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#26 2019-11-28 08:07:15

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

Re: Gravity Energy Storage

For Calliban re #22 and earlier ...

Thank you for considering the topic (of gravity storage) further, and for adding additional examples of creative design from the historical record. 

In an earlier post (in this topic or another) you reported the invention of a means of compressing gas (air) in a liquid (water) by allowing bubbles to flow down a column of moving water, as into a mine for tools and breathing air.  I am looking forward to finding a block of time to follow the link you provided, to try to understand the concept better, and the specifics of how it was used.

We appear to have the potential for a robust design competition to develop solid plans for various energy storage systems which could be deployed on Mars, or perhaps other locations in the Solar system.

You and SpaceNut have both identified real or imagined weaknesses of gravity storage systems, and that kind of feedback should lead to improved designs which would ultimately find testing in the real world.

However, gravity storage has more than one branch, and there are competing storage proposals, such as batteries, superconductors and even chemical state change for long term storage.

I would like to see a (somewhat) organized competition between the design concepts.

All require physical components, so the benefit of one design over another will depend upon the availability of particular materials and the amount of energy required to shape them into the form needed.

All will require maintenance, and the details of where failure will occur and how it will be addressed will lead to understanding of relative strengths and weaknesses of particular designs

The use of water for gravity storage on Earth makes a great deal of sense where weather patterns deliver copious quantities of water for such use.

The absence of water in many locations on Earth would encourage use of available material (eg, sand) for gravity energy storage.

In the case of Mars, it seems (to me at least) ambitious to imagine a water based energy storage solution.

Some confusion exists (at least as I read the current topic) because the starting point was the idea of a cable storage system found by SpaceNut.

I have been moving steadily away from the original suspension cable system to an alternative based upon a hybrid of cable to provide flexible anchoring for mass (eg, carts filled with sand) running on a solid monorail such as may be seen in many installations on Earth for short distance transportation.

For further clarification, I am thinking of a monorail BELOW the moving components, NOT a suspended monorail.

The idea there is to take advantage of the natural stability and long life offered by the planetary terrain, and to minimize the number of components or design elements under tension against the gravitation field.

The problem of how to draw power from a cable with carts clamped to it has received some attention here in recent times.  I don't have a solution worked out, and don't like the idea of unclamping carts from the cable to allow the cable to pass over a wheel connected to a generator.

I'm hoping to have the time to explore energy requirements for operating a decent sized steel mill. 

A quick Google search brought up Wikipedia articles about the steel industry, but I did not find reference to heating other than the historical reference to coal.

Another quick search brought up electric arc melting of scrap metal in specialty shops.

That option is more along the lines of what seems appropriate for a serious steel mill operation on Mars.

Louis' methane could certainly be used, so long as whatever process produces the methane also produces the oxygen needed for combustion.

And in any case, Louis' methane will require water for the hydrogen, so that will be needed in abundant quantities.

A gravity storage system that runs up the slope of Mount Olympus could (depending on how the numbers look) provide the concentrated energy needed for a full scale steel manufacturing plant. 

Edit: The challenge of drawing power from a moving cable encumbered with clamped mass carriers might be overcome by a combination of suitable spacing of clamps on the cable, and multiple power take-off positions at the generator station. While this system would require movement of the power take-off wheel, and therefore add to the mechanical complexity of the system, it would/should be fairly straight forward to design and implement.

OK ... a shift of the generator station to the end of the cable run would eliminate the need for the added complexity.

And as SpaceNut pointed out, the clamps for the mass carriers would need to be fitted with pivots, to negotiate the transition from the slope to the roll-out flat section of the track.

And the addition of a lifting motor station at the top of the slope would assist with drawing the mass up the slope, again without need for additional mechanical complexity.  The lifting motor would (presumably) be near the field of solar panels to be harnessed to lift the mass up the slope.

