Preliminary system design & analysis

This analysis evaluates whether a geothermal heat-pump-assisted hydronic pavement system can prevent ice formation on critical runway zones at Calgary International Airport (YYC). The approach follows the same design logic used at Oslo–Gardermoen Airport, where hydronic heated pavements are successfully supplied by an ATES geothermal system.

For YYC, Calgary-specific geological, thermal, and climatic data from the Paskapoo Formation are applied to compute required heat flux, pipe spacing, power demand, and heat pump performance.

How the geothermal anti-icing system works

Our preliminary system design uses a ground-source heat pump feeding hydronic pipes embedded beneath the runway surface. The goal is to supply enough heat to prevent ice from forming on the most critical zones at YYC, rather than heating the entire airfield.
We design for a representative area of 1,000 m × 20 m (20,000 m²) including touchdown zones, thresholds, and key taxiway intersections. Warm fluid from the heat pump circulates through pipes in the pavement, conducts upward through the asphalt, and keeps the surface a few degrees above 0 °C during snow or freezing rain.

 

Key concepts:

  • Hydronic Pipes: Carry heated fluid beneath the pavement in closely spaced loops.

  • Heat Pump: Upgrades low-temperature geothermal heat to useful pavement temperatures.

  • Geothermal Source (Paskapoo Formation): Provides a steady, low-enthalpy heat supply for the heat pump.

Key Design Parameters That Shape System Performance 

The system is sized using standard airport hydronic pavement design values from FAA and international case studies. These parameters define how much heat we must deliver to the surface and how efficiently it can move from the pipes to the runway. Each value is chosen to match typical airport practice and Calgary’s conditions.

  • Surface Heat Flux (q = 250 W/m²): Mid-range of the 200–430 W/m² used at airports for ice prevention, not full snow melting.

  • Pipe Burial Depth (t = 0.05 m): 5 cm below the surface, shallow enough for quick thermal response but deep enough for pavement strength.

  • Asphalt Conductivity (k ≈ 1 W/m·K): Representative of typical runway asphalt mixes, used to estimate heat flow through the slab.

  • Pipe Diameter (D = 0.02 m): 20 mm hydronic pipe, common in heated pavement systems.

  • Thermal Resistance (R ≈ 1.59 K/W): Derived from

  • R = t / (k * pi * D); this tells us how hard it is for heat to travel from the pipe to the surface.

From Heat to Pavement: How Our Calculations Shape the Design

Understanding how heat moves from the hydronic pipes to the runway surface is essential for keeping YYC’s most critical areas ice-free. Using standard airport design values, we calculate how much heat each meter of pipe delivers and how closely the pipes must be spaced to maintain safe surface temperatures.

 

The map highlights YYC’s critical anti-icing zones in blue areas where aircraft touch down, lift off, or perform major directional changes. Because these locations see the highest braking and acceleration forces, they are most vulnerable to ice bonding and therefore require the most reliable, uniform heating.

The heat-transfer calculations below determine whether our system can keep these priority areas operational and safe.

Key calculations include:

  • Temperature Difference (ΔT = 28 K):

    With the heat pump supplying fluid at 30 °C and the runway surface maintained at 2 °C,

    ΔT = 30 - 2 = 28K

    This temperature difference drives heat upward through the pavement.

  • Heat Output per Meter (Q ≈ 17.6 W/m):

    Using the surface conductance

    U is approximately equal to 0.63 W/K·m,

    The pipe delivers

    Q = U * ΔT = 17.6 W/m

  • Pipe Spacing (s ≈ 0.07 m or 7 cm):

    To achieve the required surface heat flux of  250 W/m², spacing must satisfy:

    s = Q/q = 17.6/250 = 0.07 m.

    A spacing of ~7 cm is much tighter than the 10–30 cm typical at airports, indicating that geothermal heat alone is not sufficient.

    This reinforces the need for heat pumps to raise supply temperatures and enable practical layouts.

  • Total Power for a Critical Zone (≈ 5 MW):

    For a 20,000 m² critical area (such as the zones highlighted in blue/red),

    P = q * A = 250 * 20,000 = 5 MW.

    This power ensures reliable anti-icing coverage where it is most operationally important.

 

Why Heat Pumps Are Critical For YYC'S Anti-Icing System

Groundwater in the Paskapoo Formation is only 4–11 °C, which is too cold to meet the runway’s heat-flux requirement by itself. A ground-source heat pump is therefore essential: it concentrates this low-temperature heat to the 25–35 °C supply temperatures needed for efficient hydronic anti-icing.

 

• Boosting Temperature: With a COP of about 3.5, the heat pump lifts geothermal water to ~30 °C, creating the ΔT needed for effective surface heating.

• Reducing Geothermal Load: Delivering 5 MW of heat to the pavement only requires about 1.4 MW from the ground and roughly 0.4 MW of electrical input, cutting the geothermal demand by ~70% compared to direct-use.

• Achieving Practical Pipe Spacing: Higher fluid temperatures allow pipe spacing to be relaxed toward the 10–25 cm range used at Oslo and other airports, making the system buildable in practice.