Power expectation from this river...help!

Hi permies,

can you help me figure out the power I could get from this river to the house ?
I would like to use the power in this stream to make electricity for the house.
There is no head pressure, so I am thinking this type of system https://waterotor.com/.
I read tha DC electricity is easier to store but I need advices on this too.

The flow rate is 3.81 m3/s (60389 USgal/min).
The flow velocity is  0.42 m/s
The width is 10 m (33 feet).
The depth is around 90 cm.

Here are images of the river :

Thanks for your help

Just looking at the volume of water, I'd express an unexperienced opinion of not very much at all.  I'd be surprised if it could make 100W.

I think you would be far ahead going with solar instead, even in a cloudy area.

In terms of power, you store the electricity made in batteries, either 12V, 24V, or 48V.  Most likely you'll want to go for 48V for powering a full house, though you could get by with 24V.  Please forget about 12V completely unless all you want to power is some lights, and maybe a TV.

Here are some generalities for you to think about....

12V system: lights, computer, TV
24V system: above, and a refrigerator or freezer, power tools
48V system: above and 240VAC items like big air-conditioners, well-pumps, ect.

I've built all three, and have abandoned 12V completely.  What I tell people is to stick with 12V only if your application has wheels.

The very first thing you need to do is make an itemized list of what you want to power, and how many watthours per day you expect to consume.  I would not even bother with a project without starting here first.  Most new people I've interacted with grossly overestimate the power they can make, and grossly underestimate the power they would consume.  I really hate having to help people fix their mistakes.  So, plan first.

What I myself am consuming on a daily basis is in the range of 3.0-3.5kWh of power.  You could also write that as 3000-3500Wh.  That's for what I mentioned above, with the lights on, a couple of hours of TV and computer time, and keeping the refrigerator/freezer running 24/7.  On irrigation days though, when I'm running the 240V well-pump, that number jumps up to 20-25kWh of power.

One thing to comprehend is the concept of the sunhour.  That is the amount of time the sun can power the panels at FULL power.  Typically for my area, that's 3.0sh in winter, and 6.0sh in summer.  In cloudy, rainy weather it drops down to ~0.5sh per day.  Plan for you winter lows, not your summer highs.

So, to get a realistic estimate of what you can make, divide your total consumption per day by your sunhours.  So, if you need 3.0kWh of power in December, and you get 0.5sh of light, that works out 3000Wh/0.5sh of solar panels = 6000W of panels.  You might find it more economical to scale the solar back to 1000-2000W of solar, and charge the batteries with a generator when a winter storm blows through.

Shop on Craigslist, or Facebook MarketPlace to shop for panels locally.  Shipping is the killer.  Don't order panels through the mail.  You will get far better deals with a cash and carry purchase.  Recently I've gotten four 250W residential panels for 160$ total.  I'd suggest starting at 2000W and working up from there with upgrades as finances allow.

You scale the batteries to your expected load, and the length of time they need to supply power.  Let's say you need 3000Wh per day.  You want two days of power before you start a generator.  You don't want to drain the batteries more than 50%.  You have a 48V battery bank.  The math becomes.... (3000Wh X 2 days X 2 fold capacity)/48V = 250Ah battery.  You could wire eight 6V Trojan T-105 batteries in series to get a 250Ah battery bank at 48V.  At 150$ per battery, that's ~ 1200$ for the batteries.

Lastly, you need a charge controller, and an inverter.  The charge controller takes the raw DC from either your solar, or your waterwheel, and transforms the voltage DOWN to what the battery bank wants.  The inverter takes the DC power out of the batteries and converts it into the 120VAC the wall sockets want.  You want to buy a sine-wave inverter if you want to run anything with an electric motor, like the frig, window fans, power tools, ect.  A square-wave or modified sine-wave will fairly quickly burn out anything running a motor.  Good brands are Samlex, Outback, MorningStar, Schneider, and Victron.  The quality inverters start at ~1200$.

I think Michael's analysis is pretty much bang-on. There is just not a lot of energy available in terms of serious power production.

Even so, there is a little bit of energy -- enough to run a few LED lights or charge a small 12V battery that in turn charges other batteries/lights. This would be a fine candidate for a homemade project.

It might also be worthwhile considering a direct mechanical connection to run a grindstone or a positive displacement (piston) pump or generate compressed air.

