It's obvious that solar panels produce most power when they are pointed directly at the sun. So, any installation needs to provide maximum sunlight onto their surfaces. Ideally, even in winter, they should receive full sun from about 9am to 3pm. Remarkably, there is still a wide range of elevations and orientation that will provide useful output. If your installation placement is limited, it is possible to try passive tracking or even reflectors to enhance light falling on them. If you are considering a DIY solar project, you need to look carefully at how you orientate your panels.
One of the main concerns is working out the correct tilt to allow for differences in latitude and season. If at all possible, adjustable mountings are preferred to maximise their efficiency. A pretty good approximation for the seasonal tilt angle is, latitude minus 15° in the summer, latitude plus 15° in winter, and set the panels at the latitude in the spring/autumn. This ensures the panels are angled to get the most advantage of direct light. It should be noted that most roof angles will allow acceptable panel tilt towards the sun and still provide good average power output over the year, but you are advised to check this.
The amount of power your panels put out is directly proportional to power received from the sun and will vary throughout the day and varies over the year will vary in line with the monthly sun hours. Since this varies not only during the day, but as the seasons progress, solar systems are often rated as an average of the output energy from the peak sun hours. Available solar energy is equal to the daily solar radiation in (kWh per square meter), and since this varies, is usually given as a monthly average.
Not only are solar systems affected by the quality of sunlight throughout the day, any shading will also affect their output. Trees, buildings and high structures can throw shadows that affect part of an array. Not that not only will those cells not work as efficiently, but nearby cells are affected by this (it is effectively resistance in the circuit) and cells may overheat, reducing their effectiveness. Even higher hills on the horizon can limit the "sun hours" in early morning or late afternoon.
One other problem can be, that if a panel or array is not protected by a blocking or bypass diode, when a panel stops producing power either due to shade, clouds or night, current can flow out of and drain your batteries.
Don't forget that the distance your panels or array are from the controller or storage must also be taken into consideration. Long cable runs can be affected by the simple resistance of the wire and there will be power loss between the array and the batteries. One solution is to wire the panels in a series to provide greater voltage(but lower amperage), you will then need to balance the output to your battery stack.
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