Gravity Based Electricity Generator

[kingamada]

Train them when they are young!

Now imagine we have like 20 of this slides, with a 10 meter height, but the getting back up isn't too steep, such that the animal might not easily get tired. 100 hundreds of cows lined up to be going down the slides. Which setup would you recommend though? to generate the most electricity

 

[kingamada]

Cattle don't walk further than they really have to.

Yes, that's why i was thinking of tiny levers in the field, such that by mere grazing in the farm, they would be generating electricity.

 

[berkeman]

Yes, that's why i was thinking of tiny levers in the field, such that by mere grazing in the farm, they would be generating electricity.

You could look at some of the ideas for generating electricity from people walking: https://www.pavegen.com/

Of course, with cows eating and pooping and drinking, keeping the conversion mechanisms clean and operating will be a challenge...

 

[russ_watters]

Which setup would you recommend though? to generate the most electricity

I have to emphasize again that the first step is always identifying how much energy/power is available. The problem with this ask is that you havent defined the scenario because you don't know what the animals can or are willing to do. That's not an engineering question so I'm not sure how much we can help.

I will say this though: we Yanks use horsepower as a unit of power for a reason: hundreds of years ago people put a lot of thought into how much power British animals can generate if properly motivated. There might be some modern or historical research on that.

 

[kingamada]

That's not an engineering question so I'm not sure how much we can help.

It's an engineering question because we're using animals weight to generate electricity, and we need to identify the right engineering setup (mechanical and electrical ) to harness the weight of the animal. The target is a 500kg per animal, we need to generate energy above 10kw. Since we're keen on using animal that means it has to do with gravity.

You could look at some of the ideas for generating electricity from people walking: https://www.pavegen.com/

Yes, actually it was pavegen that led me to think of harnessing animal weight instead of human, though pavegen is expensive and generates little power. That's why i'm here to gather help with from top engineers and physicists to get the best setup to generate the most electricity using mere animal weights.

 

[sophiecentaur]

Of course, with cows eating and pooping and drinking, keeping the conversion mechanisms clean and operating will be a challenge...

If you divert their internal energy chain, they will not put on as much weight. The economics of farming are subtle and, to put on the same amount of meat, you have to feed them for longer. It's certainly not an obvious win solution.
People will not be prepared to walk up a slope (or equivalent) just for the benefit of the nasty energy thief. They want escalators (or US equivalent).

Yanks use horsepower as a unit of power

That unit was chosen as a marketing ploy for selling steam farm machinery. 550ft lb /s (??) represents a pretty feeble horse, so I was told. But of course, horses get old and sick and you can put a tractor in a shed and forget about it for a few days. Bottom line was that steam won out.

 

[russ_watters]

It's an engineering question because we're using animals weight to generate electricity, and we need to identify the right engineering setup (mechanical and electrical ) to harness the weight of the animal. The target is a 500kg per animal, we need to generate energy above 10kw. Since we're keen on using animal that means it has to do with gravity.

That's an even worse insufficient specification than the OP gave. Just telling me I have an unspecified number of 500kg animals doing unspecified things tells me nothing about how much power/energy is available or how to harness it.

Here's the risk with engineers: we're creative and often have loose or missing screws, so if you constrain your problem insufficiently there is a decent chance the answer will involve a trebuchet.

 

[Averagesupernova]

Something tells me here that someone is literally trying to reinvent the wheel.
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My guess is the OP hasn't researched the history of what has been done to harness the energy that an animal can provide. So, to throw an old cliche out there, it's all been done.
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Now all that being said, the most sensible thing to do is to see if there are practical ways to combine that old technology with the latest. Battery technology has come a long way for instance. Charge batteries from the machinery hooked to the animal.
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Back in the days before electrical power transmission there were a number of ways power was generated. Wind was probably the most common typically used to pump well water. Solar was used to heat this water for bathing. A days sunlight on a tank provided enough warm water for comfortable bathing. Cloudy day? Well, suck it up and deal with cold water or going to bed feeling not-so-clean. Treadmills were common. Dogs were put to work on a treadmill that was rigged to run some sort of washing machine for instance.
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Here's a quick Google search. It's a start, using other phrases will reveal more interesting hits. https://www.google.com/search?q=hor...IBgGSBwMyLTKgB90F&sclient=mobile-gws-wiz-serp

 

[jrmichler]

I have to emphasize again that the first step is always identifying how much energy/power is available. The problem with this ask is that you havent defined the scenario because you don't know what the animals can or are willing to do.

Fortunately, somebody has done this:

That is the power that these animals will deliver over a normal work day under ideal conditions. Ideal conditions for most draft animals would be walking in a straight line on level ground that is soft enough to get traction and hard enough to not waste energy.