Edit(2): Here is a financial summary of steel making in (about) 2019:
https://www.thebalance.com/steel-production-2340173

(th)

Last edited by tahanson43206 (2019-11-28 10:17:34)

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#27 2019-11-28 12:52:53

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

Re: Gravity Energy Storage

Regarding steel making, a good place to start is embodied energy, which includes estimates of energy needed in all activities to produce the material.  In the case of steel, it is dominated by smelting.

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

Something like 70% of all steel in the EU comes from recycling now, so only a third of steel is virgin steel that requires metal oxide reduction by carbon monoxide.  Modern steel furnaces rely on electric induction for achieving the required temperatures.  On Mars, we would likely do the same.  Direct electric would bring the furnace to temperature, whilst methane, hydrogen, CO, etc. will serve as reducing agents.  That reduces the fuel requirements substantially.

To make 1kg of steel from 70% recycled steel, takes about 20MJ.  For virgin steel, about 30MJ/kg.  That reflects the extra fuel needed to chemically reduce the iron(ii) oxide into pure iron.

On Mars, to produce 10MJ of hydrogen for reducing iron oxide, will take about 15MJ of electricity.  So 1kg of low carbon steel on Mars will cost a minimum of 35MJ.  This energy assumes a scale economy that we may not be able to achieve on Mars (smaller furnaces are less efficient) but it allows a baseline cost for now.

Suppose we need to produce 100 tonnes of steel per day to manufacture a pressure dome.  That is an energy cost of 100,000kg x 35MJ = 3.5million MJ.  That is a continuous power input of 40.5MW – a lot of juice.  The temperature of the refractory lining is about 1200C.  The thermal expansion at those temperatures is so great, that thermal cycles inevitably result in cracking, which damages the lining.  Once you start a blast furnace, you don't want to shut it down unless absolutely necessary.  You need baseload power to make steel, although the power used to make the hydrogen, methane or CO reducing agent, could be variable, at least to a point.

We will need a lot of steel to make any pressurised structure on Mars that isn't underground.  That includes steel pressure struts for things like greenhouses, in which to grow food.  I worked out previously that producing 3000m2 of cropland on Mars (the amount needed for 1 person), would require 36.7tonnes of low carbon steel for pressure resisting frames.
http://newmars.com/forums/viewtopic.php?id=9187&p=2

So, producing enough farmland for one person would require continuous power of 40kW for one year.  Then you have the energy cost of water (1MJ/kg) and heating.  Living on Mars will be an energy hungry activity and most of that energy must be baseload.  That means lots of nuclear power.  And it need to be cheap.

http://newmars.com/forums/viewtopic.php?id=9197

Last edited by Calliban (2019-11-28 12:55:59)


"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."

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#28 2019-11-28 13:22:26

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

Re: Gravity Energy Storage

Have copied the post industrial

The post is just a scope of what levels of power will be needed in the future and just why its important to save up that energy for later since we are going to be very limited to the type of nuclear power to which early mars will be started with.

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#29 2019-12-11 17:38:40

knightdepaix
Member
Registered: 2014-07-07
Posts: 239

Re: Gravity Energy Storage

tahanson43206 wrote:

mountains-for-long-term-energy-storage-hg.jpg

Can the lower storage site be connected to a Parabolic antenna that received microwave from solar panel in Mars Orbits or Phobos

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#30 2020-01-17 18:35:30

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

Re: Gravity Energy Storage

We are still talking about the most efficient form of storage and conversion rate for Electricity, Work, and Power

Summary of Force, Work and Power

Force = Energy applied to an object(Measured in Newtons).

Work = Force X Distance, or the amount of heat transferred (Measured in Joules or calories).

