What is groundwater-coupled HVAC, and how can it contribute to a net-zero future?DCL Geothermal energy service illustration groundwater-coupled heating and cooling

During our latest Coffee Break webinar, we spoke with Jay Egg, author and consultant at Egg Geo LLC. These 35-minute presentations are packed with information from the leading experts in HVAC, so contact an SVL sales engineer to get an invitation.

Egg explained the latest technology behind geothermal and aquifer-based heat pumps and what a net-zero future could look like thanks to earth loops. Here’s a partial recap of our conversation:

Why do we need geothermal HVAC?

If we’re serious about reducing greenhouse gas emissions, Egg tells us, we need to recognize that 40% comes from the combustion of fossil fuels for domestic hot water and building heat. We can’t get to full net-zero if we don’t decarbonize our buildings’ operations. We need to adopt more efficient uses of heat pump technology to make it happen.

A groundwater-coupled heating and cooling system takes advantage of the stable temperatures just below ground level. Groundwater is either warmer than the air in winter or cooler than the air in summer, which presents a massive thermal opportunity. This kind of system pumps groundwater out of an aquifer into a heat pump and discharges it back into the aquifer.

What are the advantages of groundwater-coupled heating and cooling?

Groundwater-coupled HVAC eliminates the need for outdoor equipment like condenser farms or cooling towers. This eliminates noise, refrigerant lines, or potential vandalism from precious metal harvesters. Unlike some kinds of heat pumps, earth loop systems work well in all climates (several such systems are operating currently across Canada.)

Are there different kinds of earth loop systems?

There are a few:

  • Closed-Loop Exchange. Two HDPE pipes with a U-bend at the bottom are inserted into the bottom of a borehole between 250-500 feet deep. The hole is backfilled will bentonite grout. It can be installed in any soil. These are common but expensive (especially for systems with huge capacity requirements that might need several holes.)
  • Aquifer-based Geo-Exchange Systems: These are installed in places with aquifers. They are still expensive but have the highest capacity and can have the least cost per ton. They employ a heat exchanger and a submersible pump located at the bottom of a closed-loop aquifer well.

What is the lifespan of the pumps and heat exchanger on a system like this?

According to American Groundwater Association, the life of a submersible pump for constant duty is about 27 years. Egg contends that’s probably a low estimate and says the life of the heat exchanger is approximately 20-30 years as well. Servicing is relatively easy, with the components quickly extracted by a well rig.

Can these systems operate with any heat pump?

They can. Vertical, horizontal, dedicated hot water, etc., the different heat pumps used in these systems vary widely.

Egg also explained how the Dynamic Closed Loop system takes the best of aquifer-based thermal exchange and couples it with a familiar closed-loop system, for greater heat transfer, with less pump energy needed and zero water extraction from the well.