Hydro power on a damn small scale!

dbBrad takes a day off and has a damn (pun intended) good time at Lake Ohau Lodge's sustainable resort.



dbBrad demonstrating the Coanda effect (water being drawn up my fingers) as well as showing the amount of water that flows over this ingenuous little intake for a small hydro electric system.

Just a kilometer or so north of the Te Araroa Trail, where it heads south into the mountains leaving Lake Ohau is the Ohau lodge. An amazing place with spectacular views and wonderful food. At breakfast the following morning I had the pleasure of meeting the owners, Louise and Mike. They told me a storm was coming which would deliver up to 16cm of water, about 7 inches. That is a lot of water! Concerned about my trip into the mountains they offered me accommodation for another night despite the fact that the entire facility was booked for a wedding.

330' above the mechanical room is the intake for the hydro electric system.  A small concrete wall directs water over the ingenious grill (top left) and into the 10" steel pipe which has the grating to the old 'storm drain' style intake welded on top for access. 

In talking with Mike further, I found out that the entire lodge is powered by renewable energy--a mini hydro-electric system. My interest was now at a peak. Mike offered me a key for the machine room and showed me the direction to travel up the hill so I could see more. 

dbBrad looking at the new hydro-electric turbine and electric generator in the old diesel generator bunker.

I headed up the hill following a stream to the intake for the mini hydro generator (97 meters vertical rise) which followed a 10" pipe 330' long running from the stream down to the turbine/generator. One of the problems with intakes can be flooding which washes debris, rocks and silt down the stream and can clog the intake stopping the flow of water. Besides reducing water flow and thus power generation debris, low water flow, and dirty silty water can all damage the turbine.

Old diesel generator room which easily houses the small hydro-electric system which powers the Ohau Lodge.

This simple intake works on the Coanda principle, a phenomena similar to the Venturi effect. It is ingenious in it's simplicity and fascinating in the amount of water that can be drawn into the small grill. At the top of the intake, the water is over an inch thick and in less that 30" all the water is literally sucked into the intake providing clean water and simultaneously allowing debris to be washed over and down into the creek rather than be piled up against a grill as in the 'storm drain effect' where sticks and plants restrict the flow of water.

One of the more attractive large damns but still very questionable environmentally.

All in all, the system has minimal impact, diverts less than half the stream water (at lowest flow) involved no digger(NZ technical term for excavator) in the stream and just a little bit of concrete for a diverter. The water returns to the stream virtually unchanged (temperature, saturated oxygen content, cleanliness) some 300 feet later and it's mostly an invisible system. Great way to go in my mind since I come from the Pacific Northwest which has hundreds of large damns that are silting up, have literally destroyed Salmon runs, covered millions of acres of habitat and will someday need to be replaced. Although occasionally beautiful in their magnificence, the big dams of the world are environmental blunders.

China's 3 gorges dam with no questions about it's environmental impacts. Just one big ugly mess though it does produce over 3 times the power of Washington State's largest dam, Grand Coulee.

For more on Hydro Electric issues, go to Mr. Greenguy

http://mistergreenguy.com/hydroelectic-power-damn-interesting-facts/