Geothermal systems stand out as being one of the most efficient heating and cooling systems you can install in your home. Capable of harnessing the Earth's natural heat energy, a geothermal system is also an environmentally friendly way of keeping your home comfortable.
As you research your geothermal heating and cooling options, the biggest choice you'll likely face is one between an open loop and closed loop geothermal system. Both types have their own unique set of benefits and drawbacks to consider, so it's important to carefully vet each option before choosing your new geothermal system.
Open loop geothermal heating and cooling systems work by pulling groundwater directly from a conventional well or a deep lake. The groundwater circulates through the geothermal heat pump, where it absorbs heat removed from the indoor air during the summer or releases heat into the indoor space during the winter.
Afterwards, the water used in the geothermal process is discharged directly into a nearby body of water, such as a pond, lake or stream. Some open loop systems utilize a return well, allowing discharged water to replenish the ground aquifer instead of being dumped into an existing water source.
Open loop geothermal systems used to be common decades ago until advances in geothermal technology made closed loop systems more desirable among homeowners.
Pros and Cons
Open loop systems are usually less expensive to install than their closed loop counterparts, owing to the relative simplicity of an open loop setup. Most open loop systems only require a shallow trench to bury the required plumbing to the water source. An open loop system also uses less plumbing compared to a closed loop system.
Water quality issues are one of the biggest drawbacks of operating an open loop system. It's important to test your water source for mineral deposits as well as hardness and acidity prior to installation, as these issues can easily impact your open loop geothermal system's reliability and efficiency.
Open loop systems also require a steady, reliable source of water in order to maintain adequate water flow rates for the geothermal unit. As a result, an open loop system might not be ideal for areas with water availability issues.
Unlike an open loop system, a closed loop system features a continuous, self-contained loop between the ground and the heat pump. Instead of using water, closed loop systems rely on an antifreeze solution to not only facilitate the heat transfer process, but also to prevent the pipes from freezing. While most closed loop systems used methanol in the past, most modern systems use ethanol, ethylene glycol, propylene glycol or calcium chloride.
One particular type of closed loop geothermal system, known as a direct exchange system, feeds refrigerant through copper tubing that's buried in the same fashion as normal closed loop tubing. The refrigerant exchanges heat directly with the soil underground, hence the name.
Pros and Cons
One advantage of a closed loop system is that it can be installed horizontally through the use of trenches or vertically through drilling. A vertical installation is ideal for areas where space is at a premium. Like open loop systems, a closed loop system can also take advantage of a nearby lake or pond. Another advantage is that since closed loop systems don't rely on any nearby water sources, you won't have to worry about how the water quality will impact your geothermal heat pump.
On the other hand, closed loop systems are more expensive to install than their open loop counterparts, especially when it comes to vertical installations that require significant amounts of drilling. Certain types of antifreeze used in closed loop systems, including ethylene glycol and methanol, can potentially contaminate and poison groundwater if leaks occur.
The experts at Modern Heating & Cooling will gladly take your questions if you're interested in having a geothermal heating and cooling system installed for your home.