New Mars Forums

Official discussion forum of The Mars Society and MarsNews.com

You are not logged in.

Announcement

Announcement: This forum is accepting new registrations by emailing newmarsmember * gmail.com become a registered member. Read the Recruiting expertise for NewMars Forum topic in Meta New Mars for other information for this process.

#101 2022-09-25 11:08:08

tahanson43206
Moderator
Registered: 2018-04-27
Posts: 17,555

Re: Gravity Energy Storage

For SpaceNut re Gravity Energy Storage separated from steam ...

In the past, (if I recall correctly) you have posted about the idea of collecting energy from a supply of water running downhill.

The question I am posing about a geothermal well could be addressed above ground.

Consider a sky scraper with water delivered to the top floor.

The pressure exerted by gravity on the pipe at the bottom of that tower should be knowable.

The pump that delivers water to the resident in the Penthouse on the top floor has to push against that gravity induced pressure.

Now consider how you might harness that pipe full of water from the Penthouse. 

You would feed that water into a cold water turbine, and connect that device to an electrical generator.

The power thus provided would be good for some period of time.

It is ** that ** scenario I am proposing for the geothermal well.

The difference is that I am proposing to enlist thermal energy from the Earth to lift the water back up to the Penthouse, by turning it into steam.

Please post a skyscraper scenario, using the equations you posted earlier in this topic.

(th)

Offline

#102 2022-09-25 11:37:08

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 29,059

Re: Gravity Energy Storage

The cold water falling is if you have storage at the top of your building and that is the calculations that Calliban has done in the initial posts for a mars condition as a result of free excess energy needing to be stored. These are usually the quick release energy surge systems to take up for a lull in energy creation.

Thats a vertical fall and what I am working on is a slope.

Having the means to flash it to steam and to get that energy is where the closed loop of cooling it after the turbine is important.

What I am working on with the hillside is a slower more constant level of energy production and not so much a surge system.

Offline

#103 2022-09-25 13:08:51

tahanson43206
Moderator
Registered: 2018-04-27
Posts: 17,555

Re: Gravity Energy Storage

For SpaceNut re #102

Thanks for continuing the discussion of collecting power from gravity stored water.

We appear to have (at least two) versions of the technology under discussion.  The situation for a slope is similar to but different from a vertical stand pipe.

If you were to lay a pipe along the slope in your location, the pressure of the water at the bottom of the pipe would be the sum of the gravitational moments exerted upon all the molecules of water in the pipe.  You would measure that pressure as a single value at the valve at the bottom.

The same would be true of a vertical pipe, whether enclosed by a skyscraper skeleton, or enclosed by the walls of a vertical shaft in the Earth.

If you have time, please compute the head you might expect if you dropped a 20 kilometer pipe from the middle of your back yard.

I would expect the pressure at the bottom of that pipe to be substantial.

If you fed that water into an oven capable of converting the water to steam, then the water at the bottom of the pipe would be available to do work on a turbine.

It is ** that ** work I'd like to see converted to electric current that would be fed back up the shaft to be fed into the grid.

How much power could such a system deliver?

(th)

Offline

#104 2022-09-25 14:38:34

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 29,059

Re: Gravity Energy Storage

We know that 33 ft is the same pressure as it is at the surface for a 14.7 PSI measurement and for each next 33 ft just continues to add up for a vertical measurement. A slope is the sine function of the rise versus run.

The dam and reservoir combination makes use of a gravity but makes it continuous via the dam restrictions and inlet combination to the turbine after the drop. It's that combination that makes it continuous as a shaft or build of head pressure is a onetime drop that has limited quantities of water to all for the fall.

So, if you want to use the water in a continuous mode you want to after each drop allow for another reservoir and dam with more generators to do this again and again after every drop made, until there are no more drops to be made.

Offline

#105 2022-09-25 16:04:00

Calliban
Member
From: Northern England, UK
Registered: 2019-08-18
Posts: 3,484

Re: Gravity Energy Storage

TH, the pressure of the water at the bottom of the pipe is purely a function of the difference in height between the revervoir and the exit.  Friction will give you some pressure drop, which is lost energy.

