Wind turbine charge controller

elheffe

hi,
I have been looking at wind turbines on the web and am a bit confused on the purpose of a charge controller. simply if my wind turbine is small scale domestic application, on grid, with a dump load in the form of a resistive element. no batteries. so grid supply goes down and inverter dumps generated power into the element. what is the purpose of the charge controller or do I need it at all since I do not have batteries. I can understand its purpose if I had batteries in an off grid application.

any ideas or websites ye know off with good a explanation would be greatly appreciated.
cheers

quentingargan

You don't need a charge controller, but a different version of a charge controller is the bit that dumps surplus power into a heater, especially during grid outages. It is essentially the same thing...

A voltage measuring circuit usually switches on an IGBT to power the heater when the voltage is above a pre-determined voltage. In the case of a battery charge controller it might be 28.5V, but in the case of a grid tie system, it is usually a bit above the max working voltage of the turbine.

elheffe

got it thanks. could you answer me this, an inverter obviously converts dc to ac from the battery bank. if I was to use an immersion in a tank say 2 kW, would I have to power it from the inverter or could I do it directly from the battery bank. since the inverter steps up the voltage does this mean that I need less batteries as opposed to powering it directly from the batteries themselves. hopefully I explained this correctly. thanks again for your help.

ruairihev

If you want to power the element from the battery bank then it will need to be rated for low voltage (12V,24V,48V..etc whatever your battery bank voltage is). If you use the inverter then an element rated at 230V can be used.

It's not usually a situation of connect the element to the power source and leave it run, if it's a wind turbine system then the best method would be to have a charge controller as you mentioned for a battery system. This senses when the battery is charged and then dumps excess power to the element using Pulse Width Modulation, it's not a simple on off switch but more of a proportional switch, it senses how much power the turbine is putting out and then decides how much of that power should be diverted. This can only be done with a DC source like a battery.

If you go the 230V route through the inverter then the best method would be to have a bank of elements rated at different powers depending on the size of your turbine (maybe a 250W, a 500W, a 750W and a 1000W). You would need a controller then to measure the power output of the wind turbine and switch on the appropriate elements. For example, if the turbine was putting out 1500W then the 1000W and 500W elements should be turned on. You could use your single 2Kw element but if the turbine is putting out 500W and you turn on a 2Kw element then the remaining 1500W comes from the batteries, this will cause the batteries to cycle (i.e. reduces the lifetime of the batteries). The above method should only really be used when the batteries are fully charged.

If you want heating only then forget the batteries and the inverter and the dumpload. Again you would need a bank of different elements rated at different voltages and power, connect these directly to the wind turbine and have a controller decide when to turn them on or off. Hope this helps you out somewhat.
Regards,
ruairihev