Solar Electric Power System



"Its beautiful, just like a stained glass window"
Sweet Sue on the benefits of owning a polycrystalline photovoltaic module.
The question of designing a solar electric power system raises a number of interesting problems. For a remote system, size of panels and battery storage capacity need to be determined. For grid-connected installations the financial benefits are of greatest interest.

For grid-connected systems, we discuss a mathematical model and simulation program.

In a remote installation, the electronics for charging the batteries must be able to extract the maximum power at minimum loss from the solar modules, as well as performing a number of functions such as battery protection from over and under charging, protection of the cells from reverse voltage, and powering a number of user devices from low voltage DC to the standard grid mains power, in our case, 240V AC.

Before tackling the electronics, which will come later, we take a look at how to obtain a good choice of the capacities of the solar cells and battery. This is helped by studying a mathematical model of the system of solar modules and batteries.
  1. Solar Module Illumination Model. This model predicts the maximum power that could be obtained from a solar module during the course of a day at any time of year and any latitude. The model gives an appreciation of the reduction in power output over the specified power and how this will vary with latitude and time of year.
  2. Solar Module Model. This model predicts the actual power that would be stored into a battery. This differs from the maximum power calculated in the Illumination Model because the fixed battery voltage would prevent the solar module from operating at its maximum power transfer point. The model gives an appreciation of the loss due to the fixed battery voltage.
  3. Electronics. To be done. The aim is to develop a smart regulator that could improve the overall efficiency of the system.


First created 17 January 2007

Last Modified 26 June 2007
Ken Sarkies 2007