Solar energy is most promising alternative to the existing environment polluting conventional fuels and abundunt source of renewable energy. Solar thermal collectors are the medium to harness the solar energy to get converted it into thermal energy. Evacuated tube solar thermal collectors are most efficient design which shows better performance and productivity even at very elevated range of temperatures. Therefore, researchers are always carrying their work to propose the more efficient and effective design. Present work reviews the literature which mention the design modifications to further enhance the productivity and performance. However, it cannot be denied that operational factors are also very important aspect. Reported work primarily covers the modifications followed to improve absorption of solar energy by means of absorber design and reflector selection. It can be concluded with the study that U-tube type ETC and CPC reflectors are optimum design to offer enhanced productivity and performance.
Evacuated tube collector, Heat pipe, U-tube, Helical tube, compound parabolic collector