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Forum Index : Windmills : Help with a school project
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| Brady Newbie  Joined: 17/08/2017 Location: AustraliaPosts: 8 |
Hello, I've come across other forums covering similar themes before, however none of them have been active recently, unlike this forum. Judging from the posts and articles you guys know what you are talking about, so I wanted to ask you guys a few questions to help me out. Let me start from the beginning. I'm not going to go into detail about criteria and such, but simply put, we were able to explore and make stuff which had to do with something in science, technology, engineering, art and mathematics. We had to find a problem in the world, and attempt to fix it. ANYWAY, our group decided to look into the lesser known forms of renewable energy. We looked into geothermal, kite, wave energy and biofuels. We chose wave energy, and we continued to explore it more so. Our end goal was to power a battery to charge a phone, using the river we had access to. This is still our goal, but we recently learnt that the river, well, doesn't produce any waves.  *sarcasstic clapping While the river didn't produce enough waves, it had some powerful tides. So we looked more into tidal power systems, and discovered underwater tidal turbines. Which used the flow of water to spin a turbine and power a generator. I fully understand that this post is in the "windmill" topic. But from my basic knowledge, wind turbines are very similar to underwater turbines. If this post needs to be moved to another thread please do so, I just couldn't find another thread to put this post in. Let me describe the river before I get into the design of our system. To get across to the other side of the river there is a small footbridge. In the middle of the footbridge is a gate, which only the teachers can unlock. The river itself is relatively wide, but the banks are very difficult to access due to a lot of bush and mud. The most powerful part of the river is in the middle of it, which is hard to access from the banks. Conveniently, the gate of the footbridge is just over the middle of the river. Remember that, because it becomes important to our design later on. Here's a picture of the design we are aiming for  The pole will be attached to the gate, and it will go down under the water. Under the water, on the pole, will be two turbines. Both will be powered by the tides, and we hope to be able to charge a battery. Keep in mind, the is only a school project, it's not going to be titanic in size. The proportions in the image are VERY wrong, and it was only made to give you an idea of what we wanted to do. Our knowledge of motors and turbines are very basic. From my knowledge, the turbine is connected to a large gear, the large gear is connected to a smaller one, to get to a higher rpm, which powers the motor. We are going to make these parts using a 3D printed That's all we've come to understand. Which is where I want your help. We want someone to explain to us, as simply as possible, how this all works. From the turbine design, to the gearbox, to motor and how they are all connected. Also, how would we water proof it? Could last overnight without breaking? We would greatly appreciate a response, Thanks a lot for reading it all. |
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| Warpspeed Guru  Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
Before you even start, you need to find out two things. 1/ how much electrical power you need. 2/ how fast the water flows. You need to find out how much capacity your phone battery has, and how fast you need to recharge it. Big difference between the amount of power needed to recharge it in one hour, and the amount of power to recharge it over several days or weeks. The other thing is how fast the water flows. Is it barely moving, or is it like foaming white water rapids ? When you know how much power you need, and how powerful the water flow is, only then you can begin to size the turbine. Suppose it turns out that it needs to be very large, much larger than the depth of the water ? Or larger than you feel comfortable in building ? So first we need to see if this is even practical. Cheers, Tony. |
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| Boppa Guru Joined: 08/11/2016 Location: AustraliaPosts: 814 |
You really need to find the flow as that will determine the power you will extract from the turbines easiest way is to throw a stick (or anything else that floats) into the center, after having measured out a set distance downstream (say 100m) and time it from launch until it floats past the set marker position Then you will need to find out the efficiency of your turbine prop and that will determine the size turbine you will need (flow rate will give your energy m^2) The other issue is on a river speed of the flow will likely be fairly low most of the time, but alternators/gennies (unless custom built) will likely need fairly high speeds, requiring gearing- which makes it harder for the water to spin the turbine (it's more likely to stall the water directly in front and send most of the flow around the turbine- thats why they use dams as it forces the water to go through the blades) You will almost certainly need to build a small scale prototype and use it to get base figures for your individual setup I have seen plenty of people want to make something like this (I did when I lived on a local riverbank) but not many end up going ahead Remember too that unless it is very small, considerable forces will be acting on your pole mount, so you will have to ensure the bridge itself can handle the load |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
