Solar thermal energy can be used to drive chemical processes in such areas as fuel reforming, materials processing, detoxification, catalysis, and photolysis to name a few. This is not a complete list, and new ideas and technologies are constantly research and analyzed to take advantage of the available solar resource.
Here are a couple of examples:
Photolysis is the process in which solar radiation is directly absorbed by reagents to create a certain reaction product. For instance, photolysis can be used for the disinfection of clear water for drinking by placing contaminated water in clear plastic (PET) bottles in the sun for several hours of direct radiation. Through the combined use of increased temperature and ultraviolet radiation, water that contains pathogens, such as microorganisms or bacteria, will become potable as the pathogens are killed by the UV light and increased temperature over the course of several hours in full sun. This process is typically used at small scales for individual household use in the developing world, and is recommended by the World Health Organization for purifying and storing household water.
Photocatalysis uses solar radiation as a catalyst of a chemical reaction. In this case not necessarily solar thermal energy is the main input. Either visible light or ultraviolet components of the solar spectrum can be used to trigger electrochemical reactions or to increase the rate of reactions in the prosence of a catalyst. An example of photocatalysis is photo-catalytic oxidation (PCO). In this process visible and UV photos are combined with the nano-catalytic material to destroy volatile organic compounds, fungi, and bacteria. This approach is applied in sanitation and air purification.
The following reading provides you with an overview if solar chemistry applications:
Kalogirou, S.A., Solar Energy Engineering, Elseveier 2009. Chapter 7. Section 7.3. (10 pages)
This book is available online via Penn State library system