Power = Work/Time (Measured in Watts)

Various Energy Units

1 calorie (thermochemical) = 4.184 J

1 Btu = 251.9958 calories

1 Btu (thermochemical) = 1054.35 J

1 kilowatt-hour (kWh) = 3.6 x 106 J

1 kilowatt-hour (kWh) = 3412 Btu (IT)

1 therm = 100,000 Btu

1 electron-volt = 1.6022 x 10-19 J

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#31 2020-01-18 11:17:43

knightdepaix
Member
Registered: 2014-07-07
Posts: 239

Re: Gravity Energy Storage

knightdepaix wrote:

Can the lower storage site be connected to a Parabolic antenna that received microwave from solar panel in Mars Orbits or Phobos

How about installing GES on Olympus Mons? It has a very gently sloping profile, allowing facile maintenance after a road be built from the bottom to the top beside the cable. By the same token are GES systems on Mons of Ascraeus, Aria, Pavonia, Elysium feasible? They are all higher than Mount Everest.

Is the energy from the GES on Olympus Mons enough to support the number of people in Italy or the Philippines?

Last edited by knightdepaix (2020-01-18 11:29:01)

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#32 2020-01-18 13:01:25

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

Re: Gravity Energy Storage

At the foot of the hill we have potential energy of a mass rise to be stored at the new location at the top of the hill where in the mass is not changing only the initial energy needed to make the change is negative kenetic in the form of eletric expended..We have the initial and final energy lose as well for momemtum. Other loses are in the form of friction to motion.
https://en.wikipedia.org/wiki/Potential_energy
https://en.wikipedia.org/wiki/Kinetic_energy

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#33 2020-03-29 11:52:04

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

Re: Gravity Energy Storage

tahanson43206 wrote:

This post is offered for Calliban ...

https://www.yahoo.com/news/feature-zero … 42337.html

As I read this article, it ** sure ** sounds like the pumping technology Calliban brought to our attention some time ago.

Edit#1: The technique I'm recalling was compression of gas by a falling column of water. Developed for use in early (17th/18th Century) mining operations.

The method appears to draw energy from a large downflow of water to lift a small volume to altitudes where it is needed.

While this post is in Technology Updates, it involves a modern use of what must be an ancient technique.

(th)

The real trick is how to get the water up to the storage area without expending energy to move it there. Of course this is where some claim free energy for use is excess energy production from solar, hydro ect... which does not have a buyer for the energy and since that is in AC form we need to convert that to a storeable. That is where efficiency losses come into play for convertion, storeage and later use of it.

1. One method would be is to use rain water that falls into catch basins along mountian water areas. so as to keep it in an elevated state for later use.
2. Another such area to do the catching would be road side drain systems to just send it to ocean going streams.

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#34 2020-11-22 19:36:42

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

Re: Gravity Energy Storage

Found this paper is in support of using a hillside and a deep valley to send regolith down its slope that would be processed in the valley which made use of the slope to generate power. The cars would be filled at the top and emptied for the trip back up to the top.
A dual generator system would make the power needed at the top and one at the bottom.

MegaPower: Generating Electricity for Our Future on the Red Planet

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#35 2020-11-24 16:41:55

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

Re: Gravity Energy Storage

On Mars, liquid CO2 could be used in pumped storage systems.
https://en.m.wikipedia.org/wiki/Carbon_dioxide

Both upper and lower tanks would be kept at a pressure of at least 5.1bar to keep the CO2 liquid.  Provided that it can be maintained in a liquid state, it should function exactly as water functions in pumped storage here on Earth.


"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."

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#36 2020-11-24 17:14:24

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

Re: Gravity Energy Storage

The energy for mars via wind, solar are not of duration of 25 hr x 7 days a week time span while the kilowatt reactor is and that is where the reactor is required to fill the need for constant life support while the others are the bank of goods and energy needed as potential for later use.

Using the gravitational potential energy formula, PE = m*g*h, we found that a one Kilogram mass at a height of one meter has 3.8 Joules of potential energy on Mars.

So the potential energy at the top of a hillside that rolls or falls down it is the mass of the materials going the distance from verticle rise to the end terminus at any angle give the speed for the mass if unrestricted for the energy ammount that we will gain.

If we need co2 compressed then rather than we would want direct drive of the compressor at the top and bottom of the ramp so that we get what we need drawn in from the falling mass.

