Mechanism

Substrate-mode storage operates by cycling working materials through phase or composition transitions across the structural mass of the host building. Each cycle deposits or extracts thermal energy at the substrate interface; the magnitude of this thermal output is a deterministic function of the cycle parameters and the substrate's thermophysical state. In the disclosed primitive, this thermal output is not vented to ambient nor managed by an isolated cooling loop; instead, the substrate carries engineered thermal-coupling channels whose geometry and working-fluid path admit direct thermal exchange between the substrate's structural mass and the building's HVAC infrastructure.

The thermal-coupling channels take three principal forms. In a cavity-bath substrate, the channels appear as cavity manifolds that route the working fluid through the cavity volume that already exists for storage-cycle reasons, sharing the manifold geometry with the storage cycle itself. In a passive substrate, the channels appear as embedded conduits cast into the structural mass at the time of substrate fabrication, with conduit spacing and cross-section selected for the desired thermal transfer rate. In a modular-block substrate, the channels appear as integral channels machined or molded into each block, with the assembled blocks aligning their channels into a continuous building-scale circuit.

Heat generated during storage cycling becomes useful thermal energy at the HVAC return loop. Conversely, when the building's HVAC system has excess thermal capacity (for example, when external conditions reduce the conditioning load below the system's minimum efficient operating point), the HVAC system pre-conditions the substrate to optimize storage operation in the next cycle. The thermal exchange is bidirectional and is mediated by the same coupling channels in either direction.

Control authority over the coupling is credentialed. The building's thermal-energy management software receives credentialed thermal-state observations from the substrate elements alongside conventional HVAC sensor readings (return-air temperature, supply-air temperature, ground-loop temperature, refrigerant pressures), and dispatches thermal flows across the composed system under unified policy. The credentialing primitive is the same one that governs the rest of the substrate-mode-storage architecture: the substrate participates in HVAC operations only on the authority of credentials issued under the building's governance procedure.

Operating Parameters

Channel geometry is parameterized by the desired thermal-transfer rate per unit substrate volume, by the working-fluid pressure rating of the structural assembly, and by the structural-load envelope within which the channels are admitted. Typical embodiments admit channel cross-sections in the range of 10–50 millimeters, channel spacings in the range of 100–500 millimeters, and working-fluid pressure ratings consistent with conventional hydronic HVAC piping. The channels are sized so that the pressure drop across the building-scale circuit is compatible with the circulation pump capacity of the heat-pump or geothermal interface.

Working fluids admitted by the architecture include conventional water-glycol hydronic fluids, refrigerants compatible with direct-expansion heat-pump interfaces, and dielectric heat-transfer fluids selected for the substrate's electrochemical environment. The choice of working fluid is parameterized by the substrate chemistry (some substrate chemistries are incompatible with water-bearing fluids and require dielectric circulation), by the temperature window over which the storage cycle operates, and by the regulatory regime governing the building's mechanical systems.

Thermal-state observations are reported at credentialed sample points distributed through the substrate. Sample density is parameterized by the substrate's thermal-conductivity uniformity (more uniform substrates require fewer sample points to characterize the bulk state) and by the control regime's responsiveness requirement. Sample readings carry credentialed signatures so that the building thermal-energy management software can verify the provenance of each reading and reject readings from sample points whose credential has been revoked.

Dispatch policy parameters include the prioritization of storage-cycle thermal output versus HVAC conditioning load, the threshold at which the HVAC system pre-conditions the substrate, and the coordination rules with utility-side demand-response signals when the building participates in a grid-services regime. Each dispatch decision is recorded in the building's lineage chain alongside the credentialed observations on which it was made, producing an auditable record of how thermal energy moved through the composed system.

Alternative Embodiments

In a first embodiment, the substrate is a cavity-bath structural element forming part of a building's slab-on-grade foundation, with cavity manifolds routing working fluid between the substrate and a ground-loop heat exchanger that doubles as the geothermal interface for the building's heat pump. In a second embodiment, the substrate is a passive thermal-mass wall within the building envelope, with embedded conduits that route working fluid between the wall and the building's hydronic distribution loop. In a third embodiment, the substrate is an array of modular blocks installed in a mechanical room, with integral channels that interface to the heat-pump refrigerant loop through a manifold plate.

In a fourth embodiment, the coupling channels carry a phase-change working fluid that exploits latent-heat transfer to maintain a tighter temperature window across the substrate-HVAC interface. In a fifth embodiment, the coupling channels are dual-circuit, with separate fluid paths for high-grade and low-grade thermal exchange, admitting the substrate to participate in both space conditioning and domestic hot-water service. In a sixth embodiment, the coupling is partially passive, with thermosiphon circulation that operates without pump authority during pump-out conditions and reverts to pumped circulation when active control resumes.

