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I was curious whether they talked about the practicality of the whole setup, and they do, e.g. > Electric kettles that run on grid power are often very powerfu
by olau 5y ago
I was curious whether they talked about the practicality of the whole setup, and they do, e.g.
> Electric kettles that run on grid power are often very powerful and boil water in a matter of minutes or even seconds. Boiling water using a bicycle generator will take a lot more time, but it’s perfectly possible. We acquired a commercial 12V electric kettle with a vacuum insulated reservoir of one litre. During a test, boiling water for one cup of tea took slightly more than one hour at an average power production of 60W.
To be honest, although I realize it would be ridiculous, but if inverters were small and cheap, I would personally prefer having an exercise bike plugged into the grid. That way my exercise energy would at least be useful to someone, somewhere.
- TheSpiceIsLife 5y agoInverters are tiny and cost almost nothing. Here's one for under $50 that will do what you want: https://www.ebay.com.au/itm/Car-Power-Inverter-12V-to-240V-AC-Converter-200W-With-4USB-Phone-Charger-AU-/193941414985 https://www.ebay.com.au/itm/Car-Power-Inverter-12V-to-240V-A...
- rootusrootus 5y agoA grid-tie inverter will be quite a lot more expensive.
- explorigin 5y ago200W isn't a lot of power. Most microwaves are 1KW. You'll need an inverter that can do that at least to run a fridge constantly and a microwave periodically.
- _carbyau_ 5y agoInverter is not a battery so it is translating the useful work from the human directly. I am imagining a 1kW sprint run by Uni students for microwaved ramen noodles!
- TheSpiceIsLife 5y agoI swear the comment I replied to said: "would personally prefer having an exercise bike plugged into the TV..." When I replied to it. However, I have no proof and am often wrong.
- samatman 5y agoGenerating a dirty sine wave which will power an appliance is fine, but that's not the goal here. The goal is to generate a clean sine wave which will benefit the grid when applied to it. This is probably impossible at bike workloads, and is in any case quite a bit more of a problem than just throwing an inverter at a DC source and calling it done.
- TheSpiceIsLife 5y agoI certain the comment I replied to said something differ when I replied to it, see my reply to your sibling comment.
- fluoridation 5y agoI'm surprised they even got it to boil. I would have expected the heat to escape faster than it's added before reaching the boiling point. That aside, 60 W * 3600 s = 216 kJ. With ideal thermal insulation, that would be enough to boil about 600 ml of water. If they only managed to boil enough for a single cup (~300 ml), that's a rather inefficient setup they're using.
- pitaj 5y agoYeah I'd suspect slowly charging up a battery with the bike generator and then quickly discharging the battery to boil the water would be quite a bit more efficient.
- dylan604 5y agoIf it takes an hour to charge the battery or an hour to boil the water, it still takes an hour. Based on the previous comment of generating 60W, how much battery charging will that do? I'm really asking as I don't have the info at hand to do the maths. I'm assuming choice of battery comes into play.
- foxyv 5y agoI think that what they are saying is, if we remove the heat losses from the 1 hour boiling time and instead boil it in a burst of 5 minutes using a battery you would need significantly less energy overall. As a result, using a battery instead of directly utilizing the bicycle's electricity, would take significantly less time.
- KennyBlanken 5y agoInternal resistance of the battery would be a significant problem, you'd need a fairly sizeable battery, and most lithium ion cells have a maximum discharge rate of around 1-5C unless they're high-discharge-rate cells which are usually more expensive and lower capacity. Using a vacuum flask would dramatically lower heat loss.
- 5y ago
- wyager 5y ago> That way my exercise energy would at least be useful to someone, somewhere What very few people (who haven't worked on grid modeling) realize is that injecting energy into the grid from random locations tends to make operating grids harder and more expensive, rather than making it easier by reducing load. This applies to everything from bikes (which on balance won't really make any detectable difference, and certainly won't ever make an economically positive contribution vs the cost of hooking them up) to home solar panels. Getting paid grid rates to dump extra solar energy back into the grid is actually a (very inefficient) subsidy benefitting solar panel owners. If the grid charges you fixed 10c/kWh for power, and has to pay you 10c/kWh when you dump solar surplus onto them, they're almost certainly losing money on you, and it's probably making the grid less efficient. Here's a good starting point if anyone is curious why grid-dumping isn't socially efficient. Once you understand how socially efficient power pricing works (e.g. LMP pricing), it's pretty straightforward. https://www.eba-net.org/assets/1/6/6._[Savitski][Final][165-208].pdf https://www.eba-net.org/assets/1/6/6._[Savitski][Final][165-...
- dml2135 5y agoIs less efficiency okay though if selling back to the grid results in more clean energy overall?
- vkou 5y agoDepends on what the trade-off is. If that efficiency would have gone to shareholders, sure. If that efficiency would have gone towards building utility-scale renewables, no.
- fluoridation 5y agoNot if the added inefficiency totally consumes the added clean energy and needs further non-clean energy to sustain it. You could end up in a situation where taking energy from residential solar panels leads to burning more coal than if you hadn't done anything.