If you put that pressurised water into a boiler rather than into hydroelectric turbine, then you will be able to raise steam at the same pressure as the inlet water, provided your boiler is hot enough to reach the saturation temperature of water at that head pressure.  What it means in practical terms is that you won't need a feed pump for the boiler, as hydrostatic pressure is replacing pumped-pressure.

You could put a turbine, generator and condenser at the top of a hill, with a boiler at the bottom.  Feed water would run down the hill from the condenser and the difference in height would give you the feed pressure needed to balance steam pressure in the boiler.  No feed pumps required.  Steam would run up the hill to the turbine.  So you get a cycle, with gravity providing your condensate return.  Gravity would also help dry the steam.  The downsides to this cosy arrangement are that a 200 bar steam pressure, would require that the condenser has a 2000m head height above inlet to the boiler.  That would make the steam pipework impractically long.  Thermal losses would be horrible.  But if your heat engine is working at relatively low temperatures, i.e. if it were using geothermal or solar heat to raise steam, then steam pressures might only be a few bar.  A height difference of 100' is enough for 3 bar feed pressure.

If your steam temperature is 100°C and your condensor is at 30°C, then 9.9m height difference is needed, as the condensor pressure is 70mbar.  Efficiency would be terrible, no better than 15% and probably lower.  But you would not need feed pumps.  A single LP turbine without reheat will do the job.  And as the whole system is operating under vacuum (at Earth Sea Level), your boiler, steam pipework, turbine casing and condenser, can all be made of reinforced concrete, which is a lot cheaper than alloy steel.  Maybe this is a system that is worth investigating, for Earth and Mars.  A low pressure nuclear reactor, generating heat at 100°C, is much easier to build than a unit raising steam at 200 bar and 300°C.  Sometimes, we can accept lower efficiency if something is a lot easier and cheaper to build.  It works even better if you can find a use for the 85+% of energy that is ejected as low grade waste heat.  On Mars, that's easy.  On Earth, we have discussed district heating and desalination as uses for waste heat.

Last edited by Calliban (2022-09-25 16:09:00)


"Plan and prepare for every possibility, and you will never act. It is nobler to have courage as we stumble into half the things we fear than to analyse every possible obstacle and begin nothing. Great things are achieved by embracing great dangers."

Offline

#106 2022-09-25 17:06:18

tahanson43206
Moderator
Registered: 2018-04-27
Posts: 17,555

Re: Gravity Energy Storage

For Calliban re #105

This post is (primarily) to thank you for taking a look at the situation in this topic.

We have more than one vision in development.  You've just added contributions that look as though they will be helpful to both.

I'm trying to work with a 20 kilometer deep geothermal well, and (I think) SpaceNut is working with the slope of a back yard supplied with water from a well, or perhaps from rain when rain happens.

The reason I proposed making electricity at the bottom of the geothermal well is to take advantage of the generous head that the Earth would provide for the water column.  Thanks for pointing out the reduction of efficiency due to turbulence at the walls of the down pipe.  That is an interesting complication.

The heat loss on the up cycle is another factor that would impact the power delivered to the customer at the top of the well.

I'd like to (try to) design a geothermal well that would deliver 1 megawatt of reliable power for 1000 years.

Some maintenance would be required, and an earthquake could spoil the fun in an instant, but your suggestion of concrete pipe seems ** really ** helpful.

If the power generator at the bottom of the pipe feeds AC at high voltage back up the pipe, then (it seems to me) the maximum possible efficiency could be achieved, comparable to the efficiency of hydroelectric power stations already in existence at multiple sites world wide.

As you pointed out, heat loss on the way UP the pipe might reduced potential power take-off at the surface, since the steam will be exhausted  by the time it reaches the surface.

Again, thank you for taking a look at this topic.

