Grid tie voltage? AC or DC?

[OperaHouse]

With all the LED and heat pump water heater I'm still an energy hog.  Twice my average neighbor.  Have a hot tub that the wife won't give up.  Still, I decreased from last year.  You generate it and I'll help you to get it to the right places.

[Bruce S]

MAL;
I like the part about collecting Mini-Fridges  . Sounds like a new form of income. Collect, fix, sell 'em the incoming college freshman class. Rinse and repeat.
At a certain age, the fight gets to be just too much, so ya pick your battles and go from there.
 
From the description about where you are makes it sound like a very nice scenery.
I'm with george65 on this one, get a good handle on the daily power needs over build by 50% and go from there.
Maybe, depending on the size needed, think about a 2nd smaller unit?

We're rooting for ya!
Bruce S

[Warpspeed]

That certainly was not my experience.  I had to replace very few appliances, all with secondhand but almost new. That better than halved my consumption, and payback period worked out to just over two years.
Anyhow to each his own.

I have a system here, its not grid tie, but it behaves very much like grid tie, except it feeds nothing back into the grid. It does have the advantage that if the grid goes down I still have power, at least during daylight hours.

Like yourself I cannot see a battery being economically viable where grid power is available as an alternative.

The way my system works, incoming grid power is first isolated with a transformer, and converted to a fairly high dc voltage, which then runs my sinewave inverter.  That is how it works at night.

During the day when solar is available,  the regulated dc voltage from my solar controller is set to a voltage slightly higher than the voltage coming from the rectifier, and powers the inverter.  So I get free power during daylight hours.

If the solar system is overpowered, perhaps just by some short term inrush load, the voltage on the dc bus falls, and the dc rectifier makes up any shortfall from the grid. There is no battery required to do any of this.

The inverter is very basic, there is no need to  synchronize it to the grid, so its a very simple system. Its also extremely efficient because everything is done at  high voltage and comparatively low current.

It would be possible to combine several different sources that all feed into a common dc bus to power an inverter, but the key to efficiency is doing the whole thing at several hundred volts, not at the low dc voltage the battery guys are usually forced to run.

You could do something similar, and hydro would have the advantage of working at night. But the idea of needing a 20Kw to 30Kw inverter and a similar sized hydo to power that is just mind boggling for a do it yourself project.

[MAL]

WarpSpeed,

I think it's 2Kw not 20Kw, correct me if I am mistaken. 

[MAL]

Hey George,

When I get this thing up and running, I'll be sure to get that invite out to Ya for the Tiki bar party to see if it will light up the new Tiki lights.  It sounds like OperaHouse is going to be the guest of honor.

 I Thought that I was going to have to radio the tower and report a hijacking.  If somebody wants to read about grid tie voltage they are going to have wade through the mud to get there.

I like how your system works , I imagine that I will go with some sort of a combination of grid and no grid. 

Hey Damon,

10yrs?...I guess my appliance is not in compliance...there coming to take me away.  https://www.youtube.com/watch?v=DxVkAhto0Ag

I bought a new washing machine not too long back...it's junk.  A ten dollar bearing went out of a $250 transmission that is not serviceable.  I drilled the spot welds and replaced the bearing...and there have been many more problems.  I am going to fix the 30 year old machine and junk the new one.  There is a reason why they want you to buy a new appliance every 10yrs...and it's not for your personal gain.

OperaHouse,

You are the man of the hour, I have read through a lot of your post...I don't understand all of them, but I have read them.  I am going to do my best to hold you to that.  I may not know what a diode or a cathode is...but I do know my right hand from my left   Do you have any quick thoughts on battery-less systems?

Thanks Bruce, 

I can use the support. If you don't mind me asking...are you looking for a mini fridge?

Yes, I have a very nice lot on the Mississippi River.  We have a naturally sandy beach that leads to muddy water.  I built a Tiki hut, boat shed and a dock with great boat access.  If I can figure out how to post a picture, I will. (File too large?  I will try again later)

Hi WarpSpeed,

There are some second hand appliances around, but there is an aggressive program to haul away your old machine and scrap it in the States.  I prefer to own things till I understand what makes them tick...it makes working on them easier.

