Site the powerhouse at the lower end of the penstock on stable ground with its floor at least 0.5 meter above the highest flood you can identify, and as close to the loads as the head allows. Distance costs power through the cable: a 700 W plant at 12 V carries 58 A, which would drop 50 V along 100 meters of 4 mm² copper, while at 120 V the same cable drops only 5 V.
Part of Micro-Hydro Turbine
The powerhouse is the shelter at the foot of the penstock that holds the turbine, generator and controls; its position trades head, flood safety and cable length against each other.
Three Constraints Pull In Different Directions
Head. Every meter of fall you give up in the building’s floor level is a meter off the head. A Pelton wheel runs in air, so its housing must sit above the tailwater, and the clearance is lost. On a 30 m site, 0.5 m of clearance costs 0.5 ÷ 30 = 1.7%; on a 10 m site the same 0.5 m costs 5%. A low-head site cannot afford a high floor, so on one the floor level is a direct trade against power.
Flood and ground. The Installation page sets the powerhouse floor at least 0.5 m above the highest flood level you can identify, with floor drains for leakage, anchor bolts set in concrete before the floor is poured, and a bedplate levelled to within 0.5 mm per meter. The carrier adds a concrete or stone pad for vibration stability. The Penstock Design page warns against slopes prone to landslide. Look for the flood evidence the same way as for the dry flow: debris lines on the bank, and the memory of people who have lived by the stream.
Distance to the loads. The next section explains why this one decides the voltage you choose.
Cable Loss Sets The Maximum Distance
A cable has resistance, and a current through resistance loses power: loss = I² × R. For a run of 100 m, the conductor length is 200 m, out and back. Copper has a resistivity of about 0.0172 Ω·mm²/m (a recalled handbook value), so R = 0.0172 × 200 ÷ area in mm².
| Voltage | Current for 700 W | 4 mm² copper: R | Voltage drop | Power lost | 16 mm² lost |
|---|---|---|---|---|---|
| 12 V | 58.3 A | 0.86 Ω | 50 V | 2,926 W | 732 W |
| 120 V | 5.83 A | 0.86 Ω | 5.0 V | 29 W | 7.3 W |
| 230 V | 3.04 A | 0.86 Ω | 2.6 V | 8.0 W | 2.0 W |
At 12 V a 700 W plant carries 58 A (58.3 A before rounding), and a 100 m cable of 4 mm² cannot deliver the power at all, since the voltage drop is larger than the supply. Even 16 mm² copper dissipates 732 W, more than the plant makes. At 120 V the loss is 29 ÷ 700 = 4.2%. The loss falls with the square of the voltage: ten times the voltage, one hundredth of the loss. Putting the powerhouse beside the battery bank and loads lets a 12 V system work; a village scattered along a valley needs AC at line voltage. See Battery Charging vs Direct AC and Conductor Selection.
The Building Must Shelter, Drain And Leave Room To Work
The carrier asks for a small shelter that protects the equipment from weather, gives room for maintenance and handles the discharge without flooding. Beyond that:
- Keep the electrics above the flood mark even if the turbine pit is not.
- Leave a walking path round the machine wide enough for a person to stand clear of the belt (Generator Coupling (Belt vs Direct)).
- Plan the tailrace first. The tailwater cannot back up into the runner (Tailrace & Environmental Flow).
- Make an access route that is open in a flood and in frost; the flood is when the penstock is most likely to need an inspection.
Common Mistakes
- Placing the powerhouse at the lowest dry spot — it can be the line the flood water takes.
- Locating it far from the village at 12 V — the cable loss exceeds the output.
- Pouring the floor before setting the anchor bolts.
Safety
Electricity and floodwater in the same room
A powerhouse that floods while the generator is live puts a shock hazard in the water. Mount the panel and wiring above the highest flood mark, fit circuit breakers (Circuit Breakers), and shut the intake gate, which is the stop, before anyone enters a room with standing water. At 120 V or 230 V the supply can kill; follow Electrical Safety.
What’s Next
- Learn next: Tailrace & Environmental Flow for the water leaving the building
- Combine with: Generator & Electrical for what goes inside it