PV Panels

This dialog allows you to describe a photovoltaic system supplying electrical power to the building. Specify the existence of such a system by adding one or more entries to the list of PV panels.

There are two options; Freestanding Panels (see Section X ModelIT User Guide) and Parametric Panels.

The user-defined type of the panel.

The area of the panel (m²).

Panel azimuth angle in degrees clockwise from north.

Panel tilt angle in degrees from horizontal.

If adjacent buildings or any other object shades the PV array, the average shading effect can be modelled by reducing the shading factor from the default value of 1.000 (1.0 not shaded, 0.0 fully shaded).

Add (or edit) new PV Types to the list and define the performance parameters.

 

Enter a description for the PV Type.

Define which PV Type is the default. Selecting a type included in the table will populate the data grid on the right with the corresponding data relative to that type.

This is linked to the ‘Defined PV Panels’ UI.  If a particular panel is selected from the ‘Type’ drop-down, it is defined as ‘In Use’

Choose a PV array type from the 6 options

·       Amorphous silicon

·       Monocrystalline silicon

·       Other thin films

·       Polycrystalline silicon

·       Thin Film Cadmium-Telluride

·       Thin Film Copper-Indium-Gallium-Diselenide

If you do not have specific data on the performance of the PV array you can tick this box to apply suitable defaults based on the PV array type.

PV array manufacturers then provide standard defaults, as standard.

The nominal efficiency is the fraction of solar radiant power that is converted to useful electrical power at a standard temperature and solar irradiance.

The cell temperature under standard test conditions – ambient air temperature 20°C and irradiance either 800 or 1000 W/m².

There is a degree of standardisation in the presentation of PV performance data. For example, there are Standard Test Conditions (STCs) for current, voltage, output power and temperature coefficient, and Standard Operating Conditions (SOCs) for NOCT. However, two standards are in use for SOCs, based on irradiances of 800 and 1000 W/m² respectively, so one should always check the stated conditions.

This parameter describes the rate at which the panel’s conversion efficiency falls off with increasing cell temperature.

η = η₀ [1 – β (T_c – T_a )]

where

η is the conversion efficiency at cell temperature T_c and outside temperature T_a

Field measurements of a representative sample of PV modules may show that the PV module powers are different than the nameplate rating or that they experienced light-induced degradation upon exposure (even crystalline silicon PV modules typically lose 2% of their initial power before power stabilizes after the first few hours of exposure to sunlight). The degradation factor accounts for this drop in performance.

This is the combined efficiency of conversion of DC electrical power from the panel to delivered AC electrical power.

The Meter recording the power output.

Select the associated Electricity Meter from the drop down. Define Meters within ‘Energy Sources and Meters’.