# Calculation of Hydro Power

# Calculation Of Hydro Power

## Work out how much hydro power can be taken from flowing water with our new online automatic hydro-power calculator

hydro | educationBefore embarking on any

**hydro power**generation project it is essential to survey the proposed site to calculate the amount of available

**hydro power**.

The two vital factors to consider are the

**flow**and the

**head**of the stream or river. The

**flow**is the volume of water which can be captured and re-directed to turn the

**turbine generator**, and the

**head**is the distance the water will fall on its way to the generator. The larger the flow - i.e. the more water there is, and the higher the head - i.e. the higher the distance the water falls - the more energy is available for conversion to electricity. Double the flow and double the power, double the head and double the power again.

A

**low head**site has a head of below 10 metres. In this case you need to have a good volume of water flow if you are to generate much electricity. A

**high head**site has a head of above 20 metres. In this case you can get away with not having a large flow of water, because gravity will give what you have an energy boost.

The key equation to remember is the following:

**Power = Head x Flow x Gravity**

where

**power**is measured in Watts,

**head**in metres,

**flow**in litres per second, and

**acceleration due to gravity**in metres per second per second.

*The acceleration due to gravity is approximately 9.81 metres per second per second - i.e. each second an object is falling, its speed increases by 9.81 metres per second (until it hits its terminal velocity)*.

Therefore it is very simple to calculate how much

**hydro power**you can generate.

Let's say for example that you have a flow of 20 litres per second with a head of 12 metres. Put those figures in the equation and you will see that:

**12 x 20 x 9.81 = 2,354 Watts**

## Real World Hydro Power Calculation

So in the example above a 12 metre head with a 20 litres per second flow rate equated to just over 2.3kW of available power. Sadly it is not possible to tap all of that power - nothing is 100% efficient. However,**hydro power turbine generators**are very efficient when compared to

**wind turbine generators**and

**solar panels**.

Efficiencies of around 70% can be expected which is to say that 70% of the

*hydraulic energy*of the flowing water can be turned into

*mechanical energy*spinning the

**turbine generator**. The remaining 30% is lost. Energy is again lost in converting the

*mechanical energy*into

*electrical energy*(electricity) and so at the end of the day you can expect a complete

**system efficiency**of around 50-60%.

In our previous example where 2.3kW of power was available - we can therefore expect to generate around 1.1-1.4kW of electricity.

These same calculations are valid whether you are planning a tiny Pico or Micro Hydro Power system or the next Three Gorges Dam Hydro Project.

Find out much more about

**hydro power**by clicking here and viewing our Hydro Power Directory. We also have an

**Introduction to Hydro Electric Power**, and information about the most common (small scale)

**Run of River Hydro Power**systems.

**Waterwheels**are introduced here.

Article Last Modified: 23:20, 24th Sep 2014