Creating Mini Pumped-Storage Power Plant with Windmill for 100kWh Storage: Cost & Feasibility

Have any of you ever thought about making a mini pumped-storage power plant powered by, for example, a windmill/windmills? I wonder what the cost would be? Let's assume that the household consumes about 500 kWh per month. We would like to store 100kWh to have a supply for 6 windless days. Less than 2000m3 would be enough, i.e. a tank of 20m x 20m x 5m and a difference in levels of 20 meters. I think that if you have a plot with a difference in levels, it is feasible. Of course, purely theorizing, I am unable to calculate the costs of building such reservoirs, turbines, etc. If something like this could be built, it would be practically 100% independent of state energy.
What do you think about it? Is it real somehow?

The level difference of 20 meters on one small plot (even on a large plot) is huge. The cost of digging such a reservoir is about PLN 4,000, completely unprofitable in my opinion.

PLN 4000? then see:
The cost of the energy that is there is PLN 50, it seems not much ... But assuming that you will recover it 100 times a year, it is already PLN 5,000! After 10 years, you have PLN 50,000. After all, energy will become more and more expensive over time! However, if you wanted to use chemical batteries, then in order to have the 50kWh, you need to use about 16 batteries, 250ah each, which with accessories, etc. will cost a minimum of PLN 20,000. And such batteries after 10 years are in the trash
I wonder what the rest of the cost would be. I think that if they do not exceed PLN 50,000, it pays off. After all, it is always the case that the cost of one KWh will be smaller the larger the investment. So someone may need more energy. As for the plot, there are certainly people who have plots in such a location!

Are they available in mini versions and in some affordable prices of turbines that can be used to pump water, as for example in Żarnowiec?

The energy balance must start with the windmill.
Do you want to store 100kWh, in what time? a dozen hours?
In Poland, wind statistics are not very favorable: winds of 10m/sec and more, there are only a few dozen hours a year (for calculations, I assume 100). Such wind is able to transfer the power of 15kW to a windmill with a diameter of 10m.
Unfortunately, winds with a speed of about 4m/sec (this is the average for Poland for favorable areas) are statistically about 3000 hours a year, and at this speed such a 10-meter windmill will give only 1kW.
You can't count on even weaker winds, there are (together with silence) about 5,500 hours a year, and the wind of 2.5 m/sec in your windmill will give only 230W, it's rather a laugh ...
So the total energy that such a windmill will give you is (100x15) + (3000x1)=4500kWh.
If your energy consumption is 500kWh per month or 6000kWh per year, then such a windmill will not cover all the demand.
The solution is to build a tower windmill at a height of e.g. 30m, where the wind balance is 50% more favorable, but the cost of the windmill will be much higher, for rough calculations it is assumed that a 1W installation costs 2 euros, so 15kW is at least 30,000 euros.

Wind energy is free, but access to it is expensive. Just like in the cinema: you watch for free, but to enter - you pay for the ticket.

Building wind farms "everywhere" makes as much sense as building gold mines "everywhere", and not where the gold content in the rock is so high that the value of the ore is higher than the cost of extraction.
Denmark has a much better balance of winds than Poland, and California has many more hours when the sun is warm, no ambitions of ours will change that.

By the same token: a tram is more economical than a car, but that doesn't mean that we should commute to work in our private trams, even if they only have 5 seats.

I was thinking of a windmill or two with a vertical axis of rotation installed on a 15-meter lattice mast. You have one that is quite cheap to produce, set up, etc. Besides, windmills with a vertical axis of rotation work with much weaker winds and are more resistant to very high winds.
Besides, nobody talks about building something like this everywhere, only about the sense or lack of sense of the project itself... I'm not saying that I want to do something like this, I'm just interested in this topic from a theoretical point of view.
Anyway, thanks a lot for the honest answer

There is only one more observation.
If I have a plot of land with a 20m hill and I will build a 10m windmill on that hill...
I have a windmill 30m above the ground and it costs me as much as 10 meters.
An additional sense can be seen in the ability to control the power of the power plant. I collect electricity as it blows and use it as needed. By default, the wind blows when it wants and electricity is needed when there is no electricity.
The cost of installation will also be reduced by the lack of need to connect to the public network (we will not sell electricity, we will only produce as much as we need).
Unfortunately, this carrot also has a stick. Automation must be "on the level" power demand in the household changes quite dynamically and our power plant must keep up with it (do not choke at load increases and do not spin up at decreases).

Nom on this hill you can still hit 20 meters or more to have more wind stability. Then we come to the 50m that my friend said.

The problem with wind energy is that a turbine is built for the winds that blow most often (4-5 m/s), and the structure must withstand 4-5 times stronger winds (storms). The forces acting on the structure are then 16-25 times greater. This entails significant costs.

With wind it is even worse, wind energy increases to the third power of speed, so for 4x more wind pressure is 56x greater.

narek 1!
Your calculator is broken or the batteries are dead.
4 to the power of 3 is 64.

This load increase is not that simple (typical x3 wind and cleaned up).
Unfortunately, during extreme conditions, the wind is not only fast, but also quickly variable, both in terms of speed and direction. Calculations for fatigue and dynamic loads bow.

Having a miniature pumped-storage power plant, you can earn money on it 365 days a year, and not be limited to 100 windless ones.
You can set up a two-zone meter and take electricity at night, and use it, for example, to pump water to a higher tank.
At night, electricity is much cheaper due to differences in daily consumption.

During the day, pick up with a turbine.
Of course, we will incur 25-30% losses. But we will still have cheaper energy.
Having, for example, a factory, you can afford 2 and not one fire protection pools.
located at different heights.