Hi,
I have a 24V 1kw wind turbine that I want to use for heating water in a water tank. The turbine is located about 100m from the tank so running 24V is out of the question. I am thinking of using an inverter to send the power from a buffer battery at the bottom of the tower to the tank at 230V, no need for as thick a cable then. I have searched for comments about using an inverter as a dump load and they all say not to do it but don't really say WHY not to do it!
In the water tank I will have three heating elements rated at 250W, 500W and 750W. I have built a controller that monitors the battery voltage and can turn on the elements so that I have outputs of 250W, 500W, 750W, 1000W and 1500W. With the wind I have here the turbine is rarely putting out less than 200W which 24hrs a day every day should at least pre heat my water tank (40 gallons). As a back up incase the inverter fails or shuts down or something else goes wrong I might use a Xantrex C60 or morning star diversion controller at the battery bank to take over and dump load to an air heater or some sort of resistance at the bottom of the tower.
The controller will sense the battery voltage and turn the elements on as needed, I have a bit of hysterises so that they are not rapidly turning on and off. Can I get away with using a modified sine wave inverter (i.e. a cheap one) or will I have to go for a pure sine wave? I think the MSW might not handle the loading and unloading and eventually fry the electronics where as the pure sine might handle better with the toroidal transfomers? I can get four 3000W MSW inverters for the same price as one 1800W pure sine wave but I suppose you get what you pay for. I am hoping that I'd get a good life expectancy from a pure sine wave inverter?
Some might say that I should just change my stator to a higher voltage and feed the elements directly from the turbine, it is an option but I have the stator already built and I also want the inverter for expansion in the future so that if I ever want to run the electricty in the house then I'll have that option by increasing my battery bank.
So, can anyone suggest to me why I should not go with this plan or why it won't work? Is there any other way of going about it that I am missing, using a transformer of some kind?
Thanks for any help,
ruairíhev