Solar thermal collectors as the
name suggests are collectors designed to absorb the heat and radiation
from the sun and convert it into thermal energy. There are different
types of solar thermal collectors available, which can be sourced from
the market or can be built by individuals themselves. Solar thermal
collectors are basically of three types i.e. concentrating, flat-plate,
and evacuated tube.
Concentrating solar collectorsare usually used for commercial power production systems, as it can
generate large amount of energy due to its capacity to reach high
temperatures. More often, concentrating collectors is made of parabolic
troughs with a mirrored surface, which helps to concentrate and collect
the solar energy on the absorber tube. The absorber tubes either
contain water or heat transfer fluids. However, since these collectors
are largely dependent on direct sunlight they are not feasible in
places where the sun light is not abundant or in places which remain
cloudy for long periods of time.
Although not as effective compared to other solar thermal collectors,
the flat-plate is the most commonly used collector in a number of
countries. Made of an insulated weatherproof box, the flat-plate
includes multiple translucent or transparent covers and a dark absorber
plate. The pipes placed below the absorber plate have heat conducting
fluids or water passing through them and as the liquid flows through
the pipes, thermal energy is generated due to the heat from the sun.
Evacuated tubes also known as solar tubes are generally rows of glass tubes positioned parallel to each other.
There are various types of tubes available such as glass-glass tubes,
which comprises of a glass tube within another glass tube, the space
between them evacuated of air to form vacuum. Glass-metal tubes on the
other hand consist of a glass tube with a metal plate placed inside,
which is connected with a flow pipe. Such tubes are considered
efficient but they tend to lose the vacuum during the course of time.
Batch heaters are passive solar water heating systems. A batch heater
is basically a huge tank full of water, insulated with glass and
painted with black color. It absorbs the heat from solar rays and heats
up the water inside the tank to generate heat energy. It is among the
simplest and most practical of collectors that can be easily set-up in
any location. Connected to the existing plumbing system, the heated
water flows out of the tank and fresh water enters the tank from the
bottom.
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