In contrast to concentrating technology, solar collectors, like flat plate and evacuated tube, have been developed for heating and cooling purposes in a non-concentrated manner [27].
This technique has become popular within short time because of its efficiency and cost effectiveness [28].
It can be used in areas where weather conditions are poor and solar intensity is low [29].
This system has three mechanisms such as light absorption, transforming and storage.
Copper tubes with insulation are used to absorb solar energy, where water or air is circulated and heated up before returning to storage system.
An efficient modification of this system is evacuated tube
collector where heat pipes are vacuum shield and 20–45% more
efficient than flat plate collectors.