Geothermal Heating and Cooling 102

How is ground source heat energy perceived?

Expensive to install, not very reliable, but good for the environment by cutting fossil fuels and reducing CO2 emissions.

Why is the ground a good energy source?

It has a constant temperature year-round, unlike air temperature which changes seasonally.

What does a ground heat exchanger (GHX) do?

Transfers energy to or from the ground using circulating fluid.

What are the four main components of a basic heat pump?

Compressor, condenser, expansion valve, and evaporator.

How does a heat pump heat a building?

Extracts heat from GHX fluid, compresses it, and transfers it to the building air.

How does a heat pump cool a building?

Extracts heat from building air, compresses it, and transfers it to the GHX.

What is a desuperheater in a geothermal system?

An added component that diverts 5-10% of heat pump capacity to heat domestic hot water (DHW).

What is the key difference between designing conventional HVAC vs GSHP?

Conventional systems assume infinite energy and heat sinks; GSHPs must manage finite ground energy.

Why can’t a GHX be selected from a catalog?

It must be custom-designed based on building and site-specific energy loads over the building's life.

How does the ground respond when cooling a building?

The earth around GHX piping warms and slowly dissipates heat to the surrounding earth.

How does the ground respond when heating a building?

The earth around GHX piping cools and slowly draws heat from surrounding soil.

Why don't rules of thumb work for GHX design?

Because energy loads are site- and building-specific; generic rules miss critical variables.

What happens if GHX sizing only uses peak loads?

It risks long-term performance problems like temperature degradation.

How can proper GHX sizing save costs?

Accurate energy modeling can optimize GHX size, saving on drilling and installation costs.

What improves GHX performance and stability?

Balancing heating and cooling energy loads to the ground.

What do soil properties affect in GHX design?

They determine how much and how fast energy is transferred between GHX piping and the earth.

How does thermally enhanced grout help a GHX?

It improves heat transfer, stabilizing GHX temperature and efficiency over time.

What is a design challenge with heating-dominant systems?

Long-term ground temperature drops can lower system efficiency.

How does changing glass specifications impact GHX?

Reduces heating and cooling loads, affecting GHX size and performance.

How does exhaust air energy recovery (ERV) help GSHP systems?

Reduces heating loads and helps balance annual energy loads for better GHX performance.

What factors determine GHX type and configuration?

Site area, geology, contractor capabilities, and project-specific constraints.

Why must contractor capability be considered in GSHP design?

It affects cost, feasibility, and long-term system success.

How do energy models influence return on investment (ROI)?

They predict system costs, energy savings, and utility cost comparisons.

What must happen before final GHX design?

Confirming assumptions via test bores, soil data, and thermal conductivity tests.

Why is commissioning important in GSHP projects?

It ensures proper system flushing, setup, and long-term performance monitoring.

What documentation should be given to building operators?

System design basis, control strategies, and expected GHX operating temperatures.

What happens if GHX temperatures go outside optimal range?

System performance drops; monitoring is essential to detect and address it.

How does a well-designed GSHP system benefit owners?

It reduces energy use, cuts CO2 emissions, ensures reliability, and offers strong ROI.