Your system sounds very interesting.  You are converting grid to DC?  I have a digital electric meter so it wont spin backwards anyway, so there is no reason for me to risk penalty.  Can I get a little more detail on the equipment that you used?..brand names, models, etc...so I can look them up? Do you still need a dump load?

[MAL]

Here is a picture of the site. I am not sure how to make the picture smaller...hope I don't get into too much trouble.

[Bruce S]

The PIC is just fine.
Where on the Mississippi did you get such a nice view!!?
As for mini-fridges .
I have a small collection of my own. The solid-state ones and a few of the standard mini-fridges that even include mini-ice trays  . I've already donated 3 to my work just to get them out of the house/basement!!


These, I pick up during trash day. The solid-state units I fix pretty easy, usually only a fan or blown fuse. Once in a while a TEG is burnt out from having no air flow.
These are good if you need something that will start even with a MSW inverter. The phase change type I use for testing larger inverters and battery banks. They like the larger units can take up to x10 the running Amps just to start.

[Warpspeed]

Mal, the very first thing you need to do is monitor your consumption.  If you already have one of those new fangled "smart" meters, all the information should already be there and accessible.

You need to know your consumption pattern in order to properly size a system.  The biggie is peak demand. That needs to be met or the system will sometimes crash.  So start out with a plan.

There are decisions that can be made at the outset such as if some really horrible and very  infrequent electrical loads can be met in some other way, than just oversizing the system to always cope.

You may be very surprised that the load pattern is so lumpy, peak loads can easily be ten times or more the average.
If you are using 2,000 Kw per month, that is about 67Kw per day or roughly 2.8 Kw average day and night.
A 2Kw inverter is just not going to cut it, something like 20Kw would be the minimum,  possibly 30Kw .
You will not know unless you look at a full years data from your smart meter.

I monitored every individual appliance, and there were was a great deal to be learnt and some real surprises.
But whatever your circumstances, you need to know some real world figures before setting out to design a system.

I am a retired power electronics design engineer, so for me it was more interesting to build every part of it myself and do it exactly how I wanted to do it.  So I cannot suggest any commercial equipment. 

Anyhow, I am located in Australia and its 240 volts 50Hz here, which would be no good for where you are. And my system is solar not hydro, so your situation is rather different.

[MAL]

Hi WarpSpeed,

 I am not using 2000kwh.  If you look at my usage I had one month over 2000...January.  #1 it was an anomaly, I ran out of fire wood, had house guests and the fridge had a bad thermal switch that caused it to run all the time and not cool...It was a record consumption  for the 50 years that I have been here as far as I know.  #2  In January I will be on grid power, because there is ice on the river.  The rest of the year averages about 1100kwh or so.  How does using 1100kwh per month require the use of a 20,000kw generator?  My usage is high on average,  but I have an all electric home until I run out of fire wood.

 I think something is getting lost in translation.  American electrical consumption dwarfs the rest of the world because we have had more freedom than the rest of the world, but that is changing.

I don't think that I have a smart meter, but it is digital.  If I start plugging my wife's appliances into a kilowatt meter, I'm going to need a new place to stay. 

I DIY power control system would be my first choice...not sure if I can get there, but we are in the controls section of this site so maybe...

Is there a better  forum for discussing MAL's electrical consumption?

[MAL]

Hi Bruce, 

I am not sure it is a good idea to give out my address on the world wide web, but if you promise not to tell anybody, that's Iowa that we are looking at across the river.

[Warpspeed]

Mal 1,100 Kw per month is a 24hr usage of 36.7 Kwh per day, or 1.5 continuous Kw average.

You will use a lot more power during some peak usage periods during the day than you do at 3Am. How much more I have no idea.  That is why you need to do some monitoring.  If your peak demand is 10Kw, and it could easily be that, or even higher.  That is what you need to engineer the whole system to be able to supply.

