Timber that would be the best way to do it as you could put the rectifiers on the tower and then run one main in with those higher voltages from all the combined dc current. The gear ratio would have to be figured out as the higher voltages would let the turbine not see a load until higher rpms and you would lose the low wind output because the gearing would be lower thus needing more wind for even hitting the GT voltage..
Hi Murray and Bluejay, It looks like Larry is running the multiple DC inputs in parallel to gain the amperage with voltages averaging. I was referring to running the multiple DC inputs in series to gain the voltage with amperage averaging. Supposing you have a central location for AC input from x number of turbines.(e.g. your power panel) You have x number of rectifiers at that panel (so far, exactly as Larry has). Instead of running x number of positive DC leads to the positive buss bar and x number of negative DC leads to negative buss (as Larry has done, nicely I might add), you would connect the leads in series, positive of one rectifier to negative of next rectifier etc. and only one lead to the positive buss and one lead to negative buss (for eventual connection to grid tie). Voltage would be higher and amperage lower but potential (Watts) relatively equal to Larry's setup. This would, however, give you the higher voltage you are looking for. I don't know what would happen in a power outage but I would assume the proper switch/ dump load would still be effective in governing the turbines. Dave
I knew what you were thinking exactly about running the dc in series at the rectifiers to up the voltage but I am unsure how the rpm of the turbines will react. That could spell disaster for geared units if the right gears are not in it.. Direct drives would not have the same risks... :mrgreen: :ugeek:
Hi Bluejay, It's good to get your input about "geared units", although I am fairly mechanically inclined, it's difficult for me to easily grasp the relationship between load and the effect it has on the turbine(s) when geared. I would imagine that knowledge comes with much trial and error. Am I correct in assuming that the effects are, in general, an amplification of the effects seen on direct drive units? Thanx, Dave
Well these big blades are only rated at 450rpm. Your right timber in your understanding,The faster the motors starts to turn the then hits the limit you set(12v or 24v,48 etc) and thats were resistance starts. The farther away from the amount you are drawing the harder it is to spin faster. Thats where the larger blades give you the torque to push into it more and make more juice. I have found that until the blades are spinning fast enough to "catch all the air in the diameter" it wont speed up easy. Once that speed is there its like stepping on the gas and watching it speed up quickly. By adding more mills in paralle the top voltage making turbine helps bring up the laggers by letting less resistance be there for them until they blip into the lead. The leader would be experiencing the most resistance while the lowest volt one would have the least..Thats all my observations while 2 were running at the same time :ugeek:
Ok first as GOD as my witness,these photos have not been altered in any way except shrunk to fit on this site.. First is a picture of what a real time snap shot looks like... And here is the strongest gust recorded in its memory.. This was the month I had 1800 lbs of concrete ...over 100 mph wind,Thats power and I live in a spot that gets crazy winds 2-3 times a year like this.. I was actually looking at this things features to see what the winds were here last week when it crashed..News said 70 mph gust.. I know how I am gearing and doing guide wires along with a attachment on the tail to be able to lock it out of the winds these couple times a year..The blkades are far enough away from the tower so climbing it in high wind to hook the tail and locking it will be nerve racking but safe...
Man those gusts, that is some scary stuff ! I know if given a choice you would prefer not to use the wires so maybe you can find a balance and have your ground eyelets in place, have your wires attached to the tower but do not attach them to the eyelets until there are big wind warnings .
Mur I just didnt want them stretched all over the yard so I will be putting foot long eyelets with a steel anchor bolted on into the concrete pad.. The angle will be small but I can tension it on every side and do belive this will help to stabilise it.. I always have warning when we will have Gale wind warnings like this so I can plan... Wonder if a windy frame with a furling tail will survive here.....Hmm you should let me test one for half price windy :lol:
Bluejay, Have you considered testing your bird with Direct Drive first? Ithink this will get you some good baseline data - Watts vs Wind Speed. Then follow up with a simple 1:1 ratio gear train. This with prove how much of a NEGATIVE impact there is just from introducing the Gear Train. Collect data again - Watts vs Wind Speed. Then slowly increase the Ratio up to 1.1:1, 1.2:1, 1.3:1, 1.4:1 and collect Watts vs Wind Speed at each ratio until you see Watts Peak for your "Rated" Wind Speed. Then sit back, analyze the data and ask yourself "Is ANY Geared Ratio more efficient than Direct Drive?" Step to methodically analyze a "Geared-Up" Bird ... Step #1) Direct Drive = Collect Base-Line Data Step #2) 1:1 Ratio = Determine Negative Impact of Gears & Chain Step #3) Starting at 1.1:1, slowly increase the gear ratio to find Peak Watts at Rated Wind Speed Step #4) Sit down with all of that data and analyze. I think 2:1 is too high a ratio and is beyond PEAK efficiency since you will transmit less than half the torque generated by the rotor into the genny.
I have been flying a direct drive for a while now and am unimpressed.Takes more wind to hit 22v than the geared units ever did.. I tested 40 t sprockets to 16t-18t-20t-24t and the best performance was from the 20t gear(on a 24v system).. the 18t sacrificed some low wind watts but had the highest top end wattage.The 16t would not spin the blades fast enough to catch all the wind to allow it to speed up quickly In wind that will not get me my 200 rpm direct drive(24v) the geared unit would be putting out 30-50w @(100rpm).. I just need to figure out a heavy duty furling tail system for the 10.6 blades..
The high winds and a direct drive windy nation pma will put out good juice,so far with the new system I seen a high of 481 watts with no furling yet. Hopefully the 5 lbs isnt to much for the size of tail. I am happy with overall performance but see the lacking in low winds that used to produce with a geared unit..
WHAT IF ... You put two put TWO 500 Watt generators on your 10.6' (1KW) blades - direct drive? (Can your 10.6' Blades handle two 750's ? WOW!) Then your wire the DC outputs in SERIES. That would that double your Voltage at low RPMS. Will two 500W/750W genny's create more load on those big 10.6' Blades to help control the top end speed? Too small of a load on those big blades can lead to a Run-Away condition = SELF-DESTRUCT! And you don't want to furl at low speeds and loose all that immense power at high speeds. Can two 500w/750w generators extract 1KW/1.5KW vs 640W @ 25mph wind speeds before furiling begins? Basically, this idea is similar to your 2:1 gear-up but it uses electronic voltage doubling instead of a mechanical gear doubling. Upside for 2 Genny idea ... 1) You get the 2X Voltage Boost at the low end 2) You get more braking force to control the blades top end speed - allowing more time to furl 3) Allows you to furl at a higher wind speed to capture even more power Down Sides (there is always a down side) ... 1) Extra cost for 2nd genny. 2) Extra weight for 2nd genny. I am wondering if a single Direct-Drive High Voltage Generator mated with an MPPT Wind Controller is another way to solve this Low Voltage issue?
