The phenomenological relation between current and voltage is described by the implicit function. In the case of HIL (hardware in the loop) simulation it could be more convenient to use a neuroemulator instead of solving in real time the phenomenological model of a solar panel (e.g. using Newton's method). This submission contains both approaches. The very basic MPPT (maximum power point tracking) algorithm is also included. There is nothing insightful about this model -- it is supposed to serve educational purposes. Developed back in 2003.