Flat Plate Collectors (FPC) used the greenhouse effect, the Flat Plate Collector converts solar energy from the sun into heat energy, which then is transferred to the water system in residential and commercial houses.
An off grid solar system comes with solar panel, solar inverter and solar battery as well. This solar system is also known as stand-alone solar system.
An air source heat pump, sometimes referred to as an air-to-water source heat pump, transfers heat from the outside air to water, which heats your rooms via radiators or underfloor heating.