The number of buckets with mass can be variable for the bucket count on rise and fall are static for actions on the moving parts so its only the change from filling that is the limiter and how fast the mass can be poured out and moved to make way for the next bucket of mass that is on the machine we build.

So energy to fill and energy to remove the contents must be factored in for how much energy we are truely creating from the filling, moving down a slope gravity fed and then moved away from the end of the line dumping.

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#37 2020-11-24 19:26:20

SpaceNut
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#38 2020-11-25 07:27:44

tahanson43206
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Posts: 17,555

Re: Gravity Energy Storage

For SpaceNut re #37

Thank you for the research you did to assemble the list of links and topics relating to Gravity Energy Storage.  Thank you for providing short hints about the value of some of the links. 

You posed an (interesting to me) question .... could CO2 function as a fluid in a Mars implementation.  This topic (Gravity Energy Storage) started out (as I recall) with the idea in mind of working with solids.  The Wikipedia article on Liquid_carbon_dioxide should provide insight into what temperature range on Mars would allow for use of CO2 as a liquid for operation of a turbine at the bottom of an incline.

In the video recently highlighted from the Mars 2020 conference, (as I recall) Alan Stern showed evidence of methane flows on Ceres. 

It is entirely possible that members of this forum have already explored this question in detail and arrived at specific knowledge that could be employed on Mars to generate energy using flowing CO2. 

The Wiki format may be better for knowledge storage and recovery than this ever-flowing forum format.

Did the Mars Society ever set up a Wiki?

(th)

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#39 2020-11-25 10:29:09

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

Re: Gravity Energy Storage

Yes but I think its crashed content has been moved to https://marspedia.org/Home as it was not restored as the old wiki but hopefully some of its content was pulled in....

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#40 2020-11-28 19:13:58

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

Re: Gravity Energy Storage

I have been surveying the property to see what sort of potential energy can be created with use of water.
The slope of the back yard is a pizza slice shape where the crust is the high side of the yards flat area. The left side of the property is at a different slope rate when compared to the other but they both meet at the stream that cuts across the corner.

The right side of the pie is might be 120 feet down the line or longer and is about 20 feet down. When the crust is about 100 ft.
I could create a tank reservoir at the crust location back towards the well in the shape of an L which could be 20ft on the short side of the L and 10 ft on the long side  all being 5ft deep to give a volume of collected water the go down the slope ending up in the stream.
That gives a collective 8,000 cu ft of water stored or 4,000 based on refill rates  or 2,000 if only half the rate to refill for daily use with head for use at any rate of release. But the release rate as it goes up so will the capacity hours for making energy.

https://www.inchcalculator.com/convert/ … ubic-foot/

Right now the level of water in the well is at ground level with some times in the year it flows out the top of the well cover. This along with roof rain water and other such collection efforts could feed the reservoir to keep it filled. The daily summer use is 31kw while the winter months its closer to 45kwhr. So for a 24hr period a 2 kw generator is enough to supply power when net metering and not storing the energy in batteries but into the grid for later draw out.

The well refills at a slow 2 gallons a minute but lets set the level to just 1 gallon for the power generation use. The trough could zig zag or go straight line depending on what can be done for the water wheel size or for any turbine type that could be built to create power.

The alternator or generator heads can produce that power level but they need to turn the shaft at 3600 rpm typically which is not how fast the turbine or water wheel will turn so we need to do a ratio of turn to increase the speed to the shaft to make it work as well.

So what do we have going for the project is free water with no energy expended to receive in the reservoir, a slope that is some what promising but need experimentation in order to prove out for the power levels required and it would be for the most part a zero cost for the energy yearly if we watch the usage level.

Seems it can be done...

https://www.backwoodshome.com/design-ca … terwheels/

http://www.anliatec.com/product/micro-h … m-2kw-5kw/

Water wheel imgaes19small.jpg

http://www.top-alternative-energy-sourc … esign.html

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#41 2020-11-29 09:44:13

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

Re: Gravity Energy Storage

For SpaceNut re topic and post #40

Thanks for the research you have done, and for the image of a home-sized water wheel power generator.

