Solar thermal technology

Solar thermal technology

As Thailand situates in the tropical zone, we can tremendously benefit from usage of solar energy. Varietal technologies have been invented to harness solar energy, including solar thermal technology used for water heating and drying systems.

The solar water heating system requires solar collector, divided into two types namely flat plate collector and evacuated tube collector.

For flat plate collector, water will flow into the collective pipe from under the plate and then flow through minor tubes that will transfer heat from absorber, resulting in higher temperature of water outflow at the upper-end.  


Figure 1 Flat plate collector (hot water, clear glass, insulator, minor tubes, cool water, absorber, collective intake pipe)

The evacuated tube collector has heat pipe and absorber within it. Heat from sunlight will vaporize fluids at the low-end of heat pipe, consequently flowing up toward the upper-end of the heat pipe. Water at the end of the tube will take up heat from the vaporized fluids, which will now transformed back into fluids and flow back down to the low-end of the heat pipe. The heat exchange process will go on and water that runs through the absorber will gain temperature. It will then be stored in hot water tank or mix with other leftover heat from other devices such as air-conditioning units, steamer, flue etc. This type of collector requires heat exchange equipment.                              



Figure 2 Evacuated tube collector (Solar energy, hot vaporized fluids, vaporized fluids, transform heat to water, water, heat pipe, absorber, vacuum between internal and external glass tube

The solar drying technology comprises of transparent glass and wall to allow sunlight to pass through and directly dry substances, creating natural flows within the dryer.

Indirect solar dryers will use fan to take in heated air from outside through solar collector, making temperature higher with less humidity than drying substances and eventually dry the substances. However, in case of inconsistence sunlight or speedy process is needed, this system can hook up with other energy sources, such as electricity and biomass fuel, and be called a hybrid system. Dried substances will take heat from hot air that came through solar collector during sunny period and airflow from fans or ventilation units.


                                                           Figure 3 Glass house dryer


                                                                  Figure 4 Hybrid dryer