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Daylight Design Guidelines - Illinois

Updated over 2 weeks ago

Offset = 75% min <> 120% max

Minimum System Size DC = 5.98kW

Maximum System Size DC = 17.94kW

Production Factor Min = .80

Illinois Equipment

Panels: Aptos 460w

Inverters:

Inverter sizing must match battery count and system size

A critical load panel is required for every system

Refer to equipment combinations here

Settings in Aurora

Prior to design work, please align your simulation settings with the following:

General Settings

  • Simulation: Auto

  • Shading Engine: On

  • Use LiDAR Shading: On

  • If tree removal is indicated in the project submission, please turn off LiDAR, model in trees according to LiDAR and Google Earth, excluding the trees indicated for removal.

  • Use Horizon shading: On

Aurora

  • Irradiance Model: Perez

  • Inverter Clipping: On

  • Weather Dataset: PSM3, NREL-PSM, TMY3 or TMY2

System Losses (See Total Percentage by state in System Loss Chart, below is just a suggestion)

Parameter

Value

Nameplate rating

1.00%

Mismatch

1.50%

Connections

0.50%

Light-Induced Degradation

1.50%

Wiring

2.00%

Soiling

2.00%

Availability

1.00%

Shading

Varies by site

Age

0.00%

Snow

4.00%

Other

0.0%

Daylight's Aurora Design Requirements and Standards

1. Customer Usage & System Sizing

Start every design with customer annual usage (kWh). Input the monthly consumption values from the ComEd, Eversource, or National Grid utility bill into the Energy Details section in Aurora.

Aurora's system will estimate any months that are missing

2. Roof Selection Priority (Panel Placement Order)

Panels should be placed in the following order to maximize production:

  1. South-facing roof or most south-facing plane

  2. South-West and South-East

  3. West and East

  4. North-East and North-West (last resort)

No true North-facing roofs should be used unless absolutely necessary to achieve the minimum system size (5.98kW) or production goals.

Shading from nearby obstructions, such as trees or buildings, should also be considered in panel placement. Favor roofs with higher TSRF when deciding between azimuths.

Prohibited Roof Types: Flat, Rubber, Slate, Terracotta

3. Azimuth, Stringing & MPPT Standards

  • Avoid mixing azimuths/roof planes within a single string. Assign one MPPT per azimuth whenever possible.

  • Do not mix North- and South-facing arrays within the same MPPT.

4. MPPT Utilization

  • Utilize all available MPPTs when array size allows: 2 MPPTs per 12kW Solark, 3 MPPTs per 15kW Solark.

  • Balance the number of panels per MPPT as evenly as possible.

  • Do not overload one MPPT while leaving others unused.

5. Minimum String & Array Requirements

  • Minimum of 5 panels per string per azimuth.

  • If a roof plane has fewer than 5 panels:

  • Add panels where feasible, or

  • Redesign stringing.

6. Production Factor, Solar Access Overall & TSRF

Design and QA/QC threshold:

  • Production factor must be greater than 0.80.

  • Solar access indicates the percentage of sunlight hitting the roof, while TSRF factors in shade, tilt, and orientation.

  • Solar production factors (or capacity factors) are calculated by dividing the actual annual energy production (kWh) divided by system size (kW)*1000

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