Hydro - Water Power

What power output is available?

We can supply water turbines from 200W to 1MW

What is the voltage/frequency output?

220v 50Hz single phase a.c. (three phase for large turbines)

Why not low voltage DC?

Because the higher voltage allows you to site the water turbine further away from the house without incurring heavy powerline losses. Also, it allows you to use these turbines directly with household wiring, without the expense and efficiency losses provided by an inverter system. It is of course necessary to ensure that the incoming mains electricity and the turbine-produced electric are kept separate using a changeover switch.

What about load variations?

All of our water turbines come with an integral dump load (or separate dump load, in the case of large machines) connected to a voltage stabiliser circuit. Some manufacturers supply these at additional costs of hundreds of pounds. The voltage stabiliser ensures that a constant maximum load is placed on the turbine at all times. The circuitry reacts to changes in applied load, and feeds any excess power into the dump load, thus maintaining voltage and frequency.

What Head of Water do I need?

The minimum head is officially 1.8m, although the lowest head turbine has been demonstrated to work sucessfully down to 1m head. Ideally, you should have more head than this, as you need a large volume of water to produce sufficient power at low head sites

Can you survey my site for me, and tell me how much power I can produce?

Yes, we can, but it takes time, travel etc. We prefer to concentrate on offering the best products at the lowest prices, in order to make these technologies affordable. Consequently, we do not build-in the cost of so-called 'free surveys' into the price. Instead we try to offer all the information you will need in order to do it yourself. Therefore we can offer the service at a price, but you need to consider the cost of the survey with the cost of buying a turbine and some pipe to try it out. For small scale sites, our turbine prices are so competitive, you might as well do some crude calculations yourself, and purchase a turbine to test it out.

Can I survey my own site to save money?

Yes, of course! We encourage customers to do this, as surveying costs are high, and yet it is very easy to achieve fairly accurate results by carrying out a DIY survey. Many installers will try to make you believe that this is a magic art which requires great skill. Read below to find out how to survey your own water site, and then decide if you agree!

How do I calculate the potential power of a site?

You need to measure the maximum fall available and the flow rate. Bear in mind that flow rate varies considerably by season, and the turbine will not work if flow rate drops below the design requirements. The power output (watts) = head (metres) x flow (litres/second) x gravitational constant ('g' i.e. 9.81) x efficiency (~70%)

How do I measure head?

The best method is to use a laser level. Set up the laser level at the point where you intend to divert water from the main flow. It is easier to set this up at waist height, so measure the height difference from the level to the water level. Use the laser level to project a level to a point above the lower part of the water course, where you intend to place the water turbine (use a tall tree, wall or similar to project onto). Measure the difference in height between this projected level and the water level at the lower point. Deduct the height difference between the laser level and the water level at the top of the watercourse. This is your head. If necessary you can do this in several stages, if you are surveying a long watercourse. As a crude method, on high head sites, it is sometimes possible to use the height contours on an ordnance survey map to give an approximation.

How do I measure the flow rate?

This depends on the amount of water you are trying to measure. The flow of a small stream can be measured by finding a natural dam, or installing a crude temporary dam, and diverting the flow into a large bucket. Measure the capacity of the bucket beforehand, and time how long it takes to fill the bucket. For larger water courses, where this is impractical, you can estimate the average depth and width of the water. You can then drop a leaf or stick onto the surface of the water and time how long it takes to float 1m (or 10m etc). For example if the average depth is 1m and the average width is 5m, and it takes 4seconds for the stick to float 10m, then the flow rate is 5x1x(10/4)=12.5m3/second. To convert m3 into litres, simply multiply by 1000 i.e. 1000x12.5 = 12 500litres/second. If you have a river, you can often check the flow rate simply by telephoning the Environment Agency, who monitor the flow of most rivers. Some of the information is even available online.

I have not got enough head. Perhaps I could use a small nozzle to get extra pressure and therefore more power?

Power is dependant on flow rate and head. Nothing else...or at least, nothing you can change (the gravitational constant and the density of water)

Could I pump the water back up to get more flow?

Yes, you can do this, but you will use more electrical energy pumping than the extra you will produce from the water turbine?

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