Comment by Johnny555 | Hacker News Reader

Comment by Johnny555 | Hacker News Reader

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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

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.

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.

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.

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.

> 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.

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.

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.

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.

> 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.

Withering away and dying to stop global warming

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).

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

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

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

Humans evolved to move around a lot. Avoiding exercise to save food will lead to a host of ailments. Sarcopenia is a hidden epidemic among older people in developed countries.

But we aren't talking about avoiding exercise, we're specifically talking about exercise as a way to burn calories.

Depending on what you eat you could still be well below the average environmental impact of a resident of an industrial nation. If you're vegan/vegetarian then 4000 calories a day from beans would be far less impactful than a 2000 calorie diet of meat.

Fit people need to eat more. Muscle takes calories to maintain. You can't maintain muscles without exercise. Your body expects that you're running down prey on a periodic basis. If you don't meet those expectations not everything will work as it should.

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.

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.

Imagine thinking that human bodies are CICO machines with no other function or utility

Imagine not being able to comprehend the sentence "if you were planning on exercising just to burn calories, just don't eat them in the first place."

Imagine continuing the argument when you've been repeatedly, definitively, and elaborately told you're missing the point

Yes, apparently I'm missing the point I made myself.

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