Solar array model¶
Example: PV module calculator
The ability to use Solcore to build a SPICE equivalent circuit allows entire PV systems to be simulated from the bottom up. Each photovoltaic solar cell is described using an equivalent circuit which can then be arranged in strings of series and parallel cells to represent the entire system. An example for a triple junction solar cell, complete with a bypass diode is shown in figure [fig:3J_equiv_curcuit]; this unit is the basic building block for a concentrator PV module.
The diode and resistance values for the equivalent circuit are determined from solar cell testing, while the current source is evaluated by integrating the product of the spectral irradiance (estimated using an appropriate radiative transfer code e.g. SPCTRAL2 or SMARTS) and the quantum efficiency which in turn can be calculated dynamically as a function of temperature by Solcore.
Since the entire module (and subsequently the system) is assembled from individual solar cell components, it is possible (and indeed, necessary) to distribute the component values to accommodate for manufacturing tolerances. This enables a close match between the modelled output power and that measured experimentally and has been used to determine how both aerosols and precipitable water affect the electricity yield from concentrator PV systems. Where system IV data is available, the emergence of electrical faults, (e.g. shunts or shading) can also be accounted for.