Frequently Asked Questions

We are adding question and answers almost daily. If your query is not answered here please contact us using our enquiry form.

Q. How can I measure the Head on my proposed hydro system?

A. For our Pelton and Turgo turbines you will be measuring the vertical distance between the turbine and the entry point of the penstock pipe. If this is a considerable distance possibly over difficult terrain, an altimeter can be used. Simply set the altimeter scale to read zero at the turbine and then read off the height in metres or feet at the penstock inlet. If the terrain is easier then you can use a surveyor’s level although it may take some time with a 4 or 5 meter staff. Alternatively, if both the turbine and the penstock inlet are visible, you can use an inclinometer to determine the gradient and a tape measure to define the distance between both points from where it is a simple bit of trig to calculate the vertical distance. Alternatively Google Earth can be used. Simply hover your mouse each point in turn and note the altitude reading given in the bottom right of the screen. This might have an error of 5 - 10% but it is generally good enough for an Initial Viability Survey.

For our Low Head turbines the Head is the vertical distance from the turbine propeller housing to the surface of the water below the turbine location. Typically this will be between 2 and 5 metres and can simply be measured with a spirit level and tape measure.

Q: How can I measure the flow in my stream?

A: If you have a point at which at least, most of the water is flowing over or through a small gap the the easiest way is with a large bucket and a stop watch. If you have a 20 litre bucket and it can be filled in 5 seconds then your flow is 4lps. To get the best accuracy then use the largest bucket you can and take at least 3 measurements per occasion and average the results. If the size of your stream makes this method difficult then you may be able to find a length of the stream, either up or downstream which is at least 15 metres long and relatively uniform in its width and depth. Measure and calculate the cross-sectional area of the stream and then record the time it takes for a piece of wood or an orange to travel the measured distance. Make sure you through the float into the stream upstream of the measuring area so that its speed is stabilised with the water flow by the time you start measuring. This method is not as accurate as a bucket because the water passing through the area will be moving at different speeds though out its depth so a correction factor is needed. Multiply your result by 0.85 if the stream has a rocky bottom or 0.9 if it is smooth.

There are many other methods using V-notch weirs and sophisticated measuring devices but whatever you choose it is important to be consistent and detailed in your records. Recording both rainfall and stream flow on a daily basis over 12 months is an onerous task but will ensure that your system is designed correctly.

Q: If I live in the UK do I need to get planning approval and Environment Agency licences to install my hydro system?

A: Yes. However, if you decided not to we would rather not know.

Q: I have a large roof area on my house and could get all of the rainwater to come down one pipe. Would I have enough to power a turbine?

A: Even if your house was the size of Wembley Stadium it is rather doubtful, and in any case you would have no water when it wasn’t actually raining.

Q: How long will it take to get the necessary consents from the Environment Agency (In Wales they are called Natural Resources Wales)?

A: I have a piece of long string somewhere. (3 to 12 months is not uncommon)

Q: After measuring the flow in my stream for the last 12 months I can see that I have a very wide variation between Winter and Summer. How do I design a system to cope with this?

A: If your head and flow were sufficient and you wanted to maximise your Winter generation then you can install as many as 10 individual turbines all of which would be running in the Winter period with perhaps only one or two running in the Summer. Changing nozzle sizes or using adjustable nozzles is a way of accommodating flow variation on single turbine sites. Many PowerSpout installations (including our own) generally run for 8 - 10 months of the year and are turned off in high summer when we rely on solar PV for our energy "fix" rather than water coming off our mountain.

Q: How important is it to screen the inlet?

A: Essential. Without effective inlet screening the turbine may become blocked especially in Autumn when leaves are falling or after periods of heavy rain when more debris is washed down.