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Collectors are the most visible components of solar thermal systems. In addition to evacuated tube collectors, Viessmann also offers flat-plate collectors for residential, commercial, and local government buildings. These two collector options are similar in that they both utilize free and virtually universally available solar energy for heating and hot water.
Furthermore, they are made of corrosion- and UV-resistant materials. However, the design and operating principles of these solar collectors differ. Read on to learn what makes Viessmann’s Vitosol flat-plate collectors unique.

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Viessmann flat plate collectors

Design and functions of Viessmann flat-plate collectors

Powerful flat-plate collectors are a great addition to any heating system. These collectors consist of an absorber and a casing with a protective panel. The difference lies in the details: the casing of the Viessmann flat-plate collector is made of a curved aluminum frame. In the Vitosol 200-FM model, this frame can be custom-made and painted in a RAL color. The standard frame is dark blue. The seamless casing ensures a tight fit and maximum collector stability.

The cover, made of special glass, is highly transparent, allowing a large amount of solar energy to penetrate. Furthermore, Vitosol flat-plate collectors feature a puncture- and corrosion-resistant rear panel and highly efficient thermal insulation. The heart of the collectors is the absorber—a winding tube through which the solar fluid (solar medium) flows. Above it is the absorber panel, coated with ThermProtect.

How does sunlight turn into heat?

Flat-plate collectors operate based on a circuit diagram. When sunlight hits the surface of the flat-plate collectors, it heats the solar fluid circulating within the tubes. The solar fluid then transfers the heat to the hot water cylinder or heating buffer tank. The cycle can then begin again.

On days with abundant sunlight, flat-plate collectors can absorb large amounts of energy and temporarily store it in the storage tank. If no energy is removed for a period of time, the collectors risk overheating. This occurs because the storage tank can no longer absorb energy. An intelligent absorption layer protects Viessmann flat-plate collectors from this risk.

The difference between standard and switchable absorbers

Viessmann’s patented ThermProtect technology prevents further energy absorption after a certain temperature is reached, when the solar cylinder is fully heated. When the response temperature is exceeded, the crystalline structure of the absorber layer changes, greatly increasing the rate of thermal radiation and reducing collector performance. This significantly reduces the stagnation temperature, preventing vapor formation. When the collector temperature drops again, the crystalline structure returns to its original state. Solar energy can then be absorbed as before. The change in the crystalline surface structure is infinitely reversible, meaning it is completely reversible. ThermProtect also provides a larger overall surface area compared to conventional flat-plate collectors.

Advantages

In general, the highly efficient Viessmann Vitosol 200-FM and Vitosol 100-FM flat-plate collectors are characterized by the following:

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ThermProtect protects against overheating at high outside temperatures and low heat output

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High solar coverage

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Suitable for backup central heating and domestic hot water heating

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High tightness thanks to a curved frame with a glass retaining strip

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Quick and easy installation thanks to push-fit connectors made of stainless steel corrugated pipe

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Suitable for various installation options: on the roof, on a flat roof, inside the roof and on the facade

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Suitable for horizontal and vertical installation

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Attractive design with the possibility of individual design by painting the Vitosol 200-FM in RAL colours

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UV and corrosion resistant materials for all components

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Vitosol

Flat and tubular collectors

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Product range for flat plate collectors

Viessmann flat-plate collectors offer a variety of installation options. They can be installed both horizontally and vertically. Installation on pitched roofs is also possible. When replacing a boiler in a residential building, a combination of two flat-plate collectors and a solar cylinder is often the ideal solution.

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