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Intake with Coanda screen filtration

Overview of hydro systems

Hydro schemes vary depending on the local topology and land characteristics, but all schemes have the same essential key elements:

Intake

Most run-of-river schemes have a weir built in the river to allow the collection of water to power the system. Typically this is a concrete construction and will incorporate some method of screening the water passing in to the penstock and thence the turbine. The level of screening will depend on the type of turbine used. It is unusual to build dams or storage ponds for small and medium hydro schemes, but existing infrastructure can possibly be re-utilised.

Penstock pipe or lade

From the intake a lade (open water channel) or penstock pipe will run to the turbine location. Lades are more typically used on low head schemes and pressurised pipes are more common. The pipe is typically buried underground for support and protection and to minimise the visual impact.

Turbine

Many different types of turbine are available and the correct choice depends primarily on the head and flow of the scheme. Low head schemes suit an Archimedean screw or Kaplan type turbine, whilst high head schemes would normally utilise a pelton or turgo turbine. Crossflow turbines fill the gap. The turbine will be linked to a generator and the whole system governed by a custom made control system. Most turbines require a turbine house or shelter.

Grid connection

Grid connection is via an import/export meter. If connected to an existing use of electricity, this measures output to the grid when surplus electricity is being generated and electricity drawn from the grid at times of low/no generation or peak usage. Many schemes are connected direct to the local electricity supply infrastructure, owned by the relevant District Network Operator (DNO). They will make a charge for the connection which can be significant. Additionally, if there is not sufficient spare capacity in the local supply network to incorporate the electricity generated, the DNO may charge to upgrade the system. Grid connection can add significantly to the cost, complexity and timescales of any project.

British Hydro Power Association Scottish Land & Estates Renewable Energy Assurance Ltd