Solar collectors are one of the best devices for capturing and transforming solar heat into electricity. Different types of solar collectors are available to suit the needs of various applications. They range from small-scale residential units to large-scale solar power plants. Check out this website to know more.
Flat Plate Collectors
Flat plate solar collectors are a common domestic hot water solar heating system. They're a great choice for many applications because they can be installed quickly and efficiently without requiring special equipment.
They're also cheaper than evacuated tube collectors, which can be expensive to build. Additionally, they can be less expensive to operate in warm climates because they don't require antifreeze or other insulating fluids.
A typical flat plate solar collector comprises a black absorber plate mounted in a hermetically sealed frame. The absorbing plate has a grid of conduits to circulate the heat transfer fluid.
Heat transfer fluid (water or water/antifreeze mix) is pumped from the water storage tank through the bottom header, then up the risers to the absorber plates. The absorbed heat is transferred to the fluid and stored in the tank. Some collectors also include a series of tubes to further circulate the fluid.
Evacuated Tube Collectors
Evacuated tube collectors capture the sun's energy in parallel glass tubes. This allows them to absorb more solar energy than flat plate collectors.
They also offer superior performance on cloudy days and at night in contrast to flat plates only perform well during the day when sunlight is at its peak, which makes them less efficient for heating water.
Unlike flat plates, evacuated tubes are hermetically sealed and do not suffer from corrosion problems. This design ensures the maximum efficiency and reliability of these systems.
The tubes are made from transparent borosilicate glass coated with an anti-reflective and selective surface coating (ALN/AIN-SS/CU). It creates a vacuum between the two walls of the tube, which eliminates
conduction and convection losses and prevents condensation inside the collector. This makes the system more efficient and helps it operate better at higher temperatures than flat-plate collectors.
Parabolic Dish Collectors
Parabolic dish collectors are one of the most efficient solar technologies available.
These systems use mirrors mounted over a parabolic-shaped dish to concentrate the sun's rays onto a receiver placed at the dish's focal point.
The heat energy collected from the solar radiation is transferred to a working fluid in a receiver, which is then used in a Stirling or Brayton cycle engine. This system is called a parabolic-dish cogeneration (PDC) power plant.
Compared to a parabolic-trough system, a PDC offers significantly higher solar-to-steam conversion efficiencies (in the 70-80% range) and better scalability and flexibility. They also require the less clear ground for installation and don't need as expensive rooftop support structures.
Parabolic-dish collectors have the potential to be a high-efficiency distributed solar thermal technology for many applications. They are particularly useful for heating, drying, industrial hot water, and electricity generation.
Concentrating Collectors
Concentrating collectors (concentrator solar power systems or CSP) convert sunlight into thermal energy using mirrors and lenses to concentrate the sun's rays. They can be used in various applications, from heating water to producing electricity.
The solar radiation reflected by the lens or mirrors is focused on an absorber tube, transferring the thermal energy to a heat transfer liquid. Pressurized water, steam, or thermal oil is typically used as the heat carrier fluid.
These systems can operate at much higher temperatures than non-concentrating technologies, but they require a sophisticated tracking system to keep the sun's rays focused on the absorber. Also, the high-temperature requirements of these systems make them less reliable and robust than flat-plate solar thermal technology. In addition, they are more expensive than their non-concentrating counterparts. Moreover, manufacturing these systems produces potent greenhouse gases contributing to global warming.
