Ditch the Batteries: Off-Grid Compressed Air Energy Storage (2018)
lowtechmagazine.com
lowtechmagazine.com
https://www.cottagecraftworks.com/home-goods/self-sufficient...
You can also do something similar with the fridge where it turns off the ice maker and the auto door light.
I share in your fascination of these kinds of workarounds.
Someone help me understand why some folks treat this stuff like a tax loophole.
The rules come from God because Jews consider themselves a chosen people. They don't particularly want you to follow those rules or concern yourself with the mechanics of them, because they're not about you. The fact that it doesn't make sense is perfectly fine.
Interpreting those rules in a modern context is every bit as arcane and arbitrary as the rules were in the first place. The important part is that they come to a conclusion and follow them together. That cements the society as a group.
It doesn't really matter what God thinks, either. If God had a contrary opinion, He'd say so. There is, for that matter, a famous story about rabbis coming to a conclusion that God explicitly sends messages against, but is pleased that they have used their reason.
The Jews put a lot more weight on community and a lot less on trying to please their deity by following the rules. It just so happens that the rules really are both things.
I vaguely know some Mennonites. One guy has a cell phone and car transmission repair businesses, and computers, but he only uses those things for certain tasks and does not keep the technology in his home. He uses it at work. He locks up his phone and pc when not using them for work.
Not that this guy is representative or anything, just an anecdote. Neither group is homogeneous, and I don’t mean to single anyone out.
The different approaches to technology, and the varied applications of technology, in service both to secular and sacred ends is interesting to me.
I believe some also had mechanical windmills, though none for electrical generation. The area wasn't suitable for waterwheels- if it was, I suspect they may have forgone the diesel engine.
This group also had single landline phone in the community, in someone's yard nearish the road. They used it for the rare cases where letters weren't practical- things like calling a doctor, etc.
Keep in mind, the limitations are based on how a thing affects your relationship with God and each other. Buttons on clothes, for example, weren't a thing; they were seen as a vanity (often too decorative). Instead, safety pins were the norm. As such, technology isn't banned for being technology, but as part of a larger category of things that draw you away from devotion- be it pride, vanity, etc.
What concerns the Amish is being too dependent on the outside world. Tying to the regional electrical grid would make them too dependent.
They aren't isolationists, though. They will still buy from and sell to outsiders. Using things like gasoline or diesel generators to power air compressors is OK because it isn't seen as requiring becoming too closely tied. Probably because if their gasoline supplier becomes unreliable, they can buy from someone else.
In general, the Amish avoidance of technology is greatly overstated. They don't so much avoid it as take a very cautious approach, making sure they know how it will impact their society before they let it in.
They have a few people try it out, while the rest observe how it goes, and they watch how the outside world handles it. Only when they understand what changes it will bring, good and bad, do they decide if they are going to adopt it or skip it.
They are kind of like where the rest of us were 20-50 years ago (it varies depending on the particular technology) except they are avoiding the mistakes we were making back then when we were rushing to embrace the latest stuff.
In a few decades, there will probably be Amish equivalents of Facebook and Twitter but without being full of trolling and misinformation, because the Amish will wait for us to figure out how to control that before they make their versions.
Here's a good article on Amish and technology [1].
Quote: "Ivan is an Amish alpha-geek. He is always the first to try a new gadget or technique. He gets in his head that the new flowbitzmodulator would be really useful."
flowbitzmodulator!! That's my new word for this week...my wife's going to kill me
The force and energy available through natural physical processes is under rated some times...
Well...I guess all our power and energy is based on natural processes.
Hmmm...I guess...there's some natural physical processes that tend to get largely overlooked that provide more energy than one might think is I guess what I mean.
An electrical battery, even if it stores the same amount of energy, is seriously more power-strapped.
Of course you have to mitigate moisture, but that is trivially solved with a moisture trap on the compressor's outlet or at the tool if you're using long air lines.
The very good idea of floating solar panels on a reservoir (cool panels are more efficient, and keeping them clean is cheap!) raises the question of what to do with excess power generated in the daytime. One alternative would be to pump water up out of another reservoir downstream, but there might not be one. So, just put a big air bladder on the bottom of the reservoir and pump air in.
Same applies for offshore wind power.
About half the energy you put into a pressure vessel becomes heat that you would not get back, under water. (But rock is an excellent insulator.) With enough spare water, you can draw almost the same amount of heat back in on discharge. Or, you might have a use for cold air.