Stepping on power levers would be like walking on very soft sand. The power would be generated by pushing down against resistance with muscles evolved for pulling forward. The result would fatigue the animal while generating minimal power.

Animal power works best by pulling in a straight line, as in farm field work. Animals can also walk in circles while connected to a capstan. The image below shows a ten horse capstan drive:

And then there are the conversion losses. Converting pulling power into lifting a weight will have friction losses. The potential energy added to the weight will be less than the power delivered by the animal. There will be further friction losses as the weight drops. The generator has inertia, so takes more energy to spin it up. A 10 kW generator might be 80% efficient, so 20% of the power turning the generator shaft will be lost as heat. There are standby losses because animals keep eating on their days off. With additional power losses to remove and dispose of manure. And don't forget that controlling the that animal is a full time job for a human.

When all of the losses are added up, the useful power delivered to a load will be less than 10% of the power delivered by the animal. Animal power can be effective when used directly, as in pulling farm equipment. But not when used to lift a weight to generate electricity to drive that load. In that case, the human could drive the load directly using pedal power, and eliminate the horse.

 

[Averagesupernova]

In that case, the human could drive the load directly using pedal power, and eliminate the horse.

Depends on the load of course. I would say back in the day all of the energy used by a machine that was powered by horses utilized it at the moment the horse pulled the load. No storage. Energy storage in those days consisted of stock piling the product whether it was water (pumped by wind power), firewood (hauled by horses, likely sawed by humans), grain or hay for feed (again, hauled by horses).

 

[Ripcrow]

Thank you so much, you really did grasp my idea. Maybe I didn't ask the right questions, as you know sometimes it's about the quality of the question. Though I'm still trying to see how mechanical advantage does not alter the amount of power. Before we answer that, let me see if this rephrasing of my question will lead to a helpful answer and guide. Let's say I have a motor that has the below specification

MMA size (shaft height, mm)	Rated Speed, rpm	Max Speed, rpm	Rated Power, kW	Rated Torque, N•m	Peak Torque, N•m
SH80	580…2600	1400…6000	0.6…8.6	10.5…31.5	21…88
SH100	580…2600	1400…6000	2.3…21.1	35.6…94.6	80…200
SH132	580…2600	1400…6000	6.4…48.4	90.7…217	200…400

If we attach 500kg of weight to the pulley weight to each of the motor and we attach a pulley with multiplying gears such that each rotation of the pulley in 2 seconds results to 100 rotation of the motor, which would translate to 30 rotation = 3,000 rpm. Now knowing the rpm, power output of the motor, peak torque and the height is 5 meters. Wouldn't it produce it produce the rated power as it's coming down?

Gearing changes how power is delivered but it doesn’t change the amount of total energy that can be extracted from the system.

 

[Ripcrow]

Yes, that's why i was thinking of tiny levers in the field, such that by mere grazing in the farm, they would be generating electricity.

A hard surface means less energy is required by the animal. I’m not sure of the amount of depression ( how much higher the animals would have to lift their feet off the ground ) the animals would experience in a fields that moved under their feet ( think of walking on a soft lawn verse walking on a hard grass surface ). The extra energy required by the animals to move might be more than they can generate. You can’t get anything for free.

 

[sophiecentaur]

A hard surface means less energy is required by the animal. I’m not sure of the amount of depression ( how much higher the animals would have to lift their feet off the ground ) the animals would experience in a fields that moved under their feet ( think of walking on a soft lawn verse walking on a hard grass surface ). The extra energy required by the animals to move might be more than they can generate. You can’t get anything for free.

By effectively putting yourself in the animal's place you have successfully revealed the nonsense of the scheme. Just imagine the cost of a field full of "little levers" and the maintenance involved. I fear that the OP has never been made aware of the TNSTAAFL principle.
Skinny cows are not very marketable.

 

[kingamada]

You can’t get anything for free.

No one is requesting anything for free, or trying to get free energy. Even the solar requires capital investment, maintenance, and all sort. We're looking for a cheaper alternative with minimal inputs but higher output. I feel like there is energy there that is left untapped.

 

[jrmichler]

After 74 posts, about 20 of which discuss the physics of energy conversion, I will summarize the physics of energy conversion:

First law of physics: You can't win.
Second law of physics: You can't even break even.
Third law of physics: You can't get out of the game.

All energy conversion systems, with no exceptions, require more total energy IN than get total energy OUT. That's the first law of physics. The second law of physics states that it is never possible to get out as much as you put in. There is no such thing as a zero friction, 100% efficient machine. And the third law states that there is no way around the first two laws.

looking for a cheaper alternative with minimal inputs but higher output.

This is perpetual motion (PMM) or free energy, both of which are specifically not allowed at PF. Therefore, this thread is closed.