Effectively Get off the Grid

Effectively Get off the Grid

Ok. First. Let me just say that I'm all for the grid and I think it's needed for most cases. However. If you're looking to get off, is not a water tank + smaller battery.

Here's my thought:

Typically when your solar array is not being used by your home you feed your power back to the grid. Great. But what if you used it to pump water (from a well) into a water tank/tower that is hooked to a turbine. This turbine charges a battery that holds a constant source of power for the home.

Someone debunk this from a physics perspective. I don't understand why you can't have power 24hrs a day with instant kinetic energy from a gravity fed water turbine.

Brian H | 22 marzo 2014

Possible, but there are inefficiencies at every step. Why not use batteries instead? Likely much less expensive and space-wasting than a water tower.

Bikezion | 22 marzo 2014

Check this out,
Not the same thing, but the principle applies.

ztayl | 22 marzo 2014

@Bikezion Thank you! Exact same principle I had in mind. All batteries have a storage capacity and shelf life. Resivoirs? Not so much. I would expect to see this at more people's homes. Uninterrupted power supply off the grid. A thing of beauty.

Brian H | 22 marzo 2014


They also require maintenance, and filling them is very lossy. "energy efficiency varies in practice between 70% and 80%" That's with a large regional resource, using landforms. Not similar to private setups.

jkn | 23 marzo 2014


To store 85 kWh you need 100 m high tower with 312 ton water tank or 10 m high tower with 3120 ton water tank. If you need heat energy, you could store heat into material with suitable melting point.

dutchstew | 23 marzo 2014

I just watched this interesting video on a solar array

It is certainly better than a coal power station but still aesthetically unappealing.

Can we not have visually pleasing and environmentally harmonious energy generation?

Is it not possible to either use existing lakes or artificial lakes that absorb the heat of the sun that generates a current flow that feeds a giant underwater electrode that then feeds into the grid.

The lake could be a nature reserve at the same time.

This is just a starting point, the salt content/formula of the water could be optimised along with heat absorption facilitation etc.

muleferg | 23 marzo 2014
muleferg | 23 marzo 2014
Dramsey | 23 marzo 2014

It's possible, but not really feasible for most folks once you start looking at the math. The trouble is that you need a LOT of water movement to generate any significant amount of power.

This company offers a system to do exactly what you want. However, the power outputs are minuscule: a $1,400 water turbine is rated to produce only 100 watts of power, maximum. So you're not going to run a refrigerator or air conditioner or really much of anything without tens of thousands of dollars' worth of these turbines.

The prop diameter on the turbine is 12", and it needs water moving at more than 1.8 meters/second to generate full power. So every second you need a cylinder of water 1.8 meters (70 inches) long and 12" wide flowing past the prop.

The volume of a cylinder is pi * r^2 * h, so that's 7,900 or so cubic inches per second. At 231 cubic inches per gallon, that's just over 34 gallons of water per second to generate a measly 100 watts of power. not feasible for home installation, unless you live near a fast-flowing stream or river.

ztayl | 23 marzo 2014

I own a company that has all the equipment necessary for me to do water retention for free. For me and the site I have it makes sense. It won't for everyone.

Frank.B.Smith | 23 marzo 2014

Most communities have water towers that provides the water pressure to the homes. Energy is used to pump the water to the top so why not get some of that energy back as the water is used? In my house most of our water usage is after dark so if you use solar during the day to pump the water up to the tank you will be getting "free" electricity from a turbine as water is naturally used.

tjc7 | 24 marzo 2014

But what if you used it to pump water (from a well) into a water tank/tower that is hooked to a turbine

You've got a great idea. Some R&D and better battery tech and surely it could work.

I'd add what if you used that solar electricity to make hydrogen from water- which is H20- with electrolysis? Storage is an issue but here's a guy (in NJ) that stores it in propane tanks. He was written up in Scientific American.

Inside the Solar-Hydrogen House: No More Power Bills--Ever (2008)

Youtube update (2013):

And here's a guy that uses tanks of Hydrogen made from solar electrolysis to run his car:

Combine all this tech and the US could be energy independent. No doubt.