Further embodiments admit district-scale composition in which multiple buildings' substrate-mode storage assets share a common geothermal field through credentialed inter-building thermal exchange; multi-substrate composition in which a single building hosts substrates of different chemistries each coupled through their own channels but dispatched under unified policy; and retrofittable embodiments in which the coupling channels are installed on the surface of an existing structural element rather than integrated into the structural mass at fabrication.

A seventh embodiment integrates the coupling channels with a domestic-hot-water preheat loop, harvesting low-grade thermal output from storage cycling that would otherwise be insufficient for direct space conditioning but is well-matched to the lower temperature lift required for water preheating. An eighth embodiment couples the substrate to a chilled-beam or radiant-ceiling distribution loop, admitting summer-season storage waste heat to be rejected through the same hydronic distribution surfaces used for cooling delivery, after which the residual cooling capacity is re-introduced to the substrate during the next charging interval. A ninth embodiment admits a heat-recovery ventilation interface, coupling the substrate to the exhaust-air stream so that latent and sensible heat in the exhaust pre-conditions the substrate before mixing with outside air for makeup ventilation.

A tenth embodiment encloses the coupling channels within a vacuum-insulated jacket where local code or substrate chemistry require thermal isolation from occupied spaces, preserving the bidirectional exchange between substrate and HVAC infrastructure while preventing uncontrolled heat transfer into adjacent envelope cavities.

Composition

The embedded thermal-coupling primitive composes with the broader substrate-mode-storage architecture. The credentialed-observation primitive that admits substrate state to the storage controller also admits substrate state to the HVAC controller; the lineage-chain primitive that records storage operations also records HVAC dispatch decisions; the governance procedure that issues credentials for storage operation also issues credentials for HVAC participation. The composition is structural rather than incidental: the same governance instruments authorize the substrate's two roles.

Composition with grid-services participation is admitted through the dispatch policy. When the building participates in a demand-response regime, the dispatch policy admits utility-side signals as a credentialed input alongside the building's internal observations; the substrate is then dispatched to satisfy both the storage-cycle obligation and the grid-service obligation, with the trade-off resolved under the policy's declared prioritization rule.

Composition with on-site renewable generation is similarly admitted: when photovoltaic or wind generation is co-located, the dispatch policy treats surplus generation as a credentialed input that authorizes pre-conditioning cycles, expanding the effective storage envelope of the building without expanding the substrate volume. Composition with thermal-energy-as-a-service contracts is admitted through credential issuance to a third-party operator, who acquires bounded authority to dispatch the substrate's thermal exchange under metered terms while the building owner retains residual authority over storage-cycle obligations.

Distinction From Prior Art

Building codes and industry practice recognize embedded heating systems (radiant floor systems, thermally-active building systems or TABS) and recognize standard HVAC interfaces to heat pumps and geothermal loops. The disclosed thermal-coupling primitive composes with these recognized categories rather than introducing a novel regulatory class; deployment proceeds under existing building-code frameworks, with the storage-related thermal output reported as part of the energy-storage admissibility surface's operational profile rather than as a separate regulatory matter.

Conventional substrate-mode storage treats the cell-level heating produced during cycling as a thermal-management burden, expending parasitic energy to vent or actively cool the substrate so that the storage cycle remains within its efficient temperature window. Conventional radiant heating and TABS treat the building thermal mass as a passive distribution surface for HVAC heat that is generated elsewhere. Conventional heat-pump and geothermal HVAC treats the ground loop as the sole low-grade thermal reservoir and does not admit building structural mass as a co-equal participant in dispatch.

The disclosed primitive is distinct in that the storage substrate is engineered as a thermal participant in HVAC operations from the substrate-fabrication step forward, rather than retrofitted as an afterthought; the thermal coupling is bidirectional and credentialed, with HVAC and storage controllers operating against a shared lineage chain; and the cell-level heating that conventional substrate-mode storage treats as waste becomes a useful output by the same architectural choice that admits HVAC pre-conditioning of the substrate as a useful input.

Disclosure Scope

This article discloses the embedded thermal-coupling primitive of U.S. Provisional Application No. 64/050,895. The disclosure encompasses the channel-geometry options (cavity manifolds, embedded conduits, integral modular-block channels), the working-fluid options, the credentialed observation and dispatch primitives, the bidirectional thermal-exchange discipline, and the enumerated embodiments and composition properties. The disclosure is intended to support claims directed to the architectural primitive rather than to any particular substrate chemistry, working fluid, or HVAC topology, and to admit the full range of equivalents reachable by a person of ordinary skill applying the disclosed primitive to a building-integrated substrate-mode storage installation.