Solar Field

To view the Trough System Costs page, click Dish Solar Field on the main window's navigation menu. Note that for the trough input pages to be available, the technology option in the Technology and Market window must be Concentrating Solar Power - Dish Stirling System.

The parameters on the Solar Field page define the size of the solar field and the layout of the dish network. To explore the impact of these parameters on the system's costs and performance, change the value of the parameter.

The relevant sections of the thesis Stirling Dish System Performance Prediction Model (Fraser 2008) https://www.nrel.gov/analysis/sam/pdfs/thesis_fraser08.pdf (4.1 MB) are:

•	3.1 Parabolic Collector Model, p 63

•	Appendix A: TRNSYS Parabolic Collector Model, p 152

Contents

►	Input Variable Reference describes the input variables on the Trough System Costs page.

►	Entering Periodic Operation and Maintenance Costs explains how to use annual schedules to assign operation and maintenance costs to particular years in the project cash flow.

Input Variable Reference

Field Layout

The solar field is assumed to be a rectangular field with collectors oriented north-south and east-west.

Variable	Description	Units
Number of Collectors North-South	Number of collectors oriented along north-south lines. Used to calculate the total number of collectors.	-
Number of Collectors East-West	Number of collectors oriented along east-west lines. Used to calculate the total number of collectors.	-
Number of Collectors	Total number of collectors in the field. Used to calculate the predicted system output, the shading factor, and piping distance for pumping loss calculation.	-
Collector Separation North-South	Center-to-center distance between collectors along north-south lines. Used to calculate the solar field area, shading factor, and piping distance for pumping loss calculation.	m
Collector Separation East-West	Center-to-center distance between collectors along east-west lines. Used to calculate the solar field area, shading factor, and piping distance for pumping loss calculation.	m
Total Solar Field Area	The total ground area occupied by the collectors. Used in area-related cost calculations.	m2

System Properties

Variable	Description	Units
Wind Stow Speed	When the wind velocity from the weather file for the current hour is greater than or equal to this value, the concentrator moves into stow position to prevent wind damage. The solar power intercepted by the receiver is zero during this hour.	m/s
Total Solar Field Capacity	Nominal electric output capacity of the solar field. Used in capacity-related cost calculations.	kWe

Array Shading Parameters

Solar Advisor uses the shading parameters to calculate the shading of the concentrator mirror by the dish components and by neighboring dish systems. Solar Advisor's approach to modeling shading is different from the Osborn approach described in the Fraser thesis.

Variable	Description	Units
Ground Slope, North-South	Slope of the ground in percent (rise over run) along a north-south line. A positive slope indicates that for two dishes aligned north-south, the dish to the south is lower than the dish to the north. Used to calculate shading factor.	%
Ground Slope,East-West	Slope of the ground in percent (rise over run) along a east-west line. A positive slope indicates that for two dishes aligned east-west, the dish to the east is lower than the dish to the west. Used to calculate shading factor.	%
Slot Gap Width	Average width of the slot in the mirror perpendicular to the vertical support post. Used to calculate shading factor.	m
Slot Gap Height	Average height of the slot in the mirror parallel to the vertical support post. Used to calculate shading factor.	m

Equations for Calculated Values

Number of Collectors

The total number of collectors is calculated based on the numbers of north-south and east-west oriented collectors.

Where,

NColl	Number of Collectors
NColl,N-S	Number of Collectors North-South
NColl,E-W	Number of Collectors East-West

Total Solar Field Area

The total solar field area is the product of the north-south and east west dish collector separation distances and the number of collectors.

Where,

ASF (m2)	Total Solar Field Area
dCollSep,N-S (m)	Collector Separation North-South
dCollSep,E-W (m)	Collector Separation East-West
NColl	Number of Collectors

Total Capacity

The total solar field capacity is the product of the number of collectors and the engine nameplate capacity on the Stirling Engine page.

Where,

PSF (W)	Total Capacity
PEngine (W)	Singe Unit Nameplate Capacity from the Stirling Engine page.
NColl	Number of Collectors