PV Gap

Elaine Said:

I need a 1/2 hp dc motor and solar panel so that I can replace the motor in my evaporative cooler.?

We Answered:

If the motor is really 1/2 HP, then that's about 400 watts, maybe realistically 300 when running.

Many motors of that size are actually "universal" motors, and will run just fine off DC. I won't give you any guarantees that it will work, and most likely no one will. You would also need to develop about 100 volts DC, which is 4 grid-tie type panels in series. To give margin when the sun isn't absolutely brilliant, you'd probably want 5 or 6 panels. But I don't know what would happen at sunrise, when there will be a very low voltage across the motor. Possibly it would be ok. If not, you'd need a controller to disconnect the panels when the sun isn't bright enough. Also, you would want to have some sort of protection for the panels against the inductive kick that the motor might produce.

This is starting to sound like it would cost a sizeable fraction of $5000 already, with the bulk of the cost in the panels, which would be $500-$1000 each, depending on what kind you get.

It could work, if your goal is to save energy. If your goal is to save money, that sounds difficult.