Pretty soon, heat pumps will be able to store and distribute heat as needed

Seasonal vs. Short‑Term Heat Storage

• Several commenters dream of “seasonal batteries” – e.g., a buried, bus‑sized tank storing summer heat for winter use.
• Others argue physics makes true seasonal storage at house scale impractical: even high–specific‑heat materials (water, salt hydrates) need huge volumes and very strong insulation to offset losses.
• A worked example: a buried, insulated 100 m³ water tank charged to ~85 °C could deliver ~4,000 kWh over winter – technically feasible but large, expensive, and construction‑heavy.
• Consensus: this tech is mainly suited to day‑night (or a few days) shifting, not storing summer heat for winter.

Phase Change Materials (PCM) vs. Water, Sand, and Stone

• The article’s system is recognized as essentially an enlarged version of PCM hand warmers; similar products already exist (e.g., Sunamp, ice‑storage systems, ceramic‑brick storage).
• PCMs store heat at nearly constant temperature, which aligns well with heat pump efficiency curves.
• However, cited figures (200 kJ/kg) are comparable to heating water from 10–60 °C; ceramics can be higher (450 kJ/kg).
• Critics highlight sealing, compatibility, and end‑of‑life/disposal risks versus simple water/sand/stone, which are cheap, robust, and well‑understood.

Heat Pumps, Solar, and Electrical Batteries

• Some argue that PV + sodium/LFP batteries + heat pump will outperform thermal storage on flexibility and total utility.
• Others counter that thermal stores are far cheaper upfront than electrical batteries and don’t need expensive inverters or major electrical work.
• Discussion of solar thermal vs PV: thermal is simple but limited by collector temperature; PV + heat pump can be more broadly useful but adds complexity.
• Hybrid PV‑thermal panels are mentioned as efficient but costly.

Heat Pump Water Heaters and Regulation

• A major subthread discusses US moves to effectively phase out resistive electric water heaters in favor of heat pump models.
• Supporters note 3–4× efficiency gains and existing tax credits/rebates; skeptics worry about high installed costs, required upgrades, maintenance, and edge cases (cold climates, lack of venting options).
• Broader debate over mandates vs markets, subsidy side‑effects (price inflation, boom‑bust installer cycles), and equity of tax‑credit–based incentives.

Use Cases Beyond Heating

• Some users in hot climates want analogous “cold storage” systems; examples given include district‑scale chilled water/ice storage and “cold district heating.”
• General sentiment: thermal storage paired with heat pumps is promising for daily load shifting and peak‑shaving, but not a silver bullet for long‑term or seasonal energy storage.