Way to generate energy in a closed system?

[Lucas38]

I’m looking to create a self sustaining ecosystem inside of a 4x2’ glass box that could be a totally closed system (with the exception of heat transfer, I can’t really prevent that). The idea is that I would bury it for a year and then dig it up again. In order for that to work I would need a way to generate enough electricity inside of the box to power a small led grow light, but I’m not aware of any way to do that. Is that even theoretically possible? I considered using a syphon to turn a small turbine but later learned that is impossible due to the way syphons work. Any help would be greatly appreciated!

 

[anorlunda]

The key parameter is the power consumption of the LED. If small enough, a battery might suffice.

You could also use induction to transfer external power wirelessly through the wall of the box while keeping the box sealed. Even that way, the power consumption of the LED is still the critical parameter.

 

[Tiran]

Have you considered perpetual motion?

 

[Tom.G]

but I’m not aware of any way to do that. Is that even theoretically possible?

No. There will have to be some outside energy source for continued activity, otherwise it is equivalent to a perpetual motion machine. We seem to get away with it here on Earth because our 'outside energy source' is the Sun. In you experiment the 'outside source' is the LED.

@anorlunda made some good suggestions to make energy available.

Cheers,
Tom

p.s.What are you trying to grow?

 

[Lucas38]

No. There will have to be some outside energy source for continued activity, otherwise it is equivalent to a perpetual motion machine. We seem to get away with it here on Earth because our 'outside energy source' is the Sun. In you experiment the 'outside source' is the LED.

@anorlunda made some good suggestions to make energy available.

Cheers,
Tom

p.s.What are you trying to grow?

That’s a bummer, but I suppose a battery would work. I was hoping there would be some way to generate energy inside of the box, so it could be fully self sustaining. I’m planning to grow some bromeliads and some other small plants. Thanks for the info!

 

[Lucas38]

The key parameter is the power consumption of the LED. If small enough, a battery might suffice.

You could also use induction to transfer external power wirelessly through the wall of the box while keeping the box sealed. Even that way, the power consumption of the LED is still the critical parameter.

Those are both good ideas, thanks!

 

[DaveC426913]

What is the ultimate goal of this?

Is the goal to create a closed system?
Or is the goal to grow plants without having direct access?

I mean, if there were a way to deliver power to the setup, would that directly violate your conditions?

Because, if you're literally trying to make a fully-self sustaining perpetual system, then you're out of luck.

But it depends on how rigorous you want to be.

 

[anorlunda]

Perpetual motion is a forbidden topic on PF. However, the OP clearly says:

for a year

That is very far from perpetual. In #5, the OP acknowledges:

I suppose a battery would work

So please, let's leave perpetual motion out of this thread.

 

[Rive]

It might worth noting at this point that the largest known 'closed loop' system (aka. Earth) still has external power supply (aka Sun).

Battery won't work for a year (at a power level required by any valuable experimental ecosystem, with reasonable size). Maybe something nuclear would.

 

[Tiran]

No closed system can "generate" energy - it has to start with all the energy it needs stored in some form: combustibles, trapped heat, electrical potential, radioactive material, food, etc.

You may be able to get colonies of aerobic and anaerobic bacteria to balance each other so one is "cleaning" the other's waste products well enough to last a year, but then your stored fuel/battery is whatever organic material they're eating - like yeast eating grape sugars in a wine bottle. But my gut sense is that photosynthesis actually takes quite a bit of light for something like a terrarium, and suitable long running batteries would be very, very expensive.

 

[Bystander]

https://en.wikipedia.org/wiki/Biosphere_2

 

[Tiran]

https://en.wikipedia.org/wiki/Biosphere_2

That is a closed system materials wise, but runs on outside solar energy.

 

[jim hardy]

I’m planning to grow some bromeliads and some other small plants.

I'd look at one of those light tube skylights.

 

[OmCheeto]

That is a closed system materials wise, but runs on outside solar energy.

Amongst other things: "An energy center on site provided electricity and heated and cooled water, employing natural gas and backup generators, ammonia chillers and water cooling towers." [ref: Bystander's link]

I would suggest growing mushrooms.

 

[Nik_2213]

May I suggest looking at some of the eg USGS geo-physics field instrumentation ? 'Alaskan' systems cannot rely on solar power or wind due lonnng, dark Arctic winter plus snow & ice accumulation. At least you don't have to worry about reduced battery output due to the chill...

Similar issues apply to Oceanography stuff, intended to eg log sea-bed conditions, then pop up after a year or two.

IIRC, pulsed LEDs are much more efficient than the 'regular' connection, so consider 'Joule Thief' circuits to eke out the supply.

( OT: Will your minimal LED(s) provide the correct spectral mix for your plants ? Have you done in-house runs to check viability ?? )

IIRC, high capacity primary batteries can prove exceedingly expensive-- Just ask a wildlife photographer...

Really Big 'Recreational' / Sealed Lead Acid accumulator ? IIRC, they have a significantly lower self-discharge than the 'Starter' variety.

Have you considered the 'micro fuel cell' designs now available ? Could be their waste water etc is little enough to be used by your eco-system...
--

PS: hopefully your plantings will be benign, not currently forbidden in your locale...

 

[some bloke]

Is the system somewhere secure EG your garden? if so, a solar panel could power the LED's (and accurately reflect the day/night cycle for the project).

Alternatively, a method for transferring sunlight into the system would bypass the LED's and electrical requirements entirely. perhaps a long, Perspex rod which extends from the roof of the box and protrudes from the ground? the sunlight hitting the face of the rod would reflect down it's length and into the box.