Once you know what your real needs are, you can then engineer a system around that.

[MAL]

WarpSpeed, 

That is starting to make some sense to me.  I thought that the grid would handle peak usage if the system was set up like yours...and what happens to the excess electricity if I had a 10Kw generator when I am not using it...I could heat the swimming hole ...But seriously I don't know what happens to electricity that is being generated but not used.  My assumption is that it has to be used with a dump load.  Is it possible to build a system that has grid backup for peak load?

[Warpspeed]

The problem with grid tie these days, is that at one time you were only charged for net usage, any power you fed back into the grid you received a credit.  So you could figure your installation cost against future savings and come up with a realistic payback period, and then be pretty much free from electricity charges after that.

The privately owned power utilities (and their shareholders) expect income to grow every year, regardless. And the greenies generating their own power became a lethal menace to future profit, because the power utilities still have the expense of maintaining and expanding the power distribution network, while seeing a steadily shrinking income.

The first step was to reduce feed in tariff to a point where you have to feed back about roughly ten times as much power as you consume just to break even.  So people just started installing much larger systems to do exactly that.  The power utilities still were not seeing the rise in annual income they have become used to budgeting for.

The next step, at least here in Australia, was to introduce really tough laws regarding how large a grid tie system  could be.  All of which is purely to keep the power utilities profitable.  I don't know the situation in the US, but it probably varies greatly from state to state.

If you decide to install a grid tie system, you suddenly come under very close scrutiny, and with a smart meter they can see exactly what you are doing minute by minute.

In a perfect world you could maybe install a 1.5 Kw hydro and break even in power consumption most months, but that will never satisfy the power utilities.  And what you are actually allowed to do, (or can get away with) is highly variable.  Going totally off grid is a pretty expensive business and just not a viable option if grid power is already available.

Its difficult to know what to do both technically and financially.  But one thing is for sure, the power utilities demand their pound of flesh, and they have the law behind them to ensure they get it.

[MAL]

I was not talking about about feeding back into the grid, just taking from it as needed.  That was my understanding of how your system works.  I can see that a grid tie has it's pitfalls, and I am not seriously considering it any more unless I can see some benefit in the future.

 Why can't I  rectify the  grid power to a fairly high dc voltage, which then runs my sinewave inverter.  In the winter I could just flip a switch and use AC from the grid to avoid losses.

During the spring, summer, and fall when hydro is available I could set the regulated dc voltage from my hydro controller  to a voltage slightly higher than the voltage coming from the rectifier and power the inverter.  So I get free power during hydro season.

...and if the hydro system is overpowered, perhaps just by some short term inrush load, the voltage on the dc bus falls, and the dc rectifier makes up any shortfall from the grid with out batteries or a grid tie.

Wouldn't this system solve the peak usage issue so I could use a 1.5 or 2Kw generator?

[Warpspeed]

That is exactly what I myself am doing, and it works great.

First thing is to size the inverter, because all your power must go through that, unless the system is totally bypassed.
For realistic inverter sizing you need to collect some monitoring data, mainly about peak demand.
Then its just a case of keeping up the dc input voltage to the inverter from whatever mixed power sources you have available.

You can start off with just the inverter, and a large grid powered dc power supply to make it go. 
That will initially reduce efficiency.
Then later you can add, hydro, some solar, a wind generator, anything you like to reduce the load drawn from the grid.

I built up my system gradually from scratch that way.
If it ever fails, I can just throw a bypass switch and run straight from the grid while I carry out maintenance.

[MAL]

My next question might be stupid,  Why do I have to rectify anything to DC? The Axle Flux generates AC unlike most if not all solar panels. There are some AC to AC inverters, although the ones that I have seen are meant to be Grid tie inverters and the voltage is not that high.  Does this make any sense at all?

[Warpspeed]

The problem with ac is that its very difficult to combine two or more ac sources. They must be at the exact same voltage and frequency in order to be able to connect them directly  together.

