and a washing machine!

                        Keep in mind these are very poor communities compared to western standards, they have very little resources and no electricity but unlimited numbers of kids that will pedal a bike for entertainment, so even if the power output is low, there is always someone pedalling.

                        There was a design flaw though. Because they used of-the-shelve bikes, the pump bikes were quickly stolen and converted back to a normal bike.

                        There is a video on youtube of a pedal powered ultra light plane that actually flew a short distance.

                        I think the OP has a sound idea in principle. If you connect a type of generator to each excercise bike in a gym/spinning class, you would create a useable but very erratic power supply. 20 excercise bikes at 200w gives a respectable 4kw. Setting up a system with batteries and inverters to make the power useable will make it expensive and I don't believe enough power will realistically be generated to recover the expence. Will make a good "green power" advertisement for a gym though! Now, if we could only find a way to harnas energy from the manly art of drinking beer....

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                        • #27
                          We've evolved a lot of things based on electricity, and with our modern electronics becoming more efficient, the power requirements are low enough that a person could keep it alive based on muscle power alone. But how far do you take the idea (muscle powered electricity) before it becomes ludicrous. I can't recall the last time I had a power outage where I just HAD to have power right now. A flashlight or two, that's about it.

                          The whole idea of being able to keep your personal electronics alive pretty much suggests that you'd be carrying the man-powered generation and storage device with you most of the time. It becomes a different animal then. If you don't have a jacket with a battery pack sewn into it, covered with solar cells, or a head-mounted wind turbine- what form will the generator take? The squeeze flashlight ? No it has to be better than that- and what kind of battery capacity would you want to carry?

                          Or- maybe you'd just want to make sure you brought enough beer-
                          Last edited by darryl; 08-04-2020, 03:42 AM.
                          I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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                          • #28
                            Modern electronics... I just picked up an Asus G14 gaming laptop computer. It's the size of a small Chromebook but has an AMD Ryzen 4000 series CPU and a Nvidia GTX2060 video card. It's as fast or even faster than my gaming desktop, will surf the web all day for 10 hours on a charge, and when I want it to, plug in my VR headset for VR gaming. With the power brick, it's less than 5 lbs. Plenty of reviews on YouTube, impossible to find a negative one. It just blows my mind, the performance it has in a small package
                            And oh yeah, runs Fusion and Solidworks like a boss.
                            The 14" screen is small for such tasks but that's why I have an HDMI cable on hand. Every hotel now has decent flatscreens.

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                            • #29
                              Originally posted by tomato coupe View Post
                              1/3 HP all day is pretty difficult, but 1 HP in a short burst is doable by many recreational cyclists. Serious cyclists are in the 1.5-2 HP range for short bursts, and track cyclists can reach 3 HP.

                              A big difference between ordinary cyclists and professional cyclists is not the power they produce, but their power-to-weight ratio.
                              And the shift in muscle mass to the legs. Major legs on all the top competition cyclists. Good all over but major size legs.

                              I'm ashamed to admit that I don't ride as often as I should since retiring. It led to me being in pretty good shape when I commuted by bicycle all but a very few times a month and even ran many of my errands by bike.

                              It's a bit more of an expedition now though. I'm 330 ft up a hill now and about 3km from the nearest part of town with stores. I still try to get in a couple of rides a week but it's not the same. And I gave up riding in all weather too. I rode to work in some rather biblical condition storms a couple of times back in the day....
                              Chilliwack BC, Canada

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                              • #30
                                The pyramids and great cathedrals were built with just human power. Generating and storing energy as electricity is the most inefficient form unless you need it in that form. That bike powered water pump would have done almost nothing if electricity was used as an intermediate step.
                                When thnking of your laptop battery requirement you have all forgottn the need for modem - nowadays an essential part of the kit and energy hungry unlike the old dial up modem built into the earlier laptops.
                                Those bike powered knife grinders were commonplace in most towns until WW2.

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