An electro-chemical hydrogen conversion and compression vessel would have far more points of failure with far greater technical barriers to repair. The access to specialized spares in a remote location would also be a major issue.
I am not saying it cannot become a player in energy storage to eliminate the need for coal and natural gas energy generation. But it seems unlikely that would be a good choice for remote 'off-grid' location.
My brother has a steep hill on his property and Ive been wondering about the feasibility of PSH. How high the tank should be, the equipment, the power output.
It at least gets you all the right words to start googling for turbine options which helped me to do some back of the envelope math. It's a steeper hill than seemed feasible to me.
He doesn't need the pumped storage part of the equation due to a natural water flow, but it is part of the solution at least.
I suspect the amount of energy is far less than you are imagining... It takes a lot of water to generate a useful amount of energy. This video (https://www.youtube.com/watch?v=66YRCjkxIcg) does an interesting demo and points out that a 5 gallon bucket on a ladder has the same potential energy as a watch battery.
This guy (https://www.youtube.com/watch?v=tMLu9Dtw9yI) makes some good points about how cheap and scalable the technology is for medium-scale energy storage. It uses tried and tested, reliable and simple components for example
[1] http://www.u.arizona.edu/~deymier/deymier_group/refs/CAES.pd...
EMALS uses a big flywheel to power aircraft carrier catapults. The flywheel energy storage seems to cause most of the problems. The next generation of that system may use ultracapacitors.[1]
[1] https://www.ga.com/capacitors/military-mil-spec-capacitors
[1] https://repositories.lib.utexas.edu/bitstream/handle/2152/30...
https://web.archive.org/web/20151017100843/http://www.utexas...
The difference being one between a .50 caliber machine gun and something that can sink a ship from 100km away.
I worked across the street from CEM at the time. Firing the railgun was a big deal. The mechanical stresses on the electrical systems were pretty severe.
The vast proportion of what UT CEM was doing in that era was with the big gun, for Navy and SDI type projects.
You probably only have one giant flywheel, as the mass is where the energy storage gains make it worthwhile. Maybe you have many of them in parallel, but the size would make scaling an issue. Not to mention that there’s an associated drivetrain and linkages and so on. It’s a fully integrated contraption. It works, but many parts must work in tandem for it to be so.
This is in contrast to an electronic system, which would benefit from miniaturization and isolated redundancy. Racks of capacitors could run as hot spares when energy is abundant next to racks that may be down for maintenance. I doubt that a flywheel can be meaningfully inspected, let alone repaired or upgraded while operating.
That is the benefit of a modular approach to certain problems and not others. The two approaches are not always mutually exclusive either. Capacitors could be used as regenerative brakes for flywheels, for instance.
One thing to consider is that the heat generated by compressing the air could be vented into the home to warm it up in the winter, or simply allowed to escape outside in the summer. When discharging the cool air would either be released outside or inside of the home, depending on if you want to cool it off.
Large amounts of energy stored in an area is inherently dangerous, no matter the form.
Make no mistake, 8 bar escaping from a compressor is no joke. It's the equivalent of two elephants worth of air suddenly entering the room. It'll rupture eardrums and shatter windows but the building will still be standing. I wouldn't be so sure about that when a scuba tank decides to explode though.
You’re right, a vessel the size of a battery array is stupid. Because it’s all surface area and no volume, compared to a vessel the size of an aircraft, or a small stadium. You’d build one of these for an area of town, and the “size” that matters for stationary centralized equipment is not the displacement but the volume of material to make up the skin, the valves, the generator, and the piping to connect it all.
e.g. " By discharging the cylinders sequentially, the discharge time can be greatly increased, making the system comparable to lead-acid batteries in terms of energy density. Based on their experimental set-up, the researchers calculated the efficiencies for different starting pressures and numbers of cylinders. They found that 57 interconnected cylinders of 10 litre each, operating at 5 bar, could fulfill the job of four 24V batteries for 20 consecutive hours, all while having a surprisingly small footprint of just 0.6 m3.
Interestingly, the storage capacity is 410 Wh, which is comparable to the 360 Wh rural system noted earlier, which requires an 18 m3 storage vessel – that’s thirty times larger than the modular storage system. "
Also you missed the points of higher pressure vessels and using the residual heat/cold for things like hot water. Basically you trade off lower electricity efficiencies, space, and heat. Excess heat is not necessarily a bad thing in a domestic situation.