With dc you can just connect all your mixed dc power inputs through diodes onto a common dc bus that feeds  the inverter.  It is also possible to set the dc voltages at the various sources so that there is a priority in loading.
The grid supplied rectifier being set at the lowest dc  voltage so it is the very last thing to make up any supply deficit.

Whatever source is set to the highest dc voltage will take as much load as it can possibly carry before the voltage is pulled down slightly, and the next available power source begins to contribute.

In my case I have three completely separate 2Kw solar sources (pointing in different directions) all set to the same dc output voltage. If  I need say 2.3Kw, I really do not care if that all comes mostly from only one solar source, or a bit from each, so all my solar output dc bus voltages are set to be the same.

Yes, you can feed in a 2Kw 120v ac gasoline generator into that if required, but it will need a suitable transformer and rectifier to generate suitable dc. 
Your hydo can be, and probably should be a three phase axial flux generator and rectifier, and something to control the output voltage.

The only thing you need to be sure of is that the dc voltages generated by all these various sources is fairly constant and reasonably well regulated. A battery usually solves that problem, but without a battery it is very important that the voltage supplying the inverter cannot ever go high enough to do any damage.

[MAL]

Thanks, and good night, I have to get some sleep.  I hope to have many more conversations with you in the future.

 I hope you have Merry Christmas or Happy Holidays which ever you prefer.

[Warpspeed]

Its starting to get dark here, my solar output just died. 
It must be very late indeed on the Mississippi.

Cheers, and a very Merry Christmas.

[clockmanFRA]

The problem with grid tie these days, is that at one time you were only charged for net usage, any power you fed back into the grid you received a credit.  So you could figure your installation cost against future savings and come up with a realistic payback period, and then be pretty much free from electricity charges after that.

The privately owned power utilities (and their shareholders) expect income to grow every year, regardless. And the greenies generating their own power became a lethal menace to future profit, because the power utilities still have the expense of maintaining and expanding the power distribution network, while seeing a steadily shrinking income.

The first step was to reduce feed in tariff to a point where you have to feed back about roughly ten times as much power as you consume just to break even.  So people just started installing much larger systems to do exactly that.  The power utilities still were not seeing the rise in annual income they have become used to budgeting for.

The next step, at least here in Australia, was to introduce really tough laws regarding how large a grid tie system  could be.  All of which is purely to keep the power utilities profitable.  I don't know the situation in the US, but it probably varies greatly from state to state.

If you decide to install a grid tie system, you suddenly come under very close scrutiny, and with a smart meter they can see exactly what you are doing minute by minute.

In a perfect world you could maybe install a 1.5 Kw hydro and break even in power consumption most months, but that will never satisfy the power utilities.  And what you are actually allowed to do, (or can get away with) is highly variable.  Going totally off grid is a pretty expensive business and just not a viable option if grid power is already available.

Its difficult to know what to do both technically and financially.  But one thing is for sure, the power utilities demand their pound of flesh, and they have the law behind them to ensure they get it.

Hiya Warpspeed.

A nicely written statement, I might add that to my hand outs here in France.  (I will of course give credit).

[OperaHouse]

It is surprising how little power you can live on if daily practices are changed. My utility
says about 15KWH is average a day. At camp we live on about 3KWH and I don't feel that deprived
of comfort.  I've heard it said many times that power usage actually goes up when RE is added
to grid power. The utilities are being squeezed as actual usage drops yet the demand for rapid
service from storm damage increases. The trend in recent years is for utilities to sell off
power generation and concentrate on delivery.  That means that smart metering will closely
track what electricity actually costs. Peak delivery times are going to get expensive. This
is the first time it is technically possible to change rates by the minute.  It is going to
get ugly. Peak load generation can easily cost four times the rate being charged now. Have
you seen those shipping crates at the side of the road with power lines going to them? Those
are gas turbines for peak demand periods. Utilities don't want your solar panels to face south,
they want them to face west.

