Our outdoor main panel does not have a ground bar, but there is stranded bare wire that leaves the panel and goes through conduit into the ground. We want to add breakers to this box for a spa panel, pool pump and maintenance outlet. Do we have to add a ground bar to this breaker box or can we attach our ground wires to the bar on the right side, where that wire is attached that goes into the ground?
This is your main panel, where the one-and-only neutral-ground bond occurs: the incoming neutral wire from your electric utility attaches to the same bus bars as your local ground rods. You may land ground and neutral wires on either of the screw-terminal bus bars in your picture. You already have one: the large black wire with white tape attached to the left-hand bar that is the neutral feeder to your indoor sub-panel.
One limit to remember is that panel instructions typically allow two ground wires per screw on those bars, but only one neutral per screw, and never mixing of ground and neutral under the same screw. But that shouldn't be a concern for you since you have ~40 ground/neutral bar screw positions and only 8 breaker spaces, so you have no need to double up anything to save screw positions.
