SPAC 1.27 UI

By integrating site-specific solar irradiance statistics with real-time regional electricity tariffs, SPAC enables users to model both energy production ($kWh$) and estimated financial revenue. The application supports two primary installation site options:

1. Rooftop Installations: Residential or commercial pitched roofs with full or partial southern exposure.
2. Ground-Mounted Systems: Open land, unshaded yards, or agricultural plots suitable for mini solar power plants.

To run a simulation, SPAC requires three fundamental location parameters:

• Geographical Location / Latitude: Selected from a database of nearby reference cities with statistical meteorological data.
• Roof Pitch / Panel Tilt Angle: The inclination angle relative to the horizontal plane.
• Azimuth Alignment (Orientation): The surface deviation angle measured relative to due South.

Roof Orientation Constraints vs. Ground-Mounted Flexibility

In the Northern Hemisphere, maximum cumulative solar gain occurs when panels face due South. Roofs oriented towards North, Northwest, or Northeast suffer severe shading and cosine losses, making PV investments unviable. Deviations to the East or West must be accurately measured from the South axis.

While building architecture dictates fixed roof geometry, ground-mounted installations allow full structural optimization:

• Fixed South-Facing Mounts: Simplest structure optimized for annual yield.
• Single-Axis Seasonal Tracking: Monthly adjustable tilt angle to follow seasonal solar elevation.
• Dual-Axis Active Tracking: Continuous dynamic tracking of both azimuth and elevation angles.

• v0.9 Beta (October 2022): Calculated theoretical geometric solar angles and extraterrestrial irradiance.
• v1.0 Beta (December 2022): Added electricity generation estimation using the classic Liu-Jordan diffuse radiation model.
• v1.1 Beta (January 2023): Integrated a stochastic Linke turbidity algorithm developed by mechanical engineer Miroslav Mitic.
• v1.2 Beta (March 2023): Redesigned UI; added inverter matching, string input voltage verification, wiring cross-section recommendations, and regional tariff financial calculations.
• v1.25 Beta (May 2023): Added collapsible data tables, optimized calculation execution flows, and improved error handling for large datasets.
• v1.27 Beta (June 2023): Updated UI theme and introduced graphical plot plan rendering for mini power plant footprints.

Main interface overview of SPAC v1.2x featuring energy and financial ROI modeling

The updated interface leads the user through a logical step-by-step configuration flow:

Step 1: Required Physical Inputs

1. Location & Coordinates: Select the nearest city to load meteorological statistics or enter custom latitude.
2. System Mount Category: Select fixed-tilt, single-axis, or dual-axis tracking architecture.
3. Roof Pitch & Azimuth Deviation: Input surface slope and orientation (enter negative values for Southeast, positive for Southwest, measured from South).

Nearest meteorological site selection

Roof pitch and South orientation deviation setup

Step 2: Environmental & Mounting Options

Configure ground reflectance (Albedo) parameters (e.g., urban asphalt, grass, or winter snow cover) to accurately model ground-reflected diffuse radiation.

Ground reflection (Albedo) environment selection

Step 3: Array Sizing & Equipment Selection

Choose between filling an existing roof area ($Length \times Width$) or constructing a custom $M \times N$ panel array grid.

Ground-mounted mini power plant configuration interface

Next, select a photovoltaic module from the integrated database to define string voltage, power density, and layout dimensions.

Photovoltaic module selection and power specification

Upon execution, SPAC outputs two core dataset categories: theoretical solar irradiance availability ($kWh/m^2$) and realistic electrical yield estimations ($kWh$), including optimal string voltage and financial returns based on the local tariff.

SPAC v1.2x delivers a balanced toolset for evaluating PV installations by combining stochastic meteorological models with practical electrical and financial constraints. Future updates will focus on incorporating high-resolution satellite insolation maps and expanded local weather databases.