Key Reasons for Poor Performance

Reason 1: Use of Shallow Horizontal Loops

The Underlying Issue and Seasonal Woes

Shallow horizontal loops are often favored for their economical installation costs. However, this upfront saving masks some inherent drawbacks. One of the most significant is the sensitivity of these shallow loops to fluctuating ground temperatures. Unlike deeper underground layers, the temperature at shallow depths is much more susceptible to seasonal changes.

During cold winters, this becomes particularly problematic. When the ground freezes, the shallow loops may not be able to extract sufficient heat to maintain a comfortable indoor environment. As a result, the system has to work overtime, leveraging backup heating methods or increasing the compressor’s duty cycle, which leads to high operational costs and reduced lifespan of the unit.

Impact on Efficiency Metrics

This increase in operational complexity negatively impacts the system’s Coefficient of Performance (COP). Where a well-designed geothermal system might typically operate at a COP of 4-5, shallow loop systems may see this figure dip to as low as 2-3 in harsh conditions, essentially halving its energy efficiency.

Soil Conductivity: The Unseen Variable

Shallow horizontal loops are also more susceptible to the variability in soil thermal conductivity. The soil type can significantly influence how efficiently heat is transferred between the loop and the earth, a variable often neglected during the design phase for shallow installations.

Solutions

• Depth Augmentation: If horizontal loops are non-negotiable due to space or other constraints, increasing their depth may offer some benefits, although this is often a compromise rather than an ideal solution.
• Enhanced Thermal Grouts: Using thermal grouts with higher thermal conductivity can help in optimizing the heat exchange efficiency, though this doesn’t fully mitigate the shortcomings of shallow loops.

Why Vertical Loops Offer Better Performance

Depth-Enabled Stability

Vertical loops plunge much deeper into the Earth, tapping into a more stable thermal environment that isn’t subject to the whims of seasonal changes. This stability ensures a more consistent heat exchange process, boosting the system’s COP.

Reduced Land Requirement

Vertical installations also require less land area than their horizontal counterparts. This allows for more flexibility in system design and can be particularly advantageous in residential settings where land is often at a premium.

Lower Lifecycle Costs

Although the upfront costs of vertical loops are higher, the total cost of ownership often ends up being lower due to increased efficiency and lower maintenance needs. There’s less wear and tear on the system components, and there’s rarely a need for supplemental heating, even in colder climates.

Adaptability to Soil Conditions

Vertical loops are less affected by soil thermal conductivity, making them more adaptable to different geological conditions. This flexibility often makes vertical loops a universally reliable choice, irrespective of local soil characteristics