Boppa is 100% correct. No point in building a yacht from scratch if there is no wind. Or building a down hill racer if you live in totally flat terrain. The very first step in any engineering project is to see if its even possible. Cheers, Tony. |
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| Boppa Guru Joined: 08/11/2016 Location: AustraliaPosts: 814 |
Now I dont have to rush off to work, some more ideas about your gearing waterproofing etc longterm waterproofing is a major hassle, if you just want it to run for a few days, then its easier As you are looking at constructing the gears etc yourself, one suggestion I have (from a long time friend who is into microhydro) is keep the sparky bits away from the wet bits as he put it lol He lost several installations due to creek flooding and now uses vertical drive instead- either a variation on Gorlov turbine with the axle extended above the waterline and possible flood zone. His original ideas were in fact very close to your own design, but long term waterproofing and maintenance stopped his following that route As you want to use the pole mount and a horizontal axle turbine design and making your own gear to up the speed, why not think of a right angle bevel drive if you want to experiment with it- that way you keep the sparks away from the wet easily, plus it allows much easier or even no waterproofing required for the generator end which can be mounted up at the bridge end for easier access for modifications/maintenance The bevel gear lets you turn the rotational axis from horizontal to vertical and also allows a change in gearing ratios (to help with speeding up to the speed of the genny) The best bit is it will allow you to run an axle up inside your supporting pole and at the top, it pops back out- ready to either add/change the gearing more or mount the genny- safely out and away from the water- minimizing waterproofing needed By making the bevel gear out of either non oxidizing metals (brass/bronze) or plastics, you minimise the lubrication required, and also the waterproofing needed at the prop end- in fact with the right design and keeping speeds down at the water end- you might find it possible to actually not bother with waterproofing at all and simply let the water flow through the gears and support bushes- acting as the lubricant (at slower speeds obviously) This also has the advantage that if you dont get enough speed out of the turbine blades, you can add extra gearing at the top (belt drive or more cog gearing) to change speeds, plus you can easily get at the genny to maintain or modify it (or even swap over to a new design easily- build several different generators with different number of poles/permanent magnets/ electromagnets etc and by using a belt drive from the top of the axle, swap out each to find the different advantages of each- something not so easy to do with a underwater pod design |
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| Boppa Guru Joined: 08/11/2016 Location: AustraliaPosts: 814 |
One idea for very small scale charging (and would be easy for 3d printing etc) would be getting a 'small' dc motor eg Jaycar 12vdc motor and use that as a basis for experimenting with different props/gearing ratios etc. As you are unlikely to get much above 60-100rpm prop speeds I suspect, you would need to make up a gearbox that could give you a 10:1 step up in speed, and a prop that is big enough to overcome the stalling effect that level of gearing would require (Note that such a small motor would be unlikely to get more than 1/2Amp into a 12v battery- and only then that would be its Max, likely much less look up 'marine packing glands' for ideas on how to waterproof axles passing through into your watertight box if you decide to go that route- There are many ways to do it, most use cheap and simple packing materials like cotton waddiing and grease (altho some actually use water as a lubricant for the shaft) For your power wires either hot glue/sellys silicone sealant or you can use waterproof glands like these waterproof glands (Note you would need 2 of these glands- positive wire goes through one, negative goes through the other- dont use with 'fig8' dual wires, they wont seal) So theres some ideas for you at least to think about edit to add If using a DC motor in this fashion ie a generator; to wire it up you will need a 'anti motoring diode' otherwise when the flow rate is too low; the battery will make the motor turned into a genny back into a motor again and it will discharge the battery trying to push the river along faster! To wire it up the motor/genny will have a + and a - connection; you will have to wire the motor - to the battery -, and in the + wire you will have to put a diode IN4004 will be fine for a small motor like the one mentioned before. The diode is black and has a white stripe at one end- that end with the stripe is connected to the battery +, the other end without the stripe goes to the motor/genny + terminal This stops the battery backfeeding or 'motoring' the generator when the flow is too low (btw I dont work for Jaycar or anything, its just they are the ones I usually buy from and I know their cattledog well, other suppliers can usually be found by a quick google, the links I provide are to show what I am talking about) |
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| flc1 Senior Member  Joined: 20/11/2011 Location: New ZealandPosts: 242 |
Gday Brady, Just a suggestion for a slightly diffrent idea which may be easier to build? useing your pole from your bridge ..mount a floating platform which can rise up and down on the pole,or have a swingarm, and on that platform you mount a paddle wheel, the same as you see on the old paddle steamer boats with gearing from pulleys ,belts or cog gearing. Your generator is on the platform so its not going to be much of an issue to keep the water out of it, you have a wide paddle wheel.. which will give you plenty of power to use with your gearing, just have to test what size paddle wheel you need in regards to how much flow there is in the river..... this is how I would do it . |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
