Technologies

Hydro Electric systems typically fall into three scales:
 

• Large Hydro and Pumped Storage > 5MW
   
• Run of River (including retro fit to existing systems) 100KW – 500Kw
   
• Mini/Micro/Pico Hydro <100KW

Most hydro schemes incorporate measures to prevent fish and debris entering the system. Maximum efficiencies can be up to 80/90% but for smaller schemes a more realistic figure is around 50/60%.
 

Large Hydro and Pumped Storage

New large scale hydro systems (>5MW) require a new dammed reservoir and turbine house. Large hydro schemes utilise a high static head of water behind the dam and use high head, high flow turbines.

A ‘basic’ hydro system can be coupled with a downstream pumped storage facility to improve the schemes short term performance allowing it to meet peak electricity demands. For these schemes an Environmental Impact Assessment (EIA) may be required including both environmental and technical studies required during the consenting process.

Pumped storage can also be linked to other renewable technologies, for example a wind turbine or wind farm, which can provide the power required to pump water up to the reservoir.
 

Run of River

Run-of-river schemes draw water from an intake above a weir which ensures a continuous flow and static head. Run of river provides a low-impact hydro solution harnessing the power of gravity and mountain rivers/streams.

Turbines used in run-of-river schemes include:

• Pelton Turbines - Medium to High Head (50m to 800m), high flow accommodating silt laden water
• Francis Turbines - Considered to be medium head turbines (10-250m)
• Kaplan Turbines - Low head, high flow applications
• Turgo Turbines - Accommodate the transition between Pelton and Francis turbines and have been proven to deal extremely well with “dirty” water
• Archimedes Screw - Low head (1-10m) and high volume applications
   

Mini/Micro/Pico Hydro

Small scale hydro schemes generally utilise 'off the shelf' turbines combined with a small dam or located in a stream. Small schemes have a minimal visual impact and fit well into the surrounding environment. They also have the added advantage of low running costs. The capital costs of small hydro schemes are very site specific and vary widely depending on location and the head of the river. Redundant hydro systems and other industrial systems can also be retro fitted to provide small hydro outputs utilising modern plastic pipes and cheaper jointing facilities.

Turbines used in mini/micro/pico hydro schemes are likely to be off the shelf solutions and may include:

• Francis Turbines - Considered to be medium head turbines (10-250m)
• Crossflow Turbines - A relatively simple impulse turbine, Crossflows are often deployed were the cost of manufacturing a Francis turbine would be prohibitive
• Archimedes Screw - Low head (1-10m) and high volume applications