Planing a hydro power system

The information on this pages describes the fundamentals.

Determine your needs:

1. What is your single electrical appliance with the biggest power consumption (kilowatts or kW)?


Examples:
  • An electrical stove with all 4 hotplates and the baking oven on at the same time will draw between 7 kW and 10 kW.
  • A big circular saw will draw between 3kW and 5kW.
Examples of power labels. 2000W = 2kW

If you absolutely must run both of these appliances at the same time with full power, then you need to add the numbers to dermine your total maximum power requirement.
(You can always reduce your maximum power requirement by pushing the wood through the saw a bit slower or not cooking and baking at the same time :-)

2. Check the power capabilty of your water source.

Preparations

Measure the flow speed of your water source.
Needed: stop watch and measuring tape
  • Mark 2 points along the water path
  • Measure the distance between the points
  • Drop a piece of wood into the water at the upper point
  • Use the stop watch to measure the time it takes to reach the lower point)
  • Calculate the flow speed: Flow speed is meters divided by seconds.

Calculate the water flow of your creek.

The water flow can be calulated by estimating the cross-sectional area of the water path, and multiply this with the flow speed.
E.g. cross-sectional area of 0,25 m2 * flow speed of 2m/s = water flow of 0,5 m3/s


Calculate the head of water or penstock

This is the height difference between the water intake and the location of the turbine.
If you don't have trigonometrial equipment available, you can use a spirit level, a measuring tape or builder's rope, a protractor, and some basic geometry from school.
If the penstock is several meters, you can also use an altimeter, depending on the resolution of your altimeter


Calculate the power capability of your water source

The simple formula is: water flow (m3/s or cubic meters/second) * head of water (falling height of the water in meters) * 7kN/m3 = power in kiloWatt.        // assuming a total efficiency factor of the system of 70%

E.g. water flow of 0,5 m3/s * penstock 10m * 7kN/m3 = 35kW

3. Do you need some kind of energy storage?

If your water source delivers more power than what you require, all year round, then you don't need additional batterys or a dam.

However if in the dry season or even all year round  there is not enough water, and you don't want to put up with the reduced power, then you need to store some energy somewhere for the times when you need it (cooking and sawing).
Two possibilities:

a) Batteries

Easy to implement, but batteries are consumables, need replacement, and can get quite expensive if you need lots.

b) Build a dam

Free for ever, but building it can also be quite expensive.
If you build a dam, you will need an Electronic Load Controller which regulates the water flow in order not to waste your precious water reservoir.
The hydrocontrol ELC described on this site can do this.

c) Use a gasoline-powered power generator for the big machines - this really only makes sense if you don't need high power very often.


Note: do not confuse power (kilowatts or kW) with energy (kilowatt-hours or kWH)

Energy is power produced/consumed over time.
E.g. if your system produces 1kW of power, then it will produce 24kWh of energy per day. (1kW * 24h = 24kWh)

A typical household might use anything between 3kWh - 30kWh of energy  per day, depending on heating, number of inhabitants etc.
However the energy usage is not distributed evenly over the day. The peak times are in the morning and in the evening. Low times are in the night.

With a battery system or a dam, you can "buffer" the peak times, while collecting water in the low times.

An intelligent load distribution, which only switches on low priority loads like heating elements if there is enough power, can help you manage limited water availability.
The hydrocontrol ELC described on this site can do this.

Which turbine for which head?

high head > 40m

Pelton
water hits each spoon or bucket separately
cross-flow
the blades direct the water toward the center, the water then hits the blades on the other side again.
Works well if the water flow varies greatly.
Turgo
15 - 300m
derived from Pelton, but spoons are cut in half, the water hits the spoons on the side.
 Francis
water hits all blades simultaneously.
    


low head 10 -40m


Some Models
Kaplan
 Turgo  
 like a francis, but with modified blade shape, like a propeller.
Sometimes blades can be adjustable
   

very low head <10m

Screw turbine


flow of the river

Tyson

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