Anyone built a waterwheel?

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  • Anyone built a waterwheel?
  • Thinking about a microhydro project, low output but continuous achievable with a waterwheel for grid export? Don’t think we’ve got the right profile for a traditional piped turbine.

    Premier Icon cinnamon_girl
    Subscriber

    Sounds intriguing!

    neilnevill
    Member

    In theory you need permission from the waterways I believe. I guess if you were to remove lots of energy or might upset flow down stream. I’ve seen junk yard/ off grid tour m type things on you tube where people use an old washing machine drum and motor to generate a few tens or hundreds of watts, which looks a bit of fun.

    Premier Icon lesgrandepotato
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    We’ve been having a look at this, we have somewhere between 40 and 60 ft of drop so looking at 1kw pelton from China feeding into our thermal store.

    Cheeky boy- No, it’s just in the pondering stage, lgp- I suspect we haven’t got the flow or fall for a worthwhile grid connection so it’d just be a supplement probably. Nn- Also don’t want to impound any water hence looking at water wheels. Have seen the red neck ones on YouTube, i like those but getting the electricity in to usable V/A would be the challenge for grid connected house.

    twowheels
    Member

    Perhaps start with a more modest goal of powering a single appliance with a fairly predictable power consumption like a fridge/freezer?

    Scrap car alternator (geared appropriately from your water wheel) and battery plus basic inverter and a dumb fail safe switch to mains should do the trick.

    That could be it, bodge up a cable reel job and see what juice it knocks out before getting too carried away

    cheekyboy
    Member

    As above car alternator > battery > inverter

    Premier Icon FB-ATB
    Subscriber

    Yes, it maybe not on the scale you intend.

    Waterwheel rotisserie

    CraigW
    Member

    Would probably need an abstraction licence from Environment Agency / SEPA, if you are diverting any water, even if not impounding it. Seems there is a cheaper licence available for small hydro schemes.

    Premier Icon lesgrandepotato
    Subscriber

    We’ve decided against a direct connection. So the approach we’ve taken is to have 500l thermal store. The oil boiler will be set to kick in if we drop below say 50deg and to top out at 65deg or so. The 1kw immersion then can run continuously as the UFH / DHW draws it down.

    We’ve used 500l for 9months heating for 3000sqft. Hoping to halve that or maybe more with the turbine. It’s going to take a few years to wash its face at that rate but we should be able to build the setup for a about a grand. The heating elements and the provision for the immersions is already in place.

    Premier Icon maxtorque
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    First, do the math! No point doing anything till you know how much energy you have to capture.

    You’ll need to know the fall you have (or can realistically leverage) and the mass flow of water going down that fall. The fall can be worked out fairly easily, using maps, or simply a long garden hose with a clear bit on the end (fill it with water, and run it down the side of the stream, the height of water is constant:

    http://www.fao.org/fishery/static/FAO_Training/FAO_Training/General/x6707e/x6707e05.htm

    The flow is harder, but an estimate will suffice. Measure a known length along the stream, say 5m, and time how long a float takes to travel that distance. That’s the (surface) speed of the water. Estimate the cross section of the stream (using a measuring tape) multiply the cross section in m^2 by the velocity in m/s and you’re got the volumetric flow rate, in m^3/second.

    Using the height and the flow rate, you can then easily calculate the fluid power available. Once you have that number, or at least an estimate of that number, report back, and we can start to look at the best method to extract the power available!

    https://www.engineeringtoolbox.com/hydropower-d_1359.html

    Premier Icon maxtorque
    Subscriber

    Depending on the layout of your stream, chances are, any successful project is going to have to include some ‘focusing’ of the energy, ie bringing as much of the flow as possible to a single point, where that flow can undergo a momentum change, and enable you to extract energy from it.

    Back in the day, a “mill pool” did just that, allowing the river/stream to flow under or over a large waterwheel.

    The trick to these projects is to spend as little as possible, because realistically unless you are lucky enough to live next to a massive river you own the water right for, these projects are unlikely to break even. A home made wheel or turbine, driving a modified car alternator, and heating water using immersion heaters should be possible to a) be made completely from scrap and b) be done for a very small amount of money (but a lot of time….)

    Premier Icon lesgrandepotato
    Subscriber

    Fair points Maxtorque. For reference my house is called ‘The Mill’.

    Premier Icon northernsoul
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    Sounds intriguing!

    Indeed! Will read with interest (as a boy I lived in an old water mill that had been converted into maisonettes).

    Premier Icon thisisnotaspoon
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    With regards to sizing, one of the reason jets were used is you can get the benefit of however many meters of drop without having to build a wheel of that diameter.

