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The Walsh River range of Micro-hydro turbines are designed especially for home use.

Planetary Power developed the Walsh River Micro-hydro system in 1991 to provide reliable low-head micro-hydro power for its own facility on the Walsh River in Far North Queensland. This prototype turbine is used to generate electricity and pump water - it is able to do both continuously and simultaneously, and from it has developed the range of Walsh River Micro-hydro systems.

These systems provide cost effective and environmentally friendly micro-hydro power for low head sites, ranging from less than 1 meter up to 8 meters

The Turbine

The turbine is of the Banki-crossflow type consisting of a cylindrical, horizontal axis 18 blade runner, intake nozzle, exit draught tube and housing. The turbine is available in two sizes: LH6-180 has a runner 270mm dia. and 180mm wide LH6-300 has a runner 270mm dia. and 300mm wide The runners are made of epoxy coated mild steel and are of all welded construction. The intake nozzle is designed to accept water entering via a 150mm dia. UPVC penstock (ie inlet pipe). The LH6-300 has a double entry, allowing a penstock made up of two pipes, side by side.

The penstock needs to be of sufficient length to develop adequate head, and is usually between 2 metres and 50 metres long.

In normal operation the turbine sits just above the tail pond into which the water is discharged. The water exits via a draught tube, which ideally descends into the tail pond itself. If rising water levels submerge the turbine, no harm results. The turbine will continue to operate when partially submerged, although it will stop when completely submerged, automatically restarting when the water level drops.

Electricity Generation

The WALSH RIVER MICRO-HYDRO SYSTEM is usually supplied as a complete package ready to generate electricity once assembled. It comprises: either the LH6-180 or LH6-300 turbine a permanent magnet DC generator micro-hydro controller frame, belt, pulley and other auxiliary items The turbine needs to be anchored in a protective part of the stream bed. Usually it is bolted to concrete footings.

The generator is mounted, either above the turbine on a 1.2m high tower, or separately on the stream bank. Power is transmitted from the turbine to the generator using a cog belt and pulleys. The output of the generator is then transmitted to the controller, which forms part of the switchboard located at the house, near the battery bank. The controller provides the battery with a continuous and regulated charge. The output voltage of the controller is switch selectable to accommodate any type of battery. The most common type of battery is the wet cell lead acid at 12V, 24V or 48V. An inverter, connected directly to the battery is used to provide mains quality 240V power for lighting and other loads.

Water Pumping

The turbine can also be used to pump water, either as a stand alone operation or as an adjunct to electricity generation. One system currently operating pumps water to a head of 100 metres, another pumps 40,000 litres/day to 20 metres head. PERFORMANCE The performance of the turbine, both for electricity generation and pumping water depends on the head and flow rate. Once these are known the output can be estimated using Figs. 1 & 2.

The head is the difference in height between the intake and the turbine and includes an allowance [of between 5% and 30% depending on the site] for intake and penstock friction losses. The WALSH RIVER MICRO-HYDRO SYSTEM is designed for heads in the 1 metre to 3 metre range. It will however operate at lower heads, with 70cm being the practical lower limit for electricity generation and 50cm the lower limit for water pumping. The LH6-180 turbine will also operate at heads greater than 3 metres, the upper limit being 8 metres.

The flow rate is the rate at which water flows through the turbine. It is usually limited by the flow rate of the stream, however the penstock and the turbine itself can also be limiting factors.
For the LH6-180 turbine, the maximum flow possible is 18.5 litre/sec for a head of 1 metre, rising to 26 litre/sec for 2 metres head and 32 litre/sec for a 3 metre head.

For the LH6-300 turbine the corresponding values are: 31 litre/sec, 43 litre/sec and 53 litre/sec. The turbines have an adjustable nozzle to accommodate variable flow rates. The flow can drop to as little as one third of the maximum flow rate with little reduction in efficiency. This is a feature for which Banki-crossflow turbines are noted.

A Typical Micro Hydro Site

A typical low head micro-hydro site has the following parts: A diversion weir is a small dam or weir to divert water into a penstock. The penstock is the pipe that carries the water to the turbine inlet. The turbine is the machine that extracts power from the water. Water exits the turbine via a draught tube into a tail pond or tail race. At the entrance to the penstock is an area to trap sand and debris called a forebay.The trash rack is located at the forebay to prevent debris and small animals being sucked in.

Collectively, all parts of the installation upstream of the turbine are called the headworks. The turbine is coupled to the generator cause it to rotate and thus generate electricity which is then transmitted via the transmission line to dwelling, workshop or wherever power is needed. The transmission line can be above ground or underground depending on site and environmental considerations. Transmission over several hundred metres is usually practical although once the distance exceeds about 300 metres the cost becomes quite significant

Assessing a Site for Micro Hydro

Assessing the suitability of a site takes time and care. It is important. You may invest a lot of money on the basis of your understanding of a stream. You need to spend time with your watercourse and get to know it so you can find the best site for your turbine and its headworks. As already noted the key factors that determine the output potential of a turbine are the head and flow rate and once these are known the performance curves can be used as a guide to how much power you could expect to be generated.

The head is the difference in height between the turbine and the intake of the penstock. It can be measured in any one of several ways, for example by using a measuring staff and sight level or for low heads a water hose level is suitable. The flow rate of the stream can be measured directly, for example by seeing how long it takes to fill a 10 litre bucket or indirectly by using a notched weir.

The weir method is useful for all stream sizes. A weir is built across the stream to cause the water to flow through a notch of known dimensions. Sometimes a natural rock formation will resemble a weir and will channel most of the stream through a narrow gap resembling a notch. The depth of the water flowing through the notch is measured and this is converted to a flow rate using tables published for the purpose. Usually the notches are triangular or rectangular.

Care for the Environment

All the water diverted through a turbine is quickly returned to the stream and assuming that some water is allowed to remain flowing in the original watercourse, the environmental impact of a micro-hydro site is minimal. The use of a WALSH RIVER MICRO-HYDRO SYSTEM keeps about one ton of CO2 out of the atmosphere per year.

The local generation of power also saves the cost of distributing mains electricity and/or petroleum and the related infrastructure. These costs are not currently considered in environmental assessments as they are borne by the community at large whether or not it uses mains electricity. Any project that reduces Australia's CO2 emissions helps to meet our international treaty commitments.These national contributions need to be recognised and rewarded appropriately.

WALSH RIVER turbines are manufactured locally out of mostly Australian parts generating local employment.

The staff at Planetary Power are available to assist you with the calculations and evaluation of potential sites.

A site assessment service is available. We will inspect the site, take the relevant measurements and produce a written report describing:- the site's potential to generate power, its potential to meet the expected loads, design considerations and options. The report also will include a system design proposal and development cost estimates.

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