This Addendum extends the 5T-ISC-AWG Defensive Publication (2026) with a rigorous long-term thermal balance analysis of the bedrock-tunnel condenser, addressing a question that the parent publication acknowledged as a known limitation but did not quantify in detail: how the plant maintains passive operation over decadal timescales when the bedrock condenser is continuously absorbing latent heat of condensation at megawatt-class rates. The analysis confirms that the published Nordic and Mediterranean yields (0.93 and 1.16 ML/day respectively) are fully sustainable in passive 24/7 operation, and identifies the physical mechanisms through which long-term thermal balance is achieved: dew-point-pinning of the warm inlet wall by the wet-bulb temperature of the incoming air, internal vapour-phase heat redistribution by the adhesive water film along the tunnel invert, conductive dissipation through the bedrock mass to the natural ground surface above the tunnel, and night-time radiative re-cooling through selective-emissivity coating at the chimney head. For the tropical configuration, the same analysis shows that the originally published yield of 1.98 ML/day is achievable as a transient design peak rather than as a sustained 24/7 operating point under strictly passive conditions, because the higher latent heat input at tropical coastal sites overwhelms the passive dissipation budget of a five-tunnel plant. This Addendum therefore introduces a scaled tropical embodiment — the 15T-2C-LV configuration: fifteen parallel tunnels, two solar chimneys, low-velocity continuous operation, with dedicated exhaust-air bedrock cooling galleries — that achieves a sustained passive yield of approximately 0.95 ML/day at generic tropical coastal sites with surface mean temperature ≤ 22 °C above the tunnel array, rising to approximately 1.69 ML/day at premium Goldilocks-tropical sites with surface mean temperature ≤ 19 °C. The configuration uses no pumps, no fans, and no active cooling; the exhaust-air galleries are driven by the same chimney suction that drives the production tunnels. The Addendum adds three new defensive claims (C8 through C10) covering the multi-chimney configuration, the exhaust-air bedrock cooling galleries, and the scaled tropical embodiment, and revises the published tropical yield figure for accuracy. The Nordic and Mediterranean configurations and yields of the parent publication are unchanged. Consistent with the parent publication, this Addendum is positioned as a technically honest extension. It does not retract the original tropical figure as a design peak (which it remains, under transient conditions and during the first months of operation from a cold-start), but it identifies the conditions under which that figure is sustainable and offers a scaled embodiment under which a sustained tropical megalitre-class yield is reached strictly passively. All thermal and psychrometric values in this Addendum are computed with the Magnus approximation for saturation vapour pressure, NIST-consistent latent heat of vaporisation, and the ε-NTU method with effectiveness ε = 0.90 — the same numerical convention used throughout the ALLFROMAIR® TERRA² Technical Addendum 6 reference verification.
Lius et al. (Tue,) studied this question.