Ground-source heat exchangers are systems that transfer heat between the ground and a building. They use a series of pipes buried underground, filled with a heat transfer fluid, to absorb or release heat. In winter, the system extracts heat from the ground to warm the building, while in summer, it can remove heat from the building and transfer it back into the ground. These systems are part of a broader category known as geothermal energy systems, which utilize the Earth's stable temperature for heating and cooling. Ground-source heat exchangers are energy-efficient and environmentally friendly, making them a popular choice for sustainable building designs.