Elevation tracking will work if you are 'near equator' (up one side and down the other) as that is close to an equatorial mount there. (40 degrees elevation sounds off for this though, and you will never find the sun at negative elevations, that's pointing downward). As you get more northern or southern, azimuth start to become more important (At the pole, you ONLY need azimuth tracking).
As Upsidedown said, an equatorial mount makes a good single axis operation. It won't correct for the seasonal north-south motion of the sun, but that is small enough, and slow enough that you might not need to automatically adjust for this. It does say that an accelerometer might not be the right sensor, as at higher latitudes you get less signal from it, a rotary encoder of some sort on the equatorial mount is more commonly used.
Having just a simple 'bang-bang' controller (on/off and direction), your control law will be fairly simple, If you are too far from the desired position turn on the motor in the needed direction, and when you get close, stop (don't wait for exactly equals, as you are going to overshoot).
One other issue with using an accelerometer for position measurement here is that while you are moving, that motion will affect the accelerometer reading, making it hard to decide when to stop.