(th)

Offline

#107 2022-09-25 18:05:42

Calliban
Member
From: Northern England, UK
Registered: 2019-08-18
Posts: 3,484

Re: Gravity Energy Storage

20km is substantially deeper than the deepest boreholes that humans have dug so far and is over 50% of the way to the mantle.
https://en.m.wikipedia.org/wiki/Kola_Superdeep_Borehole

The Soviets found that they could not drill deeper than 12km, because the rocks became plastic.  God only knows how much it cost them.  But the facilities that they needed were considerable.

If you want a 1000 year power plant and really don't care how much you pay upfront, there are probably easier ways. You could combine solar thermal power with underground thermal energy storage.  A 200m layer of rock is a formidable insulator.  The solar thermal plant won't last 1000 years, or even 100 years, but the geothermal plant won't either.  But maybe the thermal store will last that long.  If capital costs don't matter, then you coukd build windmill towers out of solid stone and use robust carbon steel bearings and gears.  You will need to replace the blades every few decades.  But everything else will last for centuries if properly designed.

Of course in real life, capital costs always matter.  I doubt you would be willing to pay $1million for a car or personal computer, unless that device offered real benefits that a cheaper model did not.  Knowing that it will last 1000 years (which is probably impossible) won't sway you, because you won't be around that long.  And neither will your children or grandchildren.  And a power station isn't a ferrari.  A huge capital cost means a huge bill.  The electricity that you get from it will be identical to what you get from a plant with a tenth or hundredth the power cost.


"Plan and prepare for every possibility, and you will never act. It is nobler to have courage as we stumble into half the things we fear than to analyse every possible obstacle and begin nothing. Great things are achieved by embracing great dangers."

Offline

#108 2022-09-25 18:06:08

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 29,059

Re: Gravity Energy Storage

For my current thoughts having a thermal source to create steam is not possible as its deep in the woods where I cannot use any solar derived energy to do this and making use of other sources would be too costly. So, a pulley style system is the best that I can do with limited water supplies.
This is sort of like a zipline for how the mass of the 5-gallon pale would ride to the bottom of the hill. Sort for this I need to understand the cable's ability to not sag and its required strength to support the mass from the top all the way through its run until it reaches the bottom.

https://www.ziplinestop.com/pages/zip-line-calculator
https://www.ziplinegear.com/pages/how-t … e-concepts

https://outdoortroop.com/how-fast-is-a-zip-line-ride/

https://sciencebehindthesport.wvu.edu/s … lculations

Offline

#109 2022-09-25 20:30:53

tahanson43206
Moderator
Registered: 2018-04-27
Posts: 17,555

Re: Gravity Energy Storage

For Calliban re #107 and SpaceNut re #108

Thank you for your respective contributions to the topic.

SearchTerm:plastic rock cited by Calliban at 20 km depth
SearchTerm:Zipline for power generation cited by SpaceNut

The latter idea seems quite useful for a camping trip, if the family is high on a mountain and there are plenty of rocks for the kids to load into a pair of buckets.

it wouldn't take much garage mechanic engineering to make a generator that would harness the energy stored by Nature just for your use.

This would (the more I think about it) be a fairly efficient way to harness the gravity stored energy of water, and a lot less expensive than making some sort of hydraulic system.

SpaceNut ... can you work out the potential energy gains that might come your way if you build such a zip line?

You can arrange things so the buckets empty automatically when the reach the bottom of the zip line and rotate back to the top.

I am reminded of some of Calliban's reports on gravity fed mining operations.

(th)

Offline

#110 2022-10-02 20:49:14

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 29,059

Re: Gravity Energy Storage

The pail of water will empty just before it gets to the bottom shortly after the pail at the top is filled with water with a third pail already on the return side of the slope empty so as to get filled once at the top.

I need to get actual measurements for the height of the hill and the slope length so that I can calculate what the potential will be for a 5-gallon pail of water.

gravitational potential energy, =mgh

The pail will then follow the water slope function as if it's flowing constantly across a turbine of water wheel but in actuality is just 1 pale of water moved by gravity. Its kinetic energy is converted to movement as it rides down the slope in the form of rotation.

