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Optimally you want the panels perpendicular to the sun's rays all day, every day. You can't get that with fixed panels, and practically you don't want heat in the summer time. The efficiency is proportional to the cosine of the error angle and that loss of efficiency is very small for errors under 10 or 15 degrees. Its a 30% loss at an error of 45 degrees. That said, I recall the solar collector I built back in 1974 (8' x 24') was sloped about ten degrees more than my latitude (I'm at 42 north so I tilted it 52 degrees). It was really hard to shut down in the summer time and easily overheated in the late spring sun. And water rotted the wood box and structure so its gone. If I was to do that again, I'd go with vertical collector panels and depend (especially at your latitude) on snow reflection or the reflection from a few sheets of foil faced foam on the ground to more than make up for the loss from the angle. Or better, I'd just use double paned windows (not low-e coated) into the house and save on ducting, fans, and that sort of stuff. Thomas Jefferson worked out that if the window area was something like 15% of the floor area the solar heating would be optimum. You have to prepare for storage or wild temperature rises with direct gain solar though. Something like an exposed concrete slab (but insulated at the edges and from the ground underneath) works good, Dark tiles help. Gerald J.
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