I was inspired to ask Google what (if anything) has happened in the gravity storage field since the last time I looked. 

To my complete surprise, ** this ** showed up at the top of the results ...

http://www.stratosolar.com/gravity-energy-storage.html

The author claims 85% efficiency grid to grid

The kicker is the use of a balloon platform to hold the weights.

Someone was ** really ** thinking outside the box !!!

Because the atmosphere of Earth is constantly moving, a platform of that size could hold wind turbines to augment the supply coming from the grid.

Balloon suspended wind turbines is not a new idea, and "flying/kite" systems would fall into the same category.

** This ** is the first time I've seen balloons suggested to hold dead weight.

Oh ... looking more closely ... the entire surface of the balloon platform is covered in PV panels.  That ** is ** more elegant than wind turbines, but of course it only works during the day.

I'll be interested in any comments that might come in from our registered members.

__8405931_orig.png

(th)

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#42 2020-12-16 14:37:14

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

Re: Gravity Energy Storage

copy of post for topic

Calliban wrote:

Megapower: mining and lowering rocks from high mountains to convert gravitational potential energy into mechanical power.  This was actually used at a slate mine close to where I live in the North of England.  The railway that transported the mined materials to ships on the coast, were powered by gravity.  Additionally, the descending fully loaded carts, pulled the empty carts back up the mountain.  So no external power supply was needed for transportation of the mined materials.  This reduced energy consumption of the transportation and reduced the capital cost of the railway.

I have never heard of this being used to deliberately produce excess energy.  A tonne of material dropped from a height of 2km on Mars, would release some 7.5MJ of energy.  That isn't much energy  - about the same as released from burning half a litre of diesel in an engine.  To harness it, you must run a mining operation and have a circular railway running up and down a mountain.  Lots of embodied energy and a lot of capital equipment.  It would appear to make sense however to use gravity power in planned mining operations  - using the gravitational potential energy of the ores to both power their extraction and deliver the materials to their processing facilities.  This would only be practical if there is a difference in height between the two.

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#43 2021-01-17 10:09:47

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

Re: Gravity Energy Storage

Void got me thinking about this topic as it was a bad weather day yesterday of rain which means solar would not work and if we did not have a nuclear source or fuel based back up for Mars we would need others to serve as required. Here on earth that means wind, water flowing to fill a gap on a rainy day. Of course any level of power wattage counts for when there is none being produced by the main system and secondary systems including those set up for another function.

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#44 2021-01-17 11:07:32

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

Re: Gravity Energy Storage

For SpaceNut re #43, and topic in general

This is a Todo: item ... For Earth gravity, compute the design elements of a gravity energy storage system for a home ...

A shaft is bored into the Earth for some distance D in meters.

The shaft has a liner of metal (or other suitable material) to prevent collapse due to hydrostatic pressure caused by ground water (on Earth)

The liner has thickness T and inside diameter of ID

A weight is suspended over the opening into the shaft with sufficient mass to generate (arbitrary performance) 14Kw of electricity when released.

The weight has a mass of W in metric tons

The electrical system must be defined to produce electricity at the specified rate while the weight is descending.

Movement regulatory subsystems will be needed to insure the movement of the weight is precisely controlled to insure the production of energy is even.

The generator subsystem needs to be capable of serving as a motor to restore the weight to the top of the shaft using utility power after an emergency.

The time of operation of the system is (arbitrarily) specified as 24 hours.

In practice, an actual home power load would be less than the maximum, so the actual outage coverage time will be greater than 24 hours.

If the homeowner is careful, a system such as the one described might last a week.

(th)

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#45 2021-01-17 11:52:03

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

Re: Gravity Energy Storage

volume-cylinder.png
https://www.wikihow.com/Calculate-the-V … a-Cylinder
https://www.gigacalculator.com/calculat … ulator.php

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

generator type for the working fluid determines inlet rate from the volume

This is also where we get into how much power wattage can I get for how long of a duration before refilling the volume.

