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Eco-Siphon Packaged Hydro Station

Eco-Siphon Packaged Hydro Station

The Eco-Siphon Packaged Hydro Station technology relates to low head hydro power plants where the available head of water is between about 2 to 7 metres.

The Station provides an inexpensive method of extracting low head energy from rivers and streams where there is a drop over distances up to 100 metres. This is commonly found at dams, canals, low waterfalls and river rapids.

The benefits of developing a site using the Eco-Siphon Packaged Hydro Station are:
  • It eliminates the high cost of associated civil works and site assembly
  • It eliminates the high operational costs associated with cleaning screens (trash racks) that are used to limit the passage of debris into the turbine
  • It eliminates the biological damage done to fish passing through the turbine

The drawing above shows the patented (US-4,465,430 and GB-2 430 984) water turbine casing mounted in a turbine house, with the turbine’s intake facing downward toward a trash rack system used to screen the incoming water. The house sits in the head pond on 4 adjustable legs.

The water conveyance system is submerged in the head pond and in the tailrace to form a barrier to the entrance of air. Water is drawn into the turbine through suction generated by a pump until the turbine begins rotation. At this time the suction pump is no longer needed as the remaining air is mixed with flowing water until all the air is expelled into the tailrace.

The turbine uses a low speed, low velocity fish-friendly runner operating under a vacuum at the top of the siphon loop formed by the intake, turbine and discharge piping.

The application of the Eco-Siphon Packaged Hydro Station is governed by two factors, the size of the turbine and the elevation between the head pond and tailrace.

The practical application of the technology is limited to about 7 metres in stations using turbines less than 800 mm, and to 6 metres when using turbines more than 1.5 metres in diameter.

The length of the discharge piping system is limited by friction losses between the water and the piping. This can reduce the suction on the turbine to the point that the reduction in energy does not leave enough velocity in the water column to convey air through the system. Which means elbows must be avoided if the discharge piping is relatively long. Refer a drawing of the piping system to the factory for determination of the expected power that will be generated.

The supports for the station are adjustable to allow for an irregular bottom and to allow the station to be elevated for access to the trash racks or excessive rises in the water level. Lifting the station is facilitated by the use of a flexible coupling in the discharge piping that can be readily removed. The house containing the turbine is constructed to resist the entry of water and is self draining. The housing is coated steel to resist corrosion. The skirt that projects into the water, and the trash racks, are made from stainless steel. The house sits a short distance into the head pond in order to deter the entry of air and surface debris.

The trash racks are placed above the surface of the river to aid in the removal of debris when the turbine is not operating and to prevent the accumulation of marine growth when the system is shut down for an extended period. In some cases due to varying levels it may be desirable to submerge the trash racks.

Having horizontal trash racks greatly reduces the depth of head pond needed to draw water into the turbine house, and reduces the infiltration of air into the piping system.

The siphon is broken by the admittance of air through a valve, allowing the turbine to be dry when not in operation. An expensive turbine isolation valve is not required and there is ready access for maintenance and repairs.

An elastic coupling is employed between the turbine discharge and the piping system conveying the water to the draft tube. This coupling eliminates vibrations in the discharge piping from reaching the turbine house and facilitates access to the discharge of the turbine for maintenance and repairs.

To shut the station down, air is admitted to the top of the turbine. Water in the turbine and intake system discharges downward toward the trash racks. The water moving opposite to the normal direction of flow will clean the trash racks of most accumulated debris. Additional trash will fall off the racks when they are exposed to air as the wet debris will be pulled naturally downward.

The technology reduces the civil works required on site to the support of the discharge piping system, and any excavation that may be required for the draft tube and the creation of a small pond under the station. All the major components except the supports for the discharge piping can be manufactured under ideal conditions at a factory and shipped assembled to site.

Electrical System

The Eco-Siphon Packaged Hydro Station’s electrical system can be supplied for on or off grid connection.

In the off grid application, the connection is made to the Station’s circuit breaker/isolation switch. Station power can be single or three phase with voltages from 115 to 600.

Control of the Station is by a programmable logic controller (PLC). The PLC has inputs for mechanical and electrical parameters to allow for the automatic generator protection and alarm system. The PLC also controls the start-up and shut-down system as well as sensing blockages of the trash rack, internal and external temperatures and water levels. All of this information is available at the Station or remotely through wire or wireless connections.

In an off grid application, the PLC controls the frequency of the station through an artificial load system; this balances the demand for power from the external loads with an artificial internal load to control the speed of the turbine/generator.

The internal artificial load is water cooled heating elements in the intake system that can be accessed in the dry when the turbine is shut down.