ZsoZso | 24 marzo 2014

There are other methods that can store power with higher energy density than a water reservoir, i.e. more suitable for smaller sclae such as homes or business / factory level. One example is fly-wheels:

blue adept | 24 marzo 2014


NASA has already accomplished this, embodied in the device pictured in that Wiki link you posted, by circumventing the matter of 'friction' by imposing a vacuum in the chamber in which the flywheel resides and utilizing opposing magnetic and diamagnetic 'bearings' to suspends the flywheels axis.

There IS the small matter of the generated centrifugal force acting upon welds and joints and what have you of the cars' body as it wound and turned its way along its route, going in directions that would place the flywheel in off axis orientations and, possibly, resulting in exerting rending torsional forces upon the cars' body and chassis.

blue adept | 24 marzo 2014


But, if used in a STATIC installation, it would prove VERY beneficial for continuous energy generation as it would NEVER stop because, you know, that whole supposedly impossible "perpetual motion" thingy.

Brian H | 24 marzo 2014

There's a limit to how much you can reduce the water pressure, which is what that rig does.

Boukman | 24 marzo 2014

Have you thought about a compressed air turbine system? It might be a more compact system...

blue adept | 24 marzo 2014


You don't need a "tower", just a pump to accelerate the water flow to a speed that would spin the turbine.

Granted, a "gravity feed" type of water supply system would supply a certain amount of water current, but I don't believe that it would be adequate to spin the turbine to any speed that would serve to generate an appreciable amount of current unless you made use of reduction tubing that would incrementally decrease the inner diameter of the feed tubing/hose/piping over the course of its run, accelerating the water as a result.

Try Googling "hydraulic mining" for some insight on using reduction piping to accelerate water flow.

Brian H | 25 marzo 2014

Compressed air is a thermal nightmare. At high psi, lots of heat to dump when compressing it, then lots of reheating when releasing it (or it comes out freezing, condensing ice all over the works). Fuggedaboudit.
Many other concerns, including explosion and noise (air pistons are LOUD!).

holidayday | 25 marzo 2014

Just: "just a pump to accelerate the water flow to a speed that would spin the turbine."

Then you'd need to power the pump. If you use a pump, then all the power from the turbine would need to power the pump, and you can't use any of the power for anything else.

Gravity gives you "free" energy as it causes the water to move. You know, as long as you didn't have to pump it back up to the tower. :)

Brian H | 25 marzo 2014

That's why dams are built in high mountain valleys. Which are in limited supply, and are a shame to flood and ruin.

blue adept | 27 marzo 2014


Ideally you'd want the turbine to generate more energy than what it took to spin it (the turbine) up (perhaps incorporate an amplifier to boost the output of the turbine), that way there'd be plenty of extra to spin the pump, otherwise, then I guess you're back to using reduction piping/employing hydraulic mining techniques to increase the water's volumetric flow rate?!

Yes, it is something of a closed loop system that I suggest, sort of a perpetual motion system, though you'd also have to recover the water spent on spinning up the turbine and return it to the tower to facilitate that/complete the circuit, but it could be done.

vgarbutt | 27 marzo 2014

Donald Sadaway thinks he has the solution for grid level storage, the liquid metal battery. Its a unique direction. here is his TED talk Link:">


ztayl | 27 marzo 2014

Awesome info. Especially the flywheel. I always knew it was possible until I actually "youtubed" the breakdown on its kinetic energy saving effects. Super neat stuff. I don't understand why it's not more prevalent. Strange.

blue adept | 28 marzo 2014


It's currently under development by NASA with an eye towards off-world applications, e.g., off-world colonies, power generation for space travel and the like...Perhaps that is the reason why it hasn't been more prevalent in media/real world applications, though I am aware of a couple companies who are developing their own versions, so perhaps we'll hear something more of it in the future?

ZsoZso | 28 marzo 2014


If you follow the 2nd link I posted, you can see a couple of large scale installations in Stephenton and Hazle Township. Those are grid-connected systems to help "smart-grid" operation by storing excess production when not needed and helping out during peak usage.

blue adept | 28 marzo 2014

Ah, so there ARE some Earth-based installations already in operation...Nice!