A solar thermal system captures heat directly from sunlight to provide hot water or space heating, using fundamentally different technology than photovoltaic panels. These systems convert solar radiation into thermal energy through specialized collectors containing heat transfer fluids. Residential systems typically achieve 50-80% efficiency, significantly higher than the 15-22% efficiency of photovoltaic panels.
Components and Operation
Solar thermal systems include collectors (flat-plate or evacuated tube), a heat transfer fluid loop, storage tanks, and circulation pumps. In active systems, pumps force fluid through collectors where solar heat is absorbed. The heated fluid transfers energy to potable water or storage tanks through heat exchangers. In passive thermosiphon systems, natural convection eliminates pump requirements. Systems operate year-round, though output decreases in winter months and cloudy climates.
Applications
Residential solar thermal systems supply 40-80% of annual hot water needs depending on climate and system size. Commercial applications include pool heating, space heating, and industrial process heat. A typical 4-person household system includes 4-6 m² of collector area and a 200-300 liter storage tank. Solar thermal installations require less space than equivalent photovoltaic systems while delivering superior thermal efficiency.