[olau]

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.

[Johnny555]

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.

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

[qqqwerty]

I 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.

[ASalazarMX]

You can't deny that it's borderline foolish to spend much more energy to build a device to save energy, even if you think it could be repurposed in the uncertain future. If we're going to be conscious about our (carbon/pollution/etc.) footprint in this planet, we have to make rational decisions about our consumption. It doesn't mean we can't have fun, we just have to waste less.

[cwkoss]

Energy isn't fungible though. It has a steep decay over time and space.

A watthour next to a hydroelectic powerplant has a very different value that a watthour in an off grid cabin during arctic winter.

Sometimes energy prices even go negative - it would be wonderful if these surpluses could effectively be utilized to manufacture solar.

[qqqwerty]

We are talking about a handful of hobbyists and tinkerers making DIY systems. If they substitute a weekend road trip with a weekend of tinkering with DIY power generation at home, the fuel savings would more than offset the embodied energy of the hardware in their project.

But if everyone on the planet started doing it, I might rethink my position.

[stefan_]

These calculations are all kinds of silly. No one should be exercising in the first place if you apply this kind of logic since humans are terribly inefficient (~25%) and the western food mix takes many many kJ to produce one kJ of nutrition.

[dwighttk]

> 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.

Large shifts like that don’t occur from people wasting money they have left over after entertaining themselves, they occur because the new way is much cheaper and the old way can’t compete.

[BizarroLand]

The current situation is like a fishhook with many barbs. You can't go back without ripping your skin to shreds, so even though it hurts almost as bad, to minimize damages you have to push forward, embedding more hooks into your already wounded skin, in order to get to the smooth part of the hook so you can push it out and be done with it.

Too many people get hung up on the idea of pulling out the hook (the current carbon-positive processes that we use) and not about the ultimately least painful and most successful way of removing the hook (pushing forward with pressure to transition to carbon-negative systems even if in the in-between time that causes more carbon to be released into the atmosphere)

We would generate a ton of carbon to build and roll out an EV replacement for every ICE vehicle on the planet, not to mention the extraordinary expenses of generating enough electricity and charging plants for them.

If that were done in an amazing single year by military force or something, it would be the year of the most carbon production ever on the planet.

But the centuries afterwards with the extraordinary reduction in Carbon Dioxides and Monoxides and other exhaust gasses would be worth it, right?

That's the plan, work over time, get better every day, little by little, don't worry about perfection, focus on drawing closer to good enough.

[mateo1]

From a simpler pov, assuming $50/MWh, biking super hard for 1 hour(100W) produces $0.005 of electricity.

Biking super hard for 16 hours a day for an entire year would produce $29 of electricity (assuming 100% efficiency in the generator and electronics).

And from an environmental standpoint, it would be better to idle on your couch while you burn the food you'd consume in an ICE.

[stavros]

> You'd likely never produce enough energy to offset the energy used to create the inverter.

Even if you did, the energy going into the bike isn't usually green. It's very, very far removed from the sun, especially if you eat lots of beef. Even if you don't, lots of gas was spent to get your food to your mouth, so you'd be much better off just not wasting the calories.

[SamBam]

This argument is only relevant if you weren't planning on exercising anyway.

If you were planning on exercising, any energy you feed back is completely "free," regardless of your food source (minus the embodied energy of the equipment you hook up, as above).

[stavros]

Yes, but if you were planning on exercising just to burn calories, just don't eat them in the first place.

[NathanielK]

Why? Exerting yourself and pumping out the watts forces your body to adapt to that and become stronger. Certainly better than being "efficient" and letting your body adapt to being sedentary.

[stavros]

Imagine eating French fries all day and then exercising to burn the calories. It would be better to not eat them in the first place.

[teaearlgraycold]

More in and more out is better than less in and less out.

[stavros]

Certainly not from an environmental standpoint, but why from an exercise standpoint?

[micromacrofoot]

Withering away and dying to stop global warming

[fluoridation]

I'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]

Yeah 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]

If 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]

I 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]

Internal 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.

[mardifoufs]

Some cheap lipo cells can get you a sweet 60-120C discharge rate with a pretty okay capacity. They are also widely available on the used market, usually sourced from EV batteries or energy storage packs. But yes, for the typical 18650/cylindrical li-ion battery, this wouldn't be especially feasible at all

[dahfizz]

The kettle used was vacuum insulated.

[wyager]

> 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-...

[dml2135]

Is less efficiency okay though if selling back to the grid results in more clean energy overall?

[fluoridation]

Not 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]

Or natural gas...which has disastrous methane emissions all throughout the supply chain

[vkou]

Depends 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.

[exDM69]

You 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.

[masklinn]

> 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]

While 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.

[Johnny555]

As 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.

[ourmandave]

I would personally prefer having an exercise bike plugged into the grid.

You could literally pedal bitcoins. ;)

[blacksmith_tb]

There 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/

[yongjik]

Your 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.

[WalterBright]

Think of all the CO2 you'll be exhaling from your exercise.

[TheSpiceIsLife]

Inverters 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-A...

[samatman]

Generating 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]

I certain the comment I replied to said something differ when I replied to it, see my reply to your sibling comment.

[explorigin]

200W 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.

[TheSpiceIsLife]

I 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.

[_carbyau_]

Inverter 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!

[rootusrootus]

A grid-tie inverter will be quite a lot more expensive.

[moltke]

I 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.