Solar Electricity Overview

The sun is the source of just about all power and energy sources on earth. Necessity, as well as technological advances in the last few decades have enabled us to generate electricity from photovoltaic (PV) panels. It is now very feasible to generate and store all the electricity you need from the sun, with a properly designed system. The following are the basic components of a solar electricity system:

Panels

PV panels are either polychrystaline, monochrystalline, or thin-film, all with their own characteristics, efficiencies and applications. The most commonly used in domestic systems in South Africa is polychrystalline, although recently monocrystalline have been getting traction, and have proven worth the small extra cost for their improved efficiency.  com

Panels come in a variety of sizes, correlated to power output, and have a life expectancy of 20-25 years. A group of panels forms an 'array', the total wattage of which gives you your solar electricity generation capacity, measured in watts (W), or kilowatts (kW). The maximum potential power of the array is referred to as the PVmax or kWp, and is a handy figure to know, as this relates to the most power that the system will every produce at one time.

Batteries

Battery storage is only required if you have no grid connection, or in a ‘Hybrid’ or grid-interactive system, if you want a back-up for when the grid fails. For a typical stand-alone system, you would want to have enough battery storage capacity to see you through 2-3 days of inclement weather (with limited charging capacity from your panels). The more common battery types used in solar systems are deep-cycle lead-acid, gel, or lithium Iron Phosphate. Their life expectancy is dependent on type as this relates to how many ‘cycles’ the battery is good for, but also how well they are looked after - inversely proportional to how much and how often they are discharged. Lithium batteries are far superior in charging efficiency, recovery after discharge (and therefore lifespan) and size, and although more expensive initially, are going to give one more reliability than the lead-acids and a much reduced Lifetime cost, in the long run.

Inverter and Charge Controller

The inverter is the backbone of a system, and takes the direct current (DC) from your batteries, and turns it into alternating current (AC, usually at 220-230 volts) to supply to your house (because that's what most of our appliances require). Inverter size is determined by your Peak power requirements (all appliances in the house on at the same time, if this were to every happen…!). The Charge Controller is also an essential piece of equipment, regulating the current that is supplied to your batteries, and in the case of a Maximum Power Point Tracking (MPPT) device, optimizing the way in which the energy arriving at the panels is utilized.