SPAC 1.1 UI

SPAC allows homeowners, engineers, and investors to evaluate the energy yield of a potential solar installation based on real-world structural and geographical parameters. The system supports two primary installation site options:

1. Rooftop Installations: Residential or commercial roofs with full or partial southern exposure.
2. Ground-Mounted Systems: Open land (yards, fields, or unshaded lots) suitable for mini solar power plants with fixed or tracking mounts.

To generate an accurate solar generation forecast, SPAC requires three core parameters:

• Geographical Location / Latitude: Selected from a database of nearby reference cities with historical solar radiation statistics.
• Roof Pitch / Panel Tilt Angle: The inclination angle of the surface measured relative to the horizontal plane ($0^\circ$ to $90^\circ$).
• Azimuth Alignment (Orientation): The deviation angle from due South.

Roof Orientation vs. Ground-Mounted Flexibility

In the Northern Hemisphere, PV panels achieve maximum annual output when facing South. Roofs oriented towards the North, Northwest, or Northeast are generally unsuitable for solar investments due to severe shading losses.

When mounting on an existing roof, pitch and orientation are fixed by the building's architecture. Conversely, ground-mounted systems offer complete freedom to optimize panel orientation and mounting geometry:

• Fixed South-Facing Mounts: Optimized for annual average peak generation.
• Single-Axis Seasonal Tracking: Monthly adjustable tilt angles to capture seasonal elevation changes.
• Dual-Axis Active Tracking: Continuous daily tracking of both solar azimuth and elevation angles.

• v0.9 Beta (October 2022): Initial release calculating theoretical geometric solar angles and extraterrestrial irradiation.
• v1.0 Beta (December 2022): Added electricity generation yield models utilizing the classic Liu-Jordan diffuse radiation model and atmospheric turbidity coefficients.
• v1.1 Beta (January 2023): Integrated a stochastic algorithm for dynamic atmospheric turbidity estimation based on local statistical climate data, developed by mechanical engineer Miroslav Mitic.

Functional layout and input modules of the SPAC user interface

The SPAC interface is structured into six logical input and configuration sections:

1. Location & Albedo Selection: Select the nearest city from the database to load microclimate data. You can also specify ground reflectance parameters (Albedo) to model ground-reflected radiation accurately.
2. Tracking Options: Select between fixed-tilt mounting, single-axis seasonal adjustment, or full dual-axis tracking configurations.
3. Tilt & Azimuth Entry: Input roof pitch and azimuth deviation. Azimuth is measured from due South: enter negative values ($-1^\circ$ to $-90^\circ$) for Southeast orientations, and positive values ($+1^\circ$ to $+90^\circ$) for Southwest orientations.
4. PV Panel Selection & Array Sizing:

   Choose a commercial solar panel module from the database and configure the array geometry:

   • Roof Fill Mode: Automatically calculates maximum panel capacity based on overall roof dimensions ($L \times W$).
   • Custom Grid Mode ($M \times N$): Define a custom matrix of panels tailored to specific physical or financial constraints.
5. Calculation Method Engine: Toggle between the classic Liu-Jordan model or the enhanced Stochastic Modified Liu-Jordan algorithm prior to execution.
6. Results & Yield Forecast: Computes both theoretical solar availability ($kWh/m^2$) and actual expected electrical output ($kWh$) on an annual and monthly basis.

1. City and nearest meteorological site selection

2. Roof tilt angle and South azimuth deviation parameters

3. Photovoltaic panel database and power ratings

4. Array geometry selection: Full roof area vs. custom grid layout

The SPAC tool provides an intuitive yet mathematically rigorous framework for simulating PV plant yields without requiring complex CAD or GIS software. Ongoing developments focus on expanding the weather database to cover smaller municipalities and integrating real-time satellite irradiance data for even higher precision.