Powering An Old Mill - 1.5 Kw Lake District Overshot Waterwheel Project Part 3

Kris do not be too harsh on yourself! the whole wheel looks absolutely amazing.

I’m a 71 year old electrical engineer. One thing I learned (eventually) is that critical path items must be tested before being installed. It’s time consuming and costly to do so, but there really is no reasonable option.

Your 3 amp calculation is really per phase and you have 3 phases, so 9 amps seems realistic to me. You should also find out if the windings are star or delta connected. Resistance of wire varies and you won't get a good value by just considering the diameter. A better approach would be to measure the resistance of each phase then use P = V^2 / R

Kris, You measured a single wire. That is a three phase generator so there are at least 3 wires being used to carry the total 2KW power. You would need to cut open the splices inside where all the wires come together to connect to the outgoing feeds. There could be several parallel windings in the stator. Your cover to keep water off the gearbox and generator is also acting as a "hot box" holding all the heat inside. Louvers, vents and a fan might just be what you need.

Hi Kris, I watched your video last night and I've been following your project. A few thoughts: First, if I was in your situation now, with the added pressure of this being a customer installation a couple of hundred miles up the M6, I'd be exploring the simplest solution first - and for me this would mean getting a PMG/motor manufacturer on board (I have a company in mind) that could help with either a new unit, or a rewind of one of those chinese units with a different winding configuration and possibly a replacement lamination stack. From my experience in PMG design, it looks like (and this is just based on how it appears on screen) that unit/design/size should be able to manage 2kW at ~90-95% efficiency if wound correctly. If you want to try going down this route, I can help you talk to these guys from a PMG design point of view, the first thing they'd need would be a whole host of measurements such as lamination stack depth, slot depth/width, airgap size, target RPM, etc. and with these numbers plugged into their software you should be able to get a quick answer on whether or not a rewind would be feasible. Regarding using an induction motor as a generator - whilst this can work, it's not as simple as a PMG because it needs an excitation voltage to generate, and if you do this with capacitors you will have to size everything for a single operating point/power point and then you have the problem of it being difficult to regulate, and possibly losing excitation and free-spinning. If I were going down this route, I'd be fearing 'opening up a can of worms' and I'd want to be fully testing and proving this in the workshop first, over the full operating range (using a motor-generator rig) before taking it on site. I've been involved in product developments in the past where the R&D spilled out onto a customers site, and for several weeks I was driving backwards and forwards to London every week trying to solve a motor control/stability problem that could've been solved at the lab, so I understand the stress involved. I don't know how to contact you other than this comment section, and after a couple of tries my comment seems to not exist if I leave any hint of my details. Cheers, Andy

Chris take it to a local motor repair company they will rewind it to what you want. You will have confidence it will work.😊

Kris, what a fantastic piece of engineering! Well done and meticulous executed. Before you start redesigning your generator setup however, please consider that this motor can actually do it, based on 3 phase and 0.7mm wire (as several people pointed out in the comments). However, when generating 2KW electricity and 80% efficiency it produces approx 500W of heat. This is the case regardless of the generator configuration. A redesign might improve the efficiency a bit but the heat still has to go somewhere. There are two ways to get rid of this heat: Convection and conduction. Convection transfers heat to the air around it and will require forced air flow. Conduction transfers the heat to the mounting bracket and the frame, from where convection will take over. Water cooling of the frame will reduce the convection needs, making this less dependent on the ambient temperature. A very rough estimate of convection cooling: If the maximum motor housing temperature is 60C and the ambient air is 40C (consider the summer) then there is a 20 degree max temp difference. Newtons law of cooling states that the rate of cooling is directly proportional to the temperature difference. If the surface area of the motor is fixed and the temp difference is fixed then your variable is the air flow. The heat transfer is calculated as: heat transferred (500 Watt) = hc (transfer coefficient) * A (surface area) * dT (20 degrees temp difference). 'A' is the motor surface area (which is enlarged by the ribs). hc depends on air flow speed and surface radiance. For air flow this is roughly 30 W/m^2*K for an air flow of 5m/sec and 40W for 20m/sec (so not linear!). If we ballpark the surface area at 1/10sqm then an air flow of 5m/s will transfer: 30 * 1/10 * 20 = 60 watt. You will need nearly 0.5M^2 surface area with 20m/s air flow to make this work for 20C temp difference. Disclaimer: this has some huge simplifications and should be properly calculated by a professional. Its been over 30 years since I last looked at this so no guarantees on the above. How to improve the air flow? Perhaps a fan blade on the generate pulley will do. It needs an opening in the housing where the fan can draw air inside. A big round hole in the cover in front of the fan would do nicely. This assumes that the air exit through the bottom isn't too obstructed. Probably best to combine this with conductive cooling using some of that water. Summers are getting hot and water stays cooler providing a greater temperature difference to work with. Conductive cooling has its own formulas based on transference of heat through a solid but this post is already long enough. I'd be happy to help bouncing off ideas if you like. Last, you can test this on your work bench by putting a 500W heating element in the motor cover and put a cowl over it. Then cut a hole and blow some air through and see the temp drop. Good luck and I hope your resolve it without too much headache.

