Photovoltaics – Reducing cable cross-section by considering load

Client:
Photovoltaics Expert

Problem: 
Our client, a renowned photovoltaics expert was presented with a complex task. A photovoltaic system builder had the idea of considering the load profile in the cable design. The idea made sense as photovoltaic system power rises and falls to zero during the day-night cycle. Therefore, cables are not permanently subjected to maximum stress levels and the surrounding ground also cools down during the night. The norm requires m = 1. However, as in almost every standard, there is also the possibility of deviating from the norm if the reasons are well founded.

Solution: 
Based on our experience gathered from similar projects in the areas of wind power and hybrid vehicle technology we were quickly able to recommend the customer a Comsol Multiphysics multidimensional calculation.

This considers both the expected load profile of the photovoltaic system as well as all geometrical and material-specific boundary conditions. To stay on “the safe side” all estimates were conservative.

The simulation demonstrated that in the first days the temperature of the cable as well as the surrounding ground increases continuously. However, after a few days, a stationary profile appears showing only minor day-night fluctuations.

The maximum temperature is clearly below the maximum temperature which was to be expected constantly as per standard calculations.

As a result of this project, our client could communicate with their customer in a calm manner and accept a cross-section decision that was higher than our calculations but still under the amount laid out by photovoltaic standards.