    Think about how hard generating just a few hundred watts is on the turbo, the water is going to need to work about 5x harder than that to generate 1kw.

    Premier Icon eddie11
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    It will need a hydro power permit and possibly a flood risk permit

    Premier Icon db
    Subscriber

    A small Breastshot water wheel might work depending on the head of water you can achieve.

    More here;

    Waterwheel Design

    Premier Icon lesgrandepotato
    Subscriber

    Not sure about the breastshot design. I can’t see past the pelton / turgo rigs for pico hydro. I reckon a pair of flexi 63mm pipes into a plenum and into the pelton.
    63mm map pipe is available flexi so it’s an easy run with no joints.
    Plenum allows the addition of an air bleed to allow the stop of the turbine without sucking the pipes flat.
    Doing that over about a 40-60ft drop should be somewhere in the order of 500-1000w.

    Because we are dropping it into an immersion which is really just a resistive load then it really doesn’t matter how clean the power is. We’re going to warm water not power laptops.

    twowheels
    Member

    Good post maxtorque. Useful calculator link to see some numbers- 25 litre per s falling 1m * at 80% efficiency is ~200w. That’s more than I expected actually.

    Completely agree on using scrap parts- if you can average 200w or let’s say 5kwh per day, usable power you’re looking at around 5*365*11p~ £200 pa worth of power. Not to be sniffed at but I think you could spend that on:
    £40 – on a good condition used alternator (incl. rectifier etc)
    £50 – making the waterwheel itself (I’m thinking decent quality hardwood like olden days wheels)
    £25 – a big pulley and belt (gearing up to spin the alternator, wants say 2000 rpm min.)
    £25 – materials to make some kind of “chute” (hopefully not fugly concrete..)
    £40 – inverter.
    £20 – battery

    * my guesstimate of a garden stream but I imagination your fall could easily be higher.

    twowheels
    Member

    @lesgrandepotato – sounds like you have considerably more fall (hence power) available than in my estimates! Good point about the immersion heater- do you know if there’s one that would tolerate the 3 phase output of an alternator connected directly?

    Premier Icon lesgrandepotato
    Subscriber

    @twowheels not sure but I’ll have a rummage and find out who supplied our Eco units. They made all sorts of custom heating elements.

    Heatrod! Just remembered.

    Book marked, our house is built on the River Irwell allbeit in the Rossendale valley so have a massive energy source outside our living room window.

    Premier Icon igm
    Subscriber

    If you are grid connecting, it’s probably a simple G83/G98 style connection not a slightly more complex G59/G99 connection at the size you’re likely to install (hope I got those new G numbers the right way round)

    If you’re in the Northern Powergrid patch feel free to PM me.

    Premier Icon keithb
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    Ooh, if your house is called “the mill” you may have rights to impound or use the water under your deeds or some archaic legislation. It doesn’t absolve you of current permitting requirements, but mayran they cannot refuse it if it’s similar volumes to what was originally envisaged.

    Worth checking out, somehow…

    Premier Icon nedrapier
    Subscriber

    Not me, other than incidental waterwheeling, eg cleaning my pedals with a pressure hose.

    You should have a walk round Cragside in Northumberland if you’re ever up that way. Right up your millrace.

    Cheers all good info to chew on, will try and get some measurements tomorrow

    Premier Icon maxtorque
    Subscriber

    Automotive alterantors with the rectifiers removes make good 3 phase sources! A typical alternator can put out up to about 70 volts when spun fast (they go to around 18krpm peak, but you’ll want to keep it around 4 krpm for the max efficiency point, but output voltage will climb linearly with rotational speed (and field current)). You can feed that power directly (as AC) to some resistive immersion elements, but you’ll need to either find some 110V elements or wire a few 240V elements in parallel (per phase) to get a low enough resistance to enable you’re alternator to drive a decent amount of current through them. Typical 240V 3kW immersion elements have a resistance of around 20 ohms (when hot, a bit less when cold), so at say 50V AC RMS from your alternator at 5krpm, that’s 125W per element.

    The beauty of car alternators is that they feature a field winding that is separately excited. Normally, that winding is driven by the voltage regulator, but if you take the regulator off, you can drive the winding with a suitable controllable current source. ideally, you’d measure the rotational speed of the pelton wheel (using a cheap / robust sensor like the cam position sensor or crank sensor from a car) and control the field current to keep the alternator spinning at the design speed (max power extraction point) for your particular pelton wheel, irrespective of water flow rate. You’ll need to look at the lowest loss mechanical coupling to the alternator, as you don’t want the alternator getting (too) wet, but you don’t want the loss in a belt system really.