Your .42 MPS =.94 MPH and the Waterotor minimum speed is 2MPH to function, so likely won't work.
Very interesting technology though.

I would think you'd have to build a dam and create a fall in order to get some power from that water...and well dams are not my favorite landscape altering technology.

Kyle Hayward wrote:Your .42 MPS =.94 MPH and the Waterotor minimum speed is 2MPH to function, so likely won't work.
Very interesting technology though.

I would think you'd have to build a dam and create a fall in order to get some power from that water...and well dams are not my favorite landscape altering technology.

Kyle is completely right.  You have less than half the velocity needed.  And that means a dam of some sort for this answer to work.  Flow rate is velocity X cross sectional area.  To more than double the flow velocity means you have to reduce the cross sectional area the stream flows thru by the same amount.  For now to keep the numbers easy let pretend it is 3X.  They don't say how wide it is but pretend rotor is one third the width of your stream.  Then at minimum you would need to add wings blocking the other 2/3 of your stream flow.  Guessing that would be too much depth and you would actually need more to account for secondary affects.  That would triple the depth of your stream so your stream would now need to back up do a depth of 270 cm.  90 cm = 2.95 ft.  270 cm = 8.85 ft.  So basically you would need to dam the stream at least 6 feet deeper than it is now.  That low a velocity suggests very little stream fall which means up stream you would flood a long ways back upstream.   Which would likely bother a lot of neighbors and getting the permits to do it would be very difficult.

You wouldn't need to raise the water level that much to run a turbine-type generator. A 9' head would be needed for a big overshot wheel. To increase the water speed at a point, you just need to reduce the cross section at that point to say 1/3 of normal, and the water will be moving three times as fast. It will raise the water level some, but not very much. Wing walls up to the height of the surface at minimum useful flow would allow floodwater to run over the top and not endanger the banks much. Of course, everything depends on the actual conditions at the particular spot, so detailed analysis is needed before starting a real project.

It looks like you have about 250 watts of power there.

But it would be very hard to actually use it as is.

In my opinion the best way to make it useful would be wing walls as Glenn Herbert suggested, and a undershot wheel to capture the power.  With such a set up you may get 75-100 watts out of it.

But in many areas you aren't allowed to dam up a river/stream without jumping through a LOT of hoops.

Do you live in a area where the stream freezes in winter?  That would make it much harder.  Does it regularly flood in spring or after heavy rains?

75-100 watts may not sound like much but unlike wind or solar it is 24 hours a day 365 day a year of dependable power.

 If it is 100 watts that gives you 2.5kwh's per day.  An average American home uses 30kwh every day.  2.5kwh would be enough to:
   run a fridge and a chest freezer for a day, or
   run a electric heater for 2 hours, or
   light an entire house with LED's for a couple days, or
   wash 20 loads of laundry, or
   dry 1 load of laundry, or
   pump 250 gallons of water out of a shallow well, or
   drive 7 miles in an electric car, or
   watch 15 hours of tv.

2.5kwh's amounts to about 25cents worth of electricity every day or $8 a month

Depending on how you look at it that is a tiny amount of power and not worth the hassle, or it could be a life changing amount of power and would open up all sorts of new things for you.
   
   

J Hillman wrote:75-100 watts may not sound like much but unlike wind or solar it is 24 hours a day 365 day a year of dependable power.

... Depending on how you look at it that is a tiny amount of power and not worth the hassle, or it could be a life changing amount of power and would open up all sorts of new things for you.

Well said J Hillman! I think this is an excellent way to approach the problem. If I had a constant flowing stream on my property, I would absolutely find a way to harness it.

The challenge, as noted by many posters, is how to do this without breaking rules and community trust. And doing it inexpensively, so that the energy generated exceeds the cost of materials.

Qualitative estimates can sometimes be a little error-prone. I would recommend putting some numbers to this.

Power = Flow-rate x Head x density x gravitational constant x efficiency.  You have good estimates for everything except elevation. So let's just assume you have a small elevation change of say 0.5m, the power generated at 100% efficiency would be.

Power (W) = 3.81 x 0.5 x 1000 x 10 = 19050 W = 19.5 kW

So that's a notional estimate of available power based on an elevation change of 0.5m.