My take aways from this article:
- there are a few scenarios where stuff like this makes sense.
- there's lots of room for innovation and component improvement (e.g. more efficient dynamos are hinted at). This is currently a niche market and people have not put much R&D into this so far (i.e. I'd expect some improvements are entirely feasible).
- sequential vs. monolithic setups have different properties.
It boils down to cost / kwh and whether the requirements make sense. In an industrial setup, having a cheap but enormous vessel might not be the end of the world. In an apartment, you'd want maybe a smaller but higher pressure one.
But do you have reason to be skeptical about the physics? The premise here is brutally simple centuries old physics and engineering that any high school kid should be able to understand. Simple pressurized vessels holding compressed air. It sounds plausible to me that that ought to be dirt cheap to implement with very low tech solutions for pumping and compressing air and storing it in some kind of vessel.
You see people arguing here for an alternative based on Tesla batteries costing in the order of thousands of dollars even for a modest/small setups. It's kind of easy to see that this could potentially undercut that by orders of magnitudes because there are no special/hard to get materials and it's all based on dirt cheap commodities and technology. Pumps, valves, steel, etc.
If these numbers are accurate, then such a system seems quite feasible for domestic use. The others, much less so, as the storage vessels to store just a few KW/h are so massive.
http://www.fze.uni-saarland.de/AKE_Archiv/AKE2003H/AKE2003H_...
https://en.m.wikipedia.org/wiki/List_of_energy_storage_proje...
This may be because they over-provision so "rated" energy is met by replacement from a 110% sold capacity-type model.
I think the rest of the article is great. Fascinating.
Grid scale compressed air storage is a thing, and may have low energy efficiency, but so does PHES. The thing is, they can be huge, and they can sustain power for long periods. The heat loss story, I am confused by because usually this gets better with scale: you can exploit a lot of lower grade energy in heat/cool cycles, either to retain it in system eg heat transfer to another form of heat energy storage, or, for adjunct purpose like building heating or cooling.
Fan, not expert, experts can put me right!
Say you have two separate pressure vessels where to charge the system you pump air out of one into the other. Well the depressurizing vessel will cool down, but the pressurizing vessel will heat up. If they came to thermal equilibrium with each other their net temperature change would cancel out somewhat. This is great because it would restore the pressure on both sides to have more favorable conditions for energy storage and extraction.
So I wonder if you could design a pressure battery that would exhibit no change in temperature on the exterior throughout the charge/discharge cycle.
Blenders, washers, dryers, dish washers, garage door openers. Basically anything that uses a motor.
I doubt there's much of an ecosystem/incentive to build a compressed air --> <something> conversion systems that are general enough for anything to use.
Bonus: Compressed air is inherently dry. It'll come out of the motor cooler than ambient, but pass it through a heat exchanger and you'll get almost-room-temp super-dry air. (And maybe use the exchanger to condense some of the moisture out of the dryer's exhaust; you're halfway to a ventless condensing dryer already!)
I wonder if refrigeration appliances would be designed differently if they assumed compressed air as the power source.
On a side note, I wonder what the state of research is on reducing the embodied energy in li-ion battery production. The mentioned figure in the article is surprisingly high (2-10 times the total energy the battery will store - presumably they mean over its lifetime), which now that I think aboute it, squares with what I have seen elsewhere on the embodied energy of electric car manufacture.
Certainly not 10 times the total energy the kwh of battery capacity will store. Probably not more energy than the battery will store.
Simple economics puts the lie to outlandish claims intended to manipulate markets.
Their number is the reciprocal of this.
i.e. the total energy stored/discharged by the battery over it's lifetime = 2-10x the energy required to manufacture the battery.
Which still seems a bit conservative. The corresponding number they quote for their storage system is 240.
Are the figures correct, I couldn't find much follow up to that study?
I can imagine small-scale CAES being ideal where there is also a cooling load (eg humid tropics), since the expanding air will be cool and dry.
Having said that, you still need to do maintenance just like you do on a wooden house or a wheeled cart or anything that might fail dangerously. Wood rots over time!
If you wanted to compress the air 10x the atmosphere pressure, when it takes 10% of the normal volume, you would have to fill the tank with water for more than 90%.
Without water, you can compress air 10x and put 10x more of it into the same pressurized tank.