Wind powered swimming pool

[frackers]

Thought I'd make a start on documenting my 10 footer project so here goes.

Requirements

Maximum of 1kw of wind power to drive one of two 1kw pumps on my swimming pool.

Assumptions

Since the power is mostly being used as soon as it is available, minimum storage is required. No big deal if the filter or solar pump doesn't run for a couple of days due to there being no wind.

No dump load required since the pool pumps ARE the dump load. They will always be available to take the excess power from the battery bank when it gets up to a pre-determined point. I'll probably put in a 'crowbar' arrangement so that if the battery bank get more than 2 volts above the normal load cutin point, the generator output is shorted - either that or if the inverter fails to start then a short is applied a couple of seconds later.

Building blocks

 * 10 footer as per Hugh Piggott "How to build a wind turbine" with 24volt stator from Otherpower, set to furl at 1000w

 * Tower - I have a choice of 4" thick wall steam pipe at about 11m high or a few sections of 140mm irrigation pipe to get to 15m high. The latter is my best choice but nothing has arrived on site yet from a mate!!

 * charge controller to start an inverter at 28volts and cut out at 22volts (using the basic 555 design to start with but later using Dallas 1-wire DS2438 battery monitor chips)

 * Overcharge protector - probably a relay and a zener diode to start with to short the output of the genny if the battery bank over volts

 * Battery bank made from recovered 150amp/hr truck batteries - aiming for 8 in series parallel for 24volts at a nominal 600amp/hrs (but nearer 300amp/hrs since they are pretty rough)

 * Pump controller which juggles the demand for heat from the solar panels and minimum dosing of the chemicals each night but ensuring that one pump will ALWAYS load the inverter when it becomes active but avoid connecting the inverter to the mains!

Eventual integration

• More CAT5 cable round the property to allow statistics collection of the state of each battery in the battery bank using the DS2438 chips
  
• Collate generator output with the weather station to see how it varies through the year
  
• More intelligent controller using the 1-wire chips
  
• More intelligent control of the pool pumps so that minimum water temperature etc can be maintained by using mains power if required
  
  

Pictures of each block should be available for posting by the end of Feb (by which time I hope to be test flying the genny)

[jmk]

 Just because it's a 1000 watt turbine doesn't meen that you will get 1000 watts all the time. Most of the time it will only bring in 50 - 100 watts. Your going to need fifty to just keep your battery charged without any loads. A 1000 watt load is going to drain your batteries pretty quick. I have a 12' turbine and wouldn't be able to run my pool pump from my wind turbine. I have a hard time running 250 watts. You may have a better wind site though?

[jmk]

 You will definitely need a dump load! You can't keep up with the wind. You will be plugging in your pool pump and unplugging it all the time just to keep your batteries from getting drained. When you aren't around to plug in the pool pump your batteries are going to boil. Your better off matching your system to a load that is the size of the system, like around 200 watts.

[frackers]

Note the last item in the list of parts - a pump controller that ensures there is ALWAYS a pump to take the load.

[frackers]

You're quite right on the 1000w - thats the furling (max) I expect to get from it. I'm betting on about 5kw/hrs per day so thats 5 hrs of pump time on average.

Having said that, we've had kilowatt winds for the last 2 days (35km gusting to 50km) with not a cloud in the sky and temperatures in the mid 20's and we had the same last weekend as well. It gets a bit wearing at times but thats what its like on the Canterbury plains!! (described by the local council as a high wind zone - and they're not kidding).

Cheers

[Flux]

I agree with JMK that you will need an incredibly good wind site to keep up with your pumps.

If you could get dc pumps then you would be in with a far better chance. The cube law of a centrifugal pump matches wind power fairly well. A dc pump would be working much of the time even though it would be rarely on full rating. An inverter driven ac pump intended for constant speed would be a poor match.

Flux

[Flux]

Perhaps I should have made it clear that my scheme would not include a batter in normal operation. You could still charge one during windy periods and extend pump time in low wind periods, but the turbine would directly drive the pump at variable speed normally, using all the available wind.

Flux

[frackers]

I'm going for the battery to smooth out the availability of power - rather than the norm of storing the energy until I want to use it and dumping any excess, my scheme is to store it until I have a useful amount and use it automatically there and then.