Your setup has an abundance of flow and a probable lack of elevation change. So firstly measure that elevation change to get a handle on it.
I recommend you speak to someone with some knowledge of how/whether you can tap into this source with a properly engineered system.

As regards many of the comments here, they seem to be focussed largely on velocity when clearly velocity is a function of flow-rate and cross-sectional area. So I wouldn't worry too much about that.

So I would conclude by saying there's power there that could power your home. However you need to measure your elevation then find out the answer to an engineering question - ie is there a system design that can tap into this power source with a high efficiency?

Louis Romain wrote:Hi permies,

There is no head pressure, so I am thinking this type of system https://waterotor.com/.

There must be some "head pressure" ie elevation or the river wouldn't flow.

Here's a type of system that might suit your setup with low elevation and high flow....

https://www.turbulent.be/

Regards

Stephen

Louis Romain wrote:
I would like to use the power in this stream to make electricity for the house.
There is no head pressure, so I am thinking this type of system https://waterotor.com/.
I read tha DC electricity is easier to store but I need advices on this too.

The flow rate is 3.81 m3/s (60389 USgal/min).
The flow velocity is  0.42 m/s
The width is 10 m (33 feet).
The depth is around 90 cm.

The flow velocity will vary with rainfall - take more measurements, then work out how much downtime you can work around, when there's insufficient flow.
Constricting the river from 10m to 2m will increase the velocity around 5x. And make the kit smaller and cheaper. A bend in the river will send the flow to the outside.
If you fancy alternative uses:
A hydraulic ram pump can use the flow to power a flow to house or irrigation, without external power.
Water source heat pumps are more efficient than air source - but you won't want it cold enough to freeze the river!
If there's sunlight getting to the surface, crops are more possible - here's a list for ponds and bogs: https://pfaf.org/user/cmspage.aspx?pageid=79
Bathing!

I know nothing about these things, other than that I live within a few miles of two major dams on the Columbia River, in The State of Washington.

That aside, it would be fun to see what a small, slow moving river like this could do using a water wheel on floats and chained to the shore.  Like so many other places in life, I'd try to incorporate some major gearing and a flywheel.

It's difficult for me to believe one couldn't get some worthwhile power off the system.  Others, on another thread, made claims about what couldn't be done because of the weight of wheels involved, but grew very quiet when asked how old flower mills were able to move huge, heavy stone wheels that, weighed tons, to grind wheat.


SIDE NOTE ON POWER STORAGE:  Look into gravity batteries. All they are is, a weight moved up a hill using excess power (why wouldn't poles work?) on a track. When allowed to roll, slowly, back down the hill, they generate power.  Think in terms of your coo coo or grandfather clock and the pendulums that store power. An idea I'd love to see applied to pellet stove augers so they could continue to work when power goes down.

You may know very little about such things but your points are well made.

I would add that your intuition is (I think) working toward the distinction that I made earlier between the science (ie the reality) and the engineering (ie how we tap into that reality with a system that can try to deliver on what we want.

Unfortunately many people have limited backgrounds in either science or engineering which it makes it really hard to get to the nub of an issue and thus target what is required. That is not to denigrate the "tinkerers" amongst us with the hands-on practical knowledge of system design.

Anyhow I'll get off my high horse before I get pushed off.... and I wondered if anyone on Permies has ever worked with, or seen one of these low elevation systems:

[youtube]https://duckduckgo.com/?q=video+of+vortex+turbine+in+river&t=newext&atb=v364-1&iax=videos&ia=videos&iai=https%3A%2F%2Fwww.youtube.com%2Fwatch%3Fv%3D7w9rxf6UutA[/youtube]

Kelly Craig wrote:


SIDE NOTE ON POWER STORAGE:  Look into gravity batteries. All they are is, a weight moved up a hill using excess power (why wouldn't poles work?) on a track. When allowed to roll, slowly, back down the hill, they generate power.  Think in terms of your coo coo or grandfather clock and the pendulums that store power. An idea I'd love to see applied to pellet stove augers so they could continue to work when power goes down.

A gravity battery does work.  The problem is; making one large enough to store a real amount of power is a huge undertaking.  Your example of a grandfather clock is a good place to start.  If you  wind it up 600 times you will have stored about as much usable energy as a watch battery can hold.

So now if you want to store enough power to run a energy efficient home overnight you have to have a huge system.