The three main types of solar power systems: On-Grid, Off-Grid and Hybrid

The three main types of solar power systems

1. On-grid - also known as a grid-tie or grid-feed solar system

2. Off-grid - also known as a stand-alone power system (SAPS)

3. Hybrid - grid-connected solar system with battery storage

Main Components Of A Solar System

Solar Panels

Most modern solar panels are made up of many silicon-based photovoltaic cells (PV cells) which generate direct current (DC) electricity from sunlight. Solar panels, also known as solar modules, are generally connected in ‘strings’ to create what is known as a solar array. The amount of solar energy generated depends on several factors, including the orientation and tilt angle of the solar panels, the efficiency of the solar panel, plus any losses due to shading, dirt and even ambient temperature.

Solar panels can generate energy during cloudy and overcast weather, but the amount of energy depends on the 'thickness' and height of the clouds, which determines how much light can pass through. The amount of light energy is known as solar irradiation and usually averaged over the whole day using the term Peak Sun Hours (PSH). The PSH or average daily sunlight hours depends mainly on the location and time of year.

Solar Inverter

Solar panels generate DC electricity, which must be converted to alternating current (AC) electricity for use in our homes and businesses. This is the primary role of the solar inverter. In a ‘string’ inverter system, the solar panels are linked together in series, and the DC electricity is brought to the inverter, which converts the DC power to AC power. In a microinverter system, each panel has its own micro-inverter attached to the rear side of the panel. The panel still produces DC but is converted to AC on the roof and is fed straight to the electrical switchboard.

There are also more advanced string inverter systems which use small power optimisers attached to back of each solar panel. 

Batteries

Batteries used for solar energy storage are available in two main types: lead-acid (AGM & Gel) and lithium-ion. Several other types are available, such as redox flow batteries and sodium-ion, but we will focus on the most common two. Most modern energy storage systems use rechargeable lithium-ion batteries and are available in many shapes and sizes, which can be configured in several ways explained in more detail here.

Battery capacity is generally measured as either Amp hours (Ah) for lead-acid or kilowatt hours (kWh) for lithium-ion. However, not all of the capacity is available for use. Lithium-ion based batteries can typically supply up to 90% of their available capacity per day. In comparison, lead-acid batteries generally only supply 30% to 40% of their total capacity per day to increase battery life. Lead-acid batteries can be discharged fully, but this should only be done in emergency backup situations.