    Build it all from scrap,use an arduino or similar to control it, and you’ve got a cheap way to get about a horse power out of the river. Not a lot, but if you can do that 24/7 it adds up (6.5 MWhr over a full year if it runs 24/7 at that power level!)

    Premier Icon maxtorque
    Subscriber

    PS, use an alternator off a common car, say a ford, and you’ll be able to buy a heap of them for pennies. Parts like this are so reliable these days most just get mashed up and melted down because there second hand value is so low.

    The “front end” bearing on a modern alternator is reasonably highly rated, because it carries the belt static (tension) and dynamic (engine torsional vibration) loading, and can spin at up to 18krpm typically. As long as you keep the alternator reasonably dry (ie splash guards etc) then i think you could get the pelton wheel mounted directly onto the input shaft, which would simplify things and minimise losses. You can probably remove the airfan that is built into the alternator for a little less loss because you are not running at high load under a hot bonnet!

    The key is going to be to measure all the parts you use, and work out the overall system specifications that maximise efficiency within those parameters. Most critical will be pelton wheel size and speed, alternator speed, and load impedance. Match those and it’ll be a proper job 🙂

    doris5000
    Member

    Not a lot, but if you can do that 24/7 it adds up (6.5 MWhr over a full year if it runs 24/7 at that power level!)

    Unless my maths are completely off, that sounds like…. quite a lot?

    I just checked my leccy bill and 6.5MWH would keep my house going for nearly 5 years!

    Premier Icon lesgrandepotato
    Subscriber

    @maxtorque lots to digest there but it’s good stuff!

    I have 3 1k 240v immersions so we are in the ball park.

    I’ll have a look see what alternators I have in stock in the box of bits.

    Premier Icon maxtorque
    Subscriber

    The “flow” of your calculations is important, because there are somethings you can’t change (like the available pressure head for your water source) and some you can (like the diameter of the wheel etc)

    If you have a pressure head of 10m or more, then a pelton wheel is likely to be the lowest effort choice (because it spins fast, unlike a traditional water wheel, it has a high power density), but there are some practical limitations as we shall see.

    So your available head sets your theoretical (lossless) nozzle velocity via sqrt( 2 x g x h) where g = gravity (9.81 m/s) and H is the head in meters, ie a 10 meter head is a 14m/s nozzle speed.

    For a pelton wheel which is a device that captures energy due to a change in momentum, the tangental speed for peak power is half that of water jet velocity. This is because the water changes direction through 180 deg, and you want the greatest speed drop giving the highest change in momentum, water is doing 14m/s, hits bucket doing 7m/s (slows down by half) then gets flipped 180 deg, slowing the water down by another 7m/s, and exits (theoretically) at 0 m/s.

    So you optimum pelton wheel tangential speed is 7m/s (14m/s divided by 2).

    Now you need to know what your generator curves look like, so you can size the pelton effective diameter to sit at that 7m/s tangential velocity. For a directly connected car alternator. your going to need around 2,000 rpm wheel speed, which is 33 revs per second, which means an effective wheel diameter of just 6.6 cm ( 7/33/pi() ) which is unlikely to be practicable because it will limit the size of the buckets, and hence the size of the nozzle, and hence the water flow rate and the total power of the system.

    So we have our first trade off decision, based on the available head, something we can’t change!

    Premier Icon maxtorque
    Subscriber

    BTW:

    1 horse power is 747 watts

    There are 365 days in a year each of 24 hrs long, so there are 8,760 hours in a year. if we make 747 watts for 8,760 hours, we make 6,543,720 Watt hours, which is 6.5 MWhr 🙂

    Premier Icon lesgrandepotato
    Subscriber

    So depending where we pick up we have a minimum of 10m. Going back to the dam (which would require use of other parties land) could be up to about 40m. It’s comfortably more than a big big tree 🙂

    Premier Icon lesgrandepotato
    Subscriber

    From the culverts we have and the remaining ruin. We reckon the old mill could have had a 20-24ft wheel.

    *buys maxtorque a train ticket and slumps on chaise longue with bolly bought with future earnings*

    twowheels
    Member

    20-24ft wheel.

    Tiny, not worth bothering with.

    Joking aside it sounds like you have some serious power available there if you get decent flow year round. Possibly justifies more than an alternator from a scrapyard!

    Wow. Lesgrandspotatowater. Blaw!

    We can’t match that, maybe 20ft drop over 100m (mixed unitaggedon)

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