Variant Menu: System Definition > Collector Array > Collector > Select

In this section, you can configure the collector parameters. Here’s a summary of the content:

Entering the collector areas and specific heat capacity

• Gross Surface Area: This is calculated from the external dimensions of the collector, although the specific collector characteristic values usually relate to the active solar surface rather than the gross surface area. The active solar surface is typically derived from reports by testing institutes.

• The active solar surface in flat-plate collectors can be the absorber area or the aperture area, depending on the test institute. In the case of evacuated tube collectors, the active solar surface might be a theoretical value.

Collector – Thermal Losses

Variant Menu: System Definitions > Flat-Plate / Tube Collector > Losses / Thermal Losses

Calculation of thermal and optical collector losses

• The energy absorbed by the collector and output to the collector loop minus heating losses is calculated based on several factors, including solar irradiation striking the collector, average collector temperature, air temperature, and incident angle modifier.

• Optical losses are taken into account through conversion factors and incident angle modifiers. These losses determine how much of the irradiated energy is lost through reflection on glass and the absorber. The remainder is absorbed by the collector.

• The heat transfer coefficient (k) indicates how much heat the collector releases into the environment per square meter of active solar surface and temperature difference between the average collector temperature and the environment in degrees Kelvin. It is divided into a simple part (k_o) and a quadratic part (k_q), which influences the collector’s efficiency.

• The specific heat capacity measures how quickly the collector reacts to irradiation and is expressed in Ws/m²K.

Collector – Optical Losses

Variant Menu: System Definitions > Flat-Plate / Tube Collector > Losses / Optical Losses

Calculation of optical collector losses of a tube collector

• Conversion and incident angle modifiers determine the optical losses, i.e., how much of the irradiated energy is lost through reflection on glass and the absorber. The conversion factor indicates how much energy is absorbed when irradiation is vertical to the collector surface area.

• Incident angle modifiers describe additional reflection losses when the sun is not positioned vertically above the collector surface. The modifiers are calculated differently for flat-plate and evacuated tube collectors.

This information allows you to configure collector parameters and understand the factors affecting thermal and optical losses.

For more details and specific data input, please refer to the complete documentation.