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#46 2021-01-17 13:40:40

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

Re: Gravity Energy Storage

For SpaceNut re #45

Thank you for picking up on the vision of a home gravity energy storage system.

There is a slight/small difference in how we are seeing this.  Both seem quite feasible.

As I understand your vision, the home storage system would consist of a column of water.  The engineering of that would be interesting.

What I had in mind is an elevator concept, similar to a tall building elevator, except designed for a vertical drop from the surface of the planet.

In the "tall building" version, the weight would be supported by a cable.  In order for the system to NOT have to deal with coiling the cable, I would imagine a small weight on the side of the rotor opposite from the main weight.  This "counterweight" would be sized **just** heavy enough to keep the cable taut as the system takes on energy or gives it up.

Could you describe what you have in mind for a water based system? 

(th)

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#47 2021-01-17 14:48:43

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

Re: Gravity Energy Storage

For high storage we need to have a means to dump the contents of working fluid, dirt ect that is coming up with supplied energy then to make use of the stored material as a power creation source we then need to reverse the order to create power. The functions to load, unload at top and then reloading at the top all reduce the stored values out put. The trick is to eliminate those embodied costs for the system. The is where the free energy comes in or in this case unused energy to do the movement function of loading or unloading the materials to a stored location.

The elimination of the starting low to move to a high location is required to increase the out put value of power creation. So what does a Mars mountain top have that we need at the base of the mountain?

If we use water that can natural evaporate to a high source from a day night cycle of concentrated solar and a bend at the top to cause the water to condense you have saved on energy input and it the droplets fall into the top collection tank we then have saved all three free energy inputs from the excess energy pool. Then you turn down the power creation closer to what you are using....

Landustrie-3-1024x744.jpg

The water loop is closed to mars environment and covered where needed to aid in heating or cooling by the natural mars temperature cycle.
The fall of water from the reservoir at the top to the bottom Caliban outlined with a tube and turbines along the path such as the Archimedes' screw which has the shaft on it connected to a generator to make power. All that is done at the top is have a gating flow rate door to control the time of power creation for the rate of flow volume held by the reservoir. Capture of the water at the bottom is into a holding low depth basin that is heated to cause evaporation to happen to bring it back to the top by sun light and by reflective concentrating of it on the water we have there. The bottom of the area is colored deep black to aid with the water absorption of heat.

Right now I am in a hold until I understand size of the screw to volume of water flow rate for fabrication and volume of water to hold at elevation to enter the system for a residential use. I am also looking at whether there is a benefit to multiple drops or a continous one along the rise with hold volume areas to power continous levels.

Elevators use a single pulley and a wheel that is motorized to bring it up or down and going down is the crash at the end if we are near free fall of the mass being brought to the bottom where the travel from high to low produced power. Another type simular would be a 4 point contact to the elevator box in that 3 corners are slide shafts where the third is a gearbox motor assembly which is still subject to the same pitfalls of slamming into the bottom.

A00Y_1_20130826157883022.jpg
The version with weights is more like a cuckoo clock method of creating motion of the pendulum that meters the energy released in each swing to create internal motion. In this case the wheel that moves the shaft of the generator makes use of imbalance created by filling at the top and empty lifted back up with the gating of drop speed being controlled by the pendulum device.

The cylinder would be more like the hydrogen tank for using a weight column to cause gas displacement by water moving from the filling tank into the lifting expansion areas the inlet pressure causes the second cylinder to lift. One would then shut off the incoming source gas and then add mass to the expansion lift displacement to force the first to increase pressure to force it back out to be used in a turbine. The working gas can be anything that will compress to cause a pressure rise.

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

https://www.theamericancuckooclockcompa … oo-clocks/

cuckoo clocks. They are gravity powered by two or three cast (usually pine cone) weights, as they have been since the first known cuckoo clock appeared about 1740, with their time-keeping regulated by a pendulum.

