Ground source heating and cooling or “ground source heat pump” is an energy efficient way to remove heat from the ground in the winter and cooler temperatures from the ground in the summer, piped into conventional heating and cooling systems to boost efficiency. Instead of the system doing all the work, water is piped into the ground to aid the system with warmer or cooler water, depending on climate and seasons. The temperature at 20 feet in the ground is equal to the average annual temperature of that particular climate on the surface. This temperature is almost a constant 50 to 60 degrees fahrenheit, and very stable, making it an ideal way to extract heat from the ground, or use the ground as a heat sink to remove heat from a piping system.
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To set up a ground source heat pump, it is quite costly in the initial investment, but can have some amazing returns, three to ten years, due to the high efficiency operation of the system. Normally, piping is buried in the ground in loops. These loops are in direct contact with the surrounding earth making a heat exchange possible. The number of loops and pipe sizing, depend on the amount of BTU’s required to heat or cool the home. Simplified, The loops are connected to the system through a heat exchanger located in the home and pumped by means of a circulator. The heat exchanger may be water to water heat exchange or water to air. Water to water would be used in conjunction with a boiler or water heating system. Water to air heat exchangers (or coils) are used in forced air systems with duct work. There are many variations of the system that can be installed and connected to existing or new heating and cooling systems. The most common systems are direct exchange, closed loop systems, and open loop systems.
A direct exchange system is the oldest and simplest of all ground source heat pumps. This system is used in a conventional heat pump system where refrigerant (not water) is piped directly into the ground in copper coils to extract heat or release heat into the ground, making the system much more efficient.
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A closed loop system has two loops, a primary and secondary loop. The primary loop would be the refrigerant loop inside the unit where it delivers heat to the secondary loop through a plate to plate heat exchanger, keeping the loop contents separate. The secondary loop contains the water that is circulated back to the ground where the heat from the water is removed before returning to the unit.
An open loop system uses water from a well or natural body of water, such as a lake, that is pumped into the heat exchanger to transfer inside the unit. This type of system uses protection such as filters and could cause build up of minerals inside the heat exchanger, requiring constant cleaning. A closed loop system is normally preferred over this type of system for these reasons.
These types of systems and systems such as wind and solar, are being installed on a much more frequent basis as a result of today’s rising fuel costs. A Lot of new home manufacturers are incorporating them with high efficiency propane or natural gas systems and conventional heat pump systems, making it more affordable to heat and cool homes.
