A solar collector is an object that is used to collect energy from the sun, which it does by absorbing solar radiation and converting it into heat or electricity. The material type and coating on a solar collector are used to maximize solar energy absorption.
Solar collector types
Air based (transpired and non-transpired types)
Dark perforated absorber captures solar energy. The fan then draws in air through collectors of small holes and canopies. Later, air is collected in a cavity between the solar collector and building wall. The air is distributed through the building. The air has an improved quality at low cost. The duct should be located near south wall as part of the building envelope. Aluminum louvers (shading devices) are also used as solar thermal collectors.
These collectors absorb the sun's radiation through a heat transfer liquid. The radiation is converted into useable heat energy by pumping the heat transfer liquid through a heat exchanger that transfers the energy to the water heater system.
- Non concentrating like solar ponds (solar radiation is absorbed and trapped on the bottom of the pond. temperature inversion due to density of salt water), flat plate and evacuated
- Concentrating like Trough, Dish and power tower
Flat plate unglazed & Plastic Absorber collectors
- Low cost
- Low temperature (0-10c rise)
- Seasonal pool heating
- Poor performance in cold or windy weather
Flat plate glazed
- Simple construction
- Insulation and glazing prevent heat loss
- High temperature operation (0-50c rise)
- Selective surface improves performance
- Moderate cost
- Heavy and bulky
- Easier to integrated
Evacuated tube collector
- Very good at reaching high temperature (10-150c rise)
- No convection heat loss
- Difficult to integrate into roof
- Suitable for cold climates
- Cost more money than flat plate
Domestic solar water heating system (DSWH)
Passive: use gravity and tendency for water to naturally circulate as it is heated through the system without a pump. They are generally more reliable and easy to maintain.
- Batch heater: these are the simplest solar hot water systems. Their simple design consists of a tank of water within a glass covered insulated enclosure carefully aimed at the sun.
- Thermosyphone features: Natural circulation of water, Flat plate collector, Collector placed below the storage tank, Hot water is taken from the top of the tank
circulate waters or other heat transfer fluids through the collectors.
Active types are two direct and indirect models
Solar district heating systems
The surface to volume ratio of a central storage tank is much better than that for distributed storage systems. So the storage losses are much lower and even permit seasonal heat storage. Solar district heating is also an option if room heating is to be covered by solar energy. Nevertheless, there are higher piping losses with a central tank.