Most alternators run at 1000 rpm's so a larger wheel connects to the smaller wheel that the connecting cable rolls on. The smaller alternator steps up ratio is accomplished by having a large wheel for the small alternator wheel to ride against. It's a step-up transforming ratio that happens to make the alternator spin more times in a minute.

Offline

#111 2022-10-03 06:01:35

tahanson43206
Moderator
Registered: 2018-04-27
Posts: 17,555

Re: Gravity Energy Storage

For SpaceNut re #110

Thanks for continuing to work on this very practical sounding idea.

This is an alternative to the traditional solution of a water wheel.

It seems to me the difference is in the flow rates that the two systems can accommodate.

A water wheel depends upon a flowing stream, and it can be sized according the available flow.

This cable system (with three 5 gallon buckets) can work efficiently when the bucket at the top is full.

It would be unproductive between fill events, but fully productive during a descent cycle.

On the other hand, if the flow becomes constant (as after a rain storm and accumulation in a catch basis), then the cable system would be constantly productive.

Thus, this system seems ideal for a situation where water supply is intermittent or modest or both.

Please keep working on this, and post your results.

If you develop something worth permanent storage, we have the Dropbox account available for permanent storage.

On Mars, there is no precipitation available, but it might turn out that conditions are right to collect CO2 from the atmosphere as dry ice to fill the bucket.  I'm thinking of Mount Olympus as a location for a cable system, for example.

A supply of CO2 at the bottom of the cable would feed directly into a production facility to make Oxygen, such as Krusty, or perhaps something to take the next step to make the full fuel/oxidizer combination of CO and O2 to drive the Martian economy.

You might even be able to develop an article for publication or presentation, if you are able to carry this through to the Real Universe.

I estimate it would take you a solid Earth Year from start to finish.

Fortunately, we ** do ** have plenty of time.

(th)

Offline

#112 2022-10-03 06:46:52

tahanson43206
Moderator
Registered: 2018-04-27
Posts: 17,555

Re: Gravity Energy Storage

For SpaceNut re Gravity Water Cable experiment ....

This is an idea which could become reality in the Real Universe, and which could have educational value for others.

It will take some time to move from vision to reality, but the investment in dollars (USD) ** should ** be modest.

Please provide a few details about the test site that is available.

What is the likely distance of the run?

What is the slope for that distance?

Ordinary flexible wire clothes line cable should be sufficient for this application, but the method of joining the ends of the cable so they last for years of service passing through the pulley while under tension is going to be a challenge.  At this point, I have no idea how to do that, but it ** must ** be achievable, because all those cable systems that Calliban showed us would have had to have such a joint.

You've already begin thinking about adapting automotive technology to this application, and others around the world would have access to such technology for their reproduction of your invention.

It would be helpful to have pictures to show of the stages of development of the system.

A YouTube video is a very practical presentation option in today's world.

(th)

Offline

#113 2022-10-03 19:03:30

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 29,059

Re: Gravity Energy Storage

The first pale to start down the hill is a delta velocity that is v of zero while the time to get all the way done would be max but since I am using rotation at the end and a 1/3 refilling it's going to achieve a different speed but at that point the next pale will fill while the one at the bottom will empty such as to keep the speed constant.

This is a horizontal windmill unit on top of a tower. With a low RPM generator under the wheel looking like a pancake.
An alternator would ride against the outer diameter of the windmill wheel so as to get higher rpm from the ration of the alternator pully to the wheel diameter.

R.0415918040ee6faa2ea543b11913c2e1?rik=jmthTt%2baXW5ArA&riu=http%3a%2f%2f3.bp.blogspot.com%2f-_jJxxcSsrAQ%2fTpXsNSjD31I%2fAAAAAAAAA8A%2fSBajaU5nqeo%2fs1600%2fHesperia1.jpg&ehk=Bx7Dc4u92APZWZk9YzrdE3d7I5Eb37uvwtoZFhSm5eY%3d&risl=&pid=ImgRaw&r=0

Looks like a water wheel. Of which I am replacing it with a bicycle wheel and a cable that will ride in the location of the tire inner tube area.
This will set on the top of a tower possibly like this.

old-windmill-tower-hdr-randy-harris.jpg

a matching tower and wheel will rest at the bottom of the hill with the cable wrapping around both ends.

