An electricity-free oxygen concentrator

[Resnick]

Has anyone seen this project? http://freo2.org/siphon/

Seems a little too good to be true, but I don't know enough about the oxygen concentration process to comment. Any experts out there able to verify their claims? Here is a link to one of their papers:

https://link.springer.com/article/10.1007/BF03371464

The reason I ask is it recently won the Eureka prize for "Innovative Use of Technology". Also, it is a project running out of a big name University here in Melbourne, Australia.

[helius]

Oxygen concentrators use a cryogenic bulb to condense nitrogen out of the air, leaving greater relative concentration of oxygen. The condensation process can be enhanced using materials that adsorb gas molecules to their surface (like a sponge for gases). Typically the cryogenic system is powered by electric pumps, but pumps can be driven by other methods.



What the paper you cite proposes is to use rainwater to drive a vacuum pump. This has nothing to do with generating oxygen for sick children: as usual these types of proposals employ emotional images to hide substandard engineering.

Is rainwater used to drive vacuum pumps anywhere currently? What are the engineering problems to use rainwater as a vacuum pump? Do more efficient and practical ways perhaps exist to extract energy from rain?

[BradC]

What the paper you cite proposes is to use rainwater to drive a vacuum pump. This has nothing to do with generating oxygen for sick children: as usual these types of proposals employ emotional images to hide substandard engineering

Maybe you best go back and actually read the paper.

PSA oxygen generators are used in medicine all the time. They can generate Oxygen at sufficient concentration to be clinically effective and this is an extremely novel embodiment of the process. They are using a simple venturi (see edit below) to create "enough" vacuum that it can be converted to sufficient pressure to drive the PSA process. Effectively a low pressure vacuum driven compressor.

With the right zeolite and an optimized sieve bed what they are suggesting is perfectly viable. If they can come up with a novel way to keep the sieve bed dry (a considerable about of energy is expended in a conventional PSA cycle keeping the beds purged to release the moisture) they'll make a significant contribution to medial PSA technology.

edit: It's even better than a venturi. Using the siphon pressure differential to enhance the vacuum. That's *really* clever.

[helius]

I read as far as I needed to understand the technology being proposed. The design of a vacuum pump has nothing to do with concentrating oxygen. Vacuum pumps are used for a wide and diverse set of applications. Simple water aspirators, for example, are used in school science laboratories. None I am aware of use rainwater. I wonder why?

[BradC]

The design of a vacuum pump has nothing to do with concentrating oxygen. Vacuum pumps are used for a wide and diverse set of applications. Simple water aspirators, for example, are used in school science laboratories. None I am aware of use rainwater. I wonder why?

Because the method being proposed is slow and relatively weak compared to a water aspirator, but it *is* enough to drive a pump to develop pressure to run PSA process when no other source of energy is available.

[Resnick]

But can it really be as effective as reported? On their website it says:

"The team used the FREO2/SIPHON system to produce medical grade oxygen concentrations above 90%, sustaining the production of concentrated oxygen into the night."

It reminds me a bit of that self filling drink bottle that Dave debunked: https://www.treehugger.com/gadgets/fontus-solar-powered-bike-gadget-creates-water-out-of-air.html

[BradC]

But can it really be as effective as reported? On their website it says:

"The team used the FREO2/SIPHON system to produce medical grade oxygen concentrations above 90%, sustaining the production of concentrated oxygen into the night."

Absolutely. As long as they have a continuous flow of water they can produce a relatively steady vacuum. The vacuum drives a bellows based "pump" that generates enough pressure to run the PSA process. Remember, they are talking air at 90% oxygen content at 1/317 the flow rate of the water used to power the process. It's not fast by any stretch. I can buy an over the shoulder battery powered generator that makes that much oxygen at 90% purity.

You don't need a massive airflow to reach 90% purity. I got close to that on my patio table with some hacked together PVC fittings and a couple of E-bay solenoid valves. You need considerably more air for each % you try and get closer to pure however (and better zeolite).

They state the test system had 540Lpm of water flow, or 9L/s. That's a pretty good flow. Oxygen at 90% purity at 1.7Lpm requires about 4.2Lpm of air at *best*. Lets be generous and figure triple that, so 12.6Lpm or 210ml/s.

They are talking 5PSI (~4M head) and that's doable with the right zeolite (the stuff I have needs ~30PSI, but it was cheap).

So they are injecting .210L/s of air into a 9L/s water flow to get the vacuum. It's not unachievable. The best part is it scales. Got more water, put more siphons in and multiply your flow.

All in all, it's a pretty cool concept. Don't forget the vacuum doesn't have to be producing pressure on a 1:1 basis. The mechanical advantage can be used to optimise the delivery pressure for the PSA cycle at the expense of volume or vice versa.

[davepeake]

Hey everyone,

My name is David Peake and I'm one of the FREO2 team (you can see my ugly mug here: http://freo2.org/team) and I've been working with Bryn since the start, back when we were both Post-Docs and building these systems on the weekend and in spare hours.

Firstly it does work, we've generated 4 LPM of 92% oxygen using no electricity. This target was given as it's the same as the mid-range O2 concentrators found in medical centers. As guessed in the thread above, essentially the system is divided into two sections: the siphon which provides the vacuum flow and the custom VSA concentrator we've built. The VSA concentrator looks very similar to a PSA system you'd find in a standard concentrator but we use more selective zeolite, and instead of driving the system according to time, we've built a "pneumatic computer" which shifts through the solenoid states depending on pressures within the cylinders. Both of these let us wring a bit more efficiency out of the system.

The shift to vacuum is really the advantage here, it moves all moisture from the water away from the cylinders, it means the oxygen quality isn't dependent on the water quality and the N2/O2 isotherms (effectiveness of the zeolite) are steeper at the lower pressures.

As to the future, we've got a small grant from the Saving Lives at Birth (SLAB) collaboration to deploy it in Western Uganda (https://savinglivesatbirth.net/summaries/2016/502) and we're working towards making the system rugged now.

PS. I'm sorry the website doesn't have much on it; we're only a core team of four people, and the Siphon project is only one of a suite of solutions we're trying to develop for getting oxygen to kids. Web/Social etc comes pretty low on the priority list.