ASK THE EXPERTS: Wind Turbine Problem

Intermediate
Checking wiring connections at 120 feet is no easy chore.

My wind turbine is producing power, but when I connect it to my regulator, I cannot detect any DC current and it does not charge my batteries. It’s the second regulator—both of which were new—that I have been unable to detect any DC voltage out of. What am I doing wrong?

Nicholas Godwin • via e-mail

I suspect that when you say it is producing power, you mean voltage. As long as a battery is connected, it acts like ballast, preventing the turbine’s voltage from rising much higher than the battery’s voltage. If you are running the turbine without the battery connected, be careful—the voltage will rise with the increasing speed of rotation, can soon become hazardous and damage equipment.

Assuming there’s an adequate wind resource, these problems are likely to be due to defective wiring or a damaged controller. You can check the turbine wiring by shorting the wires together—called a “brake switch”—connecting all three phases together. The turbine should slow drastically and then come to a standstill.

If it is producing voltage but there is no short-circuit current, there’s likely a poor connection in the wiring. Test your connections by trying to pull them apart. Check that they are all clean and tight. It is also important to have good connections to the battery, or the battery charge controller could be damaged by the rising turbine voltage.

Make sure your controller is suitable for a wind turbine. A wind turbine connected to a solar controller’s input is likely to damage the turbine. Connecting your turbine to any controller without a battery connected is also likely to damage it.

In most cases, a wind turbine will be connected to the battery via a rectifier and a fuse or breaker, and not directly via a charge control device. You will need a diversion controller, which diverts surplus energy into a dump load to protect the battery from overcharging. These vary from crude relays to sophisticated PWM controllers, such as the Morningstar TriStar or Schneider Electric’s C40. You must configure them for diversion rather than for solar control mode. It is good practice to use a separate fuse or breaker for each—the charge-control electronics and the wind turbine.

One exception, in situations where the controller lies between the turbine and battery, is the MPPT controller, but very few of these are suitable for wind systems. You would need to protect this controller using a voltage-limiting device like the MidNite Solar Clipper.

If you don’t understand, or lack confidence, then buy the wind turbine and controller as a package and follow the instructions. Always make sure that the dump load and the battery are both securely connected; use fuses or breakers before you connect a wind turbine to any controller; and put the brake switch on before working on these connections.

Hugh Piggott • Scoraig, Scotland

Comments (5)

Ed Hutchinson's picture

If there is a PV system also connected to the same battery the PV charge controller may keep the wind system shunted. I could only get power out of my turbine in strong winds until I "floated" the wind turbine output voltage just above the PV voltage in light winds. It is simply a capacitive coupled three-phase voltage tripler, that saturates at about 150W. It drives up the voltage until it draws current which clamps the voltage at that level.

Hugh Piggott's picture

Hi Ed, Some wind turbine controllers work by "shunting" the turbine to a load directly (often using a big relay). It's better to use a PWM controller that diverts the correct amount of power to a load in proportion to the surplus power available. Often (unless the wind is very strong) the crude shunting approach will stall the turbine so it slows and produces very little. This is adequate to prevent the battery from overcharging but it makes no use of the potential excess power harvest that could be used for heating water or other applications. I doubt if tripling the turbine voltage will be the most efficient solution to be honest. Using a quality PWM charge controller with settings just below the solar charge controller settings will make sure that surplus wind and solar energy is available for heating purposes, and the battery voltage is held at an optimum level for maximum service life too.

Ed Hutchinson's picture

The polyphase voltage tripler is only used at very low power. It is bootstrapped around the regular controller. It has three capacitors as inputs and they "swamp". But it allows the Whisper 200 to produce between 56 and 62 V in very light wind (the voltage range maintained by the PV charge controller - depending on the state of charge). In light air the turbine P-to-P ac voltage is around 20V which allows the blades to spin but produces no usable energy. When trippled the wind voltage will reach the PV voltage and begin to draw current for either the amount available from wind (and the voltage drops) or until the capacitors are not capable of passing any more (about 150W). Above that power the standard Whisper controller is in charge. In strong winds the blades "self-feather" to an odd helicopter attitude and the turbine will continue to put out 1000 W all the way up to 100mph (which I have never seen here). The shunt is only used if the batteries are fully charged and there is insufficient load. A PWM controller would let the blades freewheel (and probably destroy themselves) during the off duty pulses. Shunting does stall the turbine in light air but when it is blowing hard the heating element draws power to keep the blades loaded. If the batteries are fully charged and the PV system is producing enough to manage the load there is no place to put the wind energy so being stalled is perfect.

Hugh Piggott's picture

hi Ed,
I understand better what your tripler does now. A bit like a maximum power point thing to make the turbine work in very low windspeeds when the battery voltage is too high for the turbine rpm. Neat. I don't think you understood what I meant when I suggested using a PWM controller though. PWM controllers have several modes, one being solar mode where they limit the current coming in from the PV. This is not suitable for wind because it results as you have described in overspeed and overvoltage that would damage the controller. The turbine would overspeed and be noisy. I did not mean that PWM mode. I was talkig about diversion mode where the controller pulses the excess power into a heater in the exact amount required to maintain the optimum voltage. This does not stall the turbine so it continues to produce power as normal and the excess is all harvested as useful heat. Or it can be by those who are keen to use renewable energy to the maximum advantage. A reader recently pointed out to me that a good diversion load is a Willis type external immersion heater that gives very hot water even from quite low power. That's the beauty of using electricity for heating. YOu can get a small amount of very hot water where a solar water heater would give you lots of tepid water. I digress. My point is that a PWM diversion controller will be better for the battery and also give you more useful hot water than a relay based controller that connects the turbine to a dump load directly.

Ed Hutchinson's picture

I forgot about the diversion mode on a good MPPT controller. We have a solar thermal system for hot water and it gets hot most of the year. Nov through March not so much. It is peaked by an electrical element, and that is supported by grid tied PV, but this time of year there is not much PV either. An electric diversion element for the hot water is a good idea (although the cost of the controller would make cost recovery a long term proposition. That never seemed to get in my way in the past! I have been working on a thermal electric generator powered by a pellet burner. Although only 6% electrically efficient with bismuth telluride TEG cells the "waste heat" would be used for radiant floor heat and a high temperature exchanger for domestic hot water taken from the smokestack. The system would run 24-7 for about 100 days. The cells cost about $2.50 per watt but would have about twice as many hours of generation per year as our PV systems. It would provide a steady half kilowatt and produce enough waste heat to heat the entire house except on very cold days. Even at $2.50 per watt they are half as much as I paid for my first PV panels (a long time ago). I am 70 now and this project would probably have a cost recovery well past my expected useful life.... Well, it's not about the money all the time.

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