The Tower and Receiver page displays variables that specify the geometry of the heat collection system. The receiver model uses semi-empirical heat transfer and thermodynamic relationships to determine the thermal performance of the receiver. This allows the model to represent a wide array of geometries without deviating from a hypothetical reference system.

Page numbers relevant to this section from the Wagner (2008) and Kistler B (1986) references are:

The model makes several assumptions about the system geometry:

The model varies the heat transfer fluid mass flow rate through the receiver to maintain the required outlet heat transfer fluid temperature. The model includes several practical safeguards to ensure realistic behavior in the receiver. For example, the mass flow rate through the receiver is limited to the value of the Max Flow Rate to Receiver variable, and the maximum receiver heat transfer fluid inlet temperature is kept at a value below the value of the Max Temp to Receiver variable.

Solar Advisor allows several options for the heat transfer fluid flow patterns through the receiver as indicated by the diagrams on the Receiver / Tower page. The Flow Pattern variable specifies the path taken by the fluid as it passes through the receiver. Options include a full circle around the receiver, a split path around the receiver, and a split pass with a single cross-over.

Dimensions

For analyses involving the optimization wizard to optimize the heliostat field layout, Solar Advisor populates these variables with optimal values. You can change the values after running the optimization wizard, but results will no longer be for the optimal system.

Receiver Height (m)

Height in meters of the receiver panels.

Receiver Diameter (m)

Total diameter in meters of the receiver.The distance from center of the receiver to center of a receiver panel. The width of a single panel is the circumference of receiver divided by number of panels.

Tower Height (m)

Height in meters of the tower structure from the ground, equal  to the vertical distance between the heliostat pivot points and the vertical center of receiver.

Thermodynamic Characteristics

Number of Panels

Number of vertical panels in the receiver.

Tube Outer Diameter (mm)

The outer diameter in millimeters of the tubing that carries the heat transfer fluid through the receiver panels. Typical values range from 25 mm to 50 mm.

Tube Wall Thickness (mm)

The thickness in millimeters of the individual receiver panel tube walls.

Required Outlet HTF Temp (°C)

The temperature set point in degrees Celsius for the heat transfer fluid at the receiver outlet.

Max Temp to Receiver (°C)

The maximum allowable temperature of the heat transfer fluid at the receiver inlet.

Coating Absorptivity

Absorptivity fraction of receiver tube coating. Typical values are 0.91 to 0.95.

Coating Emissivity

The emissivity of the receiver coating, assumed to be black-body emissivity constant over the range of wavelengths.

Heat Loss Factor

A receiver heat loss adjustment factor that can be used when the calculated heat loss value deviates from an expected value. The default value is 1, corresponding to no heat loss correction. The calculated receiver heat loss is the sum of convection and radiation losses from the receiver, reported in the hourly results as Rec_conv_loss and Rec_rad_loss, respectively.

Enable Night Recirculation through Receiver

With night circulation enabled, whenever the radiation incident on the receiver is zero, hot heat transfer fluid circulates through the receiver to prevent fluid in the receiver from freezing. For systems with storage, the system pumps heat transfer fluid from hot storage. For systems with no storage, or when there is insufficient energy in storage, the circulating fluid is heated with an electric heater. The heat transfer fluid is assumed to enter the receiver at the temperature required for it to exit the receiver at the required outlet temperature, accounting for thermal losses. SAM ajdusts the  heat transfer fluid mass flow rate accordingly.

Recirculation Heater Efficiency

With night circulation enabled, the electric-to-thermal conversion efficiency of the heater used to supply thermal energy for preventing the receiver heat transfer fluid from freezing. Solar Advisor calculates the heater electricity based on the required thermal recirculation energy and the heater efficiency, and reports the hourly electricity required by the heater as Par_recirc_htr in the hourly results.

Max HTF Velocity in Receiver (kg/hr)

The maximum heat transfer fluid flow rate inside the receiver. If the fluid velocity through any single panel exceeds this value, the heliostat field is partially defocused until the fluid velocity constraint is met.

Max Flow Rate to Receiver (kg/hr)

The maximum heat transfer fluid flow rate at the receiver inlet. Solar Advisor calculates this value as a function of the maximum heat transfer fluid velocity in the receiver.

Max Receiver Flux (kW/m2)

The upper limit of solar radiation incident on the receiver allowed to be reflected from the heliostat field. Solar Advisor ensures that the optimal receiver size and heliostat positions do not result in a receiver flux that exceeds this value.

Material Type

The material of the receiver panel tubes, typically a stainless-steel alloy.

Heat Transfer Fluid Type

One of two types of solar salt used for the heat transfer fluid, also called the working fluid.

Flow Pattern

One of eight heat available transfer fluid flow configurations shown in the diagram on the Receiver / Tower page. The views are from the top of the receiver, assuming that panels are arranged in a circle around the center of the receiver. Arrows show the direction of heat transfer fluid flow into, through, and out of the receiver.

Materials and Flow

HTF Type

One of two types of solar salt used for the heat transfer fluid, also called the working fluid. You can also add a user defined HTF by choosing the user defined option and clicking the Edit button to open the HTF properties editor.

Property table for user-defined HTF

When the HTF type is "user defined," the Edit button provides access to the HTF properties editor.

Material Type

The material of the receiver panel tubes, typically a stainless-steel alloy. The current version of Solar Advisor allows only one material type.

Flow Pattern

One of eight heat available transfer fluid flow configurations shown in the diagram. The views are from the top of the receiver, assuming that panels are arranged in a circle around the center of the receiver. Arrows show the direction of heat transfer fluid flow into, through, and out of the receiver.