Batteries and other energy storage devices store energy so that it can be used when needed. In a stand-alone power system, the energy stored in batteries can be used when energy demand exceeds the output from renewable energy sources like solar (e.g. on a cloudy day) and wind (e.g. on a still day).
Inverters and other energy conversion devices turn energy from one form to another. An inverter in a grid connected renewable energy system converts direct current (DC) electricity from solar panels or a wind turbine into alternating current (AC) mains power.
Any renewable energy system also includes switches, circuit breakers and fuses to ensure it is electrically safe and allow major equipment to be isolated for maintenance.
Solar Batteries:
Lead-acid batteries are often used in renewable energy systems. However, lithium batteries, though more expensive than lead-acid, are becoming more affordable and can have a much longer life. Nickel iron batteries are harder to find and less efficient than lead-acid or lithium ion but have very long lives. Flow batteries (zinc bromine and vanadium redox) and flywheel batteries can be used in renewable energy systems but are complex and expensive.
Solar Inverters:
Inverters are commonly a part of both grid connected and stand-alone renewable energy systems. Inverters convert DC power from batteries or solar modules into usable AC power, normally 240V AC (single phase) or 415V AC (three-phase). Inverters are complex electronic devices and must be installed in relatively clean areas.
Inverters can become very warm when operating at large power outputs and need suitable ventilation and cooling airflow. Insects often like to nest in the heat dissipation vents, so site your inverter carefully and check it often.
Inverters should be installed out of direct sunlight as direct exposure can cause them to overheat. They should be easily accessible in case they need to be electrically isolated in an emergency.