MONO CRYSTAL CELLS ARE MORE EFFICIENT THAN POLY CRYSTAL CELLS AND WILL GIVE BETTER PERFORMANCE IN ALL CONDITIONS INCLUDING CLOUDY DAYS WITH LOW LIGHT CONDITIONS. MONO CELLS ARE DARK IN COLOR, POLY CELLS ARE LIGHTER BLUE AND SHOW MULTIPLE CRYSTAL FORMATIONS ON THEIR SURFACE. The lifespan of a monocrystalline cell is a minimum of twenty-five years and can be more than fifty, making them a worthwhile investment for long term use. Monocrystalline vs Polycrystalline Photovoltaic Cells You may have heard the terms monocrystalline and polycrystalline used to describe photovoltaic cells, but what does that mean and how does it affect a cell’s performance? The main ingredient in most photovoltaic cells is silicon – the same element that makes computer chips possible. Silicon is the second most abundant element in the Earth’s crust, but unfortunately it is normally found in the form of silica (the chemical symbol for silica is SiO2) – you might know it as sand. Various methods exist to extract the pure silicon, but the most common is carbothermic reduction, where the silica is heated to 1700°C in the presence of carbon. As the silicon cools it forms crystals. The speed at which the silicon cools is one of the critical factors that determine the crystal size: the slower the silicon cools, the larger the crystals. With care the silicon can be extracted as one large crystal. As you might imagine, that’s more difficult, which means it’s more expensive. The difference between monocrystalline vs polycrystalline solar cells is simply that one is produced from a single crystal of silicon and the other is produced from a piece of silicon consisting of many crystals. So what is the impact on cell performance? Since polycrystalline cells contain many crystals, they have a less perfect surface than monocrystalline cells. This means that they absorb less solar energy and produce less electricity per square metre. On the plus side, the process of creating the silicon for a polycrystalline cell is much simpler, so these cells are generally cheaper per square metre. On balance, the cost of monocrystalline vs polycrystalline based panels per Watt of power output works out about the same, but the polycrystalline panels will be larger than equivalent monocrystalline panels. This is a problem if you have a very limited area available for the installation, in which case you will want to maximise the power output per square metre so you might as well buy monocrystal. Monocrystalline and polycrystalline also look different. Monocrystalline cells will usually have a perfectly uniform appearance, but polycrystalline cells will appear “grainy” – think of how a granite worktop looks and you’ll get the idea.