Kris, have a rewind done on that motor in thicker wire to give you the 2.5 3kw that your needing. Sure it can be done by a rewind company in the UK and be cheaper then the cost of your time and materials on reworking the mounts.

You are an eloquent testament to the theory that progress is made through an iterative process of failures leading to eventual success. Your consistent positive attitude and wonderful sense of humility are amazing. Keep going!

Hey Kris, the wheel is looking fantastic! some input for the electronics, if its of any addition to what you already know. The difference here is that they specify 2KW but this will be the short term Peak rating not the continuous rating. This is not that unusual to state peak rather than continuous, Chinese or otherwise. Motors, inverter, speaker, power amps always tend to use peak because people love big numbers. It also not just the wire, it is the power density/efficiency the wire you measured will be one of at least two for just one of the phases so current capability is ok (especially as the rating is KWpeak). Running a higher voltage from the motor for the same amount of power (lower current) will reduce the temperature rise in the wires/motor. Double the voltage/half the current but 1/4 the temperature rise of the Alternator. This is also more efficient to run at a higher VDC down the cable to your controller (of course short distance 30M or so this doesn't matter so much but every bit is a hit in over all system efficiency). If you get the output of the alternator to be in the top 1/3 or 1/4 of the operating voltage rating of the Solis DC input for peak RPM of the wheel. Also take advantage of some of the shaft rpm to shift air around inside that enclosure. Hope this helps.

As I am watching my imagination starts to make me smell the welding, (which I actually like.) Ether that or I’m having a stroke. Watching you work is very soothing. Thanks very much. 🙂

I think you have to take a step back and just admire the whole projekt. This is absolutely stunning! Also huge props to the gully builder, that's looking really good!

34:47 The label alone provides for mistrust in the alternator's ability. Otherwise, your work on the wheel, all things mechanical and your commitment to a job well done is inspirational!

You have inspired me to leave London after 18 years and return to the valleys of Wales to get involved in forestry projects. Just need to find a job and a house now!

These videos lower my blood pressure. Not joking. Awesome and purposeful engineering plus the great outdoors. Love it!

Yes, the Chinese cannot be trusted to be truthful in their advertising. I believe this is because of the fear that workers have of projecting facts which management doesn’t want to hear that would make the item more expensive to build. Management has an unrealistic expectation of an output, but the worker/engineer cannot this accomplish due to the reality of the science/physics behind it. It’s an insane system, which is why they have the reputation that they have. Another lesson learned, so now you move on to accommodating the materials that will make your project work. Love your work on everything you do!👍👍👍

Your work is typically so well engineered and thought through; I can see how incredibly frustrating it would be to have faulty (lying) suppliers. Press on young man!

Nothing worse than having to explain to a customer that you’ve done everything to the best of your knowledge, and then to look like a fool because you’ve been lied to by a supplier. I really hope your customer understands and isn’t holding back on “too much” cash. This is what kills small business’, when all you want to do is have a happy customer who will spread your name, but go into the red because of nonsense like this. Head up mate! You’re doing a great job!

Kris you are a one man business, developing an engineering product from scratch. .Don't lose heart, like you said you know how to fix this. You have created an amazing system and you have uncovered a product shortcoming very early in the process really.

Mistakes are a very normal part of any engineering project, don't be hard of yourself and keep innovating, the next iteration will be much better! P.S absolutely loving this series!