How does a cuckoo clock work?image.png

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#48 2021-11-11 13:57:13

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

Re: Gravity Energy Storage

tahanson43206 wrote:

Gravity energy storage has been discussed at some length earlier in the forum archive.

I'd like to (try to) renew the discussion with a challenge to our members gifted with numbers skills, to work out the specifications for a vertical shaft gravity energy storage facility for installation on the property of private home owners.

I would like the system (shaft/weight/generator-motor/cable) to be able to supply 2 Kw for 24 hours.

The model I have in mind is the Kohler/Generac systems I see in stalled in the neighborhood.  These are fitted with automatic cutover junction boxes that interface the generator with the home and with the local utility service.

The neighborhood systems (that I know about) all use natural gas as the energy storage medium, since natural gas is abundant locally.

A gravity storage system would be independent of fossil fuel while in operation, but ( I expect ) it would be recharged using fossil fuel.

Here is some data from the Internet (courtesy of Google) that sets the parameters for the specification I am hoping will come out of this initiative.

https://www.inchcalculator.com/kwh-to-kw-calculator/

Home Electrical Calculators Electrical Conversion
    Kilowatt-Hours (kWh) to Kilowatts (kW) Conversion Calculator

Kilowatt-Hours (kWh) to Kilowatts (kW) Conversion Calculator

Convert kilowatt-hours to power in kilowatts by entering the energy (in kWh) and time (in hours) below.
Energy: 50,000 kWh
Time: 24 hours
convert kW to kWh
Kilowatts Results:
2,083.3 kW
Recommended Electrical Tools:

    Multimeter

The requested system would hold more than 50,000 kwh, due to expected playback efficiency (less that 100% due to losses)

While the energy is stored, due to the nature of gravity (ie, reliable) there would be no losses.

There would also be no risk of fire or explosion due to stored chemical energy.

The system would be immune to weather disturbances, since the entire installation would be housed in a weather sturdy dome/shelter.

Installation would be more expensive than the Generac/Kohler model, but maintenance expenses would be modest, since electronic control subsystems need to be exercised weekly.  There would be a battery to sustain the system when power is lost, so that would need to be replaced every four years or so.

There would be no oil change or spark plug replacement required, although the bearings in the shaft would need periodic checking.

It should be possible to build a rewarding and near-permanent business on this concept.  The existing Generac/Kohler systems I see locally are all supported by long term companies who provide annual or as-needed service.

Update: I asked Google if there are any companies already providing gravity energy storage (other than water systems).

https://gravitricity.com/

This company appears to have a working above-ground demo unit, and appears to be studying use of a coal mine for below ground storage.

The following was submitted to the Contact Form:

Does your company have a product for home power backup?

I'm thinking of Generac and Kohler as examples.

These systems depend upon natural gas (or propane) to provide emergency power backup.

They include electronic and electrical subsystems to interface between utility power and the home or small business.

Storage I have in mind would be on the order of 50,000 kwh, with the ability to supply up to 2 Kw for 24 hours if necessary.

The installation would be on the property of the home owner, and would be entirely below ground except for a small hut/dome/covering on the surface.

Both Generac and Kohler would be likely partners in the US.

If you are interested in interacting with a small group of (reasonably) knowledgeable folks, you are welcome to apply for a membership in the NewMars.com/forums.

I am a moderator there, and provide membership admission services at newmarsmember@gmail.com.

We have members in the UK and the US, Canada and Mexico, as well as Italy and (probably) other locations.

(th)

(th)

You have just run into why creating to many topics is part of the issues for developing information into useful products as the post just above this is similar to this one.

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#49 2021-11-11 13:58:22

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

Re: Gravity Energy Storage

reposting computations

edit
calculator
https://www.inchcalculator.com/convert/ … -to-joule/

Calliban wrote:

2kW for 24hours is 48kWh = 172.8MJ.  1kg raised 1m = 10J.  Let's us assume a 3m raise.  That's 30J/kg.  Concrete bound granite rock has a density about 3000kg/m3.  So 1m3 raised by 3m = 90KJ.  The total volume of rock needed would be just shy of 2000m3, or a cube 12.4m aside.  A lot larger than an average house and not very easy to achieve.