In this manner (so goes the theory!!) if I get 4kw/hrs of power in a day then my pump will run for about 4 hours, spread throughout the day as the battery bank gets sufficient charge. This is certainly enough to keep the water clear.

The beauty of the system is that the timing is not critical at all - in fact if I go for a couple of days of no wind, so I get no filtering of the pool water, then it's no big deal.

I'm making 2 overrides in the pump controller - one is if the solar controller (which looks for the solar panel to be 4c higher in temperature than the pool) wants to run its pump then it will use the inverter power if its available. If I have no wind then I could end up with a pretty cold pool so I'll have a manual override that will use mains power if necessary and just use the filter pump as the dump load.

The second override is the dosing of chlorine etc which is handled by another controller (which has various solenoid operated valves). This will be set up to run for one hour each night. If there is battery power then the pump will already be running, doing its job as a dump load. If not then mains power will run the pump.

This area is where a more intelligent controller will be useful - to predict that the chemical cycle is due in half an hour so allow the battery bank to charge for those few extra minutes or if the pool is getting cold then automatically use mains for the solar pump to push the 45kw of heat into the pool (its amazing how quickly 50sq.m of bespoke neoprene solar collector warms things up!)

Concerning the use of DC motors - I seriously looked at that option but whilst it works great for the wind genny, its a large capital cost and the extra cost of a mains charger (or 24v 40amp supply) to provide mains backup really is a deal breaker :-(

[frackers]

Another week, another bunch of setbacks :-(

The problems this time are the magnet rotors came out of the molds about 5mm too big so they foul on the studs that hold the stator - guess I should have done the measuring and drilling AFTER I completed them. A bit of hacking with a router bit in the drill press and spinning the rotors on the hub up against it will trim them up (I have no lathe)!

Next issue was deciding that the varnished blades would suffer in the sun (VERY intense here in NZ) so a white oil based  gloss paint is the answer. The problem there was that the etching primer did just that - it worked just like paint stripper on the varnish and made a complete hash of the finish. I've had to strip back to bare wood and start again. At least it was only the test blade that has required all the extra work - I'm skipping the primer on the other blades and going straight to a good quality undercoat after sanding the varnish well down for a good key.

The blade hubs are next, the tail being cut out and primed ready for its final top coat, drilling and mounting on the tail boom.

Positive progress has been in the cable clamps on the yaw bearing, rectifiers mounted on the heatsink, the arrival of 50m of 85amp flexible starter/welding cable for the run down the mast and the promise of more 150amp/hr truck batteries. Also complete are the 100amp ammeter/voltmeter for monitoring and most of the pump controller parts have arrived. Also sourced a bunch of bakalite 63amp fuses and a 3 phase switch to park (short out) the genny from the local reclamation yard.

Just paint and assembly for the generator and with the rectifiers and batteries ready I'll be ready to test fly in a week or so :-) Hopefully no more setbacks now, its just finding the time with the drought broken by a week of rain, the mowing in the orchard will start again!!

One extra job I might do at this stage is a mechanism to manually furl the mill. I'm thinking that a bit of bicycle brake cable to handle all the changes in direction involved with having a cord (or high tensile fence wire) down the mast that pulls the tail up to the back of the hub. I'll get some pictures together once I've scrounged up the parts.

[TomW]

robin;

Ain't learning fun?

You really learn when you mess up. Seems those lessons stick.

Thanks for the update.

Best of luck on the project.

TomW

[elvin1949]

Tomw

 I think he has the bug.

robin

 It's incurable.

Seems like you are having to much FUN.

later

Elvin

[frackers]

I am :-)

No time to resize pictures at present so you'll find them at

my web site where you have the choice of scaled or full size pictures.

[frackers]

More progress with the Loctite going onto the magnet rotors which I eventually set up with a depth gauge (see my item about levelling nuts

here ).

A kg of lead on one of the blades was required to get the balance right but as can been seen from the picture, its a fair way out on the blade. A quick trip to the local tyre company has provided me with 3-4kg of used lead balance weights that I'll melt down tonight to make a nice big chunk up against the hub.

With the tail complete I'm also able to show a view of the complete mill. (we have 6 cats...)

Hoping to do a trial flight this weekend - hooray!