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Comment by mabbo | Hacker News Reader

This sort of system is used today in many modern industrial facilities. Case in point: Amazon warehouses.

Lots of the mechanical automations inside some of those warehouses are powered by compressed air in open loop systems. As the conveyor pushes the item off, onto a different lane, there's a distinct hiss of air escaping. The movement of the machine was powered by compressed air.

Out in the parking lot in these facilities, you'll see a huge compressed air tank (or many), constantly being refilled. Tubes from these go into the building like arteries in a body. Often inside the building there will be buffer tanks to help ensure constant pressure.

Source: worked for a few years with guys who maintained these systems. Some of what I learned may be wrong, so feel free to correct me.

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The common term is "pneumatics" and the components are prevalent in all automation and manufacturing. The air required is typically compressed on site.

Pneumatic actuators are relatively inexpensive, have a binary state that is easy to control, and offer a high power density.

How do they avoid bacteria/mould from growing in tanks and flocking the pipes and releasing in the room? Do such systems ever get cleaned up?

The air in industrial pneumatic systems is filtered and dried, which would prevent these issues.

Pneumatic systems often use small orifices and valves to control the air flow which would be quickly clogged by any debris, so cleanliness is important.

An aside: PID control was, back in the day, mostly implemented in pneumatic control systems (using a set of levers, bellows springs and nozzles). Pneumatic control systems were (and still are) used a LOT in industrial control systems where e.g. flammable environments where electrical equipment is too much of a risk.

https://control.com/textbook/closed-loop-control/pneumatic-p...

Mechanical, i.e. pneumatic, PID controllers were one of the most incredible things to learn about in university.

They aren't really the same types of systems.

Pneumatic "muscle pressure" is common in lots of industrial applications, especially those that operate in austere environments. But those are different than the tech being researched in the article in large part because the mechanical compressors in industrial applications are hugely inefficient. Many constant volume compressors have 90%+ of the energy as waste heat.

I believe the article is referencing isobaric (constant pressure) compressed air energy storage (CAES) that have much better efficiencies.

How does this work? How can you compress air without raising the pressure? Are you sure you don't mean adiabatic?

According to PV=nRT (ideal gas law), no you cannot in a closed system!!! But Hydrostor isn't violating any laws of physics -- they are simply capturing that heat so that it doesn't become waste heat!

Hydrostor has a thermal management system that captures the heat and stores is during compression. Then it reuses the heat when it is decompressing the air.[1]

This seem extremely promising as a much smaller footprint solution than pumped storage and much more sustainable and lower cost than any other energy storage solution. I just heard about them today, and I'm extremely impressed.

[1] https://www.youtube.com/watch?v=cOWjwwKSR78

That doesn't seem isobaric. Searching if it's possible, I've seen mentions of condensing working fluids, and bumby mentions ocean floor bags which seem like a good solution.

An external pressure (usually water) keeps it at a constant pressure.

Think of a bag of air under water on the ocean floor. The height of the water column is (relatively) constant, so the pressure in the bag is also constant. The air is being compressed as it goes from sea level into the bag, but inside the bag, the pressure is always the same. If you define the system boundary as the bag, it's an isobaric system. The volume changes, but the pressure is constant. Contrast that to the compressor you might have in your garage where the rigid tank provides a constant volume, but the internal pressure changes.

Oh I agree it's not quite the same as in the article. I was comparing to what the parent comment was saying about large pneumatic tube networks in ages past.

It is pretty common in regular workshops. Compressed air powers drills, riveting machines, sprays guns, jack hammers... Tools powered by compressed air are simpler (no electronics), more durable and cheaper.

My favourite thing about air tools was not having to worry about batteries (most electric hand tools I've used are battery only so no opportunity to use an extension lead like you use an air hose)

The motor also doesn't create sparks so they are more useful in flamable atmospheres.

Most electric hand tools are usually available for cheaper in a corded variety. The only electric hand tool I haven't seen come corded are impact drivers and most impact drivers I've used will last a day or two using it 8 hours a day even off a 2aH battery.

For me, I like air powered tools because of their power and reliability. They'll almost always have more torque and power than similar electric tools.

Air tools defintely don't have more torque than electric tools, they rely on speed to overcome their shortcomings in torque. The main high torque application in air tools is in impact wrenches, which use very fast hammering action. Modern battery impact wrenches can match the performance of the best air wrenches.

A top of the line M18 fuel impact (a $300 tool, before the $100 battery) is only equivalent with its air analog on the 1/365th of the year shop pressure runs at 90 because the OSHA guy is poking around and it's a heck of a lot bulkier.

When you start getting into 3/4 and 1" it's not even a comparison.

The cordless is nice to have but it's a luxury/convenience tool, not a replacement.

You forgot the most important reason they're used: they're far more powerful!

I saw a similar thing in a very old building, I think from the early 1900s.

The web of tubes was for messaging. (Just like some bank drive-ins work.) Users would put paper messages in capsules which were put into a pipe. Compressed air would carry the message to a central switching station, where human operators would re-route the message to the proper destination tube.

It was pretty cool, in a steam-punk sort of way.

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