LAST EDITED ON Jun-04-06 AT 06:52 AM (EST)Ask yourself, "what if?" Electrical safety is not so much about probabilities as it about possibilities and liablities. A 120 vac 20 amp circuit with 10 receptacles on it probably will not be overloaded in a residential setting but it is possible that it can be overloaded. It would most assuredly become overload in a commercial shop setting. That is why a wire with a certain engineered volt/amp. rating is used and then protected by a breaker engineered for that volt/amp. rating as well as the recs. and any device that might possibly become plugged into that circuit.
To the best of my knowledge there is not one charge controller that does all three at once as efficiently as a controller designed for each specifically. PV modules can be disconected from the batteries without harm during charging. Some of the first controllers functioned this way. Wind genny's cannot be disconected while charging and some are designed to produce optimum output in low winds and some in high winds. Water genny's as well cannot be disconected while charging they need load diversions as do wind genny's.
All of this is not to say one could not build a 3 in 1 controller but the 3 three different aspects of charge controll as well as voltages and amperages would have to be carefully monitored. If for example a voltage sensor on the battery had a high voltage set limit that could switch over to heating water, the contactor would have to be able of carrying the highest possible voltage and amperage. That goes for the wire and other electrical devices as well. Then what if the; batteries where charged, the tank of water was boiling and the Sun was shining, the wind blowing, and the water flowing? Well, I suppose if the tank where actully a boiler with all of the saftey requirments it might work. What if elements went out? I suppose the load diversion could be lights. But what if bulbs blew? Or it could pump water. But what if the motor burned up? What if?
All of these things have already been thought out when charge controllers are engineered for a specific task. Things like wire distances can have an effect. Diodes to kept electricity flowing one way. You wouldnt want your hydro genny turning your wind genny into a fan right? Or the PV array turning the hydro genny into a water pump? But hey dont let me squash your dreams. I have heard the Thomas Edison once said "I havent just discovered how to make a light bulb, I have found several ways how not to". I know, I know, I misquoted, but I believe you know what it is I am trying to say.
Calculate just how much power each electrical supply source circuit could produce under extreme conditions. Water - we know would be the most constant because of the penstock, it could produce less energy than normal if anything during low rain times for example. Wind - who can predict the wind? Like the Sun we can average its potential energy output but the extremes is what the electrcal needs to be sized at. We cannot forget load potential either. Could the load ever exceed the average output? What are the load characteristics as compared to the line characteristics in otherwords?
Now if the system you have invisoned concisted of pre-engineered devices such as an AIR wind genny that has regulation built in. A hydro genny that controls water flow accross its turbine to regulate power output. Then all you would is an MPPT controller for the PV array.
Dont forget the liability part of it all. Ultimately if anything goes wrong, it will all be between you and your insurance agent.