Coming up with a cable will be the issue for me to overcome as well as to create the generator to make use of.

Offline

#114 2022-10-03 19:56:57

tahanson43206
Moderator
Registered: 2018-04-27
Posts: 17,555

Re: Gravity Energy Storage

For SpaceNut re #112

The images you've assembled are certainly interesting!

Question regarding the rate of descent of the pail ... Would it make sense to use a governor to insure the cable turns the generator at a constant rate?

I'm thinking of the mechanical governors that were popular in steam and early gas engines.

Here's a well done YouTube animation that shows what one looks like: https://www.youtube.com/watch?v=HS_YGZXP2xY

Something to keep in mind is that in a situation with a slow moving water source, a pail might take a while to fill, but no harm done, if the generator can operate intermittently, such as to charge a battery.

Once the pail is full, the automation controlling the system can release it to move down the incline, while bringing the empty bucket back up.

(th)

Offline

#115 2022-10-08 17:14:36

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 29,059

Re: Gravity Energy Storage

I was looking at some sort of speed control as well but until I get to build, I will not have much for numbers to work from.

I had seen and article, but it was gone when I went back so here is a google search for it
http://en.cnesa.org/
The China Energy Storage Alliance is a non-profit industry association dedicated to promoting energy storage technology in China

'Power up' for China's energy storage sector

Industry estimates show that China's power storage industry will have up to 100 million kilowatts of installed capacity by 2025, and 420 million kW installed capacity by 2060, attracting related investment of over 1.6 trillion yuan, said Li Jie, general manager of power storage at State Grid Integrated Energy Service Group Co Ltd.

I did see a lake as another means for the China storage but when I did a search, I also found compressed air as well and will post those in that topic.

Offline

#116 2022-10-08 18:18:11

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 29,059

Offline

#117 2022-10-09 06:29:51

tahanson43206
Moderator
Registered: 2018-04-27
Posts: 17,555

Re: Gravity Energy Storage

For SpaceNut re Cable Bucket Power Supply vision

It is possible your vision can be turned into working reality in the Real Universe.

For that to happen, the elements of the vision need to transform from mental images in the minds of your readers, to a set of actual photographs of working hardware.

A clue as to the possible form of your vision appeared in a recent post, when you suggested mounting bicycle wheels as the pulleys over which a cable would run.

Details of how the buckets would be managed need to be worked out.

The local State Fair grounds has a popular ride featuring cable cars.  The pivot wheels at the ends of the (very long) line are oriented so that the axis of rotation is vertical.  The cars are suspended on the cable using "J" shaped claws.

These claws are able to negotiate a trip around the pivot without falling off or damaging the pivot wheel.

I could supply pictures of the equipment if necessary, but it is possible the Internet can provide detailed drawings.

In fact (thinking about this further) there are ski lift systems that (appear to) use a similar system.

The system you design needs to be able to pass the buckets safely around the pivot wheels.

If you were going to build one of these systems, where might it go?

I'd sure like to see this system constructed and running within a year on the outside.

Perhaps it might be working sooner, but a year is (hopefully) enough time to get from vision to reality.

Update a bit later .... water wheels are a well studied way of translating gravity energy into rotary motion.

Small buckets can be mounted on both sides of a bicycle wheel mounted with the axis of rotation horizontal.

A small stream of water can be directed horizontally from a source at a higher location, to just above the water wheel.

Water flowing into the small buckets could (and would) provide torque to cause the wheel to rotate against the resistance of a small generator system.

Such a system would have fewer moving parts exposed to the weather.

(th)

Offline

#118 2022-10-09 10:28:33

tahanson43206
Moderator
Registered: 2018-04-27
Posts: 17,555

Re: Gravity Energy Storage

For SpaceNut re water wheel design ...

Bing came up with a citation for a study ? book that examines multiple types of water wheel designs.

https://www.sciencedirect.com/science/a … 20flexible.

