Ground Source Heat Pump

Also known as earth energy systems, where heat is extracted from the earth through certain liquids, the heat pump then raises the temperature from that liquid. That heat is then used for the indoor setting. This source of heating comes directly from the earth or ground water, and helps develop heat for homes. This type of system can be expensive to install, but requires little maintenance. This system is beneficial because it is energy saving and in places such as Canada where temperatures in winter can be very cold, like -30°C, the groundwater temperatures are typically -2°C to 4°C. Earth energy systems (EES) have a Coefficient of Performance (COP) of 2.5 to 3.8 which means that their input is 2.5 to 3.8 times greater than their input, a measure of their efficiency. An EES installation in southern Canada, such as Ontario, will have an HSPF of 10.7 to 12.8, which is significantly higher than 3.4 which is for electrical-resistance heating which is typically used.  An HSPF is the heating seasonal performance factor, which is another measure of efficiency, specifically with respect to heating and so the higher the number, the better it performs.

Heat Pump
(1) Circulation
(2) Heat Extracted From Earth
(3) Heat Exchange and Use
(4) Recirculation
Coefficient of Performance (COP)=
  energy output  
energy input

This image shows an air source heat pump.

Image obtained from Google Images, click on image for reference. 

Air Source Heat Pump

Air source heat pumps work by working with air from outside. During the warmer months, heat is rejected, while during the cooler months the heat is taken from outside. There are two types of air source heat pumps: air to air heat pump and the air to water heat pump. The air to air heat pump takes heat from the air and brings that into or outside of your home varying on the season. The air to water pump in the cooler temperatures takes heat from the air outside and carries that into the water that is within the hydronic distribution system. In warmer temperatures, the opposite occurs where the hydronic distribution system takes the heat away from the water and expels it outside.