Water Turbines

If you are lucky enough to have a water course across your property, such as a stream, river, or if you are lucky enough to own an old water mill, water turbines are an ideal solution for providing reliable long-term renewable energy. You can easily calculate the available power at your site using the following equation:

 Power (watts) = Head (m) x Flow (litres/sec) x 9.81 (gravitational constant ‘g’)

A typical water to wire efficiency is around 70%, so you should multiply the result by 0.7 to get the actual amount of electricity that you can expect from the site.

Most sites vary considerably in flow between winter and summer, reflecting the differences in rainfall. It is important to make sure that the flow is sufficient to run the turbine, and if you wish extract maximum power from the turbine site, it is often desirable to install two turbines, switching in the second machine, when the water flow allows. Alternatively, a twin nozzle machine may be used, which incorporates a valve to isolate the second nozzle when insufficient flow is available to run both nozzles.

NET METERING

Water turbines are ideal for net-metering. You can sell your surplus energy to the national grid, and get paid 7.9p/kWh. This means very short pay-back times especially for DIY installations, and in all cases, the investment will be PROFITABLE! There is also a ROC (Renewable Obligation Certificate) which can be claimed - this is 4p/kWh, but it does involve some paperwork. Ofgen are currently revising this, so hopefully things will become easier over the next year or two. In fact, you can claim the 4p/kWh even if you use the electricity yourself! This can make renewable energy very cost-effective.

HEAD TURBINES

These turbines are lightweight, and small in physical size, and yet able to supply high quality electricity, regulated in terms of frequency and voltage by their own internal voltage stabilization circuitry. They are based on 'Turgo' runners, which provide an ideal alternative for the Pelton wheel at lower heads. The medium head turbines, for example, incorporate a ‘dump load’ ballast heating element in the draught tube, which uses water-cooling to ensure that the load on the turbine remains constant. The machines may be operated for years with minimal maintenance, although it is necessary to apply grease to the bearings using the grease cap a couple of times a month, to ensure a long life. By reducing the jet diameter on these turbines, it is possible to operate them with heads of over 100m