Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
If you are going to connect directly to the solar panels, they put out DC power, so you need a DC pump.
Depending on configuration you can alter the output of the panels, so research how much water you want to move, which pump can do that, then configure the panels. This set up will only run during the day. The pump needs to be OK with varying power levels in low light. One example of where to get a 12v DC pump is a sporting goods store that has supplies for fishermen. The use a pump like this to keep the bait and the catch alive.
If you are using solar to charge a battery, then running the pump off the battery you can get a cheaper pump because you will be feeding controlled power to the pump from the battery. It will not change day or night. You can run this type of set up 24/7.
You will need to figure out how many batteries (and what size) you will need for the 'worst case' scenario: How long is the longest time that the solar panels might not be able to produce enough power to charge the batteries (cloudy weather reduces the output). You will need to get a controller that will supply the pump with whatever voltage etc. it needs. All these extras will add to the cost. Might be cheaper to get the higher priced pump that runs directly off the solar panels.