Scheduling loads is going to be a fact in the future.  Forty years ago many rural utilities gave
discounts for water heaters with timers that only operated at night.  I have a heat pump water
heater that was left over from the HOT SHOT program. That can be found on a google search and
some of the reports are quite interesting. They were trying to reduce all these 5KW water heaters
from coming on at the same time in the morning causing a huge demand.  The heat pumps were only
600W and acted like 1,200W heating elements, could the public get used to a slower recovery. The
utilities are not evil.  They are just trying to get rid of the deadbeats, YOU, that want to use
power only at peak periods and trade them back power when they don't want it. Much like those
people who pay off their credit card every month. You are only an operating expense. Scheduling
is going to become mighty important in the future.

In many ways your solution is similar to mine.  I have limited generating capacity and very little
storage. I have only one car battery in my system.  There is a second house battery which is nearly
defunct, only about 6AH capacity. It gets switched in only when the other battery is fully charged.
In spite of this I am able to operate a fridge, heat water, run the CPAP machine all night, provide
lighting and entertainment.

Charging the battery is the #1 priority. When that has a reasonable charge the fridge can run. Any
excess goes into heating water and anything else. Let's say your system only provides 350W. That
power could be run to the lower heating element of the water heater.  The upper element would still
be connected for high demand. It would be low power, but running all night. The rest of the system
would be a small battery and inverter supplying one or two circuits like refrigeration, lighting
and TV. The battery provides surge capability for starting motors and stabilizes the system. With
moderate demand, it shuts off the water heater to maintain battery voltage.  Should the battery
voltage get too low, power is switched to the grid. For a load like a fridge that doesn't like a
hot swap, it waits for that load to shut off before switching grid or battery source. 

[Warpspeed]

I am slowly adding to and developing my system. 
At the moment on most days my grid power consumption drops right to zero for about thirteen hours per day, and consumption at night is absolutely minimal.

Anyone looking at the load profile from my smart meter can see exactly what I am doing, but might be a bit baffled as to how I am actually doing it, as my system is pretty unique at this stage. 
Once the power utility discovers my little secret, they will definitely not be amused, especially as I am feeding nothing back they can sell to other consumers for profit.

An idea I  thought of just now, would be to control things in such a way that I reduce my grid load during the day, and night, by some fixed percentage instead of having full grid load at night and zero grid load throughout the day.

My load profile would look quite normal, but much smaller than it otherwise would be.  It should be possible to greatly reduce grid consumption without it being too obvious.  I need to think about this a bit more how best to do it technically.

it  should be possible by controlling the solar voltage going into my inverter dc bus, so it goes up and down to keep  some fixed proportion of total load current coming from the grid. 

My consumption at night is quite low, about 1Kwh, and a battery to reduce that to even less need not be that large.
I think there are some interesting possibilities with this.

[MAL]

Hi WarpSpeed, 

I have read many times about the need to match the load to the generator.  You are the only one that has been able to get it through my thick skull what that actually  means.  There should be some kind of award and recognition for an accomplishment of that magnitude...but there isn't. 

It sounds like what you are doing could be accomplished with off the shelf equipment, but I have no practical experience in power production.   

[Warpspeed]

Any limited power source such as a turbine (wind or water) or a solar panel has an optimum loading factor where it can produce the maximum amount of output power.

You can do a simple thought experiment. 
If your turbine is running completely unloaded, it is not producing any usable power output by definition.
Its certainty creating rpm, but zero torque is being extracted.
If you lock the turbine solid into an infinite load, it is not producing any power either. 
It may straining producing a lot of torque, but as rpm is zero, there is no actual power production there either.

Power is force x distance, or more conveniently torque x rpm.  There will be some combination of torque and rpm where power peaks. Under loading or over loading away from the peak reduces power.

So you build your hydro turbine, and couple it to an axial flux alternator, and rectify the output to generate some unknown (at this stage) output voltage.   You then place this in a likely spot in the river.

There will be some dc output voltage created as the whole contraption rotates.

What you do next is start placing a series of increasing electrical load onto the output, measuring both the output voltage and the output current.  The power going into the load will be measured in watts, which is volts multiplied by amps.

