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My interest is with small scale hydros of up to about 125kW. So comment below are based on that knowledge. Others with knowledge of high power hydro schemes may wish to add to comments below.
My gut feeling is as follows. Good that you have distribution system. This suggests that a central power generation is way to go. It is technically possible with hydro. However it would be too complicated and too expensive for hydro compared to better insulated houses (to keep heat out and cool in) and big PV array (as long as you have the space) with battery storage (buffer and night time) with existing generators as back up. You should note that I am not a PV expert so it would be good for a PV expert to also respond to your question. Maybe you should ask the same question but focussed on PV as a solution to attract responses from PV experts.
On the 'hydro power from borehole/well source of water' question there is no technical reason why you could not produce a balance of electricity as long as the turbine was located at a level that was well below the drawdown level of water in the borehole/well. In your case you would need to pump water up (before allowing it to gravity feed down). You would probably need some sort of buffer holding tank on the top of the hill. Due to efficiency losses you would need more power to pump water to the top of the hill than you would gain from hydro power to get water down to the same level of the drawn down water in the borehole/well. If you were able to tunnel in horizontally to the water table then you would not have these same losses.
So, stating the obvious) your power balance would be total hydro power produced minus the power to get the water to the top of the hill/hydro pipe.
The rule of thumb for 'normal' hydros is about US$10k to 5K per kW of power. This probably holds true in you case. Maybe much higher than the US$10k mark because of the borehole/well/pumps. So if you are looking at a 1,000kW output then expect it to cost at least US$10 million, probably more.
You also need to consider the quantity of water that you would need (to give idea of borehole and pump sizes) Basic calculation is: kW = [residual head (m) x flow (lts/sec) x 9.81 (gravity) x 0.75 (efficiency guestimate)] / 1000
If borehole/well is expected to be 250m deep then i suspect that the drawdown would also be quite a long way down. In brought terms what is the height difference between the position of the turbine and the drawdown level of water in the well?
Let's assume the height difference between draw down level in borehole/well compared to position of the turbine is 100m. The pipe you choose would need to have about a 5% friction head loss at peak flow. So residual head would be about 95m.
So to get say 1,000kW you would need about 1,400 lts/sec of water (big borehole, big pump). Power, height and flow are on a 1:1:1 ration. So if you can double the available height then you can half the required flow, if you need twice the power then you need to double the flow or height, etc...
What every technology you use will require level of expertise. Is there hydro expertise in the country? PV is obviously a good balance with the abundant sun even if they need to be cleaned.
Since you have the power distribution network set up then it does make sense to have a centralised power plant. At this stage i am just not sure that using a borehole/well as source of water for hydro is, in your case, the right solution. If you have the space then a PV array might be more appropriate. Spending money on home insulation will always be a winner.
Obviously i do not know the full context of your situation. The above makes some very broad
assumptions. I am happy to continue discussions if it would be of help.
Feel free to e-mail me on: NGWHydro01@gmail.com