2.2 Optimising solar energy collection

In the northern hemisphere, a surface should face south to collect as much radiation as possible, and must be tilted towards the Sun at an angle depending on the latitude and the time of year that most solar collection is required.

As you can see from Figure 6, in summer, when the most radiation is available and solar energy collection can be maximised, the tilt angle should be less than the latitude. In winter, when you may need more solar energy, the tilt angle should be more than the latitude angle.

Figure 6 Optimising solar collector tilt for different seasons

Fortunately, the effects of tilt are not particularly critical. Similarly, the effects of orientation away from south are relatively small. For most solar heating applications, collectors can be faced anywhere from south-east to south-west.

This relative flexibility means that a large proportion of existing buildings have roof orientations suitable for solar energy systems. This conclusion applies to both solar thermal systems and the solar photovoltaic (PV) systems to be described in Week 3.