1. Solar Collectors
A solar collector is a device that collects and/or concentrates solar radiation from the Sun. These devices are mainly used for active solar heating of water for personal use. The use of these solar collectors provides an environment friendly alternative for traditional domestic water heating which reduces energy costs over time.
There are two types of solar collectors
- The sun rays fall on the outer tube. They are transmitted to the inner tube.
- The inner tube has a selective coating which helps absorb maximum sunrays falling on its surface.
- The heat from the rays is transferred to the fluid flowing inside the tube.
- The inlet and outlet pipes to the tubes are in the manifold.
- The manifold connects several tubes together to make a solar collector.
- Water at 60-65°C can be obtained using this collector.
The Flat Plate Collector works in a similar way.
- Finned copper tubes with selective coating are called as ‘risers’.
- 10 such risers are connected on either side to a copper tube to make a flat plate absorber.
- This absorber is covered with glass and placed in housing. The housing has insulation on the sides and the back to reduce heat losses.
As the tubes get heated, the heat is transferred to the fluid flowing through the tubes.
2. Solar Concentrators
Solar concentrators allow collection of sunlight from a large area and focus it on a point/line or a beam depending upon the equipment used and its application. Solar concentrators consist of mainly reflectors and receivers. The sunrays falling onto the reflectors are reflected onto the receiver. The reflectors thus are made of materials with a very high reflectivity.
The receivers absorb the solar heat from the sunrays and pass on the heat to the heat transfer fluid. The absorbers are coated with a material with a high absorptive to ensure maximum capture of the solar heat.
There are two types of solar concentrators
- Fluid upto 80°C can be obtained using these concentrators.
- The unique shape of the 2 parabola profiles, acting as reflectors, help capture maximum rays.
- These are basically non-tracking concentrators and can be mounted on slating roofs, terraces or on ground.
- If they are built to track, the efficiency increases by 30-40% upon tracking.
- Fluid upto 150°C can be obtained using PTC.
- The sunrays falling on the parabola (reflector) are reflected onto the receiver tube.
- The fluid flowing through the receiver tube gets heated due to the solar heat.
- This is a tracking collector. As the sun travels across the horizon, the parabola rotates, such that it always faces the sun.
- This ensures maximum energy capture.