In particular, the linked page gives 85% as an efficiency target that might be achieved.

The linked page describes multiple ways of pulling energy from water.  Gravity and buckets are included in the alternatives.

Gravity water wheels rotate around an horizontal axle. Maximum efficiencies of gravity machines are included between 70% and 90% [19], [28].

Three main types of gravity water wheels can be identified: overshot, where the water enters from the top, breastshot and undershot, where the water enters from the upstream side. Depending on the water entry point, breastshot wheels can be distinguished in high, middle and low. High breastshot wheels receive water over the rotation axis; middle breastshot wheels near the axis, and the low ones under the axis. Low breastshot water wheels can be also called undershot water wheels. Schematic historic representations are depicted in Fig. 2. The most efficient kinds of undershot water wheels are Sagebien water wheels with forwards flat blades and Zuppinger water wheels with curved blades. Sagebien wheels are optimized for minimizing the inflow power losses, ensuring a gentle entry of blades into the upstream water. Zuppinger wheels are designed with blade shape to reduce the outflow power losses, reducing the portion of water that is uplift over the downstream water surface. Schematic historic pictures are depicted in Fig. 3. Gravity water wheels are the subject of the present paper.

The page appears to be available in pdf form.  There are high quality illustrations showing the bucket version in at least four layouts.

(th)

Offline

#119 2022-10-09 14:14:30

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 29,059

Re: Gravity Energy Storage

Finally trying to get some base numbers for the property path and drop shape.

I stood at the bottom of the slope where the water would exit into the stream bed and sighted my first tree at eyeball height of 5 feet at the first 100 feet and so on until I got to the top of the rise.


Tip of the rise 10 ft H x 50 ft L
                           10 ft H x 50 ft L
                                10 ft H x 100 ft L
                                     10 ft H x 200 ft L

grand total of height change is roughly 40 ft H x with a horizontal distance of 400 ft L
I see post 90 I had the L at 300 ft of which the extra hundred gives a longer run.

Nice link but what I am doing limits the required water such that I do not need it to make the wheel continue to move but instead I am using gravity to substitute with a give mass to come out with that same speed of flow value.

The over under does really not apply to the design but the image shows what I can expect if the generator is moving at the charts speed.

1-s2.0-S1364032118306178-gr1.jpg

Offline

#120 2022-10-09 19:20:52

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 29,059

Re: Gravity Energy Storage

In addition to mechanical governor for speed control but you can also make use centrifugal clutch and flywheels as well.

Flywheel is an internal energy storage device. It absorbs mechanical energy during the period when the supply of energy is more than the requirement and releases it during the period when the requirement of energy is more than the supply. The main function of a fly wheel is to smoothen out variations in the speed of a shaft caused by torque fluctuations.

https://www.mechanical-farm.com/ufaqs/w … -governor/

https://engg.directory/difference-betwe … -explained

Governor-and-Flywheel.jpg

https://www.slideshare.net/trishamgarg9 … -governors

Offline

#121 2022-10-11 09:11:24

tahanson43206
Moderator
Registered: 2018-04-27
Posts: 17,555

Re: Gravity Energy Storage

For SpaceNut re construction of working model of power system

It should be possible for you to build a working model of the system you are considering for the property available to you.

If you have space in the basement, you could work on the system over the coming months, and deploy it to the outdoors when conditions are more suitable.

It is not necessary to begin at full scale.  A small version of the system would allow you to work out all the mechanical details, and (more importantly) report your progress to the forum.

This forum has been in existence for over 20 years, and with the sole exception of one member, absolutely NOTHING has happened in the Real Universe as a result of all the intense thought recorded in the thousands of posts we have in file.

Here is an opportunity for you to show the way forward for future readers.

A working power conversion system would be immediately useful at multiple locations around the world, where a small but steady supply of water is made available by Nature's application of Solar Power to lift water to high elevations, to transport that water around the world, and then to drop it off at arbitrary locations.

The total amount of water lifted and transported is ** increasing ** due to climate change.  Your power system could be used where water is present.

