Polar Thermal Breakwater Unit (PTBU): A Passive Dual-Function Concept for Polar Coastal Protection and Seasonal Freshwater Phase Change

The Polar Thermal Breakwater Unit (PTBU) is a conceptual dual-function coastal engineering system proposed for cold and polar environments. The concept combines the mechanical role of interlocking concrete armor units used in breakwaters with a sealed internal freshwater cavity designed to undergo seasonal freezing and thawing. During the cold season, heat is transferred from the enclosed freshwater through the unit walls to the colder external environment, allowing partial or complete freezing. During the warmer season, the resulting ice mass provides latent-heat buffering while the external armor geometry continues to perform its conventional coastal-protection function against waves, currents, and ice-related forcing. The baseline PTBU concept is intentionally passive and mechanically simple. It does not require continuous electrical power, pumps, refrigeration systems, or active thermal-control equipment. A first-order lumped thermal screening model is presented to examine whether seasonal freezing and partial warm-season ice retention are physically plausible under simplified polar boundary conditions. The preliminary results are encouraging but are not presented as engineering validation. More detailed transient heat-transfer, structural, hydrodynamic, environmental, and field testing would be required before practical deployment. The proposed novelty of PTBU does not lie in breakwater armor units, hollow concrete elements, freshwater freezing, or phase-change thermal storage individually. Rather, it lies in their specific integration within a mechanically interlocking coastal armor unit containing a sealed freshwater cavity intentionally subjected to seasonal freezing and thawing while retaining a simultaneous coastal-protection function. PTBU is presented as a falsifiable engineering concept rather than as a demonstrated climate intervention. Its initial objective is to determine whether such units can produce measurable local thermal and coastal-protection benefits in cold-region environments.