System Advisor Model (SAM)

Running the SAM simulation gives the overall generation data of our new solar array. The figure below shows total generation in the first year, annual savings on electricity, and the levelized cost of energy of our new system.


 

The simulation output also shows predicted monthly generation based on local weather conditions. The second figure overlays the monthly generation data with monthly load of the HQ building based on last year’s utility bills. In the more moderate months, the array will produce more energy than Tyson will pull from the utility grid.

Single-Line Diagrams

Design Calculations

When creating single-line diagrams for our system, the two primary calculations that will be carried out will be the string sizing of our inverters and conductor sizing. An inverter string is a line of solar modules connected in series that feeds into the inveter. Multiple strings can be tied to the inverter through parallel string input ports. Each of our SolarEdge inverters can support up to 2 strings each. String sizing, which refers to the number of solar modules that can be placed in series on a single string, considers many variables to account for the voltage of the modules falling at high temperatures and rising at low temperatures during operation.

In addition to string sizing, conductors between electrical equipment must be sized properly to prevent excessive voltage drop or fire hazards if the conductors are undersized. 

Equations for each of these calculations are summarized below:

National Electric Code (NEC)

With respect to fire safety, it is required that conductors are sized according NEC Table 310-15(B)(16) “Allowable Ampacities for Insulated Conductors”, which specifies the max allowable current for each standard gauge of wire to prevent failure during operation.

Max short-circuit current values are used to with this table to determine the size of conductors needed to withstand the highest available current loads that the device can output. Together with the voltage drop calculation, these two methods of conductor sizing are used to determine the gauge of conductors needed for each interconnect in the system. Once the conductors are sized, an NEC conduit filling table can be used to determine how many of each size conductor can safely be run in a conduit of a given size.

Single Line Progression

The diagram collections below represent the evolution of the single-line designs for both the HQ PV system and the LLC Powerwall system, as well as the trenching route for conduit run between the solar array and the utility connection for the new PV system. 

HQ Solar Array System

HQ Trenching Route

LLC Powerwall Backup System