As I  consider the options that might be available in a mountain location (for example) your design (cable transport) seems to me to compare favorably to alternatives that might use pipes to deliver hydraulic pressure down a hillside.

You ** should ** be able to work up an article on the system for publication online if not in print.

***
As an example of the kind if critical detail that you could study in a home workshop, is the method of mounting buckets on the cable so they can pass the pivot wheels at the ends, as well as lift locations along the line, such as those used routinely in Real Universe cable transport systems.

(th)

Offline

#122 2022-10-11 11:17:56

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 29,059

Re: Gravity Energy Storage

A gallon is 3.76 kg of mass and 5 of these is 18.8 kg total.

I am looking to build a 1/10 scaled model to get real numbers for the flow rate speed. which makes it 4ft tall with a run of 40 ft with a pale that is near 1/2 gallon or 1.88kg. I can get test data over a variety of mass under the model.

Offline

#123 2022-10-11 14:46:27

tahanson43206
Moderator
Registered: 2018-04-27
Posts: 17,555

Re: Gravity Energy Storage

For SpaceNut re #122

This seems (to me for sure) like a well-worth-while undertaking.

Very few folks in the modern age have experience with cable systems of any kind.

There is probably a wealth of remaining knowledge and experience in the industry that supports snow recreation facilities, for as long as we have them.

One suggestion I ** do have (if you decide to go with horizontal axle for your wheels, instead of vertical like a ski lift) is to mount two buckets on the cable, so the load is evenly distributed.  A ski life (or at least the one's I've seen) use a "J" shaped hook that presses down on the cable from above, and transfers support to the gondola below through the metal bracket.

In any case, I'm looking forward in hopes you'll have the time needed to carry this investigation from vision to Real Universe hardware.

(th)

Offline

#124 2022-10-15 19:28:56

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 29,059

Re: Gravity Energy Storage

I ran a scale test of the cable slide with an old clothesline pulley and a 2 quart of juice in a bag such that I tied 1 end of a parachute cord to a basketball pole and anchored the other to the ground some 40 ft away.

Several test runs were performed just counting the seconds to when the run made contact to the ground, each time I stretched the cord a bit more to try and get the most out of the run distance. Normally this end plus the start will be higher so as to get the rotation at the ends to never make contact to the ground.

The length for the cord was 45ft with contact occurring 35ft from the start of the zip line to contact 6 sec approximate starting at a height of 4-5ft.

The pulley was well weathered but shows that in principle it's going to do what I need it to do plus this time and parts will be different in that it's not sort of rusty and will be a bit stronger with a cable for the mass to ride down.

So, what should the time be by calculations of 32ft/sec at a 4 ft height (4/32) which is the opposite for angle C for the hypotenuse run of 45 ft. which comes back as 5.625 seconds.

edit:
the clothesline pulley diameter is 6" and I placed the 2-quart bottle in a plastic bag that was tied to the hook bracket that is part of the pulley assembly.

500_F_171695_jVWSGCdwF2h0nbPq01BcQEfSuZrAbu.jpg

Offline

#125 2022-10-15 20:57:33

tahanson43206
Moderator
Registered: 2018-04-27
Posts: 17,555

Re: Gravity Energy Storage

for SpaceNut re #124

Thanks for reporting your experiments today.

Bigger picture... thanks for taking the lead for the entire forum, by moving from theory to physical experiment.

Your reported descent time of 5.625 seconds was without a load.

A rule of thumb I remember from a thesis on harnessing water flow is that you can get 1/3 of the energy out of a system like this.  That was for a water wheel experiment, so your results may be better, since you are keeping the water in a container.

Never-the-less, there ** will ** be some point at which the resistance of the load will cause the gravity feed to balk.

As a working hypothesis, it might be worth aiming for a descent time under load of 1/3 more than your reported 5.625 seconds. 

By keeping accurate records of the time of descent as you increase the load, you should be able to calculate the system efficiency.

My guess is you'll do well to capture 1/3 of the potential energy.

The efficiency of the generator will factor into the results as well.

(th)

Offline

Board footer

Powered by FluxBB