Gravity hydraulic accumulators like this are useful for the more modest task of power smoothing.  Let's say you have a crane or other device that requires large amounts of power for very brief periods.  A hydraulic accumulator is a good way of allowing a power source that meets average power requirements to cover very large but short term peaks in power demand.  In a workshop, there may be pieces of equipment that draw several kW, but will only run for a few minutes, with a long time between cycles.  The average power of the workshop is only a few hundred watts but peak power is in kW.  The hydraulic accumulator allows a small power source providing a steady power output of a few hundred watts, to meet peak loads measured in kW.  In the house, a washing machine may run for an hour consuming a couple of hundred watts to power the drum motor.  But at the end, there are spin cycles lasting minutes, that will need power levels of a few kW.  Hydraulic systems are very good at delivering modest amounts of total energy at very high power, for short periods.

Another way they might be useful: you have a base load of a few hundred watts within a building and variable peaks in power above that.  You power the building using a wind turbine, with a peak capacity about 5 times average load.  Excess power is stored as heat used for water heating.  When wind turbine power falls below base demand, a DG starts.  However, it takes time for the DG to start and accelerate to load.  The hydraulic reservoir can be used to reduce the slew rate of the wind turbine, allowing sufficient time for the diesel to come online.

tahanson43206 wrote:

For Calliban re #6 ... thank you for picking up on this new line of inquiry!

Thanks for working out the numbers for a 12.4 meter cube that would operate over a distance of 3 meters.

I am going to take the risk of (trying to) estimate what the numbers would be for a home owner.  The footprint I have in mind is 3 meters square on the surface, and ideally no more that a meter above the surface (for maintenance/inspection etc).  The size of the pipe in that case might reasonably be given as 1  meter in diameter  (for ease of computation.

Starting with your numbers: 12.4 meters on a side for the mass and a distance of 3 meters elevation

The volume was computed as

2000m3,

A cylinder one meter in diameter with a volume of 2000 m3 would have a depth of:

Consulting Google:

Right cylinder
Solve for height
h

2546.48 Diameter
   
Unit Conversion:
Using the formula
V=π(d2)2h
Solving for h h=Vπ(d2)2=2000π·(12)2≈2546.47909

That's interesting!

Now, if we stay with your estimate/scenario, the movement of that cylinder would be 3 meters over a 24 hour period.

Now I'm hitting a wall .... By extending the distance to be traveled by the cylinder, we could reduce the height of the cylinder.

There exists (I am reasonably confident) a sweet spot where the depth of the bore hole and the height of the cylinder are optimum.

I'm hoping you (or someone) might be willing to see if you can compute that sweet spot.

My (admittedly wild) guess is that calculus could solve that problem, although some dimly remembered algebra might be able to find the sweet spot.

What I do NOT know at this point is whether there is a sweet spot where the costs are competitive with the costs of a Generac or Kohler system of comparable power.  In this case, the amount of natural gas or propane consumed would (presumably) be similar, since the weight has to be "charged" (at present) with fossil fuel.

The whole point of this exercise is to try to find a way to provide emergency power that ** does NOT ** depend upon utility supply of natural gas, or a propane tank topped off and waiting for an emergency that may never come.

(th)

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#50 2021-11-11 14:34:23

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

Re: Gravity Energy Storage

This is line with the clock towers with a church steeple as well

https://commons.princeton.edu/motorcycl … paper2.pdf

http://www.my-time-machines.net/speech_final_web.pdf

compound.gif

Amplifying length would be done with more pullies
12fall.gif
https://www.model-engineer.co.uk/forums … 116604&p=7

9RKS1_j9gpJjlVkjkpDyGl3PJJl3BQ3XmkjWvY_l853rJ88Kwx1I8b72Q81M5K6f1MDchnYnStfJ2yDQweZhhK9euQTuYm03ME-dQA

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