If the 19th century was the age of coal and the 20th of oil, the 21st will be the age of the sun.

Solar energy is set to play an ever-increasing role in generating the form, and affecting the appearance and construction, of buildings. The principal reason for this is that photovoltaic (PV) systems which produce electricity directly from solar radiation are becoming more widespread as their advantages become apparent and as costs fall. PVs are an advanced materials technology that will help us design buildings which are environmentally responsible, responsive and exciting. These will take a variety of forms as shown in Figures 1.1, 1.2 and 1.3. In Figure 1.1 the PVs are part of the roof structure; in the other figures they form the southfacing walls.