Tracking has nothing to do with clouds or weather; it increases the efficiency of the solar panels in the early morning and late afternoon when the angle of a fixed panel is poor. Pretend your eye is the sun, stick a post-it-note on a globe, and rotate it. You'll see the aspect ratio change. Then, pretend your hand is a solar tracker and I think you'll see the difference! Even with a solar tracker, you'll still see less power in the morning/evening due to greater atmospheric attentuation (lower sun angle = shining through more atmosphere), but it will be more efficient than a fixed panel. It also helps account for seasonal differences, but these are less of an issue because the cos of the angle between summer and winter is small.
Solar tracking is typically not economical for a-Si solar panels, though. Solar tracking really comes into its own when using parabolic mirrors to concentrate solar energy, as the mirrors must be perfectly aligned to focus the solar energy on the element. So, if you use a parabolic concentrator, you'd need solar tracking. Otherwise, your customers are probably better off just spending that $15k on more panels because they'll see a better return.
Also, why bother with batteries unless they're off-grid? Grid-tie, and save them a lot of cost, complexity and toxic material!
If they're doing this expecting a positive return on their investment... they're not going to see it. Unless there is a HUGE government subsidy, they're going to lose money on this, and lose big. (Even if there is a subsidy, other tax payers take the hit for them- it's still a financial dead-end.) If they want to do it for environmental reasons despite the loss, that's their call, but please make clear to them that they're not going to get any $$$ returns on their investment. Especially in Canada, wow. They may not even make a return on the energy investment of the panels that far north.
