Use case: Solar Collector for Water heating

Adsorber for Closed System

Solar collectors are exposed to strong temperature fluctuations. If the outside temperature drops towards 0°C in winter and at the same time air inside the collector heats up to around 20°C due to solar radiation, condensate forms on the inside of the glass pane. This condensate impairs further ingress of sunlight and thus the performance of the collector. A ventilation dryer counteracts this by drying the air that enters beforehand.

How a solar collector works

In a solar collector, the carrier fluid is heated by sunlight. Therefore, the heart of the collector are pipes that are exposed to sunlight. To increase the energy yield, the pipes are installed in a heat-insulated housing with a glass cover – taking advantage of the greenhouse effect. Sunlight passes through the glass cover with minimal loss and is converted into heat when absorbed by the tubes. At the same time, the glass cover is an effective barrier for this heat, so that the temperature inside the collector is higher than the outside temperature.

Condensation in the collector

During the operation of a solar collector in winter at an outside temperature of 0°C and an average humidity of 50% rH, air binds 8.6g of water per 1m². Assuming that a collector now heats up to 20°C inside due to solar radiation, the condensation temperature would already be 9.2°C. We therefore recommend taking precautions to ensure that the heat gain of the collector is not also impaired by condensate during the season, which is not very sunny anyway.

Decentralized adsorption dryer

A breather dryer can be used to reduce the moisture content of the air in the solar collector and maintain it at a permanently low level. As an externally mounted unit, the adsorber is the only interface with the ambient air. The air sucked in during the cooling process is completely dried beforehand – so there is almost no moisture in the collector. In addition, the dew point also shifts into the negative temperature range. In the above example to -30°C to -20°C. This allows the collector to be operated over a much wider temperature range without any loss of performance.