You will find that as you gradually increase the electrical load, power will at first increase, but only up to some peak value.
Increasing the electrical load beyond that point will reduce the measured output power.

So you do the test and work out what combination of output voltage and output current is the most efficient operating point for your floating turbine, as it now is.

The problem will be that, at different times of the year, the water flow velocity will vary, and your peak power point will be slightly different.

That is one problem.  The other problem is that the optimum operating point for the hydro is nothing like what you might need to power your inverter.

There are two ways to fix that, either mechanically or electrically.  Mechanically you could alter the gearing to the axial flux generator, if there is any gearing. Or you could do it electronically by stepping the voltage from the generator up or down to suit your inverter. Or perhaps a combination of the two.

But its a pretty essential step to match the generator to the load whatever power system you have.
Because there are so many unknowns, all you can really do is assemble something and test it, then make whatever changes seem necessary to get it closer to the ideal.

[Bruce S]

Hi Bruce, 

I am not sure it is a good idea to give out my address on the world wide web, but if you promise not to tell anybody, that's Iowa that we are looking at across the river.

I gotcha! I thought it looked a little familiar. Our daughter was stationed up in Vinton, IA for a short year. Sure am glad Hwy 61 got bigger, driving behind a Combine was NOT fun!!


 

[MAL]

Thanks to all of you guys,

I will definitely need to revisit this topic as I get closer to completion. 

As it is right now I felt I needed to do some more reading...I was just guessing on things like rotor size, wire gauge, gear ratio, etc...I decided to read through all Chris Olsen's posts, and I am very glad that I did.  It gave me the chance to get to know many of the people on this site, and the passion that many of you have for RE.  I can't help but to feel a great deal of respect for all that you do here.

If Chris is not going to write a book somebody else should, there might even be a movie in there some where...I mean he is the guy that tore up the box, used it for his CAD soft ware(cardboard assisted drawing) ...and he must have used whatever was in the box to heat his home. 

However it was very disappointing to find all of the broken links and missing pictures from the earlier days.

The light bulb is not yet fully illuminated, but there was a flicker,  I believe that I will be doing a ferrite  generator with crammed poles and high rpm.

Thanks again and feel free to comment.

Dave

[Warpspeed]

Keep at it Dave,
You usually start out with only two solid pieces of information, the amount of required electrical power, and the flow velocity of the river.
Its then a case of designing a mechanical system of sufficient size (and specification) to do the required  job.

Hint, the amount of power you can extract will be proportional to the flow area you can tap into.  That should be the starting point.
One horsepower =  pound feet per minute divided by 33,000

Suppose your river flows 33 feet per minute.
You will need "something" that is large enough to create 1,000 lbs of pull from the flowing water to generate one horsepower.
One horsepower (in theory) equals 735 watts, but you will be fortunate to finally extract half of that as electrical energy.

If its a paddle wheel, the submerged paddles must have sufficient area to generate that 1,000 Lbs of pull.
A bit of experimentation with dragging things through the water and measuring the amount of pull with a spring weighing scale might be a reasonable starting point. That, and measuring the flow velocity.

The faster the river flows, the less actual pull you need to reach any specific power.

Give it a go, and see how the numbers turn out.
It will at least give you an idea of the practicality of the whole plan.

[MAL]

Moderators, let me know if you want this to be moved to the Hydro forum

Hi Warpspeed

How did you know that was going to be my next question?  I have been trying to understand the relationship between horsepower, watts and torque in layman's terms.  I have seen the equations on paper, but I can't understand what it means as it relates to my project(math with letters isn't natural )  Chris Olsen talks about torque at the shaft or available watts from a particular prop.  If I am going to use one of his designs I need to be able to figure  if can be powered with a reasonable sized machine that can be pulled up on the beach.