- mcronce 5y ago
- masklinn 5y ago> To be honest, although I realize it would be ridiculous, but if inverters were small and cheap, I would personally prefer having an exercise bike plugged into the grid. That way my exercise energy would at least be useful to someone, somewhere. The only thing it would do is fuck up the grid. Grids are not sewers, they don’t work by having randos throw shit into it. Human power is way too low and unreliable to be of any non-hyperlocal use.
- rruark 5y agoWhile impractical and not cost effective, having a bunch of bikes connected to the grid and randomly producing power would have no more of an impact on the grid than flicking a 60W light bulb on and off.
- deleted 5y ago[deleted]
- Johnny555 5y agoAs long as he uses a proper grid-tie inverter, there's no reason the grid couldn't absorb his excess energy. It wouldn't be cost effective for him, though.
- exDM69 5y agoYou can power a smartphone or a flashlight for a very long time with the energy it takes to boil a liter of water. The latter is easy to do with firewood but charging batteries is not.
- moltke 5y agoI think you'd be better off plugging it into a kettle or coffee maker. At one hour per cup that sounds like good exercise and having a goal sounds like good motivation.
- yongjik 5y agoYour exercise is already useful to you (and those around you): it keeps you healthier and reduces future medical cost expected by the society. It sounds like a fun project, so I'm not arguing against that, but I don't expect it to "help the Earth" in any meaningful way. Considering the fossil fuel usage by modern agriculture (and all the energy spent on delivering the food to our mouths), the net climate impact of using "human energy" is probably worse than an electric kettle.
- Johnny555 5y agobut if inverters were small and cheap, I would personally prefer having an exercise bike plugged into the grid. That way my exercise energy would at least be useful to someone, somewhere. You'd likely never produce enough energy to offset the energy used to create the inverter. Just to come up with a rough estimate, if the bicycle grid-tie inverter cost $200, and 25% of that cost is due to energy @ $0.10/Kwh, that's 500KwH of energy wrapped up in that inverter. If you produce an average of 100W while biking, that's 5000 hours of biking, or about 10 years of biking 10 hours a week. It might be more practical if you could harness all of the bikes in a busy gym where you could get hundreds of bike-hours of energy a day. (Ok, I made some pretty big assumptions here. First, I don't know how much energy goes into making a product or how much it costs, and it's not all electricity, there's diesel and natrual gas in mining and processing raw materials, etc). (Edit: my guess is probably not too far off, a typical phone in 2008 had around 180MJ/50Kwh of embodied energy [1], so 10X that amount for a 10 or 20 pound grid-tie inverter might be in the right ballpark. Aluminum alone has around 200MJ/kg embodied energy so a 2 pound heat sink would account for around 50KWh of the embodied energy of the device) [1] https://www.lowtechmagazine.com/2008/02/the-right-to-35.html https://www.lowtechmagazine.com/2008/02/the-right-to-35.html
- qqqwerty 5y agoI have a philosophical issue with the embodied energy critiques. Primarily, it is that individuals who are trying to push the world in a carbon free direction would also likely prefer that the goods that they consume also be manufactured using carbon free energy. In essence it feels like they are taking the blame for decisions made by our predecessors when they are the ones trying to fix those bad decisions. In a sense, the blame for the embodied energy belongs to the previous generation that chose to use carbon based energy, with the exception for individuals who are advocating for the status quo. In that case, they should be accountable for it (not that they would care anyways). Additionally, these analyses rarely take into account positive second order effects. For example if someone puts solar panels on a northern facing roof in Canada, they are unlikely to ever realize a breakeven point, and the project might not offset the embodied energy of the system (and associated emissions). But that purchase means more revenues and jobs for the solar industry. And in turn that means more investment and more economies of scale. Basically, if we want to transition to a carbon neutral world, it is going to require a lot of people investing/purchasing projects/goods that do not make sense economically and might not initially be carbon neutral after accounting for embodied energy. Without early supporters we can only rely on government subsidies (which we already do, but obviously not enough). I personally don't think the free market can solve climate change, but if it is going to have a chance, we are going to need a lot of people to make these types of purchases/investments. Also, another thing to consider is that the inverters lifetime is going to be directly correlated to the operating hours. So if the OP wants to hook up his exercise bike to the grid (assuming it is legal in their area), and then down the road decides to get some solar panels, that inverter will work perfectly fine for that purpose and have minimal degradation.
- WalterBright 5y agoThink of all the CO2 you'll be exhaling from your exercise.
- blacksmith_tb 5y agoThere are commercially-available exercise bikes etc. that have inverters built in[1], though they're marketed to gyms who want to buy a fleet of them it looks like. I am skeptical it'd be practical, but it might not be a terrible idea if you were buying your first machine (and not replacing a perfectly good existing one). 1: https://www.gosportsart.com/product/g516-indoor-cycle/ https://www.gosportsart.com/product/g516-indoor-cycle/
- ourmandave 5y agoI would personally prefer having an exercise bike plugged into the grid. You could literally pedal bitcoins. ;)