This is a school project, really a practical exercise in putting something together that can be demonstrated to work, without spending a great deal. Ingenuity is probably the main feature, and it should be fairly simple to put together, not requiring much in the way of tools or a fancy machine shop to make parts for it We don't know how deep the water is, or how fast it flows, probably not that fast. So we are going to need something fairly large that is inevitably going to turn very slowly, but generates a fairly high torque, at least sufficient to overcome the inefficiencies in the gearing up process. I agree that all the electrical bits should be kept high and dry and well clear of the water. I see the submerged turbine part as a bicycle wheel with turbine blades attached. How about the fan blades from a pedestal fan, or large multi bladed car radiator fan attached to the spokes with plastic cable ties ? A string around the outside of the rim would make for a fairly efficient way to transmit the very slow motion of the turbine up well clear of the water. I am sure that could all be put together at zero cost and not require much in the way of tools. Now we need a dc generator, which is really just a permanent magnet dc motor. Ideally it should only need to run at very low speed to do the job, making the gearing up process more efficient and easier to do. The most suitable thing I can think of right now might be a treadmill motor. These are quite large, but the advantage is that they are a high voltage permanent magnet motor, that typically run at 180 volts dc at perhaps at 1,800 rpm. If we spin this as a generator up to 1,800 rpm we would get 180 volts from it. But as the speed is reduced, the output voltage also reduces in proportion. For this example 10 rpm for every volt. Assuming we might need about four or five volts we might get away with needing only 40 to 50 rpm to turn the generator. I have no idea how fast the water flows, or what speed the generator must run. But a speed increase of about something like 10:1 might do it. It may even be possible to drive it directly from the string around the bicycle wheel, I really do not know. As Boppa says, a diode will be required between the generator and the battery, but other than that, its about all you might really need. Cheers, Tony. |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
That would be perfect if the water is fairly shallow and fast flowing. Cheers, Tony. |
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| Boppa Guru Joined: 08/11/2016 Location: AustraliaPosts: 814 |
Many microhydro guys use paddlewheels, either undershoot or overshoot depending on location and conditions, and the most common microhydro turbine is in fact a modified paddlewheel inside a housing (being the pelton wheel) A small pelton wheel for home microhydro systems using a small modified car alternator to generate electricity ie a few hundreds of watts up to large ones up to 300MW (amazing what you buy off the internet  from Alibaba.com $10 grand pelton wheel Rainbow Power Company has a lot of details about setting up microhydro and things to look out for, how to measure flow etc |
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| flc1 Senior Member Joined: 20/11/2011 Location: New ZealandPosts: 242 |
I think if you make the paddles large enough ,you could easily gear it up,, there is alot of power in moving water. |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
First we probably need to hear more about how deep the water is, and how fast it moves. A floating drum on the end of a boom, with paddles attached certainly sounds like an excellent idea. Cheers, Tony. |
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| Brady Newbie Joined: 17/08/2017 Location: AustraliaPosts: 8 |
Firstly, I would just like to say that I'm so happy and thankful for the responses I've gotten. I'm confident that my group and I will be able to complete this project. You guys are legendary. I will continue to post as the weeks progress, and I would really appreciate further tips. oh! And before anyone asks! I'm not cheating! Our teachers greatly encourage looking for help on other sources and expertise, and I think I've hit the nail on the head. Sorry I was late to reply. I believe I will be able to access the river, either tomorrow or Tuesday. At that time, We will test the speed of the river. However, the problem is that the river fluctuates ALOT, and very adept to flooding. Sometimes, it can be calm, and relatively slow, while other times it turns into a complete monster! Especially after a rain storm. How could we measure the river speed with often fluctuations? As for electrical power needs, we need to charge at least a battery with a MAh of 2000. But we can go as high as we can handle. In the end, we hope to be able to charge a battery, to charge a phone, from 0 to 100 percent. As for the phone I will be charging, it has a MAh of around 1500. Ooh, and diode and weird bezel gear things. Like this?  The idea of using paddles and a floating platform seem like the easiest to make. Is this design possible?  I love the idea, keeping the generator out of water would been that I wouldn't even need to waterproof very much! I'll suggest it to my team tomorrow! Thanks again, |
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| flc1 Senior Member Joined: 20/11/2011 Location: New ZealandPosts: 242 |
