Update on Bay Of Fundy Tidal Power

waynefromnscanada

Underwater turbine was trashed by extreme tidal currents in just 3 weeks.
www.thechronicleherald.ca/Front/1252613.html

westbranch

Re: Update on Bay Of Fundy Tidal Power

I wonder what type of engineer UNDERestimates the power by 30 times??? I hope it was in the data or someone should be out of a job...

BB.

Re: Update on Bay Of Fundy Tidal Power

Not to make excuses--but it is not as "big of mistake" as it would appear.

Power goes with the cube of the velocity:

• cube root (30) = 3.1x change in velocity

And when dealing with "real life" flows, turbulence, non-uniform fields (i.e., sea beds)--A Factor of 2x is almost "the same" in the modeling/measuring/predicting of flows.

A factor of 10x difference is a "night vs day" difference in Engineering Terms.

So, being off by 3.1 in velocity should probably not be a "fire-able" offense in a completely new field.

10x safety factors is standard for construction (difference between expected loads vs expected failure loads)...

Could you imagine if the Engineer told the bosses/folks paying for the project to make it 30x stronger and to make the generator 30x larger "just in case"...:roll:

Drawing power from nature (wind, water, etc.) requires serious over design... People talk about designing for 100 year storms, but they may happen anytime:

In their worst form, they were known as "100-year storms": catastrophes that occurred once a century and caused devastating floods.

And yet, in just the past four years, three times the Merrimack Valley and Southern New Hampshire have been hard-hit by storms that once came with interludes of decades between them.

So, do we design for 500 year events? How about 600 year events:

Inscriptions on up to 600 years old stone marker located near the coastal city of Kesennuma warn descendants:

"Always be prepared for unexpected tsunamis. Choose life over your possessions and valuables."
"If an earthquake comes, beware of tsunamis."
"High dwellings are the peace and harmony of our descendants, remember the calamity of the great tsunamis. Do not build any homes below this point."

We know that it probably would have reduced the losses of life and ongoing Nuclear Power Plant radioactive releases in Japan if people took the geological reports of Tsunamis seriously over the last decades...

-Bill

westbranch

Re: Update on Bay Of Fundy Tidal Power

hi bill, yes I was aware of the 10X engineering rule and have seen it used frequently. In forestry applications for road building we always looked for the 100 year event, yet as you point out we are getting events that are well in excess of those...

I guess I am just set back by the fact that the turbine failed is such a short time after being installed in a water-body ( Bay of Fundy) that is renowned for having one of, if not the greatest high - to- low tide variations in the world, everyday... ? Glad it wasn't my $$$.

info from BC Hydro on the project.
http://www.bchydro.com/news/articles/conservation/novascotia_power_turbine.html
and another
http://www.nspower.ca/en/home/environment/renewableenergy/tidal/projectoverview.aspx

Eric

Frxddy

Re: Update on Bay Of Fundy Tidal Power

It surprises me too. They built a small one & ran it for a while to do testing. One might think that water movement was a well understood phenomenon. Seems not to be the case! But, all in all, a good idea and a good test. I live just a half day's drive from that area. It is amazing how the tides there come & go with great speed. One particular beach has a stairway going down to the beach. Big warning signs and two clocks with signage: This is the time now: This is the time you must be OFF the beach.

If you are at the waters edge when the tide starts coming in, you CAN NOT outrun it. If you take off at a full run when the tide touches your foot you will not make it 300 feet. You will be swimming.

ggunn

Re: Update on Bay Of Fundy Tidal Power

waynefromnscanada wrote: »

Underwater turbine was trashed by extreme tidal currents in just 3 weeks.
www.thechronicleherald.ca/Front/1252613.html

This is the second tidal turbine to be destroyed there, isn't it?

waynefromnscanada

Re: Update on Bay Of Fundy Tidal Power

ggunn wrote: »

This is the second tidal turbine to be destroyed there, isn't it?

No, just an update on the same incident. Big wheels turn slowly