The Earth’s Energy - Geothermal Heating & Cooling Systems
Posted on: October 2019
Imagine an energy source that is renewed daily, clean and can be found in your own backyard.
Geothermal energy systems use the temperature of the ground to either heat or cool the indoor environment. Making it a global means of heating and cooling as consumers become more environmentally aware. (Derek Whitfield, 2013)
Understanding Geothermal Systems
The shallow ground, at around 2m deep, maintains a temperature between 10°-17°C all year, which is far more constant than the air temperature above the surface. The deeper you go the more constant the temperature becomes. In most areas during winter the ground is warmer than the air above it and in summer the ground is cooler than the air, which means it can be used all year round. Ground and ground water heat pumps take advantage of these temperature differences to heat and cool the indoor environment. This is done by pumping water or refrigerant through a buried loop field of high-density polyethylene (HDPE) plastic tubing and returning it at warmer temperature in winter and cooler temperature in summer.
Horizontal vs Vertical System
The system can either be a horizontal or vertical loop field, depending on the land area available for the system and the depths at which the system would be most feasible.
Horizontal fields require trenches of between 3m to 5m deep where the tubing is laid horizontally either in u-shaped loop or a slinky loop (to save space). They are generally more cost effective than vertical fields but need a much larger surface area to be as effective.
Vertical fields require holes to be drilled into the ground at depths of between 60m to 120m deep. Two tubes are placed in these boreholes and connected at the bottom to form a u-loop with the space between the borehole wall and tubing filled with grout to enhance the thermal properties.