I found an undershot waterwheel calculator, but it is telling me that my design has 0 estimated energy production.  I am going to have 53 feet of blades in the water. I think there should be some power there.
http://www.borstengineeringconstruction.com/Undershot_Water_Wheel_Design_Calculator.html

 
   

That pasted kinda funny, but the numbers are there.  The bold print is the questions that requires answers in order to solve the calculation.  What Am I doing wrong?  If it helps the proposed design is basically a 4 axle rolling pin with barrels cut for blades.  If somebody understands this calculator it may be useful.  One thing that I did notice is that the RPM is only calculated at 2.1, but it allows me to change calculated numbers.

I can only estimate at this point because the water is (((cold)))

Stream Velocity (FPS)   
1
Wheel Design Diameter (Feet, larger diameters yield more torque and lower RPM)   
6
Wheel Design Width (Inches)   
640
Blade Thickness (Inches, from Blade Stress Analysis Calculator)   
.25
Shaft Diameter (Inches, from Shaft Stress Analysis Calculator)   
1.5
Expected Wheel Efficiency (%, 15-25 with flat or 65-75 with curved blades is typical)   
65
Expected Generator Efficiency (%, 90 typical for PMG)   
75

Maximum Theoretical Power (KW, HP=KW/0.745)   
0.001
Estimated Power (KW, HP=KW/0.745)   
0.001
Estimated Energy (KWH/Month)   
0
Maximum Steady Shaft Torque (Ft-Lbs)   
2.3
Effective Head (Feet)   
0.02
Effective Flow Rate (GPM, CFS=GPM/448.   
372.0
Minimum Optimal Diameter (Feet)   
0.05
Maximum Optimal Diameter (Feet)   
0.09
Working Diameter (Feet)   
5.98
Working Circumference (Feet)   
18.80
Working Cross-Sectional Area (SF)   
0.8
Optimal Rim Tangential Speed (FPS)   
0.7
Optimal Rotation Speed (RPM)   
2.1
Number of Blades   
1274
Blade Spacing (Inches)   
0.18
Blade Width (Inches)   
0.19
Number of Radial Arms   
4
Weight of Wheel (Lbs)   
11948
Maximum Blade Force (Lbs)   
1.6
Maximum Shaft Force (Lbs)   
11950.0
Maximum Blade Bending Moment (In-Lbs)   
85.8
Maximum Shaft Bending Moment (In-Lbs)   
955997.3

[joestue]

The amount of power you can get is the additional head you create, the amount the water slows down.

1fps flow rate in a wide deep river might be say, 1 inch per 50 feet of slope. Almost nothing can be extracted from such a flow.

If you plug 10 fps into that calculator you get recognizable numbers, but I haven't tried to verify the power output against the calculated head created by the waterwheel


Notice that it is suggesting you make a .1 foot diameter water wheel....

[MAL]

Hi Joestue,

I am obviously not sure, but one thing that I observed is that the RPM looks significantly wrong...and why would the calculator allow me to change the results.  I suspect there is something that I entered wrong or don't understand. 

Tell me where I am wrong. If all else is the same water has more power than wind.  A 10 MPH wind is just a breeze.  10 MPH flow of water will carry you away. 

[MAL]

Notice that it is suggesting you make a .1 foot diameter water wheel....

I don't see that, and why would that make sense?...larger would be more torque.

[Warpspeed]

The difficulty with an undershot wheel is it usually assumes watter running down a slope that has a reasonable amount of speed and kinetic energy.

A large mature river is usually a large very slow moving enormous thing, and that will be your problem.
I have never seen the Mississippi, but I believe it is not exactly like white water rapids !
Near the bank I would expect it to be fairly slow moving, but I could be wrong.

Most hydro turbines assume a dam of some kind and a sufficient head of water that has a reasonable drop.
The weight of the falling water is where the power comes from. X tons of falling water per second, or whatever.

With a large slow moving river you need to trade off water velocity for massive collected torque.
That is going to require enormous deep and wide paddles, with a large enough wetted area to provide sufficient torque.

The slower the flow, the more enormous the wheel needs to be.

[MAL]

Hi Warpspeed,


I have it figured with 2' by 53' blades. If you had a sheet like that coming at you in 5 MPH current, I don't Think you could stop it.  Yes it is slow 4 or 5 MPH on average.