Ivan's Creek: Low-head hydro-electric power

[tribdog]

How much money did you want?

5 dollars and 67 cents. Double quarter pounder meal. I'm hungry

 

[Ivan Seeking]

At three feet of head the first guy is probably off the power curve - the water falls too fast wrt to its forward velocity so the second impulse is out of time [I should say that the angles of the blades are wrong], which causes turbulent flow - but even then the efficiency can be as high as 50%.

 

[Ivan Seeking]

I moved this to engineering as a low-head hydro-power thread. There are times that this seems to be worth doing; esp here in the Pacific Northwest. In my case, the creek is probably too dynamic to tame for a 5KW, 8 month per year installation.

 

[Ivan Seeking]

Maybe this is being done now, but the idea of a variable load to match the source seem to be key with LHH. Consider electric space heat run in constant duty mode - say for example if we run 5KW at a 90% duty cycle, with a low speed fan mode [on the space heater], at opposed to the typical 20KW over a 23% duty cycle. This should allow space heat to run almost exclusively on hydro-power. Also, by adding the water pre-heater in front of the water heater, I calculated that we could utilize the average 5KW most of the winter with no other energy storage. IIRC, space and water heat are about 80% of a typical home's energy usage.

If you look at the average power usage in any home, it is surprising how little power is really needed if one could avoid the large, low duty cycle loads. Smart loads are I think a key concept needed to make this type of alternative supply practical.

 

[Ivan Seeking]

Okay, here is a nice page for the Banki turbine.
http://home.carolina.rr.com/unclejoe/

According to this, the paper that I read must have been the translated paper - Bulletin #25 - and someone at OSU built and tested it.

 

[Bystander]

http://home.comcast.net/~integral50/scenery/streamlr.JPG
The state of the stream today... Not nearly as exciting.

Have you considered the "rustic" approach? Can't tell a whole lot about the topography, just picturing an undershot wheel 'tween the trees and bridge, 'bout even w' the bar.

How much cutting goes on during the high water?

 

[Ivan Seeking]

Anything but a crossflow turbine is too inefficient to be worth doing. It just wouldn't be enough power to be useful in a practical way that would offset the cost. Undershot wheels can run as low as 20% efficient...in fact I think that's more like a best case.

And it does move an amazing amount of rock during heavy flows. The little island seen in the one shot was formed in about one day. I have seen it dig straight down through six feet of rocky clay in a week.

 

[Ivan Seeking]

I didn't even notice that the original paper is linked at the end.
http://home.carolina.rr.com/unclejoe/banki_scan.pdf

Also, ignore all of the whining about the paper. I had no trouble reading it and then designing my own turbine. [Yes, unfortunately I got that far].

 

[Ivan Seeking]

One more thought here: I think a major trap for the alternative energy crowd is the idea of selling power back to the power company. At $10K for the safety switch that is legally required in order to prevent back-feeding the lines during an outage and possibly killing a lineman, I don't think it's worth trying to sell the power back unless we are talking about a very large installation. But in many more cases it does make sense to isolate the system from line power and design the loads to follow the supply power available - to keep the system operating at max efficiency. The plan was to design one of the four heater modules [~5KW each] so that by using triacs, a 1, 2, 3, 4, or 5 KW load could be selected so as to maintain a nearly constant turbine speed. This seemed a best option as opposed to trying to PWM a highly inductive load or trying to vary the load linearly. In both cases the potential complications seemed best to avoid altogether. But this was a judgement call and unique to my situation. Linearly variable loads would probably work fine in most cases. The additional water heater element would be a fixed load in this plan, which would cause some additional losses, but it calculated out that those losses would be relatively small, and acceptable.

If the creek was more stable with an easily had four feet of effective head, and assuming a typical Oregon winter, this installation calculates out as being worth about $250 per month, eight months of the year. And keep in mind that a typical flow is about 16% of that seen here. Integral came by because of the unusually large flow due to a month of heavy rain.

Late edit [sorry]: for those who don't know this, one of greatest sources of energy loss and expense for alternative energy systems is the need for energy storage. This design seeks to avoid this problem. Also, the final parameters were for a variable 1- 10 KW load as the flows in the creek vary over the season. The max efficiency of the system occurs at a constant turbine speed and is otherwise independent of the load or the power being generated.