I'm thinking about building a cheap DIY hydro energy storage (like a battery) system. I can build it but so far I can't really figure out the calculations to validate my idea and where to start mathematically.
I'm considering doing a small test with two equally sized water containers. To store, pump water up, to regain the energy, let it flow back down.
The main question is How to determine the efficacy and potential energy of hydro power energy storage? But below are some sub questions I came up with that I think need to be taken into account.
For this I wanted to start small with two 220 liter tanks with the dimensions of height 108cm / diameter 57cm / opening diameter 37cm as shown below.
Later I could consider using two IBC containers of 1000L instead of 116cm height / 120 cm width / 100 cm depth. as shown below.
My plan is to stack them on top of each other (within some frame). Either directly on top of each other or by digging in the lowest tank and elevating the highest tank with a range between them of 0-3 meters in between. I suspect the further elevation contributes to a higher water pressure.
I would like to know what the ideal location would be to let the water flow out and if the angle/position of the tank matters.
The pump and generator
I did not choose the pump yet but considering a given (I guess) the flow rate of the pump, efficiency (loss) percentage and power usage. I would like to know: How much power (watt hour) and time would it take to pump all water from the lowest tank to the highest tank?
Same for the generator. Considering a certain volume, generator flowrate, maybe pressure, efficiency height and or pipe diameter sizes: How do I determine the right values for this calculation, what calculation do I use to determine how much power (electricity) in watt hours I could potentially regain from letting all water flow back down from the upper tank and how much time that would take?
With those two values, obviously I want to determine the approximate efficacy of the system, the potential loss of power, how much power to use to fully "charge" and how much power to regain to fully "drain".
Perhaps the most important question. How do I determine the optimal pipe path (spiral down/straight or diagonally downwards), pipe diameter, pipe length, nozzle size (reduction size or ratio), distance from nozzle to generator blades, to increase pressure as much as possible? Assuming higher pressure results in higher RPM of the generator, results in higher output.
I'm planning to use 23.3% saline water with a freezing point of -21.1C. I asked a related question about that here: Can saline water be used in a hydro storage system and would the ambient temperature or higher liquid viscosity affect performance?.
I guess above (sub questions) need to be taken into account for a realistic calculation.