.Buildings.Fluid.SolarCollectors.UsersGuide

Information

The package Buildings.Fluid.SolarCollectors contains models used for simulation of solar thermal systems. Top-level models are available for solar collectors based on the ASHRAE93 and EN12975 test protocols. The two models use different models for solar gain, heat loss and data packages. Solar gain and heat loss models are available for use with data obtained from ASHRAE93 and EN12975 test procedures. Data packages containing default values for several collectors are available in packages for concentrating, flat plate and tubular collectors.

Use of the Buildings.Fluid.SolarCollectors models

A model of a solar thermal collector mainly consists of the three following items:

• A package containing ratings data.
• Models for solar gain and heat loss corresponding to the format of the referenced ratings data.
• Parameters describing the installation of the system.

Ratings data describing the parameters of individual collectors are available in Buildings.Fluid.SolarCollectors.Data. All ratings data was taken from the Solar Rating and Certification Corporation (SRCC) website. Data for concentrating, flat plate and tubular collectors are currently presented in separate data packages to improve ease of use. The name of any given collector data package begins with a code stating what type of collector it is. The codes are as follows:

• C: Concentrating
• FP: Flat Place
• T: Tubular

Currently there are no concentrating models on the SRCC website that provide all of the data necessary for accurate use in the models available in Buildings.Fluid.SolarCollectors. Namely, they lack data for dp_nominal, dT_nominal and G_nominal. This data must be obtained from other sources.

There are two test methods for solar thermal collectors. The American standard is ASHRAE93 and the European standard is EN12975. Models calculating solar gain and heat loss using coefficients from both test methods are available in Buildings.Fluid.SolarCollectors.BaseClasses. Users should be careful to ensure that the solar gain and heat loss models used in their simulation match the ratings data entered into the data package.

Finally, the parameters of the system must be defined. Most of the parameters are self-explanatory. The complex parameters are used as follows:

• nSeg: This parameter refers to the number of segments between the inlet and outlet of the system, not the number of segments in each solar thermal collector.
• nColType: This parameter allows the user to specify how the number of collectors in the system is defined. Options are Number, allowing the user to enter a number of panels, or TotalArea, allowing the user to enter a system area.
  • Number: If Number is selected for nColType the user enters a number of panels. The simulation then identifies the area of the system and uses that in solar gain and heat loss computations.
  • TotalArea: If TotalArea is selected for nColType the user enters a desired surface area of panels. The model then uses this specified area in solar gain and heat loss computations. The number of panels in the system is identified by dividing the specified area by the area of each panel.
• SysConfig: This parameter allows the user to specify the installation configuration of the system. Options are Series and Parallel. The handling of dp_nominal is changed depending on the selection.
  • Series: If Series is selected it is assumed that all panels in the system are connected in series. As a result there is a pressure drop corresponding to dp_nominal for each panel and the effective dp_nominal for the system is dp_nominal * nPanels.
  • Parallel: If Parallel is selected it is assumed that all panels in the system are connected in parallel. As a result the fluid flows through only a single panel and the dp_nominal for the system is dp_nominal specified in the collector data package if the collector field has a mass flow rate equal to per.m_flow_nominal.

References

• ASHRAE 93-2010 -- Methods of Testing to Determine the Thermal Performance of Solar Collectors (ANSI approved)
• CEN 2006, European Standard 12975-1:2006, European Committee for Standardization