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: 12:47, 10th Mar 2008
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