Solar thermal collectors and applications
Ozone layer depletion
The ozone present in the stratosphere, at altitudes between 12 and 25 km, plays a natural equilibrium - maintaining role for the earth, through absorption of ultraviolet (UV) radiation (240-320 nm) and absorption of infrared radiation [3]. A global environmental problem is the depletion of the stratospheric ozone layer which is caused by the emissions of CFCs, halons (chlorinated and brominated organic compounds) and NOx. Ozone depletion can lead to increased levels of damaging UV radiation reaching the ground, causing increased rates of skin cancer and eye damage to humans and is harmful to many biological species. It should be noted that energy related activities are only partially (directly or indirectly) responsible for the emissions which lead to stratospheric ozone depletion. The most significant role in ozone depletion have the CFCs, which are mainly used in air conditioning and refrigerating equipment as refrigerants, and NOx emissions which are produced by the fossil fuel and biomass combustion processes, the natural denitrification and nitrogen fertilizers.
In 1998 the size of the ozone hole over Antarctica was 25 million km2. It was about 3 million km2 in 1993 [7]. Researchers expect the Antarctic ozone hole to remain severe in the next 10-20 years, followed by a period of slow healing. Full recovery is predicted to occur in 2050; however, the rate of recovery is affected by the climate change [8].