I think you should still have good waterproofing on your system,its close to the water and could still get water on it during storms when the river rises and starts to pump with small pressure waves etc. If you find out what the flow is most of the time then that will be your average and you work with that flow rate, allowing for more of coarse when the river rises and the flow increases. yep diode in the positive lead. And maybe look at a small charge controller to stop your battery from being cooked....not sure if they make them that small, or you could just go with small generator and charge controller and small 12 volt battery with small inverter to plug your phone charger into ha! unfortunatley it cost money , and would that be cheating? That second pic you have there was what I was trying to explain...maybe make the slide ring loose and at the top of the float so its less likely to jam?, or use a swingarm? . look forward to some pics of progress  |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
[quote] And before anyone asks! I'm not cheating! Our teachers greatly encourage looking for help on other sources and expertise, and I think I've hit the nail on the head.[/quote] Successful engineering is not about knowing everything, but about knowing how and where to find (or look up) the answers to problems. Books have been the traditional source, but the internet has now largely replaced libraries as a bulk store of accessible knowledge. Definitely not cheating, but very wisely using the resources that are available. Anyhow... Wild unpredictable fluctuations in water height and speed, lend themselves to the floating paddle wheel solution. The simplest way might be a floating drum with paddles arranged around the outside. If that was mounted on the end of a long forked boom, it could rise and fall with the water height and possibly even survive a fair flood. The drum will need to be perfectly watertight or its obviously going to slowly sink. Easiest way might be to just use a steel or plastic drum and bolt or screw your axle shaft and paddles to the drum and not worry too much about keeping the outer structural part of the drum water tight. Then stuff the drum with small watertight objects to give it buoyancy. Maybe small plastic drink bottles? Whatever you can find that is both light and absolutely watertight, and you can pack a lot of them in there very closely. Cheers, Tony. |
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| Boppa Guru Joined: 08/11/2016 Location: AustraliaPosts: 814 |
The paddlewheel is definitely a good solution and if you use a bicycle rim (a pair actually- one for each end of the paddlewheel) you could further distance your genny from the water, plus gear up to the speed required for the genny from the very likely lethargic paddlewheel speed by using the rim itself as part of the gearing- a rubber belt around the rim, and at the top it goes over the genny pulley, and you could attach the planks/blades to the spokes re the first diagram  The motor would be at the top actually at the deck level of the bridge so easy to access, the axle and pole/axle tube would extend right down to the water and below |
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| Brady Newbie Joined: 17/08/2017 Location: AustraliaPosts: 8 |
I found this thing,  I was thinking of something like that, but larger, and use those Water dispenser containers you find in offices. I would place the motor in the middle of the two containers. I'm sorta confused by that belt system... But I found this video showing me how gears work and stuff, http://www.askaprepper.com/homemade-water-wheel-electric-generator/ Its the second video down. Do you think I could do something similar as that old man? Connected through the motor would be the axle shaft, on either end, over the containers, would be the paddles (I really like the idea of using drums or bicycle rims as the paddle wheel, I'llsee what I've got access to.) I'm going to talk with my team tomorrow about the floating paddle wheel idea, it sounds simpler to make. My question is that would it be Still necessary to test the speed of the river? If it's going to fluctuate a lot and the system will go with the tide, is there still a point to recording the river speed? |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
What he said ^^^^ And a suitable slim and very flexible multi groove rubber drive belt and pulley that should not slip, (even when wet) might be found in a discarded tumble dryer. The drum in a tumble dryer is typically about 20 to 22 inches diameter, and the matching multi groove motor pulley maybe an inch diameter. I believe BMX bikes typically run 20 inch diameter rims. Cheers, Tony. |
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| flc1 Senior Member Joined: 20/11/2011 Location: New ZealandPosts: 242 |
If you did know the speed of the water it may save time with testing. As you bright young sparks should be able to work out from the speed of the water... the gearing ratio needed to get correct voltage. |
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| Boppa Guru Joined: 08/11/2016 Location: AustraliaPosts: 814 |
I was thinking more along the lines of a sternwheeler lol but the twin paddles would work too  paddles could be attached to bicycle spokes via nuts/bolts with large washers, or even with cableties.... One thing you could do is measure the water speed, and if you put an ammeter in the lead to the battery (many schools still have them in the science labs I believe) if not a cheap multimeter with a 10A setting would work as well Then you could chart various water flow rates with the current you get out of it ETA I just noticed- you have your diode backwards in the diagrams above- the silver/white banded end should be closest to the battery +, the unbanded black end would be connected to the motor +  |
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