A little reminder to those of us with hydropower schemes of the importance of our screens.
The screening at our intakes is one of the least glamourous parts of any hydro scheme. It is often neglected and often out of sight (though penstocks and pipelines will say different)… However, it is one of the most critical components in determining the efficiency of our hydro schemes, and to cut to the chase, efficiency means money!
The Importance of Clean Screens in Turbine Efficiency
A clean screen means more water into the pipe and from there into the turbine.
A partial blockage may not stop the turbine operating, but may stop it operating at full power. A partially blocked screen can also create something called 'skip'. This is where water passes onto the screen but is lifted, or skips over, the dirtier part of the screen and misses the clean part.
In the case of a coanda screen with an accelerator plate, this can happen because of dirt or algae build up on the accelerator plate above the screen.
Not all intakes have coanda screens and often low head schemes can have larger and more complex screening systems. In these cases it is not about clearing algae, it is about clearing trees! As well as cleaning these complex screens, they may have a self-cleaning element but they may also have a legal or licenced requirement to facilitate certain flows.
In one instance earlier in the year, a Client's turbine wasn't operating properly. We were called out and on investigation we found a 2 feet long piece of plywood jammed inside the vanes. It turned out their self-cleaning intake was not operating and under high water levels had overtopped.
We hope to help them revisit the screening design and operation during the drier summer months. In the meantime, it means more regular checks for the Client.
Impact of Winter Avalanches on Hydro Systems
In another remote site, with a high head hydro up in the hills, a winter avalanche in the hills meant a geomorphologically active burn (more exciting than it sounds!). This led to unusual volumes of sand and debris in the water course which migrated through the screen and into the system.
You can learn more about our renewable energy services here: https://www.proterra-energy.com/services
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