In this article we will know about the types of solar collector. We will discuss about the concetraticon collector.
Working of concentration collector.
Concentrating collector is a device to collect solar energy with high intensity of solar radiation on the absorbing surface by the help of reflector or refractor.
Need of Orientation in Concentrating Collectors
Such collectors generally use optical system in the form of reflectors. A concentrating collector is a special form of flat-plate collector modified by introducing a reflection (or refracting) surface (concentrator) between the solar radiations and the absorber. These types of collectors can have radiation increase from low value of 1.52 to high values of the order of 10,000. In these collectors radiation falling on a relatively large area is focused on to a receiver (or absorber) of considerably smaller area. As a result of the energy concentration, fluids can be heated to temperatures of 500 C or more.
Orientation of sun from earth changes from time to time. So to harness maximum solar rays it is necessary to keep our collector facing to sun rays direction. This is the reason why orientation in concentrating collector necessary. This is achieved by the use of “Tracking device”
Type of Concentrating Collectors
The different types of focusing/concentrating type collectors are:
- Parabolic through collector.
- Mirror strip collector.
- Fresnel lens collectors.
- Flat-plate collector with adjustable mirrors.
- Compound parabolic concentrator (CPC).
- Parabolic dish collector.
- Heliostat collector.
Parabolic trough collector.
The principal of the parabolic through collector which is often used in focusing collectors. Solar radiation coming from the particular directions is collected over focusing collectors. Solar radiation coming from the particular direction is collector over. The area of reflecting surface and is concentrated at the focus of the parabola, if the reflector is in the form of a trough with parabolic cross-section, the solar radiation is focused along a line. Mostly cylindrical parabolic concentrators are used in which absorber is placed along focus axis.
Mirror Strip Collector
A mirror strip collector has a number of planes or slightly curved or concave mirror strips which are mounted on a base. These individual mirrors are placed at such angles that the refracted solar radiations fall on the same focal line where the pipe is placed. In this system, collector pipe is rotated so that the reflected rays on the absorber remain focused with respect to changes in a
Fresnel lens Collector
In this collector a Fresnel lens is used in which linear grooves are present on one side and flat surface on the other. The solar radiations which fall normal to the lens are refracted by the lens and are focused on the absorber. Both glass and plastic can be used as refracting materials for Fresnel lenses.
Flat-plate Collector with Adjustable Mirrors
A flat-plate collector with adjustable mirrors. It consist of a flat-plate collector facing south, with mirrors attached to its north and south edges. If the mirrors are set at the proper angle, they reflect solar radiation on the absorber plate. Thus the latter receives reflected radiation in radiation in addition to that normally falling on it. In order to make the mirror effective, the angles should be adjusted continuously as the sun’s altitude changes. Since the mirrors can provide only a relatively small increase in the solar radiation falling on the absorber, flat-plate collectors with mirrors are not widely used.
Compound Parabolic Concentrator (CPC)
The compound parabolic concentrator. It was designed by Winston (and Baranov). It consists of two parabolic segments, oriented such that focus of one is located at the bottom end point of the other and vice versa. The receiver is a flate surface to the apertures joining of two foci of the reflecting surfaces.
For thermal and economic reasons the fin and the tubular type of absorbers are preferable. It is chained that Winston collectors are capable of competitive performance at high temperatures of about 300 C required for power generation, if they are used with selectively coated, vacuum enclosed receivers.
The maximum concentration ration available with parabolicdal system is of order of 10,000.
- High concentration ratio
- No need of tracking
- Efficiency for accepting diffuse radiation is much larger that conventional concentrators.
Paraboloidal Dish Collector
In this type of collector all the radiations from the sun are focused at a point. This collector can generate temperature up to 300 C and concentration ratio from 10 to few thousands. Its diameter is of the range between 6 to 7m and can be commercially manufactured.these are types of solar collector.
A system equivalent to a very large paraboloidal reflector consists of considerable number of mirror distributed over an area on the ground. Each mirror called a heliostat can be steered independently about two axes so that the reflected solar radiation is always directed towards an absorber mounted on a tower. This type of collector is classified as Central Receiver Collector. This is mostly used in toward power plants for generation of electrical energy.
Advantages and Disadvantages of Concentrating Collectors Advantages
- High concentration ratio.
- High fluid temperature can be achieved.
- Less thermal heat losses.
- System’s efficiency increases at high temperatures.
- Inexpensive process.
Disadvantages of solar collector
- Non-uniform flux on absorber.
- Collect only beam radiation components because diffuse radiation components cannot be reflected, hence these are lost.
- Need costly tracking device.
- High initial cost.
- Need maintenance to retain the quality of reflecting surface against dirt and oxidation.
Hence these are types of solar collector. If you want to know about the types of solar collector you must comment below in comment box.