Flat plate solar collector can be classified based on by working fluid type such as flat plate solar collector for water and flat plate solar collector for air. The following below will be explained flat plate solar collector that is used in solar water heater systems.
Flat plate solar collector consists of four basic elements as follow:
Absorber has function to absorb solar radiation and transfer heat energy to the fluid. Absorber consists of absorber plate (fin), collector pipe and stem pipe. Absorber plate (fin) serves to expand the heat-absorbing surface. This heat is then absorbed by water in collector pipes which are connected to stem pipe.
- Transparent cover.
Transparent cover serves to reduce radiation heat loss and convection heat transfer from flat plate solar collector to surrounding.
Isolation serves to reduce heat loss of absorber parts that are not exposed to the sun.
- Frame and casing of collector.
This part has function as place to put all of components in position and support the weight of flat plate solar collector.
|Figure 1: Flat Plate Solar Collector|
Heat energy is transferred from absorber to fluid either liquid or gaseous fluid which is then used directly or stored. Usually more than half of the absorbed heat is lost from absorber surface. This condition is caused by re-radiation and convection to the environment. This heat loss can be reduced by using transparent cover plate with glass type because:
- Glass can forward solar radiation wave but cannot absorb solar radiation wave.
- Air space between absorber with glass can eliminate amount of thermal resistance between absorber and ambient air.
The bottom of absorber should be insulated to prevent loss by conduction from bottom and sides. For example, the outer frame and cover plate support must also be isolated from absorber plate and from air space which has temperature above ambient temperature.