Fan convectors use fans to push air across a heat exchanger within the unit, which warms or cools the air, depending on whether the system is in heating or cooling mode and circulates it round the room.
They give the user a lot of control over heating and cooling and can enable the user to specify the constant temperature
However, they require relatively high/low flow temperatures in order to work effectively making them unsuitable for many renewable technologies. Some manufacturers make heat pumps specifically for fan convector systems. RDC will recommend the most suitable products for your project.