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Solar collectors
Solar collectors are designed to convert the energy of sunlight into thermal heat. The two main types are passive collectors and active collectors. They are most commonly use as domestic hot water systems, but they are also used for a variety of other tasks, such as cooking and producing electricity.The most basic type of collector is the solar cooker. The panel cooker is a simple curved reflective surface that focuses sunlight onto a container. The box cooker is similar but encloses the container with an insulated space to retain heat. The parabolic cooker is a most of the three types and uses the light focusing power of the parabolic curve, which is also found in car headlights.
The most common type of solar collector is the roof-mounted domestic hot water system. While they may resemble photovoltaic panels and are often placed next to them, these collectors are completely different internally. Their main component is an array of heat transfer tubes that carry a fluid, usually water. Plain copper or rubber tubing is often used in the cheaper models, but the better models use multi-layered evacuated tubes. These comprise a central fluid-carrying tube surrounded by copper sheet, inner glass tubing, heat absorbent coating, evacuated space, and then outer glass tubing. This complex, fragile design is optimized to retain heat within the tube and transfer it to the fluid.
Passive solar collectors use convection to move the fluid around the system without the need for a pump. This is called the thermosiphon effect, and requires the collector panel to be tilted and the storage container to be located above it. Water expands and becomes less dense as it heats up, causing it to move upwards through the collector tubes and into the storage container. Gravity causes the more dense cold water to flow through another pipe from the storage container to the bottom of the collector pipes. This cycle continues for as long as the water is heated by the sun.
Active solar collectors use a pump to move the fluid around the system. The pump can be powered by mains electricity or by a large photovoltaic panel. Active collectors do not rely on the thermosiphon effect and do not have to be inclined, making them ideal for flat roofs and walls. Pool heaters are a common application of active solar collection. Pool water is pumped through a large area of rubber tubing mounted on a roof before flowing back into the pool. While not as efficient as hot water collectors, they can easily raise the temperature of pool water by several degrees.
Industrial solar plants use a different kind of collector, one with a parabolic shape and a reflective surface. They are not designed to absorb sunlight like water heaters, but to reflect it towards a point forward of the collector. This focused sunlight is so intense that it turns water into steam, which is then used to drive turbines to create electricity. These plants are also known as solar farms and cover large areas with hundreds of collectors. Some collectors, called heliostats, have sensors and motor drives that allow them to track the sun. The plants built so far have been mostly experimental but increasing energy costs in the future could see them rolled out across the world.
Solar collectors are a cheap and effective means of converting sunlight into thermal heat. They have been used since the 1920's and are a common sight on the roofs of buildings across the world, even more so than solar panels. Passive collectors are primarily used for domestic hot water systems, while active collectors are used to heat swimming pools and provide space heating through pipes installed in walls and floors. As energy costs increase in the future, solar collectors are sure to become an even more common sight.
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Related information
- Evacuated tube solar collectors Evacuated tube solar collectors are very efficient for the purpose of collecting and transferring the solar energy to your home.
- Flat plate solar collector Flat plate solar collectors are glazed and insulated with weatherproof boxes that have dark absorber plates under the plastic covers.
- Photovoltaic cells Photovoltaic cells are used for everything from operating solar-powered calculators to heating air and water in homes and businesses.
- Portable solar panels Portable solar panels are a critical component of solar chargers which recharge your cellphone battery or other power systems.
- Solar cells Solar cells convert light energy into electrical energy through the photoelectric effect and they are often called photovoltaic cells.
- Solar cooker Solar cookers use focused sunlight to heat a small container of food or water. The three main types are the panel, box, and parabolic.
- Solar heating system In solar heating systems, energy from the sun is collected using solar collectors. This creates heat that will heat up liquid or air.
- Solar lantern A solar lantern is a light that uses solar cells to recharge its battery. It includes a case, battery, lamp, and solar cells.
- Solar lights Solar lights work by using the solar panel to charge the internal battery during the day, so that it can power the light at night.
- Solar plate heat exchanger Solar plate heat exchangers are made up of cupro-nickel tubes that facilitate its use in chlorine water, spas, and seawater.
- Solar pool heater The most common type of solar pool heater is the active solar collector. They are have a larger collector area and no storage tank.
- Solar power generator Solar power generators harness and convert solar energy into electrical energy for powering from lights to electrical equipment.
- Solar water heater A solar water heater comprises solar thermal collectors consisting of a network of pipes, and a metal water tank inside a heat box.
- Swimming pool solar panels Swimming pool solar panels perform a similar role to solar